U.S. patent application number 14/903337 was filed with the patent office on 2017-07-06 for manufacture of methylolalkanes with augmented heat transfer and improved temperature control.
The applicant listed for this patent is Oxea Bishop LLC. Invention is credited to Howard W. Brooks, Guido D. Frey, Fred Gaytan, Tracy Kevin Hunt, Norman Nowotny, Donald K. Raff, Marcos L. Schroeder, William E. Slinkard, Michael J. Stone, Heinz Strutz.
Application Number | 20170190646 14/903337 |
Document ID | / |
Family ID | 51398856 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170190646 |
Kind Code |
A2 |
Stone; Michael J. ; et
al. |
July 6, 2017 |
Manufacture of Methylolalkanes with Augmented Heat Transfer and
Improved Temperature Control
Abstract
A multistage tubular reaction system and method for preparing
methylol derivatives of an aldehyde includes a tubular reaction
system with a plurality of successive reactor stages comprising a
plurality of jacketed reaction tubes provided with a cooling system
adapted to control flow of a cooling medium through said jacketed
reaction tubes. The cooling medium flow is controlled independently
in different stages in response to temperature measurements in the
reaction system to regulate temperature. In order to further reduce
temperature spikes and byproduct generation, aldehyde is stepwise
added to the production stream at a plurality of feed ports
proximate to reaction tubes equipped with tube inserts to enhance
mixing and heat transfer.
Inventors: |
Stone; Michael J.; (Lake
Jackson, TX) ; Brooks; Howard W.; (Bay City, TX)
; Strutz; Heinz; (Moers, DE) ; Raff; Donald
K.; (Waynesville, NC) ; Frey; Guido D.;
(Mulheim, DE) ; Nowotny; Norman; (Essen, DE)
; Schroeder; Marcos L.; (Andover, KS) ; Gaytan;
Fred; (Kingsville, TX) ; Hunt; Tracy Kevin;
(Corpus Christi, TX) ; Slinkard; William E.;
(Richmond, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Oxea Bishop LLC |
Dallas |
TX |
US |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20170050907 A1 |
February 23, 2017 |
|
|
Family ID: |
51398856 |
Appl. No.: |
14/903337 |
Filed: |
July 23, 2014 |
PCT Filed: |
July 23, 2014 |
PCT NO: |
PCT/US2014/047718 PCKC 00 |
371 Date: |
January 7, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61862554 |
Aug 6, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B01J 2208/02 20130101;
B01J 8/06 20130101; C07C 29/38 20130101; B01J 19/2425 20130101;
B01J 2208/00061 20130101; B01J 2208/0053 20130101; B01J 2208/00106
20130101; B01F 5/0615 20130101; C07C 29/38 20130101; B01J
2219/00094 20130101; B01J 8/04 20130101; B01J 2219/00772 20130101;
B01J 8/065 20130101; B01F 2005/0632 20130101; B01F 15/065 20130101;
B01J 2208/00212 20130101; B01J 19/242 20130101; B01F 2005/0637
20130101; C07C 31/20 20130101; B01J 8/067 20130101 |
International
Class: |
C07C 29/38 20060101
C07C029/38; B01J 19/24 20060101 B01J019/24; B01J 8/06 20060101
B01J008/06 |
Claims
1. A method of making a methylolalkane from formaldehyde and a
C.sub.2 or higher condensable aldehyde in a multistage process
comprising: (a) providing a formaldehyde containing stream to a
tubular reaction system with a plurality of successive reaction
stages; (b) adding a C.sub.2 or higher condensible aldehyde and
optionally a base to the formaldehyde containing stream wherein at
least one of the C.sub.2 or higher condensible aldehyde or base are
added to the formaldehyde containing stream at a plurality of
successive feed points to provide a production stream which is
progressively provided with additional C.sub.2 or higher
condensible aldehyde or base as the production stream advances
through the successive reaction stages; and (c) converting the
C.sub.2 or higher condensible aldehyde and formaldehyde to a
methylolalkane, wherein (i) the production stream is fed to a
plurality of tubular reaction sections provided with tube inserts
following addition of the C.sub.2 or higher condensable aldehyde or
base; or (ii) there is provided a cooling control system adapted to
control temperature and flow of a cooling medium wherein the flow
of the cooling medium is independently controlled in different
stages of the reaction system in response to temperature
measurements in respective stages.
2. The method according to claim 1, wherein the production stream
is fed to a plurality of tubular reaction sections provided with
tube inserts following addition of the C.sub.2 or higher
condensable aldehyde and/or base.
3. The method according to claim 2, wherein said tube inserts are
displacement flow inserts.
4. The method according to claim 3, wherein said tube inserts are
wire-wrapped tube inserts.
5. The method according to claim 3, wherein the plurality of
reaction sections with tube inserts are characterized by a tube
diameter, D, and the tube insert is configured such that the ratio
of D/De is from 1.5 to 3, De = 4 Nfa .pi. D ##EQU00003## where
D.sub.e is the heat transfer equivalent diameter and Nfa is the net
free area inside of the tube.
6. The method according to claim 1, wherein there is provided a
cooling control system adapted to control temperature and flow of a
cooling medium, and the flow of the cooling medium is independently
controlled in different stages of the reaction system in response
to temperature measurements in respective stages.
7. The method according to claim 6, wherein said tubular reaction
system with a plurality of reaction stages includes tubular
reaction sections jacketed with a cooling medium.
8. The method according to claim 1, wherein the methylolalkane is
trimethylolpropane and the aldehyde which is condensable with
formaldehyde is n-butyraldehyde.
9. The method according to claim 1, wherein the methylolalkane is
neopentyl glycol and the aldehyde which is condensable with
formaldehyde is isobutyraldehyde.
10. The method according to claim 1, wherein the C.sub.2 or higher
condensible aldehyde is added to the formaldehyde containing stream
at a plurality of successive feed points to provide a production
stream which is progressively provided with additional C.sub.2 or
higher condensible aldehyde as the production stream advances
through the successive reaction stages.
11. The method according to claim 1, wherein base is added to the
formaldehyde containing stream at a plurality of successive feed
points to provide a production stream which is progressively
provided with additional base as the production stream advances
through the successive reaction stages.
12. The method according to claim 1, comprising adding the C.sub.2
or higher condensible aldehyde and an inorganic base to the
formaldehyde containing stream at a plurality of successive feed
points to provide a production stream which is progressively
provided with additional C.sub.2 or higher condensible aldehyde and
inorganic base as the production stream advances through the
successive reaction stages.
13. The method according to claim 1, wherein said base is an
inorganic base selected from potassium hydroxide, calcium hydroxide
and sodium hydroxide.
14. The method according to claim 1, wherein the temperature of the
production stream is maintained between 30.degree. C. and
75.degree. C.
15. A multistage tubular reaction system for preparing methylol
derivatives of a C.sub.2 or higher condensible aldehyde comprising:
(a) a tubular reaction system with a plurality of successive
reactor stages comprising a plurality of reaction tubes; (b) a
reaction system inlet adapted to provide a formaldehyde containing
stream to the tubular reaction system; (c) a plurality of feed
ports adapted to provide at least one of the C.sub.2 or higher
condensible aldehyde or a base to the formaldehyde containing
stream at a plurality of successive feed points to provide a
production stream which is progressively provided with additional
C.sub.2 or higher condensible aldehyde or base as the production
stream advances through successive reaction stages, Said reaction
system being further characterized in that there is further
provided (i) a plurality of tube inserts disposed in reaction tubes
proximate to said feed ports such that the production stream is fed
to a reaction tube with a tube insert following addition of the
C.sub.2 or higher condensable aldehyde and/or base; or (ii) a
cooling control system adapted to control temperature and flow of a
cooling medium wherein the flow of the cooling medium is
independently controlled in different stages of the reaction system
in response to temperature measurements in respective stages.
16. The multistage tubular reaction system for preparing methylol
derivatives of a C.sub.2 or higher condensible aldehyde according
to claim 15, wherein the tubular reaction system comprises
displaced flow inserts such that the ratio of D/De is from 1.5 to
3, with D as the inside diameter of the tube and De is the heat
transfer equivalent diameter.
17. The multistage tubular reaction system for preparing methylol
derivatives of a C.sub.2 or higher condensible aldehyde according
to claim 15, wherein the reaction system is adapted to provide both
C.sub.2 or higher condensible aldehyde and base to the successive
stages of the reaction system such that the production stream is
progressively provided with additional C.sub.2 or higher
condensible aldehyde and base as the production stream advances
through successive reaction stages.
18. The multistage tubular reaction system for preparing methylol
derivatives of a C.sub.2 or higher condensible aldehyde according
to claim 15, wherein the reaction system comprises a plurality of
reaction tubes cooled with a coolant such that the temperature of
the production stream is maintained between 30.degree. C. and
75.degree. C.
19. The multistage tubular reaction system for preparing methylol
derivatives of a C.sub.2 or higher condensible aldehyde according
to claim 15, wherein the reaction system comprises a plurality of
reaction tubes of a jacketed construction with an outer shell, an
annular cooling channel and an inner reaction tube defining a
reaction zone and wherein the annular cooling channel receives
coolant.
Description
CLAIM FOR PRIORITY
[0001] This application is based on International Application No.
PCT/US2014/047718 FILED Jul. 23, 2014 of the same title which was
based on U.S. Provisional Application No. 61/862,554 also of the
same title filed Aug. 6, 2013, the priorities of which are hereby
claimed and the disclosures of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present invention relates to improved manufacture of
methylolalkanes such as trimethylolpropane (TMP) by way of
multistage reaction in a tubular reactor with a plurality of tube
banks. Staged addition and temperature control through the use of
tube inserts and independently regulated cooling of the tube banks
reduces temperature spikes and unwanted byproducts such as
2-ethylhexyl dimers, methylolalkane formals, methanol and so
forth.
