CN103316677A - Catalyst for dehydrogenation of sec-butyl alcohol and preparation method thereof - Google Patents

Abstract

The invention relates to a catalyst for the dehydrogenation of sec-butanol and a preparation method. It uses CuO and SiO ₂ as active components, and its components and proportions are as follows in terms of mass percentage: CuO 50~70%, SiO ₂ 30~50%; the preparation of the catalyst includes the following steps: soluble copper salt is prepared into a certain amount with distilled water Concentration solution, and calculate the amount of corresponding amount of soluble silicate according to the mass percentage specified by the catalyst, and configure it into a solution with the same concentration as the copper salt solution; put the two solutions in a water bath at a constant temperature of 30°C and stir fully Mix, and use buffer solution to control the pH value of the solution during precipitation at 3~7, and maintain the mixing process at 0.5~1h; stop stirring and then age, wash and filter, dry and roast, and shape to obtain the finished catalyst. The preparation process of the catalyst of the invention is simple, and the thermal stability is good. The catalyst is used in the process of preparing methyl ethyl ketone by dehydrogenating the sec-butanol, and improves the conversion rate of the sec-butanol and the selectivity of the methyl ethyl ketone.

Description

Catalyst for dehydrogenation of sec-butanol and preparation method thereof

technical field

The invention relates to a catalyst for the dehydrogenation of sec-butanol and a method for preparing the catalyst.

Background technique

In the process of catalytic dehydrogenation of sec-butanol to prepare methyl ethyl ketone, Cu-Zn-Al catalysts are usually used in China at present, but with the continuous improvement of industrial application requirements, the development of high-performance sec-butanol dehydrogenation catalysts has been attracting attention. All provide the method for improving Cu-Zn-Al catalyst performance in Chinese patent CN1289752A and CN1289753A, as by adding alkali metal oxide in catalyst component or adding organic amine in organic raw material to eliminate Cu-Zn-Al catalyst The acid center inhibits the side reactions of alcohol dehydration and further condensation of methyl ethyl ketone. Although the nano-metal catalyst prepared in the Chinese patent CN1415591A improves the selectivity of ketone products without using other carriers, the preparation process of its nano-scale metal catalyst involves high requirements such as high vacuum and gas-induced arcing. At the same time Nano-scale catalysts should be stored under anaerobic conditions. These requirements in preparation and use limit the popularization and application of nano-scale metal catalysts. Chinese patent CN101269331A prepares mesoporous Cu-Zn-Al catalyst by adding an organic active agent in the process of co-precipitation. This method increases the catalyst activity by increasing the pore size and surface area. Existing studies have shown that mesoporous materials have pore walls It is thinner, has poor thermal stability, and is easy to collapse during use, thus limiting its use. Unfortunately, the patent does not disclose thermal stability data about mesoporous Cu-Zn-Al catalysts. In addition, Chinese patent CN102247855A introduces Zr and alkali metal oxides on the basis of Cu-Zn-Al catalyst prepared by co-precipitation method to solve the problems of poor activity and low selectivity of methyl ethyl ketone.

At present, research on Cu- _SiO2 catalysts for dehydrogenation of sec-butanol is also carried out at home and abroad, basically using silica gel, silica sol and organic silicon grease as silicon sources, and preparing them by methods such as ion exchange, sol-gel, and ammonia distillation. However, these methods have limited their large-scale application due to the defects of their own processes. The ion exchange method can only prepare catalysts with poor activity and low copper content; the long-term gelation process of the sol-gel method and the formation of gels that are difficult to wash make this process difficult to industrialize; The ammonia process consumes high energy and takes a long time. In addition, due to the presence of ammonia, the process inevitably leads to the loss of copper ions and ammonia to form water-soluble copper ammonium ions, and it is impossible to obtain a catalyst with high copper content.

From the above analysis, it can be seen that the relevant patents basically focus on improving the problems in the preparation of Cu-Zn-Al catalyst by co-precipitation method. Although some progress has been made in improving the conversion rate of sec-butanol and the selectivity of methyl ethyl ketone, it still cannot meet the requirements of industrial production. . The existing Cu-SiO ₂ catalyst preparation methods all have their own limitations so that this type of catalyst cannot be applied industrially. In addition, it is well known that Cu catalysts have poor stability due to high-temperature sintering, which has been difficult to meet the requirements of oxidation regeneration and long-term industrial operation. The existing patents and research have not reported the improvement of the thermal stability of the catalyst.

