U.S. patent application number 10/296255 was filed with the patent office on 2003-08-28 for device and method for carrying out heterogeneously catalysed gas phase reactions with heat tonality.
Invention is credited to Brocker, Franz Josef, Haake, Mathias, Schwab, Ekkehard, Stroezel, Manfred, Worz, Otto.
Application Number | 20030159799 10/296255 |
Document ID | / |
Family ID | 29421460 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159799 |
Kind Code |
A1 |
Brocker, Franz Josef ; et
al. |
August 28, 2003 |
Device and method for carrying out heterogeneously catalysed gas
phase reactions with heat tonality
Abstract
Apparatus for substantially isothermal operation of a
heterogeneously catalyzed gas phase reaction involving a pronounced
exotherm comprises at least one reactor space (101) having an inlet
(131, 141) and an outlet (143), wherein the reactor space is
bounded by heat-removing walls which are spaced apart substantially
uniformly at a distance of .ltoreq.30 mm along the main flow axis
of a reaction gas, the reactor space is fitted with catalyst-coated
tapes (120, 132), the tapes are flexible and pervious to the
reaction gas in all spatial directions and have a surface to volume
ratio of 50 to 5000 m.sup.2/m.sup.3 and also a good thermal
conductivity, the reaction gas flows through the reactor space at a
velocity of .gtoreq.200 m.sup.3 per m.sup.2 of frontal area per
hour, and a heat exchange medium flows on that side of the reactor
wall which is remote from the reactor space.
Inventors: |
Brocker, Franz Josef;
(US) ; Haake, Mathias; (Mannheim, DE) ;
Stroezel, Manfred; (Ilvesheim, DE) ; Worz, Otto;
(Friedelsheim, DE) ; Schwab, Ekkehard; (Neustadt,
DE) |
Correspondence
Address: |
KEIL & WEINKAUF
1350 CONNECTICUT AVENUE, N.W.
WASHINGTON
DC
20036
US
|
Family ID: |
29421460 |
Appl. No.: |
10/296255 |
Filed: |
November 21, 2002 |
PCT Filed: |
May 25, 2001 |
PCT NO: |
PCT/EP01/06034 |
Current U.S.
Class: |
165/4 |
Current CPC
Class: |
B01J 2219/32466
20130101; F28D 9/04 20130101; B01J 2219/32475 20130101; C07C 45/38
20130101; B01J 12/007 20130101; B01J 2219/1944 20130101; B01J
19/0013 20130101; B01J 2219/00085 20130101; B01J 2219/00096
20130101; B01J 19/248 20130101; B01J 19/24 20130101; C07C 47/21
20130101; C07C 45/38 20130101 |
Class at
Publication: |
165/4 |
International
Class: |
F23L 015/02; F28D
017/00 |
Claims
We claim:
1. Apparatus for substantially isothermal operation of a
heterogeneously catalyzed gas phase reaction involving a pronounced
exotherm, comprising at least one reactor space (101) having an
inlet (131, 141) and an outlet (143), wherein the reactor space is
bounded by heat-removing walls which are spaced apart substantially
uniformly at a distance of .ltoreq.30 mm along the main flow axis
of a reaction gas, the reactor space is fitted with catalyst-coated
tapes (120, 132), the tapes are flexible and pervious to the
reaction gas in all spatial directions and have a surface to volume
ratio of 50 to 5000 m.sup.2/m.sup.3 and also a good thermal
conductivity, the reaction gas flows through the reactor space at a
velocity of .gtoreq.200 m.sup.3 per m.sup.2 of frontal area per
hour, and a heat exchange medium flows on that side of the reactor
wall which is remote from the reactor space.
2. Apparatus as claimed in claim 1, wherein the reactor space is
formed by the gap of a heat exchanger.
3. Apparatus as claimed in claim 1 or 2, wherein the reactor space
is formed by the gap of a spiral type, plate type or annular gap
heat exchanger.
4. Apparatus as claimed in any of claims 1 to 3, wherein the tapes
are formed from metals, asbestos substitutes, glass fibers, carbon
fibers and/or plastics.
