CN110560055B - Alkane dehydrogenation catalyst, preparation method and application thereof - Google Patents

Abstract

The invention relates to an alkane dehydrogenation catalyst, and a preparation method and application of the catalyst. Specifically, according to the present invention, there is provided an alkane dehydrogenation catalyst wherein a main catalyst metal and a co-catalyst metal are combined on an alumina support, wherein the main catalyst metal is selected from Pt and Pd at a loading of 0.1 to 1.0 wt%, and the co-catalyst metal is selected from Ce and Sn at a loading of 0.5 to 10 wt%, the molar ratio of the main catalyst metal loading to the co-catalyst metal loading is 0.1 to 1 in terms of metal, the alumina support has a spinel structure derived from a hydrotalcite-like compound on the surface, wherein the metal of the hydrotalcite-like compound is selected from Mg and Zn at a loading of 0.5 to 10 wt%, and all loading percentages are in terms of metal on the basis of the entire catalyst.

Description

Alkane dehydrogenation catalyst, preparation method and application thereof

technical field

The present invention relates to an alkane dehydrogenation catalyst and a preparation method and application of the catalyst, in particular to an alkane dehydrogenation catalyst which can be used in a fluidized bed reaction.

Background technique

Propylene is an important petrochemical raw material, which can be used to produce polypropylene, acrylonitrile, butane/octanol and acrylic acid, etc., but it is mainly used to produce polypropylene. The consumption of propylene in this application can account for 70wt% of the total propylene output above.

Polypropylene (PP) is the third largest plastic after polyethylene (PE) and polyvinylchloride (PVC), and its current demand is growing the fastest. Polypropylene is widely used in the manufacture of plastic products, such as household appliances, pipes, packaging films and synthetic fibers, which are closely related to people's production and life, and the demand for these propylene downstream products is also growing rapidly, which will undoubtedly further increase. increased demand for propylene. According to industry reports, in 2011, the total output of propylene in my country was less than 14 million tons, and the import volume was 1.7552 million tons, showing a significant gap in the self-sufficiency rate. Therefore, my country's domestic production capacity of propylene still needs to be further improved.

Direct dehydrogenation of propane to propylene (PDH) is a propylene production technology developed since the 1970s. The obvious advantage of direct propane dehydrogenation technology compared to other propylene production technologies is the high yield and quality of propylene. Specifically, when propane is directly dehydrogenated to propylene, the propane molecule removes two hydrogen atoms under the action of a catalyst to obtain propylene molecules, and the total yield of propylene in this process can be as high as 74-86% (considering the consumption of heating fuel). In addition, due to the simple chemical reaction and few side reactions in the process, the obtained propylene fully conforms to typical polymer-grade propylene specifications after being purified.

At present, mature foreign propane dehydrogenation technologies mainly include UOP's Oleflex process, ABB Lummus Global's Catofin process, Linde AG/BASF's PDH process, Snamprogetti/Yarsintz's FDB-4 process and KruppUhde's STAR process.

Correspondingly, at present, research reports on Pt-Sn-based propane dehydrogenation catalysts supported by alumina mostly focus on the preparation methods of the catalysts, the preparation of additives and active metals, and the like. Although these existing catalysts have good alkane conversion and olefin selectivity under certain reaction conditions, they suffer from poor reaction stability and poor service life due to their easy coke deactivation under high temperature conditions.

In order to improve the reaction stability and service life of alkane dehydrogenation catalysts, it has been found that the use of catalyst supports containing hydrotalcites (LDHs) can provide a good confinement effect on active metals, which can ensure to a certain extent The reaction stability of the catalyst and its service life are correspondingly improved.

Hydrotalcites (LDHs) are inorganic materials with a layered structure. There are strong covalent bonds in the main layer and weak interactions between the layers. In this way, in the LDHs crystal structure, the metal ions can be uniformly distributed on the layer plate, and when used as a catalyst carrier, the active metal can be stably and uniformly distributed, but due to its weak interlayer interaction, it may reduce the overall strength of the catalyst. not enough.

