CN118304903A - Modified propane dehydrogenation catalyst and preparation method thereof - Google Patents

Abstract

The invention provides a modified propane dehydrogenation catalyst and a preparation method thereof, and belongs to the technical field of propane dehydrogenation catalysts. Carboxylation is carried out on the surface of the multiwall carbon nanotube, aluminum oxide and zinc oxide are coated, moS ₂ is deposited, the obtained product is immersed in impregnating solution containing lanthanum nitrate, cobalt nitrate and nickel chloride, the solvent is volatilized, and the modified propane dehydrogenation catalyst is obtained after calcination. The modified propane dehydrogenation catalyst prepared by the invention has larger specific surface area, better propane selectivity and catalytic activity, high propylene yield, low reaction temperature, reduced carbon deposition, improved carbon deposition resistance, favorable catalytic activity and service life of the catalyst, no need of adding noble metal, low cost and wide application prospect.

Description

A modified propane dehydrogenation catalyst and preparation method thereof

Technical Field

The invention relates to the technical field of propane dehydrogenation catalysts, and in particular to a modified propane dehydrogenation catalyst and a preparation method thereof.

Background technique

Propylene is the basic raw material of petrochemical industry, mainly used to produce polypropylene, acrylonitrile, acetone, propylene oxide, acrylic acid and 1,2-butylene glycol. Half of the supply of propylene comes from refinery by-products, and about 45% comes from steam cracking, with a small amount of other alternative technologies. In recent years, the demand for propylene has increased year by year. Traditional propylene production can no longer meet the demand for propylene in the chemical industry, so increasing the production of propylene has become a major research hotspot. Among them, propane dehydrogenation to propylene is a major technology for increasing propylene production. For more than 10 years, propane dehydrogenation to propylene has become an important process for industrial propylene production.

The process of producing propylene by dehydrogenation of propane has been industrialized for more than 20 years, and there have been many studies on dehydrogenation catalysts. However, the current catalysts still have defects such as low propane conversion rate and easy deactivation, which need to be further improved and perfected. Therefore, it is of practical significance to develop propane dehydrogenation catalysts with excellent performance.

Summary of the invention

The purpose of the present invention is to provide a modified propane dehydrogenation catalyst and a preparation method thereof, which has a large specific surface area, not only has good propane selectivity and catalytic activity, high propylene yield, but also can reduce the reaction temperature to a certain extent and reduce the generation of carbon deposition. At the same time, the prepared catalyst structure can change the acid distribution on the surface of the carrier, enhance its anti-carbon deposition ability, which is beneficial to improve the catalytic activity and service life of the catalyst dehydrogenation, and has broad application prospects.

The technical solution of the present invention is achieved in this way:

The present invention provides a method for preparing a modified propane dehydrogenation catalyst. The surface of multi-walled carbon nanotubes is carboxylated, coated with aluminum oxide and zinc oxide, and then _MoS2 is deposited. The obtained product is immersed in an impregnation solution containing lanthanum nitrate, cobalt nitrate and nickel chloride, the solvent is evaporated, and calcined to obtain a modified propane dehydrogenation catalyst.

As a further improvement of the present invention, the following steps are included:

S1. Preparation of carboxylated carbon nanotubes: Mix multi-walled carbon nanotubes, concentrated sulfuric acid and concentrated hydrochloric acid, heat and ultrasonically stir to react, dilute with water, centrifuge, wash, adjust pH, dry, heat and extract with tetrahydrofuran, and dry to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: dispersing the carboxylated carbon nanotubes obtained in step S1 in water, adding aluminum salt and zinc salt, stirring and mixing, adding a complexing agent, heating and stirring to form a sol, calcining, and ball milling to obtain bimetallic oxide-coated carbon nanotubes;

S3. Preparation of _MoS2- deposited bimetallic coated carbon nanotubes: dissolve molybdate in water, add bimetallic oxide-coated carbon nanotubes and thiourea obtained in step S3, stir and mix evenly, heat to react, and obtain MoS2 _- deposited bimetallic oxide-coated carbon nanotubes;

S4. Preparation of an impregnation solution: dissolving lanthanum nitrate, cobalt nitrate and nickel chloride in water to prepare an impregnation solution;

S5. Preparation of modified propane dehydrogenation catalyst: adding the MoS ₂ deposited bimetallic oxide-coated carbon nanotubes obtained in step S3 to the impregnation solution obtained in step S4, heating to evaporate the solvent, and calcining to obtain a modified propane dehydrogenation catalyst.

