A preparation method of methyl ester compound

Abstract

The present application discloses a method for preparing methyl ester compounds, which comprises subjecting a raw material of a carboxyl compound, methanol and / or dimethyl ether to an esterification reaction to obtain a methyl ester compound; wherein the general formula I of the carboxyl compound is R-CH2-COOH, and R is a methoxy group or a hydroxyl group; and the methyl ester compound comprises at least one of methyl methoxyacetate and methyl glycolate. The present application also discloses a method for preparing methyl glycolate, comprising the steps of: a) subjecting methylal to a carbonylation reaction with carbon monoxide to obtain methyl methoxyacetate; b) subjecting methyl methoxyacetate to a hydrolysis reaction with water to obtain methyl glycolate; and c) subjecting glycolic acid and methoxyacetic acid to an esterification reaction with methanol and dimethyl ether to obtain methyl glycolate. The above method can greatly simplify the separation process, save energy consumption, and provide a new synthetic route for the synthesis of methyl ester compounds, especially methyl glycolate.

Description

Technical Field

[0001] The present application relates to a method for preparing a methyl ester compound, and belongs to the field of catalytic chemistry. Background Art

[0002] Methyl glycolate (HOCH2COOCH3, MG) is an important platform compound. Ethylene glycol can be produced through hydrogenation, glycolic acid can be prepared through hydrolysis, and polyglycolic acid (PGA) can be synthesized through polymerization. Ethylene glycol is a monomer in the widely used polyethylene terephthalate (PET) material, enjoying high market demand. Glycolic acid is an excellent chemical cleaning agent and cosmetics raw material and can also polymerize to produce PGA. On January 1, 2021, the strictest plastic restriction order in history officially came into effect in China. Disposable, non-degradable plastic straws and packaging are now banned. The shift to greener, more environmentally friendly materials is becoming increasingly important, and the biodegradable plastics industry has recently become a hot topic in the market. Polyglycolic acid (PGA) is the simplest linear polyester among polyhydroxyalkanoates (POHLAs). It is a fully biodegradable material and can be synthesized by condensing monomers such as methyl glycolate and glycolic acid. It degrades rapidly in the natural environment under the action of water and microorganisms, with carbon dioxide and water as the final degradation products. In addition, PGA can be degraded in seawater, and its degradation products are harmless to the human body and the environment.

[0003] Methyl glycolate can be produced through the formaldehyde carbonylation process. Although the raw materials are inexpensive and readily available, the process requires high temperature, high pressure, strong liquid acid, and organic solvents. Equipment is susceptible to corrosion, and product purification is difficult, resulting in high industrial production costs. In recent years, with the large-scale industrial application of "coal-to-ethylene glycol" technology, the method of partially hydrogenating the intermediate product dimethyl oxalate to produce methyl glycolate has garnered widespread attention. However, on the one hand, the catalyst for the partial hydrogenation of dimethyl oxalate is still immature, resulting in low conversion efficiency and poor stability; on the other hand, the production process of dimethyl oxalate is long and costly, which seriously restricts the development of this method. Currently, the industrial production technology of methyl glycolate monomer is still immature, resulting in insufficient production capacity and high prices for PGA plastics, limiting its large-scale alternative application. Summary of the Invention

[0004] In order to overcome the defects in the prior art, the present application provides a green, economical and efficient synthesis technology route for methyl ester compounds, especially methyl glycolate.

[0005] According to one aspect of the present application, a method for preparing a methyl ester compound is provided. A raw material containing methoxyacetic acid, methanol, and / or dimethyl ether is passed through a reactor to undergo an esterification reaction to produce a product containing methyl methoxyacetate. The readily performed esterification reaction of methoxyacetic acid with glycolic acid not only increases the yield of methyl glycolate but also eliminates the need for separation of methoxyacetic acid and glycolic acid, significantly simplifying the separation process and saving energy.

[0006] As one specific embodiment, the method for esterifying methoxyacetic acid and glycolic acid described in the present application is to pass raw materials containing methoxyacetic acid, glycolic acid, methanol and dimethyl ether through a reactor, and undergo esterification reaction under predetermined reaction conditions to produce methyl methoxyacetate and methyl glycolate.

[0007] According to the hydrolysis reaction mechanism, the hydrolysis of methyl methoxyacetate can produce not only the target product methyl glycolate, but also other hydrolysis products such as methoxyacetic acid, glycolic acid, methanol, and dimethyl ether. Since methoxyacetic acid is relatively limited in use and the purification of low-concentration glycolic acid is energy-intensive, methyl methoxyacetate and methyl glycolate can be further produced through a readily accessible esterification reaction. This not only increases the yield of methyl glycolate but also significantly simplifies the separation process, saving energy.

[0008] The esterification reaction mainly includes the following reactions:

[0009] CH3OCH2COOH+CH3OH=CH3OCH2COOCH3+H2O

[0010] HOCH2COOH+CH3OH=HOCH2COOCH3

[0011] CH3OCH2COOH+CH3OCH3=CH3OCH2COOCH3+CH3OH

[0012] HOCH2COOH+CH3OCH3=HOCH2COOCH3+CH3OH

[0013] The esterification method comprises passing a raw material containing a carboxyl compound, methanol and / or dimethyl ether through a reactor to undergo an esterification reaction to obtain a methyl ester compound;

[0014] Wherein, the carboxyl compound is selected from at least one compound represented by formula I;

[0015] R-CH2-COOH Formula I

[0016] R is methoxy or hydroxy;

[0017] The methyl ester compound includes at least one of methyl methoxyacetate and methyl glycolate.

[0018] Optionally, the esterification reaction conditions are: reaction temperature 40-300° C., reaction pressure 0.1-0.5 MPa.

[0019] The esterification reaction is carried out in the absence of a catalyst or in the presence of an esterification catalyst.

[0020] The esterification catalyst is a solid catalyst that is insoluble in raw materials and products.

[0021] Optionally, the solid catalyst is at least one of an acidic molecular sieve and an acidic cation exchange resin.

[0022] Optionally, the esterification reaction is carried out on one of the following inert components: at least one of quartz sand, aluminum oxide, silicon oxide, silicon carbide, glass, and ceramics.

[0023] As one specific embodiment, the reactor does not carry any catalyst, or carries a solid catalyst that is insoluble in the raw materials and products.

[0024] Optionally, in the esterification reaction of methoxyacetic acid and glycolic acid, methoxyacetic acid and glycolic acid themselves can serve as catalysts, which is an autocatalytic reaction, and thus no catalyst is required.

[0025] Optionally, the solid catalyst insoluble in the raw materials and the product includes an acidic solid catalyst and a non-acidic solid catalyst. The non-acidic solid catalyst mainly promotes the mixing and dispersion of the materials; the acidic solid catalyst not only has the above functions but also can catalyze the esterification reaction.

[0026] Optionally, the solid catalyst insoluble in the raw material and the product is spherical or cylindrical.

[0027] Optionally, the raw material is methoxyacetic acid, methanol and / or dimethyl ether; or

[0028] The raw materials are glycolic acid, methanol and / or dimethyl ether; or

[0029] The raw materials are methoxyacetic acid, glycolic acid and methanol; or

[0030] The raw materials are methoxyacetic acid, glycolic acid and dimethyl ether; or

[0031] The raw materials are methoxyacetic acid, glycolic acid, methanol and dimethyl ether.

[0032] Optionally, the product also includes methyl glycolate.

[0033] As a specific embodiment, the molar ratio of methoxyacetic acid, glycolic acid, methanol and dimethyl ether in the raw materials is any ratio.

[0034] Optionally, the feedstock includes methoxyacetic acid, glycolic acid, methanol and dimethyl ether;

[0035] The molar ratio of methoxyacetic acid to glycolic acid in the raw materials is 3:1 to 10:1, and the molar ratio of (methanol+dimethyl ether) / (methoxyacetic acid+glycolic acid) is 1:1 to 5:1.

[0036] Optionally, the raw material does not contain methanol, the molar ratio of methoxyacetic acid / glycolic acid is 3:1 to 10:1, and the molar ratio of dimethyl ether / (methoxyacetic acid+glycolic acid) is 1:1 to 5:1.

[0037] Optionally, the raw material does not contain methanol and glycolic acid, and the molar ratio of dimethyl ether to methoxyacetic acid is 1:1 to 5:1.

[0038] Optionally, the raw material does not contain dimethyl ether,

[0039] The molar ratio of methoxyacetic acid to glycolic acid is 3:1 to 10:1, and the molar ratio of methanol to (methoxyacetic acid + glycolic acid) is 1:1 to 5:1.

[0040] Alternatively, the reaction temperature can be selected from any value of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C and 300°C, or any range therebetween.

[0041] Alternatively, the reaction pressure may be selected from any value among 0.1 MPa, 0.15 MPa, 0.20 MPa, 0.25 MPa, 0.30 MPa, 0.35 MPa, 0.40 MPa, 0.45 MPa and 0.50 MPa, or a range determined by any two values.

[0042] Alternatively, the molar ratio of methoxyacetic acid to glycolic acid may be selected from any value of 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 and 10:1, or a range determined by any two values.

[0043] Optionally, the (methanol + dimethyl ether) / (methoxyacetic acid + glycolic acid) molar ratio is any value among 0.5:1, 1.0:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1, 5.0:1, 5.5:1, 6.0:1, 6.5:1, 7.0:1, 7.5:1 and 8.0:1, or a range determined by any two values.

[0044] Optionally, the raw material does not contain methanol or dimethyl ether, and the molar ratio of methoxyacetic acid / glycolic acid can be selected from any value of 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, 9:1, 9.5:1 and 10:1, or a range determined by any two values.

[0045] Optionally, the dimethyl ether (or methanol) / (methoxyacetic acid+glycolic acid) molar ratio is any value selected from 1:1, 1.5:1, 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1 and 5.0:1, or a range determined by any two values.

[0046] Optionally, the raw material is generated by hydrolysis of methyl methoxyacetate.

[0047] Alternatively, the feedstock containing methoxyacetic acid, glycolic acid, methanol and dimethyl ether is produced by hydrolysis of methyl methoxyacetate.

[0048] Optionally, the reactor is a fixed bed reactor or a tank reactor.

[0049] The reactor is preferably a fixed bed reactor.

[0050] As one specific embodiment, the reaction process includes a carrier gas, and the carrier gas includes at least one of nitrogen, argon, helium, hydrogen, carbon monoxide, and carbon dioxide.

[0051] According to the second aspect of the present application, the present application provides a method for preparing methyl glycolate, the method comprising the following steps:

[0052] a) passing a feedstock containing methylal and carbon monoxide through a reactor carrying an acidic molecular sieve catalyst to undergo carbonylation reaction under predetermined conditions to produce a product containing methyl methoxyacetate, dimethyl ether and methyl formate, which is then separated to obtain methyl methoxyacetate;

[0053] b) passing the raw material containing the methyl methoxyacetate obtained in step a) and water through a reactor loaded with an acidic molecular sieve catalyst to carry out a hydrolysis reaction under predetermined conditions to generate a product containing methyl glycolate, glycolic acid, methoxyacetic acid, methanol and dimethyl ether, which is separated to obtain methyl glycolate; and

[0054] c) passing the glycolic acid and methoxyacetic acid obtained in step b) into a reactor with methanol and dimethyl ether to carry out an esterification reaction under predetermined conditions to generate products containing methyl methoxyacetate and methyl glycolate, which are then separated to obtain methyl glycolate.

[0055] The technical route composed of the combination of steps a) to c) provides an industrially applicable route for synthesizing methyl glycolate.

[0056] Wherein, the methylal carbonylation reaction in step a) mainly includes the following reactions:

[0057] CH3OCH2OCH3+CO=CH3OCH2COOCH3 (1)

[0058] 2CH3OCH2OCH3=2CH3OCH3+HCOOCH3 (2)

[0059] The methoxyacetic acid methyl ester hydrolysis reaction in step b) mainly includes the following reactions:

[0060] CH3OCH2COOCH3+H2O=HOCH2COOCH3+CH3OH (3)

[0061] CH3OCH2COOCH3+H2O=CH3OCH2COOH+CH3OH (4)

[0062] CH3OCH2COOCH3+2H2O=HOCH2COOH+2CH3OH (5)

[0063] 2CH3OH=CH3OCH3+H2O (6)

[0064] The esterification reaction in step c) mainly includes the following reactions:

[0065] CH3OCH2COOH+CH3OH=CH3OCH2COOCH3+H2O (7)

[0066] HOCH2COOH+CH3OH=HOCH2COOCH3 (8)

[0067] CH3OCH2COOH+CH3OCH3=CH3OCH2COOCH3+CH3OH (9)

[0068] HOCH2COOH+CH3OCH3=HOCH2COOCH3+CH3OH (10)

[0069] The above reactions (3) to (10) are reversible.

[0070] The dimethyl ether and methanol obtained by the separation systems a) and b) can be used to prepare methylal. The reactions involved are:

[0071] 2CH3OH+O2=2HCHO+2H2O (11)

[0072] CH3OCH3+O2=2HCHO+H2O (12)

[0073] 2CH3OH+HCHO=CH3OCH2OCH3+H2O (13)

[0074] From the above reactions (1)-(13), it can be seen that by combining the reactions of methylal synthesis, methylal carbonylation, methyl methoxyacetate hydrolysis, and esterification of methoxyacetic acid with glycolic acid, methyl glycolate can be synthesized using methanol, carbon monoxide, and oxygen. The overall reaction equation is as follows:

[0075] 4CH3OH+O2+2CO=2HOCH2COOCH3+2H2O (14)

[0076] In summary, the technical route composed of the combination of steps a) to c) can fully utilize non-target products, with only methyl formate (HCOOCH3) with very low selectivity as a by-product.

[0077] Optionally, the method further comprises step a'): returning the unreacted methylal and carbon monoxide in step a) to the reactor in step a) to continue the carbonylation reaction.

[0078] Optionally, the method further comprises step b'): returning the unreacted methyl methoxyacetate in step b) to the reactor in step b) to continue the hydrolysis reaction with water.

[0079] Optionally, the method further comprises step c'): introducing the product methyl methoxyacetate obtained in step c) into the reactor of step b) to carry out a hydrolysis reaction with water.

