CN1136966C - Catalyst for synthesizing dimethyl carbonate and preparation method thereof - Google Patents

Abstract

The present invention relates to a catalyst for synthesizing dimethyl carbonate, which comprises soluble salts of alkali earth metal, alkali metal compounds and carriers, wherein the weight ratio of the soluble salts of alkali earth metal, the alkali metal compounds and the carriers is 0.01 to 0.3: 0.01 to 0.5: 1. After calcined according to a proportion of 1:1 for 1 to 10 hours, the carriers are immersed in an aqueous solution of the soluble salts of alkali earth metal in equal volume according to the composition of the catalyst, are dried, are calcined and are immersed in the alkali metal compounds in equal volume to obtain the catalyst. The catalyst has the advantages of simple preparation method, easy operation, mild reaction conditions and high yield of target products. The catalyst is easy to separate from products, and can be repeatedly used.

Description

Catalyst for synthesizing dimethyl carbonate and preparation method thereof

Field:

The invention belongs to a catalyst for synthesizing dimethyl carbonate and a preparation method thereof.

Background technique:

Dimethyl carbonate (DMC), as a low-toxicity, environment-friendly product, has been widely used in the fields of preparing high-performance resins, solvents, dye intermediates, pharmaceutical additives, food preservatives, lubricating oil additives, etc. applications and are gaining more and more attention. In recent years, a large number of patents on the production and application of dimethyl carbonate have been published at home and abroad, and a certain scale of industrial production has been achieved. The industrial production methods of dimethyl carbonate mainly include liquid-phase methanol carbonylation, gas-phase methanol carbonylation and transesterification. Among them, the transesterification method has been paid more and more attention because of its mild reaction conditions, simple process flow and low equipment cost. The transesterification method is mainly formed by the reaction of carbon dioxide and ethylene oxide (EO) or propylene oxide (PO) to form ethylene carbonate (EC) or propylene carbonate (PC), and then made from EC or PC and methanol (MeOH). Obtain DMC, simultaneously by-product ethylene glycol (EG) or propylene glycol (PG), concrete reaction formula is as follows: R = H, _CH3

Generally speaking, alkali metal hydroxides, alkali metal carbonates, alkali metal alkoxides, etc. (Jiang Qi et al., Natural Gas Chemical Industry, 1997, 22(5), 1) are often used as catalysts for the second step of transesterification. However, because it is a homogeneous catalytic reaction, it is difficult to separate and reuse the catalyst.

Invention content:

The object of this invention is to provide a kind of solid base catalyst from methyl alcohol and propylene carbonate or ethylene carbonate synthetic dimethyl carbonate, this catalyst has high activity and is easy to separate from product.

The purpose of the present invention is achieved in that the soluble salts of alkaline earth metals and alkali metal compounds are impregnated onto molecular sieves, activated carbon, silicon oxide, zinc oxide or aluminum trioxide in two steps. The weight ratio of catalyst consists of:

Soluble salt of alkaline earth metal: alkali metal compound: carrier=0.01～0.3:0.01～0.5:1

The soluble salts of alkaline earth metals mentioned above are: magnesium nitrate, calcium acetate, calcium nitrate, strontium nitrate and the like.

As mentioned above, the alkali metal compounds include carbonates, nitrates, acetates, fluorides, and hydroxides of sodium, potassium, and cesium.

As mentioned above the support is molecular sieve, activated carbon, silicon oxide, zinc oxide or aluminum trioxide.

The preparation method of catalyst of the present invention is as follows:

Burn the carrier at 300-1000°C for 1-10 hours, then impregnate the equal volume of the carrier into the soluble salt solution of alkaline earth metal according to the above catalyst composition, let it stand at room temperature for 2-30 hours, and then dry it at 60-200°C , baked at 350-800°C for 1-10 hours, then lowered to room temperature, immersed in an equal volume of alkali metal compound aqueous solution according to the above catalyst composition, left at room temperature for 2-30 hours, and then dried at 100-200°C, The catalyst is obtained by burning at 300-900°C for 1-5 hours.

Compared with the prior art, the present invention has the following advantages:

(1) The preparation method is simple and easy to operate.

(2) The catalyst and the product are easy to separate and can be reused.

(3) The reaction conditions are mild and the yield of the target product is high.

Detailed ways:

Example 1:

The alumina was fired at 300°C for 10 hours. Then use 0.01g magnesium nitrate/alumina to impregnate the aluminum oxide in an equal volume of magnesium nitrate aqueous solution, let it stand for 2 hours, dry it at 60°C, burn it at 500°C for 1 hour, then lower it to room temperature, and oxidize it with 0.5g hydroxide Potassium/g alumina, equal volume impregnated in potassium hydroxide aqueous solution, after standing for 2 hours, dried at 100°C, and calcined at 500°C for 2 hours to obtain the catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. The analysis method is: analyze the reaction product with GC-920 produced by Shanghai Haixin Chromatography Co., Ltd. The chromatographic conditions are as follows: chromatographic column: stainless steel column with an outer diameter of 3 mm and a length of 2 m; carrier: GDX-203 (60-80 mesh); detector: thermal conductivity cell; injector temperature: 220 ° C; thermal conductivity cell temperature: 220 ℃; column temperature program temperature rise: initial temperature 100 ℃, time 7 minutes; heating rate 20 ℃ per minute; final temperature 200 ℃, time 20 minutes; injection volume: 1 μL. The results are shown in Table 1.

Example 2:

The ZSM-5 molecular sieve was fired at 500°C for 4 hours. Then impregnate the equal volume of molecular sieves into calcium acetate aqueous solution according to 0.3g calcium acetate/g molecular sieve, after standing for 15 hours, dry at 100°C, burn at 500°C for 5 hours, reduce to room temperature, and press 0.2g potassium carbonate/g Molecular sieves were impregnated in an equal volume of potassium carbonate aqueous solution, allowed to stand for 15 hours, dried at 150°C, and fired at 300°C for 1 hour to obtain a catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the /g supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Example 3:

Activated carbon was fired under N ₂ at 500°C for 4 hours. Then impregnate the activated carbon into the calcium nitrate aqueous solution according to 0.15g calcium nitrate/g activated carbon, after standing for 30 hours, dry at 200°C, burn at 400°C in _N2 for 10 hours, lower the room temperature, press 0.3g nitric acid Potassium/g activated carbon, equal volume impregnated in potassium nitrate aqueous solution, after standing for 30 hours, dried at 200°C, and fired at 700°C in _N2 for 5 hours to obtain the catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Example 4:

The alumina was fired at 1000°C for 1 hour. Then impregnate an equal volume of alumina into calcium acetate aqueous solution according to 0.10g calcium acetate/g alumina, let it stand for 24 hours, dry at 120°C, burn at 800°C for 2 hours, reduce to room temperature, and fluoride with 0.35g Potassium/g alumina, equal volume impregnated in potassium fluoride aqueous solution, after standing for 24 hours, dried at 120°C, and fired at 900°C for 2 hours to obtain the catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Example 5:

The silica was fired at 500°C for 4 hours. Then, according to 0.20g calcium acetate/g silica, impregnate the equal volume of silicon oxide into calcium acetate aqueous solution, let it stand for 24 hours, dry it at 120°C, bake it at 350°C for 2 hours, lower it to room temperature, and oxidize it with 0.01g of hydroxide Cesium/g silicon oxide, equal volume immersed in cesium hydroxide aqueous solution, after standing for 24 hours, dried at 120°C, and fired at 500°C for 2 hours to obtain a catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Embodiment 6:

Zinc oxide was fired at 500°C for 4 hours. Then impregnate the equal volume of zinc oxide into the calcium acetate aqueous solution according to 0.25g calcium acetate/g zinc oxide, after standing for 24 hours, dry at 120°C, burn at 500°C for 2 hours, lower the room temperature, and oxidize with 0.35g hydroxide Sodium/g zinc oxide, equal volume immersed in sodium hydroxide aqueous solution, after standing for 24 hours, dried at 120°C, and fired at 500°C for 2 hours to obtain the catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Embodiment 7:

Zinc oxide was fired at 500°C for 4 hours. Then impregnate the equal volume of alumina into the calcium acetate aqueous solution according to 0.18g calcium acetate/g alumina, let it stand for 24 hours, dry at 120°C, burn at 500°C for 2 hours, reduce to room temperature, press 0.4g cesium nitrate /g alumina, impregnated equal volume in cesium nitrate aqueous solution, allowed to stand for 24 hours, dried at 120°C, and fired at 500°C for 2 hours to obtain a catalyst. Add methanol, propylene carbonate and catalyst into a 75mL autoclave, the molar ratio of propylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analysis method is with embodiment 1.

Embodiment 8:

The alumina was fired at 500°C for 6 hours. Then impregnate an equal volume of aluminum oxide into an aqueous solution of strontium nitrate at the rate of 0.08g strontium nitrate/g alumina, let it stand for 24 hours, dry at 120°C, burn at 500°C for 2 hours, cool down to room temperature, and fluoride at 0.5g Sodium/g alumina, equal volume immersed in sodium fluoride aqueous solution, after standing for 24 hours, dried at 120°C, and fired at 500°C for 2 hours to obtain the catalyst. Add methanol, ethylene carbonate and catalyst into a 75mL autoclave, the molar ratio of ethylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Embodiment 9:

The alumina was fired at 500°C for 4 hours. Then, according to 0.10g calcium acetate/g alumina, the aluminum oxide is impregnated into the calcium acetate aqueous solution in an equal volume, and after standing for 24 hours, it is dried at 120°C, fired at 500°C for 2 hours, lowered to room temperature, and mixed with 0.15g cesium acetate /g alumina, impregnated in an equal volume of cesium acetate aqueous solution, let it stand for 24 hours, dried at 120°C, and fired at 500°C for 2 hours to obtain a catalyst. Add methanol, ethylene carbonate and catalyst into a 75mL autoclave, the molar ratio of ethylene carbonate and methanol is 1:4, the amount of catalyst used is 3% of the total weight of raw materials, and the temperature is raised to 120°C under stirring conditions, and the reaction time is 2 hours . The product was settled by centrifugation, and the supernatant was analyzed by gas chromatography. Analytical method is the same as embodiment 1.

Table 1 Example PC (EC) conversion rate (%) DMC yield (%) DMC selectivity (%) Example 1 36.2 36.0 99.4 Example 2 35.8 35.4 98.9 Example 3 32.5 32.1 98.8 Example 4 39.6 39.1 98.7 Example 5 30.8 30.4 98.7 Example 6 35.4 34.7 98.0 Example 7 40.8 40.1 98.2 Example 8 64.3 63.5 98.7 Example 9 63.3 62.9 99.4

Claims (5)

1. the catalyzer of a Synthesis of dimethyl carbonate is characterized in that weight ratio consists of: the soluble salt of alkaline-earth metal: alkali metal compound: carrier=0.01～0.3: 0.01～0.5: 1;

The soluble salt of described alkaline-earth metal exists with oxide form;

Described alkali metal compound exists with oxide compound or fluorochemical form.

2, catalyzer as claimed in claim 1 is characterized in that the soluble salt of described alkaline-earth metal is: magnesium nitrate, calcium acetate, nitrocalcite, strontium nitrate.

3, catalyzer as claimed in claim 1 is characterized in that described alkali metal compound is: the carbonate of sodium, potassium, caesium, nitrate, acetate, fluorochemical and oxyhydroxide.

4, catalyzer as claimed in claim 1 is characterized in that described carrier is a molecular sieve, gac, silicon oxide, zinc oxide or aluminium sesquioxide.

5, as claim 1,2,3 or 4 Preparation of catalysts methods, it is characterized in that comprising the steps:

Carrier in 300-1000 ℃ of following roasting 1-10 hour, is pressed catalyzer then and formed the carrier incipient impregnation in the soluble salt aqueous solution of alkaline-earth metal, after room temperature leaves standstill 2-30 hour, through 60-200 ℃ of drying, at 350-800 ℃ of following roasting 1-10 hour, reduce to room temperature then, press the catalyzer group after.Incipient impregnation is in the aqueous solution of alkali metal compound, and after room temperature left standstill 2-30 hour, through 100-200 ℃ of drying, 300-900 ℃ obtained catalyzer in following roasting 1-5 hour.