As a further improvement of the present invention, the mass ratio of the multi-walled carbon nanotubes, concentrated sulfuric acid and concentrated hydrochloric acid in step S1 is 1-2:20-30:5-7, the temperature of the heated ultrasonic stirring reaction is 45-50°C, the ultrasonic power is 800-1000W, and the time is 3-5h; the pH is adjusted to 5-6, and the temperature of the tetrahydrofuran heating extraction is 60-70°C, and the time is 12-15h.

As a further improvement of the present invention, the mass ratio of the carboxylated carbon nanotubes, aluminum salt, zinc salt and complexing agent in step S2 is 15-20:5-7:3-5:12-15, the aluminum salt is selected from at least one of aluminum chloride, aluminum sulfate and aluminum nitrate, the zinc salt is selected from at least one of zinc chloride, zinc sulfate and zinc nitrate, the complexing agent is selected from at least one of citric acid, sodium citrate and potassium citrate, the heating temperature is 65-75°C, the calcination temperature is 550-600°C, the time is 2-4h, and the ball milling time is 1-3h.

As a further improvement of the present invention, the molybdate in step S3 is selected from at least one of sodium molybdate, potassium molybdate and ammonium molybdate, the mass ratio of the molybdate, the bimetallic oxide-coated carbon nanotubes and thiourea is 3-5:17-22:5-10, the temperature of the heating reaction is 200-220°C, and the time is 15-20h.

As a further improvement of the present invention, the mass ratio of lanthanum nitrate, cobalt nitrate, nickel chloride and water in step S4 is 3-5:2-4:12-17:200.

As a further improvement of the present invention, in step S5, the mass ratio of the _MoS2 deposited bimetallic oxide-coated carbon nanotubes to the impregnation solution is 15-20:50-70, the heating temperature is 70-80°C, the calcination temperature is 600-700°C, and the time is 2-4h.

As a further improvement of the present invention, the present invention specifically comprises the following steps:

S1. Preparation of carboxylated carbon nanotubes: 1-2 parts by weight of multi-walled carbon nanotubes, 20-30 parts by weight of concentrated sulfuric acid, and 5-7 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 45-50 ° C, 800-1000W ultrasonic stirring reaction for 3-5h, diluted with water, centrifuged, washed, adjusted to pH 5-6, dried, tetrahydrofuran heated to 60-70 ° C, extracted for 12-15h, dried, to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: 15-20 parts by weight of the carboxylated carbon nanotubes obtained in step S1 are dispersed in 100 parts by weight of water, 5-7 parts by weight of aluminum salt and 3-5 parts by weight of zinc salt are added, stirred and mixed evenly, 12-15 parts by weight of a complexing agent are added, heated to 65-75°C, stirred to form a sol, calcined at 550-600°C for 2-4h, ball milled for 1-3h, and bimetallic oxide-coated carbon nanotubes are obtained;

S3. Preparation of _MoS2 -deposited bimetallic coated carbon nanotubes: dissolve 3-5 parts by weight of molybdate in 100 parts by weight of water, add 17-22 parts by weight of bimetallic oxide-coated carbon nanotubes prepared in step S3 and 5-10 parts by weight of thiourea, stir and mix evenly, transfer to a Teflon-lined reactor, heat to 200-220°C, stir and react for 15-20 hours, and prepare MoS2 _- deposited bimetallic oxide-coated carbon nanotubes;

S4. Preparation of an impregnation solution: 3-5 parts by weight of lanthanum nitrate, 2-4 parts by weight of cobalt nitrate, 12-17 parts by weight of nickel chloride are dissolved in 200 parts by weight of water to prepare an impregnation solution;

S5. Preparation of modified propane dehydrogenation catalyst: Add 15-20 parts by weight of _MoS2 deposited bimetallic oxide-coated carbon nanotubes prepared in step S3 to 50-70 parts by weight of the impregnation solution prepared in step S4, heat to 70-80°C, evaporate the solvent, and calcine at 600-700°C for 2-4h to prepare a modified propane dehydrogenation catalyst.

The present invention further protects a modified propane dehydrogenation catalyst prepared by the above preparation method.

The present invention further protects the use of the modified propane dehydrogenation catalyst in the reaction of preparing propylene by dehydrogenating propane.

The present invention has the following beneficial effects:

Multi-walled carbon nanotubes have a large specific surface area, provide abundant sites for reaction, and have good mechanical properties. However, due to their high chemical inertness, they are not conducive to the surface deposition of active catalysts. Therefore, the present invention performs carboxyl modification on the multi-walled carbon nanotubes, and the surface has abundant carboxyl groups, which is conducive to the deposition of zinc oxide and aluminum oxide metals. It has the advantages of large specific surface area of active aluminum oxide, appropriate surface acidity and alkalinity, high thermal stability, etc. At the same time, the mixing of zinc oxide significantly improves the initial activity and stability of the catalyst, and has a significant effect on improving the selectivity of propylene.

Furthermore, the present invention deposits _MoS2 on the surface of the prepared bimetallic oxide-coated carbon nanotubes. The _MoS2 nanomaterial has a layered structure, a large specific surface area, good adsorption performance, and sufficient reaction active sites, thereby having good catalytic activity. At the same time, due to the introduction of the S element, the catalyst's selectivity for propylene can be improved, the reaction temperature of the reaction can be reduced, and the generation of carbon deposits can be reduced from the source, which greatly improves the catalytic service life of the catalyst and is more suitable for industrial applications.

Then, the prepared product is immersed in an impregnation solution containing lanthanum nitrate, cobalt nitrate and nickel chloride. In the active component Ni, five metal atoms of La, Co, Mo, Ni, Zn and Al are further doped, and strong interactions are formed between the metal atoms and oxygen atoms, such as forming an Al-O-Zn structure, which can not only improve the thermal stability of the crystal structure, but also promote better dispersion of the catalytic active components, thereby improving the thermal stability of the catalyst.

At the same time, after La and Co-doped Ni oxides were loaded on the surface of activated alumina/zinc oxide, the acidic sites on the surface of alumina were modified, and the strong Lewis acid centers were transformed into weak acid centers, that is, the acid distribution on the surface of the carrier was changed, and its anti-carbon deposition ability was enhanced, which was beneficial to improve the catalytic activity and service life of the catalyst for dehydrogenation.

Therefore, the modified propane dehydrogenation catalyst prepared by the present invention has a large specific surface area, not only has good propane selectivity and catalytic activity, high propylene yield, but also can reduce the reaction temperature to a certain extent and reduce the generation of carbon deposition. At the same time, the prepared catalyst structure can change the acid distribution on the surface of the carrier, enhance its anti-carbon deposition ability, and is beneficial to improve the catalytic activity and service life of the catalyst dehydrogenation. No precious metals need to be added, the cost is low, and the catalyst has broad application prospects.

Detailed ways

The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Multi-walled carbon nanotubes, industrial grade, were purchased from Suzhou Tanfeng Graphene Technology Co., Ltd.

Example 1

This embodiment provides a method for preparing a modified propane dehydrogenation catalyst, which specifically comprises the following steps:

S1. Preparation of carboxylated carbon nanotubes: 1 part by weight of multi-walled carbon nanotubes, 20 parts by weight of concentrated sulfuric acid, and 5 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 45°C, and reacted with 800W ultrasonic stirring for 3h, diluted with water, centrifuged, washed, adjusted to pH 5, dried, added to 50 parts by weight of tetrahydrofuran, heated to 60°C, extracted for 12h, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: 15 parts by weight of the carboxylated carbon nanotubes prepared in step S1 were dispersed in 100 parts by weight of water, 5 parts by weight of aluminum chloride and 3 parts by weight of zinc chloride were added, and the mixture was stirred for 20 min, 12 parts by weight of citric acid was added, and the mixture was heated to 65° C. and stirred to form a sol, and the mixture was calcined at 550° C. for 2 h, and ball-milled for 1 h to obtain bimetallic oxide-coated carbon nanotubes;

S3. Preparation of _MoS2 -deposited bimetallic coated carbon nanotubes: Dissolve 3 parts by weight of sodium molybdate in 100 parts by weight of water, add 17 parts by weight of bimetallic oxide-coated carbon nanotubes prepared in step S3 and 5 parts by weight of thiourea, stir and mix for 20 minutes, transfer to a Teflon-lined reactor, heat to 200°C, stir and react for 20 hours to obtain MoS2 _- deposited bimetallic oxide-coated carbon nanotubes;

S4. Preparation of an impregnation solution: 3 parts by weight of lanthanum nitrate, 2 parts by weight of cobalt nitrate, and 12 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to prepare an impregnation solution;

S5. Preparation of modified propane dehydrogenation catalyst: 15 parts by weight of _MoS2 deposited bimetallic oxide-coated carbon nanotubes prepared in step S3 were added to 50 parts by weight of the impregnation solution prepared in step S4, heated to 70°C, evaporated the solvent, and calcined at 600°C for 2h to obtain a modified propane dehydrogenation catalyst.

