Phosphorus-based catalysts hydrogenation

The dispersions were obtained by emulsification via ultrasonication of a toluene solution of the unsaturated homopolymer in an aqueous surfactant solution. This was followed by exhaustive hydrogenation with Wilkinson s catalyst at 60°C and 80 bar H2 to produce a dispersion with an average particle size of 35 nm (dynamic light scattering and transmission electron microscopy analyses). The same a,co-diene was used as comonomer in the ADMET polymerization of a phosphorus-based monomer, also containing two 10-undecenoic acid moieties... 

It is concluded that phosphorus shows no effect or only a very small positive effect on thiophene HDS, but it decreases the selectivity for hydrogenated products with Mo/Al catalysts. However, the presence of phosphorus seems to be beneficial in promoted molybdenum-based catalysts, especially NiMoP/Al. 

Tungsten-based hydrotreating catalysts have been studied much less than the classical molybdenum-based catalysts. It is expected, however, that phosphorus addition should lead to similar effects in both cases since tungsten is chemically similar to molybdenum. Atanasova et al. (101) reported that phosphorus increases the thiophene HDS activity, especially that of a sequentially impregnated NiW—P/Al catalyst. Halachev et al (135) found that a maximum hydrogenation activity for naphthalene conversion is attained when the catalyst contains 0.6 wt% P2O5. Cruz Reyes et al (58) reported that phosphorus on a W/Al catalyst notably enhances gas oil HDS and pyridine HDN. 

Effects of phosphorus have also been proposed from different points of view. First, phosphorus may decrease the polarization of the Mo—S bond and therefore increase its covalent character. Since molybdenum-based catalysts with highly covalent Mo —S bonds are supposed to have high HDS activities, phosphorus can thus improve HDS activity (84). Second, the presence of phosphorus increases the formation of octahedral molybdenum, cobalt, and nickel oxo-species which could be the precursors of the catalyti-cally active phase (38,88). Finally, phosphorus strongly promotes hydrogen activation in MoP/Al catalysts (59), which could be beneficial for all the hydrotreating reactions. 

Quinoxaline 1-oxide (32) can be reduced to the parent base by hydrogenation in the presence of a Raney nickel catalyst or by treatment with phosphorus tribromide. Reaction of the N-oxide with acetic anhydride gives initially a mixture of quinoxaline (33) and quinoxalin-2-one (34) but on more prolonged reaction a third product, l-(2-quinoxalinyl)-quinoxalin-2-one (35), is formed. ... 

The ability to efficiently synthesize enantiomerically enriched materials is of key importance to the pharmaceutical, flavor and fragrance, animal health, agrochemicals, and functional materials industries [1]. An enantiomeric catalytic approach potentially offers a cost-effective and environmentally responsible solution, and the assessment of chiral technologies applied to date shows enantioselective hydrogenation to be one of the most industrially applicable [2]. This is not least due to the ability to systematically modify chiral ligands, within an appropriate catalyst system, to obtain the desired reactivity and selectivity. With respect to this, phosphorus(III)-based ligands have proven to be the most effective. 

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