U.S. patent application number 14/431408 was filed with the patent office on 2017-10-05 for process for the production of dialkyl succinate from maleic anyhdride.
The applicant listed for this patent is JOHNSON MATTHEY DAVY TECHNOLOGIES LIMITED. Invention is credited to Rikard Umberto Andersson, Paul Gordon, Andrew George Hiles, Graham Reed, Simon Nicholas Tilley.
Application Number | 20170283362 14/431408 |
Document ID | / |
Family ID | 49680025 |
Filed Date | 2017-10-05 |
United States Patent
Application |
20170283362 |
Kind Code |
A9 |
Reed; Graham ; et
al. |
October 5, 2017 |
Process For The Production Of Dialkyl Succinate From Maleic
Anyhdride
Abstract
In a process for the production of dialkyl succinate from a
feedstock comprising maleic anhydride, feed in the liquid phase is
provided to a reactor operated at a temperature of at least about
150.degree. C. The feed is contacted with hydrogen at a pressure of
at least about 300 psig in the presence of an acid tolerant
catalyst and an alkanol wherein at least some of the carbon carbon
double bonds of the maleic anhydride are hydrogenated to form
succinic acid and that the heat generated promotes esterification
to dialkyl succinate in situ. A stream of dialkyl succinate is
recovered from the reactor.
Inventors: |
Reed; Graham; (London,
GB) ; Hiles; Andrew George; (London, GB) ;
Andersson; Rikard Umberto; (London, GB) ; Tilley;
Simon Nicholas; (Thornaby, GB) ; Gordon; Paul;
(Thornaby, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
JOHNSON MATTHEY DAVY TECHNOLOGIES LIMITED |
London |
|
GB |
|
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20160214922 A1 |
July 28, 2016 |
|
|
Family ID: |
49680025 |
Appl. No.: |
14/431408 |
Filed: |
October 13, 2014 |
PCT Filed: |
October 13, 2014 |
PCT NO: |
PCT/GB2014/053075 PCKC 00 |
371 Date: |
March 26, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C07C 67/08 20130101;
C07C 67/08 20130101; C07C 69/40 20130101 |
International
Class: |
C07C 67/08 20060101
C07C067/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 14, 2013 |
GB |
1318175.5 |
Claims
1. A process for the production of dialkyl succinate from a
feedstock comprising maleic anhydride, said process comprising the
steps of: (a) providing the feed in the liquid phase to a reactor
operated at a temperature of at least about 150.degree. C.; (b)
contacting said feed with hydrogen at a pressure of at least about
300 psig in the presence of an acid tolerant catalyst and an
alkanol wherein at least some of the carbon carbon double bonds of
the maleic anhydride are hydrogenated to form succinic acid and
that the heat generated promotes esterification to dialkyl
succinate in situ; and (c) recovering a stream comprising dialkyl
succinate from the reactor.
2. The process according to claim 1 wherein the feed to the reactor
comprises at least 90% maleic anhydride.
3. The process according to claim 1 wherein the alkanol is
methanol.
4. The process according to claim 1 wherein the reaction is carried
out at a temperature of from about 150.degree. C. to about
240.degree. C.
5. The process according to claim 1 wherein the esterification
reaction is carried out in the absence of a catalyst.
6. The process according to claim 1 wherein an esterification
catalyst is used.
7. The process according to claim 6 wherein a combined catalyst is
used.
8. The process according to claim 1 wherein the saturation reaction
is carried out at a temperature in the range of from about
150.degree. C. to about 240.degree. C.
9. The process according to claim 1 wherein a hydrogen pressure of
about 300 psig to about 900 psig is used.
10. The process according to claim 1 wherein the succinate produced
is recycled to the reactor.
Description
[0001] The present invention relates to a process for the
production of dialkyl succinate from a feedstock comprising maleic
anhydride.
[0002] It is known to produce diols by reaction of dicarboxylic
acids and/or anhydrides, or mono or di-alkyl esters, lactones, and
mixtures thereof with hydrogen. Commercially, where the desired
product is 1,4-butanediol, typically with the co-products
tetrahydrofuran and .gamma.-butyrolactone, the starting material is
normally a dialkyl ester of maleic acid and/or anhydride, such as
dimethyl maleate or diethyl maleate, which may contain minor
amounts of dialkyl fumarate and/or dialkyl succinate.
[0003] Information relating to these processes can be found in, for
example, U.S. Pat. No. 4,584,419, U.S. Pat. No. 4,751,334,
WO86/03189, WO88/00937, U.S. Pat. No. 4,767,869, U.S. Pat. No.
4,945,173, U.S. Pat. No. 4,919,765, U.S. Pat. No. 5,254,758, U.S.
Pat. No. 5,310,954 and WO91/01960.
[0004] The dialkyl maleates which are used as feedstock in these
conventional reaction processes may be produced by any suitable
means. The production of dialkyl maleates for use in such processes
is discussed in detail in U.S. Pat. No. 4,584,419, U.S. Pat. No.
4,751,334 and WO88/00937.
[0005] In one conventional process for the production of
1,4-butanediol and co-product tetrahydrofuran with optional
production of .gamma.-butyrolactone, a dialkyl ester, such as
dimethyl maleate together with any residual methanol from the
esterification reactor, is fed to a vaporiser where it is vaporised
by a stream of hot cycle gas fed to the vaporiser. The hot cycle
gas stream may be mixed with make-up hydrogen. The cycle gas will
normally contain a high concentration of hydrogen gas but may also
include other gases including hydrocarbons, carbon oxides, methane
and nitrogen. Further, where the cycle gas includes recycled gases
from downstream, condensables, including product ether, methanol,
water, co-products, and by-products, may also be present.
[0006] The combined vaporous stream from the vaporiser is then
passed to a reactor where it is reacted to form 1,4-butanediol,
tetrahydrofuran and/or .gamma.-butyrolactone. The product stream is
cooled and the reaction products are condensed and separated from
the excess cycle gas before being passed to a refining zone. In the
refining zone the various products are separated and the
1,4-butanediol and the tetrahydrofuran are removed. The
.gamma.-butyrolactone, together with the intermediate dimethyl
succinate and some 1,4-butanediol, may be recycled. In one
arrangement the .gamma.-butyrolactone may be at least partially
extracted in an optional refining zone and recovered. The methanol
water stream separated from the product mix will be recycled
upstream. In general, a significant portion of the 1,4-butanediol
produced by this or other conventional methods is subsequently
converted to tetrahydrofuran.
[0007] The overall reaction which occurs is a series of steps and
includes a final dehydration step in which the tetrahydrofuran is
produced. A probable reaction path is set out in Scheme 1.
##STR00001##
[0008] Reaction 1 may be regarded as hydrogenation of the ester
(and is a reaction of the carbon/carbon double bond), Reaction 2
may be regarded as hydrogenolysis (and is a reaction of the
saturated ester to butanediol, .gamma.-butyrolactone and by-product
butanol) and Reaction 3 may be regarded as dehydration (and is a
reaction of butanediol to tetrahydrofuran).
[0009] An alternative process is described in WO99/35113 in which
maleic anhydride esters are fed to a reaction process in which
three different catalysts are used. First the maleate is converted
to the succinate in the presence of the first catalyst, which is a
heterogeneous selective hydrogenation catalyst, at a temperature of
from 120.degree. C. to 170.degree. C. and a pressure of from 3 to
40 bara. The succinate is then passed directly to the presence of
the second catalyst where it is converted mainly into
.gamma.-butyrolactone. The product of the reaction with the second
catalyst is then fed directly to the presence of a third catalyst
which is used to dehydrate the .gamma.-butyrolactone to produce
tetrahydrofuran. Some of the .gamma.-butyrolactone formed in the
presence of the second catalyst is transferred to a second reaction
loop operating at a higher pressure where it is converted to
1,4-butanediol.
