Process for the production of dimethyl succinate and 1,4 butanediol

Abstract

A process for the production of dimethyl succinate and 1, 4 butanediol is disclosed. The process comprises a 1, 4 butanediol production process comprising a first esterification section and a hydrogenolysis section and a dimethyl succinate production process comprising a second esterification section and a hydrogenation section. The process is characterised in that at least one stream is taken from the dimethyl succinate production process and fed to the 1, 4 butanediol production process.

Description

[0001] Process for the production of dimethyl succinate and 1,4 butanediol

[0002] Field of the Invention

[0003] The present invention relates to a process for the production of dimethyl succinate and 1,4 butanediol.

[0004] Background

[0005] Dimethyl succinate and 1,4 butanediol are used in the production of poly butyl succinate (PBS) . PBS is a commercially important biodegradable plastic. Biodegradable plastics have a role to play in increasing the sustainability of plastic goods. Improving the sustainability of their production will help with this. That may involve, for example, reducing energy consumption or making more efficient use of feedstocks in the production process.

[0006] 1,4 butanediol is already produced in large quantities, for example using technology available from Johnson Matthey Davy to convert maleic anhydride through esterification to dimethyl maleate and then through hydrogenolysis to a combination of 1,4 butanediol, gamma-butyrolactone (GBL) and tetrahydrofuran (THF) . By using appropriate catalysts and controlling the reaction conditions appropriately in the hydrogenolysis, the relative quantities of 1,4 butanediol, GBL and THF can be altered to suit the desired product mix. For example, for PBS production it may be desirable to maximise the 1,4 butanediol product flow and minimise the GBL and THF product flows.

[0007] Examples of such 1,4 butanediol, GBL and THF production processes are disclosed in W088 / 00937 and W091 / 01960. It has also been suggested that dimethyl succinate can be produced from maleic anhydride . The maleic anhydride can be esteri fied to dimethyl maleate and then hydrogenated to dimethyl succinate . Examples of such processes are disclosed in CN102070448 and CN110563933 .

[0008] The applicant has previously suggested that 1 , 4 butanediol and dimethyl succinate production be co-located to minimise capital and operational expenditure . However, there remains a need to provide co-located processes that improve the sustainability of the production of 1 , 4 butanediol and dimethyl succinate .

[0009] Preferred embodiments of the present invention seek to overcome one or more of the above disadvantages of the prior art .

[0010] Summary of Invention

[0011] According to a first aspect of the invention, there is provided process for the production of dimethyl succinate and 1 , 4 butanediol , the process comprising a 1 , 4 butanediol production process comprising a first esteri fication section and a hydrogenolysis section and a dimethyl succinate production process comprising a second esteri fication section and a hydrogenation section, characterised in that at least one stream is taken from the dimethyl succinate production process and fed to the 1 , 4 butanediol production process .

[0012] Integrating the 1 , 4 butanediol and dimethyl succinate production processes in this way may be advantageous because many components that are considered waste or contaminants in the dimethyl succinate production process can be usefully used in the 1 , 4 butanediol production process . By feeding a stream from the dimethyl succinate production process to the 1 , 4 butanediol production process , any contaminants or waste in that stream may be converted into useful products instead of being lost i f they were simply purged from the dimethyl succinate production process . Moreover, the sharing of streams in this way may facilitate the sharing of equipment items such as compressors i f a stream is compressed for use in the dimethyl succinate production process and then used in a lower pressure part of the 1 , 4 butanediol production process . Examples of streams that can be shared include heavies and lights that are separated from dimethyl succinate product in a puri fication section of the dimethyl succinate production process . It may for example be advantageous for some dimethyl succinate to be slipped in the heavies and lights . As examples , doing so may facilitate the obtaining of suf ficiently high dimethyl succinate purity in the dimethyl succinate product , reduce column duties or allow a column to operate at a pressure at which available steam or cooling water streams can be used respectively in reboilers or condensers . Sending such streams to the 1 , 4 butanediol production process allows that dimethyl succinate to be converted into 1 , 4 butanediol in the 1 , 4 butanediol production process and so the feedstock ef ficiency is improved, and a more sustainable overall process is obtained . Wash and start-up streams in the dimethyl succinate production process may also contain dimethyl succinate that , while not present in suf ficient quantities to be economically recovered as dimethyl succinate product , can, i f the stream is fed to the 1 , 4 butanediol production process , be converted into useful 1 , 4 butanediol product . The 1 , 4 butanediol production process can typically tolerate any contaminants that are in such streams , or will in any case be removing those contaminants present from other sources . Contaminants that are di f ficult to separate from dimethyl succinate may be more readily separable from 1 , 4 butanediol and therefore be tolerable in the 1 , 4 butanediol production process . The feeding of streams from the dimethyl succinate production process to the 1 , 4 butanediol production process therefore advantageously leads to the conversion of components in those streams to useful products without creating signi ficant additional separation requirements in the 1 , 4 butanediol production process . The result is advantageously greater overall feedstock ef ficiency and even reduced overall capital and operating expenditure through the removal of duplicate equipment .

[0013] A particularly preferred stream to pass from the dimethyl succinate production process to the 1 , 4 butanediol production process is a hydrogen stream . Both the hydrogenolys is section of the 1 , 4 butanediol production process and the hydrogenation section of the dimethyl succinate production process require a hydrogen feed . Typically, a large stoichiometric excess of hydrogen is needed in the reactor to drive conversion . In a liquid phase hydrogenation, an excess of hydrogen may also advantageously prevent di f ferences in distribution of the vapour and liquid phases from l imiting overall conversion . In prior art processes this typically involves the use of a recycle loop that recycles hydrogen back through the reactors . Such recycle loops require a purge to prevent the build-up of inert contaminants over time and there is inevitably useful material that is also lost in the purge .