5. Apparatus as claimed in claim 4, wherein the tapes (120, 132)
are formed by a woven metal fabric or by a loop-drawingly knitted
metal fabric.
6. Apparatus as claimed in any of claims 1 to 5, wherein the
sequence of voids, wires or threads in the reactor space is
ruleless as a consequence of the random orientation of the tapes
(120, 132) with regard to the main flow axis of the reaction
gas.
7. Apparatus as claimed in any of claims 1 to 6, wherein the walls
in the reactor space are spaced from 0.5 to 30 mm, preferably from
1 to 20 mm, particularly preferably from 1.5 to 10 mm, apart.
8. The use of apparatus as claimed in any of claims 1 to 7 in a
process for oxidizing alcohols to aldehydes in the gas phase.
9. The use of apparatus as claimed in any of claims 1 to 7 in a
process for oxidizing 3-methyl-3-buten-1-ol to 3-methyl-2-butenal
in the gas phase as per equation I 2
Description
[0001] This invention relates to a process and apparatus for the
substantially isothermal operation of gas phase reactions involving
a pronounced exotherm, specifically oxidative dehydrogenations,
over a solid catalyst.
[0002] DE-A 42 43 500 discloses the use of specific catalyst-coated
knitted wire inserts for exhaust gas cleaning. The layers of
knitted or woven wire are thermally and/or mechanically fixed in
the wound state. Problems are the complicated construction of the
catalyst insert and the poor heat transport within same.
[0003] DE-A 41 09 227 discloses an exhaust gas filter and/or
catalyst
[0004] (i) with a feed duct leading to a
[0005] (ii) filter or catalyst body composed of metallic materials
of construction, the materials of construction of the filter or
catalyst body using compression-molded wires or fibers in random,
braided, knitted or woven form or in powder, granule or chip form
to form a body that is pervaded by voids and through which the
exhaust gas passes, and
[0006] (iii) with an exit duct for the exhaust gas cleaned by the
filter or catalyst body.
[0007] The filter or catalyst body can have heat exchanger pipes or
ducts passing through it transversely or opposite to the exhaust
gas flow direction through the filter or catalyst body.
[0008] EP-B 201 614 describes a reactor for carrying out
heterogeneous, catalyzed chemical reactions that contains at least
partly corrugated tape-form catalyst bodies whose corrugation is
disposed at an inclination to the main flow axis and oppositely
directed in adjacent plates, the pitch of the corrugation of the
catalyst body being less than the pitch of the adjacent corrugated
plates and the surface area of the catalyst being larger than the
surface area of an adjacent corrugated plate. The catalyst can be a
body which is coated with a catalytically active material and which
may be constructed as braided or knitted wire. The complicated
corrugation of the plates favors bypass formation, inhibits eddying
and thus compromises mass transfer. In addition, the envisioned
compact packing element does not provide for effective removal of
the heat of reaction.
[0009] EP-B 0 305 203 describes the operation of heterogeneously
catalyzed reactions under nonadiabatic conditions. To this end, an
annular reactor chamber with heat-transmitting walls is packed with
monolithic catalysts in the form of catalyst sheets. The monolithic
catalysts have channels which are angled relative to the overall
flow direction, so that the reaction fluid is routed at an acute
angle from one reactor wall to the other. The shearing stress
exerted on the reaction fluid is extremely high (high pressure
drop) in reactor wall vicinity and otherwise rather low (poor mass
transfer). The reactor is complicated to fabricate, since the
pressure drop depends decisively on the geometry between reactor
wall and monolithic catalyst.
[0010] EP-B 0 149 456 relates to a process for preparing a
glyoxylic ester by oxydehydrogenation of the corresponding glycolic
ester in the gas phase using a tubular reactor comprising a
catalyst support made of at least one cylindrical monolith having
essentially the same diameter as the reactor tube and containing
channels from 1 to 10 mm in diameter which lead from the inlet to
the outlet of the reactor tube, from 60 to 90% of the volume of the
monolith being formed by hollow spaces. The channels can form an
angle of from 20 to 70.degree. with the reactor axis. This measure
directs the reaction fluid to the reactor walls and thus promotes
the removal of the heat of reaction. This process has the same
disadvantages as the process known from EP-B 0 305 203.
