CN1724159A

CN1724159A - Composite oxide load type catalyst and preparation process thereof

Info

Publication number: CN1724159A
Application number: CNA2005100125328A
Authority: CN
Inventors: 谢克昌; 任军; 李忠; 鲍卫仁
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2005-05-24
Filing date: 2005-05-24
Publication date: 2006-01-25
Anticipated expiration: 2025-05-24
Also published as: CN100496721C

Abstract

A composite oxide carried catalyst used for preparing dimethyl carbonate (DMC) from methanol by oxidation and oxidation is prepared through co-gelatinizing ethyl n-silicate and iso-propanol titanium while adding co-porous chloride, copper chloride and palladium chloride, ageing, drying and calcination. Its advantages are high catalytic activity and selectivity and high output rate of DMC.

Description

Composite oxide supported catalyst and preparation method thereof

One, the technical field

The invention discloses a composite oxide supported catalyst and a preparation method thereof, relates to a composite oxide supported catalyst for synthesizing dimethyl carbonate through methanol oxidative carbonylation and a preparation method thereof, and belongs to the technical field of organic chemical synthesis in chemical engineering.

Second, background Art

Dimethyl Carbonate (DMC) is regarded as one of the most important green chemical products in the 21 st century, and can be used as an intermediate to replace highly toxic or carcinogenic chemicals such as phosgene, Dimethyl sulfate, methyl chloride, methyl chloroformate and the like in various fields to carry out organic synthesis reactions such as carbonylation, methylation, methyl esterification, ester exchange and the like; in addition, the composite can be used as a high-quality solvent and a fuel additive due to the excellent solubility and high oxygen content. Because the existing phosgene method process has serious harm to the environment and personnel, the research on the clean synthesis of DMC has attracted extensive attention at home and abroad in recent years, wherein the methanol oxidative carbonylation method takes methanol and carbon monoxide as raw materials, which are respectively important main components of coal chemical products and coal gasification, and accords with the chemical route of taking coal with relatively abundant reserves as raw materials in China. The coal resources in China are rich, the coal gasification and methanol synthesis are perfect in basis and mature in process, the development of the process has outstanding resource advantages and technical advantages, the development is accelerated according to local conditions, and the realization of industrial clean production of DMC is a new way for developing deep coal processing and accelerating the development of downstream products of methanol as soon as possible.

The methanol oxidation carbonylation method is divided into a liquid-phase slurry method and a gas-phase direct method,wherein the liquid-phase slurry method has high DMC yield and wide industrial application prospect. The American Dow chemical industry company uses activated carbon loaded metal Cu, Pd and other chloride catalysts for research on synthesis of DMC by methanol oxidation carbonylation by a liquid-phase slurry method, and the activity and the selectivity are not high; and because Cl is gradually lost in the reaction process, the service life is short, and the separated HCl gas can seriously corrode equipment; the catalyst can be regenerated by increasing the Cl content in the catalyst by introducing HCl gas, and the regeneration activity is highest when Cl/Cu is close to 1. Tomishigo et al have concluded that activated carbon supports CuCl₂Catalyst in the course of reaction, CuCl₂Conversion to basic copper chloride compounds, e.g. Cu₂Cl(OH)₃，CuCl₂·3[Cu(OH)₂]And CuCl₂·5Cu(OH)₂·H₂O, etc. to play a catalytic role. However, as the reaction proceeds, Cl is gradually lost from the surface of the catalyst and copper is converted to CuO or copper oxychloride such as Cu₂O_3/2Cl to lose activity.

It has been found that the addition of alkali metal or transition metal chlorides]Can improve the electronic environment of the catalyst and improve the supported CuCl₂Activity and selectivity of the catalyst. The latest literature reports CuCl for different carriers₂/PVP，PdCl₂-CuCl₂/SiO₂And PdCl₂-CuCl₂the/HMS catalyst also suffers from Cl loss. It was demonstrated that the catalyst was prepared from CuCl₂Although various supported catalysts which are main active components can improve the catalytic performance by adding auxiliary agents or supplementing HCl in the reaction process, the problems of catalyst deactivation and equipment corrosion caused by Cl loss are inevitable, and the problems are difficult to overcome in industrial application.

