CN101829571A - Method for preparing Cu/SiO2 catalyst - Google Patents

Abstract

The invention relates to a catalyst, in particular to a method for preparing a Cu/SiO2 catalyst. The prepared Cu/SiO2 catalyst has the advantages of higher specific area, Cu loading capacity, dispersibility, stability and the like. The preparation method comprises the following steps of: preparing an ethyl silicate solution containing a surface active agent; preparing an inorganic acid solution; adding the prepared ethyl silicate solution containing a surface active agent to a reaction kettle, simultaneously adding the prepared inorganic acid solution to the reaction kettle, stirring, and aging at constant temperature to obtain a mixed solution; dissolving the obtained mixed solution in absolute ethyl alcohol, stirring, adding catalyst and ethanol, and stirring again to obtain a mixed liquid; adding a copper salt solution containing Cu of 2-5% in calculated amount to the obtained mixed liquid, adding ammonia water to adjust the pH value, stirring, aging at room temperature, carrying out water bath at constant temperature, drying, calcining, grinding, and sieving to obtain the Cu/SiO2 catalyst.

Description

A kind of method for preparing Cu/SiO2 catalyst

technical field

The invention relates to a catalyst, in particular to a catalyst composition suitable for olefin polymerization, a method for preparing a supported catalyst with _SiO2 as a carrier and Cu as an active component.

Background technique

The chemical composition of silica gel is SiO ₂ . At room temperature, there is a layer of physically adsorbed water on the surface of silica gel, and there is a silanol [-SiOH] structure on the surface. At 423-473K, most of the adsorbed water is desorbed, leaving mainly [-SiOH]. At higher temperatures, the adjacent [-OH] dehydrates to form a [Si-O-Si] structure. Silica gel has special pore structure, large specific surface area and excellent thermal stability, and is widely used as adsorbent, desiccant, thickener, chromatographic column support and catalyst support, etc.

As the carrier of the catalyst required for olefin polymerization, silica gel plays a very important role in the catalyst components. Its shape, particle size and distribution, specific surface area, pore size distribution and other parameters can have a great impact on the shape and performance of the polymer. . In the early 1980s, my country began to carry out research on the localization of silica gel carriers suitable for polyolefin catalysts. However, most of the catalyst silica gel carriers used in the polyolefin industry still rely on imports. Therefore, the development of new silica gel carriers for polyolefin catalysts has important practical significance for breaking the long-term monopoly of foreign countries in the field of catalyst carrier silica gel.

The commonly used preparation methods of catalysts mainly include impregnation method, precipitation method, sol-gel method, ion exchange method and so on. The sol-gel method refers to the method in which metal organic or inorganic compounds are solidified through solutions, sols and gels, and then heat-treated to form oxides or other compound solids. Sol is a system in which 1-100nm particles (basic units) are dispersed in the medium. Gel is a solid network containing submicron pores and interconnected polymer chains. The gel structure can be divided into ordered layered structure and disordered copolymerization network. , disordered controlled aggregated networks and particle disordered structures, etc. The sol-gel method has many advantages: the reaction temperature is low, and the reaction process is easy to control; the uniformity and purity of the product are high (the uniformity can reach the molecular or atomic level); the stoichiometry is accurate, easy to modify, and the range of doping is wide (including The amount and type of doping); starting from the same raw material, different products can be obtained by changing the process; the process is simple and does not require expensive equipment.

Olefin polymerization occupies a large proportion in petrochemical industry, and polyolefin catalyst support, as an important part of olefin polymerization industry, has a huge impact on the development of polyolefin. Since the 1980s, many patents have been applied for research on silica gel carriers for polyolefin catalysts at home and abroad, and there have been many reports on related theoretical research. Yao Peihong etc. disclose a kind of preparation method of silica gel carrier in Chinese patent CN1403486, promptly when preparing silica gel, dilute silicate and inorganic acid are simultaneously added in the reactor that is housed with part dilute silicate solution as mother liquor, When the sol and part of the gel appear, adjust the pH value of the mother liquor in the reactor to 5-8.5, and after the hydrosol is completely converted into silica gel, the specific surface area is 200-400m ² /g after aging, washing, treatment and drying , the pore size distribution is 8-15nm, the bulk density is 0.2-0.4g/ml, the pore volume is 1.0-1.2ml/g silica gel carrier. The polyolefin catalyst used in the polyolefin industry requires a silica gel carrier with a pore volume of 1.00-2.00ml/g, a specific surface area of 280-555m ² /g, and a pore size distribution of 9-18nm.