[0011] DE-A 197 25 378 describes a compact fixed bed reactor for
catalytic reactions in the gaseous and/or liquid phase that is
transited by two streams of material in co- or countercurrent. The
flow channels for the two streams of material are formed by a
concertinaed dividing wall. The folds in this dividing wall have
been formed into undulating structures in such a way that
continuous flow channels are created for the fluid streams. The
undulating structures serve both as spacers between opposite folds
of the dividing wall and as a catalyst support and ensure improved
heat transport to and from the dividing wall. The undulating
structures are rigid constructions whose dimensions limit the
minimum spacing between the folds of the dividing walls and also
the amount of catalyst which can be applied to these undulating
structures. The ratio of surface area of the undulating structures
(ie. of the catalyst) to heat exchanger volume is not more than 800
m.sup.2/m.sup.3 on the basis of a maximum industrially feasible
fold width of 5 mm and a fold angle of 90.degree.. In addition, the
fabrication of the reactor is relatively costly.
[0012] It is an object of the present invention to provide a
reactor for operating heterogeneously catalyzed gas phase reactions
involving a pronounced exotherm that combines good heat removal and
supply at the site of the heterogeneously catalyzed reaction with a
good surface to volume ratio for the catalyst.
[0013] We have found that this object is achieved by an apparatus
for substantially isothermal operation of a heterogeneously
catalyzed gas phase reaction involving a pronounced exotherm,
comprising at least one reactor space having an inlet and an
outlet, wherein
[0014] the reactor space is bounded by heat-removing walls which
are spaced apart substantially uniformly at a distance of
.ltoreq.30 mm along the main flow axis of a reaction gas,
[0015] the reactor space is fitted with catalyst-coated tapes,
[0016] the tapes are flexible and pervious to the reaction gas in
all spatial directions and have a surface to volume ratio of 50 to
5000 m.sup.2/m.sup.3 and also a good thermal conductivity,
[0017] the reaction gas flows through the reactor space at a
velocity of .gtoreq.200 m.sup.3 per m.sup.2 of frontal area per
hour, and
[0018] a heat exchange medium flows on that side of the reactor
wall which is remote from the reactor space.
[0019] The subject apparatus is useful for operating not only
substantially exothermic but also substantially endothermic
reactions, since it provides for rapid heat removal and heat
supply, respectively. Examples of substantially endothermic
reactions include oxidative dehydrogenations such as that of
3-methyl-3-buten-1-ol, while examples of substantially exothermic
reactions include the hydrogenation of double or triple bonds and
also aromatics such as the hydrogenation of benzene to cyclohexane.
The enthalpies of the reactions are for example in the range from
30 to 75 kcal/mol.
[0020] The subject apparatus also makes it possible to operate
under reduced pressure or elevated pressure as well as atmospheric
pressure, ie. at pressures from 1.multidot.10.sup.-3 to 100 bar,
especially from 0.5 to 40 bar. The subject apparatus can thus be
used over a wide pressure range.
[0021] Reaction gas for the purposes of the present invention
denotes the mixture of gaseous reactants and optionally added
further gaseous substances that do not react with the reactants
under the reaction conditions. The heat exchange medium can be a
liquid, a gas or a molten salt bath, depending on the desired
temperature. When the heat exchange medium is used for absorbing
and removing heat, it is also known as cooling fluid. Temperatures
from -20.degree. C. to 400.degree. C. can be efficiently realised.
The rapid heat removal or heat supply made possible by the subject
apparatus provides very accurate heat control. It is possible, for
example, to set a temperature of 370.degree. C..+-.10.degree. C.,
especially .+-.5.degree. C. In contradistinction to traditional
fixed bed reactors, there are no temperature spikes with the use of
the subject apparatus.
[0022] The reactor space can be not only annular but also
cylindrical, rectangular or square.
[0023] The subject apparatus is easily realizable by fitting the
catalyst-coated tapes (catalyst tapes) into the gap of a
commercially available heat exchanger. Thus, the reactor tube does
not conform to the catalyst, but the catalyst tapes are conformed
to the reaction space. Any desired heat exchanger can be used. Not
only annular gap heat exchangers but also plate type heat
exchangers or spiral type heat exchangers are useful. Examples of
heat exchangers include designs as described in ISO 15547 or in W.
R. A. Vauck, H. A. Muller, Grundoperationen chemischer
Verfahrenstechnik, Verlag Theodor Steinkopff Dresden 1974, 4.sup.th
edition, pages 438-440, or in the MB1 section of the VDI Wrmeatlas,
VDI Verlag, 3.sup.rd edition, 1977 (to realize the heat transfers
described in the CB3 section). The wall spacing and hence the gap
width or gap diameter of the heat exchangers used is preferably in
the range from 0.5 to 30 mm, especially in the range from 1 to 20
mm, in particular in the range from 1.5 to 10 mm or from 1.8 to 5
mm.
[0024] When annular gap heat exchangers are used, the catalyst
tapes are installed in the reactor space formed by two coaxial
tubes and are cooled (or respectively heated) through the wall of
the inner tube and/or of the outer tube. This apparatus according
to the invention is also known as an annular gap heat exchanger
reactor. Plate type heat exchangers have a square or rectangular
reactor space which is optionally subdivided by additional
heat-conducting walls which force the reaction gas to take a zigzag
course through the reactor space. A plate type heat exchanger
reactor according to the invention is obtained by installing
catalyst tapes in the reactor space, if necessary without catalyst
tapes being used where a change of direction is greatest in order
that an excessively large pressure drop may be avoided.
[0025] A subject apparatus that utilizes a spiral type heat
exchanger ("spiral type heat exchanger reactor") has a particularly
cylindrical reactor space which is packed very uniformly with
catalyst tapes.
[0026] Catalyst tapes are sheetlike, smooth constructions, which
can be formed as wovens, loop-drawn knits, loop-formed knits,
perforated plates or--in the case of metal as the material of
construction--as a rib mesh.
[0027] It may also be possible to use felts, films or foils, but
these have to be combined with wovens, loop-drawn knits,
loop-formed knits, perforated plates or rib meshes in such a way
that the felts, films or foils have to be oriented parallel to the
main flow direction and the wovens, loop-drawn knits, loop-formed
knits, perforated plates or rib meshes serve as spacers for the
felts, films or foils. It is also possible for felts, films or
foils oriented parallel to the main flow direction to be alternated
with wovens, loop-drawn knits, loop-formed knits, perforated plates
or rib meshes when installed in the reactor space. Preference is
given to using wovens, loop-drawn knits or loop-formed knits.
[0028] Catalyst tapes are flexible, ie. bendable and extendible, in
all spatial directions. They are accordingly unstructured catalyst
articles which are readily conformable to the dimensions of the
reactor space, especially the gaps of commercial heat exchangers.
Their use does not require any fixation or orientation with regard
to the main flow axis. Since catalyst tapes are flexible in all
spatial directions, they become fixed automatically. In general,
the catalyst tapes are introduced individually, curled or in layers
into the reactor space without prior deformation (for example due
to embossing of the surface structure such as corrugations by means
of a tooth wheel roll). This permits a higher packing density for
the catalyst tapes coupled with uniform filling of the reactor
space and maximum suppression of undesirable bypass formation,
which is effected in an increased mass transfer. The catalyst tapes
are installed by manually laying, standing or pushing them into the
gap of the heat exchanger. Limiting factors are the dimensions of
the reactor space and the thickness of the catalyst tapes. Not only
one catalyst tape can be installed but a plurality. The catalyst
tapes can be positioned not only distributed over the entire
reactor space of the heat exchanger but also only in sections
selected by one skilled in the art. Since the catalyst tapes are
flexible in all spatial directions, they can not only be extended
but also layered, folded or curled. By extending is meant the
lengthwise or widthwise stretching of a catalyst tape. Whereas, for
example, corrugated sheets cannot be extended, catalyst tapes can
be extended by up to 60%, depending on their material of
construction. By layering is meant the superposing of at least two
catalyst tapes, and folding is to be understood as meaning the
superposing of one and the same catalyst tape with the direction of
the tape changing by 180.degree. in certain or arbitrarily selected
sections. The layered catalyst tapes may optionally be further
folded or curled.
