New method for preparing c4 diacid esters via coal chemical oxalate and glycolate feedstocks

Abstract

The present application relates to the field of new material fine chemicals, and particularly relates to a low-cost preparation of a series of carbon four (C4) diacid (ester) by using coal chemical industry abundant oxalate and / or glycollic acid (ester) bulk raw materials, including butene diacid (ester), succinic acid (ester), tartaric acid (ester), and / or malic acid (ester) and the like, and the process features are that all of the coal chemical industry abundant carbon monoxide (synthesis gas), methanol, or formaldehyde and the like bulk C1 raw materials are used, and a series of C4 skeleton products are simply and efficiently prepared. The technology practices outstanding cost reduction and efficiency improvement results, and is beneficial to large-scale preparation of high-value chemicals relying on rich coal resources in China.

Description

[Technical Field]

[0001] This invention relates to the field of new materials and fine chemicals, and particularly to the low-cost preparation of a series of C4 dicels (esters) using abundant coal-derived oxalates and / or glycolates as raw materials. These include butylated dicels, succinic acid esters, tartaric acid esters, and / or malic acid esters. The process is characterized by the use of abundant coal-derived carbon monoxide (syngas), methanol, or formaldehyde, among other readily available C1 raw materials, to produce a simple and efficient series of C4 skeletal products. This technology achieves significant cost reduction and efficiency improvement, and is conducive to the large-scale production of high-value chemicals based on my country's abundant coal resources. [Background Technology]

[0002] Oxalate and glycolic acid (esters) are important raw materials in the coal chemical industry chain. They are key common intermediates in the coal-to-ethylene glycol and coal-based syngas-to-glycolic acid / polyglycolic acid (PGA) industrial processes. There are considerable production capacity facilities in China, and they are representative backbone varieties of coal-based chemicals.

[0003] On the other hand, many representative C4 skeleton substances in the chemical industry, especially maleic acid, trans-butenedioic acid, and succinic acid or its esters, are fundamental chemicals with extremely wide applications. Traditional manufacturing methods heavily rely on C4 or aromatic hydrocarbon resources in the petroleum refining industry chain for preparation, particularly the process of producing maleic anhydride from n-butane or benzene via high-temperature gas-phase oxidation, followed by the hydrolysis or alcoholysis of maleic anhydride to produce butenedioic acid (anhydride), or by hydrogenation reduction to produce succinic acid (anhydride). This process is highly dependent on oil and gas resources, energy-intensive, and costly. In recent years, the gradual growth of biodegradable materials and their replacement of traditional polyolefin products, particularly the increasing demand for succinic acid and its esters from biodegradable materials such as PBS, has created continuous cost pressures for cost reduction and efficiency improvement.

[0004] Other C4 skeletal chemicals that deserve special attention, such as malic acid and tartaric acid, are important nutritional chemicals and food additives. They have long relied on plant extraction or bio-fermentation methods for production, but there are still technical problems that need to be solved, such as low production efficiency and high environmental pressure.

[0005] Against the backdrop of the aforementioned industries, developing the production of C4 series products such as butenaic acid and succinic acid using bulk raw materials from my country's unique coal chemical resources, especially oxalate and glycolate, in order to achieve a beneficial circular economy and cost competitiveness, is a major issue facing the industry's transformation and upgrading.

[0006] This application has for the first time discovered that, through ingenious reaction principle design and practical exploration, a new process and flexible manufacturing of all the above-mentioned C4 series products can be achieved using C1 type raw materials, which are abundant and industrially inexpensive and readily available in China's coal chemical industry, especially representative bulk industrial products such as carbon monoxide, carbon monoxide / hydrogen (syngas), methanol, or formaldehyde, as well as oxalate and glycolic acid resources directly produced from them, through an extremely simple process flow.

[0007] This newly disclosed technology boasts outstanding process safety, environmental friendliness, and overall cost competitiveness. Furthermore, this technological breakthrough unexpectedly enables the large-scale production of the four major C4 backbone products—butenedioic acid (ester), succinic acid (ester), malic acid, and tartaric acid—from coal chemical resources for the first time, offering a significant low-cost manufacturing advantage compared to traditional petrochemical-based or bio-fermentation routes. Leveraging my country's abundant coal resources, this alternative technology holds immense strategic significance for energy security and industrial upgrading. [Summary of the Invention]

[0008] This application has now discovered that, as shown in reaction formula (I), the glycolate type substance of structural formula A and the additive [P] react under reaction conditions to dimerize to obtain the (trans / cis) trans / cis-butenedioate of structural formula B; subsequently, B and the reducing agent [H] undergo a hydrogenation reaction under reaction conditions to obtain the succinate product of structural formula C.

[0009] In our practical exploration of reaction formula (I), we further discovered that when using the acetate ester represented by structural formula D as a solvent, it can simultaneously act as a reactant and undergo a substitution reaction with A. Therefore, we also claim rights to reaction formula (II), namely, the succinate product C prepared by the condensation of glycolate type A and acetate D under reaction conditions.

[0010]

[0011] R1, R2, or R3 are independent of each other and are hydrogen or aliphatic or aromatic hydrocarbon groups containing 1-24 carbon atoms; preferably, R1, R2, or R3 are hydrogen, methyl, ethyl, propyl, or butyl.

[0012] The additive [P] is a catalyst, promoter, or polymerization inhibitor for the reaction; preferably, the catalyst or promoter is a Lewis base or Lewis acid compound.

[0013] Preferably, the Lewis base is a metal (hydro)oxide, hydride, alkoxide, alkylamine, metal (hydrocarbonate), sulfate, carboxylate, oxalate, nitrate, phosphate, sulfonate, ammonia, ammonia water, or an organic amine; more preferably, the Lewis base is sodium methoxide, potassium methoxide, sodium tert-butoxide, potassium tert-butoxide, sodium carbonate, potassium carbonate, ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide, aluminum hydroxide, magnesium hydroxide, sodium oxide, calcium oxide, aluminum oxide, sodium hydride, calcium hydride, triethylamine, tributylamine, diisopropylethylamine, or pyridine;

[0014] Preferably, the Lewis acid is hydrochloric acid, sulfuric acid, boric acid, nitric acid, phosphoric acid, sulfonic acid, oxalic acid, organic carboxylic acid, nonmetallic acids or oxides of different valence states, metal halides, sulfides, or oxides, zeolites, molecular sieves, diatomaceous earth, or heteropoly acids. More preferably, the Lewis acid is hydrochloric acid, sulfuric acid, nitric acid, sulfonic acid, oxalic acid, acetic acid, benzoic acid, tartaric acid, malic acid, citric acid, gluconic acid, molecular sieves, diatomaceous earth, or heteropoly acids.

[0015] Based on raw material A, the amount of additive used is a catalytic amount, an equivalent amount, or an excess amount (0.001-100 equivalents). Preferably, the amount of catalyst or accelerator added is 0.1-1000% of the reactant; more preferably, 1-200%, and even more preferably, 1-100%.

[0016]

H

[0017] "conditions" refers to at least one of the following: solvent, light, heat, microwave, ultrasound, vacuum, or pressure.

[0018] The solvent is selected from at least one of substituted or unsubstituted aromatic hydrocarbons, straight-chain or branched aliphatic hydrocarbons, (sulfoxides), amides, ethers, alcohols, esters, ketones, nitriles, carboxylic acids, water, amines, carbonates, ionic liquids, and supercritical carbon dioxide containing 1 to 24 carbons; or the liquid substrate itself acts as a solvent medium.

[0019] In some preferred embodiments of the present invention, the solvent is selected from water, dioxane, acetonitrile, ethanol, butanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, dimethyl sulfone, benzyl sulfoxide, benzyl sulfone, cyclobutane sulfoxide, sulfolane, trichlorosilane, dichloromethane, dichloroethane, dimethyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, chloroform, carbon tetrachloride, benzene, toluene, xylene, trimethylbenzene, tetramethylbenzene, acetonitrile, ethylbenzene, diethylbenzene, chlorobenzene, dichlorosilane, etc. At least one of benzene, anisole, nitrobenzene, heptane, hexane, petroleum ether, tetrahydrofuran, methyltetrahydrofuran, methyl tert-butyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, propylene glycol methyl ether acetate, triethylamine, tributylamine, dimethylisopropylamine, pyridine, N,N-tetramethylethylenediamine, N-alkylmorpholine, N-alkylpyrrole, N,N-dimethylformamide, formylmorpholine, N,N-diethylformamide, and N-methylpyrrolidone.

[0020] The use of solvents is preferred but not essential. Under certain conditions, solvents can be omitted, i.e., using the dissolved or melted form of the reactants, or directly mixing the reactants and then reacting under heating, grinding, or gas-phase conditions; and using supercritical carbon dioxide as the reaction medium. The advantages of using supercritical carbon dioxide as the reaction medium are that it is environmentally friendly and facilitates the occurrence of the reaction and the separation of products, advantages well known to professionals in this field.

[0021] Light refers to the reaction system under light irradiation conditions, with the wavelength range of light being 200-780 nanometers.

[0022] Heat refers to the reaction system being carried out under heating conditions, with reaction temperatures ranging from -25 to 450 degrees Celsius.

[0023] Microwave or ultrasonic refers to a system that uses microwave or ultrasonic generators to radiate a reaction system.

[0024] Pressure or vacuum refers to the reaction system being carried out under pressure or a certain degree of vacuum. The pressure of the reaction process can be 0.001-200 atmospheres.

[0025] The above steps A to B and B to C can be performed separately or in stages; or preferably, the above two steps can be performed continuously in a "one-step" or "one-pot" manner without separating and purifying intermediate B. It should also be noted that this technology can be used to produce succinic acid (ester) B or succinic acid (ester) C separately, or for the co-production of B and C.

[0026] As shown in the following formula, methyl glycolate type raw material A can be conveniently prepared by selective hydrogenation reduction via the so-called coal-to-syngas-oxalate DMO route, or by carbonylation reaction of methyl acetal obtained from methanol-formaldehyde. These are both known and mature technologies, and both directly use the cheapest and most readily available C1 type raw material.

[0027]

[0028] Utilizing abundant C1 feedstocks from coal chemical industry, particularly carbon monoxide (syngas), methanol, and formaldehyde—materials with the lowest cost advantage—to produce typical downstream products that previously relied on bio-based or petrochemical refining chains not only achieves cost reduction and efficiency improvement but also makes a positive contribution to national energy security and industrial transformation and upgrading. Furthermore, my country's vast coal-producing areas possess extremely rich coal-to-methanol / formaldehyde, as well as coal-to-oxalate, ethylene glycol, and methyl glycolate production capacity, which has a strong industrial empowerment characteristic for revitalizing existing assets and converting them into high-value-added butenanic acid and succinic acid and ester series products.

[0029] It is worth noting that, compared with the petroleum-based route, the butenedioic acid B and succinic acid and ester C prepared by the process disclosed in this invention have a significant advantage in low cost; contrary to conventional understanding, this makes the preparation of 1,4-butanediol BDO via hydrogenation of B and / or C economically feasible for the first time.

[0030] In view of this, this application also claims rights to the process technology disclosed in reaction formulas (III-IV), namely, the glycolate type substance shown in structural formula A and the additive [P] react under reaction conditions to dimerize and obtain the (trans / cis) trans / cis-butenedioic acid ester shown in structural formula B; then B and the reducing agent [H] undergo hydrogenation under reaction conditions to obtain the butanediol product shown in structural formula E (general formula III); or, glycolate A and acetate D are condensed under reaction conditions to prepare succinate product C, which then undergoes hydrogenation with the reducing agent [H] under reaction conditions to obtain the butanediol product shown in structural formula E (general formula IV).

[0031]

[0032] In the research and development practice of this project, we also unexpectedly discovered that, as shown in the general reaction formula (V), glycolate A and oxidant [O] are oxidized under reaction conditions to obtain glyoxylate ester with structural formula F, which is then condensed with acetate D under reaction conditions to prepare malate ester product with structural formula G; similarly, as shown in the general reaction formula (VI), glyoxylate F and glycolate A undergo a condensation reaction under reaction conditions to obtain tartrate ester product with structural formula H.

[0033]

[0034] Here, the oxidant [O] is any reagent capable of oxidizing the primary alcohol hydroxyl group in structure A to the corresponding aldehyde group; preferably, [O] is at least one of oxygen, hydrogen peroxide, hydrocarbon peroxide, nonmetallic (per)oxide, metallic (per)oxide, ozone, halogen, organic peroxyacid, metal heteropolyacid, dialkyl peroxide ketone (e.g., DMDO), organic NO radical oxide (e.g., 2,2,6,6-tetramethylpiperidine oxide TEMPO), oxalyl chloride-DMSO, haloamide (e.g., NCS or TCCA), metal (nitrite) anhydride, metal (hypo)halate, hydrocarbon hypohalate, etc.

[0035] Preferably, one embodiment of the reaction formula (I) is (IA), which involves the dimerization of methyl glycolate as a raw material and additive [P] under reaction conditions to obtain methyl butenedioate, which is further subjected to hydrogenation to obtain methyl succinate (preferably R2 is hydrogen or methyl):

[0036]

[0037] Methyl butyrate or methyl succinate can be used to prepare butyric acid, succinic acid, or other series of esterified products via hydrolysis or alcoholysis, if required. These techniques are well-known in the industry.

[0038] Preferably, another embodiment of reaction formula (II) is (IIA), which involves the condensation of methyl glycolate, methyl acetate, and additive [P] under reaction conditions to obtain methyl succinate (preferably R2 is hydrogen or methyl):

[0039]

[0040] Preferably, one embodiment of reaction formula (III) is (IIIA), which involves dimerization of methyl glycolate as a raw material and additive [P] under reaction conditions to obtain methyl butenedioate (or its R2O-substituted methyl butenedioate precursor), which is further reduced by hydrogenation to obtain butanediol (preferably R2 is hydrogen or methyl):

[0041]

[0042] Preferably, another embodiment of the reaction formula (IV) is (IVA), in which methyl glycolate, methyl acetate, and additive [P] undergo condensation under reaction conditions to obtain methyl succinate (preferably R2 is hydrogen or methyl), which is further reduced by hydrogenation to obtain butanediol (preferably R2 is hydrogen or methyl):

[0043]

[0044] Preferably, one embodiment of the general reaction formula (V) is (VA), which involves the oxidation of methyl glycolate with an oxidant [O] under reaction conditions to obtain methyl glyoxylate, which then condenses with acetate D to obtain the malate product.

[0045]

[0046] Preferably, one embodiment of reaction formula (VI) is (VIA), which involves oxidizing methyl glycolate with an oxidant [O] under reaction conditions to obtain methyl glyoxylate, which is then condensed with methyl glycolate to obtain the tartrate ester product.

[0047]

[0048] The techniques for obtaining malic acid or tartaric acid by acid hydrolysis of malic acid esters or tartaric acid esters, or by alkaline hydrolysis of malic acid esters or tartaric acid salts, are well-known to industry professionals.

[0049] In the research and development practice of this project, we also unexpectedly discovered that, as shown in the general reaction formula (VII), oxalate ester and glycolate ester A, as well as additive [P], condense under reaction conditions to obtain keto ester ester shown in structural formula J, which then undergoes hydrogenation reaction with reducing agent [H] under reaction conditions to obtain tartaric acid (ester) shown in structural formula H; and as shown in the general reaction formula (VIII), oxalate ester I and acetate ester D, as well as additive [P], condense under reaction conditions to obtain keto ester ester shown in structural formula K, which then undergoes hydrogenation reaction with reducing agent [H] under reaction conditions to obtain malic acid (ester) shown in structural formula G.

[0050]

[0051] Preferably, one embodiment of reaction formula (VII) is (VIIA), which involves the condensation of dimethyl oxalate and methyl glycolate as raw materials under reaction conditions to obtain methyl ketoate, which is then hydrogenated and reduced to obtain tartrate ester product (wherein R2 is preferably hydrogen and methyl):

[0052]

[0053] Preferably, one embodiment of reaction formula (VIII) is (VIIIA), which involves the condensation of dimethyl oxalate and methyl acetate under certain reaction conditions to obtain methyl ketoate, which is then hydrogenated and reduced to yield the malate product (correspondingly, an optically pure product can be prepared by so-called enantioselective hydrogenation using a chiral catalyst):

[0054]

[0055] We will explain further in the embodiments.

Detailed Implementation Methods

[0056] The essence of the invention is further illustrated below with reference to specific embodiments:

[0057] Example:

[0058]

[0059] Under nitrogen protection at room temperature, 41.8 g of methyl glycolate and 15.2 g of potassium tert-butoxide were placed in 200 mL of dry tetrahydrofuran. The system was refluxed overnight and then cooled to room temperature. The reaction solution was adjusted to neutral with sulfuric acid, the solvent was removed by vacuum distillation, and 100 mL of ice-cold ethyl acetate was added for dilution. The solution was rapidly filtered through diatomaceous earth, and the supernatant was concentrated and eluted with hexane-ethyl acetate on silica gel column chromatography to obtain 29.1 g of methyl butenedioate (cis / trans = 1 / 3).

[0060] Under nitrogen protection, 28.2 g of the obtained 1 / 3 cis / trans-butenedioate was mixed with 20 mL of methanol, and 2% molar amount of alumina-supported palladium catalyst (Pd / AlO(OH)) was added. After replacing the nitrogen with hydrogen, the mixture was hydrogenated at room temperature and atmospheric pressure for 2 hours to obtain 27.8 g of dimethyl butyrate.

[0061] Example:

[0062]

[0063] Under nitrogen protection at room temperature, 35.7 g of methyl methyl glycolate and 13.4 g of potassium tert-butoxide were placed in 200 mL of dry tetrahydrofuran. The system was refluxed overnight and then cooled to room temperature. The reaction solution was adjusted to neutral with sulfuric acid, the solvent was removed by vacuum distillation, and 100 mL of ice-cold ethyl acetate was added for dilution. The solution was rapidly filtered through diatomaceous earth, and the supernatant was concentrated and eluted with hexane-ethyl acetate on silica gel column chromatography to obtain 21.4 g of methyl butenedioate (cis / trans = 1 / 2.6).

[0064] Following the palladium-catalyzed hydrogenation reaction conditions of Example 1, 11.5 g of dimethyl butyrate was obtained from the reduction of 11.8 g of cis / trans-butenedioic acid ester.

[0065] Example:

[0066]

[0067] Under nitrogen protection at room temperature, 18.6 g of methyl methyl glycolate was placed in 250 mL of dry methyl acetate. 10.3 g of sodium methoxide was added in portions to the system at reflux temperature and the mixture was stirred rapidly for 8 hours. After the reaction solution was adjusted to neutral with sulfuric acid, the mixture was cooled with ice water and rapidly filtered through diatomaceous earth to remove salt. The supernatant was concentrated and eluted with hexane-ethyl acetate on silica gel column chromatography to obtain 24.1 g of dimethyl butyrate.

[0068] Example:

[0069]

[0070] Under nitrogen protection at room temperature, 16.1 g of methyl glycolate was placed in 220 mL of dry methyl acetate. 20.6 g of potassium tert-butoxide was added in portions to the system at reflux temperature and the mixture was stirred rapidly for 8 hours. After the reaction solution was adjusted to neutral with sulfuric acid, the mixture was cooled with ice water, filtered rapidly on diatomaceous earth to remove salt, and the supernatant was concentrated and eluted with hexane-ethyl acetate on silica gel column chromatography to obtain 22.7 g of dimethyl butyrate.

[0071] Example:

[0072]

[0073] In a high-pressure reactor, 23.6 g of dimethyl butyrate and 1% molar amount of (Triphos)Ru (trimethylenemethane TMM) catalyst were mixed in 50 mL of dry dioxane solvent and reacted rapidly with stirring at 140 °C and 55 atm hydrogen pressure for 24 hours to give 14.1 g of 1,4-butanediol (BDO) product in an almost quantitative yield.

[0074] Example:

[0075]

[0076] Using oxygen as the terminal oxidant, nitric oxide as the co-oxidant, and α-alumina as the oxidation catalyst, a gaseous mixture of methyl glycolate and nitric oxide (52% by volume) and oxygen were introduced from two ports into a fixed-bed reactor packed with α-alumina catalyst (oxygen to methyl glycolate in a 1 / 1 molar ratio, oxygen to nitric oxide in a 1 / 8 molar ratio). The reactor was operated at 85°C, 0.5 MPa, and for 0.4 h. -1Catalytic oxidation was carried out at space velocity, and the collected mixture was quantitatively analyzed by gas chromatography (GC). Methyl glycolate was converted to methyl glyoxylate with a conversion rate of 96.8% and a selectivity of 93.4%.

[0077] 19.3 g of methyl glyoxylate prepared above and 120 mL of dry methyl acetate were mixed. 4.8 g of sodium hydride powder was added in portions to the system at reflux temperature and the mixture was stirred rapidly for 6 hours. After the reaction solution was adjusted to neutral with sulfuric acid, the mixture was cooled with ice water and rapidly filtered through diatomaceous earth to remove salt. The supernatant was concentrated and eluted with hexane-ethyl acetate on silica gel column chromatography to obtain 32.9 g of dimethyl malate.

[0078] 30.0 g of dimethyl malate prepared above was placed in 150 mL of tetrahydrofuran / water mixed solvent (volume ratio 1 / 2), the pH of the system was adjusted to 2-3 with concentrated sulfuric acid, the mixture was refluxed for 6 hours and then cooled to room temperature, concentrated under reduced pressure, and the residue was recrystallized in isopropanol to obtain 20.6 g of pure malic acid.

[0079] Example:

[0080]

[0081] 16.2 g of methyl glyoxylate and 21.5 g of methyl glycolate were mixed in 150 mL of dry tetrahydrofuran. 5.1 g of sodium hydride powder was added in portions to the system at reflux temperature and the mixture was stirred rapidly for 6 hours. The reaction solution was adjusted to neutral with sulfuric acid, and the mixture was cooled with ice water. The solution was then rapidly filtered through diatomaceous earth to remove salts. The supernatant was concentrated and eluted with hexane-ethyl acetate on silica gel column chromatography to obtain 29.1 g of dimethyl tartrate (syn / anti diastereomer mixture in a ratio of 1 / 1.8).

[0082] Following the conditions described in the above embodiments, 29.1 g of dimethyl tartrate prepared above was subjected to acid hydrolysis to obtain 21.1 g of tartaric acid.

[0083] Example:

[0084]

[0085] Under ice-water cooling and nitrogen protection, 11.8 g of dimethyl oxalate and 5.4 g of sodium methoxide were placed in 150 mL of dry tetrahydrofuran. 14.6 g of methyl glycolate was dissolved in 30 mL of tetrahydrofuran and added to the above solution with stirring. After the addition was complete, the temperature was gradually raised to reflux and the reaction was continued for 2 hours. The system was acidified to pH 6-7 with 30% hydrochloric acid and then concentrated to dryness to recover tetrahydrofuran. The solution was then diluted with 150 mL of ethyl acetate. The organic phase was washed twice with saturated brine and dried with anhydrous sodium sulfate. The solution was filtered, concentrated under reduced pressure, and the residue was eluted with hexane-ethyl acetate on silica gel column chromatography to give 13.9 g of ketoester.

[0086] In a high-pressure reactor under a hydrogen atmosphere, 13.9 g of keto ester and 1% molar amount of Ru(BINAP)(MeCN)(1-3:5-η-C8H) were added. 11 The (BF4) catalyst was placed in 150 mL of dry methanol, and the mixture was stirred for 6 hours at 20 atm hydrogen pressure and room temperature to obtain dimethyl tartrate with 100% conversion.

[0087] 12.1 g of tartaric acid was prepared from 14.0 g of dimethyl tartrate through acid hydrolysis.

[0088] Example:

[0089]

[0090] Under ice-water cooling and nitrogen protection, 12.1 g of dimethyl oxalate and 5.2 g of sodium methoxide were placed in 120 mL of dry tetrahydrofuran. 13.6 g of methyl acetate was dissolved in 30 mL of tetrahydrofuran and added to the above solution with stirring. After the addition was complete, the temperature was gradually raised to reflux and the reaction was continued for 3 hours. The system was acidified to pH 6-7 with 30% hydrochloric acid and then concentrated to dryness to recover tetrahydrofuran. The solution was then diluted with 150 mL of methyl acetate. The organic phase was washed twice with saturated brine and dried with anhydrous sodium sulfate. The solution was filtered, concentrated under reduced pressure, and the residue was distilled under reduced pressure to obtain 15.0 g of keto ester.

