Heterogeneous catalyst for preparing methyl formate through CO esterification as well as preparation method and application of heterogeneous catalyst

Abstract

The invention discloses a heterogeneous catalyst for preparing methyl formate through CO esterification and a preparation method and application of the heterogeneous catalyst, and belongs to the field of methyl formate synthesis. The heterogeneous catalyst comprises a palladium active component, an auxiliary agent and a carrier, the auxiliary agent is selected from La and / or Ce; the loading capacity of the palladium active component is 0.01-0.6% of the mass of the carrier; and the loading capacity of the auxiliary agent is 0.01-10% of the mass of the carrier. Compared with a catalyst auxiliary agent reported in the literature, the rare earth auxiliary agent disclosed by the invention can enhance the interaction between the precious metal and the carrier, effectively improve the utilization rate of the precious metal, reduce the dosage of the precious metal and the production cost of the catalyst, and remarkably improve the economical efficiency of the technology. The preparation method disclosed by the invention is simple in process, easy to realize large-scale amplification and excellent in catalyst performance, and can be applied to a production technology for preparing methyl formate through CO esterification.

Description

Technical Field

[0001] The present application relates to a multiphase catalyst for preparing methyl formate by CO esterification, a preparation method and application thereof, and belongs to the field of methyl formate synthesis. Background Art

[0002] Methyl formate is a carbon-one chemical product with a wide range of uses and is an important chemical intermediate. In the chemical industry, it can be hydrolyzed to produce formic acid, ammonolyzed to produce formamide, and isomerized to produce acetic acid. In agriculture, it can be used as a fumigant and fungicide for dried fruits and grains. It is also a synthetic raw material for many pharmaceutical drugs.

[0003] There are many methods for producing methyl formate, such as methanol formate esterification, liquid-phase methanol carbonylation, and direct synthesis gas synthesis. However, the main technology currently used in the domestic industry is the liquid-phase methanol carbonylation method. This method has serious disadvantages: (1) the catalyst sodium methoxide is sensitive to water, and the impurity water in the raw material methanol needs to be purified, resulting in a high cost for raw material purification; (2) the liquid-phase methanol carbonylation method uses a homogeneous catalytic system, and the separation of the product methyl formate and the catalyst is difficult; (3) the catalyst sodium methoxide has a low solubility in methyl formate and is easy to clog pipes and valves, which brings difficulties to actual operation.

[0004] Therefore, it is of great significance to develop a heterogeneous catalytic system to achieve the production of methyl formate. Patent 201410141259.8 reports a catalyst for synthesizing methyl formate from methyl nitrite and its preparation method, which uses a fixed bed reactor, and the raw materials are carbon monoxide, nitrogen, hydrogen and methyl nitrite, which can be used to synthesize methyl formate, and the conversion rate of the raw materials, the selectivity of the product and the time-space yield are all high. Patent 202410095678.6 reports a high thermal conductivity CO esterification catalyst for methyl formate, which uses a high thermal conductivity SiC carrier, which can effectively reduce the hot spot temperature of the reactor and proposes a solution for the safe and efficient operation of the reactor.

[0005] The palladium-based catalysts for the preparation of methyl formate by CO esterification reported so far have a high content of precious metals, and the cost of precious metals accounts for as much as 80-90% of the total catalyst cost, which results in high costs for precious metal raw materials, processing losses, and secondary recycling in the production of catalysts, which is at a disadvantage in terms of catalyst cost compared to the liquid phase methanol carbonylation method. In addition, the reaction of carbon monoxide esterification to methyl formate is highly exothermic, and the operating window of the reaction temperature that is conducive to the formation of the target product methyl formate is very narrow. A high loading of precious metals is prone to the appearance of high-temperature hot spots in the catalyst bed, which not only causes the rapid occurrence of side reactions, but also leads to a significant decrease in the selectivity of the target product and the conversion rate of the reactants, thereby increasing the energy consumption and material consumption of the process. Therefore, in order to enhance the economic efficiency of the CO esterification technology for preparing methyl formate, it is necessary to develop a catalyst with low palladium loading, excellent activity and selectivity, which is of great significance for the practical application of the technology. Summary of the invention

[0006] The reported palladium-based catalyst for preparing methyl formate by CO esterification has a high precious metal content, resulting in a high catalyst production cost and the catalyst is prone to hot spot temperatures in the bed of a fixed bed reactor, which is not conducive to catalyst loading and reactor control. Therefore, the present invention provides a low palladium loading, high activity, high selectivity supported palladium-based nanocatalyst and a preparation method and application thereof.

