CN113559853A

CN113559853A - Catalyst for preparing propylene by direct dehydrogenation of propane

Info

Publication number: CN113559853A
Application number: CN202110963865.8A
Authority: CN
Inventors: 谭理; 王鹏
Original assignee: Fuzhou University
Current assignee: Fuzhou University
Priority date: 2021-08-21
Filing date: 2021-08-21
Publication date: 2021-10-29

Abstract

本发明公开了一种丙烷直接脱氢制丙烯的催化剂及其制备方法，属于催化剂制备领域。所述的催化剂由Pt、Ga、Al、Si等金属（或氧化物）组成，其重量百分含量为：Pt：0.001~0.1%，Ga：1%~10%，Al：23.100%~51.635%，Si：0.5~20%，O：44.200~49.475%。本发明具有制备成本低、丙烯选择性高、催化剂结构稳定、积炭少等优点，推广应用前景广阔。The invention discloses a catalyst for directly dehydrogenating propane to propylene and a preparation method thereof, belonging to the field of catalyst preparation. The catalyst is composed of metals (or oxides) such as Pt, Ga, Al, Si, and its weight percentages are: Pt: 0.001~0.1%, Ga: 1%~10%, Al: 23.100%~51.635% , Si: 0.5~20%, O: 44.200~49.475%. The invention has the advantages of low preparation cost, high propylene selectivity, stable catalyst structure, less carbon deposition and the like, and has broad prospects for popularization and application.

Description

Catalyst for preparing propylene by direct dehydrogenation of propane

Technical Field

The invention belongs to the field of catalyst preparation, and particularly relates to a catalyst for efficiently synthesizing propylene by directly dehydrogenating propane at low temperature, and a preparation method and application thereof.

Background

With the increasing shortage of petroleum resources and the rising price and day, the future world economic development faces the limitation of shortage of energy and resources, and simultaneously, the change of the world energy pattern is promoted. Shale gas is being developed as a novel unconventional natural gas resource in a large quantity and is known to have the advantages of large reserves, long mining life, long production cycle and the like. In recent years, means for effectively extracting shale gas by improving a hydraulic fracturing technology is continuously developed, a source of propane is effectively replaced, and the capacity increase and the operating rate of the traditional propylene production process are seriously compressed due to the influence of epidemic situations and the like. Therefore, how to convert the shale gas into high value-added chemicals in an effective way, and especially applying the shale gas to the aspect of propane dehydrogenation to prepare high-value propylene shows good economic benefits.

Propylene, as one of the most important production building blocks, can be used to produce a number of important organic chemicals, such as: polypropylene, acrylonitrile, butyl/octyl alcohol, propylene oxide, phenol/acetone, acrylic acid and ester, epichlorohydrin and the like; production of fine chemicals, such as: synthetic resins, synthetic fibers, synthetic rubbers, and the like. In addition, the product can be used as raw material in the oil refining industry to produce laminated gasoline, thus alleviating energy crisis. In addition, the method can also be applied to the fields of environmental protection, medical science, basic research and the like.

So far, the catalyst capable of realizing industrialization of propane dehydrogenation is only PtSn/Al₂O₃Or CrO_x/Al₂O₃A catalyst. Therefore, extensive research has been focused on Pt-based and CrO for decades_xThe modification of the base catalyst, the reduction of the dosage and the design of the catalyst structure improve the catalytic efficiency, reduce the cost, protect the environment and prolong the reaction life. Therefore, the development of an alternative, low cost, controllable propane dehydrogenation catalyst is still necessary for the utilization of natural gas resources.

Has higher heat absorption rate (Δ Htheta 298 = 124.3 kJ. mol) due to the direct dehydrogenation process of propane^-1) Higher reaction temperatures (550 ℃ C. and 700 ℃ C.) are required. Such harsh reaction conditions pose challenges to the thermal stability of the catalyst. The realization of propane dehydrogenation at a lower temperature has a series of advantages of reducing energy consumption, realizing green chemistry, inhibiting coking, sintering and the like, and arouses more and more interests of researchers. Considering the thermodynamic equilibrium limitations of propane direct dehydrogenation, how to achieve a propane direct dehydrogenation process with good catalytic performance at low temperatures is an emerging significant challenge. Therefore, the development of a highly stable catalyst having good low-temperature catalytic performance is highly desired.

