阅读说明：本技术 一种负载型钌基磷化物催化剂及其制备方法 (Supported ruthenium-based phosphide catalyst and preparation method thereof ) 是由 贺宇飞 马瑞 杨甜星 李殿卿 冯俊婷 刘雅楠 于 2020-07-09 设计创作，主要内容包括：本发明公开了一种负载型钌基磷化物催化剂及制备方法,所采用的制备方法是以SiO<Sub>2</Sub>、Al<Sub>2</Sub>O<Sub>3</Sub>等氧化物为载体,将磷酸与钌源分别以强静电吸附-浸渍法固载至载体上,并通过焙烧得到PO<Sub>x</Sub>-RuO<Sub>y</Sub>/ZT催化剂前驱体,利用还原气氛对催化剂前驱体进行还原,在热驱动下RuO<Sub>y</Sub>和PO<Sub>x</Sub>发生固-固反应,形成Ru-P键,得到Ru-P/ZT催化剂。该催化剂活性组分Ru-P纳米颗粒尺寸在2-6nm之间。磷源及钌盐与载体之间的强静电吸附作用使得磷化物纳米颗粒分散均匀,尺寸较小,且制备过程反应条件温和、简单绿色。该钌基磷化物催化剂在丙烷脱氢反应中表现出了优异的选择性和稳定性。(The invention discloses a load type ruthenium phosphide catalyst and a preparation method thereof, wherein the adopted preparation method is SiO 2 、Al 2 O 3 When the oxide is used as a carrier, phosphoric acid and a ruthenium source are respectively immobilized on the carrier by a strong electrostatic adsorption-impregnation method, and PO is obtained by roasting x ‑RuO y a/ZT catalyst precursor, reducing the catalyst precursor with a reducing atmosphere, RuO under thermal drive y And PO x Solid-solid reaction is carried out to form Ru-P bond, and the Ru-P/ZT catalyst is obtained. The active component Ru-P of the catalyst has the nano-particle size of 2-6 nm. The strong electrostatic adsorption between the phosphorus source and the ruthenium salt and the carrier leads phosphide nano-particles to be separatedThe powder is uniform, the size is small, and the reaction condition in the preparation process is mild, simple and green. The ruthenium-based phosphide catalyst shows excellent selectivity and stability in the propane dehydrogenation reaction.)

1. A preparation method of a supported ruthenium-based phosphide catalyst comprises the following specific preparation steps:

A. mixing a phosphoric acid solution with the mass concentration of 40-90% with deionized water to prepare a phosphoric acid impregnation solution, dropwise adding the phosphoric acid impregnation solution onto the carrier, stirring the carrier while dropwise adding to ensure uniform loading until the carrier is saturated in water absorption; drying in an oven at 80-130 deg.C for 4-24h, and calcining at 200-600 deg.C for 2-5 h to obtain phosphorus-loaded materialSupport for oxides, denoted PO_xZT, x represents the atomic ratio O/P in the phosphorus oxide, x is in the range of 2.5-3.5;

the content of phosphoric acid in the phosphoric acid impregnation liquid is determined according to the Ru/P ratio set by the target catalyst, the mass concentration of the phosphoric acid impregnation liquid is 3-50%, and the volume of the phosphoric acid impregnation liquid is required to enable the carrier ZT to be adsorbed and saturated; the carrier is SiO₂、Al₂O₃、MgAl₂O₄Any one of a ZSM-5 molecular sieve, an SBA-15 molecular sieve, an SUZ-4 molecular sieve and an SAPO-34 molecular sieve;

B. dissolving soluble Ru salt in deionized water, fully dissolving by ultrasonic, and adjusting the pH value to 4-12 by using an alkaline solution or an acidic solution; the Ru salt solution was added dropwise to the PO_xIn ZT, dropwise adding under stirring until the carrier is saturated with water, drying in an oven at 80-130 deg.C for 4-24h, and calcining at 200-600 deg.C for 2-5 h to obtain precursor loaded with phosphorus oxide and ruthenium oxide, represented as PO_x-RuO_yZT, y represents the atomic ratio of O/Ru in the ruthenium oxide, and y is 1.5-4.0;

the dosage of the deionized water is calculated according to the water absorption of the carrier based on the water absorption saturation of the carrier; the Ru salt is Ru (NH)₃)₆·Cl₃、K₂Ru(NO)Cl₅、K₂RuCl₆、Ru(NH₃)₅H₂O·Cl₃The amount of the Ru salt is determined according to the load of the metal Ru being 0.3-10%; the alkaline solution is one of ammonia water, sodium hydroxide or sodium carbonate; the acid solution is hydrochloric acid or nitric acid; wherein the molar concentration of the sodium hydroxide and the sodium carbonate is 1-3 mol/L; wherein the mass concentration of the hydrochloric acid and the nitric acid is 10-30%;

C. the PO obtained in the step B_x-RuO_yThe ZT is reduced for 1 to 10 hours in a reducing atmosphere at the temperature of 400-750 ℃; wherein the gas flow rate is 20-100mL/min, and the temperature rise rate of the atmosphere furnace is 2-20 ℃/min; obtaining a ruthenium-based phosphide catalyst expressed as Ru-P/ZT; the reducing atmosphere is 5-40% of H₂/N₂Or 5-40% CO/N₂One kind of (1).

2. The supported ruthenium-based phosphide catalyst prepared according to the process of claim 1, represented as Ru-P/ZT, wherein ZT represents a support and ZT is SiO₂、Al₂O₃、MgAl₂O₄Any one of a ZSM-5 molecular sieve, an SBA-15 molecular sieve, an SUZ-4 molecular sieve and an SAPO-34 molecular sieve; Ru-P is an active component, wherein the molar ratio of P/Ru is 0.1-75, the active component particles are 2-6nm, and the Ru loading is 0.3-10%; the Ru loading is the mass percentage of metal Ru in the carrier.

Technical Field

The invention belongs to the field of catalyst preparation, and particularly relates to a supported ruthenium-based phosphide catalyst and a preparation method thereof.

Background

As a supporting scientific technology in the petroleum industry, the chemical industry, the energy industry and many other industries, the catalytic technology plays a key role in solving the important problems of energy, environment and the like existing in the current development, wherein the development of a novel high-efficiency catalyst is the core power of the progress of the catalytic technology. The transition metal phosphide has a special crystal structure and noble metal-like properties, and shows good catalytic performance in catalytic hydrodesulfurization, hydrodenitrogenation and electrochemical hydrogen production reactions, so that the transition metal phosphide catalyst is developed rapidly in recent years, and the application field is expanded continuously.

The metal Ru belongs to rare platinum group metal elements, has lower price compared with platinum, and is a metal catalyst with wide application prospect. However, the most thermodynamically stable structure of Ru is a hexagonal close-packed structure, and most transition metals (Pt, Cu, Ir, Pd, Au, etc.) are face-centered cubic structures, and it is known from phase diagrams that achieving bulk alloying of Ru with metal elements of different lattice structures is very challenging even above the melting point, so that modification of the geometric structure and electronic structure of Ru atoms by introducing a second metal is greatly limited, and application thereof in catalytic reactions is hindered. In the transition metal phosphide, phosphorus atoms can form an alloy-like structure by bonding with metal Ru atoms, so that the electronic structure and surface properties of the Ru atoms can be modified to a greater extent, and the catalytic performance is changed. The traditional preparation method of transition metal phosphide comprises a high-temperature phosphating method of elemental metal and red phosphorus and PH₃Gas reduction method, J.Catal.,2006,237(1), 118-130 at pH₃Processing metallic nickel at 250 ℃ as a phosphorus source to prepare nickel phosphide Ni₂P catalyst, which has harsh reaction conditions and involves a large amount of highly toxic PH₃The gas escapes. Therefore, in recent years, a precursor and trioctylphosphine solvothermal method, a metal phosphate temperature programmed reduction method, and the like have been developed. The document J.Am.chem.Soc.,2017,139,15,5494-5502 reports rhodium R acetylacetonateh(acac)₃Takes n-trioctylphosphine TOP as a phosphorus source and oleylamine as a solvent as a metal source to successfully synthesize Rh through a hydrothermal reaction₂P nanocubes. The process reactants are highly flammable and corrosive, require oxygen-free operation, are difficult and dangerous to operate. The document Angew. chem. int. Ed.,2014,53, 14433->650 ℃) and reducing metal phosphate in hydrogen atmosphere to prepare molybdenum phosphide MoP, and the phosphide obtained by the method has large particle size and irregular appearance, and most of the phosphide particles are agglomerated particles.