Contents of the invention

The present invention aims to overcome the problems in the background technology, and provide a catalyst for dehydrogenation of sec-butanol and a preparation method thereof. The catalyst for the dehydrogenation of sec-butanol can greatly improve the conversion rate of sec-butanol and the selectivity of methyl ethyl ketone, and has good thermal stability while maintaining a high dispersion of Cu.

The present invention can solve the problem by the following technical scheme: a catalyst for the dehydrogenation of sec-butanol, which uses CuO and _SiO as active components, and its components and proportioning are as follows by mass percentage: CuO50～70 %, SiO ₂ 30-50%.

A preparation method for a catalyst for sec-butanol dehydrogenation, comprising the following steps:

Step a, dissolving the soluble copper salt into a certain concentration solution with distilled water, and calculating the corresponding amount of soluble silicate according to the mass percentage specified by the catalyst, and disposing it into a solution with the same concentration as the copper salt solution; Step b. Fully mix the two solutions in a water bath at a constant temperature of 30°C with stirring, and use a buffer solution to control the pH value of the solution during precipitation at 3 to 7, and maintain the mixing process at 0.5 to 1 hour; Chemicalization, washing with distilled water, filtration, drying, roasting, and tablet molding to obtain the finished catalyst.

The concentrations of the soluble copper salt and the soluble silicate solution are both 0.5-1.0mol/L; the molar ratio of the soluble copper salt to the soluble silicate is 0.95-2.20; the soluble copper salt is copper nitrate , sulfate, acetate or one or more mixtures; the soluble silicate is sodium silicate, potassium silicate or lithium silicate; the aging condition is: the aging temperature is 30～70 ℃, the aging time is 1～3h, and the pH value is 4～6; the described buffer solution is acetic acid-sodium acetate, citric acid-sodium citrate or potassium hydrogen phthalate; the described washing and filtering conditions are: The conductivity of the final precipitation mother liquor is less than 800μs/cm; the drying temperature is 120-150°C, and the drying time is 2-4h; the roasting conditions are: the roasting temperature is 400-600°C, and the roasting time is 4-6h.

Compared with the above-mentioned background technology, the present invention can have the following beneficial effects: the preparation process of the catalyst used for the dehydrogenation of sec-butanol is simple, and when the catalyst is used in the process of preparing methyl ethyl ketone from the dehydrogenation of sec-butanol, it not only improves the yield of sec-butanol Conversion rate and methyl ethyl ketone selectivity, and the catalyst has good thermal stability.

Description of drawings:

Accompanying drawing 1 is the HTEM image of the catalyst prepared in Example 1 after being treated at a high temperature of 390°C.

Detailed ways:

The present invention will be further described below in conjunction with specific embodiment:

Example 1:

Add 45.38g of Cu(NO ₃ ) ₂ ·3H ₂ O to 289ml of distilled water to make a 0.65mol/L aqueous solution, and add 37.87g of Na ₂ SiO ₃ .9H ₂ O to 205ml of distilled water to make a 0.65mol/L aqueous solution. Move the two solutions to the separatory funnel respectively, drop them into the 1000ml beaker containing 200ml potassium hydrogen phthalate buffer solution at a constant speed in the way of co-current precipitation, keep the temperature of the water bath at 30°C and keep stirring during the dropping process, The pH value of the precipitation solution is controlled at 4-5 by the buffer solution, and the precipitation time is maintained at 0.5h. After the titration, keep stirring for 5 minutes and then stop stirring. The mother liquor is aged at a constant temperature of 30°C for 2h, then moved to a Buchner funnel and washed with distilled water until the conductivity is lower than 800μs/cm, then filtered and dried at 120°C for 10h , Calcined at 500°C for 5h, and made into 20-40 mesh particles, a catalyst A was obtained. The CuO content of the catalyst was 60.60% and the SiO ₂ content was 38.82% as determined by XRF.

Example 2:

Add 37.81g Cu(NO ₃ ) ₂ ·3H ₂ O to 240ml distilled water to make a 0.65mol/L aqueous solution, and add 47.33gNa ₂ SiO ₃ .9H ₂ O to 257ml distilled water to make a 0.65mol/L aqueous solution. Move the two solutions to the separatory funnel respectively, drop them into the 1000ml beaker containing 200ml potassium hydrogen phthalate buffer solution at a constant speed in the way of co-current precipitation, keep the temperature of the water bath at 30°C and keep stirring during the dropping process, The pH value of the precipitation solution is controlled at 4-5 by the buffer solution, and the precipitation time is maintained at 0.5h. After the titration, keep stirring for 5 minutes and then stop stirring. The mother liquor is aged at a constant temperature of 30°C for 2h, then moved to a Buchner funnel and washed with distilled water until the conductivity is lower than 800μs/cm, then filtered and dried at 120°C for 10h , Calcined at 500°C for 5h, and made into 20-40 mesh particles, a catalyst B was obtained. The CuO content of the catalyst was 48.44% and the SiO ₂ content was 48.88% as determined by XRF.

Example 3:

Add 52.94g of Cu(NO ₃ ) ₂ ·3H ₂ O to 337ml of distilled water to make a 0.65mol/L aqueous solution, and add 28.40g of Na ₂ SiO ₃ .9H ₂ O to 154ml of distilled water to make a 0.65mol/L aqueous solution. Move the two solutions to the separatory funnel respectively, drop them into the 1000ml beaker containing 200ml potassium hydrogen phthalate buffer solution at a constant speed in the way of co-current precipitation, keep the temperature of the water bath at 30°C and keep stirring during the dropping process, The pH value of the precipitation solution is controlled at 4-5 by the buffer solution, and the precipitation time is maintained at 0.5h. After the titration, keep stirring for 5 minutes and then stop stirring. The mother liquor is aged at a constant temperature of 30°C for 2h, then moved to a Buchner funnel and washed with distilled water until the conductivity is lower than 800μs/cm, then filtered and dried at 120°C for 10h , Calcined at 500°C for 5h, and made into 20-40 mesh particles, a catalyst C was obtained. The CuO content of the catalyst was 68.45% and the SiO ₂ content was 29.37% as determined by XRF.

Example 4:

Add 54.69g _{CuSO 4} ·5H ₂ O to 337ml distilled water to form a 0.65mol/L aqueous solution, and take another 38.5ml _Li2O ·SiO2 aqueous solution with a density of 1.17ml/g and a SiO ₂ content of 20%. Move the two solutions to a separatory funnel respectively, drop them into a 1000ml beaker containing 200ml of citric acid-sodium citrate buffer solution at a constant speed in the way of co-current precipitation, keep the temperature of the water bath at 30°C during the dropping process and keep stirring, at this time The pH value of the precipitation solution was controlled at 3-4 by the buffer solution, and the titration process was maintained at 1 h. After the titration was completed, the stirring was continued for 5 minutes and then the stirring was stopped. The mother liquor was aged at a constant temperature of 30°C for 2 hours, then moved to a Buchner funnel and washed with distilled water until the conductivity was lower than 800 μs/cm, then filtered and dried at 150°C for 4 hours , Calcined at 600°C for 4 hours, and made into 20-40 mesh particles to obtain a catalyst D. The catalyst has a CuO content of 67.05% and a SiO ₂ content of 28.52% as determined by XRF.

Example 5:

Add 31.25g Cu(CH ₃ COO) ₂ ·H ₂ O to 240ml distilled water to form a 0.65mol/L aqueous solution, and take another 117.3ml K ₂ O·SiO ₂ aqueous solution with a density of 1.44ml/g and a SiO ₂ content of 15.5%. Transfer the two solutions to a separatory funnel respectively, and drop them into a 1000ml beaker filled with 200ml acetic acid-sodium acetate buffer solution at a constant speed in the way of co-current precipitation. The pH value of the solution was controlled at 5-6 by the buffer solution, and the titration process was maintained at 0.65h. After the titration, keep stirring for 5 minutes and then stop stirring. The mother liquor is aged at a constant temperature of 30°C for 2h, then moved to a Buchner funnel, washed with distilled water until the conductivity is lower than 800μs/cm, then filtered and dried at 150°C for 2h , Calcined at 600°C for 5h, and made into 20-40 mesh particles to obtain a catalyst E, whose CuO content was 47.95% and SiO ₂ content was 49.22% as determined by XRF.

Comparative Example 1:

Weigh Cu(NO ₃ ) ₂ 3H ₂ O 36.46g, Zn(NO ₃ ) ₂ 6H ₂ O2 1.93g and Al(NO ₃ ) ₃ 9H ₂ O 14.72g, and dissolve them in 241.4ml of distilled water. Using a 2mol/L Na ₂ CO ₃ solution as a precipitating agent, the pH of the solution was adjusted to 7 at a temperature of 70° C. using a co-current method. After the precipitation was completed, the mother liquor was aged at 70° C. for 4 h, then filtered and the precipitate was washed several times with distilled water until the conductivity of the precipitate solution was 20 μs/cm. Transfer the filter cake obtained by filtration into an oven to dry at 120°C for 10 hours, and then transfer it to a muffle furnace for roasting at 500°C for 5 hours. The calcined catalyst powder needs to be tabletted, crushed, and sieved to make 20-40 mesh particles , to obtain a catalyst F, which was determined by XRF to have a CuO content of 59.64%, a ZnO content of 28.77%, and an Al ₂ O ₃ content of 10.55%.

