Supported catalyst, process for its preparation and use thereof

Abstract

The application discloses a supported catalyst and a preparation method and application thereof. The supported catalyst is composed of a carrier and Cu and phosphorus oxide supported on the surface of the carrier; the carrier is at least one selected from SiO2, Al2O3, ZnO, CeO2, ZrO2, MgO, Fe3O4, activated carbon and a molecular sieve; wherein the mass content of Cu is 5-30 wt%, the mass content of the phosphorus oxide is 0.01-10 wt%, and the rest is the carrier. The supported catalyst is used for catalyzing the hydrogenation of dimethyl oxalate to prepare methyl glycolate in a high-temperature range (250-300 DEG C). After the introduction of the auxiliary agent, the selectivity of the copper catalyst to the methyl glycolate product in the high-temperature range can be significantly improved, the high-temperature range is beneficial to improving the conversion rate of the dimethyl oxalate and the stability of the catalyst, and thus a higher yield of the target product can be obtained.

Description

Technical Field

[0001] This application relates to a supported catalyst, its preparation method, and its application, and belongs to the field of catalysts. Background Technology

[0002] While single-use plastic products bring great convenience to our lives, they also place a heavy burden on the environment, leading to increasingly serious white pollution and damaging our living environment with non-degradable plastic waste. my country's policies require that biodegradable plastics account for more than 70% of plastic products in the next few years. This indicates a rapidly growing demand for biodegradable plastics and a huge market potential. However, the high cost of raw material production has significantly hindered the promotion and practical application of biodegradable plastics, necessitating the development of inexpensive production technologies to reduce their price. In recent years, the rapid increase in my country's coal-to-ethylene glycol (EG) production capacity via dimethyl oxalate (DMO) has exacerbated the contradiction with the overly singular downstream applications, resulting in overcapacity in coal-to-EG production and low plant operating rates. Production enterprises urgently need to find new profit growth points. Research shows that methyl glycolate (MG), the initial hydrogenation product of DMO, is an important precursor to the fully biodegradable plastic polyglycolic acid (PGA). If the same technical route and equipment can be used to extend the industrial chain and change the target product from EG to MG, it is possible to achieve the co-production of PGA biodegradable materials from coal-to-ethylene glycol. This will not only improve the utilization rate of the equipment, diversify its use, and enhance competitiveness, but also significantly reduce the cost of biodegradable plastics.

[0003] The hydrogenation of dimethyl oxalate (DMO) is a multi-step cascade reaction. Initial hydrogenation produces methyl glycolate (MG), which is further hydrogenated to ethylene glycol and ethanol. Therefore, to obtain MG with high selectivity, the depth of DMO hydrogenation must be controlled to avoid deep hydrogenation reactions. According to current literature, metallic copper is easily oxidized to monovalent copper, which has a strong hydrogenation capacity. At low temperatures (170-200℃), monovalent copper can efficiently catalyze the deep hydrogenation of DMO, primarily yielding ethylene glycol and ethanol, with very little MG formation. Furthermore, once a small amount of MG is formed, it is difficult to desorb under low-temperature conditions, and the active sites are covered, leading to rapid catalyst deactivation (e.g., Chinese patents CN101411990A, CN105085167A, CN104923228A, CN104248952A). Previous studies have found that by using high-energy plasma bombardment during sputtering to alter the electronic structure of copper atoms, the escape energy of its outer electrons can be increased, fundamentally changing the chemical properties of copper. This gives copper antioxidant capabilities similar to noble metals, inhibits the formation of monovalent copper, and thus cuts off further hydrogenation reactions of MG. Compared with copper catalysts prepared by the traditional ammonia stripping method, this technology maintains high MG selectivity at a higher temperature range, not only modifying the product from ethylene glycol (190℃, 98% selectivity) to methyl glycolate (240℃, 85% selectivity), but also extending the reaction temperature range from 170-200℃ to 200-240℃.

[0004] (ZL201811024584.0). However, monovalent copper species are not only the active sites for further hydrogenation of MG, but also important sites for promoting the activation and conversion of DMO. Inhibiting monovalent copper can regulate the selectivity of MG, but it also results in the loss of some catalytic activity and sacrifices the DMO conversion rate. The boiling points of DMO and MG are very close. When both coexist in the product, subsequent distillation separation will result in the loss of a significant amount of the target product MG. Therefore, for industrial applications, in addition to ensuring high MG selectivity, achieving efficient DMO conversion and improving catalyst stability are equally important.

[0005] Therefore, existing Cu-based catalysts need to be optimized and modified to further control their selectivity for hydrogenation products. Currently, the optimization methods mainly include the following:

[0006] 1. Adding noble metals such as Au, Ag, Pt, and Ru to Cu-based catalysts can improve the selectivity of methyl glycolate (e.g., Chinese patents CN101954288A, CN101700496A, CN10233666A, CN102463122A, CN101700496A, etc.), but this method still cannot avoid the use of expensive noble metals.

[0007] 2. Adding additives such as Mn, Zn, Zr, Co, Ni, and La to Cu catalysts can improve the selectivity of methyl glycolate (e.g., Chinese patents CN103785408A and CN 108325532 A). However, due to the limitations of the preparation method (ammonia stripping method), only SiO2 can be used as the support, which has certain limitations.

[0008] 3. Controlling reaction conditions to achieve highly selective production of methyl glycolate under specific conditions (such as Chinese patents CN108017539A and CN102989490B). This method is very sensitive to reaction conditions and has high requirements for reaction equipment and processes. Summary of the Invention

[0009] To address the problems in the prior art, this invention first modifies the support material by introducing a phosphorus additive via impregnation, and then loads active copper metal onto the support using a sputtering method. The objective of this invention is to provide a simple, low-cost, and easy-to-use copper-based catalyst for the highly selective hydrogenation of dimethyl oxalate to methyl glycolate, further increasing the reaction temperature range to 250-300℃ and improving DMO conversion while maintaining high MG selectivity.

[0010] According to one aspect of this application, a supported catalyst is provided, the supported catalyst comprising a support and Cu and phosphorus oxides supported on the surface of the support;

[0011] The support is selected from at least one of SiO2, Al2O3, ZnO, CeO2, ZrO2, MgO, Fe3O4, activated carbon, and molecular sieve;

[0012] The Cu content is 5–30 wt%, the phosphorus oxide content is 0.01–10 wt%, and the remainder is a carrier.

[0013] According to another aspect of this application, a method for preparing the above-mentioned supported catalyst is provided, characterized in that,

[0014] Includes the following steps:

[0015] The support was immersed in a solvent solution containing a phosphorus source, dried, and calcined to obtain a catalyst precursor, which was then spin-sputtered with copper as the target to obtain the supported catalyst.

[0016] The phosphorus source is selected from at least one of ammonium phosphate, disodium hydrogen phosphate, phosphoric acid, and phosphomolybdic acid;

[0017] The solvent is selected from at least one of water, methanol, ethanol, acetic acid, and acetylacetone.

[0018] The soaking time is 1 to 12 hours;

[0019] The drying temperature is 70–110°C;

[0020] The drying time is 1 to 5 hours;

[0021] The roasting temperature is 200–500°C;

[0022] The roasting time is 1 to 4 hours.

[0023] The rotary sputtering uses a rotating barrel;

[0024] The rotating drum is evacuated to a pressure of 9.9 × 10⁻⁶. -4 Below Pa;

[0025] Optionally, the rotating drum is evacuated to a pressure of 9.9 × 10⁻⁶. -6 ~9.9×10 -4 Pa;

[0026] Ar gas is introduced into the rotating barrel;

[0027] The flow rate of the Ar gas is 10–50 ml / min;

[0028] Optionally, the flow rate of the Ar gas is 12–30 ml / min;

[0029] After introducing Ar gas, maintain the pressure in the rotating barrel at 0.5–3 Pa;

[0030] Optionally, after introducing Ar gas, the pressure in the rotating barrel is maintained at 1 to 1.5 Pa;

[0031] The voltage of the plasma generator is 400–470V;

[0032] Optionally, the voltage of the plasma generator is 420–450V;

[0033] The rotating drum rotates at a speed of 1 to 20 rpm;

[0034] Optionally, the rotating drum rotates at a speed of 5 to 10 rpm;

[0035] After sputtering, an O2 / Ar mixture is introduced until the pressure reaches atmospheric pressure;

[0036] The volume concentration of oxygen in the O2 / Ar mixture is 0.5% to 5%.