In summary, the common preparation method of the transition metal-based phosphide at present has harsh conditions, extremely toxic substances such as phosphine and the like are used or accompanied in the preparation process, and the size of the active component of the catalyst is difficult to control. The invention aims to provide a ruthenium-based phosphide catalyst with high catalytic activity prepared under an environment-friendly condition.

Disclosure of Invention

The invention aims to provide a kind of supported ruthenium-based phosphide catalyst, and also aims to provide a preparation method of the catalyst. The catalyst is suitable for propane dehydrogenation.

The supported ruthenium-based phosphide catalyst provided by the invention is expressed as Ru-P/ZT, wherein ZT represents a carrier, and ZT is SiO₂、Al₂O₃、MgAl₂O₄Any one of a ZSM-5 molecular sieve, an SBA-15 molecular sieve, an SUZ-4 molecular sieve and an SAPO-34 molecular sieve; Ru-P is an active component, wherein the molar ratio of P/Ru is within the range of 0.1-75, the active component particles are between 2-6nm, and the Ru loading is between 0.3-10%; the catalyst forms Ru-P bonds, and continuous sites of Ru atoms are separated by P atoms. The Ru loading is the mass percentage of metal Ru in the carrier.

The preparation method of the supported ruthenium-based phosphide catalyst provided by the invention is characterized in that phosphoric acid and a ruthenium source are respectively immobilized on a carrier by a strong electrostatic adsorption-impregnation method, the phosphoric acid is firstly supported, and the phosphoric acid is roasted into an oxide form; loading ruthenium source, adjusting pH of the solution according to the property of the carrier, ensuring metal ions to be uniformly dispersed to the surface of the carrier by using strong electrostatic adsorption, and roasting again to obtain uniformly dispersed PO_x-RuO_ya/ZT catalyst precursor; finally obtaining the ruthenium-based phosphide catalyst with smaller size and uniform dispersion through reduction in a reducing atmosphere.

The specific preparation steps of the supported ruthenium-based phosphide catalyst are as follows:

A. mixing a phosphoric acid solution with the mass concentration of 40-90% with deionized water to prepare a phosphoric acid impregnation solution, dropwise adding the phosphoric acid impregnation solution onto the carrier, stirring the carrier while dropwise adding to ensure uniform loading until the carrier is saturated in water absorption; drying in an oven at 80-130 deg.C for 4-24h, and calcining at 200-600 deg.C for 2-5 h to obtain a phosphorus oxide-loaded carrier represented as PO_xZT, x represents the atomic ratio O/P in the phosphorus oxide, and x is in the range of 2.5 to 3.5.

The content of phosphoric acid in the phosphoric acid impregnation liquid is determined according to the Ru/P ratio set by the target catalyst, the mass concentration of the phosphoric acid impregnation liquid is within the range of 3-50%, and the volume of the phosphoric acid impregnation liquid is required to enable the carrier ZT to be adsorbed and saturated; this volume can be determined by the water absorption of the carrier. The method for testing the adsorption rate comprises the following steps: weighing 5g of carrier in a 50ml beaker, measuring 20ml of distilled water, slowly pouring the carrier into deionized water, standing at room temperature and normal pressure for 12h, and filtering off excessive water. The water absorption a of the carrier is then: a ═ 20-V)/5, where V is the filtered water volume (mL).

The carrier is SiO₂、Al₂O₃、MgAl₂O₄One of ZSM-5 molecular sieve, SBA-15 molecular sieve, SUZ-4 molecular sieve and SAPO-34 molecular sieve.

B. Dissolving soluble Ru salt in deionized water, fully dissolving by ultrasonic, and adjusting the pH value to 4-12 by using an alkaline solution or an acidic solution; the Ru salt solution was added dropwise to the PO_xIn ZT, dropwise adding under stirring until the carrier is saturated with water, drying in an oven at 80-130 deg.C for 4-24h, and calcining at 200-600 deg.C for 2-5 h to obtain precursor loaded with phosphorus oxide and ruthenium oxide, represented as PO_x-RuO_yZT, y represents the atomic ratio of O/Ru in the ruthenium oxide, and y is 1.5-4.0;

the dosage of the deionized water is calculated according to the water absorption of the carrier based on the water absorption saturation of the carrier; the Ru salt is Ru(NH₃)₆·Cl₃、K₂Ru(NO)Cl₅、K₂RuCl₆、Ru(NH₃)₅H₂O·Cl₃The amount of the Ru salt is determined according to the load of the metal Ru being 0.3-10%; the alkaline solution is one of ammonia water, sodium hydroxide or sodium carbonate; the acid solution is hydrochloric acid or nitric acid. Wherein the molar concentration of the sodium hydroxide and the sodium carbonate is 1-3 mol/L; wherein the mass concentration of the hydrochloric acid and the nitric acid is 10 to 30 percent.

C. To PO_x-RuO_ythe/ZT is reduced for 1 to 10 hours in a reducing atmosphere at the temperature of 400-750 ℃, wherein the gas flow rate is 20 to 100mL/min, and the temperature rising rate of the atmosphere furnace is 2 to 20 ℃/min; the ruthenium-based phosphide catalyst was obtained and was designated as Ru-P/ZT.

The reducing atmosphere is 5-40% H₂/N₂、5-40％CO/N₂One kind of (1).

Characterization of the catalyst obtained:

FIG. 1 shows Ru-P/SiO prepared in example 1₂As shown in the electron microscope photograph (a) and the statistical result (b) of the particle size of the catalyst, the metal phosphide particles in the obtained supported catalyst are well dispersed on the surface of the carrier, the particle size is uniform, the particle size is small, and the average particle size is 2.8 nm.

FIG. 2 shows Ru-P/SiO prepared in example 1₂The extended X-ray absorption fine structure of the catalyst can be obtained by fitting, and the coordination number ratio of Ru-P bond to Ru-Ru bond is CN_Ru-P/CN_Ru-RuAt 1.0, the formation of ruthenium-based phosphide catalyst was confirmed.

FIG. 3 shows Ru-P/SiO films prepared in example 2₂The electron microscope photograph (a) and the particle size statistical result (b) of the catalyst show that the ruthenium phosphide particles in the obtained supported catalyst are uniformly dispersed on the surface of the carrier, the particle size distribution range is narrow, the particle size is small, and the average particle size is 2.8 nm.

FIG. 4 shows a single metal Ru catalyst (curve 1) and Ru-P/SiO prepared in example 2₂CO in situ IR spectrum of catalyst (curve 2), Ru-P/SiO, compared to monometallic Ru₂CO bridge adsorption Peak in catalyst (1998 cm)^-1) And linear adsorption peak (2025 cm)^-1) Disappeared and is at 2150cm^-1-2050cm^-1There appears relatively weak Ru⁺-CO line adsorption peak, indicating that Ru consecutive sites are separated.

FIG. 5 shows Ru-P/Al prepared in example 3₂O₃From the electron micrograph (a) and the particle size statistical result (b) of the catalyst, it can be seen that the ruthenium phosphide particles in the supported catalyst prepared in example 3 were well dispersed on the surface of the support, and the particles were uniform and small in size, and had an average particle size of 3.1 nm.

FIG. 6 shows Ru-P/Al prepared in example 3₂O₃The extended X-ray absorption fine structure of the catalyst can be fitted to obtain a Ru-Ru bond length ofHas a Ru-P bond length ofRatio of coordination number of Ru-P bond to Ru-Ru bond CN_Ru-P/CN_Ru-Ru0.15, indicating that a ruthenium-based phosphide catalyst was formed.

FIG. 7 shows Ru-P/SiO in example 1₂Catalyst (Curve 1) and Ru-P/SiO in example 2₂Catalyst (curve 2) propylene selectivity as a function of propane conversion in the propane dehydrogenation reaction at 550 ℃. As can be seen from the graph, the Ru-P/SiO prepared in example 1 increased with propane conversion from 5% to 25%₂Propylene selectivity of the catalyst is always maintained>93% Ru-P/SiO prepared in example 2₂Propylene selectivity of the catalyst is always maintained>83％。

FIG. 8 shows Ru-P/SiO in example 1₂Catalyst (Curve 1), Ru-P/SiO in example 2₂Catalyst (curve 2) propane conversion at 550 ℃ over time in the propane dehydrogenation reaction. As can be seen from the figure, the catalyst has better stability, and the Ru-P/SiO prepared in example 1₂The deactivation constant of the catalyst is only 0.107h within 2h of reaction time^-1Ru-P/SiO prepared in example 2₂The deactivation constant of the catalyst is 0.115h within 2h of reaction time^-1。

The invention has the beneficial effects that: by using a strong electrostatic adsorption-impregnation method with SiO₂、Al₂O₃Taking phosphoric acid as a phosphorus source, taking the hydroxyl functional groups on the surface of the carrier to generate strong adsorption with the phosphoric acid, and roasting to take PO as the phosphorus source_xImmobilizing the species to a carrier; then, the Ru source is immobilized on the surface of the carrier by using a similar method to obtain PO_x-RuO_ya/ZT catalyst precursor. Reducing the catalyst precursor under a reducing atmosphere, RuO under thermal drive_yAnd PO_xSolid-solid reaction occurs to generate Ru-P bond. According to the method, the phosphide nanoparticles are uniformly dispersed and have small size under the strong electrostatic adsorption action of the precursor and the carrier, and the regulation and control of the Ru-based phosphide structure and the catalytic performance are realized by adjusting the molar ratio of phosphorus to ruthenium. The reaction conditions in the preparation process are mild, simple and green. The ruthenium-based phosphide catalyst prepared by the method has excellent selectivity and stability in propane dehydrogenation reaction.

Description of the drawings:

FIG. 1 shows Ru-P/SiO films prepared in example 1₂Electron micrograph (a) and particle size statistics (b) of the catalyst.

FIG. 2 shows Ru-P/SiO in example 1₂Extended X-ray absorption fine structure results of the catalyst.

FIG. 3 shows Ru-P/SiO films prepared in example 2₂Electron micrograph (a) and particle size statistics (b) of the catalyst.

FIG. 4 shows a single metal Ru catalyst (Curve 1) and Ru-P/SiO prepared in example 2₂CO in situ IR spectrum of catalyst (curve 2).

FIG. 5 shows Ru-P/Al prepared in example 3₂O₃Electron micrograph (a) and particle size statistics (b) of the catalyst.

FIG. 6 shows Ru-P/Al in example 3₂O₃Extended X-ray absorption fine structure results of the catalyst.

FIG. 7 shows Ru-P/SiO powders in example 1₂Catalyst (Curve 1), Ru-P/SiO in example 2₂(Curve 2) catalyst propylene selection in propane dehydrogenationPerformance as a function of propane conversion.

FIG. 8 shows Ru-P/SiO films, respectively, in example 1₂Catalyst (Curve 1), Ru-P/SiO in example 2₂Catalyst (curve 2) propane conversion over time in the propane dehydrogenation reaction.

The specific implementation mode is as follows: