Preparation method of tungsten carbide catalyst and application thereof in co-production of methyl formate and methyl acetate

Abstract

The application discloses a preparation method of a tungsten carbide catalyst and application of the tungsten carbide catalyst in co-production of methyl formate and methyl acetate. The tungsten carbide catalyst comprises a carrier of silicon dioxide and an active component of tungsten carbide supported on the silicon dioxide. The tungsten carbide catalyst is prepared by adopting an impregnation method and by precisely controlling the loading amount of the tungsten carbide on the carrier. The obtained catalyst can realize effective regulation on product distribution by optimizing the reaction conditions of dimethyl oxalate hydrogenation, so as to generate methyl formate and methyl acetate with high selectivity. The method not only improves the conversion rate of raw materials and the selectivity of target products, but also provides a new efficient catalyst solution method for co-production of methyl formate and methyl acetate.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of a tungsten carbide catalyst and application of the tungsten carbide catalyst in co-production of methyl formate and methyl acetate, and relates to the technical field of coal chemical catalysts. BACKGROUND

[0002] Methyl formate can be widely applied to the fields of chemical industry, medicine, agriculture and refrigeration due to its unique molecular structure, chemical properties of aldehyde and ester, and the ability to undergo oxidation reaction, reduction reaction, hydrolysis reaction and the like. In particular, methyl formate is one of methanol series products, and can produce chemical products such as formic acid, formamide, dimethyl carbonate and ethylene glycol.

[0003] Methyl acetate is a colorless and fragrant volatile liquid, is miscible with ethanol, soluble in methyl alcohol and diethyl ether, is easy to hydrolyze, and can be hydrolyzed in moist air. Methyl acetate is an important organic synthesis intermediate, has a wide range of uses, can be directly used as a smoke fumigant and a bactericide for treating tobacco, dry fruits and grains, is often used as a solvent for nitrocellulose and cellulose acetate, and is often used as a synthesis raw material for drugs such as sulfamethoxypyrimidine, sulfamethoxazole and the cough suppressant methoxyphenamine.

[0004] From the prior art, in the dimethyl oxalate hydrogenation catalyst, most of the catalysts use Cu, Ag, Ni and the like, the product is mainly ethylene glycol or methyl glycolate, and the selectivity of methyl formate or methyl acetate is low. SUMMARY

[0005] In view of the above technical problems, the application aims to provide a preparation method of a tungsten carbide catalyst and application of the tungsten carbide catalyst in co-production of methyl formate and methyl acetate. The catalyst preparation method is simple, the activity component ratio of the dimethyl oxalate hydrogenation catalyst is adjusted to control the ratio of methyl formate and methyl acetate in the dimethyl oxalate hydrogenation reaction product, the co-production of methyl formate and methyl acetate can be realized, and the application has a good application prospect.

[0006] To solve the problems in the prior art, the technical scheme adopted by the application is as follows:

[0007] The application discloses a preparation method of a tungsten carbide catalyst, and application of the tungsten carbide catalyst in co-production of methyl formate and methyl acetate.

[0008] As an improvement, the concentration of the ammonia water is 20 wt.%.

[0009] As an improvement, the calcination temperature is 620-680 DEG C, and the calcination time is 2-4 h.

[0010] As an improvement, the flow rate of the argon gas in the calcination process is 100 ml / min, the calcination temperature is 650 DEG C, the temperature rising speed is 10 DEG C / min, and the holding time is 3 h.

[0011] As an improvement, the silica is obtained by calcination of tetraethyl orthosilicate.

[0012] The tungsten carbide catalyst prepared by the preparation method is applied to co-production of methyl formate and methyl acetate.

[0013] As an improvement, the application comprises the following steps: the tungsten carbide catalyst is used in fixed-bed oxalic acid dimethyl ester hydrogenation synthesis, the reaction temperature is 160-260 DEG C, the reaction pressure is 0.1-2 MPa, the mass space velocity of the oxalic acid dimethyl ester is 0.1-0.5 h -1 , and the hydrogen ester ratio is 5-200:1.

[0014] As an improvement, by controlling the content ratio of the active component in the tungsten carbide catalyst to be within 0.20-0.30, the selectivity of the methyl formate generated from the oxalic acid dimethyl ester as a reaction product is more than 58%, and the selectivity of the methyl acetate is more than 34%.

[0015] Advantages:

[0016] Compared with the prior art, the preparation method of the tungsten carbide catalyst and the application of the tungsten carbide catalyst in co-production of methyl formate and methyl acetate have the following advantages.

[0017] 1. Good application prospect: the methyl formate and the methyl acetate are both important chemical raw materials and have wide application. The catalyst provided by the application is not only suitable for co-production of the methyl formate and the methyl acetate, but also can optimize the proportion of the products by adjusting the reaction conditions, so that the needs of different fields can be met.

[0018] 2. High selectivity: By precisely regulating the loading amount of tungsten carbide on the carrier, and combining with the optimization of the reaction conditions of dimethyl oxalate hydrogenation, the effective regulation of the product distribution is realized, and methyl formate and methyl acetate are generated with high selectivity. Actual detection shows that when the tungsten carbide catalyst of the application is used for producing dimethyl oxalate, the selectivity of methyl formate can reach more than 58%, and the selectivity of methyl acetate can reach more than 34%.

[0019] 3. High efficiency preparation: The tungsten carbide catalyst with high efficiency can be prepared by conventional steps such as impregnation, drying and calcination, and the preparation method is simple, the steps are clear, and easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 XDR characterization chart of tungsten carbide catalyst prepared for examples 1-3;

[0021] Figure 2 N2 adsorption and desorption characterization chart of tungsten carbide catalyst prepared for examples 1-3;

[0022] Figure 3 Selectivity of methyl formate and methyl acetate produced by tungsten carbide catalyst prepared for examples 1-3;

[0023] Figure 4 Performance chart of tungsten carbide catalyst prepared for example 2 under different dimethyl oxalate flow rates;

[0024] Figure 5 Performance chart of tungsten carbide catalyst prepared for example 2 under different hydrogen ester ratios;

[0025] Among them, Figures 1-3 MF is methyl formate, MA is methyl acetate, and DMO is dimethyl oxalate. DETAILED DESCRIPTION

[0026] The application will be further explained in conjunction with the examples and drawings. The following examples are only used to illustrate the application, but not to limit the scope of the application.

[0027] Example 1

[0028] 0.3161 g phosphotungstic acid and 0.2308 g hexamethylenetetramine were dissolved in 10 ml of ammonia water at 25°C, and the mixture was stirred. Ultrasonic treatment was performed at room temperature for 5 min, then 1 g was added, and ultrasonic treatment was performed at room temperature for 25 min, followed by immersion for 24 h. After immersion, calcination was performed in a muffle furnace at 100°C for 24 h, and then the tube furnace was purged with argon at 100 mL / min, and the temperature was increased to 650°C at a rate of 10°C / min and maintained for 3 h. The silica was prepared using tetraethyl orthosilicate according to the method disclosed in the article "Size-controllable synthesis of dendritic porous silica as reinforcing fillers for dental composites".

[0029] Example 2

[0030] Except that 0.3161 g phosphotungstic acid and 0.2308 g hexamethylenetetramine were replaced by 0.4215 g phosphotungstic acid and 0.3077 g hexamethylenetetramine, the rest was the same as in Example 1.

[0031] Example 3

[0032] Except that 0.3161 g phosphotungstic acid and 0.2308 g hexamethylenetetramine were replaced by 0.5419 g phosphotungstic acid and 0.3957 g hexamethylenetetramine, the rest was the same as in Example 1.

[0033] The catalysts prepared in Examples 1-3 were structurally characterized and their performance was tested, and the results are shown in Figures 1-5 and Table 1.

[0034] Figure 1 The characterization graphs of the catalysts prepared in Examples 1-3 are shown in the figure. As can be seen from the figure, the metal W in the catalyst prepared in the application exists in the form of tungsten carbide and tungsten oxide.

[0035] Figure 2 The N2 adsorption and desorption characterization graphs of the catalysts prepared in Examples 1-3 are shown in the figure. As can be seen from the figure, as the tungsten loading of the catalysts in the application decreases, the adsorption area also increases.

[0036] Table 1 Performance of catalysts at different tungsten carbide contents

[0037]

[0038] The catalysts prepared in Examples 1-3 were taken for application testing. The specific steps were as follows: 0.8 g of the above catalyst was loaded into a fixed bed reactor, quartz wool was filled on the upper and lower sides of the reaction tube, a 13% oxalic acid dimethyl ester (DMO) methanol solution was introduced, the reaction pressure was 2 MPa, the DMO liquid space velocity was 0.1 h-1 The catalysts prepared in Examples 1-3 were tested and calculated by using a gas chromatograph, and the results are shown in Figure 3 Figure 1. In Example 1, the conversion rate of dimethyl oxalate was 43%, the selectivity of methyl formate was 64%, and the selectivity of methyl acetate was 35%. In Example 2, the conversion rate of dimethyl oxalate was 54%, the selectivity of methyl formate was 58%, and the selectivity of methyl acetate was 37%. In Example 3, the conversion rate of dimethyl oxalate was 42%, the selectivity of methyl formate was 64%, and the selectivity of methyl acetate was 34%. As can be seen from the figure, in Examples 1-3, the conversion rate of dimethyl oxalate was above 42%, the selectivity of methyl formate was above 58%, and the selectivity of methyl acetate was above 34%.

[0039] The catalyst prepared in Example 2 was used to test the performance change under different dimethyl oxalate flow rates according to the above test method, and the results are shown in Figure 4 Figure 2. As can be seen from the figure, under the conditions of a reaction pressure of 2 MPa, a temperature of 260°C, and a molar ratio of H2 / DMO of 200:1, the conversion rate of dimethyl oxalate decreased with the increase of the dimethyl oxalate space velocity, the maximum conversion rate of dimethyl oxalate was 78% when the dimethyl oxalate space velocity was 0.05 h -1 , the maximum selectivity of methyl formate was 64% when the dimethyl oxalate space velocity was 0.05 h -1 , and the maximum selectivity of methyl acetate was 38% when the dimethyl oxalate space velocity was 0.15 h -1 .

[0040] The catalyst prepared in Example 2 was used to test the performance change under different dimethyl oxalate flow rates according to the above test method, and the results are shown in Figure 5 Figure 3. As can be seen from the figure, under the conditions of a reaction pressure of 2 MPa, a temperature of 260°C, and a dimethyl oxalate space velocity of 0.1 h -1 , the maximum conversion rate of dimethyl oxalate was 54% when the hydrogen / ester ratio was 200:1, the maximum selectivity of methyl formate was 58% when the hydrogen / ester ratio was 200:1, and the maximum selectivity of methyl acetate was 43% when the hydrogen / ester ratio was 160:1.

[0041] Combining Figures 3-5 , it can be concluded that the optimal process parameters for the catalyst with a tungsten carbide loading of 25% are a reaction pressure of 2 MPa, a temperature of 260°C, a dimethyl oxalate space velocity of 0.1 h -1 , and a hydrogen / ester ratio of 200:1.

[0042] To sum up, the application adopts the impregnation method, and is prepared by accurately regulating the loading amount of tungsten carbide on the carrier. The obtained catalyst can realize effective regulation of product distribution by optimizing the reaction conditions of dimethyl oxalate hydrogenation, so as to generate methyl formate and methyl acetate with high selectivity. The method not only improves the yield and selectivity of the target product, but also provides a new efficient catalyst solution for the co-production of methyl formate and methyl acetate

[0043] The above description of the application and its embodiments is illustrative, and is not restrictive, and the embodiments shown in the drawings are only one of the embodiments of the application, and the actual structure is not limited thereto. Therefore, if a person skilled in the art is inspired by it, without departing from the purpose of the application, similar structure and embodiments can be designed without creativity, which should belong to the protection scope of the application.

Claims

1. The application of a tungsten carbide catalyst in the hydrogenation reaction of dimethyl oxalate, characterized in that, The application involves controlling the content ratio of the active component in the tungsten carbide catalyst within the range of 0.20-0.30, using dimethyl oxalate as a reactant, achieving a selectivity of over 58% for methyl formate and over 34% for methyl acetate. Specifically, the catalyst is prepared as follows: at 20-30 °C, phosphotungstic acid and hexamethylenetetramine are weighed at a mass ratio of 1.3-1.4:1, dissolved in ammonia water, stirred, and ultrasonically treated for 5-10 min. Then, silica is added according to the required tungsten carbide loading, and ultrasonic treatment continues for 20-30 min, followed by impregnation for 18-24 h. After impregnation, the catalyst is dried in a muffle furnace at 100 °C for 12-24 h, then transferred to a tube furnace and calcined under an argon atmosphere to obtain the tungsten carbide catalyst. The tungsten carbide catalyst comprises silica as a support and tungsten carbide as an active component supported on silica.

2. The application according to claim 1, characterized in that, The concentration of ammonia water is 20 wt.%.

3. The application according to claim 1, characterized in that, The calcination temperature is 620-680 ℃, and the calcination time is 2-4 h.

4. The application according to claim 3, characterized in that, During the calcination process, the argon gas flow rate was 100 mL / min, the calcination temperature was 650℃, the heating rate was 10℃ / min, and the temperature was maintained for 3 h.

5. The application according to claim 1, characterized in that, The silicon dioxide is obtained by calcining tetraethyl orthosilicate.

6. The application according to claim 1, characterized in that, The application includes the following steps: using a tungsten carbide catalyst in the hydrogenation reaction of dimethyl oxalate, with a reaction temperature of 160-260 °C, a reaction pressure of 0.1-2 MPa, and a mass hourly space velocity (WHSV) of dimethyl oxalate of 0.1-0.5 h⁻¹. -1 The molar ratio of hydrogen ester is 5-200:1.

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