[0037] Optionally, the volume concentration of oxygen in the O2 / Ar mixture is 1-3%.

[0038] According to another aspect of this application, a method for preparing methyl glycolate by catalytic hydrogenation of dimethyl oxalate is provided, wherein hydrogen gas and dimethyl oxalate are contacted with a catalyst and reacted to obtain methyl glycolate.

[0039] The catalyst is the supported catalyst described above.

[0040] The molar ratio of hydrogen to dimethyl oxalate is 20 to 200.

[0041] Optionally, the molar ratio of hydrogen to dimethyl oxalate is 80 to 150.

[0042] The liquid hourly space velocity (LISH) of the dimethyl oxalate is 0.1–10.0 h⁻¹. -1 ;

[0043] Optionally, the liquid hourly space velocity (LISH) of the dimethyl oxalate is 0.2–2.0 h⁻¹. -1 .

[0044] The beneficial effects that this application can produce include:

[0045] (1) Compared with copper catalysts prepared by sputtering without additive modification, the reaction temperature range can be further broadened, the conversion rate of DMO can be improved, and the yield of MG can be increased.

[0046] (2) The additive components and additive modification methods proposed in this invention are only applicable to copper catalysts prepared by sputtering, and cannot achieve significant beneficial effects on copper catalysts prepared by the traditional ammonia stripping method.

[0047] (3) In this invention, the copper catalyst can selectively catalyze the hydrogenation of dimethyl oxalate to methyl glycolate at higher temperatures, thus avoiding the problem of catalyst deactivation caused by methyl glycolate covering the active sites at low temperatures. Attached Figure Description

[0048] Figure 1 The image shows the Cu 2p energy spectrum of the catalyst in Example 1.

[0049] Figure 2 The p 2p energy spectrum of the catalyst in Example 1 is shown.

[0050] Figure 3 The Si 2p energy spectrum of the catalyst in Example 1 is shown.

[0051] Figure 4 The O1s energy spectrum of the catalyst in Example 1 is shown.

[0052] Figure 5 X-ray diffraction patterns of the catalyst in Example 1, both fresh and after reaction.

[0053] Figure 6 This is a transmission electron microscope (TEM) image of the catalyst in Example 1.

[0054] Figure 7 This is a stability test for Example 2. Detailed Implementation

[0055] The technical details of this invention are described in detail in the following embodiments. It should be noted that the embodiments are only intended to further illustrate the technical features of this invention, and are not intended to limit the invention.

[0056] Example 1

[0057] Step 1: Modification of the support. Dissolve 125 μL of phosphoric acid in an appropriate amount of water to prepare a phosphoric acid precursor solution, then add 30 g of SiO2 support (particle size 100-120 nm, specific surface area 267 m²). 2 / g) was impregnated in the above precursor solution, stirred evenly, and allowed to stand for 12 hours. It was then dried at 80°C for 10 hours and calcined at 400°C for 2 hours to obtain the P-modified SiO2 support, denoted as 0.25P-SiO2.

[0058] Step 2: Loading active metallic copper. Place the P-SiO2 support in a rotating drum, and evacuate the drum until the pressure reaches 9.9 × 10⁻⁶. -4 Below Pa, high-purity Ar gas was introduced into the tank until the pressure reached 1.0 Pa. The voltage of the Ar ion generator was adjusted to 300 W, and the rotation speed of the tank was increased to 10 rpm, so that the nano-sized copper particles generated by Ar ion bombardment of the copper target were uniformly deposited on the surface of the support. Sputtering was carried out for 1 hour. After sputtering, a mixture of O2 / Ar gas with a volume content of 1% was introduced into the tank until the pressure reached atmospheric pressure. After testing, a Cu / P-SiO2 catalyst with a Cu mass loading of 12% and a P mass percentage of 0.25% was obtained, denoted as SP-Cu / 0.25P-SiO2.

