Boron-doped heterogeneous catalyst for preparing methyl formate through CO esterification as well as preparation method and application of boron-doped heterogeneous catalyst

Abstract

The invention discloses a boron-doped heterogeneous catalyst for preparing methyl formate through CO esterification as well as a preparation method and application of the boron-doped heterogeneous catalyst, and belongs to the field of synthesis of methyl formate. The boron-doped heterogeneous catalyst comprises a palladium active component, an auxiliary agent and a carrier, the auxiliary agent is boron; 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 assistant boron is 0.001-10% of the mass of the carrier. Compared with a catalyst auxiliary agent reported in the literature, the boron auxiliary agent disclosed by the invention can be used for effectively reducing the dosage of the noble metal and the production cost of the catalyst and remarkably improving the economical efficiency of the technology by adjusting the acid-base property of the carrier and improving the dispersity and the utilization rate of the noble metal. 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 boron-doped multiphase catalyst for preparing methyl formate by CO esterification and 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 and an important chemical intermediate with a wide range of uses. In the chemical industry, it can be hydrolyzed to produce formic acid, and ammonolyzed to produce formamide and dimethylformamide. In the agricultural field, it can be used as a fumigant and fungicide for tobacco and grain. In the pharmaceutical field, it is a synthetic raw material for many drugs. At the same time, methyl formate is also a new type of fluorine-free foaming agent.

[0003] There are many methods for producing methyl formate, such as liquid-phase methanol carbonylation and direct synthesis gas synthesis. However, the main technology currently used in the domestic industry is liquid-phase methanol carbonylation. 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 high raw material purification costs; (2) the liquid-phase methanol carbonylation method uses a homogeneous catalytic system, and it is difficult to separate the product methyl formate from the catalyst; (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 the direct synthesis of methyl formate from synthesis gas and its preparation method, which uses a fixed bed reactor, and the raw materials are carbon monoxide, 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 space-time yield are all high. However, the palladium-based catalysts reported for the preparation of methyl formate by CO esterification have a high content of precious metals, and the cost of precious metals accounts for more than 80% of the total catalyst cost, resulting in a high total cost of catalyst production, and compared with the liquid phase methanol carbonylation method, it is at a disadvantage in terms of catalyst cost. 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 precious metal loading, excellent activity and selectivity, which is of great significance for the practical application of this technology. Summary of the invention

[0005] In view of the fact that 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, the present invention provides a supported palladium-based nanocatalyst with low precious metal loading, high activity and high selectivity, and a preparation method and application thereof.

[0006] According to the first aspect of the present application, a boron-doped multiphase catalyst for preparing methyl formate by CO esterification is provided. Boron (B) as a catalyst additive can effectively improve the dispersion and utilization rate of precious metals by adjusting the acidity of the carrier, effectively reduce the amount of precious metals and the production cost of the catalyst, and significantly improve the economic efficiency of the technology.

[0007] A boron-doped heterogeneous catalyst for preparing methyl formate by CO esterification, the boron-doped heterogeneous catalyst comprising a palladium active component, an auxiliary agent and a carrier;

[0008] The auxiliary agent is selected from boron;

[0009] The loading amount of the palladium active component is 0.01-0.6% of the carrier mass;

[0010] The loading amount of the auxiliary agent boron is 0.001-10% of the carrier mass.

[0011] Optionally, the loading amount of the palladium active component is 0.1-0.5% of the carrier mass;

[0012] The loading amount of the auxiliary agent boron is 0.002-5% of the carrier mass.

[0013] Optionally, the loading amount of the palladium active component is 0.2-0.5% of the carrier mass;

[0014] The loading amount of the auxiliary agent boron is 0.01-0.5% of the carrier mass.

[0015] Optionally, the support is selected from alumina.

[0016] According to the second aspect of the present application, a method for preparing the boron-doped heterogeneous 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 precious metal loading of the catalyst, but also has excellent catalytic performance, a simple preparation process, and is easy to scale up.

[0017] The method for preparing the boron-doped heterogeneous catalyst described above comprises the following steps:

[0018] S1, immersing the carrier in a solution containing a boron auxiliary agent precursor, stirring evenly, heating to volatilize the solvent, drying, and calcining to obtain a boron-modified carrier;

[0019] S2, immersing the boron-modified support in a solution containing a palladium precursor, stirring evenly, heating to volatilize the solvent, drying, and calcining to obtain an intermediate product I;

[0020] S3, 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;

[0021] S4. Reducing the intermediate product II under a hydrogen atmosphere to obtain the boron-doped heterogeneous catalyst.

[0022] Optionally, in step S1, the boron auxiliary agent precursor is selected from at least one of boric acid, boric oxide, sodium pentaborate, and boric acid esters.

[0023] Optionally, in step S2, the palladium precursor is selected from at least one of nitrates, halides, acetylacetonates and acetates corresponding to palladium.

[0024] Optionally, the palladium precursor is selected from potassium chloropalladate.

[0025] Optionally, in step S3, 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;

[0026] 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;

[0027] 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.