[0080] Optionally, the acidic molecular sieve catalyst in step a) or step b) is selected from at least one of an acidic molecular sieve having an MFI structure, an acidic molecular sieve having a Y structure, an acidic molecular sieve having a FER structure, an acidic molecular sieve having a BEA structure, an acidic molecular sieve having a MOR structure, and an acidic molecular sieve having an MWW structure.

[0081] Optionally, the acidic molecular sieve catalyst in step a) or step b) is at least one of hydrogenated ZSM-5 molecular sieve, hydrogenated Y molecular sieve, hydrogenated ZSM-35 molecular sieve, hydrogenated β molecular sieve, hydrogenated mordenite molecular sieve, and hydrogenated MCM-22 molecular sieve.

[0082] Optionally, step a) or step b) further comprises introducing a carrier gas into the reactor, wherein the carrier gas comprises at least one of nitrogen, argon, helium, hydrogen, carbon monoxide, and carbon dioxide in any amount.

[0083] Optionally, the reaction conditions in step a) are: reaction temperature of 60-140° C., reaction pressure of 2-10 MPa, and methylal mass space velocity of 0.2-10.0 h -1 , the molar ratio of carbon monoxide to methylal is 2:1 to 20:1.

[0084] Optionally, the reaction temperature in step a) is any value of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 100°C, 110°C, 120°C, 130°C and 140°C, or a range determined by any two values.

[0085] Optionally, the reaction pressure in step a) is any value of 2 MPa, 2.5 MPa, 3.0 MPa, 3.5 MPa, 4.0 MPa, 4.5 MPa, 5.0 MPa, 5.5 MPa, 6.0 MPa, 6.5 MPa, 7.0 MPa, 7.5 MPa, 8.0 MPa, 8.5 MPa, 9.0 MPa, 9.5 MPa and 10.0 MPa, or a range determined by any two values.

[0086] Optionally, the methylal mass space velocity in step a) is 0.2h -1 , 0.5h -1 , 0.8h -1 , 1.0h -1 , 1.5h -1 , 2.0h -1 , 2.5h -1 , 3.0h -1 , 3.5h -1 , 4.0h -1 , 4.5h -1 , 5.0h -1 , 5.5h -1 , 6.0h -1 , 6.5h -1 , 7.0h -1 , 7.5h -1 , 8.0h -1 , 8.5h -1 , 9.0h -1 , 9.5h -1 and 10.0h -1 Any value or a range of values ​​determined by any two values.

[0087] Optionally, the molar ratio of carbon monoxide to methylal in step a) is any value among 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, 13:1, 14:1, 15:1, 16:1, 17:1, 18:1, 19:1 and 20:1, or a range determined by any two values.

[0088] Optionally, the reaction conditions in step b) are: reaction temperature of 140-220° C., reaction pressure of 0.1-0.5 MPa, mass space velocity of methyl methoxyacetate of 0.1-3.0 h -1 , the molar ratio of water to methyl methoxyacetate is 0.5:1 to 8:1.

[0089] Optionally, the reaction conditions in step c) are: reaction temperature of 40-300° C., reaction pressure of 0.1-0.5 MPa, and a molar ratio of (methanol+dimethyl ether) / (glycolic acid+methoxyacetic acid) of 0.5:1-8:1.

[0090] Optionally, the reaction state in step a) is a gas-liquid-solid three-phase reaction state.

[0091] Optionally, the esterification reaction in step c) is carried out in the absence of a catalyst or in the presence of an esterification catalyst.

[0092] Optionally, the esterification catalyst is a solid catalyst that is insoluble in the raw materials and products.

[0093] Optionally, the solid catalyst is at least one of an acidic molecular sieve and an acidic cation exchange resin;

[0094] Optionally, the esterification reaction is carried out on one of the following inert components: at least one of quartz sand, aluminum oxide, silicon oxide, silicon carbide, glass, and ceramics.

[0095] Preferably, the esterification reaction is carried out on quartz sand.

[0096] The present invention relates to the core part of the technical route such as Figure 1 As shown in Figure 2, the reactor used for the carbonylation reaction is loaded with an acidic molecular sieve catalyst, while the hydrolysis reactor used for the hydrolysis reaction is loaded with an acidic molecular sieve catalyst. The esterification reaction is an autocatalytic reaction, and to enhance mass transfer, the esterification reactor can be loaded with inert quartz sand particles.

[0097] Optionally, the carbonylation reactor comprises a fixed bed reactor, or may comprise a plurality of fixed bed reactors connected in parallel or in series. In order to facilitate the removal of reaction heat, the carbonylation reactor is generally a shell-and-tube fixed bed reactor.

[0098] Optionally, the hydrolysis reactor comprises a fixed bed reactor, or may comprise a plurality of fixed bed reactors connected in parallel or in series. The hydrolysis reactor is generally a selective adiabatic fixed bed reactor.

[0099] The separation system used to separate carbonylation products includes chemical equipment such as gas-liquid separation tanks and distillation towers commonly used in chemical separation units.

