Catalyst for preparing propylene by propane dehydrogenation and preparation method and application thereof

文档序号：1928878 发布日期：2021-12-07 浏览：9次中文

阅读说明：本技术 一种丙烷脱氢制备丙烯的催化剂及其制备方法和应用 (Catalyst for preparing propylene by propane dehydrogenation and preparation method and application thereof ) 是由康金灿陈琦佳张庆红王野于 2021-08-31 设计创作，主要内容包括：一种丙烷脱氢制备丙烯的催化剂及其制备方法和应用,催化剂的组成包括A、B两种金属组分、助剂元素和载体。A金属元素的质量百分含量为0.01％～10％,B金属元素的质量百分含量为0.05％～40％,助剂元素的百分含量为0.05％～20％,余量为载体。A组分为第Ⅷ族的金属元素,B组分为金属元素Ga、In、Sn、Tl、Bi中的至少一种,助剂元素为Li、Na、K、Rb、Cs、Ce中的至少一种。催化剂采用水热合成法-吸附法联用的方法制备。该催化剂用于丙烷直接脱氢制备丙烯反应中,丙烷转化率接近热力学平衡转化率,丙烯最高选择性超过98％,且催化剂稳定性超过300h,显示出良好的应用前景。(A catalyst for preparing propylene by propane dehydrogenation comprises A, B two metal components, an auxiliary element and a carrier. The mass percentage of the metal element A is 0.01-10%, the mass percentage of the metal element B is 0.05-40%, the mass percentage of the auxiliary element is 0.05-20%, and the balance is the carrier. The component A is a metal element In a VIII group, the component B is at least one of metal elements Ga, In, Sn, Tl and Bi, and the auxiliary element is at least one of Li, Na, K, Rb, Cs and Ce. The catalyst is prepared by a hydrothermal synthesis method and an adsorption method. The catalyst is used in the reaction of preparing propylene by direct dehydrogenation of propane, the conversion rate of propane is close to the thermodynamic equilibrium conversion rate, the highest selectivity of propylene is over 98 percent, the stability of the catalyst is over 300 hours, and the catalyst shows good application prospect.)

1. A preparation method of a catalyst for preparing propylene by propane dehydrogenation is characterized by comprising the following steps:

1) mixing a template agent, a silicon source and water, and uniformly stirring to form a mixed solution;

2) adding a metered A metal element precursor solution into the mixed solution in the step 1), and uniformly stirring;

3) transferring the mixed solution obtained in the step 2) into a hydrothermal synthesis kettle for hydrothermal crystallization to obtain a crystallized product, and washing, drying, grinding and roasting the obtained product to obtain the molecular sieve containing the active component A;

4) adding the molecular sieve obtained in the step 3) into a metered mixed precursor solution containing a B metal element and an auxiliary element, and then standing, drying, grinding and roasting to obtain the molecular sieve catalyst containing the A, B element and the auxiliary element.

2. The process for preparing a catalyst for the dehydrogenation of propane to produce propylene according to claim 1, wherein: the A metal element is a metal element In a VIII group, the B metal element is at least one of metal elements Ga, In, Sn, Tl and Bi, and the auxiliary element is at least one of Li, Na, K, Rb, Cs and Ce.

3. The process for preparing a catalyst for the dehydrogenation of propane to produce propylene according to claim 1, wherein: in the step 1), the template agent is at least one of tetrapropylammonium hydroxide and tetraethylammonium hydroxide; the silicon source is at least one of tetraethyl orthosilicate, silica sol and white carbon black; silicon source of SiO₂The mass concentration is 2-40%, and the mass ratio of the template agent to the silicon source is 0.5-5; the stirring time is 3-24 h, and the temperature is 20-40 ℃.

4. The process for preparing a catalyst for the dehydrogenation of propane to produce propylene according to claim 1, wherein: in the step 2), the precursor of the metal element A is at least one of an oxide, an inorganic salt and a complex of the metal element A, and the mass concentration of the precursor solution of the metal element A is 0.01-50 mg/ml; the stirring time is 5-30 h, and the temperature is 20-80 ℃.

5. The process for preparing a catalyst for the dehydrogenation of propane to produce propylene according to claim 1, wherein: in the step 3), the temperature of the hydrothermal crystallization process is 60-280 ℃, and the crystallization time is 24-120 h; the drying temperature is 30-100 ℃; the roasting time is 1.5-5 h, the roasting temperature is 270-660 ℃, and the roasting atmosphere comprises nitrogen, inert gas or air atmosphere.

6. The process for preparing a catalyst for the dehydrogenation of propane to produce propylene according to claim 1, wherein: in the step 4), the concentration of the metal element B in the mixed precursor solution of the metal element B and the auxiliary agent element is 0.01-10 mol/L, and the concentration of the auxiliary agent element is 0.01-10 mol/L; in the mixed precursor solution, the precursor of the metal element B comprises at least one of an oxide, an inorganic salt and a complex, and the precursor of the auxiliary element comprises at least one of an oxide, an inorganic salt, a complex and a hydroxide.

7. The catalyst prepared by the preparation method of the catalyst for preparing propylene by propane dehydrogenation, which is disclosed by any one of claims 1 to 6, is characterized in that: the catalyst consists of a metal element A, a metal element B, an auxiliary agent element and a molecular sieve carrier; the mass percentage of the metal element A is 0.01-10%, the mass percentage of the metal element B is 0.05-40%, the mass percentage of the auxiliary element is 0.05-20%, and the balance is a carrier; the carrier is a pure silicon Silicate-1 molecular sieve.

8. The application of the catalyst prepared by the preparation method of the catalyst for preparing propylene by propane dehydrogenation in any one of claims 1 to 6 is characterized in that: the method is used for the reaction of preparing propylene by propane dehydrogenation, the catalyst is filled into a reactor, and after the catalyst is reduced in a hydrogen atmosphere, propane or a propane atmosphere containing hydrogen is introduced for the propane dehydrogenation reaction.

9. The use of claim 8, wherein: the reduction temperature is 300-600 ℃, and the reduction time is 1-4 h; the reaction temperature is 350-650 ℃; the reactor is selected from at least one of a fixed bed, a fixed fluidized bed, a circulating fluidized bed or a moving bed.

10. The use of claim 8, wherein: in the propane atmosphere containing hydrogen, the volume content of propane is not less than 25%.

Technical Field

The invention relates to the field of low-carbon alkane dehydrogenation catalysts, in particular to a catalyst for preparing propylene by propane dehydrogenation and a preparation method and application thereof.

Background

Propylene is an important basic chemical, and is mainly used for producing important chemicals such as polypropylene, acrylonitrile, oxo synthesis, propylene oxide, acrolein, acrylic acid and other derivatives. Currently, methods for producing propylene include naphtha Fluid Catalytic Cracking (FCC), methanol to olefin (MTO/MTP), steam cracking technology and the like, but are limited by the problem of carbon emission caused by petroleum resources and coal chemical industry, and the propylene yield in China cannot meet the requirements of the chemical industry on propylene, and a new technology for cleanly increasing the propylene yield needs to be developed. In recent years, the technology for preparing propylene by propane dehydrogenation has attracted much attention, and the technology has the characteristics of low raw material cost, simple technical process, easy separation of raw materials and products and the like, and is industrialized in China.

At present, there are mainly five major processes for propane dehydrogenation, including Catofin process by Lummu, Oleflex process by UOP, FBD process by Snamprogetti and Yarsintez, STAR process by UHDE, and PDH process by Linde. At present, a large number of commercial catalysts are mainly based on Cr and Pt, respectively corresponding to the Catofin (Lummus) and Oleflex (UOP) processes. Although the supported noble metal catalyst used in the prior art shows high initial catalytic activity, the catalyst has short service life and needs frequent regeneration because the catalyst surface is rapidly deactivated by carbon deposition due to deep dehydrogenation to cause carbon deposition. On the other hand, there is also sintering of the metal clusters under high temperature reaction conditions, eventually leading to catalyst deactivation. In addition, Cr is toxic and environmentally undesirable. Research shows that the carbon deposition behavior in the reaction process can be inhibited to a certain extent by introducing hydrogen into the reaction atmosphere, but the addition of hydrogen can reduce the conversion rate of propane. Designing a catalyst for the dehydrogenation of propane to produce propylene with high activity, stability and selectivity remains a challenge in this field of research.

Disclosure of Invention

The invention aims to solve the problems in the prior art and provides a catalyst for preparing propylene by propane dehydrogenation, a preparation method and application thereof.

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

a preparation method of a catalyst for preparing propylene by propane dehydrogenation comprises the following steps:

1) mixing a template agent, a silicon source and water, and uniformly stirring to form a mixed solution;

2) adding a metered A metal element precursor solution into the mixed solution in the step 1), and uniformly stirring;

The A metal element is a metal element In a VIII group, the B metal element is at least one of metal elements Ga, In, Sn, Tl and Bi, and the auxiliary element is at least one of Li, Na, K, Rb, Cs and Ce.

In the step 1), the template agent is at least one of tetrapropylammonium hydroxide and tetraethylammonium hydroxide; the silicon source is at least one of tetraethyl orthosilicate, silica sol and white carbon black; silicon source of SiO₂The mass concentration is 2-40%, and the mass ratio of the template agent to the silicon source is 0.5-5; the stirring time is 3-24 h, and the temperature is 20-40 ℃.

In the step 2), the precursor of the metal element A is at least one of an oxide, an inorganic salt and a complex of the metal element A, and the mass concentration of the precursor solution of the metal element A is 0.01-50 mg/ml; the stirring time is 5-30 h, and the temperature is 20-80 ℃.

In the step 3), the temperature of the hydrothermal crystallization process is 60-280 ℃, and the crystallization time is 24-120 h; the washing process comprises at least one of centrifugation, suction filtration and alcohol washing; the drying comprises at least one of vacuum drying and drying, and the drying temperature is 30-100 ℃; the grinding time is 5-60 min, the roasting time is 1.5-5 h, the roasting temperature is 270-660 ℃, and the roasting atmosphere comprises at least one of nitrogen, inert gas or air atmosphere.

In the step 4), the concentration of the metal element B in the mixed precursor solution of the metal element B and the auxiliary agent element is 0.01-10 mol/L, and the concentration of the auxiliary agent element is 0.01-10 mol/L; in the mixed precursor solution, the precursor of the metal element B comprises at least one of an oxide, an inorganic salt and a complex, and the precursor of the auxiliary element comprises at least one of an oxide, an inorganic salt, a complex and a hydroxide.

The catalyst prepared by the method consists of a metal element A, a metal element B, an auxiliary agent element and a molecular sieve carrier; the mass percentage of the metal element A is 0.01-10%, the mass percentage of the metal element B is 0.05-40%, the mass percentage of the auxiliary element is 0.05-20%, and the balance is a carrier; the carrier is a pure silicon Silicate-1 molecular sieve.

The catalyst is used for the reaction of preparing propylene by propane dehydrogenation, the catalyst is filled in a reactor with the inner diameter of 8mm, and after the catalyst is reduced in a hydrogen atmosphere, propane or a propane atmosphere containing hydrogen is introduced for the propane dehydrogenation reaction.

The reduction temperature is 300-600 ℃, and the reduction time is 1-4 h; the reaction temperature is 350-650 ℃; the reactor is selected from at least one of a fixed bed, a fixed fluidized bed, a circulating fluidized bed or a moving bed.

In the propane atmosphere containing hydrogen, the volume content of propane is not less than 25%.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

(1) according to the catalyst disclosed by the invention, the active metal elements and the auxiliary agent elements are confined in the pore channels of the molecular sieve, so that the sintering resistance of the catalyst is greatly improved.

(2) By adopting the catalyst and the preparation method thereof, the active metal components are highly dispersed, which is beneficial to improving the catalytic activity; and the auxiliary agent element modifies the metal active component, adjusts the surface valence state of the metal active component, inhibits the reaction of propane deep dehydrogenation to generate carbon deposition species, and improves the stability of the catalyst.

(3) The carrier Silicate-1 of the catalyst is a pure silicon molecular sieve, has no acidity, can inhibit the reactions of oligomerization and the like of olefin products, and improves the selectivity of propylene.

(4) In the propane dehydrogenation reaction process of the catalyst, the propane conversion rate is close to the thermodynamic equilibrium conversion rate, the propylene selectivity reaches more than 99% at most, the catalyst stability is good, and the catalytic performance hardly changes after 300h of test.

(5) The catalyst for preparing propylene by propane dehydrogenation provided by the invention has the catalytic performance and catalyst stability far higher than those of the existing industrial catalyst, and has potential industrial application prospects.

Drawings

FIG. 1 shows the performance results of the catalyst for producing olefin by propane dehydrogenation of example 8 with the lapse of reaction time (curve a shows propylene selectivity and curve b shows propane conversion).

FIG. 2 shows X-ray diffraction patterns of a Silicate-1 molecular sieve carrier and catalysts of examples 7 and 8.

FIG. 3 is a transmission electron micrograph of the catalyst of example 8.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

Example 1

15g of deionized water, 12g of tetrapropylammonium hydroxide (25% by mass), 8g of tetraethylorthosilicate (SiO)₂Content 28.4%). Placing in a 100ml beaker, stirring at 25 ℃ for 6h for full hydrolysis, and adding 1.81ml of chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid aqueous solution is 10mg/ml) into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Pt-containing molecular sieve. Adding 2.5ml of mixture containing gallium nitrate and KOH into the molecular sieve dropwiseThe hydrated solution (the concentration of gallium nitrate is 0.13mol/L, the concentration of KOH is 0.05mol/L) is kept stand for 6h at the temperature of 25 ℃; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. XRF analysis shows that the catalyst has Pt element content of 0.3%, Ga element content of 1% and K element content of 0.2%.

Filling 0.5g of the catalyst with a 30-60 mesh sieve into a quartz reaction tube of a normal-pressure fixed bed, and then introducing reaction raw material gas, wherein the reaction gas is propane and hydrogen (the flow rate of propane is 20ml/min, and the flow rate of hydrogen is 7ml/min), the reaction temperature is 600 ℃, and the catalytic performance of the catalyst is shown in table 1.

Example 2

15g of deionized water, 12g of tetrapropylammonium hydroxide (25% by mass), 8g of tetraethylorthosilicate (SiO)₂28.4%) in a 100ml beaker, stirred at 25 ℃ for 6 hours for full hydrolysis, and then 0.86ml of rhodium chloride aqueous solution (the concentration of the rhodium chloride aqueous solution is 20mg/ml) is added into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Rh-containing molecular sieve. Dropwise adding 2.5ml of mixed aqueous solution containing gallium nitrate and cerium nitrate (the concentration of the gallium nitrate is 0.13mol/L and the concentration of the cerium nitrate is 0.07mol/L) into a molecular sieve, and standing for 6 hours at 25 ℃; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. The XRF analysis shows that the prepared catalyst has Rh content of 0.3%, Ga content of 1% and Ce content of 1%.

Filling 0.5g of the catalyst with a 30-60 mesh sieve into a quartz reaction tube of a normal-pressure fixed bed, and then introducing reaction raw material gas, wherein the reaction gas is propane and hydrogen (the flow rate of propane is 20ml/min, and the flow rate of hydrogen is 5ml/min), the reaction temperature is 600 ℃, and the catalytic performance of the catalyst is shown in table 1.

Example 3

15g of deionized water, 12g of tetrapropylammonium hydroxide (25% by mass), 8g of tetraethylorthosilicate (SiO)₂28.4 percent) of the solution is put into a 100ml beaker, stirred for 6 hours at 25 ℃ and fully hydrolyzed, and then 1.81ml of chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid aqueous solution is 10mg/ml) is added into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Pt-containing molecular sieve. Adding 2.5ml of mixed aqueous solution containing stannous chloride and cerium nitrate (the concentration of the stannous chloride is 0.08mol/L and the concentration of the cerium nitrate is 0.035mol/L) into the molecular sieve drop by drop, and standing for 6h at the temperature of 25 ℃; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. The XRF analysis shows that the content of Pt element, Sn element and Ce element in the prepared catalyst is 0.3%, 1% and 0.5%.

Example 4

15g of deionized water, 12g of tetrapropylammonium hydroxide (25% by mass), and 14g of silica Sol (SiO)₂Content 16.2%) in a 100ml beaker, stirring at 25 ℃ for 6h for sufficient hydrolysis, and adding 1.81ml of chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid aqueous solution is 10mg/ml) into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Pt-containing molecular sieve. Adding dropwise 2.5ml of mixed aqueous solution containing bismuth nitrate and KOH (bismuth nitrate concentration is 0.05mol/L, KOH concentration is 0.05mol/L) into molecular sieve, and standing at 25 deg.CStanding for 6 h; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. XRF analysis shows that the catalyst has Pt element content of 0.3%, Bi element content of 1% and K element content of 0.2%.

Example 5

15g of deionized water, 12g of tetrapropylammonium hydroxide (25% by mass), 8g of tetraethylorthosilicate (SiO)₂28.4%) in a 100ml beaker, stirred at 25 ℃ for 6 hours and fully hydrolyzed, and then 1.14ml of an aqueous palladium chloride solution (the concentration of the aqueous palladium chloride solution is 10mg/ml) is added into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Pd-containing molecular sieve. Adding 2.5ml of mixed aqueous solution containing gallium nitrate and RbOH (the concentration of the gallium nitrate is 0.13mol/L and the concentration of the RbOH is 0.05mol/L) into the molecular sieve drop by drop, and standing for 6h at 25 ℃; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. The catalyst prepared by XRF analysis contains 0.3% of Pd element, 1% of Ga element and 0.5% of Rb element.

Filling 0.5g of the catalyst with a 30-60 mesh sieve into a quartz reaction tube of a normal-pressure fixed bed, and then introducing reaction raw material gas, wherein the reaction gas is propane and hydrogen (the flow rate of propane is 20ml/min, and the flow rate of hydrogen is 7ml/min), the reaction temperature is 550 ℃, and the catalytic performance of the catalyst is shown in table 1.

Example 6

15g of deionized water, 12g of tetrapropylammonium hydroxide (mass fraction: 25%), and 8g of tetraethyl orthosilicate(SiO₂28.4%) in a 100ml beaker, stirred at 25 ℃ for 6 hours for full hydrolysis, and then 1.1ml of iridium chloride aqueous solution (the concentration of iridium chloride aqueous solution is 10mg/ml) is added into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Ir-containing molecular sieve. Adding 2.5ml of mixed aqueous solution containing gallium nitrate and KOH (the concentration of the gallium nitrate is 0.13mol/L and the concentration of the KOH is 0.05mol/L) into the molecular sieve drop by drop, and standing for 6h at 25 ℃; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. XRF analysis shows that the prepared catalyst has Ir content of 0.3%, Ga content of 1% and K content of 0.2%.

Example 7

15g of deionized water, 12g of tetraethylammonium hydroxide (25% by mass), 8g of tetraethylorthosilicate (SiO)₂28.4 percent) of the solution is put into a 100ml beaker, stirred for 6 hours at 25 ℃ and fully hydrolyzed, and then 1.81ml of chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid solution is 10mg/ml) is added into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Pt-containing molecular sieve. Adding 2.5ml of mixed aqueous solution containing indium nitrate and RbOH (the concentration of the indium nitrate is 0.08mol/L and the concentration of the RbOH is 0.05mol/L) into the molecular sieve drop by drop, and standing for 6h at 25 ℃; vacuum drying the solid sample at 80 deg.C for 4h, grinding, placing into a muffle furnace, calcining at 400 deg.C for 2h in air atmosphereThe final catalyst is prepared. The XRF analysis shows that the content of Pt element, In element and Rb element In the catalyst is 0.3%, 1% and 0.5%, respectively.

Example 8

15g of deionized water, 12g of tetrapropylammonium hydroxide (25% by mass), 8g of tetraethylorthosilicate (SiO)₂28.4%) in a 100ml beaker, stirred at 25 ℃ for 6 hours for full hydrolysis, and then 0.86ml of rhodium chloride aqueous solution (the concentration of the rhodium chloride aqueous solution is 20mg/ml) is added into the mixed solution; after fully stirring, placing the mixed solution in a 200ml hydrothermal reaction kettle, and crystallizing for 72 hours in an oven at 170 ℃; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 600 ℃ in an air atmosphere to obtain the Rh-containing molecular sieve. Adding 2.5ml of mixed aqueous solution containing indium nitrate and RbOH (the concentration of the indium nitrate is 0.08mol/L and the concentration of the RbOH is 0.05mol/L) into the molecular sieve drop by drop, and standing for 6h at 25 ℃; and (3) drying the solid sample at 80 ℃ for 4h in vacuum, grinding, putting the solid sample into a muffle furnace, and roasting the solid sample at 400 ℃ in an air atmosphere for 2h to obtain the final catalyst. The catalyst prepared by XRF analysis contains Rh 0.3%, In 1% and Rb 0.5%.

Filling 0.5g of the catalyst with a 30-60 mesh sieve into a quartz reaction tube of a normal-pressure fixed bed, and then introducing reaction raw material gas, wherein the reaction gas is propane and hydrogen (the flow rate of propane is 20ml/min, and the flow rate of hydrogen is 5ml/min), the reaction temperature is 650 ℃, and the catalytic performance of the catalyst is shown in table 1.

Comparative example 1

Preparation of SiO by hydrothermal synthesis₂/Al₂O₃The MFI type heteroatom molecular sieve with the framework containing Sn (the mass percent of Sn is 2%) at the molar ratio of 200 is exchanged by 0.5mol/L HCl aqueous solution at 90 DEG C3 times, 3 hours each time, washing, drying, calcining at 550 ℃ for 4 hours; adding the obtained molecular sieve into a chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid aqueous solution is 10mg/ml), mixing for 24 hours, and drying in an oven at 120 ℃; and (3) carrying out secondary calcination in an air atmosphere, wherein the calcination temperature is 550 ℃ and the calcination time is 3h, so as to obtain the required propane dehydrogenation catalyst.

Comparative example 2

Preparation of SiO by hydrothermal synthesis₂/Al₂O₃The MFI type heteroatom molecular sieve with the framework containing Zn (the mass percentage of Zn is 2%) is exchanged for 3 times with 0.5mol/L HCl aqueous solution at 90 ℃ for 3 hours each time, and is calcined for 4 hours at 550 ℃ after being washed and dried; adding the obtained molecular sieve into a chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid aqueous solution is 10mg/ml), mixing for 24 hours, and drying in an oven at 120 ℃; and (3) carrying out secondary calcination in an air atmosphere, wherein the calcination temperature is 550 ℃ and the calcination time is 3h, so as to obtain the required propane dehydrogenation catalyst.

Comparative example 3

Preparation of SiO by hydrothermal synthesis₂/Al₂O₃The molar ratio is 120, the MFI type heteroatom molecular sieve (the mass percentage of Sn is 2%) of which the framework contains Sn is exchanged for 3 times by using 0.5mol/L HCl aqueous solution at 90 ℃ and each time lasts for 3 hours, and the MFI type heteroatom molecular sieve is washed, dried and calcined for 4 hours at 550 ℃; adding the obtained molecular sieve into a rhodium chloride aqueous solution (the concentration of the rhodium chloride aqueous solution is 20mg/ml), mixing for 24 hours, and drying in an oven at 120 ℃; carrying out secondary calcination in air atmosphere at 550 ℃ for 3h to obtain the required propane dehydrogenationA catalyst.

Comparative example 4

Preparation of SiO by hydrothermal synthesis₂/Al₂O₃The MFI type heteroatom molecular sieve with the framework containing In (the mass percentage of In is 2%) is exchanged for 3 times with 0.5mol/L HCl aqueous solution at 90 ℃ for 3h each time, and is calcined for 4h at 550 ℃ after being washed and dried; adding the obtained molecular sieve into a chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid aqueous solution is 10mg/ml), soaking for 24 hours, and then placing in an oven to dry at 120 ℃; and (3) carrying out secondary calcination in an air atmosphere, wherein the calcination temperature is 550 ℃ and the calcination time is 3h, so as to obtain the required propane dehydrogenation catalyst.

Comparative example 5

By using a hydrothermal synthesis method, 15g of deionized water, 12g of tetraethylammonium hydroxide (the mass fraction is 25 percent) and 8g of tetraethyl orthosilicate (SiO)₂28.4 percent) of the total content of the components are placed in a 100ml beaker, stirred for 6 hours at 25 ℃ and fully hydrolyzed, then 1.81ml of chloroplatinic acid aqueous solution (the concentration of the chloroplatinic acid solution is 10mg/ml) and 2.5ml of mixed aqueous solution containing indium nitrate and RbOH (the concentration of the indium nitrate is 0.08mol/L and the concentration of the RbOH is 0.05mol/L) are added into the mixed solution, and after full stirring, the mixed solution is placed in a 200ml hydrothermal reaction kettle and crystallized for 72 hours in a 170 ℃ oven; after natural cooling, centrifuging the solid-liquid mixture in the reaction kettle, and vacuum drying for 4 hours at 80 ℃; and then grinding the solid, putting the ground solid into a muffle furnace, and roasting the solid for 2 hours at 400 ℃ in an air atmosphere to obtain the propane dehydrogenation catalyst. The catalyst prepared by XRF analysis contains Pt element 0.3%, In element 1%, and Rb elementThe content of (B) is 0.5%.

TABLE 1

	Conversion of propane	Propylene selectivity	Methane selectivity	Ethane selectivity	Ethylene selectivity
						Example 1	38.0％	99.3％	0.4％	0.2％	0.1％
Example 2	41.0％	97.2％	1.3％	1.4％	0.1％
						Example 3	36.0％	99.5％	0.2％	0.2％	0.1％
Example 4	42.0％	98.3％	0.6％	0.3％	0.8％
						Example 5	39.0％	99.1％	0.6％	0.2％	0.1％
Example 6	40.0％	94.8％	2.9％	2.1％	0.2％
						Example 7	42.0％	95.3％	2.7％	1.3％	0.7％
Example 8	38.7％	96.8％	2.2％	0.9％	0.1％
						Comparative example 1	32.0％	85.0％	4.2％	4.5％	1.3％
Comparative example 2	30.0％	84.0％	7.1％	5.8％	3.1％
						Comparative example 3	27.0％	87.0％	3.2％	2.5％	2.3％
Comparative example 4	29.0％	82.0％	9.2％	6.5％	2.3％
						Comparative example 5	31.0％	86.0％	4.2％	5.5％	4.3％

The catalytic performance of the catalyst for the dehydrogenation of propane to olefins according to the invention (example 8) is shown in FIG. 1. Curve a is the propylene selectivity of the propane dehydrogenation catalyst and curve b shows the propane conversion with a catalyst stability of over 300 h.

FIG. 2 shows X-ray diffraction patterns of a Silicate-1 molecular sieve carrier and catalysts of examples 7 and 8. It can be seen that all the synthesized catalysts show the characteristic diffraction peak of the molecular sieve, but do not show the characteristic diffraction peak of the metal particles, which indicates that the metal nanoparticles are small in size and highly dispersed.

FIG. 3 is a transmission electron micrograph of the catalyst of example 8. As can be seen, the zeolite molecular sieve which is one of the components of the catalyst is a nanocrystal with uniform distribution of 110-150 nm, and the metal nanoparticles are not exposed on the surface of the molecular sieve, which indicates that the active metal component is encapsulated in the molecular sieve.

The catalyst is prepared by a hydrothermal synthesis method and an adsorption method. The catalyst is used in the reaction of preparing propylene by direct dehydrogenation of propane, the conversion rate of propane is close to the thermodynamic equilibrium conversion rate, the highest selectivity of propylene exceeds 98 percent, and the catalyst has good stability and good application prospect.

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Catalyst for preparing propylene by propane dehydrogenation and preparation method and application thereof

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