Due to its good catalytic oxidation and catalytic reduction properties, Cu is widely used in chemical engineering, environmental protection, fuel cells and other fields such as oxidation, hydrogenation, catalytic combustion of hydrocarbons, catalytic reduction of _NOx , etc. Copper-based catalysts have been widely used in the field of catalysis due to their high activity, low cost and easy availability. Cu/SiO ₂ catalyst has attracted much attention due to its good hydrogenation selectivity and no environmental pollution. The research on Cu/SiO ₂ catalyst started earlier abroad, and detailed research was carried out in the 1980s and 1990s. Domestic research on Cu/SiO ₂ catalysts started in the 1990s. Li Zhuxia et al. , 2005, 31(1): 27-31; Li Zhuxia. Study on the catalytic hydrogenation of dimethyl oxalate to ethylene glycol [D]. Shanghai: East China University of Science and Technology, 2004.) Research on various oxide supports (γ- Al ₂ O ₃ , SiO ₂ , TiO ₂ and ZrO ₂ ), it was found that Cu/SiO ₂ had the best activity, and the influence of additives (Ni, Zn and Ca) was studied. Huang Weijie et al. (Huang Weijie, Wenfeng, Kang Wenguo, et al. Preparation and modification of Cu/SiO ₂ catalyst for hydrogenation of dimethyl oxalate to ethylene glycol [J]. Industrial Catalysis, 2008, 16(6): 13-17 .) and Wenfeng etc. in (Wenfeng, Huang Weijie, Xiao Wende. Preparation of Cu/SiO ₂ catalyst for hydrogenation of dimethyl oxalate [J]. Guangdong Chemical Industry, 2008, 35 (4): 5-11) respectively studied the steam Influence of preparation factors on Cu/SiO ₂ catalyst prepared by ammonia method and urea precipitation deposition method.

The current research shows that Cu/ _SiO2 catalyst has a wide range of uses as a selective hydrogenation catalyst, and there are many preparation methods, but all of them have certain limitations, such as the carrier impregnation method, which is prone to the occurrence of active components on the edge of the fine particles of the carrier uneven agglomeration; although the ion exchange method can disperse the active components well, the loading capacity of the active components is very low; the Cu/SiO ₂ catalyst prepared by the precipitation deposition method has a low Cu content, and increasing the copper content will lead to surface The copper grain grows up and is easy to sinter.

Contents of the invention

The object of the present invention is to provide a method for preparing Cu/ _SiO2 catalyst, the prepared Cu/ _SiO2 catalyst has advantages such as higher specific surface area, Cu loading capacity, dispersibility and stability.

The technical scheme of the present invention adopts crystal nucleus growth technology and effective particle size control method, and effectively disperses and loads the catalyst into the silica sol through the sol-gel method, thereby obtaining a high specific surface area and Cu loading capacity. Cu/SiO ₂ catalyst with advantages such as , dispersibility and stability.

The present invention comprises the following steps:

1) preparing an ethyl silicate solution containing a surfactant;

2) preparing inorganic acid solution;

3) adding the surfactant-containing ethyl silicate solution prepared in step 1) into the reaction kettle, and simultaneously adding the inorganic acid solution prepared in step 2) into the reaction kettle, stirring, and aging at constant temperature to obtain a mixed solution;

4) Dissolving the mixed solution obtained in step 3) into absolute ethanol, stirring, then adding catalyst and ethanol, and stirring again to obtain a mixed solution;

5) adding copper salt solution containing 2% to 5% Cu in calculated amount to the mixed solution obtained in step 4), adjusting the pH value with ammonia water, stirring, aging at room temperature, drying in a constant temperature water bath, roasting, grinding and sieving to obtain Cu/ _SiO2 catalyst.

In step 1), the surfactant can be selected from sodium dodecylbenzenesulfonate, etc., and the concentration of the sodium dodecylbenzenesulfonate can be 0.01-0.02mol/L; The concentration of the ester solution may be 0.5-1.0 mol/L.

