Platinum-based binary intermetallic compound catalyst for preparing propylene through propane dehydrogenation

Abstract

The invention relates to a platinum-based binary intermetallic compound catalyst for preparing propylene through propane dehydrogenation. The platinum-based binary intermetallic compound catalyst comprises a molecular sieve carrier, metal platinum and second metal, wherein the metal platinum and the second metal are loaded on the molecular sieve carrier; wherein the second metal is selected from zinc, indium, tin, copper, gallium, cobalt, germanium, nickel and iron. The invention also relates to a preparation method of the catalyst. According to the method, controllable preparation of the bimetallic intermetallic compound is successfully realized through a high-temperature thermal shock method. The method specifically comprises regulation and control of a catalytic carrier and controllable regulation of an active center of the catalyst under a high-temperature thermal shock condition. According to the invention, a high-temperature thermal shock technology is applied to preparation of the propane dehydrogenation catalyst for the first time, and stable existence of a noble metal active center in a reaction process is realized by forming an intermetallic compound. Compared with the prior art, the catalyst provided by the invention has the advantages that the propylene selectivity is improved to 99%, and meanwhile, the propane conversion rate of 32% is kept.

Description

Technical Field

[0001] The present invention belongs to catalyst preparation technology and relates to a platinum-based binary intermetallic compound catalyst for producing propylene by dehydrogenating propane, and a preparation method and application thereof. Background Art

[0002] Propane, an important basic chemical product, is primarily found in natural gas and light hydrocarbons from oilfields. For a long time, propane has been used as a fuel for engines and as an energy source for home heating systems, but this low-value utilization has resulted in a wasteful use of resources. In recent years, the growing demand for propylene has led to a widening price gap between propane and propylene. Simultaneously, the downstream products of propylene, including polypropylene, acrylonitrile, propylene oxide, and ethylene propylene rubber, have become increasingly abundant. The increasing demand for these products has further fueled the demand for higher-value propane utilization. Against the backdrop of the surge in propane production driven by the shale gas revolution, propane dehydrogenation to propylene processes with high propylene selectivity have attracted significant attention.

[0003] However, the inherently endothermic nature and thermodynamic equilibrium limitations of propane dehydrogenation, as well as the catalyst's susceptibility to carbon deposition, sintering, and metal loss at high temperatures, severely restrict the economic benefits of industrial production. Therefore, developing highly active, selective, and stable dehydrogenation catalyst systems has become a key research focus. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a platinum-based binary intermetallic compound catalyst for propane dehydrogenation to propylene in response to the problems existing in the prior art. The catalyst has high activity and high selectivity and is not prone to problems such as carbon deposition, sintering and metal loss at high temperatures, and has excellent stability. The present invention also provides a method for preparing the above-mentioned catalyst. The preparation method has low raw material prices, a simple preparation process, and can overcome the problem of active center structural stability during the reaction process of existing propane dehydrogenation catalysts, effectively preparing a catalyst with high activity, high selectivity and excellent stability.

[0005] To this end, the first aspect of the present invention provides a platinum-based binary intermetallic compound catalyst for propane dehydrogenation to propylene, which comprises a molecular sieve support, and metallic platinum and a second metal supported on the molecular sieve support; wherein the second metal is selected from zinc, indium, tin, copper, gallium, cobalt, germanium, nickel and iron.

[0006] According to the present invention, the mass fraction of platinum in the platinum-based binary intermetallic compound catalyst is 0.1% to 1%; preferably, the molar ratio of metal platinum to the second metal in the platinum-based binary intermetallic compound catalyst is 0.1 to 5.

[0007] In the present invention, the bimetallic compound includes one or more of platinum zinc, platinum indium, platinum tin, platinum copper, platinum gallium, platinum cobalt, platinum germanium, platinum nickel and platinum iron.

[0008] A second aspect of the present invention provides a method for preparing a platinum-based binary intermetallic compound catalyst for dehydrogenating propane to propylene, comprising:

[0009] Step A, synthesizing a molecular sieve support using a hydrothermal method;

[0010] Step B, treating the molecular sieve support with an aqueous acid solution to obtain an acid-treated molecular sieve support;

[0011] Step C, respectively mixing the platinum metal precursor solution and the second metal precursor solution with the acid-treated molecular sieve support and volatilizing the solvent to obtain a platinum-based binary intermetallic compound catalyst precursor;

[0012] Step D: subjecting the platinum-based binary intermetallic compound catalyst precursor to a high-temperature thermal shock treatment, and then fully grinding it to obtain the platinum-based binary intermetallic compound catalyst.

[0013] According to the present invention, in step A, the temperature for synthesizing the molecular sieve carrier by hydrothermal method is 80-200°C.

[0014] In some embodiments of the present invention, the pH of the aqueous solution of the acid is 1-6.

[0015] Preferably, the acid comprises one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

[0016] According to the present invention, in step C, the platinum metal precursor solution and the second metal precursor solution are sequentially mixed with the acid-treated molecular sieve support, or the second metal precursor solution and the platinum metal precursor solution are sequentially mixed with the acid-treated molecular sieve support.

[0017] In some embodiments of the present invention, the platinum metal precursor solution is obtained by dissolving a platinum metal precursor in water. Preferably, the concentration of the platinum metal precursor solution is 0.1 mol / L; further preferably, the platinum metal precursor includes tetraammineplatinum nitrate.

[0018] In some embodiments of the present invention, the second metal precursor solution is obtained by dissolving the second metal precursor in water. Preferably, the concentration of the second metal precursor is 0.1 mol / L; further preferably, the second metal precursor includes one or more of zinc nitrate, indium nitrate, stannous chloride, copper nitrate, gallium nitrate, ammonium hexafluorogermanate, cobalt nitrate, nickel nitrate and iron nitrate.

[0019] According to the present invention, the temperature of the high-temperature thermal shock treatment is 800-1800°C.

[0020] Preferably, the high-temperature thermal shock treatment is performed 1 to 20 times.

[0021] The third aspect of the present invention provides the use of the platinum-based binary intermetallic compound catalyst as described in the first aspect of the present invention or the platinum-based binary intermetallic compound catalyst prepared by the preparation method as described in the second aspect of the present invention in the dehydrogenation of propane to propylene.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention adopts a special synthesis method to form an intermetallic compound structure in the catalyst. At the same time, the addition of the second component metal additive regulates the electronic state of the active center platinum, further improving the reaction activity.

[0024] (2) The special structure of the catalyst synthesized in the present invention imparts high stability, so that it will not be sintered and deactivated due to metal agglomeration under high temperature conditions.

[0025] (3) The raw materials used in the preparation process of the present invention are relatively low in price and the preparation process is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be further described in detail below with reference to the accompanying drawings:

[0027] Figure 1 Schematic diagram of the microreactor in the present invention. DETAILED DESCRIPTION

[0028] To facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and examples. However, before describing the present invention in detail, it should be understood that the present invention is not limited to the specific embodiments described. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0029] Where a range of values is provided, it is understood that each intervening value between the upper and lower limits of the range and any other specified or intervening values in the specified range is encompassed within the present invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the present invention, subject to any express exclusions in the specified range. Where a specified range includes one or both limits, ranges excluding either or both of those included limits are also encompassed within the present invention.

[0030] Unless otherwise defined, all terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, preferred methods and materials are now described.

[0031] I. Terminology

[0032] The term "water" in the present invention, unless otherwise specified or limited, refers to deionized water, distilled water or ultrapure water.

[0033] II. Implementation Plan

[0034] As previously mentioned, the inherently strong endothermic nature and thermodynamic equilibrium constraints of the propane dehydrogenation reaction, as well as the catalyst's susceptibility to carbon deposition, sintering, and metal loss at high temperatures, severely restrict the economic benefits of industrial production. To this end, the present inventors have conducted extensive research on propane dehydrogenation catalysts, aiming to develop a highly active, highly selective, and stable dehydrogenation catalyst.

[0035] The inventors have discovered that direct dehydrogenation of propane to propylene is an inherently endothermic process, with its chemical equilibrium primarily governed by thermodynamics. Theoretically, the optimal reaction temperature is 550°C or above. At these high temperatures, the metal active sites in the catalyst are prone to agglomeration and sintering due to the increased surface energy. To address this issue, the present invention proposes a stable method for synthesizing intermetallic compounds that maintains the stability of the catalyst's active sites at elevated reaction temperatures. This intermetallic compound is constructed using a high-temperature thermal shock method for use in propane dehydrogenation reactions.

[0036] The inventors further discovered that the dispersion of the metal active centers in the catalyst is positively correlated with the catalytic performance, especially when the active centers are uniformly dispersed on the support in the form of single atoms, the catalyst usually exhibits excellent activity and selectivity. However, the propane dehydrogenation reaction is essentially an endothermic process, and its chemical equilibrium is mainly controlled by thermodynamics. The theoretical optimal reaction temperature should be 550°C and above. Under such high temperature conditions, the single-atom active centers are prone to agglomeration and sintering due to the increase in surface energy. The intermetallic compound synthesized by the high-temperature thermal shock method quickly decomposes the metal precursor, thereby forming an interaction with the support, so that the active center platinum can be stably present on the catalyst surface under high temperature conditions, and a better activity ensemble is formed through the ordered intermetallic compound structure, further improving the activity and selectivity of the catalyst. Thus, the present invention is obtained.

[0037] To solve the above problems, the present invention provides a method for preparing a platinum-based binary intermetallic compound catalyst for propane dehydrogenation to propylene, comprising the following steps:

[0038] (1) Synthesizing a ZSM-5 molecular sieve support using a hydrothermal method at 80-200°C;

[0039] (2) treating the molecular sieve support with an acid aqueous solution under acidic conditions with a pH of 1 to 6 to obtain an acid-treated molecular sieve support;

[0040] (3) sequentially mixing a platinum metal precursor solution and a second metal (metal additive) precursor solution with the acid-treated molecular sieve support, or sequentially mixing the second metal precursor solution and the platinum metal precursor solution with the acid-treated molecular sieve support, mixing them uniformly and volatilizing the solvent to obtain a platinum-based binary metal intermetallic compound catalyst precursor with a metal molar ratio of 0.1 to 5;

[0041] (4) subjecting the platinum-based binary intermetallic compound catalyst precursor to a high-temperature thermal shock treatment at a shock temperature of 800 to 1800° C. and a number of shocks of 1 to 20, and then fully grinding the precursor to obtain the platinum-based binary intermetallic compound catalyst.

[0042] Preferably, the acid comprises one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

[0043] In some embodiments of the present invention, the platinum metal precursor solution is obtained by dissolving a platinum metal precursor in water. Preferably, the concentration of the platinum metal precursor solution is 0.1 mol / L; further preferably, the platinum metal precursor includes but is not limited to tetraammineplatinum nitrate.

[0044] In some embodiments of the present invention, the second metal precursor solution is obtained by dissolving the second metal precursor in water. Preferably, the concentration of the second metal precursor is 0.1 mol / L; further preferably, the second metal precursor includes one or more of zinc nitrate, indium nitrate, stannous chloride, copper nitrate, gallium nitrate, ammonium hexafluorogermanate, cobalt nitrate, nickel nitrate and iron nitrate.

[0045] In the present invention, there is no particular limitation on the method for synthesizing the ZSM-5 molecular sieve carrier by the hydrothermal method, and it can be prepared by conventional methods in the art. For example, it can be prepared by referring to the preparation method in the literature Industrial Engineering Chemistry Research. 2019, 58, 15453-15458.

[0046] Based on the above method, the present invention prepares a platinum-based binary intermetallic compound catalyst for propane dehydrogenation to propylene, which comprises a molecular sieve support, and metal platinum and a second metal supported on the molecular sieve support; wherein the second metal is selected from zinc, indium, tin, copper, gallium, cobalt, germanium, nickel and iron.

[0047] In the present invention, the bimetallic compound includes one or more of platinum zinc, platinum indium, platinum tin, platinum copper, platinum gallium, platinum cobalt, platinum germanium, platinum nickel and platinum iron.

[0048] According to the present invention, the mass fraction of platinum in the platinum-based binary intermetallic compound catalyst is 0.1% to 1%; preferably, the molar ratio of metal platinum to the second metal in the platinum-based binary intermetallic compound catalyst is 0.1 to 5.

[0049] The present invention also relates to the use of the above-mentioned platinum-based binary intermetallic compound catalyst in the dehydrogenation of propane to propylene, which can be understood as a method for dehydrogenating propane to propylene using the above-mentioned platinum-based binary intermetallic compound catalyst. The method specifically comprises placing the platinum-based binary intermetallic compound catalyst into a fixed bed reactor (such as Figure 1 As shown), both ends are sealed with quartz sand, nitrogen is introduced, the reaction temperature is raised under a nitrogen atmosphere for pretreatment, and then propane raw gas is introduced to carry out propane dehydrogenation reaction to obtain propylene.

[0050] In some embodiments of the present invention, the propane feed gas contains 25% propane and 75% nitrogen.

[0051] Preferably, the heating rate is 5°C / min.

[0052] Preferably, the reaction temperature is 550°C.

[0053] Preferably, the pretreatment time is 1 hour.

[0054] Preferably, the space velocity of the reaction is 40 ml propane / g catalyst / hour.

[0055] The present invention addresses the existing problems of carbon deposition, sintering, and metal loss in catalysts under high-temperature conditions. By successfully achieving the controlled preparation of bimetallic compounds through a high-temperature thermal shock method, this method specifically involves regulating the catalytic carrier and the controllable adjustment of the catalyst's active centers under high-temperature thermal shock conditions. This present invention is the first to apply high-temperature thermal shock technology to the preparation of propane dehydrogenation catalysts, achieving the stable presence of noble metal active centers during the reaction by forming intermetallic compounds. Compared to the existing technology, the catalyst of the present invention increases propylene selectivity to 99% while maintaining a propane conversion rate of up to 32%.

[0056] Example

[0057] The present invention is described in detail below through specific examples. The experimental methods described below, unless otherwise specified, are all routine laboratory methods. The experimental materials described below, unless otherwise specified, can all be obtained from commercial channels.

[0058] The effects of reaction conditions on the prepared catalysts and their catalytic performance are investigated below through Examples 1-30.

[0059] 1. The catalyst is prepared by high temperature thermal shock method. The specific preparation method is as follows:

[0060] (1) Synthesizing the molecular sieve support using a hydrothermal method at 80-200°C;

[0061] (2) treating the molecular sieve support with an aqueous solution of an acid under different acid conditions with a pH of 1 to 6 to obtain an acid-treated molecular sieve support;

[0062] (3) sequentially mixing the platinum metal precursor solution and the second metal precursor solution with the acid-treated molecular sieve support, or sequentially mixing the second metal precursor solution and the platinum metal precursor solution with the acid-treated molecular sieve support, mixing them uniformly and volatilizing the solvent to obtain a platinum-based binary intermetallic compound catalyst precursor;

[0063] (4) subjecting the platinum-based binary intermetallic compound catalyst precursor to a high-temperature thermal shock treatment at a shock temperature of 800 to 1800° C. and a number of shocks of 1 to 20, and then fully grinding the precursor to obtain the platinum-based binary intermetallic compound catalyst.

[0064] The acid includes one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

[0065] The platinum metal precursor solution is obtained by dissolving a platinum metal precursor in water. Preferably, the concentration of the platinum metal precursor solution is 0.1 mol / L. Further preferably, the platinum metal precursor includes but is not limited to tetraammineplatinum nitrate.

[0066] The second metal precursor solution is obtained by dissolving the second metal precursor in water. Preferably, the concentration of the second metal precursor is 0.1 mol / L; further preferably, the second metal precursor includes one or more of zinc nitrate, indium nitrate, stannous chloride, copper nitrate, gallium nitrate, ammonium hexafluorogermanate, cobalt nitrate, nickel nitrate and iron nitrate.

[0067] (2) Using the catalyst prepared by the above method to catalyze the dehydrogenation of propane to propylene, the specific steps are as follows:

[0068] The performance test of the catalyst was carried out in a fixed bed reactor equipped with a temperature sensor. The experimental process is as follows: first, 30-35 grams of quartz sand were filled under the steel tube of the fixed bed reactor used, and then 0.05 grams of granulated catalyst (40 to 60 mesh) and 0.5 grams of quartz sand (40 to 60 mesh) were mixed evenly and filled into the steel tube, and finally a 5-gram quartz sand seal was filled on top. The filled reaction tube was placed in a tubular furnace, nitrogen was introduced, and the temperature was raised to 550°C at 5 degrees per minute under an inert atmosphere for pretreatment for 1 hour. Propane gas was then introduced so that the raw gas composition accounted for 25% propane and 75% nitrogen, with an air velocity of 40 ml propane / g catalyst / hour. The propane conversion rate was obtained by measuring the gas composition before and after the reaction, and the reactor outlet gas was analyzed by a gas chromatograph equipped with a flame ionization detector.

[0069] The reaction conditions for preparing the catalysts in Examples 1-30, as well as the propane conversion rate and propylene selectivity for catalytic dehydrogenation of propane to propylene using the catalysts are shown in Table 1 below.

[0070] Table 1

[0071]

[0072] Comparing platinum-based binary intermetallic compound catalysts formed with different metal promoters, the catalyst with a molecular sieve hydrothermally synthesized at 180°C and treated with nitric acid as the carrier, a platinum-zinc ratio of 0.8, a thermal shock temperature of 1500°C, and 10 shock times showed better performance in propane dehydrogenation, specifically 99% propylene selectivity and 32% propane conversion rate.

[0073] It should be noted that the embodiments described above are only preferred embodiments of the present invention and are used for illustration to facilitate understanding of the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A platinum-based binary intermetallic compound catalyst for propane dehydrogenation to propylene, comprising a molecular sieve support, and metallic platinum and a second metal supported on the molecular sieve support; wherein: The second metal is selected from the group consisting of zinc, indium, tin, copper, gallium, cobalt, germanium, nickel and iron.

2. The platinum-based binary intermetallic compound catalyst according to claim 1, characterized in that The mass fraction of platinum in the platinum-based binary intermetallic compound catalyst is 0.1% to 1%; preferably, the molar ratio of metal platinum to the second metal in the platinum-based binary intermetallic compound catalyst is 0.1 to 5.

3. The platinum-based binary intermetallic compound catalyst according to claim 1 or 2, characterized in that: The bimetallic compound includes one or more of platinum zinc, platinum indium, platinum tin, platinum copper, platinum gallium, platinum cobalt, platinum germanium, platinum nickel and platinum iron.

4. A method for preparing a platinum-based binary intermetallic compound catalyst for propane dehydrogenation to propylene, comprising: Step A, synthesizing a molecular sieve support using a hydrothermal method; Step B, treating the molecular sieve support with an aqueous acid solution to obtain an acid-treated molecular sieve support; Step C, respectively mixing the platinum metal precursor solution and the second metal precursor solution with the acid-treated molecular sieve support and volatilizing the solvent to obtain a platinum-based binary intermetallic compound catalyst precursor; Step D: subjecting the platinum-based binary intermetallic compound catalyst precursor to a high-temperature thermal shock treatment, and then fully grinding it to obtain the platinum-based binary intermetallic compound catalyst.

5. The preparation method according to claim 4 is characterized in that, In step A, the temperature for synthesizing the molecular sieve carrier by the hydrothermal method is 80-200°C.

6. The preparation method according to claim 4, characterized in that The pH of the aqueous solution of the acid is 1 to 6; preferably, the acid includes one or more of sulfuric acid, nitric acid, hydrochloric acid and phosphoric acid.

7. The preparation method according to claim 4, characterized in that In step C, the platinum metal precursor solution and the second metal precursor solution are sequentially mixed with the acid-treated molecular sieve support, or the second metal precursor solution and the platinum metal precursor solution are sequentially mixed with the acid-treated molecular sieve support; And / or, the platinum metal precursor solution is obtained by dissolving a platinum metal precursor in water, preferably, the concentration of the platinum metal precursor solution is 0.1 mol / L; further preferably, the platinum metal precursor includes tetraammine platinum nitrate; And / or, the second metal precursor solution is obtained by dissolving the second metal precursor in water, preferably, the concentration of the second metal precursor is 0.1 mol / L; further preferably, the second metal precursor includes one or more of zinc nitrate, indium nitrate, stannous chloride, copper nitrate, gallium nitrate, ammonium hexafluorogermanate, cobalt nitrate, nickel nitrate and iron nitrate.

8. The preparation method according to any one of claims 4 to 7, characterized in that The temperature of the high-temperature thermal shock treatment is 800-1800° C.; and / or the number of times of the high-temperature thermal shock treatment is 1-20.

9. Use of the platinum-based binary intermetallic compound catalyst according to any one of claims 1 to 3 or the platinum-based binary intermetallic compound catalyst prepared by the preparation method according to any one of claims 4 to 8 in the dehydrogenation of propane to propylene.

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