CN107586254B

CN107586254B - Method for synthesizing ethylene glycol by hydrogenating oxalate

Info

Publication number: CN107586254B
Application number: CN201610530368.8A
Authority: CN
Inventors: 徐恒泳; 葛庆杰; 马俊国; 孙剑; 周佳; 王伟; 夏锐; 夏伦超
Original assignee: Xinjiang Corps Modern Green Chlor Alkali Chemical Engineering Research Center Co ltd; Dalian Institute of Chemical Physics of CAS
Current assignee: Xinjiang Corps Modern Green Chlor Alkali Chemical Engineering Research Center Co ltd; Dalian Institute of Chemical Physics of CAS
Priority date: 2016-07-07
Filing date: 2016-07-07
Publication date: 2020-06-23
Anticipated expiration: 2036-07-07
Also published as: CN107586254A

Abstract

The invention relates to a method for synthesizing ethylene glycol by oxalate catalytic hydrogenation, which mainly solves the problems of low selectivity and short catalyst life in the catalytic reaction process of preparing ethylene glycol by oxalate hydrogenation. The catalyst of the present invention has copper or copper oxide as active component, hydrophilic silica or modified hydrophilic silica as carrier and proper metal oxide as assistant. The catalyst of the invention has higher reaction performance and reaction stability.

Description

Method for synthesizing ethylene glycol by hydrogenating oxalate

Technical Field

The invention relates to a method for preparing ethylene glycol by hydrogenating oxalate, which mainly solves the problems of low selectivity and short service life of a catalyst in the general catalytic reaction of preparing the ethylene glycol by hydrogenating oxalate.

Background

Ethylene Glycol (EG) as an important organic chemicalThe raw materials not only can be used for producing monomers of polyester resin, alkyd resin and polyester fiber, but also can be used for producing raw materials of various products such as lubricant, plasticizer, adhesive, surfactant and the like. The demand for ethylene glycol has continued to increase in recent years. The traditional production process of ethylene glycol is an ethylene oxide hydration method, the method has long process flow, high energy consumption and low ethylene glycol selectivity, and the production process excessively depends on petroleum resources. The method for preparing glycol from synthesis gas through oxalate is a more and relatively mature method for synthesizing glycol through a non-petroleum route. The method first prepares synthesis gas (CO + H) from non-petroleum resources₂) Then, the oxalic ester is generated by CO oxidative coupling, and the oxalic ester is further catalyzed and hydrogenated to generate the ethylene glycol. The method has a bright application prospect due to simple process flow, low energy consumption and high ethylene glycol selectivity.

The process for preparing the ethylene glycol by hydrogenating the oxalate is considered as a key step of the process, and the process mainly comprises the following reactions of (1) hydrogenating the oxalate to generate an intermediate product of methyl glycolate; (2) further hydrogenating the methyl glycolate to generate ethylene glycol; (3) the ethylene glycol is continuously hydrogenated to generate ethanol or other dihydric alcohol byproducts; (4) ethylene glycol reacts with other mono-alcohols to form ethers. Therefore, in the process of preparing ethylene glycol by hydrogenating oxalate, how to improve the product selectivity is critical. At present, research and development of a catalyst for preparing ethylene glycol by hydrogenating oxalate with high selectivity and good stability is a research hotspot of the process.

Compared with homogeneous hydrogenation catalysts, heterogeneous hydrogenation catalysts have the advantages of simple preparation method, mild reaction conditions, easy separation of the catalysts and the like, so that the research on the reaction catalysts for preparing ethylene glycol by dimethyl oxalate hydrogenation is focused in recent years, and particularly, copper-based catalysts which are high in activity, low in price and easy to obtain and simple to prepare are more and more important. A great deal of research is carried out on the preparation method, carrier selection, auxiliary agent modification and the like of the copper-based catalyst, and the reaction performance and the reaction stability of the catalyst are improved by improving the antitoxic property, the sintering resistance and the like of the catalyst. Such as: in the Japanese patent of Japan (US 4,229,591), the conversion rate of oxalate can reach 100% and the selectivity of glycol can reach 99.5% under the reaction condition of 180 ℃ and 300 of hydrogen-ester ratio by adopting a copper-based catalyst prepared by ammonia evaporation method. The Cu-Cr catalyst researched at the earliest time by Fujian institute can obtain 99.8% of oxalate conversion rate and 95.3% of glycol selectivity under the conditions of 200-230 ℃, 2.5-3 MPa and 46-60 gas-liquid ratio.

Although the researches have achieved good effects in laboratories, and meanwhile, a plurality of sets of industrial scale-up test devices for producing ethylene glycol from synthesis gas through oxalate are built domestically, the purity of the product ethylene glycol is still a certain distance away from the ethylene glycol standard for polyester, and the stability of the catalyst still needs to be further improved. Meanwhile, SiO of Cu-based catalyst is reported in literature₂The carrier is usually silica sol as a carrier source, and although the catalyst dispersion can be improved, if the catalyst is enlarged on a large scale, the production cost and the environmental burden are undoubtedly increased. Simultaneous carrier SiO₂The structure and physical and chemical properties of the copper-based catalyst have great influence on the hydrogenation performance of the copper-based catalyst.

The invention aims to improve SiO content of a carrier₂The performance of the catalyst improves the selectivity and reaction stability of the catalyst for preparing the ethylene glycol by hydrogenating the oxalic ester, thereby improving the efficiency of the reaction process of the invention.

Disclosure of Invention

The invention aims to solve the technical problem of the prior art and provides a method for preparing ethylene glycol by catalytic hydrogenation of oxalate. The catalyst adopted by the method comprises an active component of metallic copper or copper oxide or a mixture thereof, carrier hydrophilic silicon dioxide or modified hydrophilic silicon dioxide and an auxiliary agent of metallic oxide, wherein the mass percent of copper element in the catalyst is 10-60%, the mass percent of silicon dioxide in the catalyst is 35-90%, and the mass percent of the auxiliary agent of metallic oxide in the catalyst is not higher than 5%. The invention improves the selectivity and stability of the catalyst by regulating the hydrophilicity and acidity of the silicon dioxide.

The hydrophilicity of silica is directly related to the hydroxyl groups (-OH) present on the surface, and generally, the greater the number of hydroxyl groups present on the surface, the stronger the hydrophilicity. Therefore, we generally use SiO₂The number of surface hydroxyl groups is used to indicate the hydrophilicity of the silica. Modification with surfactants is commonly used to increase SiO₂By hydrophobizing the surface to reduce SiO₂Is hydrophilic. For SiO as catalyst carrier₂For example, it is advantageous to control the surface hydrophilicity of the catalyst to be appropriate for the performance of the catalyst.

The invention controls SiO₂The number of surface hydroxyl groups or appropriate substitution of SiO with hydrophobic groups₂Surface hydroxyl of (2) to SiO₂Hydrophilic modification of (2), in particular hydrophilic SiO₂The number of surface hydroxyl groups is 4-5/nm²And silica free of hydrophobic groups. The hydrophilic silicon dioxide is modified by SiO with 0.1-40%, or 0.1-25% of surface hydroxyl groups substituted by hydrophobic groups₂(ii) a The number of the modified hydrophilic silicon dioxide surface hydroxyl groups is 2.4-5.0/nm²Or 3.0 to 4.5/nm². The hydrophobic group refers to alkyl, alkoxy, alkenyl, particularly preferably methyl, methoxy, vinyl, particularly preferably methyl.

The preparation of the hydrophilic silica of the present invention comprises: adding sodium silicate, sodium sulfate and water into a preparation container at the same time, wherein the mass ratio of the sodium silicate to the sodium sulfate to the water is 1: 0.01-0.5: 5-15, stirring at room temperature, heating to 80-90 ℃, dropwise adding a sulfuric acid solution with the mass fraction of 2-20% until the pH value of the system is 10-11, and aging for 15-60 minutes; adding 2-20 wt% sulfuric acid to adjust pH to 4-6.5 (filtering, washing with water until no SO is formed)₄ ^2-Washing with ethanol to remove water, drying at 100-120 deg.C, and calcining at 200-800 deg.C to obtain hydrophilic SiO powder₂；SiO₂The principle of carrier formation is: sodium silicate generates ortho-silicic acid under acidic condition, and micromolecular silicic acid is connected through dehydration polycondensation to form spherical particle SiO with irregular chain dendritic structure₂(ii) a By passingControl of SiO₂Condition control of SiO during formation₂The number of surface hydroxyl groups.

Modified hydrophilic SiO₂The preparation method comprises the following steps:

adding sodium silicate, sodium sulfate and water into a preparation container at the same time, wherein the mass ratio of the sodium silicate to the sodium sulfate to the water is 1: 0.01-0.5: 5-15, stirring at room temperature, heating to 80-90 ℃, dropwise adding a sulfuric acid solution with the mass fraction of 2-20% until the pH value of the system is 10-11, and aging for 15-60 min; adding 2-20% by mass of sulfuric acid to adjust the pH value to 4-6.5, adding a hydrophobic group-containing compound, aging for 0.5-4 h, filtering, and washing with water until no SO is generated₄ ^2-Washing with ethanol to remove water, drying at 100-120 deg.C, and calcining at 200-800 deg.C to obtain white powder as modified hydrophilic SiO₂。

Modified hydrophilic SiO₂The principle of formation is as follows: precursors of hydrophobic groups can be hydrolyzed into small molecular substances under acidic conditions, and the hydrolysis products and synthesized SiO₂The surface hydroxyl of the silicon dioxide is reacted, and the micromolecule organic matter with hydrophobic groups (such as methyl, vinyl and ethoxy) is grafted to the SiO₂Surface modification to obtain hydrophilic SiO₂。

SiO₂The surface has an acid center, and the strength of the acidity is directly related to SiO₂The interaction between the carrier and the active component of the catalyst further influences the catalytic performance, controls the proper acidity range and exerts the effect on SiO₂The catalytic reaction of the carrier is of great significance. Usually, SiO₂The acidity of (A) is directly related to the pH value of an aqueous solution formed after the aqueous solution is mixed with water and stirred stably. Therefore, the invention is based on the determination of SiO₂Determination of SiO by pH value of aqueous solution₂Is acidic. Hydrophilic SiO of the invention₂Or modified hydrophilic SiO₂The pH value of the 4% aqueous solution is less than 6.1, or between 2.2 and 6.0, or between 3.0 and 5.0.

In order to solve the technical problem of the hydrogenation of the prior oxalate, the technical scheme of the invention for preparing the catalyst is as follows:

a catalyst for preparing ethanediol by hydrogenating oxalate features that the metal Cu or Cu oxide or their mixture is used as its active componentIs characterized in that the catalyst is made of hydrophilic SiO₂Or modified hydrophilic SiO₂The catalyst is a carrier, and the mass percent of each component in the catalyst is as follows: 10-60% of active element Cu and SiO carrier₂35-90% of the metal oxide additive and not higher than 5% of the metal oxide additive.

In some embodiments, the hydrophilic SiO₂Are not substituted by hydrophobic groups. In some embodiments, a portion of the surface hydroxyl groups of the hydrophilic silicas described herein are substituted with hydrophobic groups, but retain their hydrophilic character.

The number of surface hydroxyl groups of the silica can be determined by titration. The titration method comprises the following steps: firstly, weighing 4.0g of dry silicon dioxide sample, adding 50mL of ethanol for wetting, then adding 150mL of 20% NaCl solution, and fully stirring; secondly, adjusting the pH value of the solution to 4.0 by using 0.1mol/L HCl solution; finally, titration with 0.1mol/L NaOH solution to pH 9.0, wait until at least 3 minutes without change. The surface hydroxyl number of the silicon oxide is expressed in terms of the volume of NaOH consumed to change the pH of 4.0g of silicon oxide from 4.0 to 9.0. S (m)²The number of hydroxyl groups per nm on the silica surface is calculated by using the BET specific surface area of silicon oxide as a value,/g) and the volume of NaOH consumed for titration as a value²The formula of (1) is as follows:

number of hydroxyl groups (number/nm) on silica surface²)＝6.02×10²³×(V/4)×10^-4/(S ×10¹⁸)

The surface hydroxyl substitution rate of the silicon dioxide can pass through standard SiO₂The number of surface hydroxyl groups of the sample (surface hydroxyl groups are unsubstituted) minus the number of surface hydroxyl groups of the treated silica sample is calculated by dividing the number of surface hydroxyl groups of the standard silica sample. Any silica is treated with a silylating agent such as a halosilane (e.g., alkyl chloride), siloxane, particularly dimethylsiloxane (e.g., hexamethyldisiloxane), or silazane, whose surface hydroxyl groups will be substituted with hydrophobic groups.

The hydrophilic silicon dioxide prepared by the method has 4-5 hydroxyl groups/nm on the surface determined by the method²And does not contain a hydrophobic group. Modified hydrophilic dioxides prepared according to the inventionThe number of the surface hydroxyl groups of the silicon is 2.4-5.0/nm determined by the method²Or 3.0 to 4.5/nm²。

In some embodiments, the silica described herein is an acidic silica, wherein the pH of a 4% aqueous solution of the silica is less than 7.0. The pH of the silica can be obtained by measuring the pH of the solution after thoroughly mixing 4g of dry silica with 100mL of distilled water. In some embodiments, the silica has a 4% aqueous pH of less than 6.1, or less than 6.0, or less than 5.0, or less than 4.0, or less than 3.0, or less than 2.2, or less than 1.0. In some embodiments, the pH of a 4% aqueous solution of the silica is from 2.0 to 6.0. In some embodiments, the silicon oxide has a 4% aqueous pH of 3.0 to 5.0.

The metal oxide additive comprises CeO₂、TiO₂And the mass percentage of the auxiliary agent is not more than 5%, and the optimization is 0.2-3%.

The preparation process of the catalyst comprises the following steps: a) mixing copper-containing salt, metal salt and ammonia water, wherein the metal salt can generate metal oxide; b) adding silica to the solution formed in step (a); c) removing ammonia; d) calcining and grinding the product of step c).

In some embodiments, the catalyst is reduced prior to use, for example, by heating the resulting catalyst by conventional methods in the presence of a reducing agent such as hydrogen, carbon monoxide, or other reducing agent. In some embodiments, the catalyst is reduced by heating in the presence of hydrogen and/or carbon monoxide.

The reaction performance evaluation of the catalyst adopts the following scheme: the method is carried out in a continuous flow gas-solid phase reactor, the filling amount of the catalyst is 1.0g, the catalyst is reduced by adopting pure hydrogen at normal pressure and 350 ℃, the flow rate is 100mL/min, the temperature is increased from room temperature to 350 ℃ at the speed of 1-2 ℃/min, the temperature is kept for 4H, H is introduced after the temperature is reduced to the reaction temperature₂Dimethyl oxalate or its methanol solution is pumped into the reactor for reaction. Analyzing the product by gas chromatography with 30m FFAP polar capillary column, and detecting the reaction raw material by hydrogen flame detector (FID)And a product.

The catalyst conversion and selectivity were calculated as follows:

in the above formula, M is a reaction product such as Ethylene Glycol (EG), Methyl Glycolate (MG), 2-methoxyethyl ether (2-MEO), 1, 2-propanediol (1,2-POD), 1, 2-butanediol (1,2-BOD), etc.

In the reaction for preparing the ethylene glycol by the oxalate hydrogenation reaction, the conversion rate of the oxalate is not lower than 70 percent or not lower than 80 percent or not lower than 90 percent or not lower than 95 percent; the selectivity of the hydrogenation product glycol is not lower than 85 percent or not lower than 90 percent or not lower than 95 percent.

The invention solves the problems of low selectivity and short service life of the catalyst in the catalytic reaction process of preparing the ethylene glycol by hydrogenating the oxalate. The catalyst of the invention has higher reaction performance and reaction stability.

The technical details of the present invention are described in detail by the following examples. The purpose of the embodiments is to further illustrate the technical features of the present invention, but not to limit the present invention.

Detailed Description

Example 1

Hydrophilic SiO₂The preparation of (1):

adding 20g of sodium silicate, 3g of sodium sulfate and 233mL of water into a 500mL flask, stirring at room temperature for 1 hour, heating to 80-90 ℃, dropwise adding a sulfuric acid solution with the mass fraction of 10% until the pH value of the system is 10-11, and aging for 30 min. Adding sulfuric acid to adjust pH to 5, filtering, washing with water until no SO is formed₄ ^2-Washing with ethanol to remove water, drying, and calcining to obtain white powder as hydrophilic SiO₂Is marked as SiO₂A pH of 4% aqueous solution of A represented by the formula 1(A) was measured to be 4.0 and the number of surface hydroxyl groups was measured to be 4.8/nm².

Modification of hydroxy silicone oilHydrophilic SiO₂The preparation of (1):

adding 20g of sodium silicate, 3g of sodium sulfate and 233mL of water into a 500mL flask, stirring at room temperature for 1 hour, heating to 80-90 ℃, dropwise adding a sulfuric acid solution with the mass fraction of 10% until the pH value of the system is 10-11, and aging for 30 min. Adjusting pH to 5 with sulfuric acid, adding hydroxy silicone oil, aging for 1.5 hr, filtering, washing with water until no SO is present₄ ^2-Washing with ethanol to remove water, drying, and calcining to obtain white powder as modified hydrophilic SiO₂Is marked as SiO₂-B, the structural formula of which is shown in formula 1 (B).

Structural formula 1. hydrophilic SiO₂Structural formula (II)

By controlling the addition amount of glycerol in the preparation process, 1g, 2g and 3g of hydroxyl silicone oil are added in the embodiment respectively to obtain modified hydrophilic SiO₂-B-1、SiO₂-B-2、SiO₂-B-3, the pH values of which in 4% aqueous solution are determined to be 4.3,4.5 and 4.9, respectively, the number of surface hydroxyl groups is determined to be: 4.0 molecules/nm²3.3/nm²2.7/nm²。

In the preparation process, 1g of vinyltriethoxysilane is used for replacing 1g of hydroxyl silicone oil to obtain modified hydrophilic SiO₂-C, the batch pH of a 4% aqueous solution is 4.6, the number of surface hydroxyl groups is 4.2/nm².

Example 2

36.3g of Cu (NO) were weighed₃)₂·3H₂O, 500mL of 0.3mol/L Cu (NO)₃)₂And (3) solution. 157mL of Cu (NO) was measured₃)₂The solution was placed in a 250mL beaker, and then 18mL of aqueous ammonia (25 wt%) was added dropwise to Cu (NO)₃)₂In solution such that the pH of the final solution is between about 9 and 10. Mixing 12g of SiO₂-B-2 (pH 4.5 in 4% aqueous solution) was added to the ammoniacal copper solution with stirring. The beaker was aged in a 35 ℃ aqueous solution for 4 hours, warmed to 90 ℃ and maintained at this temperature for 2.5 hours to volatilize ammonia gas. The obtained precipitate isFiltering, washing until the pH value of the filtrate is about 7, transferring the filter cake into a dry pot, drying in an oven at 120 ℃ for 12 hours, and roasting at 450 ℃ for 4 hours. The resulting material was crushed and screened through a 20-40 mesh screen. The catalyst obtained by the reaction is represented as catalyst A, which comprises a mixture of copper and copper oxide and SiO₂。

Comparative example 1

The procedure is as in example 2, except that commercially available SiO is used₂(4% aqueous solution pH 7, surface hydroxyl number of 1.8/nm²) Substitute for SiO₂-B-2, resulting in catalyst A ', catalyst A' comprising a mixture of copper and copper oxide and SiO₂。

Examples 3 to 6

The procedure is as in example 2, except that hydrophilic SiO is used₂-A, modified hydrophilic SiO₂-B-1、 SiO₂-B-3、SiO₂-C instead of SiO as carrier₂B-2, respectively, to obtain catalyst B, C, D, E, the catalyst comprising a mixture of copper and copper oxide and SiO₂。

Example 7

The procedure was as in example 2 except that 157ml of Cu (NO) was added at a concentration of 0.3mol/L₃)₂To the solution, 0.19g of Ce (NO) was added₃)₃·6H₂And O. This example prepared catalyst F, which contained a mixture of copper and copper oxide, CeO₂And SiO₂。

Example 8

The procedure is as in example 2, except that SiO₂Was changed from 12g to 27 g. This example produced catalyst G, which comprises a mixture of copper and copper oxide and SiO₂.

Example 9

The procedure is as in example 2, except that SiO₂The amount of (2) added was changed from 12g to 4.5 g. This example prepared catalyst H, which comprises a mixture of copper and copper oxide and SiO₂.

Example 10

The procedure is as in example 2 except that157ml Cu (NO) concentration of 0.3mol/L₃)₂To the solution, 2g of Ce (NO) was added₃)₃·6H₂And O. This example was prepared to give catalyst I which comprises a mixture of copper and copper oxide, CeO₂And SiO₂。

The compositions of the catalysts prepared in the above examples are shown in Table 1.

TABLE 1 Components for preparing the catalyst

Example 11:

examples 2-6 and comparative example 1 preparation of catalysts A-E and A' at 210 deg.C, 3MPa, 150H/ester ratio, 0.5h^-1LHSV_DMOThe reaction performance of dimethyl oxalate hydrogenation to ethylene glycol under the conditions is shown in Table 2.

TABLE 2 SiO support₂Performance influence on reaction performance of copper-based catalyst dimethyl oxalate hydrogenation for preparing ethylene glycol

As can be seen from Table 2, hydrophilic SiO₂The catalyst used as the carrier shows obvious high reaction performance of hydrogenation of oxalate to ethylene glycol, and the A-E catalysts show better ethylene glycol selectivity. SiO of catalyst A' with poor performance₂Compared with a carrier, the catalyst SiO has better reaction performance₂The carrier has the following characteristics: (1) the suspension with water is acidic; (2) has stronger hydrophilic performance. This indicates hydrophilic acidic SiO₂The carrier is suitable for being used as a carrier of a catalyst for preparing the ethylene glycol by hydrogenating the esters of the herbal acids.

Example 12:

example 2, 8-9 preparation of catalyst A, G and H at 190 deg.C, 3.5MPa, 120H-ester ratio, 0.5H^-1LHSV_DMOThe reaction performance of dimethyl oxalate hydrogenation to ethylene glycol under the conditions is shown in Table 3.

TABLE 3 copper content addition to dimethyl oxalate on copper-based catalystEffect of Hydrogen glycol reactivity

As can be seen from Table 3, the oxalate hydrogenation activity of the catalyst is gradually enhanced with the increase of the Cu content, and when the Cu content is increased to 20%, the DMO conversion rate reaches 100%, and the EG selectivity simultaneously reaches an optimal value of 93.1%. As the Cu content continues to increase, the selectivity of EG slightly decreases, the selectivity of byproducts such as EO and 2-MEO increases, and the selectivity of MG decreases, because the hydrogenation performance of the catalyst is gradually enhanced as the Cu content increases, and the target product EG is further hydrogenated to generate a secondary reaction product.

Example 13:

examples 2,7, 10 preparation of catalyst A, F and I at 200 deg.C, 2.0MPa, 100H/ester ratio, 0.35h^-1LHSV_DMOThe reaction performance of dimethyl oxalate hydrogenation to ethylene glycol under the conditions is shown in Table 4. As can be seen from the results in the table, CeO was added to the catalyst₂After the auxiliary agent, the selectivity of the target product ethylene glycol in the reaction of preparing ethylene glycol by hydrogenating oxalate is further increased. In CeO₂When the content is increased to 5%, the selectivity of the glycol is slightly reduced.

TABLE 4 CeO₂Influence of auxiliary agent on reaction performance of copper-based catalyst dimethyl oxalate hydrogenation to ethylene glycol

Example 14

Example 2 catalyst A at 3.0MPa, 80H/ester ratio, 0.5h^-1LHSV_DMOThe results of the reaction performance of dimethyl oxalate hydrogenation to ethylene glycol with pure ester feed conditions as a function of reaction temperature are shown in Table 5.

TABLE 5 reaction temperature Performance of dimethyl oxalate hydrogenation to ethylene glycol on copper-based catalyst

The experimental results in table 5 show that, in the investigated reaction temperature range, catalyst a shows higher reaction performance for hydrogenation of oxalate to ethylene glycol, DMO is almost completely converted, and ethylene glycol selectivity is maintained above 90%. As the reaction temperature increases, the selectivity of Ethylene Glycol (EG) gradually decreases, and the selectivity of byproducts Ethanol (EO), 1, 2-propanediol (1,2-POD) and 1, 2-butanediol (1,2-BOD) gradually increases. This is due to the fact that the hydrogenation capacity of the catalyst increases with increasing reaction temperature, and the reaction product, ethylene glycol, is further hydrogenated.

Example 15:

example 2 catalyst A at 210 deg.C, 3.0MPa, 0.5h^-1LHSV_DMOThe results of the reaction performance of dimethyl oxalate hydrogenation to ethylene glycol under the conditions varied with the hydrogen-ester ratio of the starting material are shown in Table 6.

As can be seen from Table 6, catalyst A showed excellent reaction performance with DMO conversion greater than 99% and EG selectivity greater than 91% over the range of hydrogen to ester ratios examined. As the hydrogen-to-ester ratio increases, the selectivity of the hydrogenation product EG increases, reaching an optimum value at a hydrogen-to-ester ratio of 100, and then decreases slightly. The by-product MG decreases with increasing hydrogen-ester ratio, and the selectivity to EO, 1,2-POD, 1,2-BOD increases with increasing hydrogen-ester ratio. This is because an increase in the hydrogen-to-ester ratio is beneficial to the hydrogenation performance of the catalyst.

TABLE 6 influence of hydrogen-ester ratio variation on the reaction behavior of dimethyl oxalate hydrogenation to ethylene glycol over copper-based catalyst

Example 16:

example 2 preparation of catalyst A at 175 deg.C, 3MPa, 80H/ester ratio, 0.5h^-1LHSV_DMOThe results of the 1000 hour reaction stability test with pure ester feed are shown in Table 7.

TABLE 7 stability results of dimethyl oxalate hydrogenation to ethylene glycol over copper-based catalyst

As can be seen from Table 7, catalyst A prepared in example 2 maintained complete conversion of DMO and EG selectivity above 97% during the 1000 hour reaction stability test examined. The test result shows that the catalyst A not only has good reaction performance in preparing the ethylene glycol by hydrogenating the oxalic ester, but also has good reaction stability.

Claims

1. A method for preparing ethylene glycol by oxalate hydrogenation is characterized in that: the method adopts raw materials at least containing oxalate and hydrogen to produce glycol through a catalyst; the catalyst adopted by the method comprises one or two mixtures of metal copper or copper oxide, one or two hydrophilic silicon dioxide or modified hydrophilic silicon dioxide, and contains or does not contain a metal oxide auxiliary agent, wherein the mass percent of copper element in the catalyst is 10-60%, the mass percent of silicon dioxide in the catalyst is 35-90%, and the mass percent of the metal oxide auxiliary agent in the catalyst is not higher than 5%;

wherein the catalyst component is hydrophilic silica, SiO₂The number of surface hydroxyl groups is 4-5/nm²And silica free of hydrophobic groups; the modified hydrophilic silicon dioxide refers to SiO with 0.1-40% of surface hydroxyl groups substituted by hydrophobic groups₂；

The number of the modified hydrophilic silicon dioxide surface hydroxyl groups is 2.4-4.995/nm²(ii) a The hydrophobic group refers to one or more than two of alkyl, alkoxy and alkenyl;

the preparation method of the hydrophilic silicon dioxide comprises the following steps:

adding sodium silicate, sodium sulfate and water into a preparation container at the same time, wherein the mass ratio of the sodium silicate to the sodium sulfate to the water is 1: 0.01-0.5: 5-15, stirring at room temperature, heating to 80-90 ℃, dropwise adding a sulfuric acid solution with the mass fraction of 2-20% until the pH value of the system is 10-11, and aging for 15-60 minutes; adding 2-20 mass percent of sulfuric acid to adjust the pH value to 4-6.5, filtering, and washing until no SO is generated₄ ^2-Washing with ethanol to remove water, drying at 100-120 deg.C, and drying at 200-800 deg.C^oRoasting C to obtain white powder which is hydrophilic SiO₂；

adding sodium silicate, sodium sulfate and water into a preparation container at the same time, wherein the mass ratio of the sodium silicate to the sodium sulfate to the water is 1: 0.01-0.5: 5-15, stirring at room temperature, heating to 80-90 ℃, dropwise adding a sulfuric acid solution with the mass fraction of 2-20% until the pH value of the system is 10-11, and aging for 15-60 min; adding 2-20 mass percent of sulfuric acid to adjust the pH value to 4-6.5, adding a hydrophobic group-containing compound, aging for 0.5-4 h, filtering, and washing with water until no SO is generated₄ ^2-Washing with ethanol to remove water, drying at 100-120 deg.C, and calcining at 200-800 deg.C to obtain white powder as modified hydrophilic SiO₂。

2. The method of claim 1, wherein: the modified hydrophilic silicon dioxide refers to SiO with 0.1-25% of surface hydroxyl groups substituted by hydrophobic groups₂。

3. The method of claim 1, wherein: the modified hydrophilic silicon dioxide refers to SiO with 10-25% of surface hydroxyl groups substituted by hydrophobic groups₂。

4. The method of claim 1, wherein:

the number of the modified hydrophilic silicon dioxide surface hydroxyl groups is 3.0-4.995/nm²；

Wherein the hydrophobic group refers to one or more than two of methyl, methoxy and vinyl.

5. The method of claim 1, wherein:

the number of the modified hydrophilic silicon dioxide surface hydroxyl groups is 3.0-4.5/nm²；

Wherein the hydrophobic group is methyl.

6. The method of claim 1, further comprising: the hydrophobic group-containing compound is a compound containing one or more of an alkyl group, an alkoxy group and an alkenyl group.

7. The method of claim 1, further comprising: the compound containing hydrophobic groups is one or more than two of hexamethyl silazane, sodium methylsilane, sodium ethylsilane, hydroxy silicone oil and vinyl triethoxysilane.

8. The method of claim 1, further comprising: the compound containing hydrophobic groups is one or two of hydroxyl silicone oil and vinyl triethoxysilane.

9. The method according to any one of claims 1 to 5, wherein: wherein the hydrophilic silica or modified hydrophilic silica is both acidic silica.

10. The method of claim 9, further comprising: the pH of a 4wt% aqueous solution of the hydrophilic silica or modified hydrophilic silica is less than 6.1.

11. The method of claim 9, further comprising: the pH of a 4wt% aqueous solution of the hydrophilic silica or modified hydrophilic silica is between 2.2 and 6.0.

12. The method of claim 9, further comprising: the pH of a 4wt% aqueous solution of the hydrophilic silica or modified hydrophilic silica is between 3.0 and 5.0.

13. The method of claim 1 wherein the metal oxide additive is CeO₂、TiO₂One or a mixture of two of them.

14. A method as claimed in any one of claims 1 to 8, wherein: the preparation process of the catalyst comprises the following steps of,

a) mixing soluble copper salt, soluble metal salt and 10-35% ammonia water by mass concentration, wherein the metal salt can finally generate corresponding metal oxide auxiliary agent, and the molar concentration of the copper salt in the solution is 0.05-2 mol/L;

b) adding hydrophilic silica or modified hydrophilic silica to the solution generated in step a);

c) removing ammonia from the solution;

d) roasting and grinding the product obtained in the step c) at 300-600 ℃.

15. The method of claim 1, wherein: the oxalate refers to one or more of monomethyl oxalate, monoethyl oxalate, dimethyl oxalate and diethyl oxalate.

16. The method of claim 1, wherein: the oxalate refers to one or two of dimethyl oxalate or diethyl oxalate.

17. The method of claim 1, wherein: the reaction for preparing ethylene glycol by hydrogenating oxalate is carried out at the temperature of 160-230 ℃, under the pressure of 0.5-6 MPa and under the hydrogen-ester molar ratio of 10-200.

18. The method of claim 17, wherein: the reaction for preparing the ethylene glycol by hydrogenating the oxalate is carried out at the temperature of 160-200 ℃.

19. The method of claim 17, wherein: the reaction for preparing the ethylene glycol by hydrogenating the oxalate is carried out under the pressure of 0.5-4 Mpa.

20. The method of claim 17, wherein: the reaction for preparing the ethylene glycol by hydrogenating the oxalate is carried out under the pressure of 1-2 Mpa.

21. The method of claim 17, wherein: the reaction for preparing the ethylene glycol by hydrogenating the oxalate is carried out at a hydrogen-ester molar ratio of 30-150.

22. The method of claim 17, wherein: the reaction for preparing the ethylene glycol by hydrogenating the oxalate is carried out at a hydrogen-ester molar ratio of 50-150.

23. The method of claim 17, wherein: the reaction for preparing the ethylene glycol by hydrogenating the oxalate is carried out at a hydrogen-ester molar ratio of 50-100.