CN106807405A - The preparation method and its catalyst of a kind of catalyst for preparing propylene by dehydrogenating propane - Google Patents

Abstract

The present invention relates to a kind of preparation method of the catalyst for preparing propylene by dehydrogenating propane, with the IVth race's metal element and the bimetallic of group III element metallic combination as auxiliary agent, the active component with platinum family element metal as catalytic dehydrogenation, with formed alumina as carrier.The preparation process of catalyst includes：Sn-Al auxiliary agents are introduced into alumina support using co-impregnation, Sn is spreaded more evenly across with atomic level in the carrier, while strengthening the active force between Sn and alumina support；Then dehydrogenation active component is impregnated on the alumina support containing Sn-Al, the interaction force between metal-auxiliary agent-carrier is improved；Finally it is dried the post processing such as roasting, dechlorination, dipping alkali metal promoter, dipping watery hydrochloric acid and vulcanization and finally gives dehydrogenation.Catalyst of the invention can be used for dehydrogenating low-carbon alkane reaction, especially dehydrogenating propane reaction, active height, selectivity good, catalyst stability it is good the advantages of, especially selectivity and stability be obviously improved.

Description

A preparation method of a catalyst for propane dehydrogenation to propylene and its catalyst

technical field

The invention relates to a catalyst for propane dehydrogenation containing Sn, Al bimetallic promoters and alumina as a carrier and a preparation method thereof, especially a catalyst for improving the reaction activity, selectivity and stability of a catalyst for propane dehydrogenation to propylene The preparation method belongs to the catalyst preparation technology in the technical field of industrial catalysis.

Background technique

As an important organic chemical raw material, propylene can be used in large quantities in the production of acrylonitrile, propylene oxide, butanol, octanol, isopropanol, cumene, acrylic acid and nonylphenol in addition to the production of polypropylene. product. Propylene mainly comes from by-products or co-productions such as naphtha cracking and refinery FCC processes, accounting for about 90% of propylene sources. Since the 1990s, with the gradual increase in the consumption of propylene, the traditional propylene production has changed from relying solely on petroleum as a raw material to diversifying the technical route of raw material sources, especially the technical route of producing olefins from low-carbon alkanes as raw materials . The production technology of catalytic dehydrogenation of propane to propylene has attracted increasing attention due to its high selectivity (74-86%), and its output has occupied the third place in the source of propylene, accounting for about 5%.

The catalytic dehydrogenation reaction of propane is limited by the thermodynamic equilibrium, and propane cracking reaction and deep dehydrogenation are prone to occur, and the selectivity decreases; at the same time, the carbon deposition on the surface of the catalyst is accelerated and the deactivation is rapid. Due to the low propane conversion rate and short catalyst life, the industrial application of this method is limited. Therefore, the development of catalysts for propane dehydrogenation to propylene with high activity, high selectivity and high stability has become the key to this technology. Chinese patent CN200710025372.X discloses a preparation method in which an alumina-modified mesoporous molecular sieve is impregnated with a platinum-tin component catalyst on a carrier, the propane conversion rate is only 17%, and the propane selectivity is 93%. Chinese patent CN200910011770.5 discloses a propane dehydrogenation catalyst in which Sn is introduced step by step into an alumina carrier and a platinum group catalyst is used as an active component. The selectivity and stability of the catalyst are high. Chinese patent 200910011772.4 discloses a propane dehydrogenation catalyst containing Sn-alumina carrier. In this invention, Sn is introduced into the carrier when the alumina is gelled, and carbon nanofibers are loaded on the carrier in situ through ethylene cracking. The catalyst is used for propane The activity, selectivity and stability of the dehydrogenation reaction catalyst are greatly improved. Chinese patent 200910057235.3 uses the sol-gel method to introduce the tin component into the aluminum sol, and then load the platinum component and other metal additives after drying and forming. This process solves the problem that the Sn component is easy to reduce and precipitate during the high temperature process, thereby affecting the performance of the catalyst. . Chinese patent 201010510192.2 provides a catalyst for propane dehydrogenation to propylene supported by SBA-15 molecular sieve containing SnAl bimetal in the skeleton, and molded with inorganic oxide as a binder. The catalyst has excellent anti-coking properties, high propane dehydrogenation conversion rate, selectivity and reaction stability.

The mass ratio of Sn/Pt in the above-mentioned catalysts is high (2-25), and Sn is prone to be reduced and precipitated during the high-temperature reaction, which affects the activity and selectivity of the catalyst and causes irreversible deactivation. The Sn additive is conventionally impregnated on the surface of the support, and its direct interaction with the support is weak, and it is easy to be reduced to cause catalyst deactivation. In addition, the preparation methods of the above-mentioned carriers are relatively complicated, and require a carrier molding process in the later stage. Although the propane dehydrogenation conversion rate and olefin selectivity are high under certain conditions, the catalyst is prone to carbon deposition and deactivation under high temperature conditions, resulting in poor reaction stability and short service life of the catalyst.

Contents of the invention

For the problems existing in the prior art, the purpose of the present invention is to provide a kind of catalyst and preparation method thereof for propane dehydrogenation to propylene, the present invention can obtain a kind of supporting Sn, Al bimetallic promoter, low Sn/Pt It is a catalyst with high activity, high selectivity and reaction stability compared with shaped alumina as the carrier, which has obvious social and economic benefits.

In the catalyst prepared by the present invention for propane dehydrogenation to propylene, shaped alumina is used as a carrier, metals of group IV elements and metals of group III elements are used as bimetallic additives, and metals of platinum group elements are used as dehydrogenation active groups point.

The preparation method of the catalyst for propane dehydrogenation to propylene provided by the invention, the process is:

(1) Put the alumina carrier into a solution containing metal salts of Group III elements and metal salts of Group IV elements as additives by co-impregnation, and impregnate for 2-12 hours. Dry at 60-150° C. for 2-12 hours, and bake at 400-700° C. for 10-15 hours to obtain a catalyst carrier.

(2) Using a vacuum impregnation method to load the active component of the catalyst on the catalyst carrier obtained in step (1). Dry the sample at 60-150°C for 2-12h, and bake at 400-700°C for 2-6h.

(3) The product of the above step (2) is dechlorinated by water vapor treatment at 400-700°C for 2-6h, then immersed in nitrate solution to introduce alkali metal additives, and dried at 60-150°C for 2-12h, 400-700°C ℃ roasting 3-6h.

(4) The product of the above step (3) is soaked in hydrochloric acid, dried at 60-150°C for 2-12h, and calcined at 400-700°C for 2-6h. Then sulfide with ammonium sulfide and dry at 60-150°C for 2-12h.

The metal salt of the Group IV element described in step (1) is one or more of the nitrates or chlorides of germanium or tin, and the metal salt of the Group III element is the nitrate or chloride of aluminum One or several.

The active component of the catalyst described in step (2) is the combination of one or more of the platinum group elements metal platinum, palladium, iridium, cerbium or osmium; when the above-mentioned active component is platinum, the platinum source used It is one or more of chloroplatinic acid, platinum ammonia or oxyplatinum acetylacetonate. When the active component is palladium, iridium, rhodium or osmium, the metal source adopts the corresponding metal chloride or organic complex.

Calculated based on the mass of the alumina carrier, the mass percentage of metals of group IV elements in the additives is 0.001-2.5wt.%, the mass percentage of metals of group III elements is 0.001-5wt.%, and the active group of the catalyst The mass percent content of metal Pt is 0.1-0.8wt.%.

The mass ratio of the auxiliary agent group III element metal to group IV element metal in the step (1) is 0.0-10.0.

The alumina carrier described in step (1) is alumina pellets, strip-shaped alumina or granular SB powder.

The mass ratio of the metal promoter of group IV element to the platinum group element metal of the active component is 0-1.5.

Sn and Al are introduced into the alumina carrier by co-impregnation, and the dehydrogenation active component Pt group metal elements are introduced into the carrier by vacuum impregnation.

The auxiliary agent described in step 1 is a combination of one or more metals of group IV elements selected from germanium and tin, and a combination of one or more metals of group III elements selected from aluminum sources. The salt solution used may be nitrate and chloride, such as SnCl ₄ , SnCl ₂ , Al(NO ₃ ) ₃ , AlCl ₃ and the like.

The alumina carrier described in step 1 includes several kinds of alumina pellets provided by foreign companies, several kinds of domestic alumina pellets, self-made strip-shaped alumina and self-made granular SB powder.