[0029] The surface area of the catalyst tapes may be increased by
more pronounced folding or curling of the catalyst tapes without
substantially increasing the volume of these more substantially
folded or curled catalyst tapes. The catalyst tapes have a high
surface to volume ratio in the range from 50 to 5000
m.sup.2/m.sup.3. Such a high surface to volume ratio cannot be
achieved with catalyst monoliths or dumpable catalyst material, nor
such a high scope for variation in the adjustment of this surface
to volume ratio. For example, such a high scope for variation is
not achievable with the structured spacers described in DE-A 197 25
378. The catalyst tapes, moreover, are pervious to the reaction gas
and--compared with structured catalyst articles such as monoliths
or dumpable material--have a good heat transfer coefficient (see
VDI Wrmeatlas, VDI Verlag, 3.sup.rd edition, 1977, CB3 section) and
hence good thermal conductivity, so that the heat of reaction is
rapidly transferred by the catalyst tapes to the reaction walls and
vice versa. Another factor promoting rapid heat transport is the
small wall spacings in the reactor space, which are generally
.ltoreq.30 mm, preferably .ltoreq.20 mm, particularly preferably
.ltoreq.10 mm. The volume of the reactor space is predetermined by
the volume of the gaps of commercial heat exchangers.
[0030] The catalyst tapes, moreover, are mechanically very stable,
so that the heterogeneously catalyzed gas phase reactions can be
operated even at high flow velocities for the reaction gas without
significant attrition of the catalyst. The subject apparatus can be
used at low flow velocities, but it is superior to conventional
reactors with catalyst monoliths or dumpable catalyst material
especially at flow velocities .gtoreq.200 1 m 3 frontal area [ m 2
] h ,
[0031] especially at flow velocities .gtoreq.300 2 m 3 frontal area
[ m 2 ] h ,
[0032] in particular at flow velocities .gtoreq.1000 3 m 3 frontal
area [ m 2 ] h .
[0033] The flow velocity is chosen according to process (operation
at reduced pressure, atmospheric pressure or elevated pressure) and
as a function of the ratio of catalyst tapes volume to reactor
space volume. Gas flow velocities up to 70 m/s can be realized in
the apparatus of the invention before the catalyst tapes have been
installed. Typical values of gas flow velocities in heat exchangers
are 40 m/s. When the apparatus according to the invention has been
packed with catalyst tapes, it can be operated at flow velocities
of from 200 to 15000 4 m 3 frontal area [ m 2 ] h ,
[0034] especially at flow velocities of from 300 to 15000 5 m 3
frontal area [ m 2 ] h ,
[0035] in particular at flow velocities of from 1000 to 15000 6 m 3
frontal area [ m 2 ] h .
[0036] The stated velocities are superficial velocities determined
using a gas meter.
[0037] Such high flow velocities are not realizable with dumpable
catalyst material, not only on account of the attrition, but also
on account of the associated high pressure drop. Since, in the
apparatuses according to the invention, significant pressure drop
can be avoided by choosing a suitable flow velocity, no compressors
are needed in this case either to compensate the pressure drop, so
that use of the subject apparatus provides for additional cost
saving over the use of conventional reactors.
[0038] Owing to their mechanical stability, the catalyst tapes are
simple to remove from the reactor spaces and to exchange without
the problems of removing the fine catalyst attritus which are
associated with dumpable catalyst material. It is astonishing that,
when such unstructured catalyst tapes are used, the selectivity of
the heterogeneously catalyzed reactions in the gas phase is
retained or even improved by the rapid heat transport.
[0039] The subject apparatus, moreover, is designed for maintaining
a high but uniform shearing stress on the reaction gas. First, as
mentioned above, it will withstand a high cross-sectional flow
velocity without attrition of the catalyst. Secondly, the reaction
gas is exposed to a uniformly high shearing stress in the reactor
space fitted with catalyst tapes. This provides for uniform mixing
of the reaction gas and hence for a constant degree of dispersion
of the reaction gas as it passes through the reactor space. The
high flow velocities and the efficient mixing of the reaction gas
mean that the apparatuses according to the invention provide
similar conversions to conventional reactors even though--compared
with the operation of the reactions in conventional reactors--the
operation of the reactions in the apparatuses according to the
invention has lower catalyst requirements. A further advantage of
the subject apparatus is that there is no need for costly
structuring of the catalyst or catalyst support, so that it is
again possible to save costs.
[0040] The catalyst tapes generally have a fine structure. In the
case of wovens and loop-drawn knits, the fine structure resides in
the rectangles formed by the wire or thread which each share the
sides with one another. In fact, it is preferable for the angle of
pitch, formed by one side of the two sides of a rectangle with the
main flow axis of the reaction gas, to be randomly distributed. By
`randomly distributed angle of pitch` is meant that the catalyst
tapes are introduced into the reactor space in such a way that
ideally all possible angles of pitch are actualized and ideally a
chaotic meshwork is formed as a result. In such a chaotic meshwork,
the sequence of voids, wires and threads in the reactor space is
ruleless as a consequence of the random orientation of the catalyst
tapes. This minimizes bypass formation within the reactor and
maximizes heat and mass transfer as a consequence of a turbulent
flow regime.
[0041] The materials of construction used for the support are
selected from the group consisting of metallic, ceramic and
plastics materials of construction in line with the deformations
occurring in the course of production, reshaping and use. Useful
metallic, ceramic and plastics materials of construction generally
form fibrous structures. Examples of such metallic materials of
construction are pure metals such as iron, copper, nickel, silver,
aluminum and titanium or alloys such as steels, for example nickel,
chromium and/or molybdenum steel, brass, phosphorus bronze, Monel
and/or nickel silver. Examples of ceramic materials of construction
are alumina, silica (glass fibres) zirconia and/or carbon. Examples
of plastics are polyamides, polyethers, polyvinyl, polyethylene,
polypropylene, polytetrafluoroethylene, polyketones, polyether
sulfones, epoxy resins, alkyd resins, urea and/or melamine resins.
Preference is given to metals, asbestos substitutes, glass fibers,
carbon fibers and/or plastics, especially metals, ie. pure metals
and alloys, since these have a very good heat transfer coefficient.
Very particular preference is given to inexpensive stainless steels
which are given an appropriate catalytic coating.
[0042] The tapes coated with catalyst according to the invention
are in particular woven or loop-drawingly knitted metal fabrics.
For the purposes of the present invention, loop-drawingly knitted
metal fabrics are metal fabrics formed from one continuous metal
thread. Woven metal fabrics, in contrast, are fabrics formed from
at least two metal threads. The wire diameter is generally in the
range from 0.01 to 5.0 mm, preferably from 0.04 to 1.0 mm, in the
case of woven or loop-drawingly knitted metal fabrics. The mesh
size can be varied within wide limits. The catalyst tapes can be
produced by the process described in U.S. Pat. No. 4,686,202 and
EP-B 0 965 384.
[0043] Catalyst tapes embodied as woven metal fabrics can further
be coated by the process described in EP-B 0 564 830. EP-B 0 564
830 does not expressly describe the coating of loop-drawingly
knitted metal fabrics with catalyst, but they shall be treated in
the same way as woven metal fabrics. The coating of woven or
loop-drawingly knitted metal fabrics with catalysts may also be
effected by conventional dip processes, for example according to
the process described in EP-A 0 056 435.
[0044] The disclosures of U.S. Pat. No. 4,686,202, EP-B 0 965 384,
EP-B 0 564 830 and EP-A 0 056 435 are hereby fully incorporated by
reference.
[0045] When the metal forming the woven or loop-drawingly knitted
metal fabric is itself catalytically active (possibly after a
treatment), coating may be dispensed with entirely.
[0046] The invention will now be more particularly described with
reference to FIGS. 1 to 3.
[0047] FIG. 1 shows a schematic drawing of a plate type heat
exchanger reactor according to the invention,
[0048] FIG. 2 shows a side view of the interior of a spiral type
heat exchanger reactor,
[0049] FIG. 3 shows a further side view of a spiral type heat
exchanger reactor.
