CN107199035A - A kind of normal pressure gas phase catalytic synthesis methyl formate catalyst and preparation method thereof - Google Patents

Abstract

The invention discloses a catalyst for synthesizing methyl formate by atmospheric gas phase catalysis and a preparation method thereof. The preparation method of the catalyst is: adding tetraethyl orthosilicate, zinc nitrate, the precursor of the active component palladium, polyvinylpyrrolidone, and ethanol into the acetic acid solution, stirring and dissolving, and then reducing the catalyst by a rotary evaporator. The transparent sol is obtained by pressure distillation, the sol is dried and calcined to obtain the precursor of the catalyst, and the precursor is reduced by hydrogen or carbon monoxide to obtain the catalyst Pd/(SiO ₂ +ZnO). The catalyst uses palladium as an active component and SiO ₂ +ZnO composite oxide as a carrier. The catalyst of the invention exhibits better catalytic activity and methyl formate selectivity in the normal pressure gas phase synthesis reaction of methyl formate. The preparation method adopted in the present invention can effectively improve the dispersion degree of the noble metal palladium in the carrier through the sol-gel method, significantly improve the catalytic efficiency of the catalytic reaction, and realize the efficient utilization of the noble metal palladium.

Description

Catalyst for synthesizing methyl formate by atmospheric gas phase catalysis and preparation method thereof

technical field

The invention provides a catalyst for catalytically synthesizing methyl formate in an atmospheric pressure gas phase and a sol-gel preparation method thereof, which belong to the technical field of methyl formate preparation.

Background technique

Methyl formate is an important C1 chemical intermediate with a wide range of uses. In the chemical industry, it can be used as a raw material for organic synthesis products and as a solvent in the manufacture of cellulose acetate. In agriculture, it can be used as insecticide, cereal crop fungicide, fumigant and tobacco treatment agent, etc. In medicine, it is often used as a raw material for the synthesis of sulfomethylpyrimidine, sulfomethoxypyrimidine, and the antitussive agent methorphan.

There are many methods for the preparation of methyl formate, the common ones are: formic acid methanol esterification method, methanol gas phase catalytic dehydrogenation method, formaldehyde catalytic dimerization method, methanol oxidative dehydrogenation method, synthesis gas direct synthesis method, methanol liquid phase carbonylation method, etc. . So far, the technologies that have been industrialized include formic acid methanol esterification, liquid phase methanol carbonylation and methanol gas phase catalytic dehydrogenation. Among them, the methyl formic acid esterification method has been gradually eliminated due to its backward technology, high energy consumption and serious equipment corrosion. The liquid-phase methanol carbonylation method is currently the main method for producing methyl formate abroad. Its advantage is that the purity of the carbon monoxide feed gas is not high and the selectivity of the product methyl formate is high. However, this method also has serious disadvantages: sodium methoxide is The only catalyst requires anhydrous conditions; the reaction needs to be carried out in a reactor, and the pressure requirement is high; the separation of the product and the catalyst is troublesome; the process cannot produce methyl formate continuously. Gas-phase catalytic dehydrogenation of methanol has not yet been widely applied due to its immature technology.

my country is a country rich in coal resources, so the development of coal chemical technology to synthesize methyl formate is more in line with my country's current basic national conditions. Patent 201410141259.8 reports a catalyst for the formylation of methyl nitrite to methyl formate and its preparation method. The raw materials used in this process are synthesis gas and methyl nitrite. This process is a fixed bed atmospheric pressure gas phase catalytic reaction, which can realize In the continuous production of methyl formate, the product is mainly methyl formate, and the by-products are mainly dimethyl carbonate, dimethyl oxalate and methanol. The selectivity of the product methyl formate is relatively high, and the separation of the product methyl formate is also relatively easy. This process has very good application prospects. In view of the defects of the existing methyl formate production process and the serious shortage of domestic production capacity of methyl formate, it is necessary to develop a new catalyst with high activity and high selectivity for the formylation of methyl nitrite to synthesize methyl formate reaction.

Contents of the invention

Aiming at the defects existing in the existing methyl formate production process, the invention provides a catalyst which can be used for atmospheric gas phase catalytic synthesis of methyl formate and a sol-gel preparation method thereof.

Catalyst Pd/(SiO ₂ +ZnO) provided by the present invention: a catalyst with Pd as the active component and SiO ₂ +ZnO composite oxide as the carrier, wherein the loading of Pd is 0.05-0.5% of the mass of the carrier, and SiO ₂ The molar ratio of the two oxides in the +ZnO composite oxide is 1:1˜4:1. The specific surface area of the catalyst is 50-80m ² /g, and the average pore diameter is 12-25nm.

Its concrete preparation steps are as follows:

A. Dissolving tetraethyl orthosilicate in the acetic acid solution with a concentration of 5 to 10 mol/L to prepare an acetic acid solution of tetraethyl orthosilicate with a concentration of 0.67 to 1 mol/L, referred to as solution A;

B. The precursor of zinc nitrate, ethanol, Pd, polyvinylpyrrolidone (PVP) is added in the solution A successively to obtain solution B; Wherein the molar ratio of zinc nitrate and tetraethyl orthosilicate is 1～4:1; Ethanol The addition amount of PVP is 0.25-0.4 of the volume of solution A; the addition amount of Pd precursor is based on the Pd loading in the final prepared catalyst as 0.05-0.5% of the carrier mass, and the addition amount of PVP is based on the Pd precursor mass 5 to 10 times of added;

The precursor of the Pd is any one of palladium nitrate, palladium acetate, tetraammine palladium nitrate;

C. Stir solution B continuously at room temperature for 2 to 6 hours, and then use a rotary evaporator to carry out vacuum distillation. After the solution is evaporated, a transparent sol is obtained, and the obtained sol is dried in an oven at 80 to 120°C for 12 to 24 hours. After calcination at 400-600°C for 2-6 hours in a furnace, the catalyst precursor is obtained;

D. Reducing the catalyst precursor obtained in step C under hydrogen or carbon monoxide atmosphere at 150-250°C for 2-6 hours to obtain a catalyst, expressed as Pd/(SiO ₂ +ZnO).

The catalyst prepared by the sol-gel method provided by the invention shows better catalytic activity in the reaction of formylation of methyl nitrite to methyl formate, and the reaction conditions are mild, without obvious exothermic phenomenon, and the product methyl formate Has a high selectivity.

The preparation method of the invention has the advantages that: the sol-gel method is used to prepare the catalyst, which can increase the dispersion degree of the active component Pd on the carrier and reduce the Pd load of the noble metal. In addition, by changing the amount of PVP added during the preparation process, not only the specific surface area and average pore size of the catalyst can be effectively adjusted, but also the average dispersed particle size of the active component Pd particles can be effectively reduced.

Description of drawings

The powder diffraction pattern of the catalyst sample that Fig. 1 embodiment 1 obtains

detailed description

The catalyst prepared by the sol-gel method of the present invention will be described in detail below in conjunction with specific examples, but the present invention is not limited to the following specific examples.

Example 1

Dissolve 0.04mol of tetraethyl orthosilicate in 60mL of 6mol/L acetic acid solution, then add 0.04mol of zinc nitrate, 20mL of ethanol, 0.012g of palladium nitrate and 0.06g of PVP in sequence, keep stirring at room temperature for 2 hours, and dissolve them Transfer to a round-bottomed flask and use a rotary evaporator for vacuum distillation. After the solution evaporates, a transparent sol is obtained. The sol is dried in an oven at 100°C for 12 hours, and roasted in a muffle furnace at 450°C for 4 hours. The desired catalyst sample was obtained after reduction under a hydrogen atmosphere at °C for 2 hours, wherein the loading amount of the active component Pd was 0.1% of the weight of the carrier.

The phase structure analysis of the catalyst sample obtained in Example 1 was carried out by powder diffraction, and the results are shown in FIG. 1 . As can be seen from Fig. 1, only _SiO2 and the diffraction peak of ZnO phase appear in the powder diffraction pattern, do not appear any diffraction peak of PdO, this illustrates that the carrier of gained catalyst sample is _SiO2 and the mixed phase of ZnO, and active component palladium is due to Due to its high dispersion or low loading, the diffraction peaks of PdO cannot be detected by powder diffraction characterization. The results of testing the catalyst components by inductive plasma coupling showed that the mass fraction of SiO ₂ in the catalyst was 42.37%, and the mass fraction of ZnO was 57.28%.

Example 2

Dissolve 0.04mol of tetraethyl orthosilicate in 40mL of 6mol/L acetic acid solution, then add 0.06mol of zinc nitrate, 20mL of ethanol, 0.031g of palladium acetate and 0.31g of PVP in sequence, keep stirring at room temperature for 4 hours, and dissolve them Transfer to a round-bottom flask and use a rotary evaporator for vacuum distillation. After the solution evaporates, a transparent sol is obtained. Dry the sol in an oven at 110°C for 12 hours, and roast it in a muffle furnace at 500°C for 2 hours. The required catalyst sample was obtained by reduction under hydrogen atmosphere at °C for 4 hours, wherein the loading amount of the active component Pd was 0.2% of the mass of the carrier. The mass fraction of _SiO2 in the catalyst sample was measured to be 33.08%, and the mass fraction of ZnO was 57.87%.

Example 3

Dissolve 0.04mol tetraethyl orthosilicate in 60mL acetic acid solution with a concentration of 6mol/L, then add 0.05mol zinc nitrate, 20mL ethanol, 0.054g tetraammine palladium nitrate and 0.324g PVP in sequence, and keep stirring at room temperature for 6h Then transfer it to a round-bottomed flask and use a rotary evaporator for vacuum distillation. After the solution evaporates, a transparent sol is obtained. Dry the sol in an oven at 80°C for 12 hours, and roast the solid in a muffle furnace at 600°C for 4 hours. The desired catalyst sample was obtained by reducing the substance under a carbon monoxide atmosphere at 200° C. for 2 hours, wherein the loading amount of the active component Pd was 0.3% of the weight of the carrier. The inductive plasma coupling test showed that the mass fraction of _SiO2 in this catalyst sample was 37.05%, and the mass fraction of ZnO was 62.61%.

Example 4

Dissolve 0.04mol of tetraethyl orthosilicate in 60mL of acetic acid solution with a concentration of 6mol/L, then add 0.05mol of zinc nitrate, 20mL of ethanol, 0.012g of palladium nitrate and 0.12g of PVP in sequence, keep stirring at room temperature for 3 hours, and dissolve them Transfer to a round-bottomed flask and evaporate the liquid to dryness with a rotary evaporator to obtain a transparent gel. Dry the gel in an oven at 120°C for 12 hours, and bake it in a muffle furnace at 600°C for 4 hours. The desired catalyst sample was obtained after reduction for 4 hours, wherein the loading amount of the active component Pd was 0.1% of the weight of the carrier. The inductive plasma coupling test showed that the mass fraction of _SiO2 in this catalyst sample was 37.12%, and the mass fraction of ZnO was 62.58%.

Catalyst Performance Evaluation

The catalyst samples of Examples 1 to 4 were sieved into particles of 10 to 20 meshes, and 2 mL of the catalyst samples of Examples 1 to 4 were measured with a graduated cylinder and filled in a stainless steel reaction tube with an inner diameter of 5 mm, and then 20 mL/min of methyl nitrite was introduced , 20mL/min carbon monoxide, 10mL/min hydrogen, the reaction space velocity is 1500h ^-1 , the heating temperature is controlled at 135°C, the reaction products and tail gas are analyzed by online gas chromatography, and the specific analysis results are listed in Table 1.

The performance evaluation result of table 1 embodiment 1～4 catalyst sample

From the evaluation results in the above table, it can be seen that the catalyst sample prepared by the method of the present invention shows better catalytic activity in the atmospheric pressure gas phase reaction of carbon monoxide, hydrogen and methyl nitrite, and the single-pass conversion rate of carbon monoxide can reach more than 85%. , the selectivity of methyl formate can reach more than 90%, especially in the case of Pd loading of 0.1%, the space-time yield of methyl formate can still reach 710g/L _cat ·h.

Claims (2)

1. a kind of preparation method of normal pressure gas phase catalytic synthesis methyl formate catalyst, its specific preparation process is as follows：

A. tetraethyl orthosilicate is dissolved in concentration in 5~10mol/L acetums, prepare concentration be 0.67~1mol/L just The acetum of tetraethyl orthosilicate, abbreviation solution A；

B. zinc nitrate, ethanol, Pd presoma, polyvinylpyrrolidone are added sequentially in solution A obtain solution B；Wherein The mol ratio of zinc nitrate and tetraethyl orthosilicate is 1~4:1；The addition of ethanol is the 0.25-0.4 of solution A volume；Before Pd The addition for driving body is 0.05~0.5% addition for carrier quality, poly- second according to Pd load capacity in the catalyst finally prepared The addition of alkene pyrrolidone is 5~10 times of additions of forerunner's weight according to Pd；

The presoma of the Pd is any one in palladium nitrate, palladium, the ammino palladium of nitric acid four；

C. solution B is continuously stirred into 2~6h at room temperature, then carries out vacuum distillation with Rotary Evaporators, solution evaporates After obtain vitreosol, by obtained colloidal sol respectively through being dried at 80~120 DEG C of baking oven 400 in 12~24h, Muffle furnace~ After 600 DEG C of 2~6h of roasting, the catalyst precarsor is obtained；

D. catalyst precarsor step C obtained under hydrogen or carbon monoxide atmosphere in 150~250 DEG C of reductase 12~6 hour, Catalyst is obtained, Pd/ (SiO are expressed as₂+ZnO)。

2. a kind of normal pressure gas phase catalytic synthesis methyl formate catalyst prepared according to the method described in claim 1, its table It is shown as Pd/ (SiO₂+ ZnO), wherein Pd is active component, SiO₂+ ZnO composite oxides are carrier, and Pd load capacity is carrier matter 0.05~0.5%, SiO of amount₂The mol ratio of two oxides is 1 in+ZnO composite oxides:1~4:1；The catalyst compares table Area is 50~80m²/ g, average pore size is 12~25nm.