BACKGROUND
[0003] Manufacture of methylolalkanes is carried out in a variety
of processes including by the reaction of formaldehyde with another
aldehyde with formaldehyde (hereinafter sometimes referred to as
reactant aldehyde), that is, an aldehyde having at least one
hydrogen bound at the .alpha.-carbon atom adjacent to the carbonyl
moiety. The base-catalyzed aldol reaction of the reactant aldehyde
with formaldehyde initially generates the methylol derivative of
the aldehyde in the first reaction step. Then the aldehyde moiety
may be converted in a second reaction step by reaction with further
formaldehyde and base in a Cannizzaro-reaction into an alcohol
group. Simultaneously, the formate of the base is generated. The
1.sup.st reaction step, the aldol reaction, and the 2.sup.nd
reaction step, a Cannizzaro reaction, may either be carried out
separately or in one working step. The bases used both for the base
catalyzed reaction step 1 and also for the reaction step 2 which is
stoichiometric in relation to the base quantity may optionally each
independently be, for example, alkali metal or alkaline earth metal
hydroxides, carbonates or tertiary amines. In the so-called
inorganic Cannizzaro process, an inorganic base is used, such as
sodium hydroxide, potassium hydroxide or calcium hydroxide. The
resultant formates, such as potassium formate or calcium formate
can be used in further industrial applications such as an assistant
in the leather industry.
[0004] The reactions of formaldehyde with acetaldehyde,
propionaldehyde, n-butyraldehyde and isobutyraldehyde are of
particular interest. The corresponding reaction products are
pentaerythritol, trimethylolethane, trimethylolpropane and
neopentylglycol. These are polyhydric alcohols of great industrial
significance which find use, for example, in the field of coating
resins, power coating, foam production and polyester
production.
[0005] In particular, the manufacture of TMP according to the
inorganic Cannizzarro process is disclosed, for example, in U.S.
Pat. No. 3,183,274, U.S. Pat. No. 5,948,943, U.S. Pat. No.
7,253,326 and U.S. Pat. No. 8,354,561. Batchwise production of TMP
is seen in U.S. Pat. No. 7,253,326 to Eom et al., wherein the batch
production is followed by a semi-continuous product recovery train.
While batchwise production may be advantageous in terms of raw
material use, such systems are relatively difficult to operate and
capital costs are higher than continuous systems.
[0006] TMP is prepared from n-butyraldehyde and formaldehyde. In
one preferred process, base-catalyzed aldol reaction initially
generates 2,2-dimethylolbutyraldehyde in a first reaction step
which is then converted to a TMP-formate mixture by way of a
Cannizzaro reaction. The TMP-containing mixture is typically
extracted with an organic solvent, such as ethyl acetate, thereby
providing an organic phase comprising TMP and an aqueous phase
containing the formate. The solvent is separated and the crude TMP
is purified by distillation. Typical processing is seen in U.S.
Pat. No. 5,603,835 to Cheung et al., Comparative Example 1, Col. 7.
See, also, U.S. Pat. No. 5,948,943 to Supplee et al. referred to
above.
[0007] The reaction of the aldehyde with formaldehyde is highly
exothermic and can result in excessively high temperatures in the
reaction zone before the heat can be removed. The temperature
spikes lead to efficiency losses due to side reactions. In order to
reduce said temperature spikes, the art generally teaches to use a
relatively dilute aqueous formaldehyde solution and aqueous
solution of the inorganic base in order to moderate temperature.
Because of the presence of large amounts of water in the reaction
mixture, the heat capacity is relatively high so that the
exothermic heat of the reaction does not raise the temperature of
the mixture to a level above the desired range.
[0008] Besides the large amount of water, it is conventionally
typical to use formaldehyde in substantial excess over the
theoretical amount based on the reactant aldehyde. In cases where
n-butyraldehyde is reacted with formaldehyde to produce
trimethylolpropane the art teaches generally a formaldehyde excess
of about 1 to 7 moles or so over the formaldehyde needed for the
actual reaction.
[0009] Commonly, the aqueous formaldehyde solution is blended with
the starting aldehyde continuously to produce a stream of aqueous
mixed aldehydes and the aqueous solution of the inorganic base is
injected into this stream in a mixing zone. The reaction mixture is
then fed to a reaction zone. Heat generation is most problematical
at or near the mixing zone where the reactants are most highly
concentrated. Heat generated in these areas leads to temperature
spikes and byproduct generation. As will be appreciated from the
foregoing references, byproducts can cause color and other product
quality problems, leading to higher purification expense in
addition to loss of efficiency because of lower yields. Moreover,
large amounts of water needed as a temperature moderator are
difficult and expensive to process.
SUMMARY OF INVENTION
[0010] In connection with methylolalkane manufacture, byproducts
can be reduced significantly if the reaction of the aqueous
formaldehyde, a C.sub.2 or higher condensible aldehyde and
optionally an aqueous solution of inorganic base is conducted in a
tube reactor where the reactants are added in stages. After each
addition of reactants, the proximate tube section contains a tube
insert in order to augment heat transfer from the exothermic
reaction. Alternatively, or in combination with tube inserts,
temperature is independently controlled in the various stages to
reduce temperature spikes.