[0010] As the first step in Scheme 1 and the first catalyst used in
the alternative process described in WO99/35113 relates to the
hydrogenation of the dimethyl maleate to dimethyl succinate, it has
been suggested that dimethyl succinate or diethyl succinate may be
suitable starting materials for the reaction with hydrogen to form
1,4-butanediol, tetrahydrofuran and/or .gamma.-butyrolactone.
[0011] One process in which dimethyl succinate is used in the
production of tetrahydrofuran and 1-4-butanediol is described in
U.S. Pat. No. 4,656,297. In this process, methanol is added to the
ester feed to increase conversion and reduce transesterification.
Another example of a process in which dimethyl succinate is
suggested as a feed is WO99/35136 in which reaction with hydrogen
occurs over two different catalysts, to form a mixture of
tetrahydrofuran and .gamma.-butyrolactone.
[0012] An alternative process is described in WO03/006446 in which
feed material selected from mono-esters of unsaturated dicarboxylic
acids and/or anhydrides, diesters of unsaturated dicarboxylic acids
and/or anyhydrides, unsaturated lactones, and mixtures of two or
more thereof is reacted with hydrogen. This process comprises the
steps of: [0013] (a) vaporising the organic feed material in a
vapourising zone into the hydrogen containing stream to form an
organic feed material carrying hydrogen stream; [0014] (b)
contacting the organic feed material carrying hydrogen stream with
a catalyst in a vaporiser, said vaporiser operating under reaction
conditions such that at least some of the carbon carbon double
bonds are saturated; [0015] (c) supplying the hydrogen-containing
stream containing the vaporised at least partially saturated feed
to a reaction zone comprising catalyst and operating under reaction
conditions; and [0016] (d) recovering from the reaction zone a
product stream comprising an ether and/or diol and/or a
lactone.
[0017] Whilst this process successfully provides the desired
products, and offers an improved process in terms of economics and
efficiency over earlier processes, it is desirable to further
improve the economics and efficiency of the process.
[0018] An improved process is described in WO2005/058855 in which
it is intended to minimise the cycle gas requirements and
minimising the production of unwanted by-product. The described
process comprises the steps of: [0019] (a) supplying a stream
comprising at least a portion of the organic feed material selected
from mono-esters of unsaturated dicarboxylic acids and/or
anhydrides, diesters of unsaturated dicarboxylic acids and/or
anhydrides, unsaturated lactones and mixtures of two or more
thereof in the presence of hydrogen to a pre-reactor zone
comprising catalyst and operating under reaction conditions and
contacting said feed with a hydrogen containing stream such that at
least some of the carbon carbon double bonds are saturated; [0020]
(b) vaporising the at least partly saturated feed into the hydrogen
containing stream in a vaporising zone; [0021] (c) supplying the
hydrogen-containing stream containing the vaporised at least
partially saturated feed to a reaction zone comprising catalyst and
operating under reaction conditions; [0022] (d) recovering from the
reaction zone a product stream comprising the ether and optionally
diol and/or lactone; and [0023] (e) recycling depleted
hydrogen-containing stream to at least the pre-reactor zone or the
vaporisation zone.
[0024] Thus, in some of these processes at least some of the
unsaturated ester is saturated in a pre-reactor before being
vaporised into the hydrogen-containing stream and then subjected to
the hydrogenolysis reaction.
[0025] One alternative process has been described in WO2011/017543.
In this process, the dialkyl succinate is formed from co-products
or residues obtained from maleic anhydride manufacture rather than
from the maleic ester. The process comprises: (a) providing a
mixture comprising about 30 to 90 wt % maleic anhydride and about 5
to 68 wt % fumaric acid; (b) contacting the mixture of (a) with an
alkyl alcohol solvent in a sufficient amount to form a solution and
holding the solution at a temperature of from 20.degree. C. to
about 250.degree. C. for a holding time; (c) hydrogenating the
solution of (b), in the absence of an intermediate distillation
between (b) and (c), at hydrogenation conditions of temperature of
about 50.degree. C. to 200.degree. C. under hydrogen pressure from
about 50 to 1000 psig (about 450 to 7000 kPa) in the presence of a
hydrogenation catalyst to form a hydrogenation product; (d)
treating the hydrogenation product with alcohol at an
esterification temperature of about 100.degree. C. to 140.degree.
C. to form crude product containing dialkyl esters, wherein at
least 85% of maleic anhydride, fumaric acid and their derivatives
of (a) have been converted to dialkyl esters in the crude product;
and (e) isolating dialkyl esters from the crude product of (d).
[0026] Whilst these various processes offer means for obtaining the
desired products, they each suffer from various disadvantages and
drawbacks.
[0027] In many of the known processes, a copper based catalyst may
be used for the hydrogenation reaction. However, acidic species
will deactivate these catalysts necessitating regular shut down to
replace deactivated catalyst. This deactivation may be exacerbated
by the high heat release on the conversion of the double bond in
the hydrogenation step.
[0028] A further problem is that it can be difficult to separate by
distillation the acidic species in processes utilising dialkyl
maleates. This is due to the reversion of the diester to the maleic
anhydride which yields close boiling compounds. To address this
problem, high conversion of the acidic species to diesters in the
reaction system before vaporisation is required. This increases the
physical size of the reaction column required to achieve the
necessary high conversion.
[0029] A particular problem relates to the formation of insoluble
fumarates in the alkyl maleate system. To attempt to minimise
fumarate formation, it is necessary to restrict the temperature of
the esterification reaction. The lower temperature means that a
catalyst has to be used.
[0030] In addition, the requirement for high conversion of the
mono-alkyl maleate to the di-alkyl maleate requires a large excess
of dry methanol to complete the reaction. This has the disadvantage
of requiring a high energy input and equipment costs to recover dry
methanol by distillation such that it can be recycled.
[0031] A still further problem associated with the conventional
reaction processes is that by-products may be formed by reaction
across the double bond. By-products conventionally formed include
hydroxyl dialkyl succinate.
[0032] An additional problem with these prior art processes is that
dialkyl maleates, such as dimethyl maleate) vaporised in hydrogen,
is less volatile than the corresponding succinate and thus more
hydrogen is required to vaporise the feed which increases the size
of the equipment required for the hydrogenation step.
[0033] Whilst utilising aqueous maleic acid as feed might be
considered desirable as addressing some of the above problems, it
would be necessary to remove any water present. However, this
removal process may lead to the formation of fumaric acid with its
attendant problems and hence require the use of more expensive
equipment and a high energy cost to dehydrate aqueous maleic acid
to dry feed maleic anhydride for the esterification reaction.
[0034] Where the process includes a recycle, 1,4-butanediol, and/or
.gamma.-butyrolactone may be present in the recycle stream. These
compounds can react with the dialkyl maleate to form long chain
oligomers. These can grow in the vaporiser and at the inlet to the
catalyst bed to form a "polymer". The presence of the polymer may
result in the need to shut down the hydrogenation reactor
prematurely to remove the polymer. Polymers may also be formed by
cross linking of the double bonds in the maleates.
[0035] Where a process requires the hydrogenation of maleic acid to
succinic acid prior to esterification, the presence of the acid
species can lead to deactivation of the catalyst. In addition they
will cause corrosion problems unless high grade expensive materials
are used for the construction of the reactors. Additionally or
alternatively the temperature at which the reactor is operated may
have to be limited. Further, carrying out hydrogenation of maleic
acid to succinic acid may result in operating problems due to the
insolubility and high freezing points of the components.
[0036] It is therefore desirable to provide an alternative process
which addresses at least one of these problems.
[0037] It has now been found that by carrying out the
pre-saturation of the double bond prior to the esterification but
in the same reactor, the heat generated by the saturation will
allow the esterification reaction to occur without the need for a
catalyst. That is to say that the esterification reaction is
auto-catalysed.