[0050] FIG. 1 shows an inventive plate type heat exchanger reactor
(101). The catalyst-coated tapes bear the reference numeral 120.
131 designates the feed for the reaction gas into the reactor space
and 143 its exit line. The feed and exit lines for the cooling
fluid bear the reference numerals 144 and 142 respectively.
[0051] FIG. 2 shows a side view of a spiral type heat exchanger
reactor according to the invention. 131 identifies the feed for the
reaction gas into the reactor space (reactor inlet). 132 identifies
the reactor passage which will receive the catalyst-coated tapes,
which will take up the entire space in more or less dense packing.
133 identifies the cooling passage, which is to receive the cooling
fluid.
[0052] FIG. 3 is a side view of a spiral type heat exchanger
reactor and identifies the arrangement of the feed and discharge
stubs. 141: reaction gas feed (reactor inlet), 142: cooling fluid
discharge, 143: reaction gas discharge (reactor outlet), 144:
cooling fluid feed. Reaction gas and cooling fluid are here
arranged in countercurrent in order that heat transfer may be
maximized. If the amount of heat released at the reactor inlet
specifically is critical with regard to, for example, selectivity
and catalyst stability, then a cocurrent arrangement is
advisable.
[0053] The example hereinbelow illustrates the invention.
INVENTIVE EXAMPLE
[0054] Oxidation of 3-methyl-3-buten-1-ol to 3-methyl-2-butenal in
the Gas Phase as per Equation I 1
[0055] The reaction is conducted over a silver catalyst. The
catalyst according to the invention is prepared by coating a woven
tape of heat-resistant stainless steel, material No. 1.4764 (as per
Stahl-Eisenliste, 8th edition, published by: Verein Deutscher
Eisenhuttenleute), with silver in an electron beam vapor deposition
unit. This coating technique was used to coat the woven metal tape
on both sides with 300 nm of Ag. 50 cm.sup.2 of this woven catalyst
tape were introduced in a double layer--without deformation--into
an annular gap heat exchanger reactor 2 mm in width. The amount of
active component was 34 mg of silver. To oxidatively dehydrogenate
3-methyl-3-buten-1-ol (MBE), a mixture of 85% by weight of MBE and
15% by weight of H.sub.2O was vaporized at 150.degree. C., mixed
with preheated air and superheated by means of a preheater to an
inlet temperature of 370.degree. C.
[0056] After leaving the annular gap, the gaseous reaction product
was cooled with cooling brine to 0.degree. C., and the condensate
was collected in a cooled separator. The gas fraction of the
reaction product passed through dry ice (to condense the low boiler
fractions) to a gas chromatography analyzer and thereafter by a gas
meter into the waste gas. The combined quantities of condensate
were separated into an organic and an aqueous phase. Both phases
were analyzed. The result obtained was a selectivity of 83% from a
conversion of 54%.
Comparative Example
[0057] Instead of the annular gap heat exchanger reactor in the
inventive example, a fixed bed reactor with a 30 mm deep layer of
silver granules conforming to DE-A 27 15 209 is installed into the
same plant and the conversion of MBE is carried out similarly to
the inventive example. The results are summarized in the table
which follows:
1 Superficial MBE Superficial velocity air velocity Conversion
Selectivity Catalyst Reactor [g/cm.sup.2 h] [l/cm.sup.2 h] [%] [%]
Woven tape coated with Annular gap heat exchanger 279 94 54 83 300
nm layer of reactor, 2 mm Ag (34 mg of Ag in total) passage width
Ag granules, Fixed bed reactor, 69 27 54 73 17 g of Ag, about 4.5
cm.sup.3 30 mm bed height
[0058] It can be seen that, for the same conversion, the
selectivity of the comparative example is 10% worse than that of
the inventive example.
[0059] In addition, the inventive example is more economical, since
only 0.034 g of silver had to be used instead of 17 g of silver.
Another economic plus is that the ability to employ higher flow
velocities makes it possible to obtain a higher conversion per
hour.
* * * * *