Tandem catalyst as well as preparation method and application thereof

Abstract

The invention discloses a series catalyst as well as a preparation method and application thereof, and belongs to the technical field of CO2-assisted propane dehydrogenation new energy. The tandem catalyst is prepared from the following components in percentage by mass: 20-40% of a Pt-based propane dehydrogenation catalyst, 20-40% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 2-10% of an auxiliary agent and the balance of a stabilizer, totaling 100%. The tandem catalyst provided by the invention is wide in component source, can activate propane and CO2 molecules at the same time, has excellent propane conversion per pass and propylene yield, and also has stability under related industrial conditions.

Description

Technical Field

[0001] The present invention relates to the field of new energy technology for CO2-assisted propane dehydrogenation, and more specifically to a series catalyst and a preparation method and application thereof. Background Art

[0002] Propylene is an important basic chemical raw material, and its production capacity is an important indicator of a country's industrial level. The production process of propylene includes catalytic cracking, steam cracking, coal / methanol to propylene and propane dehydrogenation, among which the reaction equation of propane dehydrogenation to propylene (PDH) is C3H8=C3H6+H2. Compared with other propylene production technologies, propane dehydrogenation to propylene has the advantages of high product yield, simple route and low energy consumption. In recent years, propane oxygen-free dehydrogenation to propylene units have been industrialized in some areas, but in actual operation, propane oxygen-free dehydrogenation is a strong endothermic reaction, and the propane conversion rate and propylene single-pass yield are limited by thermodynamic equilibrium. Therefore, in actual operation, it is generally necessary to increase the operating temperature to increase the propane conversion rate. However, the high operating temperature makes the precious metal Pt-based catalyst easily deactivated by sintering and carbon deposition, thus requiring frequent regeneration and replacement.

[0003] As a weak oxidant, CO2 can consume the hydrogen produced by propane dehydrogenation through reverse water gas shift reaction (RWGS), and the reaction equation is CO2+H2=CO+H2O, pushing the thermodynamic equilibrium of propane dehydrogenation to the direction of propylene production. Therefore, compared with propane anaerobic dehydrogenation, CO2-assisted propane dehydrogenation has higher dehydrogenation efficiency and energy utilization. CO2 can also remove carbon deposits in situ through Boudouard reaction, and the reaction equation is CO2+C=2CO, which can extend the service life of precious metal catalysts. In addition, it is of great significance to convert greenhouse gas CO2 into CO as a C1 raw material to directly react with propylene and hydrogen in the reaction system for hydroformylation. Since the catalytic sites of propane dehydrogenation and RWGS are independent of each other during the reaction process, and propane and CO2 are both inert molecules, it is difficult for both to be activated at the same time even at high temperatures.

[0004] Patent CN114602495B discloses a method for preparing a Pt-based catalyst for propane oxygen-free dehydrogenation. MeO is first synthesized by a uniform precipitation method. x -Al2O3 composite oxide, and then Sn, Ga, In, Zn and other additives and active component Pt are introduced on the composite oxide carrier by impregnation method. This catalyst improves the dispersibility and electronic structure of Pt and enhances the catalyst's anti-sintering ability.

[0005] Patent CN114570415B discloses a method for preparing a Pt@multi-level pore zeolite catalyst. In this process, a zeolite precursor, a Pt compound and an auxiliary metal compound are simultaneously added to the zeolite precursor. The synthesized molecular sieve-confined Pt-based catalyst has excellent high-temperature stability and anti-carbon deposition ability.

[0006] Patent CN117046504A discloses a method for preparing a molecular sieve-confined Pt-based bimetallic catalyst. The method comprises the steps of mixing and stirring a silicon source, an organic base, a Pt precursor, a Sn precursor and deionized water, adding an aqueous ammonium fluoride solution, stirring to gel, and then standing and crystallizing to obtain a Pt-based bimetallic catalyst. The catalyst has good stability at high temperatures.

[0007] Although the catalysts in the above three patents have good stability and resistance to carbon deposition, the conversion rate of propane and the yield of propylene are still limited by thermodynamic equilibrium and are at a relatively low level.

[0008] Patent CN109126855B uses high-temperature pyrolysis to synthesize GaN for CO2-assisted propane dehydrogenation. The catalyst preparation process is simple, but the catalyst GaN is difficult to activate propane and CO2 at the same time, resulting in a low single-pass yield of propylene. Therefore, it is urgent to research and develop a green, efficient, stable, and integrated catalyst that can activate propane and CO2 at the same time. Summary of the invention

[0009] In view of the above problems, the present invention provides a tandem catalyst and a preparation method and application thereof. The components of the tandem catalyst provided by the present invention have a wide range of sources, can simultaneously activate propane and CO2 molecules, have excellent propane single-pass conversion rate and propylene yield, and the tandem catalyst is stable.

[0010] The first object of the present invention is to provide a tandem catalyst, which is made of the following components in percentage by mass: 20-40% of a Pt-based propane dehydrogenation catalyst, 20-40% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 2-10% of an auxiliary agent, and the rest being a stabilizer, which totals 100%.

[0011] For example, the mass percentage of the Pt-based propane dehydrogenation catalyst is 20%, 25%, 30%, 35%, 40%, etc.; but it is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0012] The mass percentage of the alkaline earth metal carbonate CO2 hydrogenation catalyst is 20%, 25%, 30%, 35%, 40%, etc.; but it is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0013] The mass percentage of the additive is 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.; but it is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0014] In a preferred embodiment of the present invention, the preparation method of the Pt-based propane dehydrogenation catalyst is:

[0015] The platinum salt and the auxiliary metal precursor are dissolved in water, the pH is adjusted to 1-6, gas phase silica is added, the mixture is stirred for aging, and the mixture is dried and then calcined to obtain a Pt-based propane dehydrogenation catalyst.

[0016] For example, the pH value is adjusted to 1, 2, 3, 4, 5, 6, etc., but it is not limited to the listed values, and other values ​​not listed within the above value range are also applicable.

[0017] In a preferred embodiment of the present invention, the auxiliary metal is Sn, Zn, Ga, Cu or In.

[0018] In a preferred embodiment of the present invention, the aging time is 12h to 48h; the calcination time is 2 to 16h. For example, the stirring time is 12h, 18h, 24h, 30h, 36h, 42h or 48h, and the calcination time is 2h, 4h, 6h, 8h, 10h, 12h, 14h, 16h, etc., but it is not limited to the listed values, and other values ​​not listed in the above value range are also applicable.

[0019] In a preferred embodiment of the present invention, the preparation method of the alkaline earth metal carbonate CO2 hydrogenation catalyst is:

[0020] The hydroxide of the alkaline earth metal is dissolved in water, CO2 is introduced to cause a carbonization reaction to generate carbonate, and after aging, an alkaline earth metal carbonate CO2 hydrogenation catalyst is obtained.

[0021] In a preferred embodiment of the present invention, the auxiliary agent is potassium carbonate and / or sodium carbonate.

[0022] In a preferred embodiment of the present invention, the stabilizer is Al oxide and / or Si oxide.

[0023] A second object of the present invention is to provide a method for preparing the above-mentioned tandem catalyst, comprising the following steps:

[0024] A Pt-based propane dehydrogenation catalyst, an alkaline earth metal carbonate CO2 hydrogenation catalyst, an auxiliary agent and a stabilizer are mixed and ball milled to obtain a tandem catalyst.