[0059] 0.5 g of the prepared SP-Cu / 0.25P-SiO2 catalyst was loaded into a reactor and reduced at 250 °C for 4 hours. The reaction mixture was then introduced with a H2 to dimethyl oxalate (DMO) molar ratio of 150. The reaction temperature was 270 °C, the pressure was 3.0 MPa, and the liquid hourly space velocity (LISH) was 0.5 h⁻¹. -1 The results showed that the conversion rate of dimethyl oxalate was 76.6%, the selectivity of methyl glycol was 82.2%, the selectivity of ethylene glycol was 11.7%, the selectivity of ethanol was 0.6%, the selectivity of C3-C4 alcohols was 0.0%, the selectivity of other products was 5.5%, and the yield of methyl glycolate was 63.0%.

[0060] Example 2

[0061] The catalyst preparation and reaction conditions were the same as in Example 1, except that the reaction temperature was 260°C. The results showed that the conversion rate of dimethyl oxalate was 84.0%, the selectivity for methyl glycol was 86.2%, the selectivity for ethylene glycol was 11.50%, the selectivity for ethanol was 0.1%, the selectivity for C3-C4 alcohols was 0.0%, the selectivity for other products was 2.2%, and the yield of methyl glycolate was 72.4%.

[0062] Example 3

[0063] The catalyst preparation and reaction conditions were the same as in Example 1, except that the reaction temperature was 250°C. The results showed that the conversion rate of dimethyl oxalate was 77.3%, the selectivity for methyl glycol was 88.3%, the selectivity for ethylene glycol was 9.9%, the selectivity for ethanol was 0.0%, the selectivity for C3-C4 alcohols was 0.1%, the selectivity for other products was 1.8%, and the yield of methyl glycolate was 68.3%.

[0064] Example 4

[0065] The catalyst preparation steps were the same as in Example 1, except that the content of the promoter P in step one was 0.015%, and the resulting catalyst was designated SP-Cu / 0.015P-SiO2. The reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 99.2%, the selectivity for methyl glycol was 24.9%, the selectivity for ethylene glycol was 54.5%, the selectivity for ethanol was 3.7%, the selectivity for C3-C4 alcohols was 1.4%, the selectivity for other products was 15.5%, and the yield of methyl glycolate was 24.7%.

[0066] Example 5

[0067] The catalyst preparation steps were the same as in Example 1, except that the content of the promoter P in step one was 0.1%, and the resulting catalyst was designated SP-Cu / 0.1P-SiO2. The reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 98.0%, the selectivity for methyl glycol was 49.6%, the selectivity for ethylene glycol was 47.0%, the selectivity for ethanol was 0.6%, the selectivity for C3-C4 alcohols was 0.3%, the selectivity for other products was 2.5%, and the yield of methyl glycolate was 48.6%.

[0068] Example 6

[0069] The catalyst preparation steps were the same as in Example 1, except that the content of the promoter P in step one was 0.5%, and the resulting catalyst was designated SP-Cu / 0.5P-SiO2. The reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 99.2%, the selectivity of methyl glycol was 58.2%, the selectivity of ethylene glycol was 37.9%, the selectivity of ethanol was 0.5%, the selectivity of C3-C4 alcohols was 0.1%, the selectivity of other products was 3.3%, and the yield of methyl glycolate was 57.7%.

[0070] Example 7

[0071] The catalyst preparation steps were the same as in Example 1, except that the content of the promoter P in step one was 1%, and the resulting catalyst was designated SP-Cu / 1P-SiO2. The reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 99.7%, the selectivity for methyl glycol was 35.9%, the selectivity for ethylene glycol was 59.1%, the selectivity for ethanol was 1.4%, the selectivity for C3-C4 alcohols was 0.3%, and the selectivity for other products was 3.3%. The yield of methyl glycolate was 35.8%.

[0072] Example 8

[0073] The catalyst preparation and reaction conditions were the same as in Example 7, except that the reaction temperature was 260°C. The results showed that the conversion rate of dimethyl oxalate was 98.5%, the selectivity for methyl glycol was 48.1%, the selectivity for ethylene glycol was 48.6%, the selectivity for ethanol was 0.8%, the selectivity for C3-C4 alcohols was 0.2%, the selectivity for other products was 2.3%, and the yield of methyl glycolate was 47.4%.

[0074] Example 9

[0075] The catalyst preparation and reaction conditions were the same as in Example 7, except that the reaction temperature was 250°C. The results showed that the conversion rate of dimethyl oxalate was 98.5%, the selectivity for methyl glycol was 51.7%, the selectivity for ethylene glycol was 46.3%, the selectivity for ethanol was 0.4%, the selectivity for C3-C4 alcohols was 0.2%, the selectivity for other products was 1.4%, and the yield of methyl glycolate was 50.9%.

[0076] Example 10

[0077] The catalyst preparation steps were the same as in Example 1, except that the content of the promoter P in step one was 2%, and the resulting catalyst was designated SP-Cu / 2P-SiO2. The reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 99.7%, the selectivity of methyl glycol was 28.3%, the selectivity of ethylene glycol was 66.5%, the selectivity of ethanol was 1.9%, the selectivity of C3-C4 alcohols was 0.4%, the selectivity of other products was 2.9%, and the yield of methyl glycolate was 28.2%.

[0078] Comparative Example 1

[0079] The catalyst preparation steps were the same as in Example 1, except that no auxiliary agent P was added in step one. The reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 98.7%, the selectivity of methyl glycolate was 12.0%, the selectivity of ethylene glycol was 56.0%, the selectivity of ethanol was 8.4%, the selectivity of C3-C4 alcohols was 1.4%, the selectivity of other products was 22.2%, and the yield of methyl glycolate was 11.8%.

[0080] Comparative Example 2

[0081] Step 1: Modification of the support. Dissolve 10 μL of phosphoric acid in an appropriate amount of water to prepare a phosphoric acid precursor solution, then add 30 g of SiO2 support (particle size 100-120 nm, specific surface area 267 m²). 2 / g) was impregnated in the above precursor solution, stirred evenly, and allowed to stand for 12 hours. It was then dried at 80°C for 10 hours and calcined at 400°C for 2 hours to obtain the P-modified SiO2 support, denoted as 0.02P-SiO2.

[0082] Step 2: Preparation of Cu / SiO2 catalyst by ammonia stripping method. Weigh 15.2 g Cu(NO3)2·6H2O into 210 mL of deionized water, and add 21 mL of concentrated ammonia dropwise; weigh 16.0 g SiO2 support and add it to the above solution while stirring continuously. Place the beaker in a 40℃ water bath for 4 h; raise the temperature to 90℃ and strip ammonia for about 2 h; wash the obtained solid with deionized water until the conductivity drops to 100 Ω. -1 The solid was transferred into a crucible and dried in an oven at 120°C for 12 hours. The dried solid was then placed in a muffle furnace and calcined at 400°C for 2 hours. The resulting catalyst had a Cu mass fraction of 16%, denoted as AE-Cu / 0.02P-SiO2.

[0083] The catalyst reaction conditions were the same as in Example 1. The results showed that the conversion rate of dimethyl oxalate was 99.8%, the selectivity of methyl glycolate was 0.1%, the selectivity of ethylene glycol was 0.1%, the selectivity of ethanol was 36.4%, the selectivity of C3-C4 alcohols was 28.8%, the selectivity of other products was 34.6%, and the yield of methyl glycolate was 0.1%.

[0084] Example 11

[0085] The SP-Cu / 0.25P-SiO2 catalyst prepared in Example 1 was analyzed using X-ray photoelectron spectroscopy (XPS). The XPS results are shown below. Figure 1-4 .

[0086] Example 12

[0087] The fresh SP-Cu / 0.25P-SiO2 catalyst prepared in Example 1 and the SP-Cu / 0.25P-SiO2 catalyst sample after reaction were subjected to X-ray diffraction analysis. The results are shown in the figure. Figure 5 Both fresh and post-reaction copper species on the catalyst are metallic zero-valent copper.