Example 2

This embodiment provides a method for preparing a modified propane dehydrogenation catalyst, which specifically comprises the following steps:

S1. Preparation of carboxylated carbon nanotubes: 2 parts by weight of multi-walled carbon nanotubes, 30 parts by weight of concentrated sulfuric acid, and 7 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 50°C, and reacted with 1000W ultrasonic stirring for 5h, diluted with water, centrifuged, washed, adjusted to pH 6, dried, added to 50 parts by weight of tetrahydrofuran, heated to 70°C, extracted for 15h, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: 20 parts by weight of the carboxylated carbon nanotubes prepared in step S1 were dispersed in 100 parts by weight of water, 7 parts by weight of aluminum sulfate and 5 parts by weight of zinc sulfate were added, and the mixture was stirred for 20 minutes. 15 parts by weight of sodium citrate was added, and the mixture was heated to 75° C. and stirred to form a sol. The mixture was calcined at 600° C. for 4 hours and ball-milled for 3 hours to obtain bimetallic oxide-coated carbon nanotubes.

S3. Preparation of _MoS2 -deposited bimetallic-coated carbon nanotubes: Dissolve 5 parts by weight of ammonium molybdate in 100 parts by weight of water, add 22 parts by weight of bimetallic oxide-coated carbon nanotubes prepared in step S3 and 10 parts by weight of thiourea, stir and mix for 20 minutes, transfer to a Teflon-lined reactor, heat to 220°C, stir and react for 20 hours, and prepare MoS2 _- deposited bimetallic oxide-coated carbon nanotubes;

S4. Preparation of an impregnation solution: 5 parts by weight of lanthanum nitrate, 4 parts by weight of cobalt nitrate, and 17 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to form an impregnation solution;

S5. Preparation of modified propane dehydrogenation catalyst: 20 parts by weight of _MoS2 deposited bimetallic oxide-coated carbon nanotubes prepared in step S3 were added to 70 parts by weight of the impregnation solution prepared in step S4, heated to 80°C, evaporated the solvent, and calcined at 700°C for 4h to obtain a modified propane dehydrogenation catalyst.

Example 3

This embodiment provides a method for preparing a modified propane dehydrogenation catalyst, which specifically comprises the following steps:

S1. Preparation of carboxylated carbon nanotubes: 1.5 parts by weight of multi-walled carbon nanotubes, 25 parts by weight of concentrated sulfuric acid, and 6 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 47 ° C, and reacted with ultrasonic stirring at 900W for 4 hours, diluted with water, centrifuged, washed, adjusted to pH 5.5, dried, added to 50 parts by weight of tetrahydrofuran, heated to 65 ° C, extracted for 13 hours, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: 17 parts by weight of the carboxylated carbon nanotubes prepared in step S1 were dispersed in 100 parts by weight of water, 6 parts by weight of aluminum nitrate and 4 parts by weight of zinc nitrate were added, and the mixture was stirred for 20 minutes, 13 parts by weight of citric acid was added, and the mixture was heated to 70° C. and stirred to form a sol, and the mixture was calcined at 570° C. for 3 hours and ball-milled for 2 hours to obtain bimetallic oxide-coated carbon nanotubes;

S3. Preparation of _MoS2 -deposited bimetallic coated carbon nanotubes: Dissolve 4 parts by weight of potassium molybdate in 100 parts by weight of water, add 20 parts by weight of bimetallic oxide-coated carbon nanotubes prepared in step S3 and 7 parts by weight of thiourea, stir and mix for 20 minutes, transfer to a Teflon-lined reactor, heat to 210°C, stir and react for 17 hours to obtain MoS2 _- deposited bimetallic oxide-coated carbon nanotubes;

S4. Preparation of an impregnation solution: 4 parts by weight of lanthanum nitrate, 3 parts by weight of cobalt nitrate, and 15 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to form an impregnation solution;

S5. Preparation of modified propane dehydrogenation catalyst: 17 parts by weight of _MoS2 deposited bimetallic oxide-coated carbon nanotubes prepared in step S3 were added to 60 parts by weight of the impregnation solution prepared in step S4, heated to 75°C, evaporated the solvent, and calcined at 650°C for 3h to prepare a modified propane dehydrogenation catalyst.

Comparative Example 1

Compared with Example 3, the difference is that step S1 is not performed.

details as follows:

S1. Preparation of bimetallic oxide-coated carbon nanotubes: 17 parts by weight of multi-walled carbon nanotubes were dispersed in 100 parts by weight of water, 6 parts by weight of aluminum nitrate and 4 parts by weight of zinc nitrate were added, and the mixture was stirred for 20 minutes, 13 parts by weight of citric acid were added, and the mixture was heated to 70°C, stirred to form a sol, calcined at 570°C for 3 hours, and ball-milled for 2 hours to obtain bimetallic oxide-coated carbon nanotubes;

S2. Preparation of _MoS2 -deposited bimetallic coated carbon nanotubes: Dissolve 4 parts by weight of potassium molybdate in 100 parts by weight of water, add 20 parts by weight of bimetallic oxide-coated carbon nanotubes prepared in step S2 and 7 parts by weight of thiourea, stir and mix for 20 minutes, transfer to a Teflon-lined reactor, heat to 210°C, stir and react for 17 hours to obtain MoS2 _- deposited bimetallic oxide-coated carbon nanotubes;

S3. Preparation of an impregnation solution: 4 parts by weight of lanthanum nitrate, 3 parts by weight of cobalt nitrate, and 15 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to prepare an impregnation solution;

S4. Preparation of modified propane dehydrogenation catalyst: 17 parts by weight of _MoS2 deposited bimetallic oxide-coated carbon nanotubes prepared in step S2 were added to 60 parts by weight of the impregnation solution prepared in step S3, heated to 75°C, evaporated the solvent, and calcined at 650°C for 3h to obtain a modified propane dehydrogenation catalyst.

Comparative Example 2

Compared with Example 3, the difference is that aluminum nitrate is not added in step S2.

details as follows:

S2. Preparation of metal oxide-coated carbon nanotubes: Disperse 17 parts by weight of the carboxylated carbon nanotubes obtained in step S1 in 100 parts by weight of water, add 10 parts by weight of zinc nitrate, stir and mix for 20 minutes, add 13 parts by weight of citric acid, heat to 70°C, stir to form a sol, calcine at 570°C for 3 hours, and ball mill for 2 hours to obtain metal oxide-coated carbon nanotubes.

Comparative Example 3

Compared with Example 3, the difference is that zinc nitrate is not added in step S2.

details as follows:

S2. Preparation of metal oxide-coated carbon nanotubes: Disperse 17 parts by weight of the carboxylated carbon nanotubes obtained in step S1 in 100 parts by weight of water, add 10 parts by weight of aluminum nitrate, stir and mix for 20 minutes, add 13 parts by weight of citric acid, heat to 70°C, stir to form a sol, calcine at 570°C for 3 hours, and ball mill for 2 hours to obtain metal oxide-coated carbon nanotubes.

Comparative Example 4

Compared with Example 3, the difference is that step S2 is not performed.

details as follows:

S1. Preparation of carboxylated carbon nanotubes: 1.5 parts by weight of multi-walled carbon nanotubes, 25 parts by weight of concentrated sulfuric acid, and 6 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 47 ° C, and reacted with ultrasonic stirring at 900W for 4 hours, diluted with water, centrifuged, washed, adjusted to pH 5.5, dried, added to 50 parts by weight of tetrahydrofuran, heated to 65 ° C, extracted for 13 hours, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of _MoS2 deposited carbon nanotubes: Dissolve 4 parts by weight of potassium molybdate in 100 parts by weight of water, add 20 parts by weight of carboxylated carbon nanotubes prepared in step S1 and 7 parts by weight of thiourea, stir and mix for 20 minutes, transfer to a Teflon-lined reactor, heat to 210°C, stir and react for 17 hours to obtain _MoS2 deposited carbon nanotubes;

S3. Preparation of an impregnation solution: 4 parts by weight of lanthanum nitrate, 3 parts by weight of cobalt nitrate, and 15 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to prepare an impregnation solution;

S4. Preparation of modified propane dehydrogenation catalyst: 17 parts by weight of MoS ₂ deposited carbon nanotubes prepared in step S2 were added to 60 parts by weight of the impregnation solution prepared in step S3, heated to 75°C, evaporated the solvent, and calcined at 650°C for 3h to prepare a modified propane dehydrogenation catalyst.