[0091] In a high-pressure reactor under a hydrogen atmosphere, 12.8 g of keto ester and 1% molar amount of Ru(BINAP)(MeCN)(1-3:5-η-C8H) were added. 11 The (BF4) catalyst was placed in 150 mL of dry methanol, and the mixture was stirred for 6 hours at 20 atm hydrogen pressure and room temperature to obtain dimethyl malate with 100% conversion.

[0092] 8.9 g of malic acid was prepared from 13.0 g of dimethyl malate through acid hydrolysis.

[0093] It should be emphasized that the above embodiments are merely exemplary and not limiting. Based on the disclosure of this application, any adjustments or changes to reaction conditions or parameters that a person skilled in the art might normally adopt will not deviate from the spirit of the invention. The scope of protection of this patent should be determined by the relevant claims.

Claims

1. A novel process for preparing butenedioic acid (ester) or succinic acid (ester). As shown in reaction formula (I), the glycolate type substance represented by structural formula A and the additive [P] react under reaction conditions to dimerize and obtain the (trans / cis) trans / cis-butenedioic acid ester represented by structural formula B; subsequently, B and the reducing agent [H] undergo a hydrogenation reaction under reaction conditions to obtain the succinate product represented by structural formula C. Alternatively, as shown in reaction (II), succinate product C is prepared by condensation of glycolate type A and acetate D under reaction conditions: R1, R2, or R3 are independent of each other and are hydrogen or aliphatic or aromatic hydrocarbon groups containing 1-24 carbon atoms; preferably, R1, R2, or R3 are hydrogen, methyl, ethyl, propyl, or butyl. Additive [P] is a catalyst or promoter of the reaction; preferably, the catalyst or promoter is a Lewis base or Lewis acid compound. Based on raw material A, the amount of additive [P] used is a catalytic amount, an equivalent amount, or an excess amount (0.001-100 equivalents). Preferably, the amount added is 0.1-1000% of the reactant; more preferably 1-200%, and even more preferably 1-100%. 【H】 is any reducing agent capable of reducing a carbonyl group (C=O) to the corresponding methylene group (CH2); preferably hydrogen, isopropanol, formic acid, formate, silane, or a catalytic hydrogenation reduction agent system composed of a metal or non-metal catalyst. "conditions" refers to at least one of the following: solvent, light, heat, microwave, ultrasound, vacuum, or pressure.

2. A novel process for the preparation of 1,4-butanediol (BDO). As shown in reaction (II), the glycolate type substance of structural formula A and the additive [P] react under reaction conditions to dimerize and obtain the (trans / cis) trans / cis-butenedioate of structural formula B; then B and the reducing agent [H] undergo hydrogenation under reaction conditions to obtain the butanediol product of structural formula E (general formula III); or, glycolate A and acetate D are condensed under reaction conditions to prepare succinate product C, which then undergoes hydrogenation with the reducing agent [H] under reaction conditions to obtain the butanediol product of structural formula E (general formula IV):

3. A novel process for preparing malic acid (ester) and tartaric acid (ester). As shown in general reaction formula (V), glycolate A and oxidant [O] are oxidized under reaction conditions to obtain glyoxylate ester with structural formula F, which is then condensed with acetate D under reaction conditions to prepare malic acid (ester) product with structural formula G; and as shown in general reaction formula (VI), glyoxylate F and A undergo a condensation reaction under reaction conditions to obtain tartaric acid (ester) with structural formula H: The oxidizing agent [O] is any reagent capable of oxidizing the primary alcohol hydroxyl group in structure A to the corresponding aldehyde group; preferably, [O] is at least one of oxygen, hydrogen peroxide, hydrocarbon peroxide, nonmetallic (per)oxide, metallic (per)oxide, ozone, halogen, organic peroxyacid, metal heteropolyacid, dialkyl peroxide ketone (e.g., DMDO), organic NO radical oxide (e.g., 2,2,6,6-tetramethylpiperidine oxide TEMPO), oxalyl chloride-DMSO, haloamide (e.g., NCS or TCCA), metal (nitrite) anhydride, metal (hypo)halate, hydrocarbon hypohalate, etc.