[0038] Thus according to a first aspect of the present invention
there is provided a process for the production of dialkyl succinate
from a feedstock comprising maleic anhydride, said process
comprising the steps of: [0039] (a) providing the feed in the
liquid phase to a reactor operated at a temperature of at least
about 150.degree. C.; [0040] (b) contacting said feed with hydrogen
at a pressure of at least about 300 psig in the presence of an acid
tolerant catalyst and an alkanol wherein at least some of the
carbon carbon double bonds of the maleic anhydride are hydrogenated
to form succinic acid and that the heat generated promotes
esterification to dialkyl succinate in situ; and [0041] (c)
recovering a stream comprising dialkyl succinate from the
reactor.
[0042] Thus the heat generated by the hydrogenation of the double
bond can be utilised to promote the esterification reaction. In one
arrangement, the heat generated may be sufficient to enable the
esterification reaction to be carried out in the absence of a
catalyst and hence the problems associated with the life expectancy
of the esterification catalyst in prior art processes are obviated.
In one alternative arrangement, an esterification catalyst may be
used. In a further alternative arrangement, a combined catalyst may
be used.
[0043] For the avoidance of doubt, the esterification part of the
reaction is carried out in the same reactor as the hydrogenation of
the double bond. Whilst cooling may be provided in the reactor to
control the exotherm, this is not generally preferred and the
temperature will be maintained at least about 150.degree. C. The
heat generated during the hydrogenation may advantageously drive
off the water from the product succinate. This will be assisted
where the alkanol is methanol and is present in excess.
[0044] Generally any unesterified anhydride or acid species
remaining in the stream recovered at step (c) will be in the
saturated form and so will be succinic anhydride or succinic
acid.
[0045] It should be noted that some monoesterification of the
maleic acid or anhydride may occur within the reaction vessel prior
to the saturation reaction occurring without departing from the
scope of the present invention.
[0046] The present invention offers significant advantages over the
various prior art processes. For example, any acidic monoalkyl
succinate, such as monomethyl succinate, and any succinic acid
remaining in the stream recovered in step (c) are easier to
separate from the dialkl succinate, such as dimethyl succinate,
than the separation of the corresponding maleic/maleate species. In
one arrangement of the present invention, a bottom liquid stream
from the separator may be recycled to the
hydrogenation/esterification reactor. The size of the reaction
column is therefore greatly reduced. This in turn will reduce the
capital and operating costs.
[0047] In some arrangements, a polishing esterification reaction
may additionally be required to esterify any remaining succinic
acid or any monoalkyl succinic acid in stream recovered in step (c)
but this will generally be of a smaller size than has been required
heretofore.
[0048] The saturation of the double bond prior to esterification
reduces the likelihood of by-products such as alkoxy dialkyl
succinate and hydroxyl dialkyl succinate forming in the
esterification reaction and thus an overall yield improvement will
generally be noted. In addition, the saturation of the carbon
carbon double bond reduces the risk of isomerisation to the
fumarate occurring.
[0049] The present invention enables the reaction to operate at a
lower conversion rate. This enables a lower quantity of alkanol to
be used than is required in conventional processes. In conventional
processes, the conversion is typically at least 99%. The present
invention can be operated at as low as 50% conversion but it will
preferably be operated at about 80 to 90% conversion to the dialkly
succinate.
[0050] In addition, alkanol having a higher water content than has
been usable heretofore may be used. In conventional processes
essentially dry alkanol is required. Thus where methanol is used,
it will conventionally be required to have a water content of less
than 0.05 wt %. In the process of the present invention where
methanol is the alkanol a higher water content of about 1 to about
2% or even higher may be used. The feed to the reactor will
generally comprise at least 90% maleic anhydride. In one
arrangement, a feed comprising 92 to 95% maleic anhydride may be
used. In an alternate arrangement, a feed comprising 97, 98, 99,
99.5, 99.8 or 100% maleic anhydride may be used.
[0051] Any suitable alkanol may be used. Generally a C.sub.1 to
C.sub.4 alkanol will be used with methanol or ethanol being
particularly preferred.
