U.S. patent application number 12/081918 was filed with the patent office on 2008-10-16 for method for vapor phase catalytic oxidation.
Invention is credited to Masayasu Goriki, Hirochika Hosaka, Kimikatsu Jinno, Teruo Saito, Yoshiro Suzuki, Shuhei Yoda.
Application Number | 20080253943 12/081918 |
Document ID | / |
Family ID | 26625359 |
Filed Date | 2008-10-16 |
United States Patent
Application |
20080253943 |
Kind Code |
A1 |
Yoda; Shuhei ; et
al. |
October 16, 2008 |
Method for vapor phase catalytic oxidation
Abstract
An object of the present invention is to provide a method for
vapor phase catalytic oxidation which is almost free of variations
in reaction states in respective reaction tubes of the fixed bed
multi-tube heat-exchanger type reactor. Provided is a method for
vapor phase catalytic oxidation for obtaining a reaction product
gas by using a fixed bed multi-tube heat-exchanger type reactor
provided with a plurality of reaction tubes and by feeding a raw
material gas inside the reaction tubes packed with a catalyst,
wherein the method comprises: adjusting pressure losses of the
respective reaction tubes so that the pressure losses of the
respective reaction tubes after catalyst packing is within .+-.20%
of an average pressure loss of the reaction tubes by: packing an
inert substance at a raw material gas inlet portion of the reaction
tubes or removing and re-packing the catalyst packed, for a
reaction tube having a pressure loss lower than the average
pressure loss of the reaction tubes; and removing and re-packing
the catalyst packed, for a reaction tube having a pressure loss
higher than the average pressure loss of the reaction tubes.
Inventors: |
Yoda; Shuhei;
(Yokkaichi-shi, JP) ; Goriki; Masayasu;
(Yokkaichi-shi, JP) ; Hosaka; Hirochika;
(Yokkaichi-shi, JP) ; Jinno; Kimikatsu;
(Yokkaichi-shi, JP) ; Saito; Teruo;
(Yokkaichi-shi, JP) ; Suzuki; Yoshiro;
(Yokkaichi-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W., SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
26625359 |
Appl. No.: |
12/081918 |
Filed: |
April 23, 2008 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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10864492 |
Jun 10, 2004 |
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12081918 |
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PCT/JP02/13372 |
Dec 20, 2002 |
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10864492 |
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Current U.S.
Class: |
422/219 ; 141/1;
141/331; 414/804; 422/144 |
Current CPC
Class: |
C07C 45/33 20130101;
B01J 2208/00221 20130101; B01J 2523/00 20130101; C07C 51/252
20130101; C07C 51/252 20130101; B01J 2523/54 20130101; C07C 47/22
20130101; B01J 2523/12 20130101; B01J 2523/54 20130101; C07C 47/22
20130101; C07C 57/04 20130101; B01J 2523/12 20130101; B01J 2523/13
20130101; B01J 2523/41 20130101; B01J 2523/305 20130101; B01J
2523/845 20130101; B01J 2523/305 20130101; B01J 2523/845 20130101;
B01J 2523/41 20130101; C07C 45/33 20130101; B01J 2208/00513
20130101; B01J 2523/842 20130101; B01J 2523/842 20130101; B01J
2523/68 20130101; B01J 2523/68 20130101; B01J 2523/847 20130101;
B01J 23/31 20130101; B01J 2523/13 20130101; B01J 2208/00212
20130101; C07C 45/35 20130101; B01J 23/28 20130101; B01J 35/026
20130101; C07C 45/35 20130101; B01J 2208/00663 20130101; B01J
2523/00 20130101; B01J 8/067 20130101; B01J 2208/00752 20130101;
B01J 8/0085 20130101; B01J 23/002 20130101; B01J 23/8876 20130101;
B01J 2523/00 20130101; B01J 2208/00539 20130101; B01J 8/003
20130101 |
Class at
Publication: |
422/219 ;
414/804; 141/331; 141/1; 422/144 |
International
Class: |
B01J 4/00 20060101
B01J004/00; B01J 8/00 20060101 B01J008/00; B65G 69/04 20060101
B65G069/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 28, 2001 |
JP |
2001-399118 |
Jan 11, 2002 |
JP |
2002-4635 |
Claims
1-20. (canceled)
21. A method for packing a catalyst by allowing the catalyst to
fall into reaction tubes of a fixed bed multi-tube reactor using a
funnel, wherein at least a part of the funnel is a net.
22. The method for packing a catalyst according to claim 21,
wherein the catalyst is a molded catalyst or a supported
catalyst.
23. The method for packing a catalyst according to claim 21,
wherein the catalyst is a catalyst for producing acrylic acid or
methacrylic acid.
24. The method for packing a catalyst according to claim 21,
wherein a net mesh of the funnel is smaller than outer diameters of
the catalyst and an inert substance.
25. The method for packing a catalyst according to claim 21,
wherein the net of the funnel is provided at an inclined portion of
the funnel and an angle of the inclination is 10 to 75.degree..
26-30. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention relates to a method for vapor phase
catalytic oxidation involving using a fixed bed multi-tube
heat-exchanger type reactor provided with a plurality of reaction
tubes and feeding a raw material gas for reaction. The present
invention more specifically relates to a method for vapor phase
catalytic oxidation which is almost free of variations in reaction
states in respective reaction tubes of the fixed bed multi-tube
heat-exchanger type reactor.
[0002] In addition, the present invention relates to a method for
packing a catalyst in the reaction tubes used in the method for
vapor phase catalytic oxidation.
BACKGROUND ART
[0003] A fixed bed multi-tube heat-exchanger type reactor provided
with a plurality of reaction tubes (hereinafter, may be referred to
as "fixed bed multi-tube reactor") has been known up to now.
Further, a method of vapor phase catalytic oxidation using the
fixed bed multi-tube heat-exchanger type reactor has been
known.
[0004] A method of packing a catalyst in the fixed bed multi-tube
heat-exchanger type reactor generally involves packing by charging
the catalyst from an upper portion of the reactor and allowing the
catalyst to fall. However, according to this method, packed states
differ for the respective reaction tubes because of reasons
including: (1) the catalyst is powdered or degraded by physical
impact of the catalyst charged to fall; and (2) packing time
varies. To be specific, a level of powdering or degradation of the
catalyst during catalyst packing differs for the respective
reaction tubes. Further, long packing time results in a large
packing density, and short packing time results in a small packing
density. Therefore, according to a conventional packing method, the
catalyst was hardly packed to provide uniform pressure states of
the respective reaction tubes, particularly a pressure loss, which
becomes an important factor in an oxidation reaction.
[0005] No technique exists aiming to provide a uniform pressure
loss for the respective reaction tubes of the fixed bed multi-tube
reactor, and methods for solving the problem (1) or (2) are
proposed.
[0006] Examples of a method of suppressing powdering or degradation
of the catalyst during catalyst packing include the following.
[0007] JP 2852712 B discloses a method of improving mechanical
strength of a catalyst by coating the catalyst with an organic
polymer compound having depolymerizing property on a surface of the
catalyst. However, a uniform coating of all of the catalyst is
difficult, and catalyst strength varies even if the catalyst
strength increases as a whole. The coating has some effects in
reducing the pressure loss, but this method is far from a
satisfying method of providing a uniform pressure loss for the
respective reaction tubes.
[0008] Further, JP 05-031351 A discloses a method of interposing a
cord-like substance, having a shape and a thickness substantially
not obstructing falling of a catalyst, inside a reactor when
packing the catalyst from an upper portion of the reactor by
allowing to fall. A slight effect is provided for preventing
powdering or degradation of the catalyst, but an effect of catalyst
packing time on packing density is unavoidable. Thus, this method
is far from a satisfying method for providing a uniform pressure
loss in the respective reaction tubes.
[0009] Further, JP 10-277381 A discloses a method involving packing
dry ice prior to packing a catalyst by allowing to fall, packing
the catalyst, and subsequently vaporizing and removing the dry
ice.
[0010] Further, JP 09-141084 A discloses a method of packing a
catalyst from an upper portion of a reactor involves packing a
liquid substance inside the reactor, subsequently packing the
catalyst, and then removing the liquid substance. However, these
methods of packing the dry ice or the liquid substance in advance
are far from satisfying methods industrially because post-treatment
after catalyst packing involves time and effort, and handled
substances may deteriorate a working environment.
[0011] On the other hand, examples of methods of controlling
packing operation (time) include the following.
[0012] JP 11-333282 A discloses a method using an automatic packing
machine provided with a catalyst feed conveyor and capable of
controlling catalyst packing time. The patent discloses that the
packing machine provides uniform packing time, allowing a uniform
pressure loss in the respective reaction tubes. However, a
difference in pressure loss may result depending on the catalyst,
and thus, the method is far from satisfying.
[0013] Next, a fixed bed multi-tube heat-exchanger type reactor,
using a heating medium for absorbing heat of reaction generated
inside reaction tubes is conventionally provided with a plate for
changing passage of the heating medium, called a baffle, to allow
uniform flow of the heating medium inside the reactor as much as
possible.
[0014] Such a fixed bed multi-tube heat-exchanger type reactor
provided with a baffle did not have particular problems when a size
of a plant was small. However, following problems arise when a size
of the plant, that is, a reactor becomes large for increasing
productivity as of today.
[0015] In other words, a non-uniform portion of a flow of the
heating medium forms inside a reactor shell. A state of poor heat
removal forms in part of reaction tubes among a plurality of
reaction tubes inside the reactor. A localized abnormal
high-temperature zone (hot spot) may form in the reaction tubes
which are in a state of poor heat removal, possibly resulting in a
reaction out of control.
[0016] Further, such different reaction states among the reaction
tubes result in a problem of not preventing formation of reaction
tubes in which a reaction becomes out of control. In addition, the
different states result in problems of decreasing an yield of a
target product gas and of decreasing a catalyst life.
[0017] On the other hand, an increase of raw material gas feed for
enhancing the productivity results in portions where heat removal
is slower than heat generation during a reaction, even with a
conventional reactor of a small size. Thus, problems arise such as
the above hot spots.
[0018] In other words, a conventional method for vapor phase
catalytic oxidation using the fixed bed multi-tube heat-exchanger
type reactor was not a method for vapor phase catalytic oxidation
exhibiting satisfactory results such as effectively preventing
forming of hot spots, yielding a large amount of a reaction product
gas, and having a long catalyst life.
[0019] Further, the method of packing the catalyst in the reaction
tubes of the fixed bed multi-tube heat-exchanger type reactor as
described above generally involves using a packing funnel. The
catalyst is packed by providing the reaction tubes with the packing
funnel, and packing the catalyst by charging the catalyst and
allowing the catalyst to fall through the packing funnel.
[0020] However, the powdered or degraded catalyst formed during
transfer, transport, and handling of the catalyst is packed in the
reaction tubes as well according to this method. Variations of
pressure loss becomes large, which is a particularly important
factor in an oxidation reaction during a production step of acrylic
acid or methacrylic acid (hereinafter, may be referred to as
"(meth)acrylic acid"), and thus, this method is far from a
satisfying packing method for providing a uniform reaction.
[0021] Up to now, no technique is available for separating and
removing the powdered or degraded catalyst in the packed catalyst
during catalyst packing. The method as described above is merely
proposed for suppressing powdering or degradation of the catalyst
during catalyst packing.
[0022] However, those methods had problems in that powdering or
degradation of the catalyst caused by vibration or impact taking
place during transfer, transport, and handling of the catalyst from
catalyst production to catalyst packing or the like in the reaction
tubes of the fixed bed multi-tube reactor were hardly evaded. In
addition, the catalyst was packed in the reaction tubes of the
fixed bed multi-tube reactor together with the powdered or degraded
catalyst or the like.
[0023] Further, when packing a catalyst in the reaction tubes of
the fixed bed multi-tube heat-exchanger type reactor, the method as
described above is employed to pack the catalyst by allowing the
catalyst to fall from an upper portion of the reactor.
[0024] However, the catalyst may be powdered or degraded from
physical impact during falling of the catalyst according to this
method. For preventing the above, the catalyst itself must have
mechanical strength above some level or the packing method must be
somehow devised.
[0025] The mechanical strength of the catalyst can be improved to a
certain degree by adjusting a molding pressure of the catalyst or
devising operations of molding or support. However, the catalyst
having enhanced mechanical strength through those techniques
resulted in reducing specific surface areas of the catalyst,
reducing active sites effective for a reaction, and not allowing
control of pore distribution effective for reaction. Thus, problems
arouse such that an yield of the target product was reduced and the
catalyst was not practical.
[0026] Further, examples of the method of suppressing powdering or
degradation of the catalyst during catalyst packing include the
above methods disclosed in JP 2852712 B, JP 05-031351 A, JP
10-277381 A, and JP 09-141084.
[0027] However, a uniform coating of all of the catalyst is
difficult for the method of enhancing the mechanical strength of
the catalyst by coating the catalyst, and catalyst strength varies
even if the catalyst strength increases as a whole. The coating has
some effects in reducing powdering or degradation of the catalyst,
but this method requires a step of coating during catalyst
production and is far from a satisfying method.
[0028] The method of interposing a cord-like substance provides an
effect of preventing powdering or degradation of the catalyst.
However, the method requires an operation of pulling the cord-like
substance upward while packing the catalyst. Effects such as
extending the packing operation time or the like are unavoidable,
and thus, this method is far from satisfying.
[0029] The method of packing the dry ice or the liquid substance
before catalyst packing may result in post treatment taking time
and effort after catalyst packing and deterioration of the working
environment depending on the handled substances, and thus, is far
from satisfying industrially.
DISCLOSURE OF THE INVENTION
[0030] A first invention of the present invention has been made in
view of the above problems, and an object of the first invention is
to provide a method for vapor phase catalytic oxidation in which a
vapor phase catalytic oxidation reaction through packing a catalyst
in reaction tubes of a fixed bed multi-tube heat-exchanger type
reactor proceeds in the respective reaction tubes having a uniform
pressure loss at an optimum temperature in all reaction tubes.
[0031] The inventors of the present invention have confirmed during
a periodic repair operation, for example, that some reaction tubes
result in coking in a plant producing acrolein, acrylic acid, or
the like through vapor phase catalytic oxidation of propylene using
the fixed bed multi-tube heat-exchanger type reactor. Moreover, the
reaction tubes resulting in coking are scattered, and the coking
occurs without a pattern in places where cannot be explained by a
reaction gas flow or a heating medium flow inside the reactor.
[0032] The inventors of the present invention have studied
intensively based on the fact, and found out that (1) a difference
in pressure losses of the respective reaction tubes in the fixed
bed multi-tube heat-exchanger type reactor significantly affects
conditions of a reaction and (2) pressure loss of the reaction
tubes after catalyst packing affects the conditions of a reaction
thereafter, to thereby complete the first invention of the present
invention.
[0033] Further, a second invention of the present invention has
been made in view of the above problems, and an object of the
second invention is to provide a method for vapor phase catalytic
oxidation achieving satisfactory results such as effectively
preventing hot spot formation, yielding a large amount of a
reaction product gas, and extending a catalyst life. Those
satisfactory results may be obtained by using a fixed bed
multi-tube heat-exchanger type reactor provided with a plurality of
reaction tubes, circulating a heating medium outside the reaction
tubes, and feeding a raw material gas inside the reactor packed
with a catalyst.
[0034] Examples of methods for preventing the formation of the hot
spots include: improvements regarding equipment of the reactor such
as a reduction of a reaction tube diameter, use of a heating medium
having a large heat capacity, and an increase in amount of the
circulating heating medium for reducing temperature of a catalyst
layer inside the reaction tubes; and improvements regarding
reaction conditions such as change in concentration of the raw
material gas.
[0035] However, similarly and uniformly subjecting all reaction
tubes in the reactor with those methods results in high cost and is
not preferable also in terms of improving productivity. Further,
reaction states of the respective reaction tubes inside the reactor
will not be uniform according to those methods.
[0036] The inventors of the present invention have studied
intensively and have confirmed that uniform reaction states of the
reactions tubes inside the reactor is effective for allowing
effective prevention of hot spot formation, increasing yield of a
reaction product gas, and extending a catalyst life. Therefore, the
inventors of the present invention have found out that the method
described below provides a method for vapor phase catalytic
oxidation achieving the above objects, to thereby complete the
second invention of the present invention.
[0037] Further, a third invention of the present invention has been
made in view of the above problems, and an object of the third
invention is to provide a method of packing a catalyst or the like
in reaction tubes of a fixed bed multi-tube reactor while
separating and removing powdered or degraded catalyst during
catalyst packing when packing a catalyst or the like in the
reaction tubes of the fixed bed multi-tube reactor.
[0038] The inventors of the present invention have found out that
when packing a catalyst or the like in the reaction tubes of the
fixed bed multi-tube reactor, separation and removal of powdered or
degraded catalyst or the like during packing catalyst is important
in addition to suppression of powdering or degradation of the
catalyst or the like during packing, to thereby complete the third
invention of the present invention.
[0039] Further, a fourth invention of the present invention has
been made in view of the above problems, and an object of the
fourth invention is to provide a method of packing a catalyst in
reaction tubes of a fixed bed multi-tube reactor through minimizing
powdering or degradation of a catalyst having not so high
mechanical strength without affecting catalyst packing operation
time, when packing a catalyst in the reaction tubes of the fixed
bed multi-tube reactor.
[0040] The inventors of the present invention have conducted
various studies and have found out that when packing a molded
catalyst or a supported catalyst by allowing the catalyst to fall
from an upper portion of the reaction tubes of the fixed bed
multi-tube reactor, interposing a chain substance in the reaction
tubes to reduce a falling rate of the catalyst allows suppressing
of blocking without affecting the catalyst packing operation time,
and minimizing of powdering or degradation, to thereby complete the
fourth invention of the present invention.
[0041] In other words, the first invention of the present invention
is described below. [0042] (1) A method for vapor phase catalytic
oxidation for obtaining a reaction product gas by using a fixed bed
multi-tube heat-exchanger type reactor provided with a plurality of
reaction tubes and by feeding a raw material gas inside the
reaction tubes packed with a catalyst, wherein the method
comprises:
[0043] adjusting pressure losses of the respective reaction tubes
so that the pressure losses of the respective reaction tubes after
catalyst packing is within .+-.20% of an average pressure loss of
the reaction tubes by: packing an inert substance at a raw material
gas inlet portion of the reaction tubes or removing and re-packing
the catalyst packed, for a reaction tube having a pressure loss
lower than the average pressure loss of the reaction tubes; and
removing and re-packing the catalyst packed, for a reaction tube
having a pressure loss higher than the average pressure loss of the
reaction tubes. [0044] (2) The method for vapor phase catalytic
oxidation according to the above item (1), wherein the inert
substance for adjusting pressure loss is at least one type of a
substance selected from the group consisting of alumina, silicon
carbide, silica, zirconium oxide, and titanium oxide. [0045] (3)
The method for vapor phase catalytic oxidation according to the
above item (1) or (2), wherein a shape of the inert substance for
adjusting the pressure loss is spherical, cylindrical, ring-shaped,
or amorphous. [0046] (4) The method for vapor phase catalytic
oxidation according to any one of the above items (1) to (3),
wherein the catalyst is an Mo--Bi mixed oxide catalyst or an Mo--V
mixed oxide catalyst. [0047] (5) The method for vapor phase
catalytic oxidation according to any one of the above items (1) to
(4), wherein a shape of the catalyst is spherical, cylindrical,
ring-shaped, or amorphous. [0048] (6) The method for vapor phase
catalytic oxidation according to any one of the above items (1) to
(5), wherein the catalyst is a single catalyst or a catalyst
diluted with the inert substance. [0049] (7) The method for vapor
phase catalytic oxidation according to any one of the above items
(1) to (6), wherein the method further comprises:
[0050] predicting reaction states inside the reaction tubes through
measurement of catalyst layer temperature of the reaction tubes or
through a simulation analysis of a fluid state of a heating medium
circulating outside the reaction tubes with heat of reaction inside
the reaction tubes using a computer; and
[0051] determining catalyst packing specifications of the reaction
tubes according to the prediction results so that nonuniformity of
the reaction states among the reaction tubes are reduced for
packing the catalyst in the reaction tubes. [0052] (8) The method
for vapor phase catalytic oxidation according to the above item
(7), wherein items determining the catalyst packing specifications
include items of a catalyst type, a catalyst amount, a catalyst
form, a dilution method for the catalyst, and lengths of reaction
zones. [0053] (9) The method for vapor phase catalytic oxidation
according to any one of the above items (1) to (8), wherein the
method further comprises:
[0054] packing the catalyst by allowing the catalyst to fall using
a funnel with a net in at least a part of the funnel, for packing
the catalyst in the reaction tubes. [0055] (10) The method for
vapor phase catalytic oxidation according to any one of the above
items (1) to (8), wherein the method further comprises:
[0056] interposing a chain substance inside the reaction tubes so
that a lower end of the chain substance is positioned above an
upper end of a catalyst layer; and
[0057] packing the catalyst by allowing the catalyst to fall, for
packing the catalyst in the reaction tubes. [0058] (11) A
production method for (meth)acrolein or (meth)acrylic acid wherein
the method comprises:
[0059] using the method for vapor phase catalytic oxidation
according to any one of the above items (1) to (10); and
[0060] oxidizing propane, propylene, and isobutylene using
molecular oxygen to produce (meth)acrolein or (meth)acrylic
acid.
[0061] In other words, the second invention of the present
invention is described below. [0062] (12) A method for vapor phase
catalytic oxidation for obtaining a reaction product gas by using a
fixed bed multi-tube heat-exchanger type reactor provided with a
plurality of reaction tubes, circulating a heating medium outside
the reaction tubes, and feeding a raw material gas inside the
reaction tubes packed with a catalyst, wherein the method
comprises:
[0063] predicting reaction states inside the reaction tubes;
and
[0064] changing catalyst packing specifications of the reaction
tubes according to the prediction results so that nonuniformity of
the reaction states among the reaction tubes are reduced. [0065]
(13) The method for vapor phase catalytic oxidation according to
the above item (12), wherein the heating medium is for absorbing
heat of reaction generated from the reaction tubes. [0066] (14) The
method for vapor phase catalytic oxidation according to the above
item (12) or (13), wherein the reaction states inside the reaction
tubes are predicted by grasping thermal states inside the reaction
tubes. [0067] (15) The method for vapor phase catalytic oxidation
according to any one of the above items (12) to (14), wherein the
thermal states inside the reaction tubes are grasped by measuring
catalyst layer temperatures of the reaction tubes. [0068] (16) The
method for vapor phase catalytic oxidation according to any one of
the above items (12) to (14), wherein the thermal states inside the
reaction tubes are grasped through a simulation analysis using a
computer. [0069] (17) The method for vapor phase catalytic
oxidation according to the above item (16), wherein a fluid
analysis of a heating medium is conducted through the simulation
analysis using a computer. [0070] (18) The method for vapor phase
catalytic oxidation according to the above item (17), wherein the
fluid analysis of the heating medium and an analysis of heat of
reaction inside the reaction tubes are conducted through the
simulation analysis using a computer. [0071] (19) The method for
vapor phase catalytic oxidation according to any one of the above
items (12) to (18), wherein items determining the catalyst packing
specifications include items of a catalyst type, a catalyst amount,
a catalyst shape, a dilution method for the catalyst, and lengths
of reaction zones. [0072] (20) The method for vapor phase catalytic
oxidation according to any one of the above items (12) to (19),
wherein the method further comprises:
[0073] stopping feed of the raw material gas to the reaction tubes
for a part of the reaction tubes among the plurality of reaction
tubes in the fixed bed multi-tube heat-exchanger type reactor.
[0074] In other words, the third invention of the present invention
is described below. [0075] (21) A method for packing a catalyst by
allowing the catalyst to fall into reaction tubes of a fixed bed
multi-tube reactor using a funnel, wherein at least a part of the
funnel is a net. [0076] (22) The method for packing a catalyst
according to the above item (21), wherein the catalyst is a molded
catalyst or a supported catalyst. [0077] (23) The method for
packing a catalyst according to the above item (21) or (22),
wherein the catalyst is a catalyst for producing acrylic acid or
methacrylic acid. [0078] (24) The method for packing a catalyst
according to any one of the above items (21) to (23), wherein a net
mesh of the funnel is smaller than outer diameters of the catalyst
and an inert substance. [0079] (25) The method for packing a
catalyst according to any one of the above items (21) to (24),
wherein the net of the funnel is provided at an inclined portion of
the funnel and an angle of the inclination is 10 to 750.
[0080] In other words, the fourth invention of the present
invention is described below. [0081] (26) The method for packing a
catalyst by allowing the catalyst to fall into reaction tubes of a
fixed bed multi-tube reactor, wherein the method comprises: [0082]
interposing a chain substance inside the reaction tubes so that an
lower end of the chain substance is positioned above an upper end
of a catalyst layer; and packing the catalyst in the reaction tubes
of the fixed bed multi-tube reactor. [0083] (27) The method for
packing a catalyst according to the above item (26), wherein the
catalyst is a molded catalyst or a supported catalyst. [0084] (28)
The method for packing a catalyst according to the above item (26)
or (27), wherein the lower end of the chain substance is positioned
1 to 100 cm above the upper end of the catalyst layer packed in the
reaction tubes. [0085] (29) The method for packing a catalyst
according to any one of the above items (26) to (28), wherein the
catalyst is a catalyst for producing acrylic acid or methacrylic
acid. [0086] (30) The method for packing a catalyst according to
any one of the above items (26) to (29), wherein a size of the
reaction tubes of the fixed bed multi-tube reactor is 2 to 10 m in
length and 50 mm or less in diameter.
[0087] Hereinafter, the first invention of the present invention
will be described in detail.
[0088] The first invention involves a method for vapor phase
catalytic oxidation using a fixed bed multi-tube heat-exchanger
type reactor provided with a plurality of reaction tubes.
[0089] In other words, a reaction product gas is produced in the
reactor by circulating a heating medium outside the reaction tubes
and feeding a raw material gas inside the reaction tubes packed
with a catalyst.
[0090] According to the first invention, the heating medium is
preferably used for absorbing heat of reaction generated from the
reaction tubes. Any material can be used for the heating medium as
long as the material has a function of absorbing the heat of
reaction generated from the reaction tubes. Examples of the heating
medium include: organic heating media such as
partially-hydrogenated triphenyl; and inorganic molten salts such
as alkali metal (sodium, potassium, or the like) nitrate or
nitrite, so-called niter.
[0091] Further, according to a method for vapor phase catalytic
oxidation of the first invention, the raw material gas or the
catalyst can be appropriately selected in accordance with a desired
type of the reaction product gas.
[0092] A vapor phase catalytic oxidation reaction of the first
invention is a method widely used for producing (meth)acrolein or
(meth)acrylic acid from propane, propylene, or isobutylene in the
presence of a mixed oxide catalyst using molecular oxygen or a
molecular oxygen-containing gas.
[0093] The method generally involves: producing acrylic acid
through vapor phase oxidation of propane using an Mo--V--Te mixed
oxide catalyst, an Mo--V--Sb mixed oxide catalyst, or the like; or
producing (meth)acrylic acid by oxidizing propylene or isobutylene
in the presence of an Mo--Bi mixed oxide catalyst to mainly produce
(meth)acrolein in a former reaction and by oxidizing the
(meth)acrolein produced in the former reaction in the presence of
an Mo--V mixed oxide catalyst.
[0094] Examples of typical systems of commercialized methods for
vapor phase catalytic oxidation include a one-pass system, an
unreacted propylene recycle system, and a flue gas recycle system.
Hereinafter, the systems will be descried using propylene as an
example.
[0095] The one-pass system involves: mixing and feeding propylene,
air, and steam from a raw material gas inlet of the respective
reaction tubes of a fixed bed multi-tube reactor for a former
reaction; converting the raw material gas to mainly acrolein and
acrylic acid; feeding an outlet gas into the reaction tubes of a
fixed bed multi-tube reactor for a latter reaction without
separating products from the outlet gas; and oxidizing the acrolein
to acrylic acid. At this time, a general method also involves
feeding air and steam required for a reaction in the latter
reaction to the latter reaction in addition to the former reaction
outlet gas.
[0096] The unreacted propylene recycle system for recycling a part
of the unreacted propylene involves: guiding the reaction product
gas containing acrylic acid obtained from an outlet of the latter
reactor to an acrylic acid collecting device; collecting the
acrylic acid in an aqueous solution; and feeding a part of waste
gas containing the unreacted propylene from the collecting device
to the raw material gas inlet of the former reaction.
[0097] The flue gas recycle system involves: guiding the reaction
product gas containing acrylic acid obtained from the outlet of the
latter reactor to the acrylic acid collecting device; collecting
the acrylic acid in an aqueous solution; catalytically combusting
and oxidizing all waste gas from the collecting device; converting
the unreacted propylene or the like in the waste gas to mainly
carbon dioxide and water; and adding a part of the obtained flue
gas to the raw material gas inlet of the former reaction.
[0098] The catalyst used in the method for vapor phase catalytic
oxidation of the first invention is preferably used for packing of
the catalyst for acrylic acid formation to the reaction tubes of
the fixed multi-tubular reactor used for forming (meth)acrolein or
(meth)acrylic acid. Specific examples of the catalyst include the
following.
[0099] Examples of the catalyst used for a vapor phase catalytic
oxidation reaction for forming (meth)acrylic acid or (meth)acrolein
include a catalyst used in the former reaction for converting an
olefin into unsaturated aldehyde or unsaturated acid and a catalyst
used in the latter reaction for converting the unsaturated aldehyde
into the unsaturated acid. Those catalysts can be employed to
either reaction according to the first invention.
[0100] The following formula (I) represents an example of the
catalyst used for the former reaction.
Mo.sub.aW.sub.bBi.sub.cFe.sub.dA.sub.eB.sub.fC.sub.gD.sub.hE.sub.iO.sub.-
x (I)
(wherein, Mo represents molybdenum; W represents tungsten; Bi
represents bismuth; Fe represents iron; A represents at least one
type of element chosen from nickel and cobalt; B represents at
least one type of element selected from the group consisting of
sodium, potassium, rubidium, cesium, and thallium; C represents at
least one type of element selected from alkali earth metals; D
represents at least one type of element selected from the group
consisting of phosphorus, tellurium, antimony, tin, cerium, lead,
niobium, manganese, arsenic, boron, and zinc; E represents at least
one type of element selected from the group consisting of silicon,
aluminum, titanium, and zirconium; O represents oxygen; a, b, c, d,
e, f, g, h, i, and x represent atomic ratios of Mo, W, Bi, Fe, A,
B, C, D, E, and O respectively; and if a=12, 0.ltoreq.b.ltoreq.10,
0.ltoreq.c.ltoreq.10 (preferably 0.1.ltoreq.c.ltoreq.10),
0.ltoreq.d.ltoreq.10 (preferably 0.1.ltoreq.d.ltoreq.10),
2.ltoreq.e.ltoreq.15, 0.ltoreq.f.ltoreq.10 (preferably
0.001.ltoreq.f.ltoreq.10), 0.ltoreq.g.ltoreq.10,
0.ltoreq.h.ltoreq.4, and 0.ltoreq.i.ltoreq.30; and x is a value
determined from oxidation states of the respective elements.)
[0101] The following formula (II) represents an example of the
catalyst used for the latter reaction of the first invention.
Mo.sub.aV.sub.bW.sub.cCu.sub.dX.sub.eY.sub.fO.sub.g (II)
(wherein, Mo represents molybdenum; V represents vanadium; W
represents tungsten; Cu represents copper; X represents at least
one type of element selected from the group consisting of Mg, Ca,
Sr, and Ba; Y represents at least one type of element selected from
the group consisting of Ti, Zr, Ce, Cr, Mn, Fe, Co, Ni, Zn, Nb, Sn,
Sb, Pb, and Bi; 0 represents oxygen; a, b, c, d, e, f, and g
represent atomic ratios of Mo, V, W, Cu, X, Y, and O; if a=12,
2.ltoreq.b.ltoreq.14, 0.ltoreq.c.ltoreq.12, 0.ltoreq.d.ltoreq.6,
0.ltoreq.e.ltoreq.3, and 0.ltoreq.f.ltoreq.3; and g is a value
determined from oxidation states of the respective elements.)
[0102] The above catalysts can be prepared, for example, through a
method disclosed in JP 63-054942 A.
[0103] The reaction tubes used in the method for vapor phase
catalytic oxidation of the first invention are packed with the
catalyst and, as appropriately, an inert substance for dilution of
the catalyst (hereinafter, may be referred to as "diluent").
According to the first invention, the catalyst used may be a single
catalyst or a catalyst diluted with the inert substance.
[0104] Further, packing specifications of the catalyst in the
reaction tubes may be determined comprehensively in view of
respective factors such as a catalyst type, a catalyst amount, a
catalyst form (shape, size), a dilution method for the catalyst
(diluent type, diluent amount), and lengths of reaction zones.
[0105] The form (shape, size) of the catalyst used in the method
for vapor phase catalytic oxidation of the first invention is not
particularly limited, and a molding method for the catalyst is also
not particularly limited. A molded catalyst molded through an
extrusion molding method or a tablet compression method can be
used, for example. In addition, a supported catalyst structured as
a mixed oxide composed of a catalytic component supported on an
inert support such as silicon carbide, alumina, zirconium oxide,
and titanium oxide may be used.
[0106] Further, the shape of the catalyst may be any shape such as
spherical, columnar, cylindrical, ring-shaped, star-shaped, and
amorphous. Use of a ring catalyst, in particular, is effective for
preventing thermal storage in hot spot portions.
[0107] Further, any type of the diluent may used as long as it is
stable under conditions of a (meth)acrolein and (meth)acrylate
oxidation reaction and is not reactive with raw materials such as
olefins and products such as unsaturated aldehydes and unsaturated
fatty acids. Specific examples of the diluent include compounds
used for catalyst supports such as alumina, silicon carbide,
silica, zirconium oxide, and titanium oxide. Further, a form of the
diluent, similar to the catalyst, is not limited and may be any
shape such as spherical, columnar, ring-shaped, a small piece, a
net, and amorphous. The inert substance is used for adjusting
activity of the whole catalyst in a packed layer to prevent
abnormal heat generation during an exothermic reaction.
