阅读说明：本技术 一种用于一氧化碳催化偶联合成碳酸二甲酯的催化剂及其制备方法与应用 (Catalyst for synthesizing dimethyl carbonate by catalytic coupling of carbon monoxide and preparation method and application thereof ) 是由 杨菊群 朱燕 王志光 吴良泉 于 2018-12-20 设计创作，主要内容包括：本发明提供一种用于一氧化碳催化偶联合成碳酸二甲酯的催化剂及其制备方法与应用,所述催化剂包括改性复合氧化物载体、金属钯活性组分和过渡金属助剂,所述改性复合氧化物载体为VIB族元素改性的γ-氧化铝,所述金属钯活性组分中金属钯元素为γ-氧化铝重量的0.3～1.5％,所述过渡金属助剂中过渡金属元素为γ-氧化铝重量的0.5～3.5％。本发明的催化剂可应用于CO与亚硝酸甲酯在低温低压条件下气相合成碳酸二甲酯,具有较高的低温活性、选择性和时空产率,而且反应性能稳定,能进行较长时间的运转。(The invention provides a catalyst for synthesizing dimethyl carbonate by catalytic coupling of carbon monoxide, and a preparation method and application thereof, wherein the catalyst comprises a modified composite oxide carrier, a metal palladium active component and a transition metal auxiliary agent, the modified composite oxide carrier is gamma-alumina modified by VIB group elements, the metal palladium element in the metal palladium active component is 0.3-1.5% of the weight of the gamma-alumina, and the transition metal element in the transition metal auxiliary agent is 0.5-3.5% of the weight of the gamma-alumina. The catalyst of the invention can be applied to gas phase synthesis of dimethyl carbonate by CO and methyl nitrite under the conditions of low temperature and low pressure, has higher low-temperature activity, selectivity and space-time yield, has stable reaction performance, and can operate for a longer time.)

1. The catalyst for synthesizing the dimethyl carbonate by catalytic coupling of carbon monoxide is characterized by comprising a modified composite oxide carrier, a metal palladium active component and a transition metal additive, wherein the modified composite oxide carrier is gamma-alumina modified by VIB group elements, the metal palladium element in the metal palladium active component accounts for 0.3-1.5 wt% of the gamma-alumina, and the transition metal element in the transition metal additive accounts for 0.5-3.5 wt% of the gamma-alumina.

2. The catalyst of claim 1, further comprising at least one of the following features:

1) the group VIB element is at least one of chromium, molybdenum and tungsten;

2) the VIB group element accounts for 1-4% of the weight of the gamma-alumina;

3) the transition metal element is selected from at least one of Fe, Co, Ag and Cu;

4) the gamma-alumina composite material further comprises an alkali metal auxiliary agent, wherein the total weight of a transition metal element in the transition metal auxiliary agent and an alkali metal element in the alkali metal auxiliary agent is 0.5-5% of the weight of the gamma-alumina.

3. The catalyst according to claim 2, wherein in feature 5), the alkali metal element is at least one selected from the group consisting of L i, Na, K and Rb.

4. A method for preparing a catalyst according to any one of claims 1 to 3, comprising the steps of:

1) according to the composition ratio of the catalyst, adopting an isometric impregnation method to impregnate an aqueous solution of soluble salt of a transition metal auxiliary agent onto a modified composite oxide carrier, and then drying and roasting the carrier;

2) dipping an aqueous solution of soluble salt of metallic palladium on the modified composite oxide carrier loaded with the transition metal auxiliary agent obtained in the step 1) by adopting an isometric dipping method, and then drying and roasting to obtain the catalyst.

5. The method of claim 4, further comprising at least one of the following features:

1) in the step 1), soaking the aqueous solution of soluble salt of the transition metal auxiliary agent and the aqueous solution of soluble salt of the alkali metal auxiliary agent on the modified composite oxide carrier by adopting an isometric soaking method;

2) in the step 1), the soluble salt of the transition metal additive is selected from at least one of chloride, nitrate and acetate of Fe, Co, Ag and Cu;

3) in the step 1), the concentration of the transition metal element in the aqueous solution of the soluble salt of the transition metal assistant is 0.6-3.0 wt%;

4) in the step 1), the dipping time is 0.5-4 hours;

5) in the step 1), drying is carried out in a mode of volatilizing moisture through ultrasonic heating;

6) in the step 1), the roasting temperature is 300-400 ℃;

7) in the step 1), the roasting time is 2-6 hours;

8) in the step 2), the soluble salt of the metal palladium is at least one selected from palladium nitrate, palladium chloride and palladium sulfate;

9) in the step 2), the concentration of the metallic palladium element in the aqueous solution of the soluble salt of the metallic palladium is 0.35-1.76 wt%;

10) in the step 2), adjusting the pH value of the aqueous solution of the soluble salt of the metallic palladium to 1.0-2.0;

11) in the step 2), the dipping time is 0.5-2 hours;

12) in the step 2), drying is carried out in a mode of volatilizing moisture through ultrasonic heating;

13) in the step 2), the roasting temperature is 200-300 ℃;

14) in the step 2), the roasting time is 2-6 hours.

6. The method according to claim 5, wherein the method according to claim 1) further comprises at least one of the following features:

1) the soluble salt of the alkali metal auxiliary agent is selected from at least one of chloride, nitrate and acetate of L i, Na, K and Rb;

2) the total concentration of the transition metal element and the alkali metal element in the aqueous solution of the soluble salt of the transition metal assistant and the soluble salt of the alkali metal assistant is 0.6-4.7 wt%.

7. The production method according to claim 4, wherein the modified composite oxide support is obtained by a production method comprising: the water solution of soluble salt containing VIB group element compound is dipped on the gamma-alumina by an isometric dipping method, and then is dried and roasted.

8. The method of claim 7, further comprising at least one of the following features:

a) the VIB group element-containing compound is at least one selected from chromium nitrate, ammonium metatungstate, ammonium paratungstate and ammonium molybdate;

b) the concentration of the VIB group element in the water solution of the soluble salt containing the VIB group element compound is 1.18-4.7 wt%;

c) the dipping time is 0.5 to 4 hours

d) Drying the mixture in a mode of ultrasonically heating to volatilize water; can be heated at 85 deg.C for 4 hr;

e) the roasting temperature is 500-800 ℃;

f) the roasting time is 2-6 hours.

9. The use of a catalyst as claimed in any of claims 1 to 3 for the CO-catalyzed coupling synthesis of dimethyl carbonate.

10. The use of claim 9, wherein the dimethyl carbonate gas phase synthesis reaction adopts a fixed bed reactor, the raw material gas of carbon monoxide and nitrite is diluted by nitrogen, trace HCl gas is mixed, the contact time of the raw material gas and the catalyst is 0.2-4 seconds, the reaction temperature is controlled at 100-130 ℃,the reaction pressure is controlled to be between normal pressure and 0.6MPa, the volume content of CO in the feed gas is 10-30 percent, and CH₃The ONO has a volume content of 5-20% and the HCl content in the mixed gas is 50-300 ppm.

Technical Field

The invention relates to a catalyst for synthesizing dimethyl carbonate by carbon monoxide gas phase catalysis, a preparation method and application thereof, belonging to the field of catalyst preparation.

Background

Dimethyl carbonate (DMC), a colorless transparent liquid at normal temperature and pressure, is slightly fragrant, is insoluble in water, and can be mixed with organic solvents such as alcohol and ester in any proportion. Dimethyl carbonate is a non-toxic and environment-friendly chemical raw material with excellent development prospect, is known as an important and broad-spectrum green chemical in the 21 st century, and is widely applied to the fields of medicines, pesticides, solvents, gasoline additives and the like. The current industrial synthesis methods of dimethyl carbonate mainly comprise a phosgene method and an ester exchange method. The phosgene method is a traditional synthesis method, uses highly toxic phosgene as a raw material, has poor safety and pollutes the environment, and the generated byproduct HCl has high corrosivity to equipment. The ester exchange method takes propylene carbonate and methanol as raw materials to carry out ester exchange to generate dimethyl carbonate, the raw materials depend on petroleum, and the production cost is high.