[0052] The saturation reaction may be carried out at any suitable
temperature provided that it is at least 150.degree. C. In one
arrangement, a temperature in the range of from about 150.degree.
C. to about 240.degree. C. may be used although higher temperatures
may also be used. Other suitable temperatures include those of
155.degree. C., 160.degree. C., 170.degree. C., 180.degree. C.,
190.degree. C., 200.degree. C., 210.degree. C., 220.degree. C. and
230.degree. C. As there is no possibility of insoluble fumarates
being formed, higher temperatures can be utilised than is
conventional. This will enable a reduced size of reactor to be used
which in turn will reduce the associated costs.
[0053] Any suitable pressure may be used provided that the alkanol
is kept in liquid phase at the high temperatures generated by the
exotherm of the hydrogenation reaction. In one arrangement, a
hydrogen pressure of about 300 psig to about 900 psig will be used.
Suitable hydrogen pressures include 400 psig, 500 psig, 600 psig,
700 psig and 800 psig.
[0054] Any suitable catalyst may be used for the hydrogenation
reaction. In one arrangement a heterogeneous catalyst may be used.
Palladium catalysts may offer some advantages. The catalyst may be
provided on a suitable support. In one arrangement, a palladium on
carbon catalyst may be used. Other suitable catalysts include
supported palladium. Where a combined catalyst is used for the
hydrogenation and the esterification, any suitable catalyst such as
palladium supported on alumina.
[0055] Any suitable flow through rate may be used. In one
arrangement a residence time of about 10 to about 60 minutes will
be suitable.
[0056] The product diester succinate, such as dimethyl succinate,
has a lower vapour pressure than the corresponding maleate, and
this, together with the fact that the heat generated is used in the
esterification reaction thereby managing the exotherm across the
hydrogenation bed means that the throughput of feed to the
hydrogenation bed can be increased. In one arrangement, this can be
achieved in the manner described in WO 2005/058855 which is
incorporated herein by reference.
[0057] In addition, the hydrogenation of aqueous maleic acid to
succinic acid prior to esterification eliminates the need to remove
the water in the generation of maleic anhydride. Without the need
to control the temperature or the problems associated with
insoluble fumarates formation that are associated with the maleate
system, the reaction can be operated at temperatures leaving a
molten stream of succinic acid.
[0058] Any monoalkyl succinate formed in the reaction may be
recycled to the reactor. In one arrangement, the monoalkyl
succinate may be recovered with the dialkyl succinate and will then
be separated before being recycled. In an alternate arrangement,
the reaction, separation of monoalkyl succinate and recycle to the
reaction may be carried out in the same vessel.
[0059] The present invention will now be described by way of
example with reference to the accompanying drawings in which:
[0060] FIG. 1 is a schematic illustration of a flow sheet according
to the present invention
[0061] It will be understood by those skilled in the art that the
drawings are diagrammatic and that further items of equipment such
as reflux drums, pumps, vacuum pumps, temperature sensors, pressure
sensors, pressure relief valves, control valves, flow controllers,
level controllers, holding tanks, storage tanks, and the like may
be required in a commercial plant. The provision of such ancillary
items of equipment forms no part of the present invention and is in
accordance with conventional chemical engineering practice.
[0062] The invention will be discussed with reference to the
methylation of maleic anhydride. However, it is equally applicable
to the use of other alkanols.
[0063] Maleic anhydride is fed in line 1 to the reactor 2
containing a hydrogenation catalyst and operating under
hydrogenation conditions. Hydrogen is fed to the reactor 2 in line
3. An alkanol, such as methanol, is added in line 4. This may be
fresh methanol or may be methanol recovered from downstream in the
reaction. A product stream comprising dimethyl succinate will be
removed in line 5. The stream may also include monomethyl
succinate. The product stream may be passed in line 5 is passed to
an ester separator 10. The dimethyl succinate is removed in line 11
as a liquid or a vapour product. It may then be passed to a
hydrogenolysis reactor (not shown) where tetrahydrofuran, and/or
1,4-butanediol and/or .gamma.-butyrolactone may be produced.