Comparative Example 5

Compared with Example 3, the difference is that step S3 is not performed.

details as follows:

S1. Preparation of carboxylated carbon nanotubes: 1.5 parts by weight of multi-walled carbon nanotubes, 25 parts by weight of concentrated sulfuric acid, and 6 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 47 ° C, and reacted with ultrasonic stirring at 900W for 4 hours, diluted with water, centrifuged, washed, adjusted to pH 5.5, dried, added to 50 parts by weight of tetrahydrofuran, heated to 65 ° C, extracted for 13 hours, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: 17 parts by weight of the carboxylated carbon nanotubes prepared in step S1 were dispersed in 100 parts by weight of water, 6 parts by weight of aluminum nitrate and 4 parts by weight of zinc nitrate were added, and the mixture was stirred for 20 minutes, 13 parts by weight of citric acid was added, and the mixture was heated to 70° C. and stirred to form a sol, and the mixture was calcined at 570° C. for 3 hours and ball-milled for 2 hours to obtain bimetallic oxide-coated carbon nanotubes;

S3. Preparation of an impregnation solution: 4 parts by weight of lanthanum nitrate, 3 parts by weight of cobalt nitrate, and 15 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to prepare an impregnation solution;

S4. Preparation of modified propane dehydrogenation catalyst: 17 parts by weight of the bimetallic oxide-coated carbon nanotubes prepared in step S2 were added to 60 parts by weight of the impregnation solution prepared in step S3, heated to 75°C, evaporated the solvent, and calcined at 650°C for 3h to obtain a modified propane dehydrogenation catalyst.

Comparative Example 6

Compared with Example 3, the difference is that lanthanum nitrate is not added in step S4.

details as follows:

S4. Preparation of an impregnation solution: 7 parts by weight of cobalt nitrate and 15 parts by weight of nickel chloride are dissolved in 200 parts by weight of water to prepare an impregnation solution.

Comparative Example 7

Compared with Example 3, the difference is that cobalt nitrate is not added in step S4.

details as follows:

S4. Preparation of an impregnation solution: 7 parts by weight of lanthanum nitrate and 15 parts by weight of nickel chloride are dissolved in 200 parts by weight of water to prepare an impregnation solution.

Comparative Example 8

Compared with Example 3, the difference is that lanthanum nitrate and cobalt nitrate are not added in step S4.

details as follows:

S4. Preparation of an impregnation solution: 22 parts by weight of nickel chloride are dissolved in 200 parts by weight of water to prepare an impregnation solution.

Comparative Example 9

Compared with Example 3, the difference is that steps S4 and S5 are not performed.

details as follows:

S1. Preparation of carboxylated carbon nanotubes: 1.5 parts by weight of multi-walled carbon nanotubes, 25 parts by weight of concentrated sulfuric acid, and 6 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 47 ° C, and reacted with ultrasonic stirring at 900W for 4 hours, diluted with water, centrifuged, washed, adjusted to pH 5.5, dried, added to 50 parts by weight of tetrahydrofuran, heated to 65 ° C, extracted for 13 hours, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of bimetallic oxide-coated carbon nanotubes: 17 parts by weight of the carboxylated carbon nanotubes prepared in step S1 were dispersed in 100 parts by weight of water, 6 parts by weight of aluminum nitrate and 4 parts by weight of zinc nitrate were added, and the mixture was stirred for 20 minutes, 13 parts by weight of citric acid was added, and the mixture was heated to 70° C. and stirred to form a sol, and the mixture was calcined at 570° C. for 3 hours and ball-milled for 2 hours to obtain bimetallic oxide-coated carbon nanotubes;

S3. Preparation of _MoS2 -deposited bimetallic-coated carbon nanotubes: Dissolve 4 parts by weight of potassium molybdate in 100 parts by weight of water, add 20 parts by weight of bimetallic oxide-coated carbon nanotubes prepared in step S3 and 7 parts by weight of thiourea, stir and mix for 20 minutes, transfer to a Teflon-lined reactor, heat to 210°C, stir and react for 17 hours to obtain MoS2 _- deposited bimetallic oxide-coated carbon nanotubes, which are modified propane dehydrogenation catalysts.

Comparative Example 10

Compared with Example 3, the difference is that S2 and S3 are not performed.

details as follows:

S1. Preparation of carboxylated carbon nanotubes: 1.5 parts by weight of multi-walled carbon nanotubes, 25 parts by weight of concentrated sulfuric acid, and 6 parts by weight of concentrated hydrochloric acid were mixed uniformly, heated to 47 ° C, and reacted with ultrasonic stirring at 900W for 4 hours, diluted with water, centrifuged, washed, adjusted to pH 5.5, dried, added to 50 parts by weight of tetrahydrofuran, heated to 65 ° C, extracted for 13 hours, and dried to obtain carboxylated carbon nanotubes;

S2. Preparation of an impregnation solution: 4 parts by weight of lanthanum nitrate, 3 parts by weight of cobalt nitrate, and 15 parts by weight of nickel chloride were dissolved in 200 parts by weight of water to form an impregnation solution;

S3. Preparation of modified propane dehydrogenation catalyst: 17 parts by weight of the carboxylated carbon nanotubes prepared in step S1 were added to 60 parts by weight of the impregnation solution prepared in step S2, heated to 75°C, evaporated the solvent, and calcined at 650°C for 3h to obtain a modified propane dehydrogenation catalyst.

Test Example 1

The specific surface area, pore volume and other parameters of the modified propane dehydrogenation catalysts prepared in Examples 1-3 and Comparative Examples 1-10 were measured using an ASAP2460 fully automatic specific surface and porosity analyzer produced by American Minion Instruments. The results are shown in Table 1.

The crushing strength of the particles was measured using a ZQJ-Ⅱ intelligent particle strength testing machine. The number of samples tested was 50, and the results were averaged.

Table 1

It can be seen from the above table that the modified propane dehydrogenation catalysts prepared in Examples 1-3 of the present invention have a larger specific surface area, a larger total pore volume, a suitable average pore diameter, and a large average strength.

Test Example 2

A method for preparing propylene by dehydrogenating propane, wherein a mixed reaction gas of propane, hydrogen and nitrogen in a volume ratio of 9:9:50 is introduced into a fixed bed reactor loaded with 0.5 g of the modified propane dehydrogenation catalyst prepared in Example 1-3 or Comparative Example 1-10, and heated to 550° C. for reaction for 5 h at a reaction space velocity of 1000 h ^-1 under normal pressure to obtain a product. The results of propane conversion, propane selectivity and propylene yield are shown in Table 2.

Table 2

It can be seen from the above table that the modified propane dehydrogenation catalysts prepared in Examples 1-3 of the present invention have high selectivity for propane, high propane conversion rate, and high propylene yield.

Test Example 3

After the modified propane dehydrogenation catalysts prepared in Examples 1-5 of the present invention or Comparative Examples 1-10 were subjected to continuous catalytic reaction at 700° C. for 200 hours, the specific surface areas before and after the catalysts were measured. The results are shown in Table 3.

table 3

As can be seen from the above table, the modified propane dehydrogenation catalysts prepared in Examples 1-3 of the present invention have similar specific surface areas after continuous catalytic reaction at a reaction temperature of 700° C. for 200 h, indicating that almost no carbon deposits are generated and the catalytic effect is good.

Compared with Example 3, Comparative Example 1 does not perform step S1. The specific surface area and total pore volume decrease, the average pore size increases, the average strength decreases, the selectivity and conversion rate of propane decrease, the yield of propylene decreases, and the carbon deposition increases. Multi-walled carbon nanotubes have a large specific surface area, provide abundant sites for the reaction, and have good mechanical properties, but due to their high chemical inertness, they are not conducive to the surface deposition of active catalysts. Therefore, the present invention performs carboxyl modification on multi-walled carbon nanotubes, and the surface has abundant carboxyl groups, which is conducive to the deposition of zinc oxide and aluminum oxide metals.

Compared with Example 3, in Comparative Examples 2 and 3, aluminum nitrate or zinc nitrate was not added in step S2. Compared with Example 3, step S2 was not performed in Comparative Example 4. The specific surface area and total pore volume decreased, the average pore size increased, the selectivity and conversion rate of propane decreased, and the yield of propylene decreased. The present invention performs carboxylation modification on multi-walled carbon nanotubes and deposits zinc oxide and aluminum oxide metal, which has the advantages of large specific surface area of active alumina, appropriate surface acidity and alkalinity, high thermal stability, etc. At the same time, the mixing of zinc oxide significantly improves the initial activity and stability of the catalyst, and has a significant effect on improving the selectivity of propylene.

Compared with Example 3, Comparative Example 5 does not perform step S3. The specific surface area and total pore volume decrease, the average strength decreases, the selectivity and conversion rate of propane decrease, the yield of propylene decreases, and the carbon deposition increases. The present invention deposits _MoS2 on the surface of the prepared bimetallic oxide-coated carbon nanotubes. The _MoS2 nanomaterial has a layered structure, a large specific surface area, good adsorption performance, and sufficient reactive sites, thereby having good catalytic activity. At the same time, due to the introduction of the S element, the catalyst selectivity for propylene can be improved, the reaction temperature of the reaction can be reduced, and the generation of carbon deposition can be reduced from the source, which greatly improves the catalytic service life of the catalyst and is more suitable for industrial applications.

Compared with Example 3, Comparative Example 10 did not perform S2 and S3. The specific surface area and total pore volume decreased, the average pore diameter increased, the average strength decreased, the selectivity and conversion rate of propane decreased, the yield of propylene decreased, and the carbon deposition increased.