In step 2), the concentration of the inorganic acid solution may be 0.5-1.0 mol/L; the inorganic acid may be selected from one of hydrochloric acid, sulfuric acid and nitric acid.

In step 3), the flow rate of adding the surfactant-containing ethyl silicate solution prepared in step 1) to the reactor can be 2 to 5ml/min; adding step 2) to the reactor The prepared inorganic acid solution should preferably have a pH value of 8.5 to 10 in the reaction kettle; the stirring speed can be 2000 to 3000r/min; the constant temperature aging temperature can be 65 to 85°C, and the constant temperature aging The time can be 1 ~ 2h.

In step 4), the mixed solution obtained in step 3) is dissolved into absolute ethanol, and the mixed solution: absolute ethanol can be 11: (18～20) by volume; the catalyst, ethanol, by volume The catalyst:ethanol ratio can be 1:(2.5-10), and the alcohol-water volume ratio of the ethanol can be 7:11; the catalyst can be selected from HNO ₃ or NH ₄ OH and the like.

In step 5), the concentration of the ammonia water can be 2mol/L, the temperature of the calcination can be 400°C, and the calcination time can be 4h; the copper salt can be selected from Cu(NO ₃ ) ₂ , CuCl ₂ , Cu(CH ₃ COO) ₂ , etc., preferably Cu(NO ₃ ) ₂ ; the pH value is adjusted with ammonia water, preferably the pH value is 6-8; the temperature of the constant temperature water bath can be 60-70°C, and the calcination temperature may be 400°C.

Since the present invention adopts crystal nucleus growth technology and effective particle size control method, the catalyst is evenly and effectively dispersed and loaded into the silica sol by the sol-gel method, so the present invention has the following outstanding advantages: the process is simple and the process conditions are easy to control , the obtained catalyst has high specific surface area, high copper loading capacity, excellent dispersion and stability, and is a very promising catalyst for polyolefins. Tests show that the catalytic efficiency of the catalyst prepared by the invention is significantly higher than that of common catalysts, which is convenient for industrial promotion.

Detailed ways

Example 1

1) Add 200ml of deionized water to the reactor equipped with a thermometer, a pH meter and a stirrer, and start the stirrer at a speed of 3000r/min, so that the temperature of the reactor is 80°C.

2) Prepare an ethyl silicate solution with a concentration of 1.0 mol/L, and then add sodium dodecylbenzenesulfonate to the solution so that the concentration of sodium dodecylbenzenesulfonate is 0.01mol/L. Prepare a nitric acid solution with a concentration of 0.5mol/L.

3) Add ethyl silicate solution in the reaction kettle at a flow rate of 3ml/min, and simultaneously add nitric acid solution dropwise, so that the pH value of the solution in the reaction kettle is 8.5, keep constant stirring speed and constant temperature in the reaction, and dropwise add Afterwards, aging at constant temperature for 1 to 2 hours under stirring.

4) Dissolve 11ml of the solution obtained in step 3) into 18.5ml of absolute ethanol, and stir evenly. 1ml of HNO ₃ and 8ml of ethanol were mixed and poured into the mixture, and stirred evenly.

5) Slowly drop 50 ml of Cu(NO ₃ ) ₂ solution containing 2% Cu into the mixed solution obtained in step 4), adjust the pH value to 7 with ammonia water with a concentration of 2 mol/L, stir vigorously for 1 hour, and age at room temperature 12h, dry in a constant temperature water bath at 60°C for 20h, oven dry at 110°C for 15h, and bake at 400°C for 4h. Grind, sieve, and set aside.

6) The catalyst sample obtained in step 5) was pretreated under vacuum conditions at 300°C for 3 hours, and high-purity nitrogen was used as the adsorbate, and the BET method was used for determination at liquid nitrogen temperature. The measured specific surface area of the catalyst was 716.5m ² /g, and the pore volume was 0.696cc/g.

7) Mix 0.2 mol of the catalyst sample obtained in step 5) with quartz sand of the same particle size and volume and place it in the middle of the pump reactor, control the feed rate of the diethyl oxalate solution to 0.01ml/min, After preheating to a gaseous state, it is mixed with hydrogen to react. The reaction temperature is 220-250° C., the pressure is 0.5-4 MPa, and the hydrogen/ester molar ratio is 170-290. The liquid phase product is analyzed by a 3700 gas chromatograph produced by Varian Company of the United States, and the percentage content of each substance is calculated by the correction factor method to obtain The conversion of diethyl oxalate was 94.5% and the yield of ethylene glycol was 81%.

Example 2

The preparation process is the same as in Example 1. The temperature of the reaction kettle is 80°C, the concentration of the ethyl silicate solution is 1.0mol/L, the concentration of sodium dodecylbenzenesulfonate is 0.01mol/L, the flow rate of the ethyl silicate solution into the reaction kettle is 3ml/min, and the reaction The pH value of the solution in the kettle is 8.5, the calculated amount of Cu in the Cu(NO ₃ ) ₂ solution is 2%, the pH value adjusted by ammonia water is 7.2, the temperature of the constant temperature water bath is 65°C, the specific surface area of the catalyst is 715.5m ² /g, and the pore volume was 0.689cc/g, and the obtained catalyst was used in the reaction of hydrogenating diethyl oxalate to prepare ethylene glycol. The conversion rate of diethyl oxalate was 93.8% and the yield of ethylene glycol was 79.8%.

Example 3

The preparation process is the same as in Example 1. The temperature of the reaction kettle is 85°C, the concentration of the ethyl silicate solution is 0.5mol/L, the concentration of sodium dodecylbenzenesulfonate is 0.01mol/L, the flow rate of the ethyl silicate solution into the reaction kettle is 3ml/min, and the reaction The pH value of the solution in the kettle is 9.0, the calculated amount of Cu in the Cu(NO ₃ ) ₂ solution is 2%, the pH value is adjusted by ammonia water to 7.5, the temperature of the constant temperature water bath is 65°C, the specific surface area of the catalyst is 714.9m ² /g, and the pore volume The obtained catalyst was used in the reaction of diethyl oxalate hydrogenation to prepare ethylene glycol, the conversion rate of diethyl oxalate was 93.5% and the yield of ethylene glycol was 80%.

Example 4

The preparation process is the same as in Example 1. The temperature of the reaction kettle is 80°C, the concentration of the ethyl silicate solution is 1.0mol/L, the concentration of sodium dodecylbenzenesulfonate is 0.02mol/L, the flow rate of the ethyl silicate solution into the reaction kettle is 4ml/min, and the reaction The pH value of the solution in the kettle is 9.0, the calculated amount of Cu in the Cu(NO ₃ ) ₂ solution is 3%, the pH value is adjusted by ammonia water to 7.5, the temperature of the constant temperature water bath is 60°C, the specific surface area of the catalyst is 717.1m ² /g, and the pore volume was 0.693cc/g, and the obtained catalyst was used in the reaction of hydrogenating diethyl oxalate to prepare ethylene glycol, the conversion rate of diethyl oxalate was 95.3% and the yield of ethylene glycol was 83%.

Example 5

The preparation process is the same as in Example 1. The temperature of the reaction kettle is 85°C, the concentration of the ethyl silicate solution is 1.0mol/L, the concentration of sodium dodecylbenzenesulfonate is 0.01mol/L, the flow rate of the ethyl silicate solution into the reaction kettle is 3ml/min, and the reaction The pH value of the solution in the kettle is 9.0, the calculated amount of Cu in the Cu(NO ₃ ) ₂ solution is 3%, the pH value is adjusted by ammonia water, the temperature of the constant temperature water bath is 70°C, the specific surface area of the catalyst is 716.8m ² /g, and the pore volume was 0.701cc/g, and the obtained catalyst was used in the reaction of hydrogenating diethyl oxalate to prepare ethylene glycol, the conversion rate of diethyl oxalate was 94.7% and the yield of ethylene glycol was 81.6%.

Example 6

The preparation process is the same as in Example 1. The temperature of the reaction kettle is 80°C, the concentration of the ethyl silicate solution is 0.5mol/L, the concentration of sodium dodecylbenzenesulfonate is 0.02mol/L, the flow rate of the ethyl silicate solution into the reaction kettle is 4ml/min, and the reaction The pH value of the solution in the kettle is 8.5, the calculated amount of Cu in the Cu(NO ₃ ) ₂ solution is 2%, the pH value adjusted by ammonia water is 7.2, the temperature of the constant temperature water bath is 70°C, the specific surface area of the catalyst is 715.9m ² /g, and the pore volume was 0.688cc/g, and the obtained catalyst was used in the reaction of hydrogenating diethyl oxalate to prepare ethylene glycol, the conversion rate of diethyl oxalate was 94.1% and the yield of ethylene glycol was 80.5%.

Claims (10)

1. prepare Cu/ _SiO The method for catalyst, it is characterized in that comprising the following steps: 1) preparing an ethyl silicate solution containing a surfactant; 2) preparing inorganic acid solution; 3) adding the surfactant-containing ethyl silicate solution prepared in step 1) into the reaction kettle, and simultaneously adding the inorganic acid solution prepared in step 2) into the reaction kettle, stirring, and aging at constant temperature to obtain a mixed solution; 4) Dissolving the mixed solution obtained in step 3) into absolute ethanol, stirring, then adding catalyst and ethanol, and stirring again to obtain a mixed solution; 5) adding copper salt solution containing 2% to 5% Cu in calculated amount to the mixed solution obtained in step 4), adjusting the pH value with ammonia water, stirring, aging at room temperature, drying in a constant temperature water bath, roasting, grinding and sieving to obtain Cu/ _SiO2 catalyst. 2. a kind of preparation Cu/ _SiO as claimed in claim 1 The method for catalyzer is characterized in that in step 1) in, described tensio-active agent is selected from sodium dodecylbenzene sulfonate; Described dodecane The concentration of the sodium phenylsulfonate is 0.01-0.02 mol/L; the concentration of the ethyl silicate solution is 0.5-1.0 mol/L. 3. a kind of preparation Cu/SiO as claimed in claim _1The method for catalyzer is characterized in that in step 2), the concentration of described inorganic acid solution is 0.5～1.0mol/L; Described inorganic acid is selected from One of hydrochloric acid, sulfuric acid and nitric acid. 4. a kind of preparation Cu/SiO as claimed in claim ₁ The method for catalyzer is characterized in that in step 3) in, described step 1) is added to the ethyl silicate solution that contains tensio-active agent The flow rate in the reactor is 2-5ml/min. 5. a kind of preparation Cu/ _SiO as claimed in claim 1 The method for catalyzer, it is characterized in that in step 3) in, described adding step 2) in reactor, the inorganic acid solution prepared is to make reactor The pH value of the medium solution is 8.5-10. 6. a kind of preparation Cu/ _SiO as claimed in claim 1 The method for catalyzer is characterized in that in step 3), the speed of described stirring is 2000～3000r/min; The temperature of described constant temperature aging is 65～ 85°C, the aging time at constant temperature is 1~2h. 7. a kind of preparation Cu/SiO as claimed in claim ₁ The method for catalyzer, it is characterized in that in step 4) in, described step 3) the mixed solution of gained is dissolved in dehydrated alcohol, by volume ratio, mix Solution: absolute ethanol is 11:18-20. 8. a kind of preparation Cu/SiO as claimed in claim ₁ The method for catalyzer is characterized in that in step 4), described catalyst, ethanol, by volume ratio, catalyst: ethanol is 1: 2.5～10, so The alcohol-water volume ratio of the ethanol is 7:11; the catalyst is selected from HNO ₃ or NH ₄ OH. 9. a kind of preparation Cu/SiO as claimed in claim ₁ The method for catalyzer is characterized in that in step 5), the concentration of described ammoniacal liquor is 2mol/L, and the temperature of described roasting is 400 ℃, and the roasted The time is 4h. 10. A method for preparing Cu/SiO ₂ catalyst as claimed in claim 1, characterized in that in step 5), the copper salt is selected from Cu(NO ₃ ) ₂ , CuCl ₂ , Cu(CH ₃ COO ) ₂ , preferably Cu(NO ₃ ) ₂ ; the further use of ammonia water to adjust the pH value is 6-8; the temperature of the constant temperature water bath is 60-70°C.