[0108] The amount of the inert substance is suitably determined
depending on an expected catalyst activity. Further, the packing
specifications of the catalyst may differ by layers of reaction
zones of one reaction tube. For example, packing specifications of
the catalyst packed in an upper portion of a reaction tube may
differ from the packing specifications of the catalyst packed in a
lower portion of the reaction tube. Generally, the number of the
reaction zones are preferably set to 2 to 3 within one reaction
tube.
[0109] Further, a preferable method involves, for example: dividing
the packed layer of the reaction tubes; lowering the catalyst
activity and increasing the amount of the inert substance used to
suppress the heat generation near the raw material gas inlet; and
enhancing the catalyst activity and reducing the amount of the
inert substance used to accelerate the reaction near the raw
material gas outlet.
[0110] According to the first invention, the fixed bed multi-tube
heat-exchanger type reactor is generally used industrially and is
not particularly limited.
[0111] Next, the pressure loss of the reaction tubes in the method
for vapor phase catalytic oxidation of the first invention will be
described.
[0112] The first invention relates to the method for vapor phase
catalytic oxidation for producing (meth)acrolein, (meth)acrylic
acid, and the like, in which the pressure losses of the respective
reaction tubes after packing the catalyst in the fixed bed
multi-tube heat-exchanger type reactor for a vapor phase oxidation
reaction is made uniform. The first invention more specifically
relates to the method for vapor phase catalytic oxidation,
characterized in that the pressure losses of the respective
reaction tubes after catalyst packing is adjusted within .+-.20% of
an average pressure loss of the reaction tubes by: packing an inert
substance at the raw material gas inlet portion of the reaction
tubes or removing and re-packing the catalyst packed, for a
reaction tube having a pressure loss lower than the average
pressure loss of the reaction tubes; and removing and re-packing
the catalyst packed, for a reaction tube having a pressure loss
higher than the average pressure loss of the reaction tubes.
[0113] Here, the average pressure loss of the reaction tubes is an
average value of the pressure loss of 0.5% or more, preferably 1%
or more of the reaction tubes randomly selected from the total
reaction tubes.
[0114] The fixed bed multi-tube reactor used for vapor phase
catalytic oxidation of propane, propylene, or the like is provided
with several thousands to several ten thousands of the reaction
tubes, and it is very difficult to uniform packed states of the
catalyst in all of the reaction tubes. In other words, catalyst
powdering or degradation is hardly made uniform in the respective
reaction tubes during catalyst packing. Further, catalyst packing
time of the respective reaction tubes is hardly made equal. The
packed state of the catalyst, that is the pressure loss, which
becomes a particularly important factor in the oxidation reaction,
differs greatly by the reaction tubes.
[0115] To be specific, a problem caused by the difference in the
pressure loss involves: changing the amount of gas flowing to the
reaction tubes; changing reaction situations by the reaction tubes;
and resulting in different reaction situations by the reaction
tubes even within the same reactor.
[0116] The reaction temperature of the reactor is determined
according to an average value of the reaction states of the total
reaction tubes. In the former reactor for an oxidation reaction of
propylene, for example, propylene conversions vary by the reaction
tubes. Therefore, the temperature of the heating medium is
determined according to the average propylene conversion of the
total reaction tubes. Thus, not all reaction tubes are operated
under optimum conditions.
[0117] In other words, providing a uniform reaction state of the
respective reaction tubes inside the reactor for oxidation
reaction, that is the pressure loss, is important for a safe
operation of the reactor for oxidation reaction from reasons
described below. [0118] (1) The conversion of the raw material
substance reduces and the yield decreases in a reaction tube with a
large amount of gas at the same reaction temperature. In contrast,
an excessive reaction occurs and side reactions increase to reduce
selectivity, in a reaction tube with a small amount of gas at the
same reaction temperature. [0119] (2) Further, excessive side
reactions occur in a reaction tube with a small amount of gas. A
reduction of the selectivity combined with an oxygen shortage in an
outlet portion of the reaction tube causes not only catalyst
deterioration, but also coking. [0120] (3) The reaction situations
of the respective reaction tubes differ, so that conditions of the
catalyst deterioration differ, thereby reducing the catalyst life
as a whole.
[0121] According to the first invention, a method of packing the
catalyst to the reaction tubes of the fixed bed multi-tube
heat-exchanger type reactor is not particularly limited. However,
the catalyst is preferably packed while leaving an empty portion in
the upper portion of the reaction tubes.
[0122] 0.5% or more, preferably 1% or more of the reaction tubes
are randomly selected from the total reaction tubes after catalyst
packing, and the pressure loss is measured. The pressure loss can
be measured by passing a gas of a constant flow rate through the
reaction tubes using a mass flow meter and measuring the pressure
at that time. The gas passed through the reaction tubes at the time
is not particularly limited, but air is desirably used for safety
reasons. The amount of the gas passed through the reaction tubes is
desirably the amount of the gas actually passed through during a
reaction at a steady state.
[0123] After measuring the pressure losses of the total reaction
tubes, the average value of the pressure losses of the measured
reaction tubes is calculated. A reaction tube having a pressure
loss lower than the average value is packed with an inert substance
in an empty portion of the reaction tube or has the catalyst
removed and re-packed, to adjust the pressure loss within .+-.20%,
preferably +10% of the average value.
[0124] A reaction tube having a pressure loss higher than the
average value by 20% or less has the catalyst removed and
re-packed.
[0125] If a pressure loss is higher than the average pressure loss
of the measured reaction tubes by 20% or more, the amount of the
raw material gas flowing through the reaction tubes reduces,
thereby causing an excessive reaction. Further, if a pressure loss
is lower by 20% or more, the amount of the raw material gas flowing
through the reaction tubes increases, thereby degrading the
reactivity.
[0126] The respective reaction tubes are generally provided with
catalyst holders in lower portions, and the catalyst is packed from
upper portions of the reaction tubes. The catalyst of the reaction
tubes may be removed by detaching the catalyst holders at the lower
portions of the reaction tubes and allowing the catalyst to fall.
For a mode in which a plurality of the reaction tubes shares the
catalyst holder, the catalyst may be removed from the upper
portions using a vacuum pump.
[0127] Moreover, according to the first invention, the inert
substance added after measuring the pressure loss for particularly
adjusting the pressure loss or the inert substance diluting the
catalyst re-packed among the inert substance packed to the above
reaction tubes is referred to as an inert substance for adjustment.
The inert substance for adjustment is preferably selected from the
group consisting of alumina, silicon carbide, silica, zirconium
oxide, and titanium oxide as described above. Further, the form of
the inert substance for adjustment is not particularly limited, and
may be any shape such as spherical, columnar, ring-shaped, and
amorphous.
[0128] Further, according to the first invention, the packing
specifications of the catalyst may be set considering prediction
results of the reaction states inside the reaction tubes described
later.
[0129] Uniforming the pressure losses of the respective reaction
tubes is effective for reducing variations of the reaction states
by the respective reaction tubes. However, the reaction states
mainly concern effects inside the reaction tubes such as the packed
states of the catalyst in the reaction tubes, but do not concern
effects outside the reaction tubes such as a fluid state of the
heating medium and a reactor structure. Therefore, predicting the
reaction states inside the reaction tubes considering effects
outside the reaction tubes as well and setting the packing
specifications of the catalyst so that the predicted reaction
states of the respective reaction tubes become uniform further
allow reduction in variations of the reaction states by the
respective reaction tubes. The effects outside the reaction tubes
include existence of places having a low heat removal effect
depending on the reaction tubes or on positions in the same
reaction tube.
[0130] Therefore, when packing the catalyst in the reaction tubes
or re-packing the catalyst in the reaction tubes to provide a
uniform pressure loss, the reaction states inside the reaction
tubes are predicted by measuring the temperature of the catalyst
layers in the reaction tubes or conducting a simulation analysis of
the fluid state of the heating medium circulating outside the
reaction tubes with the heat of reaction inside the reaction tubes
using a computer. The packing specifications of the catalyst in the
reaction tubes may be determined according to the prediction
results so that nonuniformity of the reaction states among the
reaction tubes are reduced. A prediction method for the reaction
states inside the respective reaction tubes will be described in
detail in the following section regarding the second invention.
[0131] Further, according to the first invention, use of a catalyst
packing method described below for packing the catalyst allows
further reduction in variations of the reaction states by
respective reaction tubes.
[0132] Therefore, when packing the catalyst in the reaction tubes,
the catalyst may be packed by being allowed to fall using a funnel
having a net in at least a part thereof. Alternatively, the
catalyst may be packed by being allowed to fall while interposing a
chain substance in the reaction tubes so that a lower end of the
chain substance is positioned above an upper end of the catalyst
layers. The catalyst packing methods will be further described in
detail in the following sections regarding the third invention and
the fourth invention.
[0133] Hereinafter, the second invention of the present invention
will be described in detail.
[0134] The second invention, similar to the first invention,
involves a method for vapor phase catalytic oxidation using a fixed
bed multi-tube heat-exchanger type reactor provided with a
plurality of reaction tubes.
[0135] According to the second invention, a description regarding a
heating medium used is similar to as that regarding the heating
medium in the first invention.
[0136] Further, descriptions regarding a raw material gas and a
catalyst are similar to those described in the section of the first
invention.
[0137] Here, specific examples of the catalyst which can be used,
similar to those of the first invention, preferably include the
Mo--Bi mixed oxide catalyst represented by the above formula (1)
and the Mo--V mixed oxide catalyst represented by the above formula
(2).
[0138] The reaction tubes used in the method for vapor phase
catalytic oxidation of the second invention are packed with the
catalyst and, as appropriately, an inert substance for diluting the
catalyst (hereinafter, may also be referred to as "diluent").
[0139] The packing specifications of the catalyst to the reaction
tubes may be determined comprehensively in view of respective
factors such as a catalyst type, a catalyst amount, a catalyst form
(shape, size), a dilution method for the catalyst (diluent type,
diluent amount), and lengths of reaction zones.
[0140] The form (shape, size) of the catalyst used in the method
for vapor phase catalytic oxidation of the second invention is
similar to that described in the first invention. A molded catalyst
or a supported catalyst can be used without any particular
limitation, and in addition, a catalyst may be in any shape.
[0141] Further, descriptions regarding the diluent type and a
mixing ratio of the catalyst and the diluent are similar to those
described in the first invention.
[0142] Further, a description that the packing specifications of
the catalyst may differ by layers of reaction zones within one
reaction tube is similar to that described in the first
invention.
[0143] Next, a prediction method for reaction states inside the
respective reaction tubes in the method for vapor phase catalytic
oxidation of the second invention will be described.
[0144] According to the second invention, the reaction states are
predicted for preventing an emergence of reaction tubes in abnormal
reaction states such as hot spots departing from a normal reaction
state.
[0145] Therefore, the reaction tubes in abnormal reaction states,
differing from the normal reaction state or the reaction tubes that
may be in abnormal reaction states are predicted.
[0146] To be specific, reaction tubes that are not in a uniform
state (in a reaction state of the same level) with other reaction
tubes are selected.
[0147] Further, thermal states inside the reaction tubes are
preferably grasped for predicting the reaction states.
[0148] Measuring temperature of catalyst layers of the reaction
tubes or using a computer simulation analysis enables grasping the
thermal states inside the reaction tubes.
[0149] To be specific, the reaction states different from the
reaction states of other reaction tubes can be predicted: when
temperature of a reaction tube is judged higher than that of other
reaction tubes from results of temperature measurements of the
catalyst layers of the reactions tubes; and when temperature inside
a reaction tube is judged higher than that inside other reaction
tubes from results of computer simulation analysis.