Compared with Example 3, in Comparative Examples 6 and 7, lanthanum nitrate or cobalt nitrate was not added in step S4. Compared with Example 3, in Comparative Example 8, lanthanum nitrate and cobalt nitrate were not added in step S4. Compared with Example 3, in Comparative Example 9, steps S4 and S5 were not performed. The specific surface area and total pore volume decreased, the average pore size increased, the average strength decreased, the selectivity and conversion rate of propane decreased, and the yield of propylene decreased. The present invention immerses the obtained product in an impregnation solution containing lanthanum nitrate, cobalt nitrate and nickel chloride. In the active component Ni, five metal atoms of La, Co, Mo, Ni, Zn and Al are further doped with each other, and a strong interaction is formed between the atoms and oxygen atoms, such as forming an Al-O-Zn structure, which can not only improve the thermal stability of the crystal structure, but also promote better dispersion of the catalytic active components, thereby improving the thermal stability of the catalyst. At the same time, after La and Co-doped Ni oxides were loaded on the surface of activated alumina/zinc oxide, the acidic sites on the surface of alumina were modified, and the strong Lewis acid centers were transformed into weak acid centers, that is, the acid distribution on the surface of the carrier was changed, and its anti-carbon deposition ability was enhanced, which was beneficial to improve the catalytic activity and service life of the catalyst for dehydrogenation.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. The preparation method of the modified propane dehydrogenation catalyst is characterized by comprising the following steps of:

S1, preparing carboxylated carbon nanotubes: uniformly mixing 1-2 parts by weight of multiwall carbon nanotubes, 20-30 parts by weight of concentrated sulfuric acid and 5-7 parts by weight of concentrated hydrochloric acid, heating to 45-50 ℃, performing ultrasonic stirring reaction for 3-5 hours at 800-1000W, adding water for dilution, centrifuging, washing, adjusting pH to 5-6, drying, heating tetrahydrofuran to 60-70 ℃, extracting for 12-15 hours, and drying to obtain carboxylated carbon nanotubes;

s2, preparing a bimetal oxide coated carbon nano tube: dispersing 15-20 parts by weight of carboxylated carbon nanotubes prepared in the step S1 in 100 parts by weight of water, adding 5-7 parts by weight of aluminum salt and 3-5 parts by weight of zinc salt, uniformly stirring and mixing, adding 12-15 parts by weight of complexing agent, heating to 65-75 ℃, stirring to form sol, calcining at 550-600 ℃ for 2-4 hours, and ball-milling for 1-3 hours to prepare the bimetal oxide coated carbon nanotubes;

S3, preparing a bimetal coated carbon nano tube by MoS ₂ deposition: dissolving 3-5 parts by weight of molybdate in 100 parts by weight of water, adding 17-22 parts by weight of the bimetallic oxide coated carbon nano tube prepared in the step S3 and 5-10 parts by weight of thiourea, stirring and mixing uniformly, transferring to a Teflon lining reaction kettle, heating to 200-220 ℃, and stirring and reacting for 15-20 hours to prepare the MoS ₂ deposited bimetallic oxide coated carbon nano tube;

s4, preparing an impregnating solution: 3-5 parts by weight of lanthanum nitrate, 2-4 parts by weight of cobalt nitrate and 12-17 parts by weight of nickel chloride are dissolved in 200 parts by weight of water to prepare an impregnating solution;

S5, preparing a modified propane dehydrogenation catalyst: 15-20 parts by weight of MoS ₂ deposited bimetallic oxide coated carbon nano tube prepared in the step S3 are added into 50-70 parts by weight of the impregnating solution prepared in the step S4, heated to 70-80 ℃, the solvent is volatilized, and calcined for 2-4 hours at 600-700 ℃ to prepare the modified propane dehydrogenation catalyst.

2. The preparation method according to claim 1, wherein the aluminum salt in the step S2 is at least one selected from aluminum chloride, aluminum sulfate and aluminum nitrate, the zinc salt is at least one selected from zinc chloride, zinc sulfate and zinc nitrate, and the complexing agent is at least one selected from citric acid, sodium citrate and potassium citrate.

3. The method according to claim 1, wherein the molybdate in step S3 is at least one selected from the group consisting of sodium molybdate, potassium molybdate and ammonium molybdate.

4. A modified propane dehydrogenation catalyst prepared by the preparation method as claimed in any one of claims 1 to 3.

5. Use of the modified propane dehydrogenation catalyst of claim 4 in a reaction for preparing propylene by dehydrogenation of propane.