In view of the prior art, the present invention is further improved, and specifically provides an alkane dehydrogenation catalyst. The alumina carrier used in the catalyst has a spinel structure derived from hydrotalcites (LDHs) on the surface, wherein In the process of catalyst preparation, hydrotalcite-like compounds are grown in situ on the surface of the alumina carrier, and the catalytically active components are effectively dispersed during the growth process of the hydrotalcite-like compounds. After final calcination, the effectively dispersed catalytically active components are fixed in the oxidizer On the surface of the aluminum carrier, the surface properties of the catalyst can be changed while ensuring the overall strength of the catalyst, so that the active metal can be evenly distributed on the surface of the catalyst and keep this uniform distribution as much as possible during use, thereby effectively improving the catalyst. Active stability and prolong its service life.

Due to the good overall strength of the catalyst of the present invention, it can not only be used in the existing Catofin process of ABB Lummus Global using a fixed bed and the Oleflex process of UOP using a moving bed, but also ideally can be used for fluidization bed reaction process. Due to the good heat transfer properties of the fluidized bed reactor, isothermal operation can be achieved and heat can be supplied to the propane dehydrogenation reaction by radiation and/or hot particles from an external source, and the recycle flow can also be utilized when the catalyst is deactivated The reaction-regeneration configuration of the chemical bed is used to maintain continuous operation of the process. Undoubtedly, the fluidized bed reactor is more suitable for the strongly endothermic propane dehydrogenation process.

Therefore, the alkane dehydrogenation catalyst of the present invention will have better application prospects.

SUMMARY OF THE INVENTION

According to the present invention, an alkane dehydrogenation catalyst is provided, which uses alumina as a support, and the alumina support has a spinel structure derived from hydrotalcites (LDHs) on its surface, wherein in the catalyst preparation process The hydrotalcite-based compound is grown in situ on the surface of the alumina carrier, and the catalytically active metal is effectively dispersed during the growth of the hydrotalcite-based compound, and the effectively dispersed catalytically active metal is finally fixed on the surface of the alumina carrier after final calcination. This catalyst can be used for the dehydrogenation of saturated alkanes such as C3 and C4 after reduction, and can also be used for the dehydrogenation of such alkanes in a fluidized bed reactor due to its size and strength characteristics.

Specifically, the present invention provides an alkane dehydrogenation catalyst, wherein a main catalyst metal and a promoter metal are combined on an alumina carrier, wherein the main catalyst metal is selected from Pt and Pd, and the loading amount thereof is 0.1-1.0 wt% , the promoter metal is selected from Ce and Sn, its loading is 0.5-10wt%, the molar ratio of the main catalyst metal loading and the promoter metal loading is 0.1-1 in terms of metal, and the alumina carrier Having a spinel structure on the surface derived from a hydrotalcite-like compound, wherein the metal of the hydrotalcite-like compound is selected from Mg and Zn, and its loading is 0.5-10 wt%, and all loading percentages are based on the whole catalyst. Metal count.

According to the present invention, in the alkane dehydrogenation catalyst, the main catalyst metal and the promoter metal are known in the art, for example, the former can be selected from Pt and Pd, preferably Pt, and the latter can be selected from Ce and Sn, preferably Sn, where the procatalyst metal and the cocatalyst metal are used as active metals in association with each other, and the cocatalyst metal assists in dispersing the procatalyst metal to a certain extent, thereby preventing the procatalyst metal to a certain extent. Metals aggregate during use, which can improve catalyst activity and stability.

According to the present invention, in the alkane dehydrogenation catalyst, the molar ratio of the metal loading of the main catalyst to the metal loading of the promoter is 0.1-1, preferably 0.3-0.7, and most preferably about 0.5 in terms of metal. , on the basis of the whole catalyst, in terms of metal, the loading of the main catalyst metal is 0.1-1.0 wt%, preferably 0.2-0.7 wt%, and the loading of the promoter metal is 0.5-10 wt%, preferably 0.8-5.0 wt% , so that the two can interact better and work together as active metals.

According to the present invention, in the alkane dehydrogenation catalyst, the metal that forms the hydrotalcite compound on the surface of the alumina carrier is selected from Mg and Zn, preferably Mg, and the metal loading of the hydrotalcite compound is 0.5-10wt %, preferably 1.5-7.5 wt%, the hydrotalcite-based compound and the spinel structure formed later can also adjust the acid strength of the catalyst surface, thereby reducing the generation of coking during the use of the catalyst, thereby further prolonging the service life of the catalyst.