Among the most promising catalysts for direct propane dehydrogenation, the monatomic Pt catalyst has been widely studied and applied due to its advantages such as a definite and isolated active site, and a unique and superior catalytic performance. Under low temperature conditions, the atom dispersed Pt sites can easily dissociate the first and second C-H bonds of the alkane, and the side reaction of generating coke is effectively reduced. However, the isolated Pt active sites have high surface Gibbs free energy, and agglomeration and sintering can occur in the catalytic process, thereby further causing the catalyst to be deactivated. To rationally design PDH catalysts, a number of strategies have been proposed. For example, post-transition metal elements (e.g., Sn, Zn, Ga, In) have been explored as co-catalysts to improve the dispersion, geometry, and electronic properties of Pt, and to improve activity, selectivity, stability, and anti-coking properties. And alumina has a stronger carrier effect on gallium oxide, thereby being beneficial to maintaining the dispersion of Pt species. On the other hand, the inorganic oxide shell layer is wrapped on the upper surface of the catalyst to serve as a physical barrier, so that the aggregation of Pt species is prevented, and the thermal stability and the coking resistance of the catalyst can be improved.

CN112135687A discloses an impregnation method for loading K-doped PtGa/Al₂O₃-SiO₂The composite catalyst is used for a fixed bed reactor, the reaction temperature is 570 ℃, 10 percent of propane is used under the pressure of 5 bar, and the space velocity is 12h^-1Under the reaction conditions of (1), 5 wt% SiO was introduced₂The catalyst (A) is the catalyst with the best performance, the conversion rate is 41% in the initial 1 minute, and is reduced to 40% after 11 minutes. And pure Al₂O₃Comparison of Supported catalysts, different SiO₂The stability of the introduced catalyst is firstly followed by SiO₂Is increased, and the introduced B acid site also causes side reactions to occur more easily. Thus, an optimum SiO exists₂The amount is in the range, but deactivation due to side reactions still occurs.

CN112221493A discloses a method for preparing trace precious metal modified uniformly distributed Pt-Ga₂O₃/Al₂O₃And Rh-Ga₂O₃/Al₂O₃Catalyst, the loaded active component is Ga₂O₃Trace noble metal as assistant at reaction pressure 0.1 MPa and reaction temperature 600 deg.c₃H₈/H₂=1/1, nitrogen as balance gas, mass space velocity 10h^-1Under the condition, the initial conversion rate of the catalyst with different Pt loading amounts is 19-27%, the initial conversion rate after 4 hours of reaction is 8-17%, the selectivity is basically maintained at about 88-99%, and the catalyst shows a rapid inactivation property.

CN110237840B discloses a method for preparing monoatomic Pt/TiO by adopting electrostatic adsorption₂The catalyst has the reaction pressure of normal pressure and the reaction temperature of 580 ℃ and C₃H₈/H₂=1/1 space velocity 3200 h^-1Under the conditions of (1), the conversion rate is 20%, the selectivity is 98%, and the superiority of the monatomic Pt catalyst in the direct dehydrogenation of propane is fully shown.

The Jingulong topic group (ACS Catalysis, 2016, 6, 2158-₂O₃Catalyst, 500 mg of catalyst is under normal pressure, reaction temperature of 600 ℃ and space velocity of 3h⁻¹，C₃H₈/H₂=1/1, nitrogen as balance gas, total flow 50 mL/min. The initial equilibrium conversion was 35%, after 4h 31%, the selectivity 94% and the deactivation rate parameter 15%. Although Pt as an adjuvant can reduce Zn as an active site²⁺To achieve good dehydrogenation activity and minimized Pt usage, but carbon deposition and unstable active structure still cause significant deactivation to occur.

The Weckhuysen project group (Angewandte Chemie-International Edition, 2014, 53, ‏ 9251-one 9256) adopts an equal volume impregnation method to synthesize Al loaded with 1000 ppm Pt, 3 wt% Ga and 0.25 wt% K₂O₃The catalyst of (1). At atmospheric pressure, 0.15g of catalyst was used at 620^oC reaction temperature, propane flow rate 9 mL/Min^-1The catalyst was evaluated under conditions such that a conversion of 42% was achieved in the first cycle with a selectivity of 97%, and after 15 minutes of each cycle, a conversion of 750% was required^oUsing 6% of O under C₂Regeneration is carried out. The doped K covers acid sites, so that the generation of carbon deposition can be inhibited to a certain extent, but the generation of carbon deposition is still observed to be more through an online ultraviolet-visible Raman spectrum. And the dispersion before and after Pt regeneration has not changed significantly, indicating the presence of metal carrierStrong interaction between them.