Lamberti et al have considered that CuI displaces H in Br phi nsted acid after CuCl and HY, HZSM-5 molecular sieves undergo solid ion exchange at high temperature⁺The catalyst exists in a molecular sieve with absolute advantage, is an active center of the reaction for synthesizing DMC by a gas-phase oxygen carbonyl method, and has the following reaction:

(Ze^-: molecular sieve framework anion)

The activity of the Cu (I) Y catalyst prepared by King et al is obviously higher than that of CuCl₂Active carbon, and the stability of the catalyst is greatly increased due to the low Cl ion content. Li faithfully and the like deeply research the solid ion exchange conditions and the catalytic performance of CuCl and HY, HZSM-5 and HMCM-41 molecular sieves, a CuI/MCM-41 catalyst with high activity and stability is innovatively obtained, and research results are cited for many times and are tracked and researched.

Applicants applied sol-gel method to synthesize series TiO₂-SiO₂The initial research shows that the proper preparation conditions, such as pH value, acid catalyst type, roasting temperature and the like, and the acidification treatment conditions are selected to effectively increase the Br phi nsted acid site of the catalyst, improve the loading capacity of active species and reduce the content of Cl in a catalyst system. So far, there is no international preparation of CuC by this methodl/TiO₂-SiO₂，CuCl₂/TiO₂-SiO₂And CuCl₂-PdCl₂/TiO₂-SiO₂The research papers and patent documents of the composite oxide supported catalyst and the synthesis of DMC by methanol oxidative carbonylation on the two catalysts are not reported.

Third, the invention

The invention discloses a composite oxide supported catalyst and a preparation method thereof, and aims to provide a sol-gel method and conditions for preparing a DMC catalyst synthesized by a methanol oxidation carbonylation method. The low-corrosion high-efficiency composite oxide supported catalyst and the preparation method are provided by combining the active components of the catalyst with roasting conditions.

The invention relates to a composite oxide supported catalyst, which is characterized in that the catalyst is a catalyst for synthesizing dimethyl carbonate by oxidative carbonylation of methanol, and the composite oxide supported catalyst is prepared by taking a composite oxide of titanium dioxide and silicon dioxide as a carrier and cuprous chloride, cupric chloride or cupric chloride and palladium chloride as main active components through a one-step sol-gel method.

The preparation method of the composite oxide supported catalyst is characterized by sequentially comprising the following steps of:

I. hydrolyzing Tetraethoxysilane (TEOS) for 1-5 hours at 15-50 ℃ by using ethanol, deionized water and acetic acid under the condition of high-speed stirring to form silica sol; hydrolyzing titanium isopropoxide with ethanol and acetic acid for 0.5-1.5 hours under the condition of high-speed stirring to form titanium sol, and mixing the two kinds of sol to form transparent titanium silica sol;

II. Dissolving chloride in absolute ethyl alcohol under the condition of high-speed stirring, adding the dissolved chloride into the prepared titanium silicasol, and highly dispersing the chloride in the titanium silicasol through a gelation process;

and III, putting the obtained gel into an oven for blast drying, and finally roasting for 3-10 hours in a nitrogen atmosphere to obtain the composite oxide supported catalyst.

The method for preparing a composite oxide supported catalyst of claim 1, wherein the chloride comprises CuCl or CuCl₂And PdCl₂。

The method for preparing a composite oxide supported catalyst according to claim 1, wherein the CuCl is CuCl to be purified, and the purification method comprises the following steps in order:

I. putting CuCl into a beaker, adding concentrated hydrochloric acid into the beaker, adding distilled water, stirring, standing for a period of time, and transferring the upper-layer liquid into another beaker;

II. Gradually adding distilled water into the beaker containing the upper layer liquid, changing the solution from blue-black to light-blue and generating a large amount of white precipitate, stirring, and standing to ensure that the CuCl is fully crystallized;

III, washing the fully crystallized CuCl crystals with ethanol and acetone in turn, and dissolving the washed crystals in N₂Heating to 50-70 deg.C in a protective furnace, drying for 2-3 hr, and cooling to room temperature.

The composite oxide supported catalyst and the preparation method have the advantages that: the following facts were found by a number of tests: (a) CuCl/TiO₂-SiO₂During the preparation process of the catalyst, the added CuCl content is about 15 percent, and the activity is highest; (b) cl is gradually removed from the catalyst system at a higher roasting temperature, and the stability of the catalyst is gradually increased; (c) CuCl and CuCl₂The content of (A) has good activity within 12-18%; (d) the roasting temperature is more suitable in the temperature range of 500-700 ℃; (e) CuCl/TiO₂-SiO₂，CuCl₂/TiO₂-SiO₂And CuCl₂-PdCl₂/TiO₂-SiO₂The space-time yield of DMC of the composite oxide supported catalyst can reach 0.3-0.9 kg/kg.h within the test temperature range of 120-140 ℃, and the selectivity of DMC reaches 60-98%.