[0007] According to the first aspect of the present application, a multiphase catalyst for preparing methyl formate by CO esterification is provided. Rare earth lanthanum and cerium are used as catalyst additives, and lanthanum and cerium can effectively enhance the interaction between precious metals and carriers, improve the utilization rate of precious metals, and reduce the amount of precious metals and catalyst production costs; and in a fixed tubular reactor, a catalyst with high atomic utilization and low loading not only has better performance, but also is easy to load the catalyst, and the reactor can operate efficiently and stably.

[0008] A multiphase catalyst for preparing methyl formate by CO esterification, the multiphase catalyst comprising a palladium active component, an auxiliary agent and a carrier;

[0009] The auxiliary agent is selected from La and / or Ce;

[0010] The loading amount of the palladium active component is 0.01-0.6% of the carrier mass;

[0011] The loading amount of the auxiliary agent is 0.01-10% of the carrier mass.

[0012] Optionally, the loading amount of the palladium active component is 0.1-0.4% of the carrier mass;

[0013] The loading amount of the auxiliary agent is 0.02-5% of the carrier mass.

[0014] Optionally, the carrier is selected from silicon carbide and / or aluminum oxide.

[0015] According to the second aspect of the present application, a method for preparing the above-mentioned multiphase catalyst for preparing methyl formate by CO esterification is provided. Compared with the traditional impregnation method, the preparation method adopted by the invention not only has a low noble metal loading of the catalyst, but also has excellent catalytic performance, a simple preparation process, and is easy to scale up.

[0016] The method for preparing the heterogeneous catalyst comprises the following steps:

[0017] S1, immersing the support in a solution containing a palladium precursor and an auxiliary agent precursor, stirring evenly, heating to volatilize the solvent, drying, and calcining to obtain an intermediate product I;

[0018] S2, reacting, washing, and drying a mixed solution containing the intermediate product I, a reducing agent, a structure-directing reagent, and a protecting agent to obtain an intermediate product II;

[0019] S3, reducing the intermediate product II under a hydrogen atmosphere to obtain the heterogeneous catalyst.

[0020] Optionally, in step S1, the palladium precursor is selected from at least one of nitrate, halide, acetylacetonate, and acetate corresponding to palladium;

[0021] The auxiliary agent precursor is selected from at least one of lanthanum nitrate, lanthanum acetate, lanthanum chloride, cerium chloride, cerium nitrate and cerium acetate.

[0022] Optionally, in step S2, the reducing agent is selected from at least one of sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose, and ethylene glycol;

[0023] The structure-directing agent is selected from at least one of sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, citric acid, sodium citrate, potassium citrate, and ammonium citrate;

[0024] The protective agent is selected from at least one of polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

[0025] Optionally, in step S2, the reaction conditions are: the reaction temperature is 30-130° C., and the reaction time is 1-10 hours.

[0026] Optionally, in step S3, the reduction conditions are: the reduction temperature is 50-400° C., and the reduction time is 2-6 hours.

[0027] As a specific embodiment, the method for preparing the heterogeneous catalyst described above comprises the following steps:

[0028] 1. Optionally, immerse the carrier into water or acetone or methanol or ethanol solution containing a palladium precursor (any one of nitrate, halide, acetylacetonate, acetate or any combination of several compounds) and an auxiliary agent precursor (any one of lanthanum nitrate, lanthanum acetate, lanthanum chloride, cerium chloride, cerium nitrate, cerium acetate or any combination of several compounds), stir evenly, and evenly disperse the carrier into the solution of the palladium precursor and the auxiliary agent precursor;

[0029] 2. Rotate and evaporate the mixed solution of the palladium precursor, the auxiliary agent precursor and the carrier obtained in step 1 under heating conditions until the solvent of the solution evaporates, so that the palladium precursor and the auxiliary agent precursor are uniformly adsorbed on the surface of the carrier;

[0030] 3. The adsorption sample obtained in step 2 is vacuum dried at 40-200° C. for 0.5-10 hours, and then calcined at 200-600° C. for 1-10 hours;

[0031] 4. Add a reducing agent, a structure-directing reagent (one or a combination of any of the following compounds: sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose, and ethylene glycol), a structure-directing reagent (one or a combination of any of the following compounds: sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, citric acid, sodium citrate, potassium citrate, and ammonium citrate) and a protective agent (one or a combination of any of the following compounds: polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) to the sample obtained in step 3 to carry out a reduction reaction at 30-130° C.;

[0032] 5. Filter and wash the sample obtained in step 4, and dry it in a vacuum drying oven for 1-10 hours;

[0033] 6. The sample obtained in step 5 is reduced under a pure hydrogen atmosphere at 50-400° C. for 2-6 hours to obtain a low-loaded supported nano-palladium-based heterogeneous catalyst.

[0034] According to a third aspect of the present application, there is provided a use of the above-mentioned multiphase catalyst for preparing methyl formate by CO esterification in preparing methyl formate by CO esterification.

[0035] The application of the above-mentioned heterogeneous catalyst in the esterification of CO to methyl formate.

[0036] Optionally, a raw material gas containing methyl nitrite, carbon monoxide, hydrogen and nitrogen is contacted with a heterogeneous catalyst to react to obtain methyl formate;

[0037] The volume content of methyl nitrite is 5-30%, the volume content of carbon monoxide is 5-60%, the volume content of hydrogen is 5-20%, and the volume content of nitrogen is 5-75%;

[0038] Airspeed 500-5000h -1 , temperature is 50-200℃, pressure is 0.01-5MPa.

[0039] The beneficial effects of this application include:

[0040] The low palladium loading heterogeneous catalyst for preparing methyl formate by CO esterification provided by the present application, rare earth lanthanum and cerium as catalyst additives, rare earth additives can enhance the interaction between precious metals and carriers, effectively improve the utilization rate of precious metals, reduce the amount of precious metals and the production cost of catalysts, and significantly improve the economy of the technology. At the same time, the low palladium loading heterogeneous catalyst can reduce the hot spot temperature in the reactor, which is conducive to the stable operation of the reactor, and the catalyst loading is simple and easy, and high space-time yield can be achieved without gradient loading. The preparation method adopted by the present invention is simple in process, easy to realize large-scale amplification, and the catalyst has excellent performance, which can be applied to the production technology of preparing methyl formate by CO esterification, and methyl formate is obtained with high conversion rate and high selectivity. DETAILED DESCRIPTION

[0041] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0042] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0043] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0044] In the examples of the present application, the selectivity and space-time yield are calculated as follows:

[0045] In the examples of the present application, the selectivity and space-time yield of methyl formate were analyzed by gas chromatography and calculated based on the following formula:

[0046]

[0047] Wherein, A refers to relative correction coefficient = relative correction factor / molecular weight, MF refers to methyl formate, DMO refers to dimethyl oxalate, and DMC refers to dimethyl carbonate.

[0048] Example 1

[0049] 25g SiC and 25g alumina were weighed and impregnated into 37.5mL 37.6mmol / L potassium chloropalladate aqueous solution, and then 100ml 77mmol / L lanthanum nitrate aqueous solution was added, ultrasonic dispersion was performed for 1 hour, rotary stirring was performed for 2 hours, and then rotary evaporation was performed at 120°C for 1 hour, and calcination was performed at 500°C for 4 hours. Then 1g ascorbic acid, 3g sodium citrate, 2g polyvinyl pyrrolidone, and 50ml water were added, and the reaction was performed at 90°C for 1 hour. After washing, vacuum drying was performed at 80°C for 10 hours, and then reduction was performed again at 400°C in pure hydrogen atmosphere for 2 hours to obtain Pd-La / (SiC+Al2O3) used in CO esterification to methyl formate. 2 O 3 ) catalyst, the loading amount of Pd is 0.29% of the carrier mass, and the loading amount of the auxiliary agent La is 1.90% of the carrier mass.

[0050] Example 2

[0051] The operation is the same as in Example 1, except that an aqueous solution of cerium nitrate is used to obtain Pd-Ce / (SiC+Al) used in the CO esterification reaction to produce methyl formate. 2 O 3 ) catalyst, the loading amount of Pd is 0.28% of the carrier mass, and the loading amount of the auxiliary agent Ce is 1.85% of the carrier mass.

[0052] Comparative Example 1

[0053] Weigh 25g SiC and 25g alumina and immerse them in 62.5mL 37.6mmol / L palladium chloride aqueous solution, then add 10mL water, ultrasonically disperse for 1 hour, rotate and stir for 2 hours, then rotary evaporate at 120℃ for 1 hour, calcine at 500℃ for 4 hours, then add 1g ascorbic acid, 3g sodium citrate, 2g polyvinyl pyrrolidone, 50ml water, react at 90℃ for 1 hour, wash, vacuum dry at 80℃ for 10 hours, and then reduce again at 400℃ pure hydrogen atmosphere for 2 hours to obtain Pd / (SiC+Al2O3) used in CO esterification to methyl formate. 2 O 3 ) catalyst, the Pd loading amount is 0.45% of the support mass.

[0054] Comparative Example 2

[0055] Weigh 50g of aluminum oxide and immerse it in 62.5mL of 37.6mmol / L potassium chloropalladate aqueous solution, then add 10mL of water, ultrasonically disperse for 1 hour, rotate and stir for 2 hours, then rotary evaporate at 120℃ for 1 hour, calcine at 500℃ for 4 hours, and then reduce at 400℃ for 5 hours in a pure hydrogen atmosphere to obtain PdHx / Al2O3 for CO esterification to methyl formate. 2 O 3The Pd loading of the catalyst is 0.47% of the support mass.

[0056] Comparative Example 3

[0057] The operation is the same as in Example 1, except that an aqueous solution of copper nitrate is used to obtain Pd-Cu / (SiC+Al) used in the CO esterification reaction to produce methyl formate. 2 O 3 ) catalyst, the loading amount of Pd is 0.29% of the carrier mass, and the loading amount of the auxiliary agent Cu is 1.92% of the carrier mass.

[0058] Application Example 1

[0059] The catalysts of Example 1 and Comparative Example 1 were applied to the CO esterification reaction to produce methyl formate. The raw gas ratio was methyl nitrite: carbon monoxide: hydrogen: nitrogen = 20: 20: 10: 50 (volume ratio). The gas phase space velocity was 3000 h -1 The reaction temperature was 135°C, the reaction pressure was 0.1 MPa, the reactor dimensions were 20 cm in length and 8 mm in inner diameter, and the reaction results are shown in Table 1.

[0060] Table 1 Catalyst performance in the CO synthesis of methyl formate reaction

[0061]

[0062] Application Example 2

[0063] The catalysts prepared in Example 1 and Comparative Example 2 were evaluated for catalytic activity in a single tube fixed bed reactor. The tube reactor was 200 cm long and 25 mm in inner diameter. Five temperature detection points were set in the single tube reactor. The distance between each temperature detection point was 30 cm. From top to bottom, they were marked as T1, T2, T3, T4, and T5 respectively. The air velocity was 1000-3000 h -1 , the temperature of the heat transfer medium can be adjusted in the range of 90-135°C, the reaction pressure is 0.3MPa, the raw gas ratio is methyl nitrite: carbon monoxide: hydrogen: nitrogen = 20x: 20x: 10x: (100-50x) (volume ratio), x is adjusted according to the hot spot temperature on the catalyst bed in the reactor, when the bed temperature is less than 150 degrees Celsius, x can be increased, but when the catalyst bed is close to 150 degrees Celsius, x is stopped from increasing. The reaction results and catalyst bed temperature are shown in Table 2.

[0064] Table 2 Catalyst performance and bed temperature in single tube reactor

[0065]

[0066]

[0067] It can be analyzed from Table 1 that the Pd-La / (SiC+Al 2 O 3 ) catalyst, the introduction of the auxiliary agent lanthanum maintains high activity and high selectivity (its selectivity is comparable to that of Pd / (SiC+Al 2 O 3 ) is equivalent, and the time-space yield is slightly lower than that of Pd / (SiC+Al 2 O 3 ) catalyst), greatly reducing the precious metal loading (about 33%), while increasing the utilization of precious metals, so the introduction of lanthanum additives can significantly reduce the precious metal content and production cost of the catalyst. 2 O 3 ) catalyst, and also proved that Pd-Ce / (SiC+Al 2 O 3 ) catalyst has a slightly lower conversion rate and selectivity than Pd-La / (SiC+Al 2 O 3 ) catalyst, but it also proves that the introduction of the cerium additive can effectively reduce the precious metal content of the catalyst. 2 O 3 ) catalyst, proving that copper additives cannot achieve similar technical effects. While reducing the precious metal loading, the CO conversion rate decreased significantly.