In the above-mentioned technical scheme, the drying temperature of step (1) is preferably 110-130°C, the drying time is preferably 5-7h, the roasting temperature is preferably 500-600°C, and the roasting time is preferably 11-13h; steps (2), (3), (4 ) drying temperature is preferably 110-130°C, drying time is preferably 5-7h, the roasting temperature is preferably 500-600°C, and the roasting time is preferably 3-5h; the dechlorination treatment temperature of step (3) is preferably 500-600°C, and the dechlorination time Preferably 4-5h.

The propane dehydrogenation to propylene catalyst of the present invention adopts a fluidized bed, moving bed or fixed bed reactor, preferably a fixed bed reactor. Reaction conditions: normal pressure; reaction temperature is 620°C; mass space velocity of propane is 6.0h ^-1 ; hydrogen-to-hydrocarbon ratio is 1.0; product analysis uses gas chromatography to analyze the content of propane and propylene in the dehydrogenation product online, and calculate the conversion of the reaction rate, propylene selectivity and yield.

The features of the present invention are:

(1) The introduction of Al and Sn in the form of dual additives on the alumina support through the co-impregnation method can make Sn more uniformly dispersed in the support at the atomic level, which is conducive to its full interaction with the support. The Al and Sn additives introduced by co-impregnation can form fresh alumina islands after roasting, which can serve as bridges, greatly increasing the force between the additive Sn atoms and the alumina support, which is beneficial to inhibit the reduction of Sn ⁴⁺ to zero-valent Sn ⁰ , thereby improving the dehydrogenation activity, stability and selectivity of propylene of the catalyst.

As shown in accompanying drawings 1 and 2, it can be found that the conversion rate, Both selectivity and stability were significantly improved.

(2) Using alumina as a carrier with Sn and Al as bimetallic additives, impregnation method supports platinum group metals, group III and group IV elements to prepare a catalyst for propane dehydrogenation to propylene. In the catalyst prepared by this method, the island of Al and Sn bimetallic promoters is conducive to improving the interaction between the active components of the platinum group elements and the support, as well as its dispersion and stability on the surface of the support, thereby preventing the dehydrogenation of active metals in the reaction process. reunion in. The post-impregnated Al promoter on the alumina support can form fresh alumina islands and enhance the direct metal-promoter-support interaction, thereby improving the dehydrogenation activity, olefin selectivity, and catalyst stability of the catalyst.

(3) The ultra-low Sn/Pt ratio and the super-strong interaction between the two in the present invention effectively reduce the reduction of Sn ⁴⁺ to metal Sn during the reaction process, which is beneficial to the improvement of catalyst activity, stability and selectivity.

(4) The carrier of the catalyst is formed alumina pellets, which have large pore size, specific surface area and high thermal stability, and the carrier molding process is omitted. The introduction of the additives in the carrier adopts the well-known impregnation method, and the operation is simple.

Description of drawings

Fig. 1 Propane conversion, propylene selectivity and propylene yield of Pt-Sn-Al/alumina pellet A catalyst for propane dehydrogenation. Evaluation conditions: catalyst mass 1.9g, propane mass space velocity 6h-1, normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

Fig. 2 Propane conversion, propylene selectivity, and propylene yield for propane dehydrogenation over Pt-Sn-Al/alumina pellet B catalyst. Evaluation conditions: catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

detailed description

Example 1

Sn-Al/Al ₂ O ₃ support was prepared by impregnation method. Take 2ml of Al(NO ₃ ) ₃ (0.05gAl/ml) solution and 2.44ml (0.025gSn/ml) SnCl ₄ dilute hydrochloric acid solution into a 200ml beaker, add 20ml of deionized water, and mix well. Weigh 10 g of alumina A pellets and add to the above solution, let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 4 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina pellets is 38.4%, the propylene selectivity is 92.9%, and the propylene yield is 35.7%. (Table 1).

Example 2

Sn-Al/Al ₂ O ₃ support was prepared by impregnation method. Take 4.5ml Al(NO ₃ ) ₃ (0.05gAl/ml) solution and 2.44ml (0.025gSn/ml) SnCl ₄ dilute hydrochloric acid solution into a 200ml beaker, add 20ml deionized water, and mix well. Weigh 10 g of alumina A pellets and add to the above solution, let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 2 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation to propylene catalyst supported by the Al-Sn bimetallic aided alumina pellets is 39.2%, the propylene selectivity is 92.6%, and the propylene yield is 36.3%. (Table 1).

Example 3

Sn-Al/Al ₂ O ₃ support was prepared by impregnation method. Take 9ml of Al(NO ₃ ) ₃ (0.05gAl/ml) solution and 2.44ml (0.025gSn/ml) of SnCl ₄ dilute hydrochloric acid solution into a 200ml beaker, add 20ml of deionized water, and mix well. Weigh 10 g of alumina A pellets and add to the above solution, let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 4 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina ball is 37.6%, the propylene selectivity is 93.9%, and the propylene yield is 35.3%. (Table 1).

Comparative example 1

In order to compare the performance of the propane dehydrogenation to propylene catalyst supported by Al-Sn bimetallic promoters on alumina pellets, Pt-Sn/Al ₂ O ₃ supports were prepared by impregnation method. Take 2.44ml (0.025gSn/ml) of dilute hydrochloric acid solution of SnCl ₄ into a 200ml beaker, add 20ml of deionized water, and mix well. Weigh 10 g of alumina A pellets and add to the above solution, let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 2 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina pellets is 36.2%, the propylene selectivity is 88.8%, and the propylene yield rate is 32.2%. (Table 1).

Table 1 Propane conversion, propylene selectivity and propylene yield of Pt-Sn-Al/alumina pellet A catalyst for propane dehydrogenation reaction 10h. Evaluation conditions: catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

Example 4

Sn-Al/Al ₂ O ₃ support was prepared by impregnation method. Take 2ml of Al(NO ₃ ) ₃ (0.05gAl/ml) solution and 2.44ml (0.025gSn/ml) SnCl ₄ dilute hydrochloric acid solution into a 200ml beaker, add 20ml of deionized water, and mix well. Weigh 10 g of alumina B pellets and add to the above solution, and let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 4 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina ball is 37.8%, the propylene selectivity is 91.4%, and the propylene yield is 34.5%. (Table 2).

Example 5

Sn-Al/Al ₂ O ₃ support was prepared by impregnation method. Take 4.5ml Al(NO ₃ ) ₃ (0.05gAl/ml) solution and 2.44ml (0.025gSn/ml) SnCl ₄ dilute hydrochloric acid solution into a 200ml beaker, add 20ml deionized water, and mix well. Weigh 10 g of alumina B pellets and add to the above solution, and let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 4 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina pellets is 36.7%, the propylene selectivity is 93.6%, and the propylene yield rate is 34.3%. (Table 2).

Example 6

Sn-Al/Al ₂ O ₃ support was prepared by impregnation method. Take 9ml of Al(NO ₃ ) ₃ (0.05gAl/ml) solution and 2.44ml (0.025gSn/ml) of SnCl ₄ dilute hydrochloric acid solution into a 200ml beaker, add 20ml of deionized water, and mix well. Weigh 10 g of alumina B pellets and add to the above solution, and let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 2 hours before use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina ball is 36.5%, the propylene selectivity is 94.2%, and the propylene yield is 34.4%. (Table 2).

Table 2 Propane conversion, propylene selectivity and propylene yield of Pt-Sn-Al/alumina pellet B catalyst for propane dehydrogenation reaction for 10 h. Evaluation conditions: catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

Comparative example 2

In order to compare the performance of the propane dehydrogenation to propylene catalyst supported by Al-Sn bimetallic promoters on alumina pellets, Pt-Sn/Al ₂ O ₃ supports were prepared by impregnation method. Take 2.44ml (0.025gSn/ml) of dilute hydrochloric acid solution of SnCl ₄ into a 200ml beaker, add 20ml of deionized water, and mix well. Weigh 10 g of alumina B pellets and add to the above solution, and let it stand for adsorption for 4 hours. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and calcinate at 550°C for 12 hours to obtain a catalyst carrier with dual promoters.

Take 10g of the above-mentioned carrier and put it into a 250ml suction filter bottle, and vacuumize for 0.5h. Add 1.35ml (0.037gPt/ml) of chloroplatinic acid solution and 2.4ml of 10% dilute hydrochloric acid. Dry at 60°C for 4 hours, dry at 120°C for 4 hours, and bake at 550°C for 4 hours.

Then the prepared catalyst was subjected to steam treatment at 550°C for 4h; then impregnated with 5.6ml KNO ₃ (0.025gK/ml) solution to introduce alkali metal additives, dried the sample at 120°C for 4h, and roasted at 550°C for 4h; impregnated with 1.2ml HCl (10 %) of dilute hydrochloric acid, dried at 120°C for 4h, and roasted at 550°C for 4h. Then use 1.0ml (NH ₄ ) ₂ S (2%) ammonium sulfide for sulfidation, fully dry at 120°C for 3 hours, and use it for later use.

Evaluation conditions: before the propane dehydrogenation reaction, the catalyst was reduced with hydrogen at 480°C for 2 hours, and used for the propane dehydrogenation reaction. Catalyst mass 1.9g, propane mass space velocity 6h ^-1 , normal pressure, reaction temperature 620°C, hydrogen/propane volume ratio 1:1.

The reaction results are as follows: after 10 hours of reaction, the propane conversion rate of the propane dehydrogenation propylene catalyst supported by the Al-Sn bimetallic aided alumina ball is 35.6%, the propylene selectivity is 91.6%, and the propylene yield is 32.6%. (Table 2).

Claims (9)

1. the preparation method of a kind of catalyst for preparing propylene by dehydrogenating propane, it is characterised in that：Preparation process For：

(1) alumina support is put into using co-impregnation and contains auxiliary agent group III element slaine and the IVth race In the solution of metal element salt, 2-12h is impregnated, 60-150 DEG C dries 2-12h, 400-700 DEG C of roasting 10-15h After obtain catalyst carrier；

(2) vacuum impregnation technology is used, the work of supported catalyst in the catalyst carrier of the middle gained of step (1) Property component, 60-150 DEG C of sample is dried into 2-12h, 400-700 DEG C of roasting 2-6h；

(3) product of above-mentioned steps (2) carries out steam treatment dechlorination 2-6h at 400-700 DEG C, then soaks Stain nitrate solution introduces alkali metal promoter, and by sample, 60-150 DEG C dries 2-12h, 400-700 DEG C of roasting 3-6h；

(4) the product dipping hydrochloric acid of above-mentioned steps (3), 60-150 DEG C dries 2-12h, 400-700 DEG C of roasting 2-6h, is then vulcanized with ammonium sulfide, and 60-150 DEG C dries 2-12h.

2. preparation method according to claim 1, it is characterised in that：Described in step (1) the IVth Race metal element salt is one or several in the nitrate or chloride of germanium or tin, the group III element gold Category salt for aluminium nitrate or chloride in one or several.

3. preparation method according to claim 1, it is characterised in that：Catalysis described in step (2) The active component of agent is the combination of one or more in platinum family element metal platinum, palladium, iridium, lawrencium or osmium；When upper When stating active component for platinum, platinum source used is the one kind in chloroplatinic acid, platinum ammonia or acetylacetone,2,4-pentanedione oxygen platinum or two kinds More than, when active component is palladium, iridium, lawrencium or osmium, source metal uses corresponding metal chloride or organic complex Thing.

4. the preparation method according to claim 1,2 or 3, it is characterised in that：Based on alumina support Mass Calculation, in auxiliary agent the weight/mass percentage composition of the IVth race's metal element be 0.001~2.5wt.%, the IIIth race The weight/mass percentage composition of metal element is 0.001~5wt.%, and the active component of catalyst is Pt metal quality hundred Content is divided to be 0.1~0.8wt.%.

5. preparation method according to claim 1, it is characterised in that：Auxiliary agent described in step (1) The mass ratio of group III element metal and the IVth race's metal element is 0.0~10.0.

6. preparation method according to claim 1, it is characterised in that：Oxidation described in step (1) Alumina supporter is alumina globule, the aluminum oxide of bar shaped or graininess SB powder.

7. preparation method according to claim 1, it is characterised in that：The IVth described race's metal element The mass ratio of auxiliary agent and active component platinum family element metal is 0~1.5.

8. preparation method according to claim 1, it is characterised in that：Step (1) drying temperature It it is 110-130 DEG C, drying time is 5-7h, sintering temperature is 500-600 DEG C, and roasting time is 11-13h； Step (2), (3), the drying temperature of (4) weight are 110-130 DEG C, and drying time is 5-7h, sintering temperature It it is 500-600 DEG C, roasting time is 3-5h；The dechlorination treatment temperature of step (3) is 500-600 DEG C, dechlorination Time is 4-5h.

9. the catalyst for preparing propylene by dehydrogenating propane that prepared by a kind of any methods describeds of claim 1-8.