[0150] When grasping the thermal states inside the reaction tubes
through simulation analysis using a computer, a fluid analysis of
the heating medium or an analysis combining the fluid analysis of
the heating medium with an analysis of the heat of reaction inside
the reaction tubes, to be specific, allows grasping of the thermal
states.
[0151] The fluid analysis of the heating medium includes:
determining a layout of baffles or reaction tubes, a structure of a
reactor such as a heating medium feed port, and items regarding the
heating medium such as physical properties of the heating medium or
a flow through rate of the heating medium; and conducting the
simulation. To be specific, a heat-transfer coefficient or a
temperature distribution may be computed by calculating a flow
direction of the heating medium, a flow rate of the heating medium,
or the like using a momentum conservation equation, a mass
conservation equation, an enthalpy conservation equation, or the
like. According to the second invention, CFX (United Kingdom, CFX
Ltd.) can be used for the analysis as a fluid analysis
software.
[0152] Further, the analysis of the heat of reaction inside the
reaction tubes includes: determining items regarding the reaction
tubes such as structures of the reaction tubes, physical properties
of feed gas and the catalyst, a rate equation, or the like; and
conducting the simulation. To be specific, a reaction level may be
determined at respective minute zones inside the reaction tubes
using a momentum conservation equation, a mass conservation
equation, an enthalpy conservation equation, a rate equation, or
the like. According to the second invention, g-PROMS (United
Kingdom, AEA Technology plc) can be used for the analysis as an
analysis software.
[0153] As described above, further incorporating the analysis of
the heat of reaction inside the reaction tubes by considering
portions of poor heat removal using the fluid analysis of the
heating medium enables prediction of the reaction states inside the
respective reaction tubes in all places inside the reactor.
[0154] The inventors of the present invention have confirmed as a
result of the simulation analysis using a computer in a method for
vapor phase catalytic oxidation using a fixed bed multi-tube
heat-exchanger type reactor of a double segment type shown below in
FIG. 2 or a fixed bed multi-tube heat-exchanger type reactor of a
ring and doughnut type shown below in FIG. 3 that: the heat removal
of a flow along the reaction tubes (vertical flow) is worse than
that of the flow perpendicular to the reaction tubes (horizontal
flow); and the heat removal of the vertical flow in a central
portion of the reactor is much worse than that of the vertical flow
of an outer peripheral portion of the reactor.
[0155] Further, increase of the flow through rate of the heating
medium in the fixed bed multi-tube heat-exchanger type reactors was
confirmed to improve the heat removal effect in accordance with the
flow through rate of the heating medium of a horizontal flow.
However, the increase of the flow through rate of the heating
medium did not improve the heat removal effect in a portion of the
heating medium of a vertical flow, particularly in a portion of the
heating medium of a vertical flow in a central portion of the
reactor despite the increase.
[0156] Further, an existence of a portion of poor heat removal was
confirmed in a residence portion of the heating medium in an outer
peripheral portion of the reactor according to a method for vapor
phase catalytic oxidation using a fixed bed multi-tube
heat-exchanger type reactor of a multi-baffle type of FIG. 4.
[0157] Therefore, the portions of poor heat removal are preferably
sufficiently considered to carefully predict the reaction states of
the reaction tubes in those portions.
[0158] Then, according to the second invention, the packing
specifications of the catalyst in the respective reaction tubes are
changed in accordance with the prediction results based on the
above prediction results.
[0159] In other words, the packing specifications of the catalyst
are changed so that the reaction tubes judged to have different
reaction states from the other reaction tubes described above are
brought into the same reaction states as in the other reaction
tubes. That is, the packing specifications of the catalyst are
changed so that nonuniformity of the reaction states is reduced
among the reaction tubes.
[0160] For example, the packing specifications of the catalyst are
changed for a reaction tube judged to have a temperature departing
from a given catalyst layer temperature range, revealed from the
temperature measurement of the catalyst layers in the reaction
tubes. The packing specifications are changed so that the reaction
tube has a catalyst layer temperature of the same level as those of
the other reaction tubes.
[0161] Alternatively, as a result of the simulation analysis using
a computer, the packing specifications of the catalyst are changed
for a reaction tube in a portion of a poor circulating state of the
heating medium, which is a reaction tube judged to have a
temperature departing from a given temperature range because of
inefficient heat removal of the heat of reaction generated in the
reaction tube. The packing specifications are changed so that the
reaction tube has a temperature of the same level as the presumed
temperature inside other reaction tubes.
[0162] A rough standard for the change in the packing
specifications will be described below. For example, peak
temperatures of the catalyst layers of the respective reaction
tubes are determined through the temperature measurement or the
simulation. Next, an average value of the peak temperatures
representing a whole reactor is determined based on the results of
the respective peak temperatures. Then, the average value of the
peak temperatures and the peak temperatures of the respective
reaction tubes are compared. The packing specifications are changed
for the reaction tubes having a temperature difference of
15.degree. C. or more, preferably 10.degree. C. or more, with the
average peak temperature. Here, the peak temperatures of the
catalyst layers refer to temperatures of portions having the
highest temperatures when the catalyst is packed in the reaction
tubes in single layers. The peak temperatures of the catalyst
layers refer to temperatures of portions having the highest
temperatures in respective reaction zones when the catalyst is
packed in several reaction zones. Further, the average peak
temperature is calculated as an average value of the peak
temperatures of the reaction tubes disregarding temperatures of
portions of remarkably poor heat removal.
[0163] According to the second invention, the packing
specifications of the catalyst can be changed considering the
respective factors such as a catalyst type, a catalyst amount, a
catalyst form (shape, size), a dilution method for the catalyst
(diluent type, diluent amount), and lengths of reaction zones. Of
those, the packing specifications may be preferably changed by
changing the amounts of the catalyst and the diluent to adjust the
mixing ratio of the catalyst and the diluent.
[0164] According to the second invention, the packing
specifications may be preferably changed to reduce the temperatures
inside the catalyst layers in the reaction tubes, that is, to a
direction of suppressing the reaction.
[0165] Note that, according to the method for vapor phase catalytic
oxidation of the second invention, feeding a large amount of the
raw materials for increasing the productivity may result in places
of heat removal slower than the increase of the heat of reaction
even in places where the heat generation and the heat removal were
balanced. In such a case, the packing specifications of the
catalyst in the reaction tubes are changed. In addition, it is
effective to stop feed of the raw material gas to the reaction
tubes of extremely poor heat removal portions by plugging or the
like to prevent the flow of the gas.
[0166] As described above, when setting the packing specifications
of the catalyst according to the first invention, variations of the
reaction states by the respective reaction tubes can be reduced by:
predicting the reaction states inside the reaction tubes according
to the second invention; and setting the packing specifications of
the catalyst in the reaction tubes in accordance with the
prediction results so that nonuniformity of the reaction states
among the reaction tubes is reduced.
[0167] In other words, the present invention provides, as a more
preferable mode of the first invention, a method for vapor phase
catalytic oxidation characterized by: predicting the reaction
states inside the reaction tubes by measuring the catalyst layer
temperature of the reaction tubes or conducting the simulation
analysis of the fluid state of the heating medium circulating
outside the reaction tubes and the heat of reaction inside the
reaction tubes using a computer; and determining the packing
specifications of the catalyst in the reaction tubes in accordance
with the prediction results so that nonuniformity of the reaction
states among the reaction tubes is reduced when packing the
catalyst in the reaction tubes according to the first invention.
Here, the items determining the packing specifications of the
catalyst are as described in the section of the first invention or
the second invention.
[0168] Hereinafter, the third invention of the present invention
will be described in detail.
[0169] A catalyst packing method according to the third invention
of the present invention is a catalyst packing method involving
packing of the catalyst while removing the powdered or degraded
catalyst or the like using a funnel having a net in at least a part
thereof.
[0170] A net mesh of the funnel is smaller than the outer diameter
of the catalyst or the like for separating and removing the
catalyst or the like powdered or degraded by vibration or impact
during transfer, transport, and handling of the catalyst.
[0171] A form, a material, and a size of the funnel are not
particularly limited as long as a part of the funnel consists of a
net and the funnel has a structure not allowing the powdered or
degraded catalyst to enter from the net portion into the reaction
tubes.
[0172] An inclined portion of the funnel may be provided with a
wire net, a punching metal, or the like for providing a funnel
consisting of a net in at least a part thereof.
[0173] FIG. 6(a) shows a preferable form of the funnel, and an
inclined portion of a funnel 21 is provided with a net mesh 22. An
angle of the inclination is preferably 10 to 75.degree., more
preferably 30 to 500. If the angle of the inclination is 100 or
less, the catalyst or the like may undesirably reside in the funnel
or in a wire net portion. If the angle of the inclination is
75.degree. or more, separation of the powdered or degraded catalyst
or the like may undesirably become incomplete because of excessive
inclination.
[0174] The mesh portion is preferably provided to position outside
a diameter of the reaction tubes, or a recovery bag (or recovery
container) 23 is provided to cover the mesh portion 22 for
preventing the powdered or degraded catalyst or the like from
entering the reaction tubes of the fixed bed multi-tube
reactor.
[0175] Further, FIGS. 6(b) and (c) respectively are plan views seen
from an A direction and B direction of FIG. 6(a), showing an
example of a funnel size in mm units.
[0176] Examples of the funnel material include tinplate, stainless
steel, and plastic. The funnel size is suitably selected depending
on a size of the reaction tubes of the fixed bed multi-tube
reactor.
[0177] The funnel may have a general form composed of a conical
portion and a straight pipe portion. However, the funnel used is
preferably a half funnel having a perpendicular side and a
partially conical side, and a diameter of the straight pipe portion
is smaller than an inner diameter of the reaction tubes at least in
a portion where the funnel is inserted into the reaction tubes.
Further, the funnel is preferably provided with a wire net on an
inclined side of the partial cone and with a powder reservoir for
receiving fine powders passing through the net.
[0178] The funnel preferably has a size of a sufficient length for
separating or removing the powdered or degraded catalyst or the
like using the wire net provided on the inclined side of the
partial cone within a range not effecting workability.
[0179] According to the third invention, the fixed bed multi-tube
reactor is generally used industrially and is not particularly
limited as described in the sections of the first invention and the
second invention.
[0180] A description regarding the catalyst used in the third
invention is similar to that in the section of the first invention.
Here, specific examples of the catalyst which can be used, similar
to those described in the first invention, preferably include an
Mo--Bi mixed oxide catalyst represented by the above formula (1)
and an Mo--V mixed oxide catalyst represented by the above formula
(2).
[0181] According to the third invention, the catalyst used may also
be a single catalyst or a catalyst diluted with an inert substance,
similar to that in the first invention or the second invention.
[0182] The form of the catalyst (shape, size) used in the method
for vapor phase catalytic oxidation of the third invention is
similar to that described in the first invention or the like. A
molded catalyst or a supported catalyst may be used without any
particular limitation. Further, the catalyst may be in any
shape.
[0183] Further, the descriptions regarding a type and a form of the
inert substance or an amount of the inert substance used are
similar to those in the first invention.
[0184] Further, the packing specifications of the catalyst may
differ by layers of reaction zones in one reaction tube as
described in the first invention.
[0185] The catalyst packing method of the third invention more
preferably involves purging the reaction tubes with dry air or the
like for removing the powdered product of the catalyst generated
inside the reaction tubes. The reaction tubes are packed with the
catalyst while removing the powdered or degraded catalyst using a
funnel with a net in at least a part thereof.
[0186] As described above, when packing the catalyst according to
the first invention, the variations of the reaction states by the
respective reaction tubes can be eliminated by packing the catalyst
according to the packing method of the third invention.
[0187] In other words, the present invention, as a more preferable
mode of the first invention or of a combination of the first
invention and the second invention, provides a method of packing
the catalyst by allowing the catalyst to fall using a funnel with a
net in at least a part of the funnel when packing the catalyst in
the reaction tubes according to the first invention.
[0188] Hereinafter, the fourth invention of the present invention
will be described in detail.
[0189] According to the fourth invention, the fixed bed multi-tube
reactor is generally used industrially and is not particularly
limited as described in the section of the first invention and the
second invention. The fixed bed multi-tube reactor of the fourth
invention particularly preferably has reaction tubes with a length
of 2 to 10 m and a diameter of 50 mm or less.
[0190] A description regarding the catalyst used in the fourth
invention is similar to that in the section of the first invention.
Here, specific examples of the catalyst which can be used, similar
to those described in the first invention, preferably include an
Mo--Bi mixed oxide catalyst represented by the above formula (1)
and an Mo--V mixed oxide catalyst represented by the above formula
(2).
[0191] According to the fourth invention, the catalyst used may be
a single catalyst or a catalyst diluted with an inert substance,
similar to that in the first invention or the second invention.
[0192] The form of the catalyst (shape, size) used in the method
for vapor phase catalytic oxidation of the fourth invention is
similar to that described in the first invention or the like. A
molded catalyst or a supported catalyst may be used without any
particular limitation. Further, the catalyst may be in any
shape.
[0193] Further, the descriptions regarding a type and a form of the
inert substance or an amount of the inert substance used are
similar to those in the first invention.
[0194] The chain substance interposing inside the reaction tubes
according to the fourth invention is not particularly limited as
long as the substance has a thickness or is a material which
reduces a falling speed of the catalyst and does not substantially
disturb the falling of the catalyst. Specific examples of the chain
substance include chains of stainless steel, plastic, or the like
and may be a substance which does not damage or break from contact
with the falling catalyst. The thickness of the chain substance may
be suitably selected from the number of the chain substances used
and the size of the reaction tubes.
[0195] FIG. 8 shows an example of the chain substance having a ring
outer diameter of 6 mm.times.9 mm used in the present invention. A
preferable chain substance includes chains composed of an oval ring
member having a ring wire diameter of 1 to 1.5 mm and a ring outer
diameter of 5 to 15 mm. A wire diameter of less than 1 mm, lacking
in strength may result in break of the chain during use. On the
other hand, a wire diameter of more than 1.5 mm easily results in
winding of the chain to form a "cluster". The ring outer diameter
is preferably within the above range for easy handling. If a joint
exists in the ring member, the joint is preferably welded.
[0196] According to the fourth invention, the number of the chain
substances used for interposing inside the reaction tubes is at
least one. The larger the number, the larger the effect is for
suppressing the powdering or the degradation of the catalyst during
catalyst packing. However, an excess number may hinder the catalyst
from falling, and thus, the number may be suitably selected from
the thickness of the chain substance, the size of the reaction
tubes, or the like.
[0197] The length of chain substance may be provided so that a
lower end of the chain substance is positioned 1 to 100 cm,
preferably 1 to 50 cm, and more preferably 5 to 20 cm above an
upper end of a catalyst layer packed in the reaction tubes.
[0198] According to the fourth invention, the packing
specifications of the catalyst are not particularly limited.
However, multi-layer packing is preferable for changing activity of
the catalyst packed inside the reaction tubes to increase reaction
efficiency of a target reaction using the reaction tubes packed
with the catalyst.
[0199] The multi-layer packing provides several catalyst layers by
dividing the packed layers of the reaction tubes to change the
activity of the catalyst packed inside the reaction tubes. In such
a case, the catalyst is preferably packed inside the reaction tubes
by preparing a chain substance with an adjusted length for each of
the catalyst layers and changing to an adequate chain substance
when packing the target catalyst layer.
[0200] An interposing means for the chain substance inside the
reaction tubes includes a method of hanging the chain substance on
a packing funnel provided on an upper portion of the reaction
tubes. A specific example of the method, as shown in FIGS. 7(a) to
(c), involves: welding in a cross a stainless steel linear member
32 to a stainless steel (SUS304, for example) ring 31 having a
larger diameter than that of a reaction tube so that the chain
substance does not fall inside the reaction tube; and fixing a
chain 33 to the cross portion using a stainless steel wire.
[0201] As described above, when packing the catalyst according to
the first invention, the variations of the reaction states by the
respective reaction tubes can be eliminated by packing the catalyst
according to the packing method of the fourth invention.
[0202] In other words, the present invention, as a more preferable
mode of the first invention or of a combination of the first
invention and the second invention, provides a method of packing
the catalyst by allowing the catalyst to fall by interposing the
chain substance inside the reaction tubes so that the lower end of
the chain substance is positioned above the upper end of the
catalyst layer when packing the catalyst in the reaction tubes
according to the first invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0203] FIG. 1 is a diagram of a mode of a fixed bed multi-tube
heat-exchanger type reactor used in the present invention.
[0204] FIG. 2 is a diagram of a mode of a fixed bed multi-tube
heat-exchanger type reactor used in the present invention.
[0205] FIG. 3 is a diagram of a mode of a fixed bed multi-tube
heat-exchanger type reactor used in the present invention.
[0206] FIG. 4 is a diagram of a mode of a fixed bed multi-tube
heat-exchanger type reactor used in the present invention.
[0207] FIG. 5 is a diagram for explaining Example 6 of the present
invention.
[0208] FIG. 6(a) is a perspective view showing an embodiment mode
of a funnel used in a catalyst packing method of the present
invention.
[0209] FIG. 6(b) is a plan view of (a) seen from an A
direction.
[0210] FIG. 6(c) is a plan view of (a) seen from a B direction.
[0211] FIG. 7(a) is a perspective view showing an embodiment mode
of a chain substance used in a catalyst packing method of the
present invention.
[0212] FIG. 7(b) is a plan view of (a) seen from an A
direction.
[0213] FIG. 7(c) is a plan view of (a) seen from a B direction.
[0214] FIG. 8 is an enlarged view showing an embodiment mode of a
chain substance used in a catalyst packing method of the present
invention.
BEST MODE FOR CARRYING OUT THE INVENTION
[0215] Hereinafter, the present invention will be further described
in detail by way of examples and comparative examples, but the
present invention is not limited by the examples so long as not
departing from the scope of the invention.
<First Invention>
<Standard Conditions>
[0216] Reaction Tubes of a Fixed Bed Multi-Tube Heat-Exchanger Type
Reactor
[0217] A pilot device of a fixed bed reactor consists of a reaction
tube which has an inner diameter of 27 mm and a length of 5 m and
is provided with a jacket for a heating medium. The pilot device
can uniformly control temperature using niter as the heating
medium.
[0218] Former Reaction Catalyst (Propylene Vapor Phase Catalytic
Oxidation Catalyst)
[0219] A catalyst of the following composition (atomic ratio) was
prepared by a method disclosed in JP 63-054942 A as the propylene
vapor phase catalytic oxidation catalyst.
Mo:Bi:Co:Fe:Na:B:K:Si:O=12:1:0.6:7:0.1:0.2:0.1:18:X
[0220] Wherein, X is a value determined from oxidation states of
respective metal elements.
[0221] The reaction tube was packed with 0.86 L of the catalyst,
0.43 L of a mixture containing 70% of the catalyst and 30% of
alumina balls in volume ratio thereon, and 0.43 L of a mixture
containing 50% of the catalyst and 50% of the alumina balls in
volume ratio further thereon.
[0222] Former Reaction Conditions
[0223] A raw material gas having a composition of 9.5 mol % of
propylene, 71.9 mol % of air, and 18.6 mol % of steam was fed to
the reaction tube of the fixed bed multi-tube reactor of the pilot
device or an actual equipment at a flow rate of 1,032 NL/H.
[0224] Reaction Pressure
[0225] An outlet pressure of a latter reactor was adjusted to 50
KPaG (gauge pressure).
EXAMPLE 1
[0226] A pressure loss of the reaction tube when feeding air of the
same volume (1,032 NL/H) as the volume of gas fed under the
standard reaction conditions was 7.1 KPa after packing the former
catalyst in the reaction tube of the pilot device under standard
conditions.
[0227] Further, reaction performance of the reaction tube at a
reaction temperature of 323.degree. C. resulted in propylene
conversion of 98.0% and total yield of acrylic acid and acrolein of
92.1%. (Here, the reaction temperature can also be referred to as
"heating medium temperature" because the reaction temperature can
be determined from the temperature of the heating medium
circulating outside the reaction tube for absorbing heat of
reaction generated from the reaction tube.)
COMPARATIVE EXAMPLE 1
[0228] The catalyst was packed following the same method as in
Example 1 except that catalyst packing time was changed. As a
result, the pressure loss of the reaction tube after catalyst
packing was 5.6 KPa, and the volume of air increased to reach the
same pressure loss of 7.1 KPa as in Example 1 was 1,200 NL/H.
[0229] The reaction was conducted at a heating medium temperature
of 323.degree. C. following the same method as in Example 1 except
that the gas volume fed to the former reaction tube was changed to
1,200 NL/H. The propylene convention was 96.7% and the total yield
of the acrylic acid and the acrolein was 90.1%, resulting in a very
low conversion compared to Example 1.
COMPARATIVE EXAMPLE 2
[0230] The catalyst was packed following the same method as in
Example 1 except that catalyst packing time was changed. As a
result, the pressure loss of the reaction tube after catalyst
packing was 8.4 KPa, and the volume of air decreased to reach the
same pressure loss of 7.1 KPa as in Example 1 was 920 NL/H.
[0231] The reaction was conducted at a heating medium temperature
of 323.degree. C. following the same method as in Example 1 except
that the gas volume fed to the former reaction tube was changed to
920 NL/H. The propylene conversion was 98.8% and the total yield of
the acrylic acid and the acrolein was 91.6%, resulting in an
excessive oxidation reaction.
EXAMPLE 2
[0232] Alumina balls as an inert substance were packed into the
reaction tube of Comparative Example 1, so that the pressure loss
of the reaction tube was 7.1 KPa, the same as in Example 1, when
feeding air of the same volume (1,032 NL/H) as the volume of gas
fed under the standard reaction conditions. The gas volume fed to
the former reactor was 1,302 NL/H, and the reaction was conducted
under the same conditions as in Example 1 at a heating medium
temperature of 323.degree. C. As a result, the propylene conversion
was 97.9% and the total yield of the acrylic acid and the acrolein
was 92.0%, substantially the same result as in Example 1.
[0233] Table 1 collectively shows results of Examples 1 and 2 and
Comparative Examples 1 and 2.
TABLE-US-00001 TABLE 1 With or without Pressure correction of Total
loss catalyst Reac- Pro- yield of after packing tion pylene
acrolein catalyst specification temper- conver- and packing for
adjusting ature sion acrylic (KPa) pressure loss (.degree. C.) (%)
acid (%) Example 1 7.1 Without 323 98.0 92.1 correction Comparative
5.6 Without 323 96.7 90.1 Example 1 correction Comparative 8.4
Without 323 98.8 91.6 Example 2 correction Example 2 5.6 With
correction 323 97.9 92.0
EXAMPLES 3 to 5 and COMPARATIVE EXAMPLES 3 and 4
[0234] Effects of the pressure loss on the catalyst over time after
catalyst packing were determined using the actual equipment.
