Rhodium-based aerogel catalyst as well as preparation method and application thereof

Abstract

The invention discloses a rhodium-based aerogel catalyst as well as a preparation method and application thereof. The rhodium-based aerogel catalyst is prepared from a rare earth element modified boron nitride aerogel carrier and an active component rhodium loaded on the rare earth element modified boron nitride aerogel carrier, in the rhodium-based aerogel catalyst, the mass fraction of the active component rhodium is 0.05-0.5 wt%, and the mass fraction of the rare earth element is 1-15 wt%; the rare earth element is selected from at least one of cerium, zirconium, lanthanum, yttrium, samarium and praseodymium. The catalyst can be used in a low-carbon alkane oxygen cracking partial oxidation hydrogen production reaction at a relatively low temperature, such as lt; at 600 DEG C, the conversion rate of alkane is more than 80%, and the activity performance of the catalyst is far superior to that of a rhodium-based catalyst taking a rare earth oxide as a carrier. The catalyst has H2 selectivity close to 100%. The catalyst is stable in structure, resistant to sintering and carbon deposition and capable of stably running for a long time.

Description

Technical Field

[0001] The present application relates to a rhodium-based aerogel catalyst and a preparation method and application thereof, belonging to the field of catalysts. Background Art

[0002] In the context of current energy transformation and carbon neutrality, the partial oxidation of low-carbon alkanes (such as methane, ethane, and propane) to produce hydrogen under oxygen conditions (POX, Partial Oxidation of Hydrocarbons) has many advantages such as efficient resource utilization, environmental protection, energy conservation, and technical feasibility. It is one of the important ways to promote the development of the hydrogen energy industry and provides technical support for the realization of a low-carbon economy. Low-carbon alkane resources are abundant. Methane is the main component of natural gas, with abundant reserves and wide distribution. It is a clean and efficient energy resource. In addition to obtaining it from natural gas, ethane and propane can be obtained through biomass pyrolysis, fermentation and other technologies, providing a potential source of renewable raw materials for partial oxidation of hydrogen under oxygen conditions. Compared with the traditional steam reforming method, the partial oxidation of low-carbon alkanes to produce hydrogen is an exothermic reaction that does not require additional energy input and has higher energy utilization efficiency. The partial oxidation reaction pathway under oxygen conditions can reduce the generation of by-products (such as CO) and improve hydrogen selectivity, thereby achieving a more economical hydrogen production process.

[0003] However, there are the following challenges for partial oxidation catalysts in the presence of oxygen: (1) It is difficult to balance selectivity and activity, as highly active catalysts tend to promote complete oxidation of alkanes; (2) Anti-sintering performance needs to be improved, as the agglomeration of metal particles or deactivation of active sites under high temperature conditions is the main problem; (3) Carbon deposition is serious, as carbon chains are easily cracked to form carbon black under high temperature; (4) Catalyst poisoning is easily caused by impurities, as the active centers of precious metals are extremely sensitive to sulfides and halides. (5) Catalysts have high requirements for reaction conditions and cannot adapt to a wide range of operating conditions. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a rhodium-based aerogel catalyst for partial oxidation of hydrogen production by oxygen cracking. Boron nitride aerogel as a catalyst carrier has significant advantages such as high specific surface area, high thermal stability, resistance to carbon deposition and chemical inertness. However, its surface lacks anchoring points, and the loaded metal often has poor resistance to sintering. After modification with rare earths, the activity, selectivity, stability, resistance to sintering and resistance to carbon deposition of the catalyst are greatly improved. The active component Rh has a low loading amount and exists in the form of highly dispersed clusters or single atoms on the surface of the rare earth-modified boron nitride aerogel carrier, with a very high atomic utilization rate.

[0005] According to one aspect of the present application, a rhodium-based aerogel catalyst is provided, wherein the rhodium-based aerogel catalyst is composed of a boron nitride aerogel carrier modified with a rare earth element and an active component rhodium supported on the boron nitride aerogel carrier modified with a rare earth element;

[0006] In the rhodium-based aerogel catalyst, the mass fraction of the active component rhodium is 0.05-0.5wt%, and the mass fraction of the rare earth element is 1-15wt%;

[0007] The rare earth element is selected from at least one of cerium, zirconium, lanthanum, yttrium, samarium and praseodymium.

[0008] The molar ratio of cerium to lanthanum is 4:1, and the mass fraction is 5 wt%.

[0009] According to another aspect of the present application, a method for preparing the above-mentioned rhodium-based aerogel catalyst is provided, comprising the following steps:

[0010] (1) immersing an equal volume of boron nitride aerogel in an aqueous solution containing a rare earth precursor, drying for 1, and calcining for 1 in air to obtain a boron nitride aerogel carrier modified with a rare earth element;

[0011] (2) An equal volume of a boron nitride aerogel carrier modified with a rare earth element is immersed in an aqueous solution containing a rhodium precursor, dried II, and calcined II in air to obtain the rhodium-based aerogel catalyst.

[0012] The rare earth precursor is selected from at least one of nitrates, hydrochlorides, acetates and sulfates of cerium, zirconium, lanthanum, yttrium, samarium and praseodymium.

[0013] The drying temperature is 60-150°C;

[0014] The drying time is 8 to 15 hours;

[0015] The temperature of the calcination I is 400-650°C;

[0016] The calcination time is 2 to 5 hours.

[0017] The rhodium precursor is selected from at least one of rhodium nitrate, rhodium chloride and rhodium acetate.

[0018] The temperature of the drying II is 60-150° C.;

[0019] The drying time of II is 8 to 15 hours;

[0020] The temperature of the calcination II is 400-650°C;

[0021] The calcination time of II is 2 to 5 hours.

[0022] According to another aspect of the present application, there is provided an application of the above-mentioned rhodium-based aerogel catalyst for catalyzing the cracking of low-carbon alkanes in the presence of oxygen to produce hydrogen.

[0023] The beneficial effects of this application include:

[0024] 1. The catalytic activity of the catalyst provided by the present invention far exceeds that of the catalyst with rare earth oxide as the carrier, and can obtain 80% alkane conversion rate at 600°C;

[0025] 2. The catalyst provided by the present invention has high hydrogen selectivity, which is close to 100%;

[0026] 3. The stability of the catalyst provided by the present invention far exceeds that of the catalyst with pure boron nitride as the carrier, and it has excellent anti-sintering and anti-carbon deposition performance, and the stability decreases by less than 1% within 48 hours;

[0027] 4. The catalyst provided by the present invention has a low rhodium loading, and the catalyst cost is lower than that of conventional rhodium-based catalysts;

[0028] 5. The catalyst synthesis method provided by the present invention is simple and easy to implement and suitable for large-scale preparation. DETAILED DESCRIPTION

[0029] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0030] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0031] Example 1

[0032] Weigh a certain amount of boron nitride aerogel as a carrier, immerse an equal volume of it in a mixed solution of lanthanum nitrate and cerium nitrate, stir evenly, dry at 80°C for 12 hours, and calcine at 500°C for 3 hours at a heating rate of 5°C / min to obtain BN / La-Ce powder. Take another equal volume of the above powder and immerse it in a rhodium trichloride solution, stir evenly, dry at 80°C for 12 hours, and calcine at 500°C for 2 hours at a heating rate of 5°C / min to obtain Rh / La-Ce / BN catalyst.

[0033] Example 2

[0034] A certain amount of cerium acetate and lanthanum acetate were weighed and mixed evenly, and then calcined at 800°C for 3 hours to obtain cerium lanthanum oxide powder. Then a certain amount of rare earth oxide powder was taken and immersed in rhodium nitrate solution in equal volume and stirred evenly. After drying at 120°C for 12 hours, it was calcined at 600 degrees for 4 hours at a heating rate of 5°C / min to obtain Rh / Ce-La catalyst.

[0035] Example 3

[0036] A certain amount of boron nitride aerogel was weighed as a carrier, an equal volume of it was immersed in a rhodium nitrate solution and stirred evenly, and after drying at 100°C for 12 h, it was calcined at 600°C for 3 h at a heating rate of 5°C / min to obtain a Rh / La-Ce / BN catalyst.

[0037] Example 4

[0038] Weigh a certain amount of boron nitride aerogel as a carrier, immerse an equal volume of it in a cerium sulfate solution and stir it evenly, dry it at 120°C for 12 hours, and then calcine it at 500°C for 3 hours at a heating rate of 5°C / min to obtain Ce / BN powder. Take another equal volume of the above powder and immerse it in a rhodium nitrate solution and stir it evenly, dry it at 120°C for 12 hours, and then calcine it at 500°C for 3 hours at a heating rate of 5°C / min to obtain Rh / Ce / BN catalyst.

[0039] Example 5

[0040] Weigh a certain amount of boron nitride aerogel as a carrier, immerse an equal volume of it in a lanthanum acetate solution and stir evenly, dry it at 100°C for 12 hours, and then calcine it at 550°C for 3 hours at a heating rate of 5°C / min to obtain La / BN powder. Take another equal volume of the above powder and immerse it in a rhodium trichloride solution and stir evenly, dry it at 100°C for 12 hours, and then calcine it at 600°C for 5 hours at a heating rate of 5°C / min to obtain Rh / La / BN catalyst.

[0041] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A rhodium-based aerogel catalyst, characterized in that: The rhodium-based aerogel catalyst is composed of a boron nitride aerogel carrier modified by a rare earth element and an active component rhodium supported on the boron nitride aerogel carrier modified by a rare earth element; In the rhodium-based aerogel catalyst, the mass fraction of the active component rhodium is 0.05-0.5wt%, and the mass fraction of the rare earth element is 1-15wt%; The rare earth element is selected from at least one of cerium, zirconium, lanthanum, yttrium, samarium and praseodymium.

2. A method for preparing the rhodium-based aerogel catalyst according to claim 1, characterized in that: The following steps are involved: (1) immersing an equal volume of boron nitride aerogel in an aqueous solution containing a rare earth precursor, drying for 1, and calcining for 1 in air to obtain a boron nitride aerogel carrier modified with a rare earth element; (2) An equal volume of a boron nitride aerogel carrier modified with a rare earth element is immersed in an aqueous solution containing a rhodium precursor, dried II, and calcined II in air to obtain the rhodium-based aerogel catalyst.

3. The preparation method according to claim 2, characterized in that: The rare earth precursor is selected from at least one of nitrates, hydrochlorides, acetates and sulfates of cerium, zirconium, lanthanum, yttrium, samarium and praseodymium.

4. The preparation method according to claim 2, characterized in that: The drying temperature is 60-150°C; The drying time is 8 to 15 hours; The temperature of the calcination I is 400-650° C.; The calcination time is 2 to 5 hours.

5. The preparation method according to claim 2, characterized in that: The rhodium precursor is selected from at least one of rhodium nitrate, rhodium chloride and rhodium acetate.

6. The preparation method according to claim 2, characterized in that: The temperature of the drying II is 60-150° C.; The drying time of II is 8 to 15 hours; The temperature of the calcination II is 400-650°C; The calcination time II is 2 to 5 hours.

7. An application of the rhodium-based aerogel catalyst according to claim 1, characterized in that: Used to catalyze the cracking of low-carbon alkanes in the presence of oxygen to produce hydrogen.