The current study describes the results on the selective hydrogenation of the 2-butyne-1,4-diol to 1,4-butanediol over Raney Ò nickel catalysts both in batch and in CSTR mode. The detailed kinetic analysis of the reaction in batch mode revealed the existence of three characteristic regions. In the first region, A, the starting 2-butyne-1,4-diol produces primarily cis-2-butene-1,4-diol.In the second region, B, the dominant species is cis-2-butene-1,4-diol, which is either hydrogenated to 1,4-butanediol or isomerizes to trans-2-butene-1,4-diol. In the third region, C, the accumulated 4-hydroxybutanal is slowly hydrogenated to 1,4-butanediol. When the same reaction was carried out in a CSTR mode, the only products detected initially are the 1,4-butanediol and n-butanol. The first by-product detected immediately after the end of the first stage is the linear hemiacetal between the 4-hydroxybutanal with 1,4-butanediol. This species has been used as convenient tracer for determining the length of the selective region of the catalyst performance.

A series of Anchored Wilkinson’s Catalysts were prepared by the reaction of the homogeneous Wilkinson catalyst with alumina/heteropoly acid support materials. It was found that the catalytically active species from these materials were unique in that they had only a single triphenylphosphine and a heteropoly acid as ligands giving these catalysts distinctive steric and electronic characteristics. These catalysts were used to promote the hydrogenation of 1-hexene and limonene with substrate to catalyst ratios of 10,000 and 7,500 respectively. The results were compared with those obtained using the homogeneous Wilkinson and 1% Rh/Al2O3 catalysts with respect to catalyst activity and stability as well as the reaction selectivity as measured by the amount of double bond isomerization observed. The observed rates of hydrogen uptake and double bond isomer formation in the hydrogenations of both 1-hexene and limonene follow the same order with respect to the nature of the heteropoly acid ligand used to anchor the Wilkinson catalyst to the alumina: silicotungstic acid > phosphotungstic acid > phosphomolybdic acid > silicomolybdic acid for hydrogen addition and the reverse for isomerization. This consistency provides a measure of the electronic character of these Keggin heteropoly acids when acting as ligands. In contrast to the reactions observed with the anchored catalysts the homogeneous Wilkinson catalyst was incapable of completing these high substrate/catalyst ratio hydrogenations. It became deactivated at about 85% 1-hexene conversion and only 10% limonene hydrogenation. As compared with the anchored catalysts the supported Rh promoted more isomerization of 1-hexene and limonene while the hydrogenation of the trisubstituted double bond in p-menthene was more difficult over the supported metal catalyst than with the sterically more accessible anchored Wilkinson catalysts.

The conversion of nitrobenzene (NB) to p-aminophenol (PAP) takes place by way of an initial partial hydrogenation to produce phenylhydroxyl amine (PHA) which then undergoes an in situ acid-catalyzed rearrangement to PAP. This reaction is most commonly run using Pt/C catalysts in the presence of aqueous sulfuric acid and a surfactant to assist in dispersing the NB throughout the reaction medium. The yield of PAP is closely related to those reaction parameters which facilitate first the partial hydrogenation step and second the acid-promoted rearrangement before further hydrogenation to aniline can take place. The effect which a number of reaction parameters such as hydrogen pressure, reaction temperature, stirring rate, and the amounts of NB, the catalyst, and the surfactant present in the reaction mixture had on the rate and selectivity of the hydrogenation was examined. Optimization of these parameters led to the formation of PAP at a selectivity (PAP/AN) of 5.4 with a productivity of over 80,000 g PAP/g Pt/h.

Net propylene glycol (1,2 propanediol) yields of up to 94% at 100% glycerol conversion have been achieved over a fixed bed Raney Ò Cu catalyst in trickle bed mode, at relatively low total pressure, 14 bar (200 psig), and minimal feedstock dilution (20 wt% water). The main identified byproducts are ethylene glycol and ethanol (each \2%), with methanol and 1,3 diol both \1%. The other key operating parameters for high yields are a narrow optimum in temperature (near 205°C), and a high H 2 / liquid flow ratio, about 375/0.05 by volume. The effects of chromium promotion have also been studied for effects on side reactions and rates. Our evidence points to initial dehydrogenation as the rate-limiting step in a likely three step mechanism.