[0068] According to the analysis in Table 2, in the single tube fixed bed reactor, although PdHx / Al 2 O 3 Although it is also a catalyst with excellent performance, the low thermal conductivity of the carrier and the high loading amount make it easy to overheat locally inside the reactor. In order to avoid the occurrence of runaway temperature, its production capacity is limited or a complex gradient loading scheme is required to solve this problem. In the loading of catalysts, a lot of manpower is consumed. 2 O 3 ) catalyst has a uniform temperature field in the reactor, and the production capacity of the reactor can be further improved by lowering the temperature of the heat transfer medium and continuously increasing the concentration of the reaction raw materials. The final performance is that in the same reactor, Pd-La / (SiC+Al 2 O 3 ) compared to PdHx / Al 2 O 3 The time-space yield is higher and the temperature field is more uniform (using Pd-La / (SiC+Al 2 O 3 ) catalyst, the maximum temperature difference between the highest and lowest beds is 6°C, while PdHx / Al 2 O3 The difference between the highest and lowest bed temperatures of the catalyst reaches about 27°C). Therefore, the catalyst using rare earth additives not only uses less precious metal in the catalyst and has lower catalyst production costs, but also has a more uniform temperature field in the single-tube fixed bed reactor, which is conducive to the efficient and stable operation of the reactor and makes the loading of the catalyst easier.

[0069] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A heterogeneous catalyst for preparing methyl formate by CO esterification, characterized in that: The heterogeneous catalyst comprises a palladium active component, a promoter and a carrier; The auxiliary agent is selected from La and / or Ce; The loading amount of the palladium active component is 0.01-0.6% of the carrier mass; The loading amount of the auxiliary agent is 0.01-10% of the carrier mass.

2. The multiphase catalyst according to claim 1, characterized in that The loading amount of the palladium active component is 0.1-0.4% of the carrier mass; The loading amount of the auxiliary agent is 0.02-5% of the carrier mass.

3. The multiphase catalyst according to claim 1, characterized in that The support is selected from silicon carbide and / or aluminum oxide.

4. The method for preparing a heterogeneous catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, immersing the support in a solution containing a palladium precursor and an auxiliary agent precursor, stirring evenly, heating to volatilize the solvent, drying, and calcining to obtain an intermediate product I; S2, reacting, washing, and drying a mixed solution containing the intermediate product I, a reducing agent, a structure-directing reagent, and a protecting agent to obtain an intermediate product II; S3, reducing the intermediate product II under a hydrogen atmosphere to obtain the heterogeneous catalyst.

5. The preparation method according to claim 4, characterized in that In step S1, the palladium precursor is selected from at least one of nitrate, halide, acetylacetonate, and acetate corresponding to palladium; The auxiliary agent precursor is selected from at least one of lanthanum nitrate, lanthanum acetate, lanthanum chloride, cerium chloride, cerium nitrate and cerium acetate.

6. The preparation method according to claim 4, characterized in that In step S2, the reducing agent is selected from at least one of sodium borohydride, hydrazine hydrate, ascorbic acid, formaldehyde, formic acid, sodium formate, sodium acetate, glucose, and ethylene glycol; The structure-directing agent is selected from at least one of sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, potassium iodide, citric acid, sodium citrate, potassium citrate, and ammonium citrate; The protective agent is selected from at least one of polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer.

7. The preparation method according to claim 4, characterized in that In step S2, the reaction conditions are: the reaction temperature is 30-130° C., and the reaction time is 1-10 hours.

8. The preparation method according to claim 4, characterized in that In step S3, the reduction conditions are: the reduction temperature is 50-400° C., and the reduction time is 2-6 hours.

9. Use of the heterogeneous catalyst according to any one of claims 1 to 3 in the preparation of methyl formate by CO esterification.

10. The use according to claim 9, characterized in that: The raw material gas containing methyl nitrite, carbon monoxide, hydrogen and nitrogen is contacted with a heterogeneous catalyst to react to obtain methyl formate; The volume content of methyl nitrite is 5-30%, the volume content of carbon monoxide is 5-60%, the volume content of hydrogen is 5-20%, and the volume content of nitrogen is 5-75%; Airspeed 500-5000h -1 , temperature is 50-200℃, pressure is 0.01-5MPa.

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