Hydrogen may be supplied in line 12 to the separator 10 to assist
in the separation. The monomethyl succinate may be returned in line
13 to the reactor 2.
[0064] Methanol and water are removed from the reactor 2 in line 6.
It is passed to a methanol/water separator 7. The water is removed
in line 8 and the methanol is recycled in line 9 where it is
returned to line 4. Methanol from the subsequent hydrogenolysis
reaction may be returned in line 14 to the reactor 2.
[0065] Any suitable reactor may be used for the reactor in which
the hydrogenation/esterification reaction occurs. Suitable reactors
include continuous stirred tank type reactors, or a fixed bed
reactor with a liquid recycle. The reactor may optionally have
internal or external cooling. A separate additional reaction column
may be installed downstream to complete the esterification reaction
which does not occur in the main reactor.
EXAMPLE 1
[0066] Maleic anhydride and 3 mol equivalents of methanol and a
palladium on carbon catalyst were placed in an autoclave at 500
psig hydrogen and 190.degree. C. The product analysis gave:
TABLE-US-00001 Methanol 17.12 wt % Maleic anhydride 0.51 wt %
Dimethyl maleate 2.93 wt % Dimethyl succinate 55.06 wt % Methoxy
dimethyl succinate 0.03 wt % Monomethyl maleate 0.13 wt %
Monomethyl succinate 16.31 wt % Maleic acid 1.24 wt % Fumaric acid
0.10 wt % Water 6.52 wt %
EXAMPLES 2 AND 3
[0067] Unless otherwise stated, all testwork was performed using a
300 ml autoclave. Hydrogen was used as the gas to generate
pressure. Water was analysed using a Karl Fischer Aquapal. GC
analysis was by FID using Regisil to allow for acids analysis.
EXAMPLE 2
Autocatalytic Esterification Stage 1
[0068] To the autoclave was charged succinic acid (40 g, 0.34 mol)
and methanol (21.7 g, 0.68 mol, 2 eqv). The vessel was pressurised
to 500 psig and heated to 190.degree. C. 1 hour then cooled and
discharged. The product was analysed by dissolving 50 mg of the
sample in Regisil (500 mg) and acetonitrile (250 mg) then analysed
using FID GC.
[0069] Using the previously described Regisil method the light
components (methanol and water) were removed by crude flash
distillation at 150.degree. C. under ambient pressure.
EXAMPLE 3
[0070] 50 g, 0.5 mol maleic anhydride, 49 g, 1.53 mol, 3 eqv
methanol, 1 g, equivalent to 0.32 g, 0.6 wt % palladium-carbon
paste were charged to the autoclave. The vessel was sealed and then
pressurised to 300 psig with hydrogen and heated to 190.degree. C.
The internal temperature of the vessel was recorded with time and,
to ensure that any exotherm above the desired maximum temperature
was monitored, the cooling system was turned off.
[0071] The results indicated that, although the rate of temperature
increase did go up, the temperature did not exceed the maximum
operating parameter. Analysis of the product showed significant
conversion of the maleate species to succinate with (methanol free)
selectivity to mono methyl maleate and mono maleate succinate of
7.28 mol % and 11.08 mol % respectively. Selectivity to di-methyl
maleate and dimethyl succinate were 3.59 mol % and 26.41 mol %
respectively.
[0072] The results are set out in the following table.
TABLE-US-00002 Run Number 1208-04 Temperature, .degree. C. 190 RT
at 190.degree. C., min 10 GC Analysis, wt % MeOH 24.87 MAH 0.38 DMM
4.41 DMF 3.70 DMS 32.90 DMC 0.04 MeODMS 0.06 MMM 8.07 MMS 12.48 MMF
4.48 MMC 0.20 HO-DMS 0.02 MAC 0.47 SAC 0.88 FAC 0.44 Water 6.47
* * * * *