Comparative example 2:

Prepare 45.38g of Cu(NO ₃ ) ₂ ·3H ₂ O with 289ml of distilled water to form a 0.65mol/L aqueous solution, then add 38ml of ammonia water to make it a copper-ammonia complex solution, and the pH of the solution is about 11. On the other hand, take 25ml of silica sol, move the silica sol to the separatory funnel, and add it dropwise to the prepared copper ammonia complex solution at an even speed. During the dropping process, a constant temperature water bath is used to maintain the system at 30 °C, with constant stirring. After the titration is over, stop stirring, and age at a constant temperature of 70°C for 1 hour. After the aging, the temperature of the water bath is raised to 90°C to distill ammonia until the pH of the solution drops to about 6.5, then transfer to a Buchner funnel, wash with distilled water, filter, and dry at 150°C. 4 hours, 500 ℃ roasting 5 hours, made into 20-40 mesh particles, that is a catalyst G, the catalyst by XRF measurement of CuO content of 55.46%, SiO ₂ content of 43.12%.

Comparative example 3:

45.38g Cu(NO ₃ ) ₂ ·3H ₂ O was prepared into a 0.65mol/L aqueous solution with 289ml of distilled water, and 19.88g of Na ₂ CO ₃ was also prepared into a 0.65mol/L aqueous solution with 289ml of distilled water. Put the prepared Na ₂ CO ₃ aqueous solution and Cu(NO ₃ ) ₂ ·3H ₂ O solution into the separatory funnel respectively, and drop them into the beaker with 25ml of silica sol at a constant speed in the way of co-current precipitation. The water bath was kept at a constant temperature of 30°C with constant stirring. After the titration, stop stirring, age at 30°C for 2 hours, then move to a Buchner funnel, wash with distilled water, filter, dry at 120°C for 8 hours, and roast at 400°C for 6 hours to make 20-40 mesh particles to obtain a catalyst H, the catalyst has a CuO content of 60.67% and _a SiO content of 39.12% as determined by XRF.

Catalyst activity evaluation method: the catalyst sample in the embodiment and the comparative example is evaluated its reactivity with miniature fixed-bed reactor (stainless steel reaction tube inner diameter 14mm, long 34mm); Experimental catalyst consumption is 1.14g, and reaction temperature is placed on The thermocouple of the catalyst bed is detected, and the entire heating furnace is controlled by the PID temperature control table. Before the reaction, the catalyst needs to be reduced by mixed gas (5%H ₂ -95%N ₂ ) at 270°C for 4 hours. The pressure in the reduction stage is maintained at 0.2MP through the back pressure valve. After the reaction temperature, remove the pressure in the reactor, and use a high-pressure liquid phase pump to inject sec-butanol into the reaction tube under normal pressure to start the reaction. The reaction product was condensed in the gas-liquid separation tube and taken out for testing. Experimental reaction temperature: 240°C; reaction pressure: normal pressure; reaction space velocity (using mass space velocity WHSV): 17.5h ^-1 .

Table 1 is a comparison table of the activity evaluation of the catalyst samples obtained in Examples 1-5 and Comparative Examples 1-3, which were reduced at a temperature of 270°C and reacted at a temperature of 240°C. Wherein the catalyst samples obtained in Examples 1-5 are catalysts A, B, C, D, E respectively; the catalyst samples obtained in Comparative Examples 1-3 are catalysts F, G, H respectively.

Table 1 Embodiment 1～5 and comparative example 1～3 catalyst activity evaluation comparison table

catalyst S-butanol conversion/% Methyl ethyl ketone selectivity/% A 86.6 96.3 B 80.8 97.5 C 88.1 97.1 D. 90.4 95.6 E. 87.1 98.5 f 75.7 90.8 G 84.2 92.4 h 84.8 93.1

In order to show that the Cu- _SiO2 catalyst in the present invention is different from the Cu-Zn-Al and Cu- _SiO2 catalysts prepared by the traditional co-precipitation method in thermal stability, the catalysts A, F, G and H were treated at 390 ° C Reduction at a high temperature and the activity evaluation of the reaction at a temperature of 240 ° C are compared to observe the thermal stability of the catalyst after high temperature treatment.