Fourth, detailed description of the invention

Embodiment 1:

a) adding 25mL of tetraethoxysilane into 50mL of absolute ethyl alcohol with the temperature of 20 ℃, sequentially adding 6mL of deionized water and 12.5mL of acetic acid, stirring and hydrolyzing for 1 hour;

b) adding 3.3mL of titanium isopropoxide into 6.6mL of absolute ethanol with the temperature of 20 ℃, then adding 1.7mL of acetic acid, stirring and hydrolyzing for 30 minutes, mixing with the prehydrolyzed silica sol, and strongly stirring for 1 hour at 20 ℃ to form transparent sol;

c) dissolving 2.2g of purified CuCl in 60mL of ethanol solution, then adding the solution into titanium silicasol, and stirring the solution at room temperature to form composite gel;

d) the gel is aged for 50 to 200 hours at the temperature of 20 ℃ to form xerogel;

e) the obtained xerogel is sintered for 3 to 10 hours at 550 ℃ in a muffle furnace, and is naturally cooled to room temperature to obtain about 9.7g of CuCl/TiO₂-SiO₂A composite metal oxide supported catalyst.

Embodiment 2:

a) adding 6mL of ethyl orthosilicate into 12mL of anhydrous ethanol with the temperature of 20 ℃, sequentially adding 1.5mL of deionized water and 3mL of acetic acid, and stirring for hydrolysis for 1 hour;

b) adding 24mL of titanium isopropoxide into 48mL of 20 ℃ anhydrous ethanol, then stirring and hydrolyzing 12mL of acetic acid for 30 minutes, mixing with prehydrolyzed silica sol, and then strongly stirring for 1 hour at 20 ℃ to form transparent sol;

c) 4.6g of purified CuCl₂·2H₂Dissolving O in 100mL of ethanol solution, then adding the solution into titanium silicasol, and stirring the solution at room temperature to form composite gel;

e) the obtained dry gel is sintered for 3 to 10 hours at 550 ℃ in a muffle furnace, and is naturally cooled to room temperature to obtain about 11.6g of CuCl₂/TiO₂-SiO₂A composite metal oxide supported catalyst.

Embodiment 3:

a) adding 20mL of ethyl orthosilicate into 40mL of absolute ethyl alcohol with the temperature of 20 ℃, sequentially adding 5mL of deionized water and 10mL of acetic acid, and stirring for hydrolysis for 1 hour;

b) adding 8.9mL of titanium isopropoxide into 18mL of 20 ℃ anhydrous ethanol, then adding 4.5mL of acetic acid, stirring and hydrolyzing for 30 minutes, mixing with prehydrolyzed silica sol, and strongly stirring for 1 hour at 20 ℃ to form transparent sol;

c) 2.3g of CuCl₂·2H₂O and 2.3g of PdCl₂Dissolving in 100mL of ethanol solution, then adding into titanium silicasol, and stirring at room temperature to form composite gel;

e) the obtained dry gel is sintered for 3 to 10 hours at 550 ℃ in a muffle furnace, and is naturally cooled to room temperature to obtain about 11.9g of CuCl₂-PdCl₂/TiO₂-SiO₂A composite metal oxide supported catalyst.

Claims

1. A composite oxide supported catalyst for synthesizing dimethyl carbonate by oxidizing and carbonylating methanol is prepared from the composite oxide of titanium dioxide and silicon dioxide as carrier, and the cuprous chloride, copper chloride or copper chloride and palladium chloride as active components through one-step sol-gel process.

2. The method for preparing a composite oxide supported catalyst according to claim 1, characterized in that the preparation method comprises the following steps in order:

3. The method according to claim 2 for preparing a composite oxide supported catalyst according to claim 1, wherein the chloride comprises CuCl, CuCl₂And PdCl₂。

4. The method for preparing a composite oxide supported catalyst according to claim 1, wherein the CuCl is CuCl to be purified, according to claim 2, which comprises the following steps in order: