The hydrogenolysis of glycerol was performed in an autoclave at temperatures between 190 and 225 • C and at a H 2 pressure of 5 MPa over a CuO/ZnO catalyst prepared by an oxalate gel (OG) method. