A platinum-chromium based supported catalyst, its preparation method and application

Abstract

This invention relates to the field of catalyst technology, providing a platinum-chromium-based supported catalyst, its preparation method, and its application. The platinum-chromium-based supported catalyst comprises the following components in parts by weight: a) 0.01–0.3 parts Pt or its oxide; b) 0.01–3 parts Cr or its oxide; c) 0.01–1 part Ge or its oxide; d) 0.01–3 parts iron-based elements or their oxides; e) 95–99 parts support. The catalyst provided by this invention uses Pt and Cr as dual dehydrogenation centers, while simultaneously enhancing the role of Pt with Ge and iron-based elements. Furthermore, by optimizing the catalyst preparation process and strengthening the interactions between the components, the catalyst performance is effectively improved. The catalyst provided by this invention exhibits excellent alkane dehydrogenation reaction performance and reduces the loading of precious metals Pt and Cr, thereby lowering catalyst and environmental costs, and showing promising industrial application prospects.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more specifically, to a platinum-chromium based supported catalyst, its preparation method, and its application. Background Technology

[0002] Low-carbon olefins are very important organic chemical raw materials, among which propylene, ethylene, and isobutylene are considered the foundation of modern petrochemicals. Propylene, in particular, has a wide range of applications, primarily in the production of polypropylene, which is used in woven products, injection-molded products, and film products. Furthermore, due to the many excellent properties of polypropylene fibers, their application in the three major fields of decoration, industry, and clothing is increasingly widespread, making it the second largest variety of synthetic fibers.

[0003] Traditional methods for producing propylene involve co-producing ethylene and cracking naphtha and light diesel oil. However, with the continuous growth in propylene demand in recent years, conventional methods can no longer meet this growing demand. Therefore, researchers have been dedicated to developing new routes for propylene production. Among these methods, the direct dehydrogenation process using propane from petrochemical byproducts or natural gas as feedstock has gained significant attention in recent years. Propane dehydrogenation technologies for propylene that have been successfully developed or industrialized include UOP's Oleflex process, CB&I Lummus's Catofin process, Snamprogetti-Yarsintez's fluidized bed FBD process, Krupp-Uhde's steam-activated reforming STAR process, and Linde-BASF's PDH process.

[0004] Currently, the most widely used industrialized propane dehydrogenation to propylene processes are the Oleflex process from UOP (U.S.) and the Catofin process from CB&I Lummus (U.S.). The Oleflex process uses a Pt / Al₂O₃ catalyst, which has a high Pt content and is expensive. The Catofin process uses a Cr / Al₂O₃ catalyst, with a large Cr content (approximately 20% by mass), which is environmentally unfriendly. Current research mainly focuses on optimizing Pt-based catalysts; the Pt content of the active component generally needs to be higher than 0.3 wt% to achieve good catalytic performance. There are few reports on methods to maintain catalyst activity while reducing Pt content. In their paper "Effect of preparation method on the Pt-In modified Mg(Al)O catalysts over dehydrogenation of propane," published in Catalysis Today 2020, 358:100-108, Tolek et al. reported a PtIn-supported Mg(Al)O composite oxide catalyst that did not use the traditional Cr and Sn components. The Pt component was used at a concentration of 0.3 wt%. The catalyst achieved a propylene selectivity of 98.2% at a reaction temperature of 550 °C, but the conversion rate was low, only 24.2%.

[0005] Therefore, there is an urgent need to develop an alkane dehydrogenation catalyst with low Pt content but good catalytic activity. Summary of the Invention

[0006] The purpose of this invention is to provide a platinum-chromium-based supported catalyst and its preparation method, so as to solve the technical problem that alkane dehydrogenation catalysts in the prior art need to have a high Pt content to obtain high catalytic activity.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] In a first aspect, the present invention provides a platinum-chromium-based supported catalyst, comprising the following components in parts by weight:

[0009] a) 0.01–0.3 parts of Pt or its oxides;

[0010] b) 0.01 to 3 parts of Cr or its oxide;

[0011] c) 0.01 to 1 part of Ge or its oxide;

[0012] d) 0.01 to 3 parts of iron-group elements or their oxides;

[0013] e) 95 to 99 copies of the carrier.

[0014] In this invention, the mass fraction of Pt or its oxide in the catalyst is based on the mass of Pt; the mass fraction of Cr or its oxide in the catalyst is based on the mass of Cr; the mass fraction of Ge or its oxide in the catalyst is based on the mass of Ge; and the mass fraction of iron group elements or their oxides in the catalyst is based on the mass of iron group elements.

[0015] According to some embodiments of the present invention, the catalyst, after reduction, can adsorb 0.01 to 0.03 mL / g of hydrogen.

[0016] The greater the amount of hydrogen adsorbed by the catalyst after reduction, the more Pt is exposed on the catalyst, which is more favorable for the reaction.

[0017] According to some embodiments of the present invention, the support comprises a ZnAl2O4 composite oxide.

[0018] According to some embodiments of the present invention, the preparation method of the ZnAl2O4 composite oxide includes: preparing a solution containing a soluble salt of Zn and a soluble salt of Al, adding ammonia water dropwise under stirring until the pH value is 7-9, aging, filtration, drying, calcining, and obtaining the ZnAl2O4 composite oxide.

[0019] For catalysts used in the dehydrogenation of alkanes to olefins, many side reactions can occur at the acid sites on the catalyst support surface, such as alkane cracking and isomerization, and olefin cracking, isomerization, and polymerization. Compared to common single supports such as Al2O3, the catalyst provided in this invention uses the composite oxide ZnAl2O4 as the support, which is beneficial to improving the stability of the catalytic reaction.

[0020] According to some embodiments of the present invention, the weight parts of Pt or its oxides are 0.01 to 0.2 parts.

[0021] According to some embodiments of the present invention, the weight parts of Cr or its oxide are 0.1 to 3 parts.

[0022] According to some embodiments of the present invention, the weight parts of Cr or its oxide are 0.5 to 3 parts.

[0023] According to some embodiments of the present invention, the weight parts of Cr or its oxide are 1 to 3 parts.

[0024] According to some embodiments of the present invention, the weight parts of Ge or its oxide are 0.1 to 0.8 parts.

[0025] According to some embodiments of the present invention, the weight parts of Ge or its oxide are 0.3 to 0.8 parts.

[0026] According to some embodiments of the present invention, the iron group elements or their oxides are present in weight parts of 0.1 to 2 parts.

[0027] According to some embodiments of the present invention, the iron group elements or their oxides are present in weight parts of 0.5 to 2 parts.

[0028] According to some embodiments of the present invention, the iron group elements include at least one of Fe, Co, and Ni.

[0029] In a second aspect, the present invention provides a method for preparing the catalyst described in the first aspect, comprising: mixing a solution comprising a soluble salt of Pt, a soluble salt of Cr, a soluble salt of Ge and a soluble salt of an iron group element with a support, drying, and calcining to obtain the catalyst.

[0030] According to some embodiments of the present invention, the preparation method includes: firstly mixing a first solution containing a soluble salt of Cr with a support, followed by a first drying and a first calcination to obtain a catalyst precursor; then mixing a second solution containing a soluble salt of Pt, a soluble salt of Ge, and a soluble salt of iron-group elements with the catalyst precursor for a second time, followed by filtration and washing, a second drying, and a second calcination to obtain the catalyst.

[0031] According to some embodiments of the present invention, the preparation method of the second solution includes: adding soluble salts of Pt, soluble salts of Ge, and soluble salts of iron-group elements to a polyethylene glycol (PEG) solution containing sodium dodecyl sulfate (SDS), and stirring at 110-130°C; preferably, the stirring time is 3-5 h.

[0032] According to some embodiments of the present invention, the molecular weight of the polyethylene glycol is 400 to 600.

[0033] According to some embodiments of the present invention, the concentration of sodium dodecyl sulfate in a polyethylene glycol solution containing sodium dodecyl sulfate is 2.5 to 5.0 g / L.

[0034] According to some embodiments of the present invention, the temperature of the first drying is 80-150°C and the time is 6-24 hours.

[0035] According to some embodiments of the present invention, the temperature of the first roasting is 450-700°C and the time is 6-24 hours.

[0036] According to some embodiments of the present invention, the temperature of the second drying is 80-150°C, and the time is 6-24 hours.

[0037] According to some embodiments of the present invention, the temperature of the second calcination is 450–700°C, and the time is 6–24 hours.

[0038] All stirring operations in this invention can be performed under ultrasonic conditions. The ultrasonic conditions include: first ultrasonication at 10 kHz for 1 hour, and then ultrasonication at 30 kHz for 1 hour.

[0039] Thirdly, the present invention provides the application of the catalyst described in the first aspect in the dehydrogenation of alkanes to olefins.

[0040] According to some embodiments of the present invention, the alkane is propane.

[0041] According to some embodiments of the present invention, the reaction conditions for the dehydrogenation of alkane to olefins are as follows: a steam to propane volume ratio of (10–1):1, a reaction temperature of 400–600°C, a reaction pressure of 0–1 MPa, and an alkane mass hourly space velocity of 3.0–8.0 h⁻¹. -1 .

[0042] The beneficial effects of this invention are at least as follows:

[0043] (1) The catalyst provided by the present invention uses Pt and Cr as dual dehydrogenation centers, and at the same time uses Ge and iron-based elements to enhance the role of Pt, thereby improving the catalyst performance.

[0044] (2) The catalyst provided by the present invention improves the performance of the catalyst by optimizing the catalyst preparation process and strengthening the interaction between the components.

[0045] (3) The catalyst provided by the present invention has good performance in alkane dehydrogenation reaction and reduces the loading of precious metals Pt and Cr, thereby reducing catalyst cost and environmental protection cost, and has industrial application prospects. Detailed Implementation

[0046] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0047] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0048] Preparation Example 1

[0049] Weigh 297.49g of zinc nitrate hexahydrate and 750.26g of aluminum nitrate nonahydrate and dissolve them in 1L of deionized water. Mix well and slowly add ammonia water dropwise while stirring continuously to adjust the pH to 8.0. Age the product for 2 hours, wash the filter cake with 4L of water, dry the filter cake at 120℃ for 18 hours, and then calcine it in a muffle furnace at 660℃ for 20 hours to obtain the ZnAl2O4 support.

[0050] Example 1

[0051] (1) Weigh 1.539g of chromium nitrate nonahydrate and dissolve it in 10mL of water. Add it to 9.635g of the ZnAl2O4 support of Preparation Example 1 while stirring. Mix it evenly by sonication at 10 kHz for 1h and 30 kHz for 1h. Dry it at 120℃ for 18h and calcine it in a muffle furnace at 660℃ for 20h to obtain catalyst precursor I.

[0052] (2) Weigh 0.040 g of chloroplatinic acid hexahydrate, 0.723 g of ferric nitrate nonahydrate and 0.148 g of germanium chloride and dissolve them in 10 mL of polyethylene glycol (molecular weight 500) solution with SBS concentration of 4.0 g / L. After stirring at 120 °C for 4 h, add catalyst precursor I, sonicate at 10 kHz for 1 h at 120 °C and sonicate at 30 kHz for 1 h to mix evenly, filter and wash with 100 mL of water, dry at 120 °C for 18 h, and calcine in a muffle furnace at 660 °C for 20 h to obtain the catalyst.

[0053] Example 2

[0054] (1) Weigh 2.309g of chromium nitrate nonahydrate and dissolve it in 10mL of water. Add it to 9.475g of ZnAl2O4 support of Preparation Example 1 while stirring. Mix it evenly by sonication at 10 kHz for 1h and 30 kHz for 1h. Dry it at 120℃ for 18h and calcine it in a muffle furnace at 660℃ for 20h to obtain catalyst precursor I.

[0055] (2) Weigh 0.013 g of chloroplatinic acid hexahydrate, 1.085 g of ferric nitrate nonahydrate and 0.207 g of germanium chloride and dissolve them in 10 mL of polyethylene glycol (molecular weight 400) solution with SBS concentration of 2.5 g / L. After stirring at 120 °C for 4 h, add catalyst precursor I, sonicate at 10 kHz for 1 h at 120 °C and sonicate at 30 kHz for 1 h to mix evenly, filter and wash with 100 mL of water, dry at 120 °C for 10 h, and calcine in a muffle furnace at 660 °C for 20 h to obtain the catalyst.

[0056] Example 3

[0057] The catalyst was prepared in accordance with Example 1, except that 0.723g of ferric nitrate nonahydrate was replaced with 0.494g of cobalt nitrate hexahydrate.

[0058] Example 4

[0059] The catalyst was prepared in accordance with Example 1, except that 0.723g of ferric nitrate nonahydrate was replaced with 0.496g of nickel nitrate hexahydrate.

[0060] Example 5

[0061] 1.539 g of chromium nitrate nonahydrate, 0.040 g of chloroplatinic acid hexahydrate, 0.723 g of ferric nitrate nonahydrate, and 0.148 g of germanium chloride were weighed and dissolved in 10 mL of polyethylene glycol (molecular weight 500) solution with an SBS concentration of 4.0 g / L. After stirring at 120 °C for 4 h, 9.635 g of ZnAl2O4 support from Preparation Example 1 was added. The mixture was then sonicated at 10 kHz for 1 h and then at 30 kHz for 1 h to mix thoroughly. The mixture was filtered and washed with 100 mL of water, dried at 120 °C for 18 h, and calcined in a muffle furnace at 660 °C for 20 h to obtain the catalyst.

[0062] Example 6

[0063] The catalyst was prepared according to Example 1, except that the 10 mL of SBS solution with a concentration of 4.0 g / L in step (2) was replaced with 10 mL of water.

[0064] Example 7

[0065] The catalyst was prepared according to Example 1, except that the stirring at 120°C for 4 hours in step (2) was changed to stirring at room temperature for 4 hours.

[0066] Example 8

[0067] The catalyst was prepared in accordance with Example 1, except that polyethylene glycol with a molecular weight of 500 was replaced with polyethylene glycol with a molecular weight of 200.

[0068] Example 9

[0069] The catalyst was prepared in accordance with Example 1, except that polyethylene glycol with a molecular weight of 500 was replaced with polyethylene glycol with a molecular weight of 700.

[0070] Example 10

[0071] The catalyst was prepared in accordance with Example 1, except that the polyethylene glycol solution with a sodium dodecyl sulfate concentration of 4.0 g / L was replaced with a polyethylene glycol solution with a sodium dodecyl sulfate concentration of 2.0 g / L.

[0072] Example 11

[0073] The catalyst was prepared in accordance with Example 1, except that the polyethylene glycol solution with a sodium dodecyl sulfate concentration of 4.0 g / L was replaced with a polyethylene glycol solution with a sodium dodecyl sulfate concentration of 6.0 g / L.

[0074] Comparative Example 1

[0075] Weigh 0.040 g of chloroplatinic acid hexahydrate and dissolve it in 10 mL of water. Add the solution to 9.985 g of the ZnAl2O4 support from Preparation Example 1 with stirring. Mix well, sonicate at 10 kHz for 1 h, sonicate at 30 kHz for 1 h to mix well, dry at 120 °C for 18 h, and calcine in a muffle furnace at 660 °C for 20 h to obtain the catalyst.

[0076] Comparative Example 2

[0077] 0.040 g of chloroplatinic acid hexahydrate, 0.723 g of ferric nitrate nonahydrate, and 0.148 g of germanium chloride were weighed and dissolved in 10 mL of polyethylene glycol (molecular weight 500) with an SBS concentration of 4.0 g / L. After stirring at 120 °C for 4 h, 9.835 g of the ZnAl2O4 support from Preparation Example 1 was added. The mixture was sonicated at 10 kHz at 120 °C for 1 h and then sonicated at 30 kHz for 1 h to mix thoroughly. The mixture was then filtered and washed with 100 mL of water, dried at 120 °C for 18 h, and calcined in a muffle furnace at 660 °C for 20 h to obtain the catalyst.

[0078] Comparative Example 3

[0079] The catalyst was prepared in accordance with Example 1, except that 0.148g of germanium chloride was not added and the amount of ZnAl2O4 support added was 9.685g.

[0080] Comparative Example 4

[0081] The catalyst was prepared in accordance with Example 1, except that 0.723g of ferric nitrate nonahydrate was not added, and the amount of ZnAl2O4 support added was 9.735g.

[0082] Catalyst performance evaluation

[0083] (1) Catalyst activity evaluation

[0084] The catalysts prepared in each embodiment and comparative example were evaluated for their activity in an isothermal fixed-bed reactor. The evaluation methods are as follows:

[0085] Propane gas is fed into a preheating zone for mixing by adjusting the flow rate using a mass flow meter, and then enters the reaction zone. Both the preheating and reaction zones of the reactor are heated by heating wires to reach a predetermined temperature. The reactor is constructed with a stainless steel sleeve with an inner diameter of Ф9mm-Ф6mm and a length of approximately 400mm. After the reaction, the gas passes through a condenser and is then analyzed by gas chromatography to determine its composition.

[0086] Evaluation criteria include:

[0087] 0.5 g of catalyst was loaded into the above-mentioned isothermal fixed-bed reactor (catalyst bed height 17 mm), and the reaction was carried out at atmospheric pressure and 550 °C; the volume ratio of water vapor to propane was 4:1; and the propane mass hourly space velocity was 3.0 h⁻¹. -1 .

[0088] The calculation methods for propane conversion and propylene selectivity are as follows:

[0089]

[0090]

[0091] The content of substances in the above calculation formulas are all molar amounts.

[0092] The evaluation results are shown in Table 1.

[0093] (2) Hydrogen adsorption capacity

[0094] The hydrogen adsorption capacity was obtained using an AutoChem II 2920 instrument from Micromeritics Inc., USA. The specific method included: heating to 550℃ at a rate of 10℃ / min, reducing with H₂ / Ar for 2 hours; switching to an Ar atmosphere, heating to 580℃, purging for 1 hour, cooling to 45℃, and titrating to saturation with pulsed hydrogen gas to obtain the hydrogen adsorption capacity. The test results are shown in Table 1.

[0095] Table 1

[0096]

[0097]

[0098] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on 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 terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A platinum-chromium based supported catalyst, characterized in that, The components include the following parts by weight: a) 0.01–0.3 parts of Pt or its oxides; b) 1 to 3 parts of Cr or its oxide; c) 0.01 to 1 part of Ge or its oxide; d) 0.5 to 3 parts of iron-group elements or their oxides; e) 95–99 copies of the carrier; After reduction, the catalyst can adsorb 0.01~0.03 mL / g of hydrogen. The carrier comprises ZnAl2O4 composite oxide.

2. The catalyst according to claim 1, characterized in that, The weight parts of Pt or its oxides are 0.01 to 0.2 parts; And / or, the weight parts of Ge or its oxides are 0.1 to 0.8 parts; And / or, the iron group elements or their oxides are in the amount of 0.5 to 2 parts by weight.

3. The method for preparing the catalyst according to claim 1 or 2, characterized in that, include: The catalyst is prepared by mixing a solution containing soluble salts of Pt, Cr, Ge, and iron group elements with a support, drying, and calcining.

4. The preparation method according to claim 3, characterized in that, The preparation method includes: firstly, mixing a first solution containing a soluble salt of Cr with a support for the first time, followed by a first drying and a first calcination to obtain a catalyst precursor; then, mixing a second solution containing a soluble salt of Pt, a soluble salt of Ge, and a soluble salt of iron-based elements with the catalyst precursor for the second time, followed by filtration and washing, a second drying, and a second calcination to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that, The preparation method of the second solution includes: adding soluble salts of Pt, soluble salts of Ge, and soluble salts of iron-group elements to a polyethylene glycol solution containing sodium dodecyl sulfate, and stirring at 110~130°C.

6. The preparation method according to claim 5, characterized in that, The stirring time is 3 to 5 hours.

7. The preparation method according to claim 5, characterized in that, The molecular weight of the polyethylene glycol is 400-600; And / or, the concentration of sodium dodecyl sulfate in the polyethylene glycol solution containing sodium dodecyl sulfate is 2.5~5.0 g / L.

8. The preparation method according to any one of claims 4-7, characterized in that, The temperature for the first drying step is 80–150°C; And / or, the temperature of the first calcination is 450–700°C, and the time is 6–24 hours; And / or, the temperature of the second drying is 80–150°C; And / or, the second calcination temperature is 450–700°C, and the time is 6–24 hours.

9. The application of the catalyst according to claim 1 or 2 in the dehydrogenation of alkane to olefins.

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