[0235] The actual equipment was a fixed bed multi-tube exchanger
reactor having 15,000 reaction tubes. The reaction conditions were
basically the same as in Example 1, and an average volume of the
gas fed per reaction tube was 1,250 NL/H.
[0236] 8 reaction tubes packed with a catalyst in different packed
states were prepared by changing the catalyst packing time and the
catalyst packing method, for Examples 3 to 5 and Comparative
Examples 3 and 4, respectively.
[0237] Table 2 shows the pressure loss of the reaction tubes after
catalyst packing and the pressure loss 1 year after start of the
operation. Further, the pressure losses of the 150 reaction tubes
of the reactor were measured. The results showed that an average
pressure loss was 8.5 KPa, the same value as the pressure loss of
the reaction tube in Example 3.
[0238] Table 2 also shows the pressure loss of the reaction tubes
after catalyst packing and the pressure loss 1 year after the start
of the operation in Examples 4 and 5 and Comparative Examples 3 and
4.
[0239] The volume of gas flowing through the reaction tubes having
a pressure loss higher than the average pressure loss was smaller
than the volume of the gas flowing in the reaction tubes having the
average pressure loss. As a result, an excessive reaction occurred,
not only causing catalyst deterioration, but also becoming a cause
of coking. In Comparative Example 3 and Comparative Example 4,
outlet portions of the reaction tubes were black, causing coking,
and completely blocked. In other words, the reaction tubes were
causing yield reduction at the beginning of coking and were
completely clogged ultimately, to result in the reaction tubes not
being used effectively for the oxidation reaction.
TABLE-US-00002 TABLE 2 With or without Pressure correction of loss
catalyst Pressure after packing Difference loss after catalyst
specification with average 1 year packing for adjusting pressure
operation (KPa) pressure loss loss (%) (KPa) Example 3 8.5 Without
0 8.6 correction Example 4 9.4 Without +10 9.8 correction Example 5
10.2 Without +20 11.2 correction Comparative 11.1 Without +30 Not
Example 3 correction measurable Comparative 10.6 Without +24 Not
Example 4 correction measurable
<Second Invention>
[0240] FIG. 1 shows a first embodiment mode of the fixed bed
multi-tube heat-exchanger type reactor used in a method for vapor
phase catalytic oxidation of the second invention.
[0241] FIG. 1 shows: a reactor 1; a raw material gas introducing
port (for a downflow case) or a reaction product gas discharging
port (for an upflow case) 2; a reaction product gas discharging
port (for a downflow case) or a raw material gas introducing port
(for an upflow case) 3; a reaction tube (catalyst packed inside) 4;
an upper tube plate 5; a lower tube plate 6; baffles 7, 8, and 9; a
heating medium outlet nozzle 10; a heating medium inlet nozzle 11;
a heating medium inlet line for reaction temperature adjustment 13;
and a heating medium overflow line 14.
[0242] Note that the fixed bed multi-tube heat-exchanger type
reactor in FIG. 1 has a for case of structure passing the heating
medium in an upflow direction, but the heating medium can be
obviously passed in a downflow direction as well according to the
present invention.
[0243] The raw material gas is mixed with air and/or a diluent gas,
a recycle gas, or the like, introduced from the raw material gas
introducing port (2 or 3) to the reactor (1), and fed to the
reaction tube (4) where the catalyst is packed. The reaction
product gas produced by oxidation through a catalytic oxidation
reaction inside the reaction tube or an unreacted gas is discharged
from the reaction product gas discharging port (3 or 2).
[0244] The heating medium is introduced from the heating medium
inlet nozzle (11) to a reactor shell by a pump (12), passed through
inside the reactor shell while removing the heat of reaction
generated inside the reaction tube, discharged from the heating
medium outlet nozzle (10), and circulated by the pump. Temperature
of the heating medium is controlled by introducing a cooling medium
from a cooling medium nozzle (13), and the medium introduced from
the nozzle (13) is discharged from the heating medium overflow line
(14).
[0245] A structure of the baffles of the fixed bed multi-tube
heat-exchanger type reactor according to the present invention is
not particularly limited. Any type of the fixed bed multi-tube
heat-exchanger type reactor can be used including a double segment
baffle type as shown in FIG. 2, a ring and doughnut baffle type as
shown in FIG. 3, and a multi baffle type as shown in FIG. 4, for
example. In FIGS. 2 to 4, shapes of the baffles and flow of the
heating medium are described.
REFERENCE EXAMPLE 1
[0246] The following experiment indicates that the reaction tube
located in a portion of poor heat removal can be brought under the
same reaction conditions as other reaction tubes by changing the
packing specifications of the catalyst.
[0247] The fixed bed multi-tube heat-exchanger type reactor
consisting of a stainless steel reaction tube having an inner
diameter of 27 mm and a length of 5 m was used. Partially
hydrogenated triphenyl, which is an organic heating medium, was
used as a heating medium. The fixed bed multi-tube heat-exchanger
type reactor is of a type capable of circulating the heating medium
by an external pump and controlling the volume of the heating
medium circulating.
[0248] The reaction tube was packed with a mixture containing 80%
of an Mo--V--Sb catalyst prepared following a conventional
procedure and 20% of alumina balls in volume ratio to a height of
1.8 m and a mixture containing 50% of the catalyst and 50% of the
alumina balls in volume ratio to a height of 1.0 m thereon.
[0249] A mixed gas consisting of 6 mol % of acrolein, 7 mol % of
oxygen, 16 mol % of steam, nitrogen, or the like were fed to the
fixed bed multi-tube heat-exchanger type reactor under a condition
of a contact time of 2 seconds at a heating medium temperature of
265.degree. C. with the heating medium circulating at 2.5
m.sup.3/h.
[0250] An acrolein conversion, an acrylic acid yield, and a peak
temperature of the catalyst layer at this time were respectively
99%, 97%, and 295.degree. C.
[0251] Here, the acrolein conversion and the acrylic acid yield
were respectively determined as follows.
Acrolein conversion (mol %)={(moles of acrolein reacted)/(moles of
acrolein fed)}.times.100
Acrylic acid yield (mol %)={(moles of acrylic acid produced)/(moles
of acrolein fed)}.times.100
[0252] Further, the peak temperature of the catalyst layer was
determined by inserting a multi-point thermocouple (20 points) to
the reaction tube and measuring the temperatures of the respective
points of measurement.
[0253] Next, an experiment was conducted following the same method
as described except that the volume of the heating medium
circulating was changed to 0.5 m.sup.3/h. As a result, the acrolein
conversion, the acrylic acid yield, and the peak temperature of the
catalyst layer were respectively 99.7%, 95.5%, and 313.degree.
C.
[0254] Next, an experiment was conducted following the same method
as described above with the volume of the heating medium
circulating remained at 0.5 m.sup.3/h except that the packing
specifications of the catalyst in the reaction tube was changed.
Here, the Mo--V--Sb catalyst was packed to a height of 1.3 m, and a
mixture containing 40% of the catalyst and 60% of the alumina balls
in volume ratio was packed thereon to a height of 1.5 m. As a
result, the acrolein conversion, the acrylic acid yield, and the
peak temperature of the catalyst layer were respectively 99.1%,
97%, and 296.degree. C. The results were similar to the results of
the initial experiment circulating the heating medium at 2.5
m.sup.3/h.
[0255] The above results confirmed that a conversion, an yield, and
a peak temperature similar to those obtained in good circulating
states of the heating medium (volume of the heating medium
circulated at 2.5 m.sup.3/h) can be attained by changing the
catalyst packing specifications in cases of poor circulating states
of the heating medium (volume of the heating medium circulated at
0.5 m.sup.3/h as described above).
EXAMPLE 6
[0256] The multi-point thermocouples were provided for measuring
the catalyst layer temperatures of the reaction tubes at positions
(A to H) shown in FIG. 5 using the fixed bed multi-tube
heat-exchanger type reactor consisting of 20,000 stainless steel
reaction tubes having an inner diameter of 27 mm and a length of 3
m. The reactor shell was provided with double segment type baffles
for changing a flow path of the heating medium. The partially
hydrogenated triphenyl was used as the heating medium.
[0257] All of the reaction tubes were packed with a mixture
containing 80% of the Mo--V--Sb catalyst, which is the same
catalyst as in Example 1, and 20% of alumina balls in volume ratio
to a height of 1.8 m and a mixture containing 50% of the catalyst
and 50% of the alumina balls in volume ratio to a height of 1.0 m
thereon. The alumina balls were further packed thereon to upper
portions of the reaction tubes.
[0258] A mixed gas consisting of 6 mol % of acrolein, 7 mol % of
oxygen, 16 mol % of steam, and the remaining composed of mostly
nitrogen and minute acrylic acid, acetic acid, carbon dioxide,
carbon monoxide, or the like was fed to the fixed bed multi-tube
heat-exchanger type reactor under a condition of a contact time of
2.5 seconds. The temperature of the heating medium at this time was
260.degree. C.
[0259] Table 3 shows the peak temperatures of the catalyst layer
inside the respective reaction tubes positioned at A to H.
TABLE-US-00003 TABLE 3 Difference with the Reaction tube Catalyst
layer peak average peak position temperature (.degree. C.)
temperature (.degree. C.) A 290 -- B 291 -- C 290 -- D 291 -- E 291
-- F 308 17 G 310 19 H 315 24 The average peak temperature is
291.degree. C., an average value of A to E.
[0260] From the results of Table 3, the average peak temperature in
this case was defined as 291.degree. C.
[0261] The acrolein conversion and the acrylic acid yield at this
time were respectively 99.2% and 95.3%.
[0262] Next, the catalyst layer peak temperatures of the respective
reaction tubes inside the reactor and the average peak temperature
were compared. The reaction tubes having a temperature difference
of more than 10.degree. C. (the reaction tubes positioned at F, G,
and H) were plugged or the packing specifications of the catalyst
were changed therefor.
[0263] Area 1 described in FIG. 5 was a portion of the poorest heat
removal. Therefore, tops and bottoms of the reaction tubes
positioned in Area A including H were plugged so that a reactant
gas did not flow.
[0264] The packing specifications of the reaction tubes positioned
in Area 2 including F and G described in FIG. 5 were changed as
follows. A mixture containing 90% of the catalyst and 10% of the
alumina balls in volume ratio was packed to a height of 1.3 m, and
a mixture containing 40% of the catalyst and 60% of the alumina
balls in volume ratio was packed thereon to a height of 1.0 m. The
alumina balls were further packed thereon to the upper portions of
the reaction tubes.
[0265] The reaction tubes positioned in Area 3 including A, B, C,
D, and E described in FIG. 5 had the catalyst layer peak
temperatures comparable to the average peak temperature. Thus, the
packing specifications were not changed.
[0266] The raw material gas was fed to the reaction tubes of the
above specifications under the similar conditions as described
above. That is, a mixed gas consisting of 6 mol % of acrolein, 7
mol % of oxygen, 16 mol % of steam, the remaining composed of
mostly nitrogen and minute acrylic acid, acetic acid, carbon
dioxide, carbon monoxide, or the like was fed to the fixed bed
multi-tube heat-exchanger type reactor under a condition of a
contact time of 2.5 seconds. The temperature of the heating medium
at this time was 262.degree. C.
[0267] Table 4 shows the peak temperatures of the catalyst layer
inside the respective reaction tubes positioned at A to H.
TABLE-US-00004 TABLE 4 Difference with the Reaction tube Catalyst
layer peak average peak position temperature (.degree. C.)
temperature (.degree. C.) A 291 -- B 292 -- C 290 -- D 291 -- E 292
-- F 293 2 G 292 1 H -- -- The average peak temperature is
291.degree. C., an average value of A to E.