[0100] The separation system used to separate the hydrolyzate also includes chemical equipment such as gas-liquid separation tanks and distillation towers commonly used in chemical separation units.

[0101] Since the types of hydrolyzed products already include all esterification products, they can share a common separation system.

[0102] The beneficial effects of this application include:

[0103] (1) The method described in this application is simple, efficient and easy to operate.

[0104] (2) The easy esterification reaction of methoxyacetic acid and glycolic acid not only increases the yield of methyl glycolate, but also eliminates the need to separate methoxyacetic acid and glycolic acid; this can greatly simplify the separation process and save energy.

[0105] (3) The present invention provides a novel synthetic route for methyl glycolate, which has mild reaction conditions, low by-product selectivity, high selectivity for the target product methyl glycolate, and strong atom economy. The reaction and separation equipment used in this route are all conventional equipment, which is convenient for single-set large-scale production. This route does not introduce raw materials and catalysts containing elements such as sulfur, nitrogen, and chlorine, and the product methyl glycolate is of high quality. The catalysts used in this route are all acidic molecular sieve catalysts, and expensive precious metal catalysts are not required. BRIEF DESCRIPTION OF THE DRAWINGS

[0106] Figure 1 The figure is a simplified flow chart of the synthetic route of methyl glycolate in this application. DETAILED DESCRIPTION

[0107] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0108] The endpoints of the ranges disclosed in this application and any values ​​are not limited to the exact ranges or values, and these ranges or values ​​should be understood to include approximate ranges or values. For numerical ranges, the endpoints of each range and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0109] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0110] Unless otherwise specified, the raw materials and catalysts in the examples of this application were purchased from commercial sources.

[0111] The key technologies involved in the present invention are Figure 1 The three reactions of carbonylation, hydrolysis and esterification are shown in FIG, so they are described in detail with examples.

[0112] 1) The analytical method for the carbonylation reaction of methylal is as follows:

[0113] The product and unreacted raw material were analyzed using an Agilent 7890A gas chromatograph with an FID detector connected to a DB-FFAP capillary column and a TCD detector connected to a Porapak Q packed column. The reaction product passed through a back pressure valve, heated to a vapor state, and then entered into a chromatographic online analysis. Conversion and selectivity were calculated based on the molar number of carbon atoms in methylal:

[0114] Methylal conversion rate = [(mole number of carbon methylal in the raw material) - (mole number of carbon methylal in the product)] ÷ (mole number of carbon methylal in the raw material) × (100%)

[0115] Methyl methoxyacetate selectivity = (the number of moles of carbon in the product after the carbonyl group is removed from methyl methoxyacetate) ÷ [(the number of moles of carbon in the raw material) - (the number of moles of carbon in the product)] × (100%)

[0116] Dimethyl ether selectivity = (moles of dimethyl ether carbon in the product) ÷ [(moles of methylal carbon in the feed) - (moles of methylal carbon in the product)] × (100%)

[0117] Methyl formate selectivity = (mole number of carbon atoms of methyl formate in the product) ÷ [(mole number of carbon atoms of methylal in the feedstock) - (mole number of carbon atoms of methylal in the product)] × (100%)

[0118] 2) The analytical method for the hydrolysis reaction of methyl methoxyacetate is as follows:

[0119] The products other than glycolic acid and the unreacted raw materials were analyzed by Agilent 7890B gas chromatograph, with its FID detector connected to a DB-FFAP capillary column and its TCD detector connected to a Porapak Q packed column. Glycolic acid was analyzed by liquid chromatography, with a separation column of C 18 The conversion rate and selectivity are calculated based on the molar number of carbon:

[0120] Methyl methoxyacetate conversion rate = [(mole number of carbon atoms of methyl methoxyacetate in the feed) - (mole number of carbon atoms of methyl methoxyacetate in the discharge)] ÷ (mole number of carbon atoms of methyl methoxyacetate in the feed) × 100%

[0121] Methyl glycolate selectivity = [(mole number of carbon atoms of methyl glycolate in the output)] ÷ [(mole number of carbon atoms of methyl methoxyacetate in the feed) - (mole number of carbon atoms of methyl methoxyacetate in the output)] × 100%

[0122] Methoxyacetic acid selectivity = [(mole number of carbon atoms of methoxyacetic acid in the output)] ÷ [(mole number of carbon atoms of methyl methoxyacetate in the feed) - (mole number of carbon atoms of methyl methoxyacetate in the output)] × 100%

[0123] Glycolic acid selectivity = [(moles of glycolic acid carbon in the output)] ÷ [(moles of methyl methoxyacetate carbon in the feed) - (moles of methyl methoxyacetate carbon in the output)] × 100%

[0124] Methanol selectivity = [(mole number of methanol carbon in the output)] ÷ [(mole number of methyl methoxyacetate carbon in the feed) - (mole number of methyl methoxyacetate carbon in the output)] × 100%

