阅读说明：本技术 用于碳酸二甲酯合成的催化剂及其制备方法和应用 (Catalyst for synthesizing dimethyl carbonate and preparation method and application thereof ) 是由 肖招金 汪俊 单文波 唐大川 倪菁华 于 2020-07-10 设计创作，主要内容包括：本发明提供了一种用于碳酸二甲酯合成的催化剂及其制备方法和应用,属于催化剂的技术领域。该催化剂以氧化铝为载体,以Pd为活性组分,Cu、Ce和Li作为助剂。该催化剂用于一氧化碳与亚硝酸甲酯在低温低压下合成碳酸二甲酯的反应中,具有高活性及高选择性,且稳定性很好,在空速2000～4000h-1,反应温度90～150℃反应条件下,以CO计碳酸二甲酯的选择性达到98％,以MN计碳酸二甲酯的选择性达到95％,碳酸二甲酯的时空产率达到800g/L.Cat/h。(The invention provides a catalyst for synthesizing dimethyl carbonate, a preparation method and application thereof, belonging to the technical field of catalysts. The catalyst takes alumina as a carrier, Pd as an active component and Cu, Ce and Li as auxiliaries. The catalyst is used for the reaction of synthesizing dimethyl carbonate by using carbon monoxide and methyl nitrite at low temperature and low pressure, has high activity, high selectivity and good stability, and under the reaction conditions of an airspeed of 2000-4000 h < -1 > and a reaction temperature of 90-150 ℃, the selectivity of the dimethyl carbonate calculated by CO reaches 98%, the selectivity of the dimethyl carbonate calculated by MN reaches 95%, and the space-time yield of the dimethyl carbonate reaches 800 g/L.Cat/h.)

1. A catalyst for synthesizing dimethyl carbonate is characterized in that: the catalyst comprises the following components by weight of a gamma-Al 2O3 alumina carrier: 0.1-2.5 wt% of active component Pd, 0.01-2.0 wt% of assistant Cu, 0.01-1.5 wt% of Ce and 0.1-5 wt% of assistant Li;

treating the gamma-Al 2O3 alumina carrier by a lithium salt solution with the concentration of 0.01-1 wt% for 6-24 hours, and then roasting for 2-5 hours at 700-1000 ℃;

the lithium salt solution is an aqueous solution of salts such as lithium chloride, lithium bromide, lithium nitrate, lithium acetate and the like, preferably lithium chloride;

the specific surface area of the gamma-Al 2O3 alumina carrier is 100-600 m2/g, the pore volume is 0.1-1.5 cm3/g, and the average pore diameter is 2-30 nm.

2. The preparation method of the catalyst for synthesizing the dimethyl carbonate according to claim 1, which sequentially comprises the following steps:

(a) treating the gamma-Al 2O3 alumina carrier by using LiCl or lithium nitrate solution with the concentration of 0.01-1 wt% for 6-24 hours, and then roasting at 700-1000 ℃ for 2-5 hours;

(b) preparing impregnation liquid by using Pd salt, Cu salt, Ce salt and Li salt according to the measurement, and adjusting the pH value of the impregnation liquid to be 0.1-6;

(c) soaking the carrier obtained in the step (a) in the soaking solution obtained in the step (b) for 1-12 hours;

(d) drying the solid obtained in the step (c) at 50-200 ℃;

(e) roasting the solid obtained in the step (d) at the temperature of 200-500 ℃;

(f) and (e) halogenating the solid obtained in the step (e) by adopting HCl gas with the concentration of 1.0-5.0 v% for 3-10 hours at the temperature of 200-400 ℃ to obtain the finished catalyst.

3. The method for preparing the catalyst for synthesizing the dimethyl carbonate according to claim 2, wherein the Pd salt, the Cu salt, the Ce salt and the Li salt are selected from one or more of nitrate, halide, oxalate or acetate.

4. A method for synthesizing dimethyl carbonate using the catalyst of claim 1, comprising the steps of: namely, raw material gas carbon monoxide and nitrous acid ester are subjected to contact reaction, and nitrogen or carbon dioxide is used as a diluent; the raw material gas is contacted with the catalyst of claim 1, the contact time is 0.1-6 seconds, the reaction temperature is 90-150 ℃, the reaction pressure is normal pressure-1.0 MPaG, the gas hourly space velocity is 2000-5000 h < -1 >, the volume content of CO in the raw material gas is 5-30%, the volume content of CH3ONO is 5-20%, and the gas volume content of HCl is 50-500 ppm.

Technical Field

The invention belongs to the technical field of catalysts, and relates to a catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite, in particular to a catalyst for synthesizing dimethyl carbonate, a preparation method of the catalyst for synthesizing dimethyl carbonate and a method for synthesizing dimethyl carbonate by using the catalyst.

