Catalyst, process for its preparation and process for the preparation of methyl glycolate

Abstract

The application relates to the technical field of organic synthesis, in particular to a catalyst, a preparation method thereof and a preparation method of methyl glycolate. The preparation method of the catalyst comprises the following steps: loading a copper salt and a silver salt on a carrier to obtain a catalyst precursor, wherein the material of the carrier comprises silicon dioxide; performing electromagnetic radiation treatment on the catalyst precursor to obtain a modified catalyst precursor; and performing reduction treatment on the modified catalyst precursor, so that the copper salt loaded on the carrier is reduced into elemental copper, and the silver salt loaded on the carrier is reduced into elemental silver. The preparation method can improve the DMO conversion rate and the MG selectivity.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic synthesis, in particular to a catalyst, a preparation method thereof and a preparation method of methyl glycolate. BACKGROUND

[0002] Methyl glycolate (MG) has important industrial application prospects as a precursor of degradable polymer materials (such as polyglycolic acid, PGA). The current mainstream synthesis path in industry is selective hydrogenation of dimethyl oxalate (DMO) under the action of a catalyst. However, the Cu-based catalysts commonly used in the prior art generally have problems such as easy oxidation of the surface, weak hydrogen activation ability, poor structural stability, and the like, and it is difficult to balance high selectivity and high conversion rate. Ag has strong selective adsorption of carbonyl ability, which can effectively inhibit the over-hydrogenation of MG, but its hydrogenation activity is low, and the effect is not good when used alone. The Cu-Ag bimetallic catalyst can combine the advantages of both, but the traditional preparation methods of the Cu-Ag bimetallic catalyst (such as co-impregnation, reduction deposition, etc.) often lead to uneven distribution of metals, serious particle agglomeration, insufficient interface synergistic effect, and difficulty in inducing the formation of non-equilibrium structures (such as core-shell structure, amorphous phase or defect-rich surface), so that the synergistic catalytic effect of the bimetallic catalyst cannot be fully exerted, affecting the selectivity of MG and the service life of the catalyst. SUMMARY

[0003] Based on this, the first aspect of the present application provides a preparation method of a catalyst, and the technical scheme is as follows:

[0004] The preparation method of the catalyst comprises the following steps:

[0005] The copper salt and the silver salt are loaded on the carrier to obtain a catalyst precursor, wherein the material of the carrier comprises silicon dioxide;

[0006] The catalyst precursor is subjected to electromagnetic radiation treatment to obtain a modified catalyst precursor;

[0007] The modified catalyst precursor is subjected to reduction treatment, so that the copper salt loaded on the carrier is reduced to elemental copper, and the silver salt loaded on the carrier is reduced to elemental silver.

[0008] The second aspect of the present application provides a catalyst prepared by the preparation method as described above.

[0009] The second aspect of the present application provides a preparation method of methyl glycolate, and the technical scheme is as follows:

[0010] The preparation method of methyl glycolate comprises the following steps:

[0011] In the presence of a catalyst, dimethyl oxalate is reacted with hydrogen to generate methyl glycolate; wherein the catalyst is as described above.

[0012] Compared with the conventional scheme, the present application has the following beneficial effects:

[0013] In the preparation of the catalyst, the present application adds a step of treating the catalyst precursor with electromagnetic radiation to prepare a modified catalyst precursor. The short-time high-temperature rapid melting and cooling after electromagnetic radiation treatment are conducive to realizing metal particle redistribution and interface structure reconstruction, inducing the formation of small-size Cu@Ag core-shell structures or highly uniform small-size alloy structures on the surface of the carrier. The above structures are stable, have strong interface bonding, effectively improve the hydrogen activation capacity and selective adsorption of the carbonyl group in DMO, and make the catalyst exhibit good stability in long-time continuous reaction. The catalyst of the present application, under the electronic synergistic effect of CuAg bimetallic, combined with the new strategy of electromagnetic radiation-induced reconstruction, realizes the construction of highly dispersed, stable and high-loading CuAg bimetallic nanostructures on the silicon carrier, solves the problems of easy agglomeration, poor dispersion, weak interface bonding and unstable configuration of Ag, and can improve the efficiency of DMO selective hydrogenation and the catalytic life. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, more completely understand the present application and its beneficial effects, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0015] Figure 1 Structure schematic diagram and TEM image of the catalyst of Comparative Example 1, Example 1, Comparative Example 2 and Example 2;

