CN102553592A - A kind of highly dispersed silicon-loaded Cu-based catalyst and preparation method thereof - Google Patents

Abstract

The invention belongs to the technical field of catalysts and preparation methods thereof, in particular to a high-dispersion silicon-loaded Cu-based catalyst for synthetizing ethyl acetate by utilizing an ethanol dehydrogenation reaction and a preparation method of the high-dispersion silicon-loaded Cu-based catalyst. The catalyst is prepared by using transition metal copper as an active ingredient and using SiO2 as a carrier, the copper is loaded on the SiO2 carrier in a high-dispersive way by adopting an ion exchange method, the mass ratio of metallic copper to the SiO2 is (0.01-0.1) : 1, and the metallic copper is in an amorphous state. The catalyst has the characteristics of lower copper loading, higher dispersion degree of an active center, better activity and stability, simple preparation process, low cost and environment friendliness. According to the catalyst disclosed by the invention, the preparation technology is simple, active species are highly dispersed, and the reaction activity of synthetizing the ethyl acetate by utilizing a one-step ethanol catalytic method is high under the condition of lower active ingredient loading capacity.

Description

A kind of highly dispersed silicon-loaded Cu-based catalyst and preparation method thereof

technical field

The invention belongs to the technical field of catalysts and preparation methods thereof, and in particular relates to a highly dispersed silicon-loaded Cu-based catalyst used in the synthesis of ethyl acetate from ethanol dehydrogenation and a preparation method thereof.

Background technique

Ethyl acetate is an important chemical raw material and a good organic solvent. It has excellent solubility and quick drying, and is one of the most widely used fatty acid esters. It is widely used in textile industry, food industry, pharmaceutical industry and fragrance industry. Ethyl acetate is quite active in the world chemical market due to its special properties. Moreover, with the increasing awareness of environmental protection around the world, people are increasingly aware of the environmental hazards of traditional solvents, and there are more and more fields and industries that stop and restrict the use of such solvents. Ethyl acetate, as an alternative solvent, will have a substantial increase in demand. Therefore, no matter from the international or domestic market, ethyl acetate has a certain market potential. At present, the commonly used catalysts for industrial production of ethyl acetate at home and abroad include sulfuric acid, solid acid catalysts, heteropolyacids, noble metals, etc., but the disadvantages of these catalysts are that they are severely corrosive to equipment, waste liquid pollutes the environment, and the production cost is high. Brazilian patent BR-8901776 discloses the production of ethyl acetate from ethanol and oxygen using metallic palladium/r-alumina catalysts. Chinese patent CN1349488A discloses that palladium and heteropolyacids and their salts are loaded on a carrier to obtain a catalyst for the reaction of ethanol and oxygen to prepare ethyl acetate. Chinese patent CN1781899A discloses that molecular sieves are used as catalysts to support nano-gold, and oxygen is used as an oxidant to oxidize ethanol to prepare ethyl acetate without a solvent.

In general, the catalysts reported in current patents, such as sulfuric acid, heteropolyacids, and noble metals, have the disadvantages of polluting the environment, high preparation costs, and the risk of explosion under the condition of aerobic feeding.

Contents of the invention

The technical problem to be solved by the present invention is to provide a copper-based catalyst for synthesizing ethyl acetate from ethanol dehydrogenation and a preparation method of the catalyst. The catalyst is characterized by low copper loading, high dispersion of active centers, good activity and stability, simple preparation process of the catalyst, low price and environmental friendliness.

A highly dispersed silicon-supported copper-based catalyst for the synthesis of ethyl acetate from ethanol dehydrogenation according to the present invention uses transition metal copper as an active component and _SiO as a carrier, and copper is loaded onto SiO by an ion exchange method. ₂ On the carrier, the mass ratio of metallic copper to SiO ₂ is 0.01-0.1:1, and the metallic copper is in an amorphous state. Further, the mass ratio of metallic copper to SiO ₂ is 0.03:1.

The highly dispersed silicon-supported copper-based catalyst of the present invention is based on the complex compound of organic amine and copper salt as the precursor, with silicon dioxide as the carrier, and the organic amine can disperse the active component copper by complexing with copper ions. effect. Simultaneously, comparative experiment was done with ammonia water as complexing agent.

The preparation of the highly dispersed silicon-supported copper-based catalyst of the present invention adopts the ion exchange method, and the specific process is: first, the organic amine is added to the 0.05mol/L copper nitrate solution under stirring conditions, and the consumption of the organic amine is 4 ~ 7ml. The volume of the copper nitrate solution is 30-50ml. After the solution turns dark blue to form an organic complex, add the _SiO2 carrier to the above-mentioned organic complex solution, and then soak (2-12 hours), wash ( Use distilled water 10 to 15 times the volume of copper nitrate solution to filter and wash), dry (dry at room temperature for 1 to 3 days), and roast (400 to 600 °C for 2 to 6 hours) to obtain a highly dispersed silicon-supported copper base. catalyst.

