Hydrogenolysis

About: Hydrogenolysis is a research topic. Over the lifetime, 7673 publications have been published within this topic receiving 171501 citations.

Selective Hydrogenation for Fine Chemicals: Recent Trends and New Developments

Abstract: In this overview, recent trends and developments for the selective hydrogenation of multifunctional molecules are discussed and assessed from the point of view of fine chemicals synthesis. In a first part, the design and preparation of catalysts and ligands with interesting properties are summarized, particularly meant for the catalysis specialist. The following topics are described in some detail: How enantioselective homogeneous catalysts are designed and tested; new effective chiral monodentate phosphines; successful bidentate phosphines ligand families (with axially chiral biaryl- and ferrocenyl-based backbones, new phospholanes and with stereogenic phosphorus); novel bidentate ligand families with P-O and P-N bonds; and oxazoline-based ligands. A short overview on immobilized chiral complexes and of the toolbox of heterogeneous catalysis (bimetallic, colloidal and modified catalysts) concludes this chapter. In a second part, progress for selected catalytic transformations and generic selectivity problems is described, intended mainly for the organic chemist who has to solve specific synthetic problems. Emphasis is on the following topics: The enantioselective hydrogenation of olefins with various substitution patterns; the chemo- and enantioselective hydrogenation of ketones; the diastereo- and enantioselective hydrogenation of CN functions; the stereoselective hydrogenation of aromatic rings; chemoselectivity and hydroxylamine accumulation in the reduction of functionalized nitroarenes; chemoselectivity and new protecting groups for catalytic debenzylation; the mild hydrogenation of carboxylic acid derivatives; and the chemoselective hydrogenation of nitriles. In the last parts of the review, transfer hydrogenation and mechanistic issues are discussed, followed by a short conclusions and outlook paragraph.

Kinetics and Selectivity of the Fischer–Tropsch Synthesis: A Literature Review

Abstract: A critical review of the kinetics and selectivity of the Fischer–Tropsch synthesis (FTS) is given. The focus is on reaction mechanisms and kinetics of the water–gas shift and Fischer–Tropsch (FT) reactions. New developments in the product selectivity as well as the overall kinetics are reviewed. It is concluded that the development of rate equations for the FTS should be based on realistic mechanistic schemes. Qualitatively, there is agreement that the product distribution is affected by the occurrence of secondary reactions (hydrogenation, isomerization, reinsertion, and hydrogenolysis). At high CO and H2O pressures, the most important secondary reaction is readsorption of olefins, resulting in initiation of chain growth processes. Secondary hydrogenation of α-olefins may occur and depends on the catalytic system and the process conditions. The rates of the secondary reactions increase exponentially with chain length. Much controversy exists about whether these chain-length dependencies stem from differe...

Low-pressure hydrogenolysis of glycerol to propylene glycol

Abstract: Hydrogenolysis of glycerol to propylene glycol was performed using nickel, palladium, platinum, copper, and copper-chromite catalysts. The effects of temperature, hydrogen pressure, initial water content, choice of catalyst, catalyst reduction temperature, and the amount of catalyst were evaluated. At temperatures above 200 °C and hydrogen pressure of 200 psi, the selectivity to propylene glycol decreased due to excessive hydrogenolysis of the propylene glycol. At 200 psi and 200 °C the pressures and temperaures were significantly lower than those reported in the literature while maintaining high selectivities and good conversions. The yield of propylene glycol increased with decreasing water content. A new reaction pathway for converting glycerol to propylene glycol via an intermediate was validated by isolating the acetol intermediate.