[0016] Figure 2 DMO conversion rate and MG selectivity of the catalyst of Comparative Example 1, Example 1, Comparative Example 2 and Example 2 within 5h;

[0017] Figure 3 DMO conversion rate and MG selectivity of the catalyst of Example 2 within 300h. DETAILED DESCRIPTION

[0018] The present application will be further described in detail below in combination with specific embodiments. The present application can be realized in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the present disclosure more thorough and comprehensive.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application.

[0020] Unless otherwise defined, or as can be otherwise apparent from context, terms and phrases used herein have their ordinary meanings within the technical field of the application.

[0021] In this application, the terms such as “plurality”, “a plurality of”, “plural”, “a plural of”, or the like, refer to two or more, unless otherwise indicated or contradicted by context.

[0022] In this application, the terms such as “optionally”, “optional”, or “may” mean that the subsequently described event or circumstance can or can not occur, or that the subsequently described event or circumstance is preferred, or, in other words, that the subsequently described event or circumstance is optional. If a technical solution appears multiple times with “optionally” in the specification, each “optionally” is independent of each other, unless otherwise specified, and there is no contradictory relationship or mutual restriction.

[0023] In this application, the terms such as “first aspect”, “second aspect”, “third aspect”, “fourth aspect”, or the like, the terms “first”, “second”, “third”, “fourth” and the like are used only for the purpose of description, and cannot be understood as indicating or implying relative importance or quantity, nor can it be understood as implicitly indicating the importance or quantity of the technical features indicated. Moreover, “first”, “second”, “third”, “fourth” and the like only serve the purpose of non-exhaustive enumeration and description, and should be understood as not constituting a closed limitation on the quantity.

[0024] In this application, with respect to a numerical interval (i.e. a numerical range), if not otherwise specified, the optional numerical distribution within the numerical interval is considered to be continuous, and includes both numerical end points (i.e. the minimum value and the maximum value) of the numerical range, as well as every numerical value between the two numerical end points.

[0025] In this application, the temperature parameter, if not otherwise specified, allows for constant temperature treatment, and also allows for fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for fluctuations within the accuracy range controlled by the instrument. Fluctuations within a range such as ±5°C, ±4°C, ±3°C, ±2°C, ±1°C are allowed.

[0026] In this application, room temperature refers to 10°C to 40°C.

[0027] The first aspect of the present application provides a preparation method of a catalyst. In one embodiment, the preparation method of the catalyst comprises the following steps:

[0028] S10, loading copper salt and silver salt on a carrier to obtain a catalyst precursor, wherein the carrier is made of silica.

[0029] Optionally, the carrier is modified with an amino group. It can be understood that the carrier modified with the amino group is prepared by mixing the carrier and ethylenediaminetetraacetic acid (EDTA). By modifying the silica carrier with the amino group, the carrier has a high specific surface area and abundant surface coordination sites for anchoring metal salts.

[0030] Optionally, the carrier has mesopores.

[0031] Optionally, the loading of the copper salt and the silver salt on the carrier comprises the following steps:

[0032] The carrier is immersed in a solution containing copper salt and silver salt, and then taken out and dried.

[0033] Optionally, the copper salt comprises one or more of copper nitrate, copper lactate, copper acetate and copper chloride. Optionally, the silver salt comprises one or more of silver nitrate, silver lactate, silver acetate and silver chloride. Optionally, the mass ratio of the carrier to the copper salt is 1: (1-2). Optionally, the mass ratio of the carrier to the silver salt is 1: (0.5-1).

[0034] Optionally, the solvent of the solution containing the copper salt and the silver salt comprises ethanol.

[0035] Optionally, the immersion time of the carrier in the solution containing the copper salt and the silver salt is 20-28 h.

[0036] Optionally, by controlling the immersion conditions, the total mass of elemental copper and elemental silver loaded per 1 g of carrier is in the range of 1-5 g.

[0037] Optionally, the drying temperature is 60-80°C.

[0038] S20, performing electromagnetic radiation treatment on the catalyst precursor to obtain a modified catalyst precursor.

[0039] Through electromagnetic radiation treatment, short-time high-temperature rapid melting and cooling are beneficial to realize metal particle redistribution and interface structure reconstruction, induce the formation of small-size Cu@Ag core-shell structure or highly uniform small-size alloy structure, effectively improve the hydrogen activation capacity and selective adsorption of the carbonyl group in DMO, and make the catalyst exhibit good stability in long-time continuous reaction. It can be understood that the electromagnetic radiation treatment is performed in an inert atmosphere, wherein the inert atmosphere comprises nitrogen.

[0040] Optionally, the electromagnetic radiation treatment comprises a combination of one or more of a laser scanning treatment, a microwave irradiation treatment, and a high-frequency electromagnetic field treatment, the electromagnetic field of the high-frequency electromagnetic field treatment being formed by an induction heating coil or an electromagnetic resonance cavity. It can be understood that the laser scanning treatment, the microwave irradiation treatment, and the high-frequency electromagnetic field treatment can be combined, and the catalyst precursor is subjected to combined external field treatment. For example, the catalyst precursor is exposed to laser light for laser scanning, and then exposed to microwave for microwave irradiation.

[0041] Optionally, the catalyst precursor is subjected to electromagnetic radiation treatment, comprising the following steps:

[0042] exposing the catalyst precursor to laser light for laser scanning; and / or exposing the catalyst precursor to microwave for microwave irradiation, and / or exposing the catalyst to a high-frequency electromagnetic field formed by an induction heating coil or an electromagnetic resonance cavity. Through the above electromagnetic radiation treatment, the metal particles are re-dispersed and reconfigured in a microscale, and a stable core-shell structure or an alloy structure with small particle size and strong synergistic effect is obtained, thereby improving the overall performance of the catalyst.

[0043] Among them, laser scanning, as a typical physical external field method, has unique advantages in metal-support interface regulation. Through the "inverse bremsstruhlung effect" mechanism, the metal surface can quickly absorb laser energy, realize electron-lattice coupling and complete heat exchange (10 -12 s order) in a very short time, and then form small-size crystal nuclei or stable hybrid orbits. This process is accompanied by laser-induced rapid quenching rate (10 6 ~10 8 K / s) and short-range reaction of metal particles with reactive intermediate groups such as hydroxyl (OH - ), hydrogen (H + ), etc., inducing the formation of highly activated core-shell or defect-rich phases, which helps to passivate the surface oxidation and enhance the electronic synergistic effect, and has important regulation effect on stabilizing the metal particle structure and inhibiting the growth of crystal nucleus.

[0044] Optionally, the wavelength of the laser scanning treatment is 1050 nm to 1080 nm. Optionally, the functional density of the laser scanning treatment is 1 x 10 6 W / cm 2 ~1 x 10 8 W / cm 2 . Optionally, the scanning rate of the laser scanning treatment is 1 mm / s to 120 mm / s. Optionally, the scanning times of the laser scanning treatment is 1 to 3 times.

[0045] Optionally, the microwave irradiation treatment has a frequency of 0.9 GHz to 2.5 GHz. Optionally, the microwave irradiation treatment has a power of 700 W to 900 W. Optionally, the microwave irradiation treatment has a time of 20 min to 40 min.

[0046] Optionally, the high-frequency electromagnetic field treatment has a frequency of 10 MHz to 300 MHz. Optionally, the high-frequency electromagnetic field treatment has a power of 1.5 kW to 2.5 kW. Optionally, the high-frequency electromagnetic field treatment has a time of 10 min to 20 min.

[0047] S30, performing reduction treatment on the modified catalyst precursor, so that the copper salt loaded on the carrier is reduced to elemental copper, and the silver salt loaded on the carrier is reduced to elemental silver.

[0048] After the reduction treatment, the copper salt and the silver salt are reduced, and at the same time, the structure is stabilized. Optionally, the reduction treatment has a temperature of 250°C to 350°C. Optionally, the reduction treatment has a time of 1 h to 3 h.

[0049] Optionally, the atmosphere of the reduction treatment includes hydrogen. Optionally, the atmosphere of the reduction treatment further includes an inert gas. The inert gas includes argon. The volume ratio of the hydrogen and the inert gas is 1: (3 to 5).

[0050] In the preparation of the catalyst, the embodiment adds a step of performing electromagnetic radiation treatment on the catalyst precursor to prepare a modified catalyst precursor. The short-time high-temperature rapid melting and cooling after the electromagnetic radiation treatment are beneficial to realize metal particle redistribution and interface structure reconstruction, induce the formation of small-size Cu@Ag core-shell structures or highly uniform small-size alloy structures on the surface of the carrier, and effectively improve the hydrogen activation capacity and the selective adsorption of the carbonyl group in the DMO. The catalyst has good stability in long-time continuous reaction. Under the electronic synergistic effect of the CuAg bimetal, combined with the new strategy of electromagnetic radiation-induced reconstruction, the catalyst realizes the construction of highly dispersed, stable, and high-loading CuAg bimetallic nanostructures on the silicon carrier, solves the problems of easy agglomeration, poor dispersion, weak interface combination, and unstable structure of Ag, and improves the DMO selective hydrogenation efficiency and the catalytic life.

[0051] On this basis, combined with the amino-modified carrier, a functionalized carrier with strong coordination ability and anchoring sites is constructed to realize the uniform anchoring and dispersion of Cu salt and Ag salt and further improve the catalytic performance of the catalyst. Through the synergistic strategy of "chemical modification + physical field", not only the metal dispersion and particle size uniformity are significantly improved, but also the CuAg structure with core-shell or alloy configuration is induced to form, which enhances the synergistic effect between the bimetallic metals, thereby realizing high metal loading rate while maintaining high dispersion. The prepared catalyst can be stably operated under industrial conditions and is suitable for the continuous process of DMO hydrogenation to MG.

[0052] The catalyst prepared by the above preparation method has high DMO conversion rate and MG selectivity, long catalytic life, and the preparation method is simple, efficient and green, which has good industrial application prospect.

[0053] The second aspect of the present application provides a catalyst, in one embodiment, the catalyst is prepared by the preparation method as described above.

[0054] Optionally, the catalyst includes a carrier and elemental copper and elemental silver loaded on the carrier, and the material of the carrier includes silicon dioxide.

[0055] Optionally, the particle size of the elemental copper is 2-5 nm. Optionally, the particle size of the elemental silver is 2-5 nm.

[0056] The above-mentioned catalyst loaded Cu and Ag bimetallic nanoparticles, after electromagnetic radiation treatment, form core-shell structure or uniform alloy structure, are enriched on the surface, and are highly dispersed on the surface of the carrier.

[0057] The DMO conversion rate of the above-mentioned catalyst reaches ≥98%, the MG selectivity is improved to >90%, the catalytic life is more than 300 h without obvious attenuation, and the performance is improved by more than 30% compared with the traditional CuAg catalyst.

[0058] The second aspect of the present application provides a preparation method of methyl hydroxyacetate, in one embodiment, the preparation method of methyl hydroxyacetate includes the following steps:

[0059] In the presence of a catalyst, dimethyl oxalate reacts with hydrogen to produce methyl hydroxyacetate; wherein the catalyst is as described above.

[0060] Optionally, the mass ratio of dimethyl oxalate to catalyst is (10-30):1.

[0061] Optionally, the molar ratio of dimethyl oxalate to hydrogen is 1:(45-55).

[0062] Optionally, the dimethyl oxalate is provided by a methanol solution of dimethyl oxalate, and the molar ratio of dimethyl oxalate to methanol is 1: (8-12).