The SiO ₂ carrier is commercial SiO ₂ pellets or mesoporous silicon materials, and the mesoporous silicon materials are SBA-15, MCM-41 molecular sieves, etc.; the organic amines are diethylenetriamine, triethylenetetramine, etc.

The silicon-loaded Cu-based catalyst of the invention has simple preparation process, high dispersion of active species, and high reaction activity for the one-step synthesis of ethyl acetate by catalyzing ethanol under the condition of relatively low loading of active components.

The method that the highly dispersed silicon-loaded copper-based catalyst of the present invention is used in ethanol one-step synthesis of ethyl acetate is as follows: the reaction is carried out in a fixed-bed micro-reaction device under normal pressure, and the reactor is made of a stainless steel tube, and the reactant is Absolute ethanol (injection flow rate 2ml/h), the amount of catalyst used is 2ml, and the injection space velocity of ethanol is 1h ^-1 (the catalyst needs to be reduced with a mixed gas with a volume ratio of _H2 /Ar of 10% at 300°C before the reaction 2～4h), the reaction temperature is 250～320° C., and the reaction time is 4 hours. After the reaction, the reactants and products are analyzed online by gas chromatography.

Description of drawings

Figure 1: XRD patterns of catalysts using different complexing agents;

As shown in the figure, the dispersion peak at around 22.7° belongs to amorphous SiO ₂ . From the figure, we did not observe the diffraction peak of CuO, indicating that CuO is in a highly dispersed and amorphous state.

Figure 2: TPR spectra of catalysts using different complexing agents;

As shown in the figure, the reduction peak at around 245°C belongs to the reduction peak of highly dispersed copper oxide, and the reduction peak at high temperature in the range of 367-400°C belongs to the reduction of Cu ²⁺ which has a strong interaction with the support. . Consistent with the XRD characterization results, no reduction of large particle size copper oxide was found, indicating that the use of organic amines as complexing agents can not only improve the dispersion of active species to a certain extent, but also enhance the interaction between active species and the carrier.

Figure 3: TEM photos of catalysts using different complexing agents (a, b, c: ammonia water, diethylenetriamine, triethylenetetramine);

As shown in the figure, part of CuO aggregates on the catalyst with ammonia water as the complexing agent, the aggregation degree of CuO on the catalyst with diethylenetriamine as the complexing agent weakens, and on the catalyst with triethylenetetramine as the complexing agent CuO on the catalyst is uniformly dispersed on the _SiO2 surface. The TEM results further indicated that the dispersion of active species could be improved by using organic amines as complexing agents.

Detailed ways

Comparative example 1:

1. Catalyst preparation

Take 0.45g Cu(NO ₃ ) ₂ 3H ₂ O, dissolve it in 37mL of distilled water (the concentration of copper nitrate solution is 0.05mol/L), add ammonia water to the solution until the solution turns dark blue, then weigh 4g of 40～ 60-mesh SiO ₂ pellets were added to the above solution, soaked for 6 hours, washed with 450ml of distilled water, and filtered with suction. Dry at room temperature for 2 days, and bake at 400°C for 6 hours in air.

2. Catalyzed one-step synthesis of ethyl acetate from ethanol

With absolute ethanol as the reactant, the injection flow rate is 2ml/h, the catalyst dosage is 2ml, and the reaction space velocity is 1h ^-1 , the catalyst is reduced with 10% volume ratio H ₂ /Ar gas mixture at 300°C for 2h, The reaction temperature is 270°C, and the reactor is made of stainless steel tubes. The reaction is carried out in a fixed-bed micro-reactor under normal pressure. After the reaction, the reaction product is analyzed online by Shimadzu GC-14C gas chromatography for the content of the reactant and product, and the conversion rate of ethanol was 48%, and the selectivity was 15%.

Example 1:

1. Catalyst preparation

Take 0.45g Cu(NO ₃ ) ₂ ·3H ₂ O, dissolve in 37mL distilled water, add diethylenetriamine to the solution until the solution turns dark blue, then weigh 4g of 40-60 mesh SiO ₂ particles and add to the above solution , soak for 24 hours, then wash with distilled water 10 times the volume of the copper nitrate solution, and filter with suction. Dry at room temperature for 1 day, and bake at 500°C for 4 hours in air.

2. Catalyzed one-step synthesis of ethyl acetate from ethanol

With absolute ethanol as the reactant, the injection flow rate is 2ml/h, the catalyst dosage is 2ml, the reaction space velocity is 1h ^-1 , the catalyst is reduced with 10% H ₂ /Ar mixed gas at 300°C for 2h, and the reaction temperature is 270°C, the reactor is made of stainless steel tubes, and the reaction is carried out in a fixed-bed micro-reactor under normal pressure. After the reaction, the contents of the reactants and products are analyzed online by Shimadzu GC-14C gas chromatography, and the conversion rate of ethanol is 53%. The selectivity was 23%.

Example 2:

1. Catalyst preparation

Take 0.45g Cu(NO ₃ ) ₂ ·3H ₂ O, dissolve in 37mL distilled water, add diethylenetriamine to the solution until the solution turns dark blue, then weigh 4g of 40-60 mesh SiO ₂ particles and add to the above solution , soak for 24 hours, then wash with distilled water 15 times the volume of the copper nitrate solution, and filter with suction. Dry at room temperature for 3 days, and bake at 600°C for 2 hours in air.

2. Catalyzed one-step synthesis of ethyl acetate from ethanol

With absolute ethanol as the reactant, the injection flow rate is 2ml/h, the catalyst dosage is 2ml, the reaction space velocity is 1h ^-1 , the catalyst is reduced with 10% H ₂ /Ar mixed gas at 300°C for 2h, and the reaction temperature is 300°C, the reactor is made of stainless steel tubes, and the reaction is carried out in a fixed-bed micro-reactor under normal pressure. After the reaction, the content of the reactants and products is analyzed online by Shimadzu GC-14C gas chromatography, and the conversion rate of ethanol is 67%. , with a selectivity of 20%.

Example 3:

1. Catalyst preparation

Take 0.45g Cu(NO ₃ ) ₂ ·3H ₂ O, dissolve in 37mL distilled water, add triethylenetetramine to the solution until the solution turns dark blue, then weigh 4g of 40-60 mesh SiO ₂ particles and add to the above solution , soaked for 24 hours, then washed with distilled water 13 times the volume of the copper nitrate solution, and filtered with suction. Dry at room temperature for 2.5 days, and bake at 450°C for 5 hours in air.

2. Catalyzed one-step synthesis of ethyl acetate from ethanol

With absolute ethanol as the reactant, the injection flow rate is 2ml/h, the catalyst dosage is 2ml, the reaction space velocity is 1h ^-1 , the catalyst is reduced with 10% H ₂ /Ar mixed gas at 300°C for 2h, and the reaction temperature is 270°C, the reactor is made of stainless steel tubes, and the reaction is carried out in a fixed-bed micro-reactor under normal pressure. After the reaction, the content of the reactants and products is analyzed online by Shimadzu GC-14C gas chromatography, and the conversion rate of ethanol is 55%. , with a selectivity of 21%.

Claims (8)

1. the silicon copper loaded of a high dispersive is catalyst based, it is characterized in that: this catalyst be with transition metal copper as active component, SiO ₂As carrier, adopt ion-exchange with the copper high dispersive load to SiO ₂On the carrier, metallic copper and SiO ₂Mass ratio be 0.01～0.1: 1, metallic copper is an amorphous state.

2. a kind of silicon copper loaded of high dispersive is catalyst based according to claim 1, it is characterized in that: metallic copper and SiO ₂Mass ratio be 0.03: 1.

3. the catalyst based preparation method of silicon copper loaded of the described high dispersive of claim 1; It is characterized in that: at first under stirring condition, organic amine is joined in the 0.05mol/L copper nitrate solution; Consumption 4～the 7ml of organic amine, the volume of copper nitrate solution are 30～50ml, again with SiO ₂Carrier joins in the above-mentioned organic complex solution, and is catalyst based through obtaining high dispersive silicon copper loaded after immersion, washing, drying, the roasting.

4. the catalyst based preparation method of silicon copper loaded of high dispersive as claimed in claim 3 is characterized in that: SiO ₂Carrier is commercial SiO ₂Bead or mesoporous silicon material.

5. the catalyst based preparation method of silicon copper loaded of high dispersive as claimed in claim 4, it is characterized in that: mesoporous silicon material is SBA-15 molecular sieve or MCM-41 molecular sieve.

6. the catalyst based preparation method of silicon copper loaded of high dispersive as claimed in claim 3, it is characterized in that: organic amine is diethylenetriamine or triethylene tetramine.

7. the catalyst based preparation method of silicon copper loaded of high dispersive as claimed in claim 3, it is characterized in that: the time of immersion is 2～12 hours; Be that distilled water with 10～15 times of copper nitrate solution volumes carries out filtration washing; It is dry 1～3 day at ambient temperature; Be 400～600 ℃ of roastings 2～6 hours.

8. the catalyst based application in preparation ethyl acetate of the silicon copper loaded of claim 1 or 2 described a kind of high dispersive.

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