[0014] The applicant has appreciated that , instead of purging hydrogen from the dimethyl succinate production process to waste , it can be sent to the 1 , 4 butanediol production process . Thus , a hydrogen stream is preferably taken from the hydrogenation section and fed to the hydrogenolysis section . For example , there may be provided a process for the production of dimethyl succinate and 1 , 4 butanediol , the process comprising a 1 , 4 butanediol production process comprising a hydrogenolysis section and a dimethyl succinate production process comprising a hydrogenation section, characterised in that a hydrogen stream is taken from the dimethyl succinate production process and fed to the 1 , 4 butanediol production process . The 1 , 4 butanediol production process typically also comprises a first esteri fication section and the dimethyl succinate production process typically also comprises a second esteri fication section . The hydrogen stream may be a hydrogen purge stream from a hydrogen recycle loop in the dimethyl succinate production process . However, a particularly advantageous arrangement may be achieved where an excess of hydrogen is fed to the hydrogenation section of the dimethyl succinate production process , where it passes through the hydrogenation reactor or reactors in a once-through configuration, i . e . , without a recycle . Thus , the hydrogenation section preferably does not comprise a hydrogen recycle . Instead, the excess hydrogen that has not been reacted in the dimethyl succinate hydrogenation is sent to the 1 , 4 butanediol production process hydrogenolysis section . Such an arrangement removes the need for a recycle and purge in the dimethyl succinate production process , thus saving a number of equipment items , while still maintaining a signi ficant excess of hydrogen in the dimethyl succinate production process hydrogenation section . The excess hydrogen is not wasted, because it is fed to the hydrogenolysis section and consumed there . By using a recycle to generate the desired excess of hydrogen in the hydrogenolysis section, the overall hydrogen consumption of the process is minimised and improved feedstock ef f iciency is obtained . Thus , the hydrogenolysis section preferably comprises a hydrogen recycle . Make-up hydrogen is advantageously also fed to the hydrogenolysis section in addition to the hydrogen stream . That may advantageously allow the optimum excess amount of hydrogen to be used in both the hydrogenation section and the hydrogenolys is section . Such an arrangement may be particularly advantageous where the hydrogenation section is a liquid phase hydrogenation and the hydrogenolysis is a vapour phase hydrogenolysis . In such circumstances the hydrogenation can operate without a recycle , with excess hydrogen flowing from the hydrogenation to the hydrogenolysis , and the hydrogenolysis can operate with a recycle and suf ficient excess hydrogen to vaporise the dimethyl maleate feed to the hydrogenolysis .

[0015] In some embodiments , fresh hydrogen may be fed along with the hydrogen stream . The fresh hydrogen may be the source of make-up hydrogen for the hydrogenolysis , but in some embodiments it may be both the make-up hydrogen for the hydrogenolysis and the source of hydrogen for the hydrogenation . In such embodiments , there is a recycle on both the hydrogenation and the hydrogenolysis and the recycle has a common section, which will typically comprise a common recycle compressor . The hydrogen stream is fed from the hydrogenation to the hydrogenolysis via the common section . Advantageously, in this way, the need for a purge in the hydrogenation recycle loop may still avoided because -1- contaminants can pass into the hydrogenolysis recycle loop and be handled in that loop .

[0016] In some embodiments the dimethyl succinate production process comprises a dimethyl succinate puri fication section downstream of the hydrogenation section and heavies removed in the dimethyl succinate puri fication section are fed to the

[0017] 1 , 4 butanediol production process . Preferably the heavies are fed to the first esteri fication section . For example , there may be provided a process for the production of dimethyl succinate and 1 , 4 butanediol , the process comprising a 1 , 4 butanediol production process comprising a first esteri fication section and a hydrogenolysis section and a dimethyl succinate production process comprising a second esteri fication section, a hydrogenation section and a dimethyl succinate puri fication section downstream of the hydrogenation section, characterised in that heavies removed in the dimethyl succinate puri fication section are fed to the

[0018] 1 , 4 butanediol production process , preferably to the first esteri fication section .

[0019] The skilled person will understand the term "heavies", which is commonly used in the art to refer to a stream comprising contaminants that have a higher boiling point than the desired product . Heavies are typically recovered from at or near the bottom of distillation columns , with the desired product being withdrawn higher up the column than the heavies . A puri fication section may comprise multiple distillation columns , and there may be more than one heavies stream removed, any or all of which may then be fed to the