[0088] Example 13

[0089] The SP-Cu / 0.25P-SiO2 catalyst prepared in Example 1 was analyzed using high-resolution transmission electron microscopy. The transmission electron microscopy images are shown below. Figure 6 The Cu particles on the catalyst are mostly 2-4 nm in size, and the P particles are uniformly dispersed on the catalyst.

[0090] The results from the above examples demonstrate that the catalyst of this invention, with the addition of P as an additive, can produce methyl glycolate with high selectivity over a wider high-temperature range, achieving a greater methyl glycolate yield. The product selectivity is less sensitive to temperature, making it more adaptable to temperature fluctuations in practical industrial applications. The conversion rate of dimethyl oxalate and the selectivity of methyl glycolate can both reach over 80%. A special interaction exists between Cu prepared by sputtering and the additive P; under the same conditions, adding P as an additive to Cu / SiO2 prepared by ammonia stripping cannot achieve this effect.

[0091] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A supported catalyst, characterized in that, The supported catalyst consists of a support and Cu and phosphorus oxides supported on the surface of the support; The support is selected from at least one of SiO2, Al2O3, ZnO, CeO2, ZrO2, MgO, Fe3O4, activated carbon, and molecular sieve; The Cu content is 5–30 wt%, the phosphorus oxide content is 0.01–10 wt%, and the remainder is a carrier.

2. A method for preparing the supported catalyst according to claim 1, characterized in that, Includes the following steps: The support was immersed in a solvent solution containing a phosphorus source, dried, and calcined to obtain a catalyst precursor, which was then spin-sputtered with copper as the target to obtain the supported catalyst.

3. The preparation method according to claim 2, characterized in that, The phosphorus source is selected from at least one of ammonium phosphate, disodium hydrogen phosphate, phosphoric acid, and phosphomolybdic acid; The solvent is selected from at least one of water, methanol, ethanol, acetic acid, and acetylacetone.

4. The preparation method according to claim 2, characterized in that, The soaking time is 1 to 12 hours; The drying temperature is 70–110°C; The drying time is 1 to 5 hours; The roasting temperature is 200–500°C; The roasting time is 1 to 4 hours.

5. The preparation method according to claim 2, characterized in that, The rotary sputtering uses a rotating barrel; The rotating drum is evacuated to a pressure of 9.9 × 10⁻⁶. -4 Below Pa; Preferably, the rotating drum is evacuated to a pressure of 9.9 × 10⁻⁶. -6 ~9.9×10 -4 Pa; Ar gas is introduced into the rotating barrel; The flow rate of the Ar gas is 10–50 ml / min; Preferably, the flow rate of the Ar gas is 12–30 ml / min; After introducing Ar gas, maintain the pressure in the rotating barrel at 0.5–3 Pa; Preferably, after introducing Ar gas, the pressure in the rotating barrel is maintained at 1 to 1.5 Pa; The voltage of the plasma generator is 400–470V; Preferably, the voltage of the plasma generator is 420–450V; The rotating drum rotates at a speed of 1 to 20 rpm; Preferably, the rotating drum rotates at a speed of 5 to 10 rpm; After sputtering, an O2 / Ar mixture is introduced until the pressure reaches atmospheric pressure; The volume concentration of oxygen in the O2 / Ar mixture is 0.5% to 5%. Preferably, the volume concentration of oxygen in the O2 / Ar mixture is 1-3%.

6. A method for preparing methyl glycolate by catalytic hydrogenation of dimethyl oxalate, characterized in that, Hydrogen gas and dimethyl oxalate are reacted with a catalyst to produce methyl glycolate. The catalyst is the supported catalyst as described in claim 1.

7. The method according to claim 6, characterized in that, The molar ratio of hydrogen to dimethyl oxalate is 20 to 200. Preferably, the molar ratio of hydrogen to dimethyl oxalate is 80 to 150.

8. The method according to claim 6, characterized in that, The liquid hourly space velocity (LISH) of the dimethyl oxalate is 0.1–10.0 h⁻¹. -1 ; Preferably, the liquid hourly space velocity (LISH) of the dimethyl oxalate is 0.2–2.0 h⁻¹. -1 .

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