Taoufik (ACS Catalysis, 2018, 8, 7566-one 7577) subject group adopts a grafting method to graft Ga (i-Bu)₃The difference between different active sites was investigated by grafting onto alumina and silica supports, indicating that Al-O-Ga active sites have better capacity for heterolytic cleavage of C-H bonds than Si-O-Ga active sites. However, the catalyst loaded with active metal by the grafting method has poor activity and stability (initial conversion rate is 24%, reaction time is 25h later, 9%, and selectivity is maintained at about 90%).

The Luan Hui topic group (Science, 2012, 335, 1205-₂O₃The coating can well adjust Pd/Al₂O₃The catalyst surface and the performance study of the oxidative dehydrogenation reaction of ethane at high temperature. Due to Al₂O₃The limit function of the atomic layer greatly improves the anti-sintering capability of the Pd particles, and simultaneously weakens the adsorption affinity of product molecules to Pd species, thereby well improving the anti-sintering capability and the anti-carbon deposition capability of the catalyst.

The Somorjai topic group (Nature Materials, 2009, 8, 126-131) designs a stable high-temperature-resistant mesoporous amorphous silica coated Pt nanoparticle core-shell structure for CO oxidation and ethylene hydrogenation research at high temperature, and shows good stability. The synthesis is realized by adopting a three-step strategy: (1) synthesizing nano Pt particles by taking tetradecyl trimethyl ammonium bromide as a blocking agent; (2) silica polymerization around Pt core to form Pt @ SiO₂A mesoporous structure; (3) removing organic molecules by calcination to generate Pt @ SiO₂Core-shell nanoparticles.

The Schluth group of topics (Angewandte Chemie-International Edition, 2006, 118, 8404-. Au gel is synthesized and then reduced to obtain Au nano particles which are uniformly distributed, then silicon dioxide is wrapped on the surfaces of the Au nano particles, and monodisperse Au @ SiO is obtained after the growth of a silicon shell is finished₂A nanoparticle. At Au @ SiO₂Nano-ball surface coatingCoating a surfactant, reacting with n-butyl zirconium to coat zirconium oxide, and calcining to obtain Au @ SiO₂@ZrO₂. Finally, SiO is treated by NaOH₂Dissolving to obtain hollow Au @ ZrO₂A catalyst.

The research shows that the Pt-based catalysts obtained by the conventional synthesis strategy have the defects of high reaction temperature, low conversion rate, easy inactivation of the catalysts and the like.

Disclosure of Invention

The invention aims to provide a catalyst for preparing propylene by direct propane dehydrogenation and a preparation method thereof.

The catalyst provided by the invention comprises the following components in percentage by mass: 1. pt: 0.001 to 0.1%, Ga: 1% -10%, Al: 23.100% -51.635%, Si: 0.5-20%, O: 44.200-49.475%.

The invention adopts an impregnation-cladding method to prepare the catalyst, and the preparation steps are as follows:

1) commercial gamma-Al₂O₃1-5 times of air^oThe temperature rise rate of C/min is increased to 700^oAnd C, maintaining for 2-3 hours, and vacuumizing for 2 hours at the low pressure of 0.01MPa for later use.

2) Weighing a certain mass of Ga (NO)₃)₃·xH₂O, weighing Pt (NH) according to the mass ratio of Pt/Ga = 0.0001-0.1₃)₄(NO₃)₂Dissolved in Pt/H₂And (4) marking the solution A as the water with the weight ratio of O = 0.000008-0.0008. With Pt/Al₂O₃Weighing Al in a weight ratio of = 0.00001-0.001₂O₃. Dropwise adding the solution A into the weighed Al₂O₃Standing for 2-3 h, drying, grinding and calcining to obtain PtGa/Al₂O₃A catalyst.

3) With ethanol/ammonia = 20: 1-40: 1 in the volume ratio of PtGa to Al as a B solution₂O₃(g) Ammonia water (ml) = 0.15-0.3, and weighing PtGa/Al₂O₃Adding the mixture into the solution B, and carrying out ultrasonic treatment to obtain a suspension C.

4）And (3) preparing a solution D according to the proportion of Tetraethoxysilane (TEOS) (g)/ethanol (ml) = 0.00058-0.02332, dripping the solution D into the suspension C at the speed of 1-5 ml/h, stirring for 10-20 h, and centrifuging to obtain the product. Drying and grinding the obtained product at 353K, and calcining the product in air at 623-673K for 2-4 hours (the heating rate is 1-2)^oC·min^-1) The obtained mass percentages are respectively as follows: pt: 0.001 to 0.1%, Ga: 1% -10%, Al: 23.100% -51.635%, Si: 0.5-20%, O: 44.200-49.475%.

The prepared catalyst has the following application: mixing the catalyst and quartz sand in a ratio of 1: 5, and filling the mixture into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oAnd C, maintaining for 1-2 hours, and aiming at blowing off impurities on the surface of the catalyst. The ratio of propane/hydrogen (volume ratio) = 1: 1, argon is used as balance gas, the formed mixed gas is used as raw material, and the reaction temperature is 450 DEG^oC, the reaction pressure is 0.1 MPa, and the airspeed is 1-3 h^-1Then, propylene was synthesized.

The invention principle is as follows: the strategy of coating inorganic oxide can physically obstruct the migration of metal particles to a certain extent, and simultaneously change Ga by changing metal-carrier interface₂O₃The high-dispersion Pt sites are anchored by Ga species with different valence states after reduction, so that the catalytic performance, the sintering resistance and the carbon deposition resistance are improved. Therefore, the novel low-temperature catalyst with high activity, high propylene selectivity, high stability and carbon deposition resistance is prepared by using the Pt with ultra-low loading as an active phase, based on the strong carrier effect of gallium oxide and aluminum oxide, radiating and forming high-dispersion Pt sites by using the gallium oxide as a substrate, and wrapping a silicon dioxide shell layer on the surface of active metal.

Compared with the prior art, the Pt-based catalyst for preparing propylene by directly dehydrogenating propane wrapped by amorphous silica on the surface layer has the beneficial effects that:

1) the active component of the catalyst has small particle size and uniform distribution, and Ga clusters are uniformly dispersed in Al₂O₃High dispersion Pt active site fast anchor on carrierThe Pt catalyst is fixed on a Ga cluster, and is limited to migrate on the surface by a silicon dioxide thin shell layer to form a Pt active site structure with a stable structure, so that the catalytic activity at low temperature, high propylene selectivity and thermal stability of the catalyst are improved.

2) The catalyst is wrapped on the surface of the amorphous silicon dioxide shell layer, so that the occurrence of side reactions such as cracking, polymerization, deep dehydrogenation and the like is effectively inhibited, and the inactivation of the catalyst is slowed down.

3) The low-load high-dispersion Pt locus effectively improves the utilization rate of noble metal atoms and reduces the economic cost.

Drawings

FIG. 1 (a-d) 2.5% Si @0.1Pt5Ga/Al after reaction₂O₃Spherical aberration electron micrographs of the catalyst.

FIG. 2 (a-c) 0.1Pt5Ga/Al after reaction₂O₃2.5% Si @0.1Pt5Ga/Al after reaction of catalyst and (d-f)₂O₃Spherical aberration electron micrographs of the catalyst.

FIG. 3 (a-b) 0.1Pt5Ga/Al after reaction₂O₃2.5% Si @0.1Pt5Ga/Al after reaction of catalyst and (c-d)₂O₃Electron micrograph of catalyst.

FIG. 4 (a-f) 2.5% Si @0.1Pt5Ga/Al after reaction₂O₃Spherical aberration electron micrographs of the catalyst.

Figure 5 (a-b) DRIFT-CO plot of catalyst after reaction.

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.

Example 1:

commercial gamma-Al₂O₃In the air by 5^oThe temperature rise rate of C/Min is increased to 700^oAnd C, maintaining for 2 hours, and vacuumizing for 2 hours by using a vacuum oven under the pressure of 0.01MPa for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，36.68gGa(NO₃)₃·xH₂O was dissolved in 250 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A. Taking 2.5 mL of solution A, dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after completely dropwise adding, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting the beaker into an oven 80%^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.001Pt5Ga/Al₂O₃。

0.3g of synthesized 0.001Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.1166 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a dropping rate of 3 mL/min, at which time the stirring was vigorous at 1200 revolutions per minute. Stirring is continued for 15h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 4h, and obtaining the content Pt: 0.001 percent; ga: 5 percent; al: 43.687%%; si: 5 percent; o: 46.312% catalyst, noted 5% Si @0.001Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 5% Si @0.001Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC and maintaining for 2h, then introducing propane: hydrogen = 1: 1 (airspeed 1 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 5.8 percent, the selectivity of propylene is 90.1 percent, and the inactivation rate constant is 0.059 h^-1。

Example 2:

commercial gamma-Al₂O₃In the air by 5^oThe temperature rise rate of C/Min is increased to 700^oC, maintaining for 2 hours, and vacuum oven 0Vacuumizing at 01MPa for 2h for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，3.668gGa(NO₃)₃·xH₂O was dissolved in 25 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A. Taking 2.5 mL of solution A, dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after completely dropwise adding, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting the beaker into an oven 80%^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.01Pt5Ga/Al₂O₃。

0.3g of synthesized 0.01Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.1166 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a dropping rate of 3 mL/min, at which time the stirring was vigorous at 1200 revolutions per minute. Stirring is continued for 15h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 4h, and obtaining the content Pt: 0.01 percent; ga: 5 percent; al: 43.68 percent; si: 5 percent; o: 46.31% catalyst, reported as 5% Si @0.01Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 5% Si @0.01Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC and maintaining for 2h, then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. Propane conversion 9.5%, propylene selectivity 90.4%, deactivation rate constant 0.043 h^-1。

Example 3:

commercial gamma-Al₂O₃In the air by 5^oThe temperature rise rate of C/Min is increased to 700^oAnd C, maintaining for 2 hours, and vacuumizing for 2 hours by using a vacuum oven under the pressure of 0.01MPa for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，0.3668gGa(NO₃)₃·xH₂O was dissolved in 2.5 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A. Dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after the dropwise adding is completed, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting into an oven 80^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.1Pt5Ga/Al₂O₃。

0.3g of synthesized 0.1Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. Then, 0.0116g of TEOS was weighed and dissolved in 20mL of absolute ethanol and the solution was designated as D solution. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 5 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 10h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 2h, obtaining the content Pt: 0.1 percent; ga: 5 percent; al: 48.7 percent; si: 0.5 percent; o: 45.7% catalyst, reported as 0.5% Si @0.1Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 0.5% Si @0.1Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of the reactor bedThe layer temperature is raised to 450 deg.C^oC and maintaining for 2h, then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. Propane conversion rate is 22.5%, propylene selectivity is 90.0%, and inactivation rate constant is 0.019 h^-1。

Example 4:

0.3g of synthesized 0.1Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.0583 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 4 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 12h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 3 hours, and obtaining the content Pt: 0.1 percent; ga: 5 percent; al: 46.4 percent; si: 2.5 percent; o: 46.0%% of catalyst, noted as 2.5% Si @0.1Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 2.5% Si @0.1Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 23.0 percent, the selectivity of propylene is 95.0 percent, and the inactivation rate constant is 0.008 h^-1。

Example 5:

0.3g of synthesized 0.1Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.1166 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a dropping rate of 3 mL/min, at which time the stirring was vigorous at 1200 revolutions per minute. Stirring is continued for 15h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 4h, and obtaining the content Pt: 0.1 percent; ga: 5 percent; al: 43.6 percent(ii) a Si: 5 percent; o: 46.3% catalyst, reported as 5% Si @0.1Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 5% Si @0.1Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC and maintaining for 2h, then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 22.3 percent, the selectivity of propylene is 93.0 percent, and the inactivation rate constant is 0.016 h^-1。

Example 6:

commercial gamma-Al₂O₃In the air by 5^oThe temperature rise rate of C/Min is increased to 700^oAnd C, maintaining for 2 hours, and vacuumizing for 2 hours by using a vacuum oven under the pressure of 0.01MPa for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，0.5868gGa(NO₃)₃·xH₂O was dissolved in 2.5 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A. Dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after the dropwise adding is completed, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting into an oven 80^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.1Pt8Ga/Al₂O₃。

0.3g of synthesized 0.1Pt8Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 1mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.1166 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a dropping rate of 3 mL/min, at which time the stirring was vigorous at 1200 revolutions per minute. Stirring is continued for 15h after the dripping is finished. The solution is then washed with 4Centrifuging at 000 rpm, placing in oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 4h, and obtaining the content Pt: 0.1 percent; ga: 8 percent; al: 41.5 percent; si: 5 percent; o: 45.4% catalyst, reported as 0.5% Si @0.1Pt8Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 0.5% Si @0.1Pt8Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 22.8 percent, the selectivity of propylene is 90.8 percent, and the inactivation rate constant is 0.019 h^-1。

Example 7:

commercial gamma-Al₂O₃In the air by 5^oThe temperature rise rate of C/Min is increased to 700^oAnd C, maintaining for 2 hours, and vacuumizing for 2 hours by using a vacuum oven under the pressure of 0.01MPa for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，7.33gGa(NO₃)₃·xH₂O was dissolved in 250 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A. Taking 2.5 mL of solution A, dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after completely dropwise adding, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting the beaker into an oven 80%^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.001Pt1Ga/Al₂O₃。

0.3g of synthesized 0.001Pt1Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 1mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. Then 0.0116g of TEOS was weighed and dissolved in 20mL of absolute ethanolAnd is referred to as D solution. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 5 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 10h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 2h, obtaining the content Pt: 0.001 percent; ga: 1 percent; al: 51.635 percent; si: 0.5 percent; o: 46.864% catalyst, reported as 0.5% Si @0.001Pt1Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 0.5% Si @0.001Pt1Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC and maintaining for 2h, then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. Propane conversion rate 12.3%, propylene selectivity 84.7%, deactivation rate constant 0.087 h^-1。

Example 8:

0.3g of synthesized 0.1Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.2332 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 2 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 18h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 2 degrees of stirring in air^oThe temperature rise rate of C/Min is increased to 400^oC, maintaining for 3 hours, and obtaining the content Pt: 0.1 percent; ga: 5 percent; al: 37.9 percent; si: 10 percent; o: 47.0% catalyst, reported as 10% Si @0.1Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 10% Si @0.1Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. Propane conversion 21.3%, propylene selectivity 91.6%, deactivation rate constant 0.025 h^-1。

Example 9:

0.3g of synthesized 0.1Pt5Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.4664g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 1 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 20h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 2 degrees of stirring in air^oThe temperature rise rate of C/Min is increased to 400^oC, maintaining for 4h, and obtaining the content Pt: 0.1 percent; ga: 5 percent; al: 26.6 percent; si: 20 percent; o: 48.3% catalyst, reported as 20% Si @0.1Pt5Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 20% Si @0.1Pt5Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 20.0 percent, the selectivity of propylene is 89.4 percent, and the inactivation rate constant is 0.058 h^-1。

Example 10:

commercial gamma-Al₂O₃In the air by 5^oThe temperature rise rate of C/Min is increased to 700^oAnd C, maintaining for 2 hours, and vacuumizing for 2 hours by using a vacuum oven under the pressure of 0.01MPa for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，7.33gGa(NO₃)₃·xH₂O was dissolved in 250 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A.Taking 2.5 mL of solution A, dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after completely dropwise adding, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting the beaker into an oven 80%^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.001Pt1Ga/Al₂O₃。

0.3g of synthesized 0.001Pt1Ga/Al was weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.4664g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 1 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 20h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 2 degrees of stirring in air^oThe temperature rise rate of C/Min is increased to 400^oC, maintaining for 4h, and obtaining the content Pt: 0.001 percent; ga: 1 percent; al: 29.524%%; si: 20%%; o: 49.475% catalyst, noted 20% Si @0.001Pt1Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 20% Si @0.001Pt1Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity of 1.2 h)^-1) Catalytic evaluation was performed. 4.6 percent of propane conversion rate, 89.2 percent of propylene selectivity and 0.068 h of inactivation rate constant^-1。

Example 11:

commercial gamma-Al₂O₃In the air with 1^oThe temperature rise rate of C/Min is increased to 700^oAnd C, maintaining for 3 hours, and vacuumizing for 2 hours in a vacuum oven under the pressure of 0.01MPa for later use. Firstly weighing 2g of calcined gamma-Al₂O₃Put in a 50 mL beaker, and 0.0040g of Pt (NH) was weighed₃)₄(NO₃)₂，0.7336gGa(NO₃)₃·xH₂O was dissolved in 2.5 mL of water to prepare a mixed salt aqueous solution of Pt and Ga, which was designated as solution A. Dropwise adding the solution A into a beaker by using a 100 uL liquid transfer gun, stirring by using a glass rod while dropwise adding, continuously stirring for 1h after the dropwise adding is completed, sealing the beaker by using a sealing film, standing for 3h at room temperature, and putting into an oven 80^oAnd C, 12 h. Drying, grinding, and air drying at a speed of 5%^oThe temperature rise rate of C/Min is increased to 500^oC, maintaining for 3 hours, and recording the obtained medicine as 0.1Pt10Ga/Al₂O₃。

0.3g of synthetic 0.1Pt10Ga/Al are weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 1mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. Then, 0.0116g of TEOS was weighed and dissolved in 20mL of absolute ethanol and the solution was designated as D solution. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 5 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 10h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 2h, obtaining the content Pt: 0.1 percent; ga: 10 percent; al: 45.2 percent; si: 0.5 percent; o: 44.2% catalyst, reported as 0.5% Si @0.1Pt10Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 0.5% Si @0.1Pt10Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity 3 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 18.7 percent, the selectivity of propylene is 88.3 percent, and the inactivation rate constant is 0.023 h^-1。

Example 12:

0.3g of synthetic 0.1Pt10Ga/Al are weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 1mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.0583 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 4 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 12h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 3 hours, and obtaining the content Pt: 0.1 percent; ga: 10 percent; al: 42.9 percent; si: 2.5 percent; o: 44.5% catalyst, reported as 2.5% Si @0.1Pt10Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 2.5% Si @0.1Pt10Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen gas= 1: 1 (space velocity 3 h)^-1) Catalytic evaluation was performed. Propane conversion rate is 20.3%, propylene selectivity is 93.8%, and deactivation rate constant is 0.012 h^-1。

Example 13:

0.3g of synthetic 0.1Pt10Ga/Al are weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.1166 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a dropping rate of 3 mL/min, at which time the stirring was vigorous at 1200 revolutions per minute. Stirring is continued for 15h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 1 in air^oThe temperature rise rate of C/Min is increased to 350^oC, maintaining for 4h, and obtaining the content Pt: 0.1 percent; ga: 10 percent; al: 40.1 percent; si: 5 percent; o: 44.8% catalyst, reported as 5% Si @0.1Pt10Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 5% Si @0.1Pt10Ga/Al₂O₃The catalyst and 0.5 g (40-60 meshes) of quartz sand are mixedAfter being evenly mixed, the mixture is filled into the middle section of a quartz tube of a fixed bed with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity 3 h)^-1) Catalytic evaluation was performed. Propane conversion rate is 20.5%, propylene selectivity is 91.3%, and deactivation rate constant is 0.026 h^-1。

Example 14:

0.3g of synthetic 0.1Pt10Ga/Al are weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.2332 g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 2 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 18h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. After grinding, the mixture is treated with 2 degrees of stirring in air^oThe temperature rise rate of C/Min is increased to 400^oC, maintaining for 3 hours, and obtaining the content Pt: 0.1 percent; ga: 10 percent; al: 34.4 percent; si: 10 percent; o: 45.5% catalyst, reported as 10% Si @0.1Pt10Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 10% Si @0.1Pt10Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity 3 h)^-1) Catalytic evaluation was performed. Propane conversion 19.7%, propylene selectivity 88.9%, deactivation rate constant 0.041 h^-1。

Example 15:

0.3g of synthetic 0.1Pt10Ga/Al are weighed₂O₃The catalyst was put into a 100 mL round-bottom flask, and 40 mL of absolute ethanol and 2 mL of concentrated aqueous ammonia were added thereto, and the mixture was sonicated for 30 Min and recorded as solution C. 0.4664g of TEOS was weighed out and dissolved in 20mL of absolute ethanol and recorded as solution D. Solution D was drawn into a syringe and added to the round bottom flask containing solution A using a micro syringe pump at a 1 mL/min drop rate with vigorous stirring at 1200 rpm. Stirring is continued for 20h after the dripping is finished. The solution was then centrifuged at 4000 rpm and placed in an oven 80^oAnd C, 12 h. GrindingThen in air by 2^oThe temperature rise rate of C/Min is increased to 400^oC, maintaining for 4h, and obtaining the content Pt: 0.1 percent; ga: 10 percent; al: 23.1 percent; si: 20 percent; o: 46.8% catalyst, reported as 20% Si @0.1Pt10Ga/Al₂O₃. Granulating into 40-60 mesh.

In a fixed bed, 0.1 g (40-60 mesh) of 20% Si @0.1Pt10Ga/Al₂O₃The catalyst is evenly mixed with 0.5 g (40-60 meshes) of quartz sand and then is filled into the middle section of a fixed bed quartz tube with the inner diameter of 6 mm. Under pure argon (20 mL. min)^-1) Under the condition of raising the temperature of the reactor bed to 450 deg.C^oC, maintaining for 1h, and then introducing propane: hydrogen = 1: 1 (space velocity 3 h)^-1) Catalytic evaluation was performed. The conversion rate of propane is 17.9 percent, the selectivity of propylene is 79.8 percent, and the inactivation rate constant is 0.053 h^-1。

FIG. 1 (a-d) 2.5% Si @0.1Pt5Ga/Al after reaction₂O₃Spherical aberration electron micrographs of the catalyst. Fig. a shows that the Ga metal clusters are uniformly dispersed on the surface of the catalyst by a spherical aberration electron microscope dark field graph; according to the atomic number contrast mechanism, isolated bright points in the clusters are Pt active sites, and Ga species are darker around the bright points; and d is a spherical aberration electron microscope bright field image, according to the atomic number contrast mechanism, isolated dark points in the cluster are Pt active sites, and the dark points around the bright points are Ga species.