The method for synthesizing the dimethyl carbonate by CO and methyl nitrite in a low-pressure gas phase mode is a method which gradually attracts attention in recent years, the reaction condition is mild, other reaction products can be recycled in the reaction, the method is environment-friendly and pollution-free, a fixed bed reactor is adopted, the catalyst and the products do not need to be separated, no water is generated in the main reaction, and the service life of the catalyst is prolonged.

The U.S. Pat. No. 5,09,09,09,220,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,09,indicated herein, wherein the catalyst is supported on activated carbon, the major active component is palladium chloride, the CO-active component is copper chloride, the DMC yield is preferably 725 g/(L h), and is stable for only about 8h, 50-1000 ppm of methyl chloroformate is used as a chlorine-supplementing agent, although the catalyst life can be greatly extended, the catalyst activity is still reduced by 20-30% within 100 hours, and the catalyst life needs to be improved.

The catalyst with high activity, high selectivity and long service life is the key for realizing the low-pressure gas-phase synthesis of dimethyl carbonate by CO and methyl nitrite, and the key technical problem in the field is how to ensure that the catalyst has high activity, high selectivity and long service life.

Disclosure of Invention

Aiming at the defects that the catalyst in the prior art can not maintain high activity for a long time and is poor in stability, the invention provides the catalyst with excellent performance for synthesizing the dimethyl carbonate by catalytic coupling of carbon monoxide, and the preparation method and the application thereof.

The invention is realized by the following technical scheme:

the invention provides a catalyst for synthesizing dimethyl carbonate by catalytic coupling of carbon monoxide, which comprises a modified composite oxide carrier, a metal palladium active component and a transition metal additive, wherein the modified composite oxide carrier is gamma-alumina modified by VIB group elements, the metal palladium element in the metal palladium active component is 0.3-1.5% of the weight of the gamma-alumina, such as 0.3-0.5%, 0.5-0.75%, 0.75-1% or 1-1.5%, and the transition metal element in the transition metal additive is 0.5-3.5% of the weight of the gamma-alumina, such as 0.5-1%, 1-2% or 2-3.5%.

Preferably, at least one of the following features is also included:

1) the group VIB element is at least one of chromium, molybdenum and tungsten; even more preferably tungsten or molybdenum;

2) the VIB group element accounts for 1-4% of the weight of the gamma-alumina, such as 1-2% or 2-4%;

3) the transition metal element is selected from at least one of Fe, Co, Ag and Cu;

4) the composite material also comprises an alkali metal additive, wherein the total weight of the transition metal element in the transition metal additive and the alkali metal element in the alkali metal additive is 0.5-5% of the weight of the gamma-alumina, such as 0.5-3.36% or 3.36-5%.

More preferably, in the feature 5), the alkali metal element in the alkali metal assistant is at least one selected from L i, Na, K, and Rb.

The second aspect of the present invention provides a method for preparing the above catalyst, comprising the steps of:

1) according to the composition ratio of the catalyst, adopting an isometric impregnation method to impregnate an aqueous solution of soluble salt of a transition metal auxiliary agent onto a modified composite oxide carrier, and then drying and roasting the carrier;

2) dipping an aqueous solution of soluble salt of metallic palladium on the modified composite oxide carrier loaded with the transition metal auxiliary agent obtained in the step 1) by adopting an isometric dipping method, and then drying and roasting to obtain the catalyst.

Preferably, at least one of the following features is also included:

1) in the step 1), soaking the aqueous solution of soluble salt of the transition metal auxiliary agent and the aqueous solution of soluble salt of the alkali metal auxiliary agent on the modified composite oxide carrier by adopting an isometric soaking method;

2) in the step 1), the soluble salt of the transition metal additive is selected from at least one of chloride, nitrate and acetate of Fe, Co, Ag and Cu;

3) in the step 1), the concentration of the transition metal element in the aqueous solution of the soluble salt of the transition metal assistant is 0.6-3 wt%, such as 0.6-1.17 wt%, 1.17-2.35 wt% or 2.35-3.0 wt%;

4) in the step 1), the dipping time is 0.5-4 hours;

5) in the step 1), drying is carried out in a mode of volatilizing moisture through ultrasonic heating; can be heated at 85 deg.C for 4 hr;