[0011] The tube insert may be a static mixer insert, a boundary
layer interrupter insert, a swirl flow insert, a displaced flow
insert or a combination of these types of inserts as is discussed
hereinafter. Various configurations and types of tube inserts are
commercially available from Koch Heat Transfer Company and their
use is discussed in Chemical Engineering Process, September 2012,
pages 19-25; Shilling, Richard, L.; the disclosure of which is
incorporated herein by reference.
[0012] The tube reactor according to another aspect of the
invention comprises a series n of tubes and each series contains m
single tubes, where m can vary between reactor stages. The staged
addition of the reactants in accordance with the invention occurs
at various locations and preferably in the first tube of a series
of tubes. In particular the aldehyde and the aqueous solution of
the inorganic base are added to the various stages while the
aqueous formaldehyde solution flows through the tube reactor.
[0013] The tube reactor may be designed as a double-pipe reactor
with the reaction zone in the inner tube and a coolant in the outer
tube, sometimes referred to herein as a jacketed construction as
discussed hereinafter.
[0014] In the process mode of the staged addition of the aldehyde
and the aqueous solution of the inorganic base to each series of
tubes, it is also possible to install a temperature indication
point on each series in order to control the flow of the cooling
through each series of tubes, depending on the reaction heat
generated in the specific series of tubes.
[0015] Further details and advantages will become apparent from the
discussion which follows.
DESCRIPTION OF DRAWINGS
[0016] The invention is described in detail below in connection
with numerous examples and in connection with the attached Figures.
In the Figures:
[0017] FIG. 1 is a schematic diagram illustrating the inventive
process employing a tube reactor with the staged addition of
n-butyraldehyde and an aqueous solution of potassium hydroxide
wherein each series of tubes has a temperature indication
controller which is used to control a valve manipulating the
cooling flow through that series depending on the heat of reaction
generated in that series;
[0018] FIG. 2 is a schematic sectional view of a reactor tube with
a tube insert residing in a cooling conduit;
[0019] FIG. 3 is a view in perspective of a section of reactor tube
provided with a wire-wrapped displacement insert;
[0020] FIG. 4 is a view in perspective of a static mixer tube
insert; and
[0021] FIGS. 5(a) to 5(d) are views in perspective of 4 different
types of swirl tube inserts.
DETAILED DESCRIPTION
[0022] The invention is described in detail below in connection
with the Figures for purposes of illustration, only. The invention
is defined in the appended claims. Terminology used throughout the
specification and claims herein is given its ordinary meaning as
supplemented by the discussion immediately below.
[0023] "Aggregate" and like terminology refers to the total amount
of reactants or material added to the reaction system by adding the
amounts supplied to each stage. For example, the aggregate amount
of reactant aldehyde added to the system includes the sum of the
amounts supplied at each stage.
[0024] A C.sub.2 or higher condensible aldehyde is a two carbon or
more carbon aldehyde which will undergo condensation with
formaldehyde to form a methylol derivative of that aldehyde.
Aldehydes condensible with formaldehyde generally have at least one
hydrogen bound at the .alpha.-carbon atom adjacent to the carbonyl
moiety. Useful higher aldehydes are virtually all alkanals having
an acidic hydrogen atom in the .alpha.-position to the carbonyl
group. Aliphatic aldehydes having from 2 to 24 carbon atoms may be
used as starting materials and may be straight-chain or branched or
else contain alicyclic groups. Equally, araliphatic aldehydes are
suitable as starting materials, provided that they contain at least
one hydrogen in the .alpha.-position to the carbonyl group. In
general, aralkyl aldehydes having from 8 to 24 carbon atoms,
preferably from 8 to 12 carbon atoms, are used as starting
materials, for example phenyl acetaldehyde. Preference is given to
aliphatic aldehydes having from 2 to 12 carbon atoms. Especially
preferred C.sub.2 or higher condensible aldehydes include
acetaldehyde, propionaldehyde, n-butyraldehyde and
isobutyraldehyde.
[0025] Unwanted byproducts avoided in accordance with the invention
include dimers such as 2-ethylhexyl dimers produced by self-aldol
condensation of butyraldehyde and may include a plurality of
impurities believed derived from reaction of monomethylol compounds
such as monomethylol butyraldehyde. Such impurities include for,
example, [0026] monocyclic TMP-formal (MCF):
[0026] ##STR00001## [0027] monolinear bis-TMP-formal (MBLF or
TMP-BMLF): [0028]
[C.sub.2H.sub.5C(CH.sub.2OH).sub.2CH.sub.2O].sub.2CH.sub.2 [0029]
Methyl-(monolinear)TMP-formal: [0030]
C.sub.2H.sub.5C(CH.sub.2OH).sub.2CH.sub.2OCH.sub.2OCH.sub.3
[0031] and di-TMP:
##STR00002## [0032]
2-[2,2-bis(hydroxymethyl)butoxymethyl]-2-ethylpropane-1,3-diol
[0033] In a process including a Cannizzarro process, staging base
addition also reduces unwanted methanol generation which increases
raw material efficiency.
[0034] As used herein, a Cannizzarro process refers to
methyloalkane synthesis where the condensate intermediate is
reacted with additional formaldehyde and base to yield the
corresponding methylolakane, for example, a Cannizzarro TMP
synthesis as shown in the following scheme:
##STR00003##
[0035] "Tube insert" and like terminology refers to a part disposed
in a reaction tube to enhance mixing and heat transfer. A tube
insert may be a static mixer insert, a boundary layer interrupter
insert, a swirl flow insert, a displaced flow insert or a
combination of these types of inserts. Particularly preferred is a
wire-wrapped displacement flow insert which combines swirl flow and
displacement flow augmentation. Displaced-flow inserts increase
heat transfer by blocking flow furthest from the tube wall and
increasing the Reynolds number of the liquid and therefore the
U-value of the system. In connection with the present invention, it
also extends the area in which the reaction is occurring, which, in
turn, reduces the final peak temperature seen in the reactor by
increasing the amount of area used for heat transfer in critical
areas. By using a wire-wrapped tube insert, some swirl flow is
induced as well, which imparts a helical flow path which further
increases the mixing and turbulence at the wall, which may be
operable to change flow from a laminar operation to a turbulent
operation in that tube, depending upon conditions. In preferred
embodiments employing displaced flow inserts, the ratio of
D/D.sub.e (defined below) is from 1.5 to 3. In the most preferred
embodiments, inserts are used in selected sections of reactor pipe
only so as not to overtax the feed pumps of the reaction
system.
[0036] "Heat transfer equivalent diameter" or D.sub.e is defined by
the relationship:
De = 4 Nfa .pi. D ##EQU00001##
where Nfa is the net free area inside of the tube and D is the
(inside) diameter of the tube.
[0037] "Methylol derivative" and like terminology refers to
condensation products of formaldehyde and aldehydes condensible
with formaldehyde as well as the corresponding polyol end products
formed by reduction of the condensation product with formaldehyde
or hydrogenation. Methylol derivatives include methylolalkanes and
methylolaldehydes.
[0038] "Proximate" refers to closeness in position of a feed port
and generally means that a feed point is proximate to a reactor
tube section with a tube insert if less than 30% of added reactant
aldehyde reacts over a reactor length prior to entry into the
reactor tube section with a tube insert or if the feed point is at
a distance of less than 6 meters from the reactor tube section with
a tube insert. In preferred embodiments, a proximate feed point is
within a distance of 6 meters of a reactor tube section with a tube
insert and still more preferably a proximate feed point is within a
distance of 5 meters of a reactor tube section with a tube insert.
In many cases a proximate feed point is within a distance of 3
meters of a reactor tube section with a tube insert.
[0039] A "stage" of a multistage reaction system is a portion of
the reactor system discretely configured with respect to other
stages by way of an additional feed port for reactants or catalyst
or independent temperature control of the stage, or by way of a
separate flow of cooling medium to the stage.
[0040] "Successive" refers to a serial arrangement of reactor
stages, for example, where later reaction stages are downstream of
initial stages as is seen in FIG. 1.
[0041] Referring to FIG. 1, there is illustrated schematically a
reaction system 10 comprising multiple banks or stages S1, S2, S3
and so forth of reaction tubes such as tubes indicated at 12, 14,
16 and so forth. Each bank preferably has multiple tubes connected
in series within each bank as shown schematically. 3,4,5,6 or more
stages may be employed, each having 3-10 tubes in series if so
desired. Stages without additional reactant feed may be interposed
between stages receiving fresh charges of reactants.
[0042] Reaction system 10 also includes a cooling system which
includes a plurality of coolant feeds 20 for providing coolant to
the reaction tubes and a plurality of return lines 22 for returning
coolant to the cooling system. Also provided are a plurality of
temperature indicator controllers 24, 26, 28, 30, a cooler 35, and
a plurality of control valves indicated at 40, 42, 44, and 46.
[0043] The reaction tubes are connected in series as indicated
schematically and have the structure generally illustrated in FIGS.
2 and 3, although only the tubes receiving a fresh charge of
aldehyde reactant need be provided with a tube insert to enhance
mixing and heat transfer. Likewise, reactor stages without
additional reactant feed may include inlet tubes without tube
inserts since the stream concentration profiles are already
relatively well developed.
[0044] Referring to FIGS. 2 and 3, there is shown reaction tube 12,
which has an outer shell 60, and annular cooling channel 62 and an
inner reaction tube 64 which is provided with a tube insert 66. The
reaction tube has an inside diameter, D. Preferably, insert 66 is a
wire-wrapped cylinder, a combination swirl flow and displacement
insert which reduces residence time in the areas where reactants
are introduced and heat transfer is most critical.
[0045] Insert 66 thus has a cylindrical body 68, a wire wrap 70 and
resides in reaction tube 64 as shown in FIG. 3. The net free area
72 is thus defined between insert 66 and the inner wall of tube
64.
[0046] The reaction tubes in system 10 without inserts are of the
same general configuration, but the inner channel is
unrestricted.
[0047] In preferred cases, the reaction tubes with inserts have a
ratio of D/De of from 1.5 to 3 as noted above.
[0048] Instead of a wire wrapped displacement insert, a static
mixer insert having the geometry shown in FIG. 4 could be utilized.
Static mixers are operative to transport, by their mechanical
construction, the fluid at the tube wall to the center of the tube
and to fold these transported regions of fluid into each other.
This dramatically increases heat transfer because it increases the
local temperature difference between portions of the bulk
(tubeside) fluid and the tube wall. Static mixers are particularly
useful in a flow that is laminarized.
[0049] Alternatively, a swirl flow tube insert such as the twisted
tape swirl inserts shown in FIGS. 5(a)-5(d) could be employed, if
so desired. Twisted tapes impart rotational flow which has two
effects. It imparts a helical flow path along the inside wall of
the tube, thereby producing a high velocity along the tube wall
that is a function of the helical flow angle. It also imparts a
combination of flow rotation and centripetal force away from the
center of the tube that in single-phase flow, increases mixing and
turbulence at the tube wall. This creates turbulent flows at
Reynolds numbers that would be characteristic of laminar or
transition flows in tubes without inserts. Inducing turbulence at a
lower Reynolds number enhances heat transfer.
[0050] In operation, a stream 100 of aqueous formaldehyde is fed to
system 10 via reaction tube 12 of bank S1 along with potassium
hydroxide and n-butyraldehyde via a feed port 101. Tube 12 has a
tube insert as discussed in connection with FIGS. 2 and 3. After
passing through tube 12, the reaction mixture proceeds through
additional tubes in bank S1 where the reaction proceeds and stream
100 becomes enriched in methylolated product before being passed to
the next stage of the system.
[0051] Additional potassium hydroxide and n-butyraldehyde is
provided to stream 100 via another feed port 102 as the stream is
fed to reactor stage S2 wherein the first tube is provided with a
tube insert as discussed above. Stream 100 proceeds through the
tubes of stage S2 such as tube 14 before exiting the stage.
[0052] The outlet of bank S2 is optionally provided with cooler 35
to further regulate temperature in the system.
[0053] After exiting bank S2 and cooler 35, stream 100 is provided
with additional butyraldehyde and potassium hydroxide at a feed
port indicated at 103 and fed to reactor tube bank S3 as shown. The
first tube of bank S3 is likewise provided with a tube insert,
whereas the subsequent tubes of the bank need not have inserts.
[0054] Stream 100 is passed through the tubes of bank S3 and
thereafter still additional butyraldehyde and potassium hydroxide
may be added in subsequent stages if so desired, or the stream may
be provided to additional reactor banks without further providing
reactants.
[0055] During operation of system 10 as described above, the
temperature in the reaction tubes is regulated independently in the
various reaction tube banks by way of a plurality of temperature
indicator controllers (TIC's), control valves and one or more
coolers such as cooler 35. Generally, the temperature in the
reaction medium is maintained between 35.degree. C. and 75.degree.
C. Preferably, the temperature in the reaction medium is maintained
at between 35.degree. C. and 65.degree. C. at all times and
temperature spikes are minimized or eliminated.
[0056] To this end, coolant feed 20 is pumped to reactor banks S1,
S2 and S3 such that the coolant circulates through the annular
cooling channels of the reaction tubes before returning to the
coolant system via return lines 22. TIC controllers sense the
temperature of the coolant and regulate control valves in order to
maintain a target temperature of the coolant thus maintaining a
target temperature of the reaction medium as well. The controllers
and valves are configured such that the temperature of each stage
can be independently controlled.
[0057] TIC's 24, 26, 30 sense the reaction temperature in banks S1,
S2 and S3 and regulate the flow of the coolant through valves 40,
42, 46 in order to maintain target reaction temperatures in the
banks. Another TIC 28 senses temperature in cooler 35 and controls
coolant flow via valve 44 to further adjust temperatures in the
system.
[0058] The inventive system may be sized and operated in a variety
of operating modes wherein reactants and catalyst are added in
stages to minimize temperature spikes and maintain target
temperatures.
[0059] The amount of reactants employed will vary depending upon
the process employed and the products made; for example, the
aggregate formaldehyde: C.sub.2 and higher aldehyde reactant mole
ratio differs with the C.sub.2 and higher aldehyde reactant. If a
Cannizzaro reaction scheme is included, acetaldehyde requires a
minimum of ratio of formaldehyde:acetaldehyde of 4:1,
n-butyraldehyde requires a minimum of ratio of
formaldehyde:n-butyraldehyde of 3:1, and isobutyraldehyde requires
a minimum of ratio of formaldehyde:isobutyraldehyde of 2:1. For
n-butyraldehyde recommended ranges of formaldehyde:butyraldehyde
are from 3.01:1 to 10:1.