FIG. 2 (a-c) 0.1Pt5Ga/Al after reaction₂O₃2.5% Si @0.1Pt5Ga/Al after reaction of catalyst and (d-f)₂O₃Spherical aberration electron micrographs of the catalyst. FIG. (a-c) shows 0.1Pt5Ga/Al after reaction₂O₃The PtGa clusters of the catalyst are significantly agglomerated, and the graphs (d-f) show 2.5% Si @0.1Pt5Ga/Al after the reaction₂O₃The catalyst retained highly dispersed PtGa clusters. The comparison shows that highly dispersed Pt sites are anchored by Ga while being effectively restricted from migration by the silica shell.

FIG. 3 (a-b) 0.1Pt5Ga/Al after reaction₂O₃2.5% Si @0.1Pt5Ga/Al after reaction of catalyst and (c-d)₂O₃Electron microscopy of the catalyst, (a-b) dotted micro Al₂O₃Boundary, (c-d) dotted line is epitaxialA long silica shell. The silicon dioxide shell layer grows at 0.1Pt5Ga/Al₂O₃The surface of the catalyst.

FIG. 4 (a-f) 2.5% Si @0.1Pt5Ga/Al after reaction₂O₃The spherical aberration electron microscope picture of the catalyst shows that the elements Si, Ga, Al and Pt are uniformly dispersed on the surface, and the silicon dioxide shell layer is tightly wrapped on the PtGa/Al₂O₃The surface of the catalyst.

Figure 5 (a-b) DRIFT-CO plot of the catalyst after reaction, illustrating that the Pt sites are still present as highly dispersed Pt sites after reaction and the peaks are shifted due to the interaction of the silica shell and the Pt sites, illustrating that the electronic properties of the Pt sites are modulated.

The catalysts in the above five figures are all catalysts after reaction, which illustrates that highly dispersed Pt sites are anchored on highly dispersed Ga clusters and silicon dioxide shell layers are tightly wrapped on PtGa/Al₂O₃The surface also shows that the silica shell layer can well limit the migration of active sites in the reaction process, thereby playing a role in resisting sintering.

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.

Claims

1. a catalyst for producing propylene by direct dehydrogenation of propane, is characterized in that: the component comprises by mass percentage: Pt: 0.001～0.1%, Ga: 1%～10%, Al: 23.100%～51.635%, Si: 0.5~20%, O: 44.200~49.475%.

2. a method for preparing catalyst as claimed in claim 1, is characterized in that: adopt impregnation-coating method to prepare catalyst, concrete steps are as follows:

1) Raise commercial γ-Al ₂ O ₃ to 700°C at a heating rate of 1~5°C/min in air, maintain for 2~3h, and vacuumize for 2h at a low pressure of 0.01MPa to obtain Al ₂ O ₃ ;

2) Dissolve Ga(NO ₃ ) ₃ ·xH ₂ O and Pt(NH ₃ ) ₄ (NO ₃ ) ₂ in water, add dropwise to Al ₂ O ₃ , stand for 2~3 h, dry and grind , calcined to obtain PtGa/Al ₂ O ₃ ;

3) PtGa/Al ₂ O ₃ is added to the mixed solution of ethanol and ammonia water, and ultrasonicated to obtain a suspension;

4) Add the mixed solution of ethyl orthosilicate and ethanol dropwise to the suspension at a rate of 1~5mL/h, stir for 10~20 h, centrifuge, dry at 353 K, grind, and grind at 623~673 K Calcination is carried out in air for 2 to 4 hours to obtain the catalyst for producing propylene by direct dehydrogenation of propane.

3. The method according to claim 2, wherein: in step 2), raw materials are calculated by mass ratio: Pt/Ga=0.0001～0.1, Pt/H ₂ O=0.000008～0.0008, Pt/Al ₂ O ₃ = 0.00001~0.001.

4. method according to claim 2, is characterized in that: in step 3), the volume ratio of ethanol and ammoniacal liquor is 20:1～40:1, and the mass volume ratio of _PtGa / _Al2O3 and ammoniacal liquor is 0.15～0.3 g: 1 mL.

5. method according to claim 2, is characterized in that: in step 4), the mass volume ratio of ethyl orthosilicate and ethanol is 0.0116～ ^0.4664g : 20mL; .

6 . The application of the catalyst according to claim 1 , wherein the catalyst is used in the direct dehydrogenation of propane to produce propylene. 7 .