[0020] 1 , 4 butanediol production process . In the dimethyl succinate production process , the heavies typically comprise monomethyl succinate . Advantageously, the heavies preferably also comprise dimethyl succinate . That is because advantageously some of the dimethyl succinate is slipped in the heavies to reduce column separation duty while achieving dimethyl succinate product purity and also to lower the process temperature in the column reboiler . Monomethyl succinate and dimethyl succinate in the heavies represent a loss of feedstock from the dimethyl succinate production process , but by feeding the heavies to the 1 , 4 butanediol production process monomethyl succinate and / or dimethyl succinate in the heavies may be converted to useful products . For example , in the first esteri fication section the monomethyl succinate may be converted to dimethyl succinate and subsequently converted to products in the hydrogenolysis section . Dimethyl succinate may be converted to useful products in the hydrogenolysis section . A greater feedstock ef ficiency may therefore be achieved . Additionally, the dimethyl succinate puri fication section may be built or operated at lower cost by allowing more dimethyl succinate slip in the heavies in order to achieve suf ficient dimethyl succinate product quality, because that slipped dimethyl succinate is not being lost but instead being converted to useful products in the 1 , 4 butanediol production process . Moreover, because the heavies are being sent to the 1 , 4 butanediol production process , instead of back upstream in the dimethyl succinate production process , there is no recycle loop created in which contaminants , such as methoxy dimethyl succinate , may build up and therefore no need for a heavy purge from the dimethyl succinate production process . Instead, all heavy contaminants are concentrated into heavy streams removed from the 1 , 4 butanediol production process , from which a purge may be taken to prevent build up that is more ef ficient than having heavy purges on both the 1 , 4 butanediol and dimethyl succinate production processes . For example , contaminant such as methoxy dimethyl succinate may be converted in the hydrogenolysis section to components that are more easily separated from the product 1 , 4-butanediol , and other contaminants , such as dibutyl maleate , may be converted into products in the 1 , 4-butanediol process , both of which advantageously increase the feedstock ef ficiency of the purging of heavies from the overall process .

[0021] It may be particularly preferable to feed the heavies to the first esteri fication section . The heavies could, for example , be fed to the hydrogenolysis section and an advantageous improvement in feedstock ef ficiency may achieved . However, doing so may increase the acid content of the 1 , 4 butanediol production process , which may have a detrimental ef fect on the li fetime of catalysts in that process . Feeding the heavies to the first esteri fication section may allow the acid content to be maintained at an acceptable level . Preferably the first esteri fication section comprises a first esteri fication reaction column, for example as described in US5536856 , US2002 / 026070 or US4032458 , and the heavies are fed to the first esteri fication reaction column . Since the first esteri fication reaction column may be operated to control the acid content in an esteri fication product stream recovered from the first esteri fication reaction column, feeding the heavies to the first esteri fication reaction column not only advantageously allows the conversion of monomethyl succinate in the heavies to dimethyl succinate for later conversion to useful products in the hydrogenolysis section, but also means the operation of the first esteri fication reaction column controls the removal of acid contaminants and prevents the feeding of the heavies from increasing the acid content as might happen i f the heavies were fed downstream of the first esteri fication reaction column .

[0022] In some embodiments the dimethyl succinate production process comprises a dimethyl succinate puri fication section downstream of the hydrogenation section and lights removed in the dimethyl succinate puri fication section are fed to the 1 , 4 butanediol production process . For example , there may be provided a process for the production of dimethyl succinate and 1 , 4 butanediol , the process comprising a 1 , 4 butanediol production process comprising a hydrogenolysis section and a dimethyl succinate production process comprising a hydrogenation section and a dimethyl succinate puri fication section downstream of the hydrogenation section, characterised in that lights removed in the dimethyl succinate puri fication section are fed to the 1 , 4 butanediol production process . The 1 , 4 butanediol production process typically also comprises a first esteri fication section and the dimethyl succinate production process typically also comprises a second esteri fication section .

[0023] The skilled person will understand the term " lights" , which is a commonly used term in the art to describe a stream comprising contaminants that have a lower boiling point than a desired product . Lights are typically recovered from at or near the top of distillation columns , with the desired product being withdrawn lower down the column than the lights . A puri fication section may comprise multiple distillation columns , and there may be more than one lights stream removed, any or all of which may then be fed to the 1 , 4 butanediol production process . In the dimethyl succinate production process , the lights typically comprise methanol . The lights typically also comprise dimethyl succinate . That is because separation in a column is not clean-cut and, in order to economically achieve a desired level of product purity, some of the desired product is slipped in the lights so as to ensure that only a low level of light contaminants is present in the product stream .