[0060] A set of preferred operating parameters for making TMP from
n-butyraldehyde in a Cannizzarro process are as follows:
TABLE-US-00001 Reaction Medium 35.degree. C.-65.degree. C.
Temperature Aqueous Formaldehyde 10%-50% Concentration (wt %
Formaldehyde) Aggregate Formaldehyde/ 3.01:1-10:1 Reactant Aldehyde
Molar Ratio Aggregate Inorganic Base/ 1:1-2:1 Reactant Aldehyde
Molar Ratio preferably 1:1-1.5:1
[0061] Introducing the aldehyde in increments raises the effective
formaldehyde/reactant aldehyde ratio and reduces the formation of
dimers through self-condensation of the C.sub.2 or higher
condensable aldehyde. So also, staged addition of base lowers the
base/formaldehyde ratio in the initial stages and reduces methanol
generation in connection with a Cannizzarro process. Various
operating schemes include the schemes (a), (b) and (c): [0062] (a)
Wherein the C.sub.2 or higher condensible aldehyde is added in a
fixed proportion with inorganic base at said plurality of
successive feed points to provide a production stream which is
progressively provided with additional C.sub.2 or higher
condensible aldehyde as the production stream advances through the
successive reaction stages; [0063] (b) Wherein the C.sub.2 or
higher condensible aldehyde and inorganic base are provided in an
upstream feed point in larger amounts relative to amounts provided
in a downstream feed point. Providing larger portions of reactants
in early stages provides additional residence time and is desirable
if adequate cooling is available in the system. One preferred
protocol in a Cannizzarro process is to provide 30-60% of the
aggregate amount of both the base and the C.sub.2 or higher
condensible aldehyde in early reaction stage(s); [0064] (c) Wherein
the inorganic base is provided in a downstream feed point in a
larger amount relative to an amount provided in an upstream feed
point to provide a production stream which is provided with
inorganic base at higher levels in a later stage as compared with
levels of inorganic base in an initial stage. [0065] Said process
options may include the option of using different ratios of base
and condensable aldehyde along the feeding points, as long as the
total of all additions equals the targeted component ratios.
[0066] After the production stream 100 exits the last bank of the
reaction system, further work-up includes extracting formates from
the reclaimed TMP and distillation of the crude TMP to purified
form as is known in the art. Typically, purification of the crude
product includes a multistage water/ethyl acetate extraction
system, as well as one or more distillation tower (s).
[0067] The process and apparatus of the present invention are
especially suited to the inorganic Cannizzarro process of the class
described in U.S. Pat. No. 3,183,274, U.S. Pat. No. 5,948,943, U.S.
Pat. No. 7,253,326 and U.S. Pat. No. 8,354,561 referred to above.
Alternatively, the apparatus and process methodology could be
employed in connection with an organic Cannizzarro process or a
condensation/hydrogenation methylolalkane process described in U.S.
Pat. No. 7,301,058.
[0068] There is thus provided in accordance with the invention a
method of making a methylolalkane from formaldehyde and a C.sub.2
or higher condensable aldehyde in a multistage process comprising:
(a) providing a formaldehyde containing stream to a tubular
reaction system with a plurality of successive reaction stages; (b)
adding a C.sub.2 or higher condensible aldehyde and optionally a
base to the formaldehyde containing stream wherein at least one of
the C.sub.2 or higher condensible aldehyde or base are added to the
formaldehyde containing stream at a plurality of successive feed
points to provide a production stream which is progressively
provided with additional C.sub.2 or higher condensible aldehyde or
base as the production stream advances through the successive
reaction stages; and (c) converting the C.sub.2 or higher
condensible aldehyde and formaldehyde to a methylolalkane, wherein
(i) the production stream is fed to a plurality of tubular reaction
sections provided with tube inserts following addition of the
C.sub.2 or higher condensable aldehyde or base; or (ii) there is
provided a cooling control system adapted to control temperature
and flow of a cooling medium wherein the flow of the cooling medium
is independently controlled in different stages of the reaction
system in response to temperature measurements in respective
stages.
[0069] In one preferred embodiment, both C.sub.2 or higher
condensible aldehyde and an inorganic base are added to the
formaldehyde containing stream at a plurality of successive feed
points. The inorganic base may be selected from potassium
hydroxide, calcium hydroxide and sodium hydroxide.
[0070] In yet another preferred embodiment, the production stream
is fed to a plurality of tubular reaction sections provided with
tube inserts following addition of the C.sub.2 or higher
condensable aldehyde and/or base. The tube inserts may be
displacement flow inserts such as wire-wrapped tube inserts. The
plurality of reaction sections with tube inserts may be
characterized by a tube diameter, D, and the tube insert may be
configured such that the ratio of D/De is from 1.5 to 3, where
De = 4 Nfa .pi. D ##EQU00002##
and where Nfa is the net free area inside of the tube.
[0071] In another preferred embodiment, there is provided a cooling
control system adapted to control temperature and flow of a cooling
medium, and the flow of the cooling medium is independently
controlled in different stages of the reaction system in response
to temperature measurements in respective stages.
[0072] The inventive process may be carried out wherein the
methylolalkane is pentaerythritol and the aldehyde which is
condensable with formaldehyde is acetaldehyde or wherein the
methylolalkane is trimethylolethane and the aldehyde which is
condensable with formaldehyde is propionaldehyde. The inventive
process may also be carried out wherein the methylolalkane is
trimethylolpropane and the aldehyde which is condensable with
formaldehyde is n-butyraldehyde or wherein the methylolalkane is
neopentyl glycol and the aldehyde which is condensable with
formaldehyde is isobutyraldehyde.
[0073] One way of carrying out the process is wherein the C.sub.2
or higher condensible aldehyde is added to the formaldehyde
containing stream at a plurality of successive feed points to
provide a production stream which is progressively provided with
additional C.sub.2 or higher condensible aldehyde as the production
stream advances through the successive reaction stages. So also,
base may be added to the formaldehyde containing stream at a
plurality of successive feed points to provide a production stream
which is progressively provided with additional base as the
production stream advances through the successive reaction
stages.
[0074] Typically, the inorganic base and the C.sub.2 or higher
condensable aldehyde is added to the production stream in at least
3 discrete locations and/or the tubular reaction system has at
least 3 stages.
[0075] A preferred construction is wherein said tubular reaction
system with a plurality of reaction stages includes tubular
reaction sections jacketed with a cooling medium.
[0076] In most cases, the temperature of the production stream is
maintained between 30.degree. C. and 75.degree. C. and in a
preferred case the temperature of the production stream is
maintained between 35.degree. C. and 65.degree. C.
[0077] In one mode of operation, said C.sub.2 or higher condensible
aldehyde is added in a fixed proportion with inorganic base at said
plurality of successive feed points to provide a production stream
which is progressively provided with additional C.sub.2 or higher
condensible aldehyde as the production stream advances through the
successive reaction stages.
[0078] In another mode of operation, said C.sub.2 or higher
condensible aldehyde and inorganic base are provided in an upstream
feed point in larger amounts relative to amounts provided in a
downstream feed point.
[0079] In still yet another mode of operation, said inorganic base
is provided in a downstream feed point in a larger amount relative
to an amount provided in an upstream feed point to provide a
production stream which is provided with inorganic base at higher
levels in a later stage as compared with levels of inorganic base
in an initial stage.
[0080] In another aspect of the invention, There is provided a
multistage tubular reaction system for preparing methylol
derivatives of a C.sub.2 or higher condensible aldehyde comprising:
(a) a tubular reaction system with a plurality of successive
reactor stages comprising a plurality of reaction tubes; (b) a
reaction system inlet adapted to provide a formaldehyde containing
stream to the tubular reaction system; (c) a plurality of feed
ports adapted to provide at least one of the C.sub.2 or higher
condensible aldehyde or a base to the formaldehyde containing
stream at a plurality of successive feed points to provide a
production stream which is progressively provided with additional
C.sub.2 or higher condensible aldehyde or base as the production
stream advances through successive reaction stages, said reaction
system being further characterized in that there is further
provided (i) a plurality of tube inserts disposed in reaction tubes
proximate to said feed ports such that the production stream is fed
to a reaction tube with a tube insert following addition of the
C.sub.2 or higher condensable aldehyde and/or base; or (ii) a
cooling control system adapted to control temperature and flow of a
cooling medium wherein the flow of the cooling medium is
independently controlled in different stages of the reaction system
in response to temperature measurements in respective stages.
[0081] In one construction, the reaction system is preferably
provided with a cooling control system adapted to independently
control the flow of cooling medium in each stage of the reaction
system in response to temperature measurements in respective
stages.
[0082] In its various constructions, the reaction system is
provided with a plurality of tube inserts disposed in reaction
tubes proximate to said feed ports such that the production stream
is fed to a reaction tube with a tube insert following addition of
the C.sub.2 or higher condensable aldehyde and/or base, for
example, wherein the reaction system is provided with a a plurality
of tube inserts disposed in reaction tubes proximate to said feed
ports such that the production stream is fed to a reaction tube
with a tube insert following addition of the C.sub.2 or higher
condensable aldehyde and/or base.
[0083] The tube inserts may be selected from static mixer inserts,
boundary layer interrupter inserts, swirl flow inserts, displaced
flow inserts or a combination of these inserts. One class of
preferred inserts comprise wire wrapped displaced flow inserts.
[0084] While the invention has been described in detail,
modifications within the spirit and scope of the invention will be
readily apparent to those of skill in the art. Such modifications
are also to be considered as part of the present invention. In view
of the foregoing discussion, relevant knowledge in the art and
references discussed above in connection with the Background of the
Invention, the Summary of Invention and Detailed Description, the
disclosures of which are all incorporated herein by reference,
further description is deemed unnecessary. In addition, it should
be understood that aspects of the invention and portions of various
embodiments may be combined or interchanged either in whole or in
part. Furthermore, those of ordinary skill in the art will
appreciate that the foregoing description is by way of example
only, and is not intended to limit the invention.
* * * * *