[0268] From the results of Table 4, the average peak temperature in
this case was defined as 291.degree. C. The results confirmed that
the respective reaction tubes had the catalyst layer peak
temperatures comparable to the average peak temperature.
[0269] The acrolein conversion and the acrylic acid yield at this
time were respectively 99.1% and 96.8%.
[0270] As described above, the packing specifications of the
catalyst layers in the reaction tubes were changed to be in similar
reaction states in the same reactor. As a result, nonuniformity of
the reaction states was reduced among the respective reaction
tubes, and the reaction states of the respective reaction tubes
inside the reactor could be made uniform.
[0271] From the above, a method for vapor phase catalytic oxidation
exhibiting satisfactory results such as effectively preventing
formation of hot spots, having high yield of the reaction product
gas, and having a long catalyst life could be provided.
<Third Invention>
[0272] The catalyst for packing used in the following Examples 7 to
9 was an Mo--Bi catalysts molded into cylinders having an outer
diameter of 6 mm, an inner diameter of 2 mm, and a height of 6 mm
through tablet compression. Spherical mullite balls having an outer
diameter of 6 mm were used as an inert substance for dilution
(diluent).
[0273] According to the third invention, powdering and degradation
are defined as follow:
1) powder ratio: a ratio of powder passed through a screen of 10
mesh with respect to the total normal catalyst; and 2) crack ratio:
a ratio of cracked catalyst with respect to the total normal
catalyst
EXAMPLE 7
[0274] The catalyst was packed in the reaction tube of the fixed
bed multi-tube reactor using a packing funnel with a wire net shown
in FIG. 6. The packing funnel had a net mesh of 3 mm and an angle
of inclination of the wire net portion of 35.degree.. A
polyethylene bucket was set at a lower portion of the packing
funnel. 580 g of the Mo--Bi catalyst, as a single catalyst, was
allowed to fall from the end of the packing funnel in 60 seconds.
The powder ratio and the crack ratio of the catalyst separated
below the wire net at this time were respectively 0.51% and 1.04%,
and a recovery rate of the powdered or degraded catalyst was
substantially 100%.
[0275] The recovery rate of the powdered or degraded catalyst was
obtained by removing the packed catalyst without powdering or
degrading and was represented as a ratio with respect to the total
catalyst removed following the definitions of the 1) powder ratio
and the 2) crack ratio.
EXAMPLE 8
[0276] 580 g of the Mo--Bi catalyst, as a single catalyst, was
allowed to fall from the end of the packing funnel in 60 seconds
under same conditions as in Example 7 except that the angle of the
inclination of the wire net portion of the packing funnel was
changed to 50.degree.. The powder ratio and the crack ratio of the
catalyst separated below the wire net at this time were
respectively 0.6% and 0.84%, and recovery and separation rate of
the catalyst at the wire net was about 90%.
EXAMPLE 9
[0277] The catalyst was packed in the reaction tube of the fixed
bed multi-tube reactor using a packing funnel with a wire net shown
in FIG. 6. The packing funnel had a wire net mesh of 4 mm and an
angle of inclination of the wire net portion of 45.degree.. A
polyethylene bucket was set at a lower portion of the packing
funnel. 175 g of the Mo--Bi catalyst and 220 g of a diluent were
allowed to fall from the end of the packing funnel in 40 seconds.
The powder ratio and the crack ratio of the catalyst separated
below the wire net at this time were respectively 0.51% and 1.29%,
and recovery rate of the powdered or degraded catalyst was 95%.
<Fourth Invention>
[0278] Hereinafter, the catalysts for packing used in Examples 10
to 13 were prepared as follows.
[0279] 94.1 g of ammonium paramolybdate was dissolved in 400 ml of
pure water by heating. Next, 7.18 g of ferric nitrate, 25.8 g of
cobalt nitrate, and 38.7 g of nickel nitrate were dissolved in 60
ml of pure water by warming. The two liquid mixtures were gradually
mixed with sufficient stirring.
[0280] Next, to the mixed liquid (slurry), a liquid mixture
containing 0.85 g of borax, 0.38 g of sodium nitrate, and 0.36 g of
potassium nitrate dissolved in 40 ml of pure water by warming was
added and sufficiently stirred. Then, 57.8 g of bismuth
subcarbonate and 64 g of silica were added to the slurry for mixing
under stirring. The slurry was subjected to drying by heating, and
then to heat treatment in air at 300.degree. C. for 1 hour. The
obtained solid was molded into cylinders having an outer diameter
of 6 mm, an inner diameter of 2 mm, and a height of 6 mm through
table compression using a compact molding device. The cylinders
were calcined in a muffle furnace at 480.degree. C. for 8 hours, to
thereby obtain a catalyst. The obtained catalyst is a mixed oxide
having the following atomic ratio, which is a composition ratio of
metal components of the catalyst calculated from the raw
materials.
Mo:Bi:Co:Ni:Fe:Na:B:K:Si=12:5:2:3:0.4:0.2:0.2:0.08:24
[0281] The obtained catalyst was an Mo--Bi catalyst molded into
cylinders having an outer diameter of 6 mm, an inner diameter of 2
mm, and a height of 6 mm through tablet compression. Spherical
mullite balls having an outer diameter of 6 mm were used as an
inert substance for dilution (diluent).
[0282] According to the fourth invention, powdering and degradation
are defined as follows:
1) powder ratio: a ratio of powder passed through a screen of 14
mesh with respect to the total normal catalyst; and 2) crack ratio:
a ratio of cracked catalyst with respect to the total normal
catalyst.
EXAMPLE 10
[0283] A stainless steel spring was fixed at a bottom portion of a
stainless steel straight pipe having an inner diameter of 26.6 mm
and a pipe length of 4.4 m at a position 50 mm above the bottom
portion of the straight pipe. A stainless steel chain having a
length of 2.65 m and consisting of an oval ring member having a
wire diameter of 1.5 mm and an outer diameter of 6 mm.times.9 mm
was hanged (free fall distance of 1.7 m) from an upper portion of a
reaction tube. 650 g of the Mo--Bi catalyst as a single catalyst
was packed by allowing the catalyst to fall from the upper portion.
Note that a distance between a lower end of the chain and an upper
end of the catalyst layer was 5 cm. The powder ratio and the crack
ratio at this time were respectively 0.2% and 3.1%.
COMPARATIVE EXAMPLE 5
[0284] 650 g of the Mo--Bi catalyst as a single catalyst was packed
by allowing the catalyst to fall as in Example 10 except that a
chain was not used (free fall distance of 4.35 m). The powder ratio
and the crack ratio at this time were respectively 0.9% and
25.0%.
EXAMPLE 11
[0285] A stainless steel spring was fixed in the reaction tube of
the Example 10 at a position 1.55 m above the bottom portion of the
reaction tube. A chain having a length of 1.85 m was hanged (free
fall distance of 1.0 m) from the upper portion of the reaction
tube. A diluent catalyst containing 195 g of the Mo--Bi catalyst
and 240 g of the diluent mixed was packed by allowing the catalyst
to fall from the upper portion. Note that a distance between the
lower end of the chain and the upper end of the catalyst layer was
5 cm. The powder ratio and the crack ratio at this time were
respectively 0.4% and 4.8%.
COMPARATIVE EXAMPLE 6
[0286] The diluent catalyst in Example 11 was packed by allowing
the catalyst to fall as in Example 11 except that a chain was not
inserted (free fall distance of 2.85 m). The powder ratio and the
crack ratio at this time were respectively 0.9% and 19.4%.
EXAMPLE 12
[0287] A stainless steel spring was fixed in the reaction tube of
the Example 10 at a position 2.55 m above the bottom portion of the
reaction tube. A chain having a length of 0.9 m was hanged (free
fall distance of 0.95 m) from the upper portion of the reaction
tube. A diluent catalyst containing 140 g of the Mo--Bi catalyst
and 345 g of the diluent mixed was packed by allowing the catalyst
to fall from the upper portion. Note that a distance between the
lower end of the chain and the upper end of the catalyst layer was
50 cm. The powder ratio and the crack ratio at this time were
respectively 0.3% and 5.6%.
COMPARATIVE EXAMPLE 7
[0288] The diluent catalyst in Example 12 was packed by allowing
the catalyst to fall as in Example 12 except that a chain was not
inserted (free fall distance of 1.85 m). The powder ratio and the
crack ratio at this time were respectively 0.6% and 13.4%.
EXAMPLE 13
[0289] A stainless steel spring was fixed at a bottom portion of a
polycarbonate straight pipe having an inner diameter of 24.0 mm and
a pipe length of 1.0 m. A chain having a length of 0.7 m was hanged
(free fall distance of 0.3 m) from the upper portion of the
reaction tube. 35 g of the Mo--Bi catalyst as a single catalyst was
packed by allowing the catalyst to fall. Note that a distance
between the lower end of the chain and the upper end of the
catalyst layer was 2 cm. The powder ratio and the crack ratio at
this time were respectively 0.3% and 0.9%.
COMPARATIVE EXAMPLE 8
[0290] 35 g of the Mo--Bi catalyst as a single catalyst was packed
by allowing the catalyst to fall as in Example 13 except that a
chain was not inserted (free fall distance of 1.0 m). The powder
ratio and the crack ratio at this time were respectively 0.3% and
3.0%.
INDUSTRIAL APPLICABILITY
[0291] According to the first invention of the present invention,
in a method for producing acrolein and acrylic acid, and the like
from a raw material gas such as propane and propylene through vapor
phase catalytic oxidation with molecular oxygen or a molecular
oxygen-containing gas using a fixed bed multi-tube heat-exchanger
type reactor, not only are the variations of the reaction states
among the respective reaction tubes suppressed and is the
improvement on catalyst life achieved, but also acrolein, acrylic
acid, and the like can be produced in high yields. Such results can
be obtained by packing the catalyst in the respective reaction
tubes of the fixed bed multi-tube heat-exchanger type reactor and
then using the reactor for reaction after adjusting the pressure
loss of the reaction tubes to be uniform.
[0292] Further, according to the second invention of the present
invention, a method for vapor phase catalytic oxidation achieving
satisfactory results such as effectively preventing hot spot
formation, yielding a large volume of the reaction product gas, and
extending catalyst life can be provided. These satisfactory results
may be obtained by using the fixed bed multi-tube heat-exchanger
type reactor provided with a plurality of reaction tubes,
circulating a heating medium outside the reaction tubes, and
feeding the raw material gas inside the reaction tubes packed with
the catalyst.
[0293] Further, according to the third invention of the present
invention, the use of the funnel with a net in at least a part of
the funnel for packing the catalyst in the reaction tubes of the
fixed bed multi-tube reactor allows substantially complete
separation or removal of the powdered or degraded catalyst
generated during transfer, transport, and handling of the catalyst.
Therefore, mechanical strength of the catalyst does not have to be
increased more than necessary concerning powdering or the like of
the catalyst during packing thereof. Limitations on catalyst design
become small, enabling catalyst preparation under a broad range of
conditions.
[0294] According to the fourth invention of the present invention,
the resistance of the chain substance can remarkably reduce
powdering or degradation of the catalyst caused by physical impact
during falling of the catalyst, when packing the catalyst in the
fixed bed multi-tube reactor. Therefore, mechanical strength of the
catalyst does not have to be increased more than necessary
concerning powdering or the like of the catalyst during packing
thereof. Limitations on catalyst design become small, enabling
catalyst preparation under a broad range of conditions. Further,
blocking can be prevented during catalyst packing.
* * * * *