[0028] Optionally, in step S3, the reaction conditions are: the reaction temperature is 30-130° C., and the reaction time is 1-10 hours.

[0029] Optionally, in step S4, the reduction conditions are: the reduction temperature is 50-400° C., and the reduction time is 2-6 hours.

[0030] As a specific embodiment, the method for preparing the heterogeneous catalyst described above comprises the following steps:

[0031] 1. Immerse the carrier in a water, methanol or ethanol solution containing an additive precursor (any one of boric acid, boron oxide, sodium pentaborate and boric ester or a combination of any of several compounds), stir evenly, and evenly disperse the carrier in the precursor solution containing the additive precursor;

[0032] 2. Rotate and evaporate the mixed solution containing the auxiliary agent precursor and the carrier obtained in step 1 under heating conditions until the solvent of the solution evaporates, so that the auxiliary agent precursor is uniformly adsorbed on the surface of the carrier;

[0033] 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;

[0034] 4. Immerse the carrier obtained in step 3 into water, acetone, methanol or ethanol solution containing a palladium precursor (any one of nitrates, halides, acetylacetonates, acetates corresponding to palladium or a combination of any of several compounds), and stir evenly to evenly disperse the carrier in the palladium precursor solution;

[0035] 5. Rotate and evaporate the mixed solution of the palladium precursor and the carrier obtained in step 4 under heating conditions until the solvent of the solution evaporates, so that the palladium precursor is uniformly adsorbed on the surface of the carrier;

[0036] 6. The adsorption sample obtained in step 5 is vacuum dried at 40-200° C. for 0.5-10 hours, and then calcined at 200-600° C. for 1-10 hours;

[0037] 7. Add a reducing agent (one or a combination of any several compounds selected from the group consisting of 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 several compounds selected from the group consisting of 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 several compounds selected from the group consisting of polyvinyl pyrrolidone, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer) to the sample obtained in step 6 to undergo a reduction reaction at 30-130° C.;

[0038] 8. Filter and wash the sample obtained in step 7, and dry it in a vacuum drying oven for 1-10 hours;

[0039] 9. The sample obtained in step 8 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.

[0040] According to a third aspect of the present application, there is provided a use of the boron-doped heterogeneous catalyst for preparing methyl formate by CO esterification as described above in preparing methyl formate by CO esterification.

[0041] The application of the boron-doped heterogeneous catalyst described above in the esterification of CO to produce methyl formate.

[0042] Optionally, a raw material gas containing methyl nitrite, carbon monoxide, hydrogen and nitrogen is contacted with a boron-doped heterogeneous catalyst to obtain methyl formate;

[0043] 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%;

[0044] Airspeed 500-5000h -1, temperature is 50-200℃, pressure is 0.01-5MPa.

[0045] The beneficial effects of this application include:

[0046] The boron-doped multiphase catalyst for preparing methyl formate by CO esterification provided in the present application, with boron as a catalyst adjuvant, can improve the dispersion and utilization rate of precious metals by regulating the acidity of the carrier, effectively reduce the amount of precious metals and the production cost of the catalyst, and significantly improve the economy of the technology. The preparation method adopted by the present invention has a simple process, is easy to achieve large-scale amplification, and has excellent catalyst performance, and 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 The Pd / (B-Al 2 O 3 ) catalyst and the Pd / Al prepared in Comparative Example 1 2 O 3 Pyridine infrared absorption spectrum of the catalyst. DETAILED DESCRIPTION

[0048] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0049] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0050] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0051] The infrared absorption spectrum of pyridine was obtained by using a TENSOR II Fourier transform infrared spectrometer produced by Bruker, with 64 scans and a resolution of 4 cm -1 , measuring range 600-4000cm -1 Test conditions: Use a small amount of powder sample and KBr to press into a 15 mm sample piece, place it in the in-situ cell and seal it, and evacuate to 10 -3 Pa, then heat to 400℃ and keep for 2h to remove moisture and gas molecules on the sample surface, and collect background after cooling to room temperature. Pyridine gas is introduced into the in-situ cell, and after adsorption saturation for 1h, the pyridine infrared spectrum of pyridine adsorption is recorded; after heating to 200℃ and keeping for 30min, the pyridine infrared desorption spectrum is recorded, and after heating to 350℃ and keeping for 30min, the desorption spectrum at this time is recorded. The obtained pyridine infrared spectrum can be used to identify the acid type on the surface of the sample.

[0052] In the examples of the present application, the selectivity and space-time yield are calculated as follows:

[0053] 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:

[0054]

[0055]

[0056] 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.

[0057] Example 1

[0058] Weigh 50g of aluminum oxide and immerse it in 100mL of 10.2mol / L boric acid aqueous solution for ultrasonic dispersion for 1 hour, rotate and stir for 1 hour, then rotary evaporate at 110°C for 1 hour, and roast at 600°C for 2 hours. Then, immerse it in 62.5mL of 37.6mmol / L potassium chloropalladate aqueous solution, ultrasonically disperse it for 1 hour, rotate and stir for 2 hours, then rotary evaporate at 120°C for 1 hour, roast at 500°C for 4 hours, then add 1g of ascorbic acid, 3g of sodium citrate, 2g of polyvinyl pyrrolidone, and 50ml of water, react at 90°C for 1 hour, wash, vacuum dry at 80°C for 10 hours, and then reduce it again at 400°C in pure hydrogen atmosphere for 2 hours to obtain Pd / (B-Al2O3) used in CO esterification to methyl formate. 2 O 3 ) catalyst, the loading amount of Pd is 0.43% of the carrier mass, and the loading amount of additive B is 0.03% of the carrier mass.