According to the present invention, in the alkane dehydrogenation catalyst, the main catalyst metal is Pt, the promoter metal is Sn, and the metal of the hydrotalcite compound is Mg, so that the alkane dehydrogenation catalyst is oxidation The aluminum-supported Pt-Sn-Mg catalyst, based on the whole catalyst and calculated as metal, has a Pt loading of 0.1-1.0 wt%, preferably 0.2-0.7 wt%, and a Sn loading of 0.5-10 wt%, preferably 0.8- 5.0wt%, Mg loading is 0.5-10wt%, preferably 1.5-7.5wt%.

The present invention also provides a method for preparing the alkane dehydrogenation catalyst, the method comprising the following steps:

I). Formulating an aqueous solution comprising a procatalyst metal precursor and a cocatalyst metal precursor, wherein the procatalyst metal is selected from Pt and Pd, and the cocatalyst metal is selected from Ce and Sn, and the solution is formulated such that: the The molar ratio of the main catalyst metal loading to the promoter metal loading is 0.1-1, preferably 0.3-0.7 in terms of metal, and the main catalyst metal loading is 0.1-1.0 wt %, preferably 0.2-0.7 wt %, The metal loading of the promoter is 0.5-10 wt%, preferably 0.8-5 wt%, and all loading percentages are based on the whole catalyst as a metal;

II). The solution prepared in step I) is rapidly mixed with a metal water-soluble salt of a hydrotalcite compound, a weakly basic ammonia forming precursor and deionized water at a low temperature to form a mixed solution, wherein the hydrotalcite compound The metal is selected from Mg and Zn, and the mixed solution is prepared so that: the amount of the metal of the hydrotalcite compound and the ammonia forming precursor satisfies that the molar ratio of the metal to the ammonia is 0.05-0.25, preferably 0.05-0.15, The metal loading of the hydrotalcite compound is 0.5-10 wt %, preferably 1.5-7.5 wt %, and all loading percentages are calculated as metals based on the entire catalyst;

III). Add the mixed solution formed in step II) into a hydrothermal kettle containing Al ₂ O ₃ particles, the amount of which is at least immersed in the Al ₂ O ₃ particles, and then seal the hydrothermal kettle for crystallization ;and

IV). Take out the crystallized solid matter in step III), wash with deionized water until neutral, and then dry and calcinate to obtain the alkane dehydrogenation catalyst.

According to the present invention, in the preparation method of the alkane dehydrogenation catalyst, wherein in step I), both the main catalyst metal precursor and the promoter metal precursor can be metal precursors known in the art, The two generally interact with each other to form a complex during the preparation of the aqueous solution. Specifically, the main catalyst metal precursor is selected from the chloric acid of the main catalyst metal and the water-soluble salt of the chloric acid, and the cocatalyst is selected. The metal precursor is selected from the group consisting of chlorides, nitrates and acetates of the promoter metal and acids of the promoter metal and salts thereof.

According to the present invention, in the preparation method of the alkane dehydrogenation catalyst, wherein in step II), the metal water-soluble salt of the hydrotalcite compound and the weakly basic ammonia forming precursor can be the same Common materials in the field, specifically, the water-soluble salt of the metal of the hydrotalcite compound can be the nitrate and chloride of the metal, etc., and the weakly basic ammonia forming precursor is selected from ammonia water, ammonium carbonate , ammonium bicarbonate, hexamethylenetetramine and urea, preferably hexamethylenetetramine and urea.

According to the present invention, in the preparation method of the alkane dehydrogenation catalyst, wherein in step II), the solution prepared in step I) forms a precursor and a metal water-soluble salt of a hydrotalcite compound, weakly basic ammonia and The mixing between deionized water is generally carried out quickly at low temperature, which is mainly to prevent the formation of precipitation in the solution, which is not conducive to the uniform mixing, and also to prevent the formation of ammonia from the precursor of ammonia at a non-low temperature. The rapid mixing is carried out at a temperature of 0-25°C.

According to the present invention, when the prepared alkane dehydrogenation catalyst is a surface-treated alumina-supported Pt-Sn-Mg catalyst, the main catalyst metal is Pt, and the platinum metal precursor is selected from chloroplatinic acid, chloroplatinic acid, Platinum acid and their water-soluble salts such as sodium salt and potassium salt, etc., the promoter metal is Sn, and the tin metal precursor is selected from tin dichloride, tin tetrachloride, tin nitrate, tin acetate and stannic acid and water-soluble salts of stannic acid such as sodium stannate and potassium stannate, etc., the metal of the hydrotalcite compound is Mg, and the water-soluble salts thereof can be magnesium nitrate, magnesium chloride, and the like.

According to the present invention, in the preparation method of the alkane dehydrogenation catalyst, wherein in step III), the amount of the mixed solution added in the hydrothermal kettle at least soaks the Al ₂ O ₃ particles to ensure The Al ₂ O ₃ particle carrier is fully attached to the mixed solution, and the subsequent crystallization process is generally carried out for a suitable period of time at a crystallization temperature commonly used in the art. Preferably, the crystallization temperature is 50-300°C, preferably 100-300°C, and the crystallization time is 1-48h, preferably 6-24h.

According to the present invention, in the crystallization process carried out in step III), the ammonia forming precursor is decomposed to generate ammonia gas, and the ammonia gas acts as a precipitant to make the metal ions of the hydrotalcite compound such as Mg ²⁺ interact with the surface of the alumina particles. The aluminum ions Al ³⁺ combine to form a hydrotalcite-like structure, so that the metal elements of the hydrotalcite-like compound such as Mg are firmly bound on the surface of the alumina support, and the coordination between the main catalyst metal and the promoter metal previously dispersed in the mixed solution Compounds such as Pt-Sn complexes are also highly dispersed and firmly immobilized in the hydrotalcite structure during its formation.

According to the present invention, in the preparation method of the alkane dehydrogenation catalyst, wherein in step III), the alumina particles may be alumina particles commonly used as catalyst supports in the art, which may be commercially available, or may be Prepared by industrial methods, for example, can be prepared by spray granulation, specifically, alumina powder slurry is made into alumina particles at 200-300 °C, followed by calcination at 500-600 °C, and then the desired particle size is screened. Aluminium particles.

Preferably, according to the present invention, the alumina particles are γ-Al ₂ O ₃ microspheres, the particle size distribution of which is preferably between 20-200 μm, more preferably, the particles of the γ-Al ₂ O ₃ microspheres are In the diameter distribution, the particles smaller than 40 μm are not more than 30 wt%, the particles of 40-80 μm are not more than 40 wt%, and the particles larger than 80 μm are not more than 30 wt%.

According to the present invention, in the preparation method of the alkane dehydrogenation catalyst, wherein in step IV), after the crystallization substance is taken out from the hydrothermal kettle, it is first washed with deionized water to neutrality, that is, washed away The excess alkali reaches the pH value of about 7, and the subsequent drying and calcination can be carried out under the temperature and time conditions commonly used in the art. Generally, the calcination temperature of the crystallized material is 400-800 ° C, preferably is 500-700°C, and the calcination time is 1-10h, preferably 2-7h.

According to the present invention, in the calcination process carried out in step IV), the hydrotalcite compound formed before is gradually dehydrated to finally form a spinel structure, and the main catalyst metal and the promoter metal are dispersed and fixed therein at the same time, thereby obtaining the present invention Active metal highly dispersed catalyst for alkane dehydrogenation.

In addition, the present invention also provides the use of the alkane dehydrogenation catalyst, specifically for the dehydrogenation of saturated alkanes such as C3 or C4 into corresponding olefins such as propylene or butene, in particular, the alkane dehydrogenation catalyst of the present invention can be used in Saturated alkanes such as C3 or C4 are dehydrogenated to the corresponding olefins such as propylene or butenes in a fluidized bed reactor.

Taken together, the alkane dehydrogenation catalyst of the present invention can bring the following beneficial effects:

1. Since the hydrotalcite structure is used to make the catalytically active metals highly dispersed, the aggregation of the catalytically active metals is effectively suppressed, so it can suppress the occurrence of side reactions and improve the stability of the catalyst while having good dehydrogenation activity.

2. Since the surface-treated alumina particles of suitable size are used as the carrier, the catalyst has sufficient strength and wear resistance, so it can be used in a fluidized bed reactor, thereby effectively solving the traditional dehydrogenation reaction process. Heat transfer conundrum.

Detailed ways

The present invention is described below by means of examples, which are for illustrative purposes only and the present invention is not limited to these examples.

Example

Example 1

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 20 ml of this solution, and mix it with 0.30 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O, 4.05g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 100° C. for 24 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 1.2 wt %.

Example 2

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 10 ml of this solution, mix it with 0.60 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O, 4.05g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 100° C. for 24 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.2 wt %, the tin content is 1.6 wt %, and the magnesium content is 1.2 wt %.

Example 3

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 40 ml of this solution, and mix it with 0.19 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O, 4.05g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 100° C. for 24 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.8 wt %, the tin content is 0.4 wt %, and the magnesium content is 1.2 wt %.

Example 4

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 20 ml of this solution, and mix it with 0.30 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 1.28g Mg(NO ₃ ) ₂ ·6H ₂ O, 2.00g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 100° C. for 24 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 0.6 wt %.

Example 5

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 20 ml of this solution, and mix it with 0.30 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 12.80 g Mg(NO ₃ ) ₂ ·6H ₂ O, 20.12 g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42 ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 100° C. for 24 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 6 wt %.

Example 6

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 20 ml of this solution, and mix it with 0.30 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O, 4.05g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 50° C. for 48 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 1.2 wt %.

Example 7

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 20 ml of this solution, and mix it with 0.30 g SnCl ₂ to form a Pt-Sn complex solution;

In an ice-water bath, the complex solution was rapidly mixed with 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O, 4.05g urea and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was added to a hydrothermal kettle containing 20 g of γ-Al ₂ O ₃ particles, and then the hydrothermal kettle was sealed and crystallized at 250° C. for 6 h;

The crystallized material was taken out from the hydrothermal kettle, washed with deionized water to pH 7, dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 1.2 wt %.

Comparative Example 1

Prepare 10.62g/LH ₂ PtCl ₆ aqueous solution, pipette 20 ml of this solution, and mix it with 0.30 g SnCl ₂ to form a Pt-Sn complex solution;

The complex solution was rapidly mixed with 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O and a certain amount of deionized water, and then deionized water was added to make the total amount of the mixed solution reach 42ml;

The mixed solution was uniformly mixed with 20 g of γ-Al ₂ O ₃ particles under stirring, then dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 1.2 wt %.

Comparative Example 2

Dissolve 0.30g _SnCl in water to make 42ml solution;

The solution was uniformly mixed with 20 g of γ-Al ₂ O ₃ particles under stirring, then dried, and calcined at 600° C. for 10 h, and the calcined samples were used for later use;

Dissolve 2.56g Mg(NO ₃ ) ₂ ·6H ₂ O in water to make 42ml solution;

The solution was uniformly mixed with the calcined sample under stirring, then dried, and calcined at 600° C. for 10 h, and the calcined sample was used for later use;

Prepare 10.62g/L H ₂ PtCl ₆ aqueous solution, pipette 20ml of the solution, and make it to 42ml;

The solution was uniformly mixed with the secondary calcined sample under stirring, then dried, and calcined at 600° C. for 10 h.

After the platinum component is reduced by hydrogen, a Pt-SnO ₂ -MgO-γ-Al ₂ O ₃ catalyst is obtained, wherein the platinum content is 0.4 wt %, the tin content is 0.8 wt %, and the magnesium content is 1.2 wt %.

The compositions of the catalysts prepared in the above examples and comparative examples are shown in Table 1 below.

Composition of the catalysts prepared in the examples and comparative examples of Table 1

Pt(wt%) Sn(wt%) Mg(wt%) Example 1 0.4 0.8 1.2 Example 2 0.2 1.6 1.2 Example 3 0.8 0.4 1.2 Example 4 0.4 0.8 0.6 Example 5 0.4 0.8 6 Example 6 0.4 0.8 1.2 Example 7 0.4 0.8 1.2 Comparative Example 1 0.4 0.8 1.2 Comparative Example 2 0.4 0.8 1.2

Catalyst performance test

The catalysts prepared in the various examples and comparative examples were subjected to performance tests using laboratory microreactors and propane dehydrogenation based on hydrodehydrogenation. The process conditions of the test are as follows: reaction temperature 400-700°C, reaction pressure 0.05-0.15MPa absolute, propane mass space velocity 1.0-5.0h ^-1 , hydrogen mass space velocity 0.1-1.0h ^-1 .

The specific test process is as follows:

(1), nitrogen replacement: replace the gas in the reactor with nitrogen, sample and detect the gas in the reactor at an interval of 0.1h, until the gas in the reactor is replaced cleanly;

(2), hydrogen reduction: after the replacement is completed, the nitrogen for replacement is cut off and hydrogen is introduced for reduction, the reduction temperature is 500 ° C, the reduction pressure is normal pressure, and the reduction time is 2h;

(3), dehydrogenation reaction: feed propane, adjust the hydrogen to the flow rate suitable for the reaction at the same time, carry out sampling and detection to the gas in the reactor at intervals of 1h, until the catalyst activity is reduced to a certain extent, stop the experiment, and record the reaction result;

Repeat the above steps in sequence after replacing the catalyst.

Table 2 shows the results of the propane dehydrogenation reaction obtained for each catalyst.

Table 2 Propane dehydrogenation reaction results

It can be seen from the data recorded in Table 2 that:

By comparing Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that compared with the two methods of simply mixing the catalyst components and sequentially loading the catalyst components, the method of the present invention is used to fix the catalyst group by forming hydrotalcite when the catalyst is supported. The catalyst with higher conversion rate, comparable selectivity and longer service life can be obtained;

By comparing Example 1, Example 2 and Example 3, it can be known that according to the present invention, when the catalyst component is supported, the molar ratio of the loading of Pt element to Sn element is preferably 0.3-0.7 in terms of metal;

By comparing Example 1, Example 4 and Example 5, it can be seen that according to the present invention, when the catalyst component is supported, the loading amount of Mg element is preferably 1.5-7.5wt%;

By comparing Example 1, Example 6 and Example 7, according to the present invention, in the catalyst preparation process, the crystallization temperature is preferably 100-300°C, and the crystallization time is preferably 6-24h.

Claims (15)

1. An alkane dehydrogenation catalyst, wherein a main catalyst metal and a promoter metal are combined on an alumina carrier, wherein the main catalyst metal is selected from Pt and Pd, and its loading is 0.1-1.0 wt%, and the promoter The catalyst metal is selected from Ce and Sn, its loading is 0.5-10 wt%, the molar ratio of the main catalyst metal loading to the promoter metal loading is 0.1-1 in terms of metal, and the alumina carrier has on the surface A spinel structure derived from a hydrotalcite-like compound, wherein the metal of the hydrotalcite-like compound is selected from Mg and Zn, and its loading is 0.5-10 wt %, and all loading percentages are based on the metal as a whole catalyst, wherein all the loading percentages are based on the metal. The hydrotalcite compound is formed by in-situ growth on the surface of the alumina carrier and then gradually dehydrated by calcination to form a spinel structure. 2. The alkane dehydrogenation catalyst of claim 1, wherein the main catalyst metal is Pt, and its loading is 0.2-0.7 wt %, the co-catalyst metal is Sn, and its loading is 0.8-5 wt %, and the main catalyst is The molar ratio of the catalyst metal loading to the promoter metal loading is 0.3-0.7 in terms of metal, wherein the metal of the hydrotalcite compound is Mg, and its loading is 1.5-7.5 wt%, and all loading percentages are based on the whole catalyst as Benchmarks are in metal. 3. The alkane dehydrogenation catalyst of claim 1 or 2, wherein the alumina carrier is γ-Al ₂ O ₃ microspheres with a particle size distribution between 20-200 μm. 4. The alkane dehydrogenation catalyst of claim 3, wherein in the particle size distribution of the γ-Al ₂ O ₃ microspheres, particles smaller than 40 μm are not greater than 30 wt %, particles 40-80 μm are greater than 40 wt %, and greater than 80 μm The particles are not more than 30wt%. 5. A method for preparing an alkane dehydrogenation catalyst, the method comprising the steps of: I). Formulating an aqueous solution comprising a procatalyst metal precursor and a cocatalyst metal precursor, wherein the procatalyst metal is selected from Pt and Pd, and the cocatalyst metal is selected from Ce and Sn, and the solution is formulated such that: the The molar ratio of the main catalyst metal loading to the promoter metal loading is 0.1-1 in terms of metal, the main catalyst metal loading is 0.1-1.0 wt%, the promoter metal loading is 0.5-10 wt%, all The percentage of loading is calculated as metal on the basis of the whole catalyst; II). The solution prepared in step I) is rapidly mixed with a metal water-soluble salt of a hydrotalcite compound, a weakly basic ammonia forming precursor and deionized water at a low temperature to form a mixed solution, wherein the hydrotalcite compound The metal is selected from Mg and Zn, and the mixed solution is prepared so that: the amount of the metal of the hydrotalcite compound and the ammonia forming precursor satisfies that the molar ratio of metal to ammonia is 0.05-0.25, and the hydrotalcite compound The loading of the metal is 0.5-10 wt%, and all loading percentages are based on the metal as a whole catalyst; III). Add the mixed solution formed in step II) into a hydrothermal kettle containing Al ₂ O ₃ particles, the amount of which is at least immersed in the Al ₂ O ₃ particles, and then seal the hydrothermal kettle for crystallization ;and IV). Take out the crystallized solid matter in step III), wash with deionized water until neutral, and then dry and calcinate to obtain the alkane dehydrogenation catalyst. 6. The method of claim 5, wherein in step 1), the molar ratio of the main catalyst metal loading to the promoter metal loading is 0.3-0.7 in terms of metal, and the main catalyst metal loading is 0.2-0.7 wt%, the loading amount of the promoter metal is 0.8-5wt%, the main catalyst metal precursor is selected from the chloric acid of the main catalyst metal and the water-soluble salt of the chloric acid, and the promoter The metal precursor is selected from the group consisting of chlorides, nitrates and acetates of the promoter metal and acids of the promoter metal and salts thereof. 7. The method of claim 6, wherein in step 1), the main catalyst metal is Pt, the platinum metal precursor is selected from the group consisting of chloroplatinic acid, chloroplatinous acid and their water-soluble salts, the cocatalyst The metal is Sn, and the tin metal precursor is selected from tin dichloride, tin tetrachloride, tin nitrate, tin acetate, and water-soluble salts of stannic acid and stannic acid. 8. The method of any one of claims 5-7, wherein in step II), the solution prepared in step I) forms a precursor and deionized water with a water-soluble salt of a metal of a hydrotalcite compound, weakly basic ammonia Rapid mixing at a temperature of 0-25° C. to form a mixed solution, wherein the amount of the metal of the hydrotalcite-based compound and the ammonia-forming precursor satisfies that the molar ratio of metal to ammonia is 0.05-0.15, and the hydrotalcite-based compound is The loading amount of the metal is 1.5-7.5wt%, the water-soluble salt of the metal of the hydrotalcite compound is selected from the nitrates and chlorides of the metal, and the ammonia forming precursor is selected from ammonia water, ammonium carbonate, Ammonium bicarbonate, hexamethylenetetramine and urea. 9. The method of claim 8, wherein in step II), the metal of the hydrotalcite compound is Mg, its water-soluble salt is selected from magnesium nitrate and magnesium chloride, and wherein the weakly basic ammonia forming precursor is selected from the group consisting of: From hexamethylenetetramine and urea. 10. The method of any one of claims 5-7, wherein in step III), the crystallization temperature is 50-300° C., the crystallization time is 1-48 h, and the alumina particles are γ-Al ₂ O ₃ Microspheres with a particle size distribution between 20-200 μm. 11. The method of claim 10, wherein in step III), the crystallization temperature is 100-300 ° C, the crystallization time is 6-24 h, and in the particle size distribution of the γ-Al ₂ O ₃ microspheres, less than No more than 30 wt % of 40 μm particles, no more than 40 wt % of 40-80 μm particles, and no more than 30 wt % of particles greater than 80 μm. 12. The method of any one of claims 5-7, wherein in step IV), the calcination temperature is 400-800°C, and the calcination time is 1-10 h. 13. The method of claim 12, wherein in step IV), the calcination temperature is 500-700°C, and the calcination time is 2-7h. 14. Use of the alkane dehydrogenation catalyst of any one of claims 1 to 4 or the alkane dehydrogenation catalyst prepared by the process of any one of claims 5 to 13 for the dehydrogenation of C3 or C4 alkanes to the corresponding propylene or butane ene. 15. The use of claim 14, wherein a fluidized bed reactor is used to dehydrogenate C3 or C4 alkanes to the corresponding propylene or butenes.