6) in the step 1), the roasting temperature is 300-400 ℃;

7) in the step 1), the roasting time is 2-6 hours;

8) in the step 2), the soluble salt of the metal palladium is at least one selected from palladium nitrate, palladium chloride and palladium sulfate;

more preferably palladium chloride, PdCl₂The impregnation liquid system forms stable [ PdCl ] in the solution₄]^2-The complex structure can easily regulate and control the dispersion and distribution of the active component on the carrier in the preparation process of the catalyst;

9) in the step 2), the concentration of the metallic palladium element in the aqueous solution of the soluble salt of metallic palladium is 0.35-1.76 wt%, such as 0.35-0.6 wt%, 0.6-0.88 wt%, 0.88-1.18 wt% or 1.18-1.76 wt%;

10) in the step 2), adjusting the pH value of the aqueous solution of the soluble salt of the metallic palladium to 1.0-2.0, such as 1.0-1.2, 1.2-1.3 or 1.3-2.0, for example, adjusting the acidity by using hydrochloric acid;

11) in the step 2), the dipping time is 0.5-2 hours;

12) in the step 2), drying is carried out in a mode of volatilizing moisture through ultrasonic heating; can be heated at 85 deg.C for 4 hr;

13) in the step 2), the roasting temperature is 200-300 ℃;

14) in the step 2), the roasting time is 2-6 hours.

More preferably, in the feature 1), at least one of the following features is further included:

1) the soluble salt of the alkali metal auxiliary agent is selected from at least one of chloride, nitrate and acetate of L i, Na, K and Rb;

2) the total concentration of the transition metal element and the alkali metal element in the aqueous solution of the soluble salt of the transition metal assistant and the soluble salt of the alkali metal assistant is 0.6-4.7 wt%, such as 0.6-3.95 wt% or 3.95-4.7 wt%.

More preferably, the modified composite oxide support is obtained by a production method comprising the steps of: the water solution of soluble salt containing VIB group element compound is dipped on the gamma-alumina by an isometric dipping method, and then is dried and roasted.

Still more preferably, at least one of the following features is also included:

a) the soluble salt of the VIB group element-containing compound is selected from at least one of chromium nitrate, ammonium metatungstate, ammonium paratungstate and ammonium molybdate; ammonium metatungstate or ammonium molybdate is preferred; more preferably ammonium metatungstate;

b) the concentration of the VIB group element in the water solution of the soluble salt containing the VIB group element compound is 1.18-4.7 wt%, such as 1.18-2.35 wt% or 2.35-4.7 wt%;

c) the dipping time is 0.5-4 hours;

d) drying the mixture in a mode of ultrasonically heating to volatilize water; can be heated at 85 deg.C for 4 hr;

e) the roasting temperature is 500-800 ℃, such as 500-600 ℃ or 600-800 ℃;

f) the roasting time is 2-6 hours.

The third aspect of the invention provides the application of the catalyst, which is used for synthesizing dimethyl carbonate by CO catalytic coupling.

Preferably, a fixed bed reactor is adopted in the dimethyl carbonate gas-phase synthesis reaction, raw material gas carbon monoxide and nitrous acid ester are diluted by nitrogen, trace HCl gas is mixed, the contact time of the raw material gas and a catalyst is 0.2-4 seconds, the reaction temperature is controlled at 100-130 ℃, the reaction pressure is controlled at normal pressure-0.6 MPa, the volume content of CO in the raw material gas is 10-30%, and CH is contained in the raw material gas₃The ONO has a volume content of 5-20% and the HCl content in the mixed gas is 50-300 ppm.

The invention has the technical effects and advantages that:

the catalyst comprises a modified composite oxide carrier, wherein the modified composite oxide carrier is gamma-alumina modified by VIB group elements, the electron transfer performance between an auxiliary agent and an active component is improved, the catalyst optimizes the dispersion and distribution state of the active component in the modified composite oxide carrier by impregnating the auxiliary agent and the active component step by step, and the catalyst has high low-temperature activity, selectivity and space-time yield, is stable in reaction performance and can be operated for a long time.

Drawings

FIG. 1 is a graph of the stability of the catalyst prepared in example 2.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.