Search results
Results from the WOW.Com Content Network
Since then catalysts have been in use in a large portion of the chemical industry. In the start only pure components were used as catalysts, but after the year 1900 multicomponent catalysts were studied and are now commonly used in the industry. [1] [2] In the chemical industry and industrial research, catalysis play an important role.
In cooperative catalysis, chemical species that improve catalytic activity are called cocatalysts or promoters. In tandem catalysis two or more different catalysts are coupled in a one-pot reaction. In autocatalysis , the catalyst is a product of the overall reaction, in contrast to all other types of catalysis considered in this article.
Oxidation catalysis is conducted by both heterogeneous catalysis and homogeneous catalysis. In the heterogeneous processes, gaseous substrate and oxygen (or air) are passed over solid catalysts. Typical catalysts are platinum, and redox-active oxides of iron, vanadium, and molybdenum.
Common Lewis acid catalysts are based on main group metals such as aluminum, boron, silicon, and tin, as well as many early (titanium, zirconium) and late (iron, copper, zinc) d-block metals. The metal atom forms an adduct with a lone-pair bearing electronegative atom in the substrate, such as oxygen (both sp 2 or sp 3), nitrogen, sulfur, and ...
Heterobimetallic catalysis is an approach to catalysis that employs two different metals to promote a chemical reaction. Included in this definition are cases ( Scheme 1 ) where: 1 ) each metal activates a different substrate ( synergistic catalysis , used interchangeably with the terms "cooperative" and "dual" catalysis.
General chemical structure of a metallocene compound, where M is a metal cation. A metallocene is a compound typically consisting of two cyclopentadienyl anions (C 5 H − 5, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula (C 5 H 5) 2 M. Closely related to the metallocenes are the metallocene derivatives, e.g. titanocene dichloride or ...
Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...
This type of catalysis allows for the functionalization of simple alkenes into aldehydes and gives a remarkably useful handle to generate other functional groups. This transformation can be carried out using a cobalt or rhodium catalyst in a hydrogen / carbon monoxide atmosphere and consists of four stages: metal insertion, migratory insertion ...