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Incipient wetness impregnation (IW or IWI), also called capillary impregnation or dry impregnation, is a commonly used technique for the synthesis of heterogeneous catalysts. Typically, the active metal precursor is dissolved in an aqueous or organic solution. Then the metal-containing solution is added to a catalyst support containing the same ...
The Phillips catalyst is prepared by impregnating high surface area silica gel with chromium trioxide or related chromium compounds. The solid precatalyst is then calcined in air to give the active catalyst. Only a fraction of the chromium is catalytically active, a fact that interferes with elucidation of the catalytic mechanism.
During wet impregnation, the porous particles are dissolved in the extractant and allowed to soak with the respective fluid. [8] In this approach, the particles are either contacted with a precalculated amount of extractant, which completely soaks into the porous matrix, or the particles are contacted with an excess of extractant.
In chemistry, a catalyst support is a material, usually a solid with a high surface area, to which a catalyst is affixed. [1] The activity of heterogeneous catalysts is mainly promoted by atoms present at the accessible surface of the material. Consequently, great effort is made to maximize the specific surface area of a catalyst. One popular ...
ROMP reaction giving polynorbornene. Like most commercial alkene metathesis processes, this reaction does not employ a well-defined molecular catalyst. Heterogeneous catalysis consists of catalysts and substrates in different physical states. The catalyst is typically in solid phase. [6]
A third component of most catalysts is a carrier, a material that determines the size and the shape of catalyst particles. The preferred carrier is microporous spheres of amorphous silica with a diameter of 30–40 mm. During the catalyst synthesis, both the titanium compounds and MgCl 2 are packed into the silica pores
Hoveyda–Grubbs catalysts are easily formed from the corresponding Grubbs catalyst by the addition of the chelating ligand and the use of a phosphine scavenger like copper(I) chloride: [16] The second-generation Hoveyda–Grubbs catalysts can also be prepared from the 1st generation Hoveyda–Grubbs catalyst by the addition of the NHC: [15]
The Woodward cis-hydroxylation (also known as the Woodward reaction) is the chemical reaction of alkenes with iodine and silver acetate in wet acetic acid to form cis-diols. [1] [2] (conversion of olefin into cis-diol) The reaction is named after its discoverer, Robert Burns Woodward. The Woodward cis-hydroxylation