[0125] Dimethyl ether selectivity = [(mole number of carbon atoms in dimethyl ether in the output)] ÷ [(mole number of carbon atoms in methyl methoxyacetate in the feed) - (mole number of carbon atoms in methyl methoxyacetate in the output)] × 100%

[0126] 3) The analysis method of esterification reaction is as follows:

[0127] The products other than glycolic acid and the unreacted raw materials were analyzed by Agilent 7890B gas chromatograph, with its FID detector connected to a DB-FFAP capillary column and its TCD detector connected to a Porapak Q packed column. Glycolic acid was analyzed by liquid chromatography, with a separation column of C 18 The column was used, and the detector was a UV detector. Considering that methoxyacetic acid was directional esterified to methyl methoxyacetate and glycolic acid was directional esterified to methyl glycolate, only the conversion rates of methoxyacetic acid and glycolic acid were calculated for the esterification reaction results.

[0128] Glycolic acid conversion rate = [(moles of glycolic acid in the feed) - (moles of glycolic acid in the output)] ÷ (moles of glycolic acid in the feed) × 100%

[0129] Methoxyacetic acid conversion rate = [(mole number of methoxyacetic acid in feed) - (mole number of methoxyacetic acid in discharge)] ÷ (mole number of methoxyacetic acid in feed) × 100%

[0130] Example 1

[0131] 300g of acidic H-β molecular sieve (SiO2 / Al2O3=150) was filled into a In the fixed bed reactor, there is Thermocouple tube. Methylal and carbon monoxide undergo carbonylation reaction over the catalyst bed. The product passes through a back pressure valve and vaporizes into a gas chromatograph for online analysis. Reaction conditions are: reaction temperature = 68°C, reaction pressure = 6 MPa, and methylal mass space velocity = 0.7 h -1The molar ratio of carbon monoxide to methylal was 10: 1. After 5 days of operation, the reaction results are shown in Table 1.

[0132] Example 2

[0133] 300g of acidic HY molecular sieve (SiO2 / Al2O3=25) was filled into a In the fixed bed reactor, there is Thermocouple tube. Methylal and carbon monoxide undergo carbonylation reaction over the catalyst bed. The product passes through a back pressure valve and vaporizes into a gas chromatograph for online analysis. Reaction conditions are: reaction temperature = 90°C, reaction pressure = 5 MPa, and methylal mass space velocity = 1.0 h -1 The molar ratio of carbon monoxide to methylal was 7:1. After 5 days of operation, the reaction results are shown in Table 1.

[0134] Example 3

[0135] 300g of acidic H-ZSM-5 molecular sieve (SiO2 / Al2O3=180) was filled into a In the fixed bed reactor, there is Thermocouple tube. Methylal and carbon monoxide undergo carbonylation reaction over the catalyst bed. The product passes through a back pressure valve and vaporizes into a gas chromatograph for online analysis. Reaction conditions are: reaction temperature = 80°C, reaction pressure = 8 MPa, and methylal mass space velocity = 1.2 h -1 The molar ratio of carbon monoxide to methylal was 5: 1. After 5 days of operation, the reaction results are shown in Table 1.

[0136] Table 1 Results of carbonylation reaction of methylal in Examples 1 to 3

[0137] Example Methylal conversion rate (%) Methyl methoxyacetate selectivity (%) Dimethyl ether selectivity (%) Methyl formate selectivity (%) 1 64.2 86.9 7.8 3.6 2 49.8 88.8 6.8 3.2 3 40.4 80.2 12.0 5.5

[0138] In the present application, the methylal and carbon monoxide not converted in Examples 1 to 3 can be Figure 1 The raw materials are recycled to the carbonylation reactor for carbonylation reaction to fully utilize the raw materials and improve the utilization rate of the raw materials.

[0139] Example 4

[0140] 300g of acidic H-ZSM-5 molecular sieve (SiO2 / Al2O3=30) catalyst was loaded into a In the fixed bed reactor, there is The methyl methoxyacetate prepared in Examples 1 to 3 was separated and hydrolyzed with water over a catalyst bed. The product was collected by condensation, weighed, and analyzed by gas chromatography and liquid chromatography. Non-condensable gases were analyzed online by gas chromatography. The reaction conditions were: reaction temperature = 180°C, reaction pressure = 0.1 MPa, and methyl methoxyacetate mass space velocity = 1.5 h -1 The molar ratio of water to methyl methoxyacetate was 2:1, and the carrier gas hydrogen flow rate was 1.5 L / min. After 5 days of operation, the reaction results are shown in Table 2.

[0141] Example 5

[0142] 300g of acidic H-ZSM-35 molecular sieve (SiO2 / Al2O3=20) catalyst was loaded into a In the fixed bed reactor, there is The methyl methoxyacetate prepared in Examples 1 to 3 was separated and hydrolyzed with water over a catalyst bed. The product was collected by condensation, weighed, and analyzed by gas chromatography and liquid chromatography. Non-condensable gases were analyzed online by gas chromatography. The reaction conditions were: reaction temperature = 170°C, reaction pressure = 0.12 MPa, and methyl methoxyacetate mass space velocity = 0.5 h -1 The molar ratio of water to methyl methoxyacetate was 1:1, and the carrier gas hydrogen flow rate was 1.5 L / min. After 5 days of operation, the reaction results are shown in Table 2.

[0143] Example 6

[0144] 300g of acidic H-MCM-22 molecular sieve (SiO2 / Al2O3=40) catalyst was loaded into a In the fixed bed reactor, there is The methyl methoxyacetate prepared in Examples 1 to 3 was separated and hydrolyzed with water over a catalyst bed. The product was collected by condensation, weighed, and analyzed by gas chromatography and liquid chromatography. Non-condensable gases were analyzed online by gas chromatography. The reaction conditions were: reaction temperature = 190°C, reaction pressure = 0.2 MPa, and methyl methoxyacetate mass space velocity = 0.4 h -1 The molar ratio of water to methyl methoxyacetate was 3:1, and the carrier gas hydrogen flow rate was 1.5 L / min. After 5 days of operation, the reaction results are shown in Table 2.

[0145] Table 2 Results of hydrolysis of methyl methoxyacetate in Examples 4 to 6

[0146]

[0147] In this application, the methyl methoxyacetate that has not been converted in Examples 4 to 6 can be Figure 1 The raw materials are circulated to the hydrolysis reactor for hydrolysis reaction to fully utilize the raw materials and improve the utilization rate of the raw materials.

[0148] Example 7

[0149] 300 g of quartz sand particles with a particle size of 3 mm were loaded into a fixed-bed reactor with an inner diameter of φ36 mm. A φ6 mm thermowell was installed inside the reactor. The methoxyacetic acid, glycolic acid, methanol, and dimethyl ether prepared in Examples 4 to 6 were separated and then passed through a quartz sand bed for esterification. The product was collected by condensation, weighed, and analyzed by gas chromatography and liquid chromatography. The non-condensable gas was analyzed online by gas chromatography. The reaction conditions were: reaction temperature = 180°C, reaction pressure = 0.1 MPa, methoxyacetic acid flow rate = 120 g / h, methoxyacetic acid: glycolic acid: methanol: dimethyl ether (molar ratio) = 5:1:10:10. After 5 days of operation, the reaction results are shown in Table 3.

[0150] Example 8

[0151] 300 g of 3 mm silica particles were loaded into a fixed-bed reactor with an inner diameter of φ36 mm. A φ6 mm thermowell was installed inside the reactor. The methoxyacetic acid and glycolic acid prepared in Examples 4 to 6 were separated and then esterified with dimethyl ether over a silica bed. The product was collected by condensation, weighed, and analyzed by gas chromatography and liquid chromatography. Non-condensable gases were analyzed online by gas chromatography. The reaction conditions were: reaction temperature = 200°C, reaction pressure = 0.5 MPa, methoxyacetic acid flow rate = 120 g / h, and methoxyacetic acid: glycolic acid: dimethyl ether (molar ratio) = 6:1:7. After 5 days of operation, the reaction results are shown in Table 3.

[0152] Example 9

[0153] 300 g of 3 mm glass particles were loaded into a fixed-bed reactor with an inner diameter of φ36 mm and a φ6 mm thermowell inside the reactor. The methoxyacetic acid and glycolic acid prepared in Examples 4 to 6 were separated and then esterified with dimethyl ether over a glass bed. The product was collected by condensation, weighed, and analyzed by gas chromatography and liquid chromatography. Non-condensable gases were analyzed online by gas chromatography. The reaction conditions were: reaction temperature = 300°C, reaction pressure = 0.2 MPa, methoxyacetic acid flow rate = 120 g / h, and methoxyacetic acid: glycolic acid: dimethyl ether (molar ratio) = 5:1:8. After 5 days of operation, the reaction results are shown in Table 3.

[0154] Example 10

[0155] Methoxyacetic acid, glycolic acid, and methanol were charged to a 1L reactor at 40°C, 0.1 MPa, 50 g of methoxyacetic acid, and a molar ratio of methoxyacetic acid:glycolic acid:methanol of 5:1:10. Magnetic stirring was used. After 4 hours, the reaction results are shown in Table 3.

[0156] Example 11

[0157] The methoxyacetic acid, glycolic acid, and methanol prepared in Examples 4 to 6 were separated and charged into a 1 L reactor. The reaction temperature was 90°C, the pressure was 0.1 MPa, the mass of methoxyacetic acid was 50 g, and the D001 strong acid cation exchange resin (Dandong Mingzhu Company) was 5 g. The molar ratio of methoxyacetic acid:glycolic acid:methanol was 5:1:10, and magnetic stirring was used. After 4 hours of operation, the reaction results are shown in Table 1.