Table 2 Catalysts of Example 1 and Comparative Examples 1 to 3 Catalysts after high temperature treatment Activity evaluation comparison table

catalyst S-butanol conversion/% Methyl ethyl ketone selectivity/% A 86.1 95.6 f 68.9 93.9 G 80.2 90.7 h 77.3 91.2

As can be seen from the data in Table 1, the Cu- _SiO2 catalyst of the present invention is compared with the Cu-Zn-Al and Cu- _SiO2 catalysts prepared by the traditional co-precipitation method, not only has high sec-butanol dehydrogenation activity, but also has obvious methyl ethyl ketone selectivity higher than other methods.

It can be seen from the data in Table 2 that after the Cu-SiO ₂ catalyst of the present invention is treated at a high temperature of 390°C, the conversion rate of sec-butanol and the selectivity of methyl ethyl ketone are only slightly decreased, and it has excellent thermal stability. However, the catalytic activity of the Cu-Zn-Al catalyst and Cu- _SiO2 catalyst prepared by the traditional co-precipitation method decreased significantly after being reduced at a high temperature of 390 °C.

Accompanying drawing 1 is the high-resolution TEM result of the Cu-SiO ₂ prepared in Example 1 after being treated at a high temperature of 390°C. It can be seen from the TEM pictures that the active center Cu particles (dark part) of the catalyst are still highly uniformly dispersed even after being treated at a high temperature of 390°C, without obvious aggregation and sintering. The analysis of the microstructure further shows that the Cu particles of the present invention -SiO ₂ has excellent thermal stability.

The above experimental results show that the Cu- _SiO2 catalyst developed by the present invention is compared with the Cu-Zn-Al catalyst prepared by the traditional co-precipitation method and the Cu- _SiO2 catalyst, not only has a higher sec-butanol dehydrogenation reaction Butanol conversion and methyl ethyl ketone selectivity, but also has excellent thermal stability.

The medicaments used in the examples of the present invention are all commercially available.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. A catalyst for the dehydrogenation of sec-butanol, characterized in that: it uses CuO and _SiO as active components, and its components and proportioning are as follows by mass percentage: CuO 50~70%, SiO ₃₀ ~ 50%. 2. a preparation method for the catalyst of sec-butanol dehydrogenation according to claim 1, is characterized in that: comprise the following steps: Step a, dissolving the soluble copper salt into a certain concentration solution with distilled water, and calculating the corresponding amount of soluble silicate according to the mass percentage specified by the catalyst, and disposing it into a solution with the same concentration as the copper salt solution; Step b. Fully mix the two solutions in a water bath at a constant temperature of 30°C under stirring, and use a buffer solution to control the pH value of the solution during precipitation at 3~7, and maintain the mixing process at 0.5~1h; Step c, after stopping the stirring, aging, washing with distilled water, filtering, drying, roasting and tableting to obtain the finished catalyst. 3. the preparation method of methyl ethyl ketone catalyst by sec-butanol dehydrogenation according to claim 2, is characterized in that: the concentration of described soluble copper salt and soluble silicate solution is 0.5～1.0mol/L; The molar ratio of salt to soluble silicate is 0.95~2.20. 4. The preparation method of the catalyst for preparing methyl ethyl ketone by sec-butanol dehydrogenation according to claim 2 or 3, characterized in that: the soluble silicate is sodium silicate, potassium silicate or lithium silicate. 5. according to the preparation method of the described sec-butanol dehydrogenation methyl ethyl ketone catalyst described in claim 2 or 3, it is characterized in that: described soluble copper salt is one or more of nitrate, sulfate, acetate of copper mixture of species. 6. The preparation method of the catalyst for producing methyl ethyl ketone by sec-butanol dehydrogenation according to claim 2, characterized in that: the buffer solution is acetic acid-sodium acetate, citric acid-sodium citrate or potassium hydrogen phthalate. 7. the preparation method of methyl ethyl ketone catalyst by sec-butanol dehydrogenation according to claim 2, is characterized in that: described aging condition is: aging temperature is 30～70 ℃, aging time is 1～3h, The pH value is 4~6. 8. The preparation method of the catalyst for preparing methyl ethyl ketone by sec-butanol dehydrogenation according to claim 2, characterized in that: the drying conditions are: the drying temperature is 120~150°C, and the drying time is 2~4h. 9. The preparation method of the catalyst for producing methyl ethyl ketone by sec-butanol dehydrogenation according to claim 2, characterized in that: the calcination conditions are: the calcination temperature is 400-600°C, and the calcination time is 4-6h. 10. The preparation method of the catalyst for producing methyl ethyl ketone by dehydrogenation of sec-butanol according to claim 2, characterized in that: the washing and filtering conditions are: the conductivity of the final precipitation mother liquor is less than 800 μs/cm.