Background

Dimethyl Carbonate (DMC) is a colorless transparent liquid at normal temperature and pressure, is insoluble in water, and can be mixed with organic solvents such as alcohol and ester in any proportion. Dimethyl carbonate is an important organic chemical raw material, has wide application prospect in the fields of pesticides, medicines, plastics, dyes, coatings, new materials and the like, and is known as a 'new base stone' organically synthesized in the 21 st century. DMC is low in toxicity and has excellent solubility, and can be used as a green solvent to replace Freon, trichloromethane, benzene, xylene and the like; the DMC structure contains carbonyl, and can be used as a carbonylation agent to replace phosgene which is a highly toxic and highly corrosive by-product, so as to synthesize carbonic acid derivatives, such as Polycarbonate (PC) and the like. The dimethyl carbonate has high oxygen content (53%), high octane number and low steam pressure, and can be used as additive for gasoline or diesel oil.

The current methods for synthesizing dimethyl carbonate are as follows: phosgene method, ester exchange method, methanol oxidation carbonylation method, urea alcoholysis method, CO2 and methanol direct synthesis method, etc., wherein the industrial production mainly comprises the phosgene method and the 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 uses ethylene carbonate or propylene carbonate and methanol to carry out ester exchange reaction to generate dimethyl carbonate, the raw material supply depends on petroleum, and the generation cost is high.

The synthesis of dimethyl carbonate from CO and methyl nitrite at low temperature and low pressure was first proposed and commercialized by UBE of Japan. The method has mild reaction conditions, part of reaction products can be recycled in the reaction, the reaction is carried out in a gas phase, no water is generated in the reaction, and the harm of water in a liquid phase method to the catalyst is avoided. With the increase of the demand of DMC, the domestic research on the catalyst and the process for synthesizing dimethyl carbonate by CO and methyl nitrite is gradually increased.

A catalyst for synthesizing dimethyl carbonate by gas-phase carbonyl of CO and methyl nitrite is a Cu-Pd bimetallic Wacker type chlorine-containing catalyst prepared by using active carbon, alumina, lithium aluminate spinel and the like as carriers. The chlorine-containing catalyst has good activity and high selectivity, but has the problems of poor stability, short service life, equipment corrosion and the like, and the root cause of the reduction of the activity of the catalyst is the loss of chloride ions on the catalyst. In order to improve the stability of the catalyst, the most common measure is to add a certain amount of chlorine-containing compound, such as HCl or methyl chloroformate, etc., to the raw material gas. For example, U.S. Pat. No. 5,09,09 discloses a catalyst comprising activated carbon as a support, palladium chloride as a main active component, and copper chloride as an auxiliary, wherein the DMC time-space yield is optimally 725g/(L × h), and can be stabilized only for 8 h. U.S. Pat. No. 5688984 discloses a carrier for catalyst for synthesizing dimethyl carbonate, which has lithium aluminate with spinel structure, the catalyst made by using the carrier has higher activity and selectivity, the selectivity calculated by CO and methyl nitrite reaches more than 95%, the performance of the catalyst can be improved to different degrees by adding different additives, but the service life of the catalyst is still shorter. From the data reported in the literature, it is known that the activity of the catalyst decreases by 20% to 30% over a 100 hour reaction period, even with continuous HCl replenishment during the reaction. The catalyst has low activity and short service life, and greatly limits the industrial application of the catalyst.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a catalyst for synthesizing dimethyl carbonate by CO and methyl nitrite at low temperature and low pressure, and the catalyst can keep high activity for a long time under the condition of replenishing chloride ions.

The technical scheme of the invention is to provide a catalyst for synthesizing dimethyl carbonate, which comprises the following components by weight based on an alumina carrier: 0.1-2.5 wt% of active component Pd, 0.01-2.0 wt% of assistant Cu, 0.01-1.5 wt% of assistant Ce and 0.1-5 wt% of assistant Li.

One of the preferable embodiments of the catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite is that the Pd content is 0.2-1.5 wt%.

In another preferred embodiment of the catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite, the Cu content is 0.1 to 1.3 wt%.

In another preferable embodiment of the catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite, the Ce content is 0.1-1.2 wt%.

In the fourth preferred embodiment of the catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite, the Li content is 0.3-3.5 wt%.

The fifth preferable scheme of the catalyst for synthesizing dimethyl carbonate by CO and methyl nitrite is that the specific surface area of the alumina is 100-600 m2/g, the pore volume is 0.1-1.5 cm3/g, and the average pore diameter is 2-30 nm.

The technical scheme of the invention is to provide a preparation method of a catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite, which sequentially comprises the following steps:

(a) treating the gamma-Al 2O3 alumina carrier by using LiCl or lithium nitrate solution with the concentration of 0.01-1 wt% for 6-24 hours, and then roasting at 700-1000 ℃ for 2-5 hours;

(b) preparing impregnation liquid by using Pd salt, Cu salt, Ce salt and Li salt according to the measurement, and adjusting the pH value of the impregnation liquid to be 0.1-6;

(c) soaking the carrier obtained in the step (a) in the soaking solution obtained in the step (b) for 1-12 hours;

(d) drying the solid obtained in the step (c) at 50-200 ℃;

(e) roasting the solid obtained in the step (d) at the temperature of 200-500 ℃;

(f) halogenating the solid obtained in the step (e) by adopting HCl gas with the concentration of 1.0-5.0 v% for 3-10 hours at the temperature of 200-400 ℃ to obtain a finished catalyst;

one of the preferable embodiments of the above preparation method of the catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite is that the palladium salt, the copper salt and the lithium salt are selected from one or more of nitrate, halide, oxalate or acetate, and preferably nitrate or chloride.

The second preferred scheme of the preparation method of the catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite is that the pH value of a mixed solution of palladium salt, copper salt and cerium salt is adjusted to 0.1-6;

in another preferable embodiment of the above catalyst for synthesizing dimethyl carbonate from CO and methyl nitrite, the concentration of HCl gas subjected to halogenation is 1.0 to 5.0 v%.

The technical scheme of the invention is to provide a method for synthesizing dimethyl carbonate by using the catalyst, which comprises the following steps of using nitrogen and carbon dioxide as diluents, contacting feed gas and methyl nitrite with the catalyst for 0.1-6 seconds, controlling the reaction temperature to be 90-150 ℃, controlling the reaction pressure to be normal pressure-1.0 MPaG, controlling the gas hourly space velocity to be 2000-5000 h < -1 >, controlling the volume content of CO in the feed gas to be 5-30%, controlling the volume content of CH3ONO to be 5-20% and controlling the concentration of HCl gas to be 50-500 ppm. Wherein the HCl gas acts as a supplement to the catalyst chlorine loss.

Advantageous effects

The Pd-Cu-Ce/lithium aluminum catalyst prepared by the method is continuously operated for 1000 hours under the reaction conditions of normal pressure of 0.8MPaG, 90-150 ℃ and GHSV of 2000-4000 h < -1 >, the performance of the catalyst is not reduced, the average space-time yield of dimethyl carbonate is up to 650g/L.

Detailed Description

The invention is further illustrated by the following examples, but is not limited thereto.

The catalyst comprises the following components by weight of a gamma-Al 2O3 alumina carrier: 0.1-2.5 wt% of active component Pd, 0.01-2.0 wt% of assistant Cu, 0.01-1.5 wt% of Ce and 0.1-5 wt% of assistant Li; treating the gamma-Al 2O3 alumina carrier with a lithium salt solution with the concentration of 0.01-1 wt% for 6-24 hours, and then roasting for 2-5 hours at 700-1000 ℃; the lithium salt solution is an aqueous solution of salts such as lithium chloride, lithium bromide, lithium nitrate, lithium acetate and the like, preferably lithium chloride; the specific surface area of the gamma-Al 2O3 alumina carrier is 100-600 m2/g, the pore volume is 0.1-1.5 cm3/g, and the average pore diameter is 2-30 nm.

A preparation method of a catalyst for synthesizing dimethyl carbonate sequentially comprises the following steps:

(a) treating the gamma-Al 2O3 alumina carrier with 0.01-1 wt% LiCl or lithium nitrate solution for 6-24 hours, and then roasting at 700-1000 ℃ for 2-5 hours;

(b) preparing impregnation liquid by using Pd salt, Cu salt, Ce salt and Li salt according to the measurement, and adjusting the pH value of the impregnation liquid to be 0.1-6;

(c) soaking the carrier obtained in the step (a) in the soaking solution obtained in the step (b) for 1-12 hours;

(d) drying the solid obtained in the step (c) at 50-200 ℃;

(e) roasting the solid obtained in the step (d) at the temperature of 200-500 ℃;

(f) and (e) halogenating the solid obtained in the step (e) by adopting HCl gas with the concentration of 1.0-5.0 v% for 3-10 hours at the temperature of 200-400 ℃ to obtain the finished catalyst.

A process for preparing the catalyst used to synthesize dimethyl carbonate includes such steps as choosing one or more of nitrate, halide, oxalate and acetate as Pd salt, Cu salt, Ce salt and Li salt.

The method for synthesizing the dimethyl carbonate by using the catalyst comprises the following steps: namely, raw material gas carbon monoxide and nitrous acid ester are subjected to contact reaction, and nitrogen or carbon dioxide is used as a diluent; the raw material gas contacts with the catalyst of claim 1, the contact time is 0.1-6 seconds, the reaction temperature is 90-150 ℃, the reaction pressure is normal pressure-1.0 MPaG, the gas hourly space velocity is 2000-5000 h < -1 >, the volume content of CO in the raw material gas is 5-30%, the volume content of CH3ONO is 5-20%, and the gas volume content of HCl is 50-500 ppm