[0024] In some embodiments the lights are fed to the hydrogenolysis section . In that way, dimethyl succinate in the lights may be converted to useful product in the hydrogenolysis section, thus improving feedstock ef ficiency . Also , because the lights are not representing a direct loss from the overall process , even though they are removed from the dimethyl succinate production process , the puri fication section may be built or operated at lower cost by allowing more dimethyl succinate to slip in the lights in order to achieve a desirable level of dimethyl succinate product quality . The slipped dimethyl succinate is not lost but is instead converted to useful products in the 1 , 4 butanediol production process . Preferably the 1 , 4 butanediol production process comprises a recycle loop and the lights are fed to the recycle loop . Such an arrangement may be particularly beneficial when the lights also comprise methanol . The 1 , 4 butanediol production process preferably further comprises a product refining section downstream of the hydrogenolysis section . The recycle loop may extend across the first esteri fication section, the hydrogenolysis section and the product refining section . For example , unreacted dimethyl succinate and methanol may exit the hydrogenolysis section along with the 1 , 4 butanediol and enter the product refining section . In the product refining section, the methanol may be separated and recycled to the first esteri fication section and a stream comprising the unreacted dimethyl succinate may be separated and recycled to the hydrogenolysis section . Together, these recycles may make the recycle loop . I f the lights from the dimethyl succinate production process are fed to the recycle loop, most preferably to the product refining section, methanol in the lights can be recycled to the first esteri fication section and dimethyl succinate in the lights can be recycled to the hydrogenolysis . In that way, the useful components in the lights are sent ef ficiently to the parts of the 1 , 4 butanediol production process in which they can be used, using existing separations in the 1 , 4 butanediol production process . In preferred embodiments therefore the 1 , 4 butanediol production process preferably further comprises a product refining section downstream of the hydrogenolysis section and the lights are fed to the product refining section . Preferably methanol is recycled to the first esteri fication section from the product refining section and the lights comprise methanol . Preferably dimethyl succinate is recycled to the hydrogenolysis section from the product refining section and the lights comprise dimethyl succinate . Most preferably, methanol is recycled to the first esteri fication section from the product refining section and dimethyl succinate is recycled to the hydrogenolysi s section from the product refining section and the lights comprise methanol and dimethyl succinate . In some embodiments the lights are fed to the first esteri fication section . In that way, methanol in the lights can react in the first esteri fication section and dimethyl succinate in the lights can pass through the first esteri fication section and react in the hydrogenolysis section . Thus , the components are also efficiently used in this embodiment . In some embodiments a wash stream is taken from the dimethyl succinate production process and fed to the 1 , 4 butanediol production process . The dimethyl succinate production process typically comprises one or more resin beds that require periodic washing . For example , the dimethyl succinate production process may comprise one or more sul fur removal resins upstream of the hydrogenation section . The wash stream is thus preferably a stream generated in the washing of one or more resins in the dimethyl succinate production process , and most preferably in the washing of a sul fur removal resin upstream of the hydrogenation section . The wash fluids are advantageously fluids that are compatible with the dimethyl succinate production process and such fluids can al so be chosen to be useful in the 1 , 4 butanediol production process . Advantageously, the contaminants removed in the washes are also tolerable in the 1 , 4 butanediol production process . Thus , while the wash fluids could not be passed through the dimethyl succinate production process , they can be passed to the 1 , 4 butanediol production process where components in the wash fluid can be converted to useful product . For example , in some embodiments , the wash stream comprises dimethyl succinate and is fed to the hydrogenolysis section . In some embodiments the 1 , 4 butanediol production process further comprises a product refining section downstream of the hydrogenolysis section, wherein methanol is recycled to the first esteri fication section from the product refining section, and the wash stream comprises methanol and is fed to the product refining section . As explained above , dimethyl succinate and / or methanol can be fed to appropriate locations in the 1 , 4 butanediol production process so that they are efficiently processed using existing separations and reactions in the 1 , 4 butanediol production process . In some embodiments the wash stream comprises water. Processing wash fluids in this way advantageously increases the overall efficiency and sustainability of the process.

[0025] In some embodiments a start-up stream produced during startup of the dimethyl succinate production process is fed to the 1,4 butanediol production process. During start-up, streams may be generated that cannot be process on through the dimethyl succinate production process. However, those streams advantageously comprise components that are reactants in the 1,4 butanediol production process and can thus be converted to useful products when fed to the 1,4 butanediol production process. Processing start-up streams in this way advantageously increases the overall efficiency and sustainability of the process.

[0026] Preferably the first and second esterification sections share one or more equipment items. A typical esterification section comprises a reaction column, for example as described in US5536856, US2002 / 026070 or US4032458. Such a reaction column typically comprises a plurality of stages containing a catalyst. Typically, there is a first reaction zone in which a monoester, such as monomethyl maleate, is formed. The monoester is then fed to the column and the esterification of monoester to a diester, such as dimethyl maleate, takes place across the column stages. The column also acts to separate products and by-products, which helps drive that esterification reaction. For a small plant, there may be a single first reaction zone and single reaction column for both the 1,4 butanediol production process and the dimethyl succinate production process. In other words, the first esterification section may be the second esterification section. However, for larger plants it will be more usual to have two or more reaction columns and thus one reaction column may be in use for the 1,4 butanediol production process and another in use for the dimethyl succinate production process. While in such cases the first esterification section has a different reaction column to the second esterification section, there may still be other equipment that is shared between the first and second esterification sections. For example, the first reaction zone, in which the monoester is formed may be shared between the first esterification section and the second esterification section. As another example, a shared loading system for loading catalyst into the reaction columns may be provided for use in both the first and second esterification sections. As another example, a shared distillation column used to separate excess methanol from water stripped from the reaction columns may be provided for use in both the first and second esterification sections. Such shared equipment items advantageously save on overall capital cost.

[0027] A further possibility for equipment sharing preferably involves using the, preferably shared, reaction column loading system to wash a purification resin in the dimethyl succinate production process. For example, the purification resin may be one or more sulfur removal resins upstream of the hydrogenation section. This use of the reaction column loading system advantageously saves on overall capital cost. The wash stream may be sent to the 1,4 butanediol production process as described above.

[0028] Further elements may advantageously be shared between the 1,4 butanediol production process and the dimethyl succinate production process. For example, one or more of utility headers and flare system, vacuum package, plot area, Distributed Control System, control room and operators may be shared between the 1,4 butanediol production process and the dimethyl succinate production process, advantageously saving on capital and / or operating cost.

[0029] Preferably maleic anhydride is esterified with methanol to dimethyl maleate in the first esterification section and in the second esterification section. Preferably the maleic anhydride is esterified, preferably autocatalytically, to monomethyl maleate in a first reaction zone within the first esterification section, and a further first reaction zone, which may be the same or a different first reaction zone, within the second esterification section. Monomethyl maleate so produced is then preferably esterified to dimethyl maleate in a reaction column within the first esterification section and a further reaction column, which may be the same reaction column but is preferably a different reaction column, within the second esterification section. Maleic anhydride may advantageously be readily available as a cost-effective feed to the process. In the hydrogenolysis section the dimethyl maleate is converted with hydrogen to 1,4 butanediol. This occurs by saturation of the dimethyl maleate to dimethyl succinate and hydrogenolysis of the dimethyl succinate to 1, 4 butanediol, both reaction steps occurring in the hydrogenolysis section. In the hydrogenation section, dimethyl maleate is hydrogenated with hydrogen to dimethyl succinate .

[0030] The invention advantageously improves feedstock efficiency by taking a stream that would be purged or otherwise discarded from the dimethyl succinate production process and feeding it to the 1,4 butanediol production process where components in the stream can be converted to useful products. The stream preferably therefore comprises one or more reactants or intermediates of the 1,4 butanediol production process. For example, the reactants in the 1,4 butanediol production process may include maleic anhydride, methanol and hydrogen and the intermediates in the 1,4 butanediol production process may include monomethyl maleate, dimethyl maleate, dimethyl succinate and monomethyl succinate. The stream taken from the dimethyl succinate production process and fed to the 1,4 butanediol production process preferably comprises one or more of maleic anhydride, methanol, hydrogen, monomethyl maleate, dimethyl maleate, monomethyl succinate and dimethyl succinate. In some embodiments, the stream taken from the dimethyl succinate production process and fed to the 1,4 butanediol production process preferably comprises one or more of methanol, hydrogen, monomethyl maleate, dimethyl maleate, monomethyl succinate and dimethyl succinate. In preferable embodiments, the stream taken from the dimethyl succinate production process and fed to the 1,4 butanediol production process preferably comprises one or more of methanol, hydrogen, dimethyl maleate and dimethyl succinate. In more preferable embodiments, the stream taken from the dimethyl succinate production process and fed to the 1,4 butanediol production process preferably comprises one or more of hydrogen, dimethyl maleate and dimethyl succinate. Those components may for example particularly be present in streams taken from in, or downstream of, the hydrogenation and may be readily reacted in the 1,4 butanediol production process to form useful 1,4 butanediol product. Being able to use those components in the 1,4 butanediol production process may allow more of those components to be present in the stream taken from the dimethyl succinate production process than would be economical if the stream was simply going to waste , thus allowing the dimethyl succinate production process to run more ef ficiently to produce high quality dimethyl succinate product . An example is that more dimethyl succinate may be slipped into a lights or heavies stream, thus providing more economical recovery of the dimethyl succinate product stream at suf ficient purity, because that dimethyl succinate is not being wasted but will instead be converted to 1 , 4 butanediol in the 1 , 4 butanediol production process .

[0031] The process of the invention is preferably built as a new plant to operate the process , but the process may also be provided by retrofitting a dimethyl succinate production process to an existing plant for the production of 1 , 4- butanediol . Thus , there may be provided a method of modi fying a 1 , 4 butanediol production process , the 1 , 4-butanediol production process comprising a first esteri fication section and a hydrogenolysis section, the method comprising providing a dimethyl succinate production process comprising a hydrogenation section, and preferably a second esterification section, and characterised in that the method comprises providing at least one stream that is taken from the dimethyl succinate production process and fed to the 1 , 4 butanediol production process . It will be appreciated that the method can include the provision of any of the features described above in relation to the process .

[0032] It will be appreciated that features described in relation to one aspect of the invention may be equally applicable in another aspect of the invention . For example , features described in relation to the feeding of one stream, may be equally applicable to the feeding of another stream, and vice versa . Some features may not be applicable to , and may be excluded from, particular aspects of the invention .

[0033] Description of the Drawings

[0034] Embodiments of the present invention will now be described, by way of example , and not in any limitative sense , with reference to the accompanying drawings , of which :

[0035] Figure 1 is a process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention;

[0036] Figure 2 is another process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention;

[0037] Figure 3 is part of the process according to the invention of Figure 2 ;

[0038] Figure 4 is an alternative part of a process according to the invention;

[0039] Figure 5 is another process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention;

[0040] Figure 6 is another process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention;

[0041] Figure 7 is another process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention;

[0042] Figure 8 is another process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention;

[0043] Figure 9 is another process for the production of dimethyl succinate and 1 , 4 butanediol according to the invention; Figure 10 is another process for the production of dimethyl succinate and 1,4 butanediol according to the invention; and

[0044] Figure 11 is another process for the production of dimethyl succinate and 1,4 butanediol according to the invention.

[0045] Detailed Description

[0046] In the following description of the figures, like numbered items have the same meaning and are not redefined in the description of each figure.

[0047] In figure 1 a maleic anhydride feed stream 1 is fed to a 1,4 butanediol production process 2 and a dimethyl succinate production process 3. A methanol feed stream 9 and a hydrogen feed stream 7 are fed to the 1,4 butanediol production process. A 1,4 butanediol product stream 4 and a water stream 11 exit the 1,4 butanediol production process 2. A further methanol feed stream 8 and a further hydrogen feed stream 6 are fed to the dimethyl succinate production process 3. It will be appreciated that the methanol feed streams 8 and 9 may share a common source that is split to form the two methanol feed streams 8 and 9. Similarly the hydrogen feed streams 6 and 7 may share a common source that is split to form the two hydrogen feed streams 6 and 7. A dimethyl succinate product stream 5 and a further water stream 10 exit the dimethyl succinate production process 3. At least one stream 30 is taken from the dimethyl succinate production process 3 and fed to the 1,4 butanediol production process 2.

[0048] In figures 2, 5, 6, 7, 8, 9 and 10 the 1,4 butanediol production process 2 includes a first esterification section 20, to which the maleic anhydride feed stream 1 and the methanol feed stream 9 are fed, and from which the water stream 11 is withdrawn . In the first esteri fication section 20 , maleic anhydride and methanol react in an esteri fication reaction to produce dimethyl maleate and water . In a first step of the esteri fication reaction, maleic anhydride esteri fies with methanol to monomethyl maleate . Thi s typically happens autocatalytically in a first reaction zone . The monomethyl maleate is then esteri fied again with methanol to dimethyl maleate and water, this advantageously occurs in a reaction column with a catalyst and water removal . The catalyst advantageously increases the reaction rate , and the water removal advantageously improves conversion . A distillation column is typically provided to separate excess methanol from the water . A dimethyl maleate stream 15 is fed from the first esteri fication section 20 to a hydrogenolysis section 22 . In the hydrogenolysis section 22 dimethyl maleate is converted with hydrogen from hydrogen feed stream 7 into 1 , 4 butanediol . This occurs by saturation of the dimethyl maleate to dimethyl succinate and hydrogenolysis of the dimethyl succinate to 1 , 4 butanediol , both reaction steps occurring together in the same reaction zone in the hydrogenolysis section 22 . The hydrogenolysis section 22 also produces tetrahydrofuran ( THF) and y-butyrolactone ( GBL ) along with the 1 , 4-butanediol and those components are passed in crude 1 , 4-butanediol stream 17 to product refining section 24 , where those components are refined into a 1 , 4-butanediol product stream 14 , a THF product stream 12 and a GBL product stream 13 .

[0049] Also in figures 2 , 5 , 6 , 7 , 8 , 9 and 10 , the dimethyl succinate production process 3 includes a second esteri fication section 21 , to which the maleic anhydride feed stream 1 and the further methanol feed stream 8 are fed, and from which the further water stream 10 is withdrawn . In the second esteri fication section 21 , maleic anhydride and methanol react in an esteri fication reaction to produce dimethyl maleate and water . In a first step of the esteri fication reaction, maleic anhydride esteri fies with methanol to monomethyl maleate . This typically happens autocatalytically in a first reaction zone . The monomethyl maleate is then esteri fied again with methanol to dimethyl maleate and water, this advantageously occurs in a reaction column with a catalyst and water removal . The catalyst advantageously increases the reaction rate , and the water removal advantageously improves conversion . A disti llation column is typically provided to separate excess methanol from the water . A dimethyl maleate stream 16 is fed from the second esteri fication section 21 to a hydrogenation section 23 . In the hydrogenation section 23 dimethyl maleate is hydrogenated to dimethyl succinate using hydrogen from further hydrogen feed stream 6 . A crude dimethyl succinate stream 18 is fed to dimethyl succinate puri fication section 25 , where contaminants are removed to produce dimethyl succinate product stream 5 .

[0050] In the embodiment of figure 2 , a hydrogen stream 31 is taken from the hydrogenation section 23 and fed to the hydrogenolysis section 22 . A particularly preferred embodiment of this arrangement is shown in figure 3 . In figure 3 , the hydrogenation section 23 comprises a hydrogenation reactor 101 . The dimethyl maleate stream 16 and the further hydrogen feed stream 6 are fed to the hydrogenation reactor 101 . The further hydrogen feed stream 6 contains suf ficient excess , for example around 1 . 5 times the stoichiometrically required amount , of hydrogen for the hydrogenation reaction to proceed to suf ficient conversion .

[0051] There is no recycle of hydrogen around the hydrogenation reactor 101 . The crude dimethyl succinate stream 18 is withdrawn from the hydrogenation reactor 101 and a hydrogen stream 31 is separated from the crude dimethyl succinate stream 18 . The hydrogen stream 31 contains excess hydrogen from the hydrogenation reactor 101 . The hydrogen stream 31 is fed to the hydrogenolysis section 22 , thus ensuring that the excess hydrogen is not wasted . The hydrogenolysis section 22 comprises a hydrogenolysis reactor 100 , in which dimethyl maleate in the dimethyl maleate stream 15 is converted with hydrogen to 1 , 4-butanediol . There is a recycle loop 103 around the hydrogenolysis reactor 100 in which hydrogen is circulated so as to achieve suf ficient excess of hydrogen in the hydrogenolysis reactor 100 . The recycle loop 103 passes through a compressor 102 . Hydrogen stream 31 is fed to the recycle loop 103 so that it is compressed in compressor 102 along with the rest of the recycle loop 103 . Hydrogen stream 31 is thus a source of make-up hydrogen in the recycle loop 103 . In this embodiment , make-up hydrogen is also supplied from hydrogen feed stream 7 . In that way the excess of hydrogen can be ef ficiently managed in both the hydrogenation reactor 101 and the hydrogenolysis reactor 100 , whi le also maximising feedstock ef ficiency .

[0052] An alternative embodiment of the arrangement of figure 2 is depicted in figure 4 . In figure 4 , hydrogen feed stream 6 and further hydrogen feed stream 7 are replaced by a common hydrogen feed stream 67 . Common hydrogen feed stream 67 is fed, along with hydrogen stream 31 , to the recycle loop 103 . Some of the hydrogen from recycle loop 103 is then fed in stream 40 to the hydrogenation reactor 101 , while the rest is fed to the hydrogenolysis reactor 100 . In this embodiment , compressor 102 is ef fectively used to compress both the recycle loop 103 and the common hydrogen feed stream 67 .

[0053] In the embodiment of figure 5 , a heavies stream 32 is removed in the dimethyl succinate puri fication section 25 and fed to the first esteri fication section 20 . In this particular example , the heavies stream 32 comprise some monomethyl succinate and dimethyl succinate . Monomethyl succinate and dimethyl succinate in the heavies stream 32 represent a loss of feedstock from the dimethyl succinate production process 3 , but by feeding the heavies stream 32 to the first esteri fication section 20 , the monomethyl succinate and dimethyl succinate in the heavies stream 32 are not a feedstock loss to the overall process and are instead converted to useful products . Moreover, the dimethyl succinate puri fication section 25 can be built and operated at lower cost by allowing more dimethyl succinate s lip in the heavies stream 32 in order to achieve suf ficient dimethyl succinate product quality, because that slipped dimethyl succinate is not being lost but is instead being converted to useful products in the 1 , 4 butanediol production process 2 . The heavies stream 32 is fed to the first esteri fication section 20 in figure 5 . The first esteri fication section 20 comprises a first esteri fication reaction column, for example as described in US5536856 , US2002 / 026070 or US4032458 , and the heavies stream 32 is fed to the first esteri fication reaction column . In the first esteri fication reaction column the monomethyl succinate in the heavies stream 32 i s converted to dimethyl succinate , which will then be converted to useful products in the hydrogenolysis section 22 , and acid components in the heavies stream 32 are removed . This protects the catalyst in the hydrogenolysis section 22 from shortened li fetime due to increased acid content .

[0054] In the embodiment of figure 6 , a first lights stream 33 is removed in the dimethyl succinate puri fication section 25 and fed to the hydrogenolysis section 22 . In that way, dimethyl succinate in the first lights stream 33 is converted to useful product in the hydrogenolysis section 22 , thus improving feedstock ef ficiency . Also , because the f irst lights stream 33 is not lost from the overall process , even though it is removed from the dimethyl succinate production process 3 , the dimethyl succinate puri fication section 25 can be built or operated at lower cost by allowing more dimethyl succinate to slip in the first lights stream 33 . The slipped dimethyl succinate is not lost but is instead converted to useful products in the 1 , 4 butanediol production process 2 .

[0055] In the embodiment of figure 7 , the 1 , 4 butanediol production process 2 comprises a recycle loop comprising methanol recycle 41 and dimethyl succinate recycle 42 . Methanol recycle 41 returns methanol from product refining section 24 to first esteri fication section 20 and dimethyl succinate recycle 42 returns unreacted dimethyl succinate from product refining section 24 to hydrogenolysis section 22 . In figure 7 , second lights stream 34 is fed to product refining section 24 . Methanol in the second lights stream 34 is separated in the product refining section 24 and recycled to the first esteri fication section 20 in the methanol recycle 41 . Dimethyl succinate in the second lights stream 34 i s separated in the product refining section 24 and recycled to the hydrogenolysis section 22 in the dimethyl succinate recycle 42 . Thus both methanol and dimethyl succinate in the second lights stream 34 are ef ficiently directed to the most suitable places in the 1 , 4-butanediol production process 2 using the existing product refining section 24 , with no requirement for extra separation equipment .

[0056] In the embodiment of figure 8 , a third lights stream 35 is fed from the dimethyl succinate puri fication section 25 to the first esteri fication section 20 . Methanol in the third lights stream 35 reacts in the first esteri fication section 20 and dimethyl succinate in the third lights stream 35 passes through the first esteri fication section 20 and reacts in the hydrogenolysis section 22 . Thus , the components of the third lights stream 35 are also ef ficiently used in this embodiment .

[0057] While the embodiments of figures 6 , 7 and 8 have presented alternative ways to fed lights from the dimethyl succinate puri fication section 25 to the 1 , 4-butanediol production process 2 , it will be appreciated that some or all aspects of those embodiments can also be combined, for example with more than one of the first lights stream 33 , the second lights stream 34 and / or the third lights stream 35 present in any particular embodiment .

[0058] In figure 9 the dimethyl succinate production process 3 includes a sul fur-removal resin bed 27 . A wash stream 36 is generated when the sul fur-removal resin bed 27 is washed and the wash stream 36 is fed to the hydrogenolysis section 22 . In this example the sul fur-removal resin bed is washed with dimethyl succinate and the wash stream 36 thus comprises dimethyl succinate , which is converted into useful products in the hydrogenolysis section 22 . In figure 10 , the sul fur-removal resin bed 27 is washed with methanol and / or water and alternative wash stream 37 is fed to the product refining section 24 . In the product refining section 24 methanol and / or water in the alternative wash stream 37 can be separated using the existing equipment of the product refining section 24 , with no new separation equipment required . The methanol and / or water is returned to the first esteri fication 20 in methanol recycle 41 , where the methanol can react in the esteri fication and any water can be separated along with water generated in the esteri f ication section 20 , again making use of existing separation equipment . Any dimethyl succinate in the alternative wash stream 37 is recycled to the hydrogenolysis section in dimethyl succinate recycle 42 . Processing the wash fluids in this way reduces loss of usable components and increases sustainability and ef ficiency by using separation equipment that is present anyway in the 1 , 4-butanediol production process 2 .

[0059] In figure 11 the 1 , 4-butanediol production process 2 and the dimethyl succinate production process 3 share a common esteri fication section 110 . In other words , the first esteri fication section 20 and the second esteri fication section 21 of figures 2 , 5 , 6 , 7 , 8 , 9 and 10 are combined into common esteri fication section 110 . It could al so be said that the common esteri fication section 110 is the f irst esteri fication section 20 and the second esteri fication section 21 . At least one stream 30 is fed from the dimethyl succinate production process 3 to the 1 , 4-butanediol production process 2 .

[0060] It will be appreciated by persons skilled in the art that the above embodiments have been described by way of example only, and not in any limitative sense , and that various alterations and modi fications are possible without departure from the scope of the invention as defined by the appended claims . For example , embodiments described above may be combined so that multiple streams are fed from the dimethyl succinate production process 3 to the 1 , 4-butanediol production process 2 . As an example , a hydrogen stream 31 , a heavies stream 32 and a lights stream, such as first lights stream 33 and / or second lights stream 34 and / or third lights stream 35 , may all be fed from the dimethyl succinate production process 3 to the 1 , 4-butanediol production process 2 . As another example , in the arrangement of figure 11 , only some equipment may be shared between the first esteri fication section and the second esteri fication section . In a particularly preferred variation of the embodiment of figure 11 , the common esteri fication section 110 comprises a shared first reaction zone in which monoester is formed, preferably autocatalytically, but there are then separate reaction columns for the formation of the diester . In this embodiment the first esteri fication section 20 comprises the common esteri fication section 110 and a first of the reaction columns and the second esteri fication section 21 comprises the common esteri fication section 110 and a second of the reaction columns . In such an embodiment the common esteri fication section 110 may also comprise shared catalyst loading systems and other shared equipment for example .

Claims

Claims1 . A process for the production of dimethyl succinate and 1 , 4 butanediol , the process comprising a 1 , 4 butanediol production process comprising a first esteri fication section and a hydrogenolysis section and a dimethyl succinate production process comprising a second esteri fication section and a hydrogenation section, characterised in that at least one stream is taken from the dimethyl succinate production process and fed to the 1 , 4 butanediol production process .2 . A process according claim 1 , wherein a hydrogen stream is taken from the hydrogenation section and fed to the hydrogenolysis section .3 . A process according to claim 2 , wherein the hydrogenation section does not comprise a hydrogen recycle .4 . A process according to claim 2 or 3 , wherein the hydrogenolysis section comprises a hydrogen recycle .5 . A process according to any preceding claim, wherein the dimethyl succinate production process comprises a dimethyl succinate puri fication section downstream of the hydrogenation section and heavies removed in the dimethyl succinate puri fication section are fed to the first esteri fication section .6 . A process according to claim 5 , wherein the heavies comprise monomethyl succinate .7 . A process according to any preceding claim, wherein the dimethyl succinate production process comprises adimethyl succinate puri fication section downstream of the hydrogenation section and wherein lights removed in the dimethyl succinate puri fication section are fed to the 1 , 4 butanediol production process .8 . A process according to claim 7 , wherein the lights comprise dimethyl succinate and are fed to the hydrogenolysis section .9 . A process according to claim 8 , wherein the hydrogenolysis section comprises a recycle loop and the lights are fed to the recycle loop .10 . A process according to claim 7 , wherein the 1 , 4 butanediol production process further comprises a product refining section downstream of the hydrogenolysis section and wherein the lights are fed to the product refining section .11 . A process according to claim 10 wherein dimethyl succinate is recycled from the product refining section to the hydrogenolysis section and the lights compri se dimethyl succinate .12 . A process according to claim 10 or claim 11 wherein methanol is recycled from the product refining section to the first esteri fication section and the lights comprise methanol .13 . A process according to any preceding claim wherein a wash stream is taken from the dimethyl succinate production process and fed to the 1 , 4 butanediol production process .14 . A process according to claim 13 , wherein the wash stream is a stream generated in the washing of one or more resins in the dimethyl succinate production process .

15. A process according to claim 14 , wherein the wash stream is generated in the washing of a sul fur removal resin upstream of the hydrogenation section .

16. A process according to any of claims 13 to 15 , wherein the wash stream comprises dimethyl succinate and is fed to the hydrogenolysis section .17 . A process according to any of claims 13 to 15 , wherein the wash stream comprises methanol , wherein the 1 , 4 butanediol production process further comprises a product refining section downstream of the hydrogenolysis section, wherein methanol removed in the product refining section is recycled to the first esteri fication section, and wherein the wash stream is fed to the product refining section .18 . A process according to any preceding claim, wherein a start-up stream produced during start-up of the dimethyl succinate production process is fed to the 1 , 4 butanediol production process .

19. A process according to any preceding claim wherein the first and second esteri fication sections share one or more equipment items .20 . A process according to claim 19 , wherein the first esteri fication section is the second esteri fication section .21 . A process according to any preceding claim, wherein maleic anhydride is esteri fied to dimethyl maleate in the first esteri fication and in the second esteri fication section .22 . A process according to any preceding claim, wherein dimethyl maleate is converted to 1 , 4 butanediol through reacting with hydrogen in the hydrogenolysis section .23 . A process according to any preceding claim, wherein dimethyl maleate is hydrogenated to dimethyl succinate in the hydrogenation section .24 . A process according to any preceding claim, wherein the stream comprises one or more reactants or intermediates of the 1 , 4 butanediol production process .

25. A process according to claim 24 , wherein the stream comprises one or more of maleic anhydride , methanol , hydrogen, monomethyl maleate , dimethyl maleate , monomethyl succinate and dimethyl succinate .

26. A process according to claim 25 , wherein the stream comprises one or more of hydrogen, monomethyl succinate and dimethyl succinate and is taken from in, or downstream of , the hydrogenation .27 . A method of modi fying a 1 , 4 butanediol production process , the 1 , 4-butanediol production process comprising a first esteri fication section and a hydrogenolysis section, the method comprising providing a dimethyl succinate production process comprising a hydrogenation section and characterised in that the method comprises providing at least one stream that istaken from the dimethyl succinate production process and fed to the 1,4 butanediol production process.

28. A method according to claim 27, wherein the method results in a process for the production of dimethyl succinate and 1,4 butanediol according to any of claims1 to 26.

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