The precious metal catalysts are mainly based on platinum group metals (PGM) including platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru), iridium (Ir), osmium (Os), etc. as catalytically active component of (i) heterogeneous catalyst of carrier type and a various types of (ii) homogeneous catalysts of platinum group metal including inorganic compounds and organic metal complex. Platinum group metals are not fully filled within d electronic orbits. The surface is easy to adsorb reactants, and the strength is moderate. Thus, it is conducive to the formation of intermediate "active compounds" with comprehensive excellent characteristics of highly catalytic activity, high temperature resistance, oxidation resistance, corrosion resistance, etc.. The PGM becomes the most important catalyst material.
According to the type of catalytic reaction, precious metal catalysts can be divided into two categories: homogeneous catalyst and heterogeneous catalyst.The homogeneous catalysts are usually soluble compounds (salts or complexes), such as palladium chloride, rhodium chloride, palladium acetate, rhodium carbonyl, triphenylphosphine rhodium carbonyl, rhodium iodide, and the like. The heterogeneous catalyst is an insoluble solid, and its main forms are a wire mesh state and a porous inorganic carrier supported metal state. Metal wire mesh catalysts (such as platinum mesh, platinum rhodium alloy mesh, etc.) have limited applications in scope and quantity. The most common heterogeneous catalysts of the precious metals are Pt/A12O3, Pd/C, Rh/SiO2, Pt-Pd/Al2O3, Pt-Rh/Al2O3, etc.. In all catalytic reactions, heterogeneous catalytic reactions account for 80% to 90%. According to the shape of the carrier, the supported catalyst can be divided into particulate, spherical, columnar and honeycomb. According to the main active metals of catalysts, platinum catalysts, palladium catalysts, rhodium catalysts and ruthenium catalysts are commonly used. Noble metal catalysts are highly valued for their excellent activity, selectivity, and stability. They are widely used in the reactions such as hydrogenation, dehydrogenation, oxidation, reduction, isomerization, aromatization, cracking, and synthesis, also play a very important role in the industries of petrochemical, medicine, environmental protection and new energy, automobile exhaust emission control and other fields.
The main application performances of the catalyst are as follows (1) Activity. It is a standard to measure the efficiency of the catalyst. In industry, it is usually expressed as the weight or volume of products per unit time for certain weight or volume of catalyst under certain conditions. (2) Selectivity. Referring to the specificity of the role of the catalyst, that is, under certain conditions, a certain catalyst only accelerates a certain chemical reaction. The selectivity is usually expressed as a percentage or the ratio of the moles of the expected product obtained after the reaction to the moles of the raw materials participating in the reaction. (3) Stability. Referring to the ability of the catalyst to maintain its activity and selectivity during use, usually expressed in terms of service life. The performance of the catalyst depends not only on the inherent characteristics of the active metal (atomic electronic structure, etc.), but also on its crystal structure, particle size, specific surface area, pore structure and dispersion state. In addition, the co-catalyst and/or carrier also have an important effect on the performance of the catalyst.
Evaluation of performance characterization of common precious metal catalyst materials
Zhejiang Micro General New Catalytic Materials Co., Ltd. can (i) provide the customers with testing service of physical and chemical performance for research on the precious metal compounds with the fully automatic evaluation devices; (ii) carry out research on evaluation and services such as catalytic activity, selectivity, and stability; (iii) use the instruments to accurately characterize and analyze the content of precious metals, the catalyst micrograph and phase structure; the molecular structure, active component, surface composition, adsorption state, catalytic mechanism or catalytic kinetics and related ones.
Application test of precious metal catalyst selection
According to the different reaction types of catalysts used by catalyst customers, the research and development department of WeiTong Company can use existing organic synthesis equipment for catalyst evaluation and selection, provide the customers with (i) efficient and suitable catalyst varieties and (ii) the following type reactions for the selection test:
(1) Catalytic hydrogenation reaction,
(2) Catalytic hydrogenolysis reaction,
(3) Cross-coupling reaction.