[0059] Example 2

[0060] The operation is the same as in Example 1, except that the volume of the potassium chloropalladate aqueous solution used is 37.6 ml, and the Pd / (B-Al) solution used in the CO esterification reaction to produce methyl formate is obtained. 2 O 3 ) catalyst, the loading amount of Pd is 0.28% of the carrier mass, and the loading amount of auxiliary agent B is 0.03% of the carrier mass.

[0061] Comparative Example 1

[0062] 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, then add 1g of ascorbic acid, 3g of sodium citrate, 2g of polyvinyl pyrrolidone, 50ml of water, react at 90℃ for 1 hour, wash, vacuum dry at 80℃ for 10 hours, and then reduce again at 400℃ in pure hydrogen atmosphere for 2 hours to obtain Pd / Al used in CO esterification to methyl formate reaction. 2 O 3 The Pd loading of the catalyst is 0.44% of the support mass.

[0063] Characterization of Catalysts by Pyridine Infrared Absorption Spectroscopy

[0064] The Pd / (B-Al 2 O 3 ) catalyst and the Pd / Al prepared in Comparative Example 1 2 O 3 The catalyst was tested by pyridine infrared, such as Figure 1 It can be seen that the prepared catalysts all contain Lewis acid sites, and the multiphase catalysts prepared by the boron doping method disclosed in the present invention can effectively reduce the Lewis acid content of such catalysts.

[0065] Application Examples

[0066] The catalysts of the embodiment and the comparative example were applied to the CO esterification reaction to produce methyl formate. The raw gas ratio was methyl nitrite: carbon monoxide: hydrogen: nitrogen = 25: 20: 10: 45 (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.

[0067] Table 1 Catalyst performance in the CO synthesis of methyl formate reaction

[0068]

[0069] It can be analyzed from Table 1 that the Pd / (B-Al 2 O 3 ) catalyst, which and the Pd / Al 2 O 3 The Pd loading of the catalyst is similar, but its CO conversion rate and space-time yield are significantly higher, indicating that the introduction of the auxiliary agent boron can significantly improve the utilization rate of precious metal palladium, CO conversion rate and space-time yield while keeping the precious metal loading unchanged. 2O 3 ) catalyst, the loading amount of the noble metal palladium is significantly lower than that of the Pd / Al in Comparative Example 1 2 O 3 The palladium loading of the catalyst is increased, but its methyl formate selectivity can still be maintained unchanged, and the CO conversion rate and space-time yield are still slightly higher than those of the comparative catalyst without boron doping. This further illustrates that the introduction of the auxiliary boron can not only obtain methyl formate with high conversion rate and high selectivity, but also can significantly reduce the precious metal content of the catalyst by more than 35%.

[0070] 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 boron-doped heterogeneous catalyst for preparing methyl formate by CO esterification, characterized in that: The boron-doped heterogeneous catalyst comprises a palladium active component, a promoter and a carrier; The auxiliary agent is selected from boron; The loading amount of the palladium active component is 0.01-0.6% of the carrier mass; The loading amount of the auxiliary agent boron is 0.001-10% of the carrier mass.

2. The boron-doped multiphase catalyst according to claim 1, characterized in that: The loading amount of the palladium active component is 0.1-0.5% of the carrier mass; The loading amount of the auxiliary agent boron is 0.002-5% of the carrier mass.

3. The boron-doped multiphase catalyst according to claim 1, characterized in that: The support is selected from alumina.

4. The method for preparing a boron-doped heterogeneous catalyst according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, immersing the carrier in a solution containing a boron auxiliary agent precursor, stirring evenly, heating to volatilize the solvent, drying, and calcining to obtain a boron-modified carrier; S2, immersing the boron-modified support in a solution containing a palladium precursor, stirring evenly, heating to volatilize the solvent, drying, and calcining to obtain an intermediate product I; S3, 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; S4. Reducing the intermediate product II under a hydrogen atmosphere to obtain the boron-doped heterogeneous catalyst.

5. The preparation method according to claim 4, characterized in that In step S1, the boron auxiliary agent precursor is selected from at least one of boric acid, boric oxide, sodium pentaborate, and boric acid esters.

6. The preparation method according to claim 4, characterized in that In step S2, the palladium precursor is selected from at least one of nitrate, halide, acetylacetonate, and acetate corresponding to palladium; Preferably, in step S3, 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 S3, 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 S4, the reduction conditions are: the reduction temperature is 50-400° C., and the reduction time is 2-6 hours.

9. Use of the boron-doped 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 boron-doped heterogeneous catalyst 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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