[0025] In a preferred embodiment of the present invention, the ball milling time is 2h to 4h, for example, the ball milling time is 2h, 2.5h, 3h, 3.5h, 4h, etc.; but it is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0026] The third object of the present invention is to provide the application of the above-mentioned tandem catalyst in CO2-assisted propane dehydrogenation to propylene.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The tandem catalyst prepared by the present invention is made of a Pt-based propane dehydrogenation catalyst, an alkaline earth metal carbonate CO2 hydrogenation catalyst, an auxiliary agent and a stabilizer, and the raw material source is extensive, the Pt-based propane dehydrogenation catalyst is used for the adsorption activation of propane, and the alkaline earth metal carbonate CO2 hydrogenation catalyst is used to activate the CO2 molecule, thereby achieving the simultaneous activation of propane and CO2 molecules, and the thermodynamic equilibrium of the propane dehydrogenation reaction is pulled by CO2 consumption of hydrogen, thereby improving the propane per-pass conversion rate and propylene yield, and therefore, the tandem catalyst prepared by the present invention has high efficiency. The addition of the stabilizer can ensure that the components are in contact with each other without falling off, and do not agglomerate at high temperature, and improve the mechanical strength of the overall catalyst and facilitate the mass transfer and diffusion of the gas on the tandem catalyst during the reaction. The role of the auxiliary metal is to regulate the geometric structure and electronic structure of the Pt site in the Pt-based propane dehydrogenation catalyst to promote the adsorption of propane and the desorption of propylene, which is beneficial to avoid deep dehydrogenation reactions and alleviate carbon deposition on the catalyst surface. In addition, CO2 and alkaline earth metal carbonate CO2 hydrogenation catalysts remove carbon deposition in situ through the Boudouard reaction, and the reaction equation is CO2+C=2CO, so that the tandem catalyst has high-temperature stability. The addition of the stabilizer improves the dispersion and mechanical strength of the catalytic sites, making the structure of the tandem catalyst not easy to sinter, and ultimately makes the tandem catalyst prepared by the present invention stable.

[0029] The Pt-based propane dehydrogenation catalyst in the series catalyst used in the present invention is an industrialized propane oxygen-free dehydrogenation catalyst, which has abundant market sources and is convenient for direct purchase. The synthesis process of the CO2 hydrogenation catalyst is simple, and the alkaline earth metal hydroxide can be directly obtained by dissolving the corresponding oxide in water. Taking calcium carbonate as an example, the initial raw material is limestone, which is calcined to obtain calcium oxide, which is dissolved in water to obtain calcium hydroxide, and then CO2 gas is introduced to obtain the product.

[0030] The tandem catalyst provided by the present invention exhibits excellent propane single-pass conversion rate and propylene yield in the CO2-assisted propane dehydrogenation process. The propane conversion rate is 50% to 58% at 550°C, the propylene selectivity is not less than 96%, the continuous operation time is greater than 50 hours, and the catalyst performance is completely restored after the carbon deposits are removed by oxygen. It has excellent high-temperature stability and cyclic regeneration ability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 These are the XRD spectra of propane dehydrogenation performance of PtSn / SiO2 catalyst (a) and PtSn / SiO2 catalyst coupled in series with calcium carbonate (b) before and after the reaction.

[0032] Figure 2 This is a high-resolution electron microscope spectrum of PtSn / SiO2 catalyst serially coupled with calcium carbonate, where a is the spectrum at one shooting angle and b is the spectrum at another shooting angle.

[0033] Figure 3 This is a structural diagram of the propane dehydrogenation performance of PtSn / SiO2 catalyst coupled in series with calcium carbonate.

[0034] Figure 4 It is the test spectrum of gas chromatography during the propane dehydrogenation performance test of PtSn / SiO2 catalyst coupled in series with calcium carbonate, wherein a is the spectrum obtained by detection based on the first hydrogen flame ionization detector, b is the spectrum obtained by testing based on the second hydrogen flame ionization detector, and c is the spectrum obtained by detection based on the thermal conductivity detector. DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The present invention provides a series catalyst for coupling a propane dehydrogenation reaction with a RWGS reaction, so as to realize the simultaneous activation of propane and CO2 molecules, and drive the thermodynamic equilibrium of the propane dehydrogenation reaction by consuming hydrogen through CO2, thereby improving the single-pass conversion rate of propane and the yield of propylene. The series catalyst is made of the following components in mass percentage: 20-40% of a Pt-based propane dehydrogenation catalyst, 20-40% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 2-10% of an auxiliary agent, and the rest of a stabilizer, which is 100% in total.

[0037] The tandem catalyst of the present invention is mainly used for the adsorption and activation of propane by using Pt-based propane dehydrogenation catalysis as a propane dehydrogenation catalyst, breaking the CH bond of propane, generating propylene, and coupling alkaline earth metal carbonate CO2 hydrogenation catalyst in series. The Pt-based propane dehydrogenation catalyst is closely connected with the alkaline earth metal carbonate CO2 hydrogenation catalyst in nanometer size, and the alkaline earth metal carbonate promotes the transfer of hydrogen by activating CO2 molecules, drives the transfer of hydrogen species in time and consumes, and can improve the reaction rate of CO2 and hydrogen for the reverse water gas reaction. This tandem coupled catalytic system can promote the consumption of CO2 to produce hydrogen species for propane dehydrogenation, thereby promoting the movement of the thermodynamic equilibrium of propane dehydrogenation, and increasing the per-pass conversion rate of propane and the per-pass yield of propylene in actual production. The addition of stabilizer can ensure that each component contacts each other without falling off, does not reunite at high temperature, and improves the mechanical strength of the overall catalyst and is conducive to the mass transfer and diffusion of gas on the tandem catalyst during the reaction. The effect of the auxiliary agent is to promote the adsorption of propane and the desorption of propylene by the Pt-based propane dehydrogenation catalyst through electronic interaction, which is conducive to alleviating the carbon deposition of the catalyst.

[0038] Further, the preparation method of the Pt-based propane dehydrogenation catalyst is:

[0039] The platinum salt and the auxiliary metal precursor are dissolved in water, the pH is adjusted to 6, fumed silica is added, the mixture is stirred and aged, and calcined after drying. During the preparation process, the platinum in the platinum salt and the metal in the auxiliary metal precursor are reduced and calcined by hydrogen to form nano alloy particles, thereby preparing a Pt-based propane dehydrogenation catalyst.

[0040] The molar ratio of the platinum salt to the nonferrous metal is 0.5 to 2:1.

[0041] The platinum salt is chloroplatinic acid.

[0042] The auxiliary metal precursor is a chloride, a nitrate, etc., for example, tin chloride pentahydrate, zinc nitrate heptahydrate, gallium nitrate nonahydrate, copper nitrate trihydrate, indium nitrate hexahydrate.

[0043] Furthermore, the auxiliary metal is Sn, Zn, Ga, Cu or In.

[0044] Furthermore, the stirring time is 12 h to 48 h; furthermore, the stirring time is 36 h.

[0045] Furthermore, the calcination time is 2 to 16 hours, and furthermore, the calcination time is 8 hours.

[0046] Furthermore, the alkaline earth metal carbonate CO2 hydrogenation catalyst is magnesium carbonate, calcium carbonate, strontium carbonate or barium carbonate, and the preparation method is:

[0047] The hydroxide of alkaline earth metal is dissolved in water, CO2 is introduced to cause carbonization reaction to generate carbonate, and the CO2 hydrogenation catalyst is obtained after aging and standing for 24h to 48h.

[0048] Taking the reaction of CO2 and calcium hydroxide to produce calcium carbonate as an example, the reaction equation is CO2+Ca(OH)2=CaCO3+H2O.

[0049] Furthermore, the CO2 introduction rate is 100-200 mL / min, more preferably, the CO2 introduction rate is 150 mL / min; the carbonization temperature is 20-40°C, more preferably, the carbonization temperature is 30°C; the carbonization time is 1-2 hours, more preferably, the carbonization time is 1.5h.

[0050] Furthermore, the auxiliary agent is potassium carbonate and / or sodium carbonate. Potassium carbonate and / or sodium carbonate are cheap and readily available, thus reducing the preparation cost.

[0051] When selecting a stabilizer, the present invention needs to consider the mechanical strength, hardness and specific surface area of ​​the stability, and Al oxide and Si oxide have high mechanical strength, high hardness and large specific surface area. Furthermore, the stabilizer is Al oxide and / or Si oxide.

[0052] The present invention also provides a method for preparing the above-mentioned tandem catalyst, characterized in that it comprises the following steps:

[0053] The Pt-based propane dehydrogenation catalyst, the alkaline earth metal carbonate CO2 hydrogenation catalyst, the additive and the stabilizer are mixed and ball-milled to obtain a tandem catalyst. The mechanical ball milling method is used to enhance the contact between the components through the strong force generated by the high-speed collision of the ball milling beads, which can increase the interaction between the components.

[0054] The ball milling time is 2 h to 4 h, and more preferably, the ball milling time is 3 h.

[0055] The fumed silica used in the present invention was purchased from Aladdin Reagent Platform and has a specific surface area of ​​300 m 2 / g~350m 2 / g, and the particle size is 7nm-40nm. The concentrated sulfuric acid used in the present invention is commercially available, and the concentration of the concentrated sulfuric acid is 18.4mol / L.

[0056] Example 1

[0057] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 30% of a Pt-based propane dehydrogenation catalyst, 30% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 34% of a stabilizer.

[0058] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0059] 1.3 g of chloroplatinic acid and 2.4 g of tin tetrachloride pentahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged at room temperature for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0060] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0061] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0062] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0063] The tandem catalyst was prepared according to the following steps:

[0064] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 h using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0065] In the series catalyst of Example 1, the Pt-based dehydrogenation catalyst accounts for 30%, the alkaline earth metal carbonate CO2 hydrogenation catalyst accounts for 30%, the auxiliary agent accounts for 6%, and the stabilizer accounts for 34%. The content of the noble metal Pt in the series catalyst measured by ICP-OES is only 0.3%.

[0066] Example 2

[0067] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 30% of a Pt-based propane dehydrogenation catalyst, 30% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 34% of a stabilizer.

[0068] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0069] 1.3 g of chloroplatinic acid and 2.4 g of tin tetrachloride pentahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged at room temperature for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0070] The alkaline earth metal carbonate CO2 hydrogenation catalyst is magnesium carbonate, which is prepared according to the following steps:

[0071] 50g of magnesium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to generate a carbonization reaction to generate magnesium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h, and finally filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid magnesium carbonate.

[0072] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0073] The tandem catalyst was prepared according to the following steps:

[0074] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0075] Example 3

[0076] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 30% of a Pt-based propane dehydrogenation catalyst, 30% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 34% of a stabilizer.

[0077] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0078] 1.3 g of chloroplatinic acid and 0.78 g of zinc nitrate heptahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged at room temperature for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen and argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0079] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0080] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0081] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0082] The tandem catalyst was prepared according to the following steps:

[0083] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0084] Example 4

[0085] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 20% of a Pt-based propane dehydrogenation catalyst, 30% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 44% of a stabilizer.

[0086] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0087] 1.3 g of chloroplatinic acid and 2.4 g of tin tetrachloride pentahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged at room temperature for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0088] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0089] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0090] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0091] The tandem catalyst was prepared according to the following steps:

[0092] According to the above mass percentages, 10 g of Pt-based propane dehydrogenation catalyst, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 22 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 h using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0093] Example 5

[0094] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 20% of a Pt-based propane dehydrogenation catalyst, 40% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 10% of an additive, and 30% of a stabilizer.

[0095] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0096] 1.3 g of chloroplatinic acid and 2 g of indium chloride tetrahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 1, and a mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica, aged at room temperature for 12 h, and then the gel-like solid was transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained product was calcined at 700 ° C for 16 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0097] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0098] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0099] The additives are sodium carbonate and potassium carbonate in a mass ratio of 1:1, and the stabilizer is silicon dioxide.

[0100] The tandem catalyst was prepared according to the following steps:

[0101] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 30 g of CO2 hydrogenation catalyst, 7.5 g of auxiliary potassium carbonate and 22.5 g of stabilizer were weighed and mixed, and then placed in a ball mill and mechanically ball milled for 4 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0102] Example 6

[0103] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 40% of a Pt-based propane dehydrogenation catalyst, 20% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 2% of an auxiliary agent, and 38% of a stabilizer.

[0104] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0105] 1.3 g of chloroplatinic acid and 1.2 g of cupric chloride dihydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 3, and a mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged at room temperature for 48 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 16 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0106] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0107] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0108] The auxiliary agent is sodium carbonate and the stabilizer is aluminum oxide.

[0109] The tandem catalyst was prepared according to the following steps:

[0110] According to the above mass percentages, 30 g of Pt-based propane dehydrogenation catalyst, 15 g of CO2 hydrogenation catalyst, 1.5 g of auxiliary potassium carbonate and 28.5 g of stabilizer were weighed and mixed, and then placed in a ball mill and mechanically milled for 4 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0111] Example 7

[0112] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 30% of a Pt-based propane dehydrogenation catalyst, 30% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 34% of a stabilizer.

[0113] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0114] 1.3 g of chloroplatinic acid and 1.2 g of gallium chloride were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged at room temperature for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0115] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0116] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0117] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0118] The tandem catalyst was prepared according to the following steps:

[0119] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0120] Comparative Example 1

[0121] The comparative example provides a tandem catalyst, which is made of the following components in percentage by mass: a Pt-based propane dehydrogenation catalyst accounts for 43%, an auxiliary agent accounts for 9%, and a stabilizer accounts for 49%.

[0122] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0123] 1.3 g of chloroplatinic acid and 2.4 g of tin tetrachloride pentahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0124] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0125] The tandem catalyst was prepared according to the following steps:

[0126] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar for mechanical ball milling for 3 h. After the ball milling was completed, a tandem catalyst was obtained.

[0127] Comparative Example 2

[0128] The comparative example provides a series catalyst, which is made of the following components in percentage by mass: 30% of a Pt-based propane dehydrogenation catalyst, 30% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 34% of a stabilizer.

[0129] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0130] 1.3 g of chloroplatinic acid was dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0131] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0132] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0133] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0134] The tandem catalyst was prepared according to the following steps:

[0135] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0136] Comparative Example 3

[0137] The comparative example provides a series catalyst, which is made of the following components in percentage by mass: 32% of a Pt-based propane dehydrogenation catalyst, 32% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, and 36% of a stabilizer.

[0138] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0139] 1.3 g of chloroplatinic acid and 2.4 g of tin tetrachloride pentahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0140] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0141] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0142] The stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0143] The tandem catalyst was prepared according to the following steps:

[0144] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 h using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0145] Comparative Example 4

[0146] The comparative example provides a series catalyst, which is made of the following components in percentage by mass: an alkaline earth metal carbonate CO2 hydrogenation catalyst accounts for 43%, an auxiliary agent accounts for 9%, and a stabilizer accounts for 49%.

[0147] The alkaline earth metal carbonate CO2 hydrogenation catalyst is calcium carbonate, which is prepared according to the following steps:

[0148] 50g of calcium hydroxide was dissolved in 1L of pure water to obtain a suspension, and then CO2 gas was introduced into the suspension at a flow rate of 150mL / min at 30°C to cause a carbonization reaction to generate calcium carbonate. The carbonization time was controlled at 1.5h, followed by aging for 40h. Finally, it was filtered and washed, and then dried by a spray dryer to remove moisture to obtain solid calcium carbonate.

[0149] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0150] The tandem catalyst was prepared according to the following steps:

[0151] According to the above mass percentages, 15 g of alkaline earth metal carbonate CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 hours using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0152] Comparative Example 5

[0153] This embodiment provides a tandem catalyst, which is made of the following components in percentage by mass: 30% of a Pt-based propane dehydrogenation catalyst, 30% of a CO2 hydrogenation catalyst, 6% of an auxiliary agent, and 34% of a stabilizer.

[0154] The Pt-based propane dehydrogenation catalyst is prepared according to the following steps:

[0155] 1.3 g of chloroplatinic acid and 2.4 g of tin tetrachloride pentahydrate were dissolved in 100 mL of pure water, concentrated hydrochloric acid was added dropwise to adjust the pH of the solution to 6, and a clear light yellow mixed solution was obtained after stirring for 8 h. During the stirring process, the mixed solution was slowly added dropwise to 50 g of fumed silica and aged for 40 h. The gel-like solid was then transferred to a vacuum drying oven and dried at 80 ° C for 12 h. The obtained light yellow powder was calcined at 700 ° C for 8 h in a calcination furnace with a calcination atmosphere of 10% hydrogen-argon mixed gas, the gas flow rate was 50 mL / min, and the heating rate was 10 ° C / min to obtain a Pt-based propane dehydrogenation catalyst.

[0156] The CO2 hydrogenation catalyst is the commonly used Cu / ZnO / Al2O3. The specific synthesis method is: 30g of copper nitrate trihydrate and 15g of zinc nitrate hexahydrate are dissolved in 200mL of deionized water, and then 3.2g of aluminum oxide is added. The mixture is aged at room temperature for 12h, dried at 80°C, and calcined at 400°C for 4h to obtain Cu / ZnO / Al2O3.

[0157] The auxiliary agent is potassium carbonate, and the stabilizer is a mixture of aluminum oxide and silicon dioxide in a mass ratio of 2:1.

[0158] The tandem catalyst was prepared according to the following steps:

[0159] According to the above mass percentages, 15 g of Pt-based propane dehydrogenation catalyst, 15 g of CO2 hydrogenation catalyst, 3 g of auxiliary potassium carbonate and 17 g of stabilizer were weighed, mixed and placed in a ball mill jar and mechanically ball milled for 3 h using a ball mill. After the ball milling was completed, a tandem catalyst was obtained.

[0160] Figure 1 This is the XRD spectrum of the tandem catalyst of Example 1. The precious metals Pt and Sn are evenly dispersed on the carrier, and no relevant diffraction peaks are observed. The most obvious is the diffraction peak of calcium carbonate. Since the content of the auxiliary agent in the tandem catalyst is relatively small and the stabilizer used is amorphous silicon dioxide, no relevant signals are observed either.

[0161] Figure 2 It can be seen from the high-resolution electron transmission microscopy spectrum of the tandem catalyst of Example 1 that the Pt and Sn elements in the Pt-based propane dehydrogenation catalyst are evenly dispersed on the amorphous silica, and are adjacent to the CO2 hydrogenation catalyst calcium carbonate (white block) at the nanoscale. This structure of the catalyst is conducive to the rapid transfer of hydrogen from the propane dehydrogenation catalyst to the CO2 dehydrogenation catalyst during the reaction, thereby pulling the thermodynamic equilibrium of the dehydrogenation reaction and improving the single-pass conversion rate of propane and the single-pass yield of propylene. It should be noted that HAADF refers to high-angle annular dark field, which is a technology used in transmission electron microscopy.

[0162] The CO2-assisted propane dehydrogenation test was carried out on Examples 1 to 4 and Comparative Examples 1 to 5, respectively. Specifically, 2 g of the ball-milled tandem catalyst was pressed into tablets by a tablet press, and the particles were sieved with a standard sample sieve to form particles of 20 to 40 mesh for CO2-loaded propane dehydrogenation performance evaluation test.

[0163] The catalysts were loaded into a fixed bed reactor in series. The reactor was heated by a reactor equipped with a K-type temperature detection probe. The temperature was raised from room temperature to 550°C at a rate of 10°C / min under a nitrogen atmosphere. 50ml / min of propane, 50ml / min of CO2 and 100ml / min of N2 were introduced for catalytic testing. Possible products such as methane, ethane, ethylene, propane, propylene, hydrogen, carbon dioxide and carbon monoxide were detected by online gas chromatography. The catalytic evaluation results are shown in Figure 2. Figure 3 As shown in Table 1, one of the gas phase test results is as follows Figure 4 shown.

[0164] The specific evaluation results are shown in Table 1. Figure 3 , Figure 4 Table 1 provides the propane dehydrogenation performance data of each catalyst after different reaction times.

[0165] Table 1 Test results of Examples 1 to 4 and Comparative Examples 1 to 4

[0166]

[0167]

[0168] Note: \ indicates that the data is not available.

[0169] It can be seen from Table 1 that the Pt-based propane dehydrogenation catalyst has the best propane dehydrogenation performance when Pt and Sn are added and the CO2 hydrogenation catalyst is calcium carbonate, with an initial propane conversion rate of 58.2%, a propylene yield of 56.1%, and a propylene selectivity of 96.4%; compared with Example 1, Example 1 with the addition of CO2 hydrogenation catalyst and Example 4 without the addition of Pt-based propane dehydrogenation catalyst, the propane conversion rate of Example 1 decreased by 10.7%, further illustrating that the CO2 hydrogenation catalyst can improve the conversion rate of propane, and Example 4 has almost no propane dehydrogenation catalytic activity, further illustrating the importance of Pt-based propane dehydrogenation catalyst for the adsorption activation of propane. Compared with Example 1, Example 2 has a significant decrease in propane conversion rate, propylene yield, and propylene selectivity when no auxiliary metal Sn is added to Example 2, because the auxiliary metal Sn helps to activate propane by regulating the electronic structure of Pt. After omitting the auxiliary agent, the stability of Example 3 decreases significantly, because the stabilizer can ensure that the components are in contact with each other without falling off, and avoid agglomeration of the active components at high temperatures. In Comparative Example 5, the alkaline earth metal salt CO2 hydrogenation catalyst is replaced with the common Cu / ZnO / Al2O3, but its propylene selectivity decreases significantly because Cu / ZnO / Al2O3 promotes the reaction of side reactions.

[0170] from Figure 3 and Figure 4 It can be seen that at 550°C, the propane conversion rate is 50% to 58%, the propylene selectivity is not less than 96%, the continuous operation time is greater than 50 hours, and the catalyst performance is fully restored after removing carbon deposits through oxygen, with excellent high-temperature stability and cyclic regeneration capability.

[0171] It should be noted that the flame ionization detector (FID) is used for trace organic analysis. FID1 and FID2 refer to the two spectra obtained by separating different substances through two different chromatographic columns and then detecting them based on FID. The thermal conductivity detector (TCD) is used for macro and semi-micro analysis, and both organic and inorganic substances respond. Figure 4 As can be seen from a and b, the products detected by FID contain methane, ethane, propylene, propane, carbon monoxide, and carbon dioxide. Figure 4 It can be seen from c that the products to be tested, hydrogen, nitrogen and carbon dioxide, were detected by TCD.

[0172] like Figure 1 As shown in b, XRD detection shows that no sintering of the precious metal Pt was observed in the catalyst after the reaction, and the structure of the tandem catalyst did not change significantly.

[0173] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0174] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A tandem catalyst, characterized in that: The invention is prepared from the following components in percentage by mass: 20% to 40% of a Pt-based propane dehydrogenation catalyst, 20% to 40% of an alkaline earth metal carbonate CO2 hydrogenation catalyst, 2% to 10% of an auxiliary agent, and the rest of the components being a stabilizer, which together account for 100% of the total.

2. A tandem catalyst according to claim 1, characterized in that: The preparation method of the Pt-based propane dehydrogenation catalyst is: The platinum salt and the auxiliary metal precursor are dissolved in water, the pH is adjusted to 1-6, gas phase silica is added, the mixture is stirred for aging, and the mixture is dried and then calcined to obtain a Pt-based propane dehydrogenation catalyst.

3. A tandem catalyst according to claim 2, characterized in that: The auxiliary metal is Sn, Zn, Ga, Cu or In.

4. A tandem catalyst according to claim 2, characterized in that: The stirring time is 12h~48h; the calcination time is 2~16h.

5. A tandem catalyst according to claim 1, characterized in that: The preparation method of the alkaline earth metal carbonate CO2 hydrogenation catalyst is as follows: The hydroxide of the alkaline earth metal is dissolved in water, CO2 is introduced to cause a carbonization reaction to generate carbonate, and after aging, an alkaline earth metal carbonate CO2 hydrogenation catalyst is obtained.

6. A tandem catalyst according to claim 1, characterized in that: The auxiliary agent is potassium carbonate and / or sodium carbonate.

7. A tandem catalyst according to claim 1, characterized in that: The stabilizer is Al oxide and / or Si oxide.

8. A method for preparing a tandem catalyst according to any one of claims 1 to 7, characterized in that: The following steps are involved: A Pt-based propane dehydrogenation catalyst, an alkaline earth metal carbonate CO2 hydrogenation catalyst, an auxiliary agent and a stabilizer are mixed and ball milled to obtain a tandem catalyst.

9. A method for preparing a tandem catalyst according to claim 8, characterized in that: The ball milling time is 2h to 4h.

10. Use of the tandem catalyst according to any one of claims 1 to 7 in CO2-assisted propane dehydrogenation to propylene.

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