4. A novel process for preparing malic acid (ester) and tartaric acid (ester). As shown in general reaction formula (VII), oxalate ester and glycolate ester A of structural formula I, along with additive [P], condense under reaction conditions to obtain keto ester of structural formula J, which then undergoes hydrogenation with reducing agent [H] under reaction conditions to obtain tartaric acid (ester) of structural formula H; and as shown in general reaction formula (VIII), oxalate ester I and acetate ester D, along with additive [P], condense under reaction conditions to obtain keto ester of structural formula K, which then undergoes hydrogenation with reducing agent [H] under reaction conditions to obtain malic acid (ester) of structural formula G.

5. According to claims (1-4), preferably, the Lewis base is a metal (hydro)oxide, hydride, alkoxide, alkane, or alkamine; a metal (hydrocarbonate), (hydrosulfate), (carboxylate), (oxalate), (nitrate), (hydrophosphate), or (sulfonate); ammonia, ammonia water; or an organic amine; preferably, the Lewis acid is hydrochloric acid, sulfuric acid, boric acid, nitric acid, phosphoric acid, sulfonic acid, oxalic acid, an organic carboxylic acid, a nonmetallic acid or oxide of different valence states, a metal halide, sulfide, or oxide; zeolite; molecular sieve; diatomaceous earth; or a heteropoly acid.

6. According to claims (1-4), the solvent is selected from at least one of substituted or unsubstituted aromatic hydrocarbons containing 1-24 carbon atoms, straight-chain or branched aliphatic hydrocarbons, (sulfoxide) sulfones, amides, ethers, alcohols, esters, ketones, nitriles, carboxylic acids, water, amines, carbonates, ionic liquids, and supercritical carbon dioxide; or the liquid substrate itself simultaneously acts as a solvent medium. Light refers to the reaction system being carried out under light irradiation conditions, with a wavelength range of 200-780 nanometers. Heat refers to the reaction system being carried out under heating conditions, with a reaction temperature of -25-450 degrees Celsius. Microwave or ultrasonic refers to irradiating the reaction system using a microwave or ultrasonic generator. Pressure or vacuum refers to the reaction system being carried out under pressure or a certain degree of vacuum, with the reaction process pressure ranging from 0.001 to 200 atmospheres.

7. According to claim (1), preferably, one embodiment of general formula (I) is (IA), that is, methyl glycolate is used as a raw material and additive [P] to undergo dimerization under reaction conditions to obtain methyl butenedioate, which is then hydrogenated to obtain methyl succinate (preferably R2 is hydrogen or methyl):

8. According to claim (1), preferably, one embodiment of general formula (II) is (IIA), namely, methyl glycolate as a raw material and methyl acetate and additive [P] undergo condensation under reaction conditions to obtain methyl succinate (preferably R2 is hydrogen or methyl):

9. According to claim (2), preferably, one embodiment of general formula (III) is (IIIA), namely, methyl glycolate is used as a raw material and additive [P] to undergo dimerization under reaction conditions to obtain methyl butadieneate, which is then reduced by hydrogenation to obtain butanediol (preferably R2 is hydrogen or methyl):

10. According to claim (2), preferably, one embodiment of general formula (IV) is (IVA), namely, methyl glycolate as a raw material and methyl acetate and additive [P] undergo condensation under reaction conditions to obtain methyl succinate (preferably R2 is hydrogen or methyl), which is further reduced by hydrogenation to obtain butanediol:

11. According to claim (3), preferably, one embodiment of general formula (V) is (VA), namely, methyl glycolate is oxidized with oxidant [O] under reaction conditions to obtain methyl glyoxylate, which is then condensed with acetate D to obtain malate product:

12. According to claim (3), preferably, one embodiment of general formula (VI) is (VIA), that is, methyl glycolate is oxidized with oxidant [O] under reaction conditions to obtain methyl glyoxylate, which is then condensed with methyl glycolate to obtain tartrate ester product:

13. According to claim (4), preferably, one embodiment of general formula (VII) is (VIIA), namely, condensing dimethyl oxalate and methyl glycolate as raw materials under reaction conditions to obtain methyl ketoate, which is then hydrogenated and reduced to obtain tartrate ester product (R2 is preferably hydrogen and methyl):

14. According to claim (4), preferably, one embodiment of general formula (VIII) is (VIIIA), namely, condensation of dimethyl oxalate and methyl acetate as raw materials under reaction conditions to obtain methyl ketoate, which is then hydrogenated and reduced to obtain malate product:

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