阅读说明：本技术 一种低碳烷烃脱氢催化剂及其制备方法 (Low-carbon alkane dehydrogenation catalyst and preparation method thereof ) 是由 赵素英 曹辰辰 刘杰 郑辉东 王屹鸣 刘传亮 于 2019-12-11 设计创作，主要内容包括：本发明提供了一种低碳烷烃脱氢催化剂及其制备方法,所述催化剂由以下质量百分数的组分组成：1.0~10.0wt%的Pt,1.0~5.0wt%的Sn,85.0~98.0wt%的多壁碳纳米管,三者质量百分数之和为100%,其中Pt位于多壁碳纳米管管内,Sn位于多壁碳纳米管管外。该催化剂用于低碳烷烃脱氢反应,具有较好的催化活性及稳定性。(The invention provides a low-carbon alkane dehydrogenation catalyst and a preparation method thereof, wherein the catalyst comprises the following components in percentage by mass: 1.0-10.0 wt% of Pt, 1.0-5.0 wt% of Sn and 85.0-98.0 wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, wherein the Pt is positioned in the multi-walled carbon nano-tube, and the Sn is positioned outside the multi-walled carbon nano-tube. The catalyst is used for dehydrogenation reaction of low-carbon alkane, and has better catalytic activity and stability.)

1. The low-carbon alkane dehydrogenation catalyst is characterized by comprising the following components in percentage by mass: 1.0-10.0 wt% of Pt, 1.0-5.0 wt% of Sn and 85.0-98.0 wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, wherein the Pt is positioned in the multi-walled carbon nano-tube, and the Sn is positioned outside the multi-walled carbon nano-tube.

2. The light alkane dehydrogenation catalyst of claim 1, wherein the catalyst has a pore size of 3.0-12.0 nm and a specific surface area of 104-266 m²(ii) a total pore volume of 0.1 to 0.6cm³/g。

3. A method for preparing the light alkane dehydrogenation catalyst according to claim 1 or 2, comprising the steps of:

(1) concentrated HNO with the concentration of 65-68 wt% is used₃Impregnating the multi-walled carbon nanotube, carrying out oxidation treatment for 2-18 hours, and washing and drying to obtain a multi-walled carbon nanotube carrier;

(2) and (2) sequentially and respectively soaking the multi-wall carbon nano tube carrier in the step (1) by using a platinum-containing compound solution and a tin-containing compound solution, drying for 8-30 h at the temperature of 80-130 ℃ in the air, and then reducing.

4. The method according to claim 3, wherein the platinum-containing compound in step (2) is platinum nitrate, chloroplatinic acid, potassium chloroplatinate, tetraammineplatinum dichloride or platinum acetylacetonate; the solvent of the platinum-containing compound solution is water, methanol, acetone or ethanol.

5. The preparation method according to claim 3, wherein the tin-containing compound in the step (2) is stannic chloride, stannous oxide or nano stannic oxide; the solvent of the tin compound solution is water, methanol, acetone or ethanol.

6. The preparation method according to claim 3, wherein the impregnation with the platinum-containing compound in the step (2) is divided into two steps, wherein the ultrasonic treatment is firstly adopted for 0.3-5.0 h, and then the stirring impregnation is adopted for 0.5-6.0 h; the liquid/solid ratio of the platinum-containing compound solution used for impregnation to the multiwalled carbon nanotube carrier is 10-30 mL/g, the platinum content in the platinum-containing compound solution used for impregnation is 1-8 mg/mL, and the impregnation temperature is 15-45 ℃.

7. The preparation method according to claim 3, wherein the method for impregnating the multi-walled carbon nanotube carrier with the tin compound solution in the step (2) is stirring impregnation, and the stirring time is 5-60 min; the liquid/solid ratio of the tin-containing compound solution used for impregnation to the multiwalled carbon nanotube carrier is 10-30 mL/g, the tin content in the tin-containing compound solution used for impregnation is 2-6 mg/mL, and the impregnation temperature is 70-120 ℃.

8. The method according to claim 3, wherein the reduction in the step (2) is carried out with a reducing agent such as ethylene glycol or C or hydrogen gas₁~C₃Carboxylic acid or C₁~C₃The sodium carboxylate of (1).