[0063] Optionally, the reaction conditions of dimethyl oxalate and hydrogen include that the reaction temperature is 180-220℃, the reaction pressure is 2-3 MPa, and the reaction time is 250-350 h.

[0064] The catalytic hydrogenation of dimethyl oxalate can be carried out in a fixed bed reactor, the catalyst is loaded in the fixed bed reactor, the reaction temperature is controlled at 180-220℃, the reaction pressure is controlled at 2-3 MPa, the methanol solution of dimethyl oxalate and hydrogen are introduced into the reactor and pass through the catalyst bed, the space velocity of the methanol solution of dimethyl oxalate is 0.1-0.5 h -1 ~0.5h -1 , and the continuous reaction time is 250-350 h.

[0065] Using the above catalyst for DMO catalytic hydrogenation reaction, the conversion rate of DMO can be ≥95%, even ≥98%, the selectivity of MG is ≥90%, and the catalytic efficiency is high.

[0066] The following will be further described in combination with specific examples and comparative examples. The raw materials involved in the following specific examples and comparative examples, if not specifically stated, can be sourced from the market. The instruments used, if not specifically stated, can be sourced from the market. The processes involved, if not specifically stated, are commonly selected by those skilled in the art.

[0067] Example 1

[0068] The present embodiment provides a preparation method of CuAg@MS catalyst, and the steps are as follows:

[0069] Step 1: Take 2.0 g of carrier (mesoporous SiO2spheres) and immerse it in 100 mL of ethanol solution containing 3 g of Cu(NO3)3·3H2O and 1.5 g of AgNO3. After standing and immersing at room temperature for 24 hours, dry it at 70℃ by rotary evaporation to obtain a catalyst precursor.

[0070] Step 2: Place the catalyst precursor prepared in step 1 on a laser treatment platform, and use a laser with a wavelength of 1064 nm to scan the surface of the catalyst precursor under a nitrogen atmosphere. Set the laser power density to 1×10 7 W / cm², the scanning rate is 110 mm / s, the scanning times is 2, and after the treatment is completed, cool it for standby to obtain a modified catalyst precursor.

[0071] Step 3, the modified catalyst precursor prepared in step 2 was placed in a mixed gas atmosphere of H2 / Ar (volume ratio 1:4), and reduced at 300°C for 2 hours to obtain the CuAg@MS catalyst.

[0072] Comparative Example 1

[0073] This comparative example provides a preparation method of a CuAg@MS catalyst, which is basically the same as Example 1, except that the laser irradiation treatment in step 2 is not performed. The specific steps are as follows:

[0074] Step 1, take the carrier (mesoporous SiO2spheres) 2.0 g, immerse in 100 mL of ethanol solution containing 3 g of Cu(NO3)3·3H2O and 1.5 g of AgNO3, and stand for immersion at room temperature for 24 hours, and then dry at 70°C by rotary evaporation to obtain a catalyst precursor.

[0075] Step 2, the catalyst precursor prepared in step 1 was placed in a mixed gas atmosphere of H2 / Ar (volume ratio 1:4), and reduced at 300°C for 2 hours to obtain the CuAg@MS catalyst.

[0076] Example 2

[0077] This example provides a preparation method of a CuAg@NH2-MS catalyst, and the steps are as follows:

[0078] Step 1, disperse 2.0 g of mesoporous SiO2spheres in 50 mL of ethanol solution containing 0.2 mol / L of ethylenediaminetetraacetic acid (EDTA), stir at room temperature for 12 hours, filter and dry to obtain an amino-modified silica carrier (NH2-MS).

[0079] Step 2, take 2.0 g of the NH2-MS carrier prepared in step 1, immerse in 100 mL of ethanol solution containing 3 g of Cu(NO3)3·3H2O and 1.5 g of AgNO3, and stand for immersion at room temperature for 24 hours, and then dry at 70°C by rotary evaporation to obtain a catalyst precursor.

[0080] Step 3, place the catalyst precursor prepared in step 2 on a laser treatment platform, and use a laser with a wavelength of 1064 nm to scan the surface of the catalyst precursor under a nitrogen atmosphere. Set the laser power density to 1×10 7 W / cm², the scanning rate is 110 mm / s, the scanning times is 2, and after the treatment is completed, cool and reserve for use to obtain a modified catalyst precursor.

[0081] Step 4, place the modified catalyst precursor prepared in step 3 in a mixed gas atmosphere of H2 / Ar (volume ratio 1:4), and reduce at 300°C for 2 hours to obtain the CuAg@NH2-MS catalyst.

[0082] Comparative Example 2

[0083] This comparative example provides a preparation method of CuAg@NH2-MS catalyst, which is basically the same as that of Example 2, except that the laser irradiation treatment of step 3 is not performed. The specific steps are as follows:

[0084] Step 1, 2.0 g of mesoporous SiO2spheres were dispersed in 50 mL of an ethanol solution containing 0.2 mol / L ethylenediaminetetraacetic acid (EDTA), stirred at room temperature for 12 hours, and then filtered and dried to obtain an amino-modified silica carrier (NH2-MS).

[0085] Step 2, 2.0 g of the NH2-MS carrier prepared in step 1 was immersed in 100 mL of an ethanol solution containing 3 g of Cu(NO3)3·3H2O and 1.5 g of AgNO3, and then placed at room temperature for 24 hours. After that, the catalyst precursor was obtained by rotary evaporation drying at 70°C.

[0086] Step 3, the catalyst precursor prepared in step 2 was placed in a mixed gas atmosphere of H2 / Ar (volume ratio 1:4) and reduced at 300°C for 2 hours to obtain the CuAg@NH2-MS catalyst.

[0087] Example 3

[0088] This example provides a preparation method of CuAg@NH2-MS catalyst, which is basically the same as that of Example 2, except that the laser parameters of step 3 are different. The steps are as follows:

[0089] Step 3, the catalyst precursor prepared in step 2 was placed on a laser treatment platform and scanned on the surface of the catalyst precursor under a nitrogen atmosphere using a laser with a wavelength of 1064 nm. The laser power density was set to 5×10 6 W / cm², the scanning rate was 3 mm / s, the scanning number was 1, and the modified catalyst precursor was obtained after cooling.

[0090] Example 4

[0091] This example provides a preparation method of CuAg@NH2-MS catalyst, which is basically the same as that of Example 2, except that the laser parameters of step 3 are different. The steps are as follows:

[0092] Step 3, the catalyst precursor prepared in step 2 was placed on a laser treatment platform and scanned on the surface of the catalyst precursor under a nitrogen atmosphere using a laser with a wavelength of 1064 nm. The laser power density was set to 8×10 7 W / cm², the scanning rate was 8 mm / s, the scanning number was 3, and the modified catalyst precursor was obtained after cooling.

[0093] Example 5

[0094] This example provides a preparation method of CuAg@NH2-MS catalyst, which is basically the same as that of Example 2, except that step 3 is subjected to microwave irradiation, and the steps are as follows:

[0095] Step 3, the catalyst precursor prepared in step 2 is placed in a sealed quartz tube and exposed to microwave at a frequency of 2.45 GHz for 30 min, the microwave power is 800 W, and the atmosphere is nitrogen. After treatment, cool and reserve, get modified catalyst precursor.

[0096] Example 6

[0097] This example provides a preparation method of CuAg@NH2-MS catalyst, which is basically the same as that of Example 2, except that step 3 is subjected to high-frequency electromagnetic field treatment, and the steps are as follows:

[0098] Step 3, the catalyst precursor prepared in step 2 is placed in a high-frequency electromagnetic field (frequency 50 MHz, power 2 kW) generated by an induction heating coil for 15 min, and the atmosphere is nitrogen. After treatment, cool and reserve, get modified catalyst precursor.

[0099] Example 7

[0100] This example provides a preparation method of CuAg@NH2-MS catalyst, which is basically the same as that of Example 2, except that step 3 is subjected to combined external field treatment, and the steps are as follows:

[0101] Step 3, the catalyst precursor prepared in step 2 is placed in a sealed quartz tube and exposed to microwave at a frequency of 2.45 GHz for 20 min, the microwave power is 800 W, and the atmosphere is nitrogen. After treatment, cool and then place it on a laser treatment platform, and scan the surface of the catalyst precursor with a laser with a wavelength of 1064 nm under a nitrogen atmosphere. Set the laser power density to 2×10 7 W / cm², the scanning rate is 5 mm / s, and the scanning number is 2 times. After treatment, cool and reserve, get modified catalyst precursor.

[0102] Test Example

[0103] Item 1: The structural schematic diagram and TEM image of the catalysts of Comparative Example 1, Example 1, Comparative Example 2 and Example 2 are shown in Figure 1 . Among them, Figure 1 a i is the structural schematic diagram of the catalyst of Comparative Example 1, Figure 1 a ii is the TEM image of the catalyst of Comparative Example 1, Figure 1 bi This is a schematic diagram of the catalyst structure in Example 1. Figure 1 b ii This is a TEM image of the catalyst from Example 1. Figure 1 c i This is a schematic diagram of the catalyst structure in Comparative Example 2. Figure 1 c ii This is a TEM image of the catalyst in Comparative Example 2. Figure 1 d i This is a schematic diagram of the catalyst structure in Example 2. Figure 1 d ii This is a TEM image of the catalyst in Example 2.

[0104] It can be known that: Figure 1 a i The results show that Ag and Cu nanoparticles are loaded onto the surface of sea urchin-shaped mesoporous silica spheres, with relatively large particle size and moderate dispersibility. Figure 1 a ii Display: The metal particles are uneven and partially agglomerated. Figure 1 b i The results show that after laser irradiation, the particle size is reduced and some interfaces are reconstructed. Figure 1 b ii The results show that the number of metal particles has decreased significantly and their distribution has become more uniform. Figure 1 CI results show that amino modification on the carrier surface enhances metal anchoring, and the particles are smaller than those in the unmodified sample. Figure 1 c ii The results show that the metal particles have higher dispersibility and are more uniform in size. Figure 1 d i The results show that after laser irradiation, the particle size is about 2 nm, forming a metastable alloy structure. Figure 2 d ii Display: The metal particles are the smallest and most uniform, exhibiting a highly dispersed core-shell or alloy structure.

[0105] Project 2: 0.5 g of the catalyst from each example and comparative example was loaded into a stainless steel fixed-bed reactor. The reaction temperature was controlled at 200℃ and the reaction pressure at 2.5 MPa. A methanol solution of dimethyl oxalate (DMO) and hydrogen gas (molar ratio of DMO to methanol 1:10, molar ratio of hydrogen to DMO 50:1) were introduced into the reactor and passed through the catalyst bed. The space velocity of the methanol solution of DMO was 0.3 h⁻¹. -1 .

[0106] When using the catalysts of Comparative Example 1, Example 1, Comparative Example 2, and Example 2, the reaction was carried out continuously for 5 hours, and the DMO conversion and MG selectivity were tested every hour. The results are shown in [Figure Number]. Figure 2 .in, Figure 2 e represents the result corresponding to Comparative Example 1. Figure 2f is the result corresponding to Example 1, Figure 2 g is the result corresponding to Comparative Example 2, Figure 3 h is the result corresponding to Example 2, EG refers to ethylene glycol, which is a byproduct of the catalytic hydrogenation of DMO to MG.

[0107] When the catalyst of Example 2 is used, the reaction is continuously carried out for 300 hours, and the DMO conversion rate and the MG selectivity are tested every 10 hours, and the results are shown in Table 1. ​ .

[0108] When the catalysts of the examples and the comparative examples are used, the reaction is continuously carried out for 5 hours, and the DMO conversion rate and the MG selectivity after 5 hours are recorded in Table 1.

[0109] Table 1

[0110]

[0111] It can be seen that the DMO conversion rate and the MG selectivity of the catalyst of Example 1 are better than those of Comparative Example 1, and the DMO conversion rate and the MG selectivity of the catalyst of Example 2 are better than those of Comparative Example 2. It can be seen that after laser irradiation, the catalytic efficiency of the catalyst can be significantly improved. Except for Example 1, the DMO conversion rate of each example is ≥95%, and the MG selectivity is ≥90%. The DMO conversion rate of the catalyst of Example 2 remains above 98% in a long-time DMO hydrogenation reaction, and the MG selectivity is stable at 97%. Reflecting its catalytic life exceeds 300 hours, and the performance is stable without obvious decline.

[0112] The technical features of the above-described examples can be combined in any manner. In order to make the description simple, all possible combinations of the technical features in the above-described examples are not described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the description.

[0113] The above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent of the present application should be subject to the appended claims.

Claims

1. A method for preparing a catalyst for the preparation of methyl glycolate, characterized in that, Includes the following steps: Copper and silver salts are loaded onto a support to obtain a catalyst precursor, wherein the support is made of silicon dioxide and is modified with amino groups. The catalyst precursor was subjected to electromagnetic radiation treatment to obtain a modified catalyst precursor. The modified catalyst precursor is subjected to a reduction treatment, so that the copper salt supported on the support is reduced to elemental copper, and the silver salt supported on the support is reduced to elemental silver. The electromagnetic radiation treatment includes a combination of one or more of laser scanning treatment and high-frequency electromagnetic field treatment, wherein the electromagnetic field of the high-frequency electromagnetic field treatment is formed by an induction heating coil or an electromagnetic resonant cavity. The wavelength of the laser scanning process is 1050nm~1080nm, and the functional density of the laser scanning process is 1×10⁻⁶. 6 W / cm 2 ~1×10 8 W / cm 2 The scanning rate of the laser scanning process is 1 mm / s to 120 mm / s, and the number of scans of the laser scanning process is 1 to 3. The frequency of the high-frequency electromagnetic field treatment is 10MHz to 300MHz, the power of the high-frequency electromagnetic field treatment is 1.5kW to 2.5kW, and the time of the high-frequency electromagnetic field treatment is 10min to 20min.

2. The method for preparing the catalyst for preparing methyl glycolate according to claim 1, characterized in that, The carrier has mesopores.

3. The method for preparing the catalyst for preparing methyl glycolate according to any one of claims 1 to 2, characterized in that, Loading the copper salt and silver salt onto the carrier includes the following steps: The carrier is immersed in a solution containing copper and silver salts, then removed and dried.

4. The method for preparing the catalyst for preparing methyl glycolate according to claim 3, characterized in that, The copper salt includes one or more of copper nitrate, copper lactate, copper acetate, and copper chloride.

5. The method for preparing the catalyst for preparing methyl glycolate according to claim 3, characterized in that, The silver salt includes one or more of silver nitrate, silver lactate, silver acetate, and silver chloride.

6. The method for preparing the catalyst for preparing methyl glycolate according to claim 3, characterized in that, The solvent for solutions containing the copper and silver salts includes ethanol.

7. The method for preparing the catalyst for preparing methyl glycolate according to claim 3, characterized in that, Includes at least one of the following features: (1) The mass ratio of the carrier to the copper salt is 1:(1~2); (2) The mass ratio of the carrier to the silver salt is 1:(0.5~1); (3) The carrier is immersed in the solution containing the copper salt and silver salt for 20h~28h.

8. The method for preparing a catalyst for the preparation of methyl glycolate according to any one of claims 1 to 2, 4 to 7, characterized in that, The reduction process satisfies at least one of the following conditions: (1) The temperature of the reduction treatment is 250℃~350℃; (2) The reduction process takes 1 to 3 hours; (3) The atmosphere of the reduction treatment includes hydrogen.

9. A catalyst for the preparation of methyl glycolate, characterized in that, It is prepared by any one of the preparation methods according to claims 1 to 8.

10. A method for preparing methyl glycolate, characterized in that, Includes the following steps: In the presence of a catalyst, dimethyl oxalate reacts with hydrogen to produce methyl glycolate; wherein the catalyst is as described in claim 9.

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