[0158] Table 3 Esterification reaction results of Examples 7-11

[0159] Example Methoxyacetic acid conversion rate (%) Glycolic acid conversion rate (%) 7 75.5 99.5 8 80.4 99.1 9 94.8 99.6 10 35.8 80.2 11 82.2 96.7

[0160] In the present application, the methyl methoxyacetate obtained in Examples 7 to 11 can be recycled to the hydrolysis reactor for the hydrolysis reaction to fully utilize the product and improve atom economy.

[0161] The above descriptions are merely a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application discloses the preferred embodiments as above, they are not intended to limit the present application. Any technical personnel familiar with the present profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing methyl glycolate, characterized in that: The method comprises the following steps: a) passing a feedstock containing methylal and carbon monoxide through a reactor carrying an acidic molecular sieve catalyst to undergo carbonylation reaction under predetermined conditions to produce a product containing methyl methoxyacetate, dimethyl ether and methyl formate, which is then separated to obtain methyl methoxyacetate; b) passing the raw material containing the methyl methoxyacetate obtained in step a) and water through a reactor loaded with an acidic molecular sieve catalyst to carry out a hydrolysis reaction under predetermined conditions to generate a product containing methyl glycolate, glycolic acid, methoxyacetic acid, methanol and dimethyl ether, which is separated to obtain methyl glycolate; and c) passing the glycolic acid and methoxyacetic acid obtained in step b) into a reactor with methanol and dimethyl ether to carry out an esterification reaction under predetermined conditions to generate products containing methyl methoxyacetate and methyl glycolate, which are then separated to obtain methyl glycolate.

2. The method according to claim 1, characterized in that The method further comprises step a'): returning the unreacted methylal and carbon monoxide in step a) to the reactor in step a) to continue the carbonylation reaction.

3. The method according to claim 1, characterized in that The method further comprises step b'): returning the unreacted methyl methoxyacetate in step b) to the reactor of step b) to continue the hydrolysis reaction with water.

4. The method according to claim 1, wherein The method further comprises step c'): introducing the product methyl methoxyacetate obtained in step c) into the reactor of step b) to undergo a hydrolysis reaction with water.

5. The method according to claim 1, wherein The acidic molecular sieve catalyst in step a) or step b) is selected from at least one of an acidic molecular sieve having an MFI structure, an acidic molecular sieve having a Y structure, an acidic molecular sieve having a FER structure, an acidic molecular sieve having a BEA structure, an acidic molecular sieve having a MOR structure, and an acidic molecular sieve having an MWW structure.

6. The method according to claim 1, characterized in that The acidic molecular sieve catalyst in step a) or step b) is at least one of hydrogenated ZSM-5 molecular sieve, hydrogenated Y molecular sieve, hydrogenated ZSM-35 molecular sieve, hydrogenated β molecular sieve, hydrogenated mordenite molecular sieve and hydrogenated MCM-22 molecular sieve.

7. The method according to claim 1, characterized in that Step a) or step b) further comprises introducing a carrier gas into the reactor, wherein the carrier gas comprises at least one of nitrogen, argon, helium, hydrogen, carbon monoxide, and carbon dioxide in any amount.

8. The method according to claim 1, characterized in that The reaction conditions in step a) are: reaction temperature of 60-140°C, reaction pressure of 2-10 MPa, and methylal mass space velocity of 0.2-10.0 h -1 , the molar ratio of carbon monoxide to methylal is 2:1 to 20:

1.

9. The method according to claim 1, characterized in that The reaction conditions in step b) are: reaction temperature of 140-220°C, reaction pressure of 0.1-0.5 MPa, mass space velocity of methyl methoxyacetate of 0.1-3.0 h -1 , the molar ratio of water to methyl methoxyacetate is 0.5:1 to 8:

1.

10. The method according to claim 1, characterized in that The reaction conditions in step c) are: reaction temperature of 40-300° C., reaction pressure of 0.1-0.5 MPa, and a molar ratio of (methanol+dimethyl ether) / (glycolic acid+methoxyacetic acid) of 0.5:1-8:

1.

11. The method according to claim 1, wherein The reaction state in step a) is a gas-liquid-solid three-phase reaction state.

12. The method according to claim 1, characterized in that The esterification reaction in step c) is carried out in the absence of a catalyst or in the presence of an esterification catalyst.

13. The method according to claim 1, wherein The esterification catalyst is a solid catalyst that is insoluble in raw materials and products.

14. The method according to claim 13, characterized in that The solid catalyst is at least one of an acidic molecular sieve and an acidic cation exchange resin.

15. The method according to claim 1, wherein The esterification reaction is carried out on one of the following inert components: at least one of quartz sand, aluminum oxide, silicon oxide, silicon carbide, glass, and ceramics.

Images