9. The preparation method according to claim 8, wherein when the reducing agent is used for reduction in the step (2), the molar ratio of the reducing agent to Pt is 10-20: 1, the reduction temperature is 50-300 ℃.

10. The method according to claim 8, wherein the reduction temperature in the step (2) is 550 to 650 ℃ when hydrogen is used for reduction.

Technical Field

The invention relates to a low-carbon alkane dehydrogenation catalyst, a preparation method and application thereof, in particular to a catalyst taking a carbon nano tube as a carrier, and a preparation method and application thereof.

Background

The Pt-based catalyst is one of the catalysts commonly used for propane dehydrogenation. Propane dehydrogenation is a reversible reaction with strong heat absorption and increased molecular number, the dehydrogenation reaction is favorably carried out at high temperature and low pressure, the common reaction temperature is about 600 ℃, the higher reaction temperature causes the aggravation of propane cracking and propane deep dehydrogenation degree, the selectivity of propylene is reduced, and the aggravation of carbon deposit on the surface of a catalyst can also cause the inactivation of the catalyst.

In recent years, carbon nanotubes have been widely studied as a novel nanocarbon material. The catalytic properties of carbon nanotubes are mainly manifested in their specific architecture and nanoscale dimensions. On one hand, the coiled structure causes the change of the carbon layer structure, and the electron density is transferred from the inside of the tube to the outside of the tube to form an internal and external potential difference, so that the characteristics of substances which react in the internal and external potential difference are changed; on the other hand, as the nano-particles, the carbon nano-tubes have a typical confinement effect, that is, when the system is scaled down to a nano-scale, the movement of electrons in the system is limited by space, the electronic state changes, and the catalytic performance of the system also changes accordingly.

The research on the catalytic performance of multi-walled carbon nanotube modified platinum-loaded tin in propane dehydrogenation reaction [ D ], university in shanghai, (2014) ] modifies the carbon nanotube in a manner of roasting the carbon nanotube at high temperature by air and manufacturing the carbon nanotube activated by nitric acid vapor during self-assembly, and then loads a tin component and a platinum component step by step. The prepared catalyst was finally used to catalyze the propane dehydrogenation reaction to evaluate the performance of the catalyst.

Yan academic, structure characterization and electrocatalytic properties research [ D ], university of Taichii, (2011) ] carbon nanotubes from which amorphous carbon was removed by nitric acid reflux were used as a carrier, platinum and tin components were loaded on the surface by a one-step impregnation reduction method, and the obtained material was used for fuel electrodes.

The invention takes the carbon nano tube with an opening prepared by nitric acid reflux as a carrier, firstly introduces an ethanol solution of chloroplatinic acid into a cavity of the carbon nano tube by an isometric method through a step impregnation method, quickly adds an ethanol solution of stannous chloride after the cavity is filled with the ethanol solution of chloroplatinic acid, quickly stirs and ventilates the ethanol at a certain temperature by utilizing the characteristic of low boiling point of the ethanol, evaporates the ethanol out, so that almost no stannous chloride enters the carbon nano tube, and then dries and reduces hydrogen to prepare the catalyst.

Disclosure of Invention

The invention aims to provide a low-carbon alkane dehydrogenation catalyst, a preparation method and application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

a low-carbon alkane dehydrogenation catalyst comprises the following components in percentage by mass: 1.0-10.0 wt% of Pt, 1.0-5.0 wt% of Sn and 85.0-98.0 wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, the Pt is positioned in the multi-walled carbon nano-tube (shown in figure 1 and figure 2), and the Sn is positioned outside the multi-walled carbon nano-tube. Preferably, the mass percent of Pt is 2.0-8.0 wt%, the mass percent of Sn is 2.0-5.0 wt%, the mass percent of multi-wall carbon nano tube is 87.0-96.0 wt%, and the sum of the mass percent of Pt, Sn and multi-wall carbon nano tube is 100%.

The aperture of the catalyst is 3.0-12.0 nm, and the specific surface area is 104-266 m²(ii) a total pore volume of 0.1 to 0.6cm³/g。

The preparation method of the low-carbon alkane dehydrogenation catalyst comprises the following steps:

(1) concentrated HNO with the concentration of 65-68 wt% is used₃Impregnating the multi-walled carbon nanotube, carrying out oxidation treatment for 2-18 hours, and washing and drying to obtain a multi-walled carbon nanotube carrier;

(2) and (2) sequentially and respectively soaking the multi-wall carbon nano tube carrier in the step (1) by using a platinum-containing compound solution and a tin-containing compound solution, drying for 8-30 h at the temperature of 80-130 ℃ in the air, and then reducing.

The platinum-containing compound in the step (2) is platinum nitrate, chloroplatinic acid, potassium chloroplatinate, tetraammineplatinum dichloride or platinum acetylacetonate; the solvent of the platinum-containing compound solution is water, methanol, acetone or ethanol.

The stanniferous compound in the step (2) is stannic chloride, stannous oxide or nano stannic oxide; the solvent of the tin compound solution is water, methanol, acetone or ethanol.

The platinum-containing compound impregnation in the step (2) is divided into two steps of impregnation, firstly ultrasonic treatment is adopted, the ultrasonic treatment time is 0.3-5.0 h, and then stirring impregnation is adopted, and the stirring time is 0.5-6.0 h; the liquid/solid ratio of the platinum-containing compound solution used for impregnation to the multiwalled carbon nanotube carrier is 10-30 mL/g, the platinum content in the platinum-containing compound solution used for impregnation is 1-8 mg/mL, and the impregnation temperature is 15-45 ℃.

The method for impregnating the multiwalled carbon nanotube carrier by the tin-containing compound solution in the step (2) is stirring impregnation, wherein the stirring time is 5-60 min; the liquid/solid ratio of the tin-containing compound solution used for impregnation to the multiwalled carbon nanotube carrier is 10-30 mL/g, the tin content in the tin-containing compound solution used for impregnation is 2-6 mg/mL, and the impregnation temperature is 70-120 ℃.

Reducing by using a reducing agent or hydrogen in the reduction operation in the step (2), wherein the reducing agent is ethylene glycol or C₁~C₃Carboxylic acid or C₁~C₃The sodium carboxylate of (1).

When reducing by using a reducing agent in the step (2), the molar ratio of the reducing agent to Pt is 10-20: 1, the reduction temperature is 50-300 ℃.

And (3) when hydrogen is used for reduction in the step (2), the reduction temperature is 550-650 ℃.

The invention uses the treated multi-wall carbon nano-tube as a carrier, and loads a metal Pt component and a metal Sn component to prepare the catalyst, and the prepared catalyst is used for the dehydrogenation reaction of low-carbon alkane and has higher selectivity and performance stability of dehydrogenation products.

The invention has the following remarkable advantages:

when the multi-wall carbon nanotube is loaded with the same amount of Pt and Sn metal components, namely the multi-wall carbon nanotube consists of 5wt% of Pt, 3wt% of Sn and 92wt%, the conversion rate of the catalyst for catalyzing propane dehydrogenation and the propylene selectivity are highest only when the Pt is positioned in the multi-wall carbon nanotube and the Sn is positioned outside the multi-wall carbon nanotube. The reason is that when Pt is positioned in the multi-wall carbon nanotube and Sn is positioned outside the multi-wall carbon nanotube, the Pt simple substance, the Sn simple substance and the carbon nanotube interact to form SnPt of an alloy phase_xTherefore, the distribution and the existing state of Pt species are changed, the unique electron-deficient environment in the multi-walled carbon nanotube also changes the electronic characteristics of the catalyst, the special electronic characteristics in the carbon nanotube change the reaction activation energy, the reaction channel is modulated, and the reaction activity is increased. In addition, the catalyst prepared by the invention has good stability when being used for catalyzing the dehydrogenation reaction of the low-carbon alkane, and the conversion rate of propane can still be kept at 26.12% and the selectivity is 97.13% after the propane dehydrogenation catalytic reaction is carried out for 10 hours.

Drawings

FIG. 1 is a Transmission Electron Microscope (TEM) photograph of a catalyst of the invention A;

FIG. 2 is a Transmission Electron Microscope (TEM) photograph of the catalyst A of the present invention;

FIG. 3 is a Transmission Electron Microscope (TEM) photograph of a G catalyst of the present invention;

FIG. 4 is a Transmission Electron Microscope (TEM) photograph of the H catalyst of the present invention.

Detailed Description

The invention uses a multi-wall carbon nano tube material, carries out oxidation treatment on the multi-wall carbon nano tube material by using high-concentration acid, then loads platinum on a carrier, and loads tin on the carrier to obtain the platinum-tin loaded multi-wall carbon nano tube catalyst. The catalyst is used for dehydrogenation reaction of low-carbon alkane, and has good catalytic stability.

The catalyst comprises a multi-walled carbon nanotube, platinum and tin, and preferably comprises 2.0-8.0 wt% of Pt, 2.0-5.0 wt% of Sn and 87.0-96.0 wt% of the multi-walled carbon nanotube.

The catalyst has the advantages of preferable aperture of 3.0-12.0 nm and excellent specific surface areaSelecting 104-167 m²The total pore volume is preferably 0.1-0.5 cm/g³/g。

The multi-walled carbon nanotube for preparing the carrier is prepared by a Chemical Vapor Deposition (CVD) method, the used catalyst is a supported nickel catalyst, the raw material is hydrocarbon, and the preparation temperature is 500-700 ℃.

The preparation method of the catalyst comprises the following steps:

(1) with concentrated HNO₃Impregnating the multi-walled carbon nanotube for oxidation treatment, and washing and drying to obtain a multi-walled carbon nanotube carrier;

(2) and (2) soaking the multi-wall carbon nano tube carrier dried in the step (1) by using a platinum-containing compound solution, then soaking by using a tin-containing compound solution, drying in the air and then reducing.

The method (1) comprises the steps of oxidizing multi-walled carbon nanotubes to prepare a carrier, and oxidizing the carrier to obtain the concentrated HNO₃The concentration is 65.0-68.0 wt%, and the used concentrated HNO₃The liquid/solid ratio of the multi-walled carbon nanotube to the multi-walled carbon nanotube is 40-60 mL/g, and the time of the oxidation treatment is preferably 2-18 h, more preferably 4-16 h.

(1) Step by step concentrated HNO₃And after the multi-wall carbon nano tube is treated, drying the multi-wall carbon nano tube in the air, wherein the drying temperature is preferably 60-160 ℃, and the drying time is preferably 8-36 hours, and more preferably 10-30 hours.

The method comprises the following steps of (2) preparing a catalyst by loading platinum-tin, (2) preferably selecting platinum nitrate, chloroplatinic acid, potassium chloroplatinate, tetraammineplatinum dichloride or platinum acetylacetonate as the platinum-containing compound in the step, (2) preferably selecting tin tetrachloride, stannous chloride, stannous oxide or nano-tin dioxide as the tin-containing compound in the step, (2) preferably selecting an aqueous solution of the platinum-containing compound, a methanol solution of the platinum-containing compound, an acetone solution of the platinum-containing compound and an ethanol solution of the platinum-containing compound in the platinum-containing compound solution, and (2) preferably selecting an aqueous solution of the tin-containing compound, a methanol solution of the tin-containing compound, an acetone solution of the tin-containing compound and an ethanol solution of the tin-containing compound in the step.

(2) The method for impregnating the multi-wall carbon nano tube carrier by using the platinum-containing compound solution is stirring impregnation, before the impregnation, ultrasonic treatment is preferably carried out, the ultrasonic treatment time is preferably 0.3-5.0 h, and then the stirring impregnation is carried out for 0.5-6.0 h. The liquid/solid ratio of the platinum-containing compound solution used for impregnation to the multi-walled carbon nanotube carrier is 10-30 mL/g, and the impregnation temperature is preferably 15-45 ℃. The platinum content in the platinum-containing compound solution used for impregnation is preferably 1-8 mg/mL.

(2) The method for impregnating the multi-wall carbon nano tube carrier by using the tin-containing compound solution is to stir and impregnate for 5-60 min. The liquid/solid ratio of the tin-containing compound solution used for impregnation to the multi-walled carbon nanotube carrier is 10-30 mL/g, and the impregnation temperature is preferably 70-120 ℃. The content of tin in the ethanol solution of the tin-containing compound used for impregnation is preferably 2-6 mg/mL.

(2) Sequentially impregnating a multi-wall carbon nano tube carrier with a platinum-containing compound solution and a tin-containing compound solution, drying in air, and reducing, wherein the drying temperature is preferably 80-130 ℃, and the drying time is preferably 8-30 h.

(2) The reduction of step (2) may be carried out with a reducing agent selected from ethylene glycol, C, or hydrogen₁~C₃Carboxylic acid or C₁~C₃Such as formic acid or sodium formate. When reducing agent is used for reduction, the molar ratio of the reducing agent to Pt is 10-20: 1, the reduction temperature is 50-300 ℃. The solid/liquid ratio of the multi-walled carbon nanotube carrier to the reducing agent solution is preferably 10-200 mg/mL. When the hydrogen is used for reduction in the step (2), the reduction temperature is 550-650 ℃, and the reduction time is preferably 0.5-4.0 h.

The method for dehydrogenating the low-carbon alkane comprises the step of carrying out contact reaction on the low-carbon alkane and the catalyst under the dehydrogenation reaction condition. The dehydrogenation reaction temperature is 500-650 ℃, and the pressure is 0.1-0.5 MPa. The lower alkane is C₃~C₅Such as propane, butane or pentane.

The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

Example 1

Preparation of the catalyst of the invention

(1) Preparation of multiwalled carbon nanotube carrier

2.5g of multi-walled carbon nanotubes (purity > 98 wt.%) were taken,ash content less than 1.5wt.%, provided by the national institute of sciences organic chemistry limited company, number TNSM3, and prepared by Chemical Vapor Deposition (CVD), wherein the catalyst is a supported nickel catalyst, and the preparation temperature is 500-700 ℃) and 125mL of concentrated HNO is used₃Immersing and oxidizing at 140 ℃ for 14 hours, wherein the concentrated HNO₃The concentration of the carbon nano tube is 66.0wt%, the impregnated solid is washed by deionized water, and is dried in the air at the temperature of 110 ℃ for 12 hours, so that the multi-wall carbon nano tube carrier CNTs is obtained.

(2) Preparation of the catalyst

And (2) putting 0.3g of the multi-wall carbon nano tube carrier CNTs prepared in the step (1), 3mL of ethanol solution of chloroplatinic acid with the Pt concentration of 5mg/mL and 3mL of absolute ethanol in a 50mL beaker, stirring at 25 ℃ for 0.5h, then treating with ultrasonic waves at 25 ℃ for 3h, then stirring for 0.5h, then adding 3mL of ethanol solution of stannous chloride with the Sn concentration of 3mg/mL, and stirring at 100 ℃ for 20 min. Then dried at 110 ℃ for 24h, and the resulting black powder was dried in N₂The temperature is raised to 580 ℃ under the atmosphere, and then H₂Reducing for 1 h under atmosphere, and then adding N₂Cooling to room temperature under the atmosphere to obtain a catalyst A, wherein the catalyst A comprises the following components in percentage by mass: 5wt% of Pt, 3wt% of Sn and 92wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, the Pt is positioned in the multi-walled carbon nano-tube, and the Sn is positioned outside the multi-walled carbon nano-tube. The pore diameter is 11.0654 nm, the specific surface area is 265.2946 m²Per g, total pore volume 0.5283 cm³(g) the specific surface area is obtained by adopting a BET equation and the pore diameter and the total pore volume are obtained by adopting a BJH equation according to a nitrogen absorption-desorption curve), and the transmission electron microscope images are shown in figures 1 and 2.

Example 2

Catalyst B was prepared as described in example 1, except that (2) the carrier was impregnated with the ethanol solution of chloroplatinic acid at 0.6mL using 5mg/mL of the ethanol solution of chloroplatinic acid and 5.4 mL of ethanol, to obtain catalyst B, wherein the catalyst B was composed of the following components in mass percent: 1wt% of Pt, 3wt% of Sn and 96 wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, the Pt is positioned in the multi-walled carbon nano-tube, and the Sn is positioned outside the multi-walled carbon nano-tube.

Example 3

A catalyst C was prepared as described in example 1, except that (2) the carrier was impregnated with an ethanol solution of chloroplatinic acid at 5mg/mL in 1.8mL and 4.2 mL, to obtain a catalyst C consisting of the following components in mass percent: the composite material comprises, by mass, 3wt% of Pt, 3wt% of Sn and 94 wt% of multi-walled carbon nanotubes, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nanotubes is 100%, the Pt is positioned in the multi-walled carbon nanotubes, and the Sn is positioned outside the multi-walled carbon nanotubes.

Example 4

Catalyst D was prepared as described in example 1, except that in step (2) catalyst D was prepared using 3mL of an ethanol solution of stannous chloride with a Sn concentration of 12mg/mL, wherein the catalyst D consisted of the following components in mass percent: 5wt% of Pt, 12wt% of Sn and 83 wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, the Pt is positioned in the multi-walled carbon nano-tube, and the Sn is positioned outside the multi-walled carbon nano-tube.

Comparative example 1

The catalyst was prepared as described in example 1, except that step (2). And (2) putting 0.3g of the multi-wall carbon nano tube carrier CNTs prepared in the step (1), 3mL of ethanol solution of stannous chloride with Sn concentration of 3mg/mL and 3mL of absolute ethanol in a 50mL beaker, stirring at 25 ℃ for 0.5h, then treating with ultrasonic waves at 25 ℃ for 3h, then stirring for 0.5h, then adding 3mL of ethanol solution of chloroplatinic acid with Pt concentration of 5mg/mL, and stirring at 100 ℃ for 20 min. Then dried at 110 ℃ for 24h, and the resulting black powder was dried in N₂The temperature is raised to 580 ℃ under the atmosphere, and then H₂Reducing for 1 h under atmosphere, and then adding N₂Cooling to room temperature under the atmosphere to obtain a catalyst E, wherein the catalyst E comprises the following components in percentage by mass: 5wt% of Pt, 3wt% of Sn and 92wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, the Pt is positioned outside the multi-walled carbon nano-tube, and the Sn is positioned inside the multi-walled carbon nano-tube. The pore diameter is 10.0864 nm, the specific surface area is 263.3158 m²Per g, total pore volume 0.5192 cm³And/g (according to a nitrogen adsorption-desorption curve, a BET equation is adopted to obtain the specific surface area, and a BJH equation is adopted to obtain the pore diameter and the total pore volume).

Comparative example 2

A catalyst F having a pore diameter of 8.9705 nm and a specific surface area of 262.5184 m was prepared as described in example 1, except that the step (2) was not performed, i.e., the multi-walled carbon nanotube support was not loaded with any metal component²Per g, total pore volume 0.4996 cm³And/g (according to a nitrogen adsorption-desorption curve, a BET equation is adopted to obtain the specific surface area, and a BJH equation is adopted to obtain the pore diameter and the total pore volume).

Comparative example 3

A catalyst G was prepared by the method of example 1, except that (2) the ethanol solution of stannous chloride was replaced with absolute ethanol, wherein the G catalyst consists of the following components in mass percent: 5wt% of Pt and 95 wt% of multi-wall carbon nano-tube, wherein the sum of the mass percentages of the Pt and the multi-wall carbon nano-tube is 100%, and the Pt is positioned in the multi-wall carbon nano-tube. FIG. 3 shows a transmission electron micrograph.

Comparative example 4

A catalyst H was prepared by the method of example 1, except that (2) the ethanol solution of chloroplatinic acid was replaced with absolute ethanol, wherein the H catalyst consisted of the following components in mass percent: 3wt% of Sn, and 97 wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Sn and the multi-walled carbon nano-tube is 100%, wherein the Sn is positioned outside the multi-walled carbon nano-tube, and a transmission electron microscope picture is shown in figure 4.

Comparative example 5

The catalyst was prepared as described in example 1, except that step (2). And (2) putting 0.3g of the multi-wall carbon nano tube carrier CNTs prepared in the step (1), 3mL of ethanol solution of stannous chloride with Sn concentration of 3mg/mL and 3mL of absolute ethanol in a 50mL beaker, stirring for 0.5h at 25 ℃, then carrying out ultrasonic treatment for 3h at 25 ℃, then stirring for 0.5h, then adding 3mL of absolute ethanol, and stirring for 20min at 100 ℃. Then dried at 110 ℃ for 24h, and the resulting black powder was dried in N₂The temperature is raised to 580 ℃ under the atmosphere, and then H₂Reducing for 1 h under atmosphere, and then adding N₂Cooling to room temperature under the atmosphere to obtain a catalyst I, wherein the catalyst I comprises the following components in percentage by mass: 3 weight percent of Sn, 97 weight percent of multi-wall carbon nano-tube, and the sum of the two mass percent is100% of Sn, wherein the Sn is positioned in the multi-wall carbon nanotube.

Comparative example 6

The catalyst was prepared as described in example 1, except that step (2). And (2) putting 0.3g of the multi-wall carbon nano tube carrier CNTs prepared in the step (1), 3mL of ethanol solution of stannous chloride with the Sn concentration of 3mg/mL and 3mL of ethanol solution of chloroplatinic acid with the Pt concentration of 5mg/mL into a 50mL beaker, stirring for 0.5h at 25 ℃, then treating for 3h by ultrasonic at 25 ℃, then stirring for 0.5h, then adding 3mL of absolute ethyl alcohol, and stirring for 20min at 100 ℃. Then dried at 110 ℃ for 24h, and the resulting black powder was dried in N₂The temperature is raised to 580 ℃ under the atmosphere, and then H₂Reducing for 1 h under atmosphere, and then adding N₂Cooling to room temperature under the atmosphere to obtain a catalyst J, wherein the catalyst J comprises the following components in percentage by mass: 5wt% of Pt, 3wt% of Sn and 92wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, and the Pt and the Sn are both positioned in the multi-walled carbon nano-tube.

Comparative example 7

The catalyst was prepared as described in example 1, except that step (2). And (2) putting 0.3g of the multi-walled carbon nanotube carrier CNTs prepared in the step (1) and 6mL of absolute ethanol solution into a 50mL beaker, stirring at 25 ℃ for 0.5h, then carrying out ultrasonic treatment at 25 ℃ for 3h, then stirring for 0.5h, then adding 3mL of mixed ethanol solution of stannous chloride and chloroplatinic acid with the Sn concentration of 3mg/mL and the Pt concentration of 5mg/mL, and stirring at 100 ℃ for 20 min. Then dried at 110 ℃ for 24h, and the resulting black powder was dried in N₂The temperature is raised to 580 ℃ under the atmosphere, and then H₂Reducing for 1 h under atmosphere, and then adding N₂Cooling to room temperature under the atmosphere to obtain a catalyst K, wherein the catalyst K comprises the following components in percentage by mass: 5wt% of Pt, 3wt% of Sn and 92wt% of multi-walled carbon nano-tube, wherein the sum of the mass percentages of the Pt, the Sn and the multi-walled carbon nano-tube is 100%, and the Pt and the Sn are both positioned outside the multi-walled carbon nano-tube.

Examples 12 to 22

This example evaluates the propane dehydrogenation performance of the catalyst

0.2g of catalyst was loaded in a micro-reactor with 5% propane by volume and N₂The mixture of (A) is a reaction sourceThe material is fed at 600 ℃, 0.10MPa and the propane feeding mass space velocity of 1.8h^-1The average values of the conversion of propane and the selectivity of propylene during the reaction were calculated under the conditions of (1) and the catalyst used and the reaction results in each example are shown in Table 1.

Example 23

0.2g of catalyst A prepared in example 1 are taken and filled in a microreaction device with 5% by volume of propane and N₂The mixture of (A) is used as a reaction raw material, the temperature is 600 ℃, the pressure is 0.11MPa, and the mass space velocity of propane feeding is 1.8h^-1The dehydrogenation reaction was carried out under the conditions shown in Table 2, and the results of the reaction for 10 hours were obtained. Table 2 shows that the catalyst of the present invention has better propane dehydrogenation activity and stability.

To summarize:

(1) transmission electron microscopy of the catalyst a of comparative example 1 and the catalyst F of comparative example 2. The Pt particles are embedded in the tube of multi-walled carbon nanotubes. A very significant increase in pore volume and pore diameter of the metal-loaded A catalyst, probably due to SnPt, occurred comparing the specific surface area, pore volume and pore diameter data for the A and F catalysts_xThe formation and accumulation of the alloy on the inner and outer surfaces of the carbon nanotube. The larger pore diameter is beneficial to improving the mass transfer rate, promoting the desorption of the product propylene and improving the carbon capacity of the catalyst material, thereby promoting the propane dehydrogenation reaction.

(2) Comparative catalysts A, B and C. When Pt is inside the multi-walled carbon nanotube and Sn is outside the multi-walled carbon nanotube and the Sn content is fixed at 3wt%, when the Pt loading is increased from 1wt% to 5wt%, the corresponding propane conversion is increased from 3% to 24% (300 min), and the propylene selectivity is increased from 67% to 98%. An increase in Pt loading contributes to an increase in catalytic activity, but 5wt% has been the high limit of Pt loading reported in the literature.

(3) Catalysts a and D were compared. When the load of Sn is increased from 3wt% to 12wt%, the conversion rate of propane is reduced from 24% to 4.32% (300 min), and the selectivity of propylene is reduced from 98% to 67%. The increase in the loading amount of Sn does not increase the catalytic activity of the catalyst.

(4) Catalyst A, G was compared to H. The catalyst G with the single metal component of 5wt% Pt positioned in the multi-wall carbon nano tube has the catalytic conversion rate of 4.62% (10 h) for propane dehydrogenation and the propylene selectivity of 82.89%; a catalyst H with the single metal component of 3wt% of Sn outside the multi-walled carbon nanotube, wherein the dehydrogenation conversion rate of propane catalyzed by H is 5.63% (10H), and the selectivity of propylene is 70.10%; when the same content of bimetallic components Pt and Sn are used for loading the multi-wall carbon nanotube, Pt is positioned in the multi-wall carbon nanotube, Sn is positioned outside the multi-wall carbon nanotube, the dehydrogenation conversion rate of propane catalyzed by A is 47.95 percent (10 h), the selectivity of propylene is 97.67 percent, the catalytic activity and the selectivity of propylene are obviously improved, which is probably due to the unique SnPt_xThe formation and accumulation of the alloy on the inner and outer surfaces of the carbon nanotube.

(5) Catalysts A, E, J and K were compared. The components of the three components have the same content, and the components comprise 5wt% of Pt, 3wt% of Sn and 92wt% of multi-walled carbon nano-tubes, wherein A is Pt positioned in the multi-walled carbon nano-tubes, and Sn is positioned outside the multi-walled carbon nano-tubes; e is Pt positioned outside the multi-walled carbon nanotube, and Sn is positioned inside the multi-walled carbon nanotube; j is Pt and Sn which are both positioned in the multi-walled carbon nanotube; k is Pt and Sn which are both positioned outside the multi-wall carbon nanotube. Comparing the four structures, the corresponding catalytic activities are that A catalyzes the dehydrogenation conversion rate of propane to 47.95% (10 h), and the selectivity of propylene is 97.67%; the conversion rate of the catalytic propane dehydrogenation is 17.58 percent (10 h), and the selectivity of the propylene is 94.01 percent; the conversion rate of J catalytic propane dehydrogenation is 34.51 percent (10 h), and the selectivity of propylene is 97.25 percent; the conversion rate of the K catalytic propane dehydrogenation is 16.31 percent (10 h), and the selectivity of the propylene is 94.50 percent. The results show that the catalyst has the greatest activity when Pt is inside the multi-walled carbon nanotube and Sn is outside the multi-walled carbon nanotube, probably due to the unique SnPt, when the bimetallic component content is the same_xThe formation and accumulation of the alloy on the inner and outer surfaces of the carbon nanotube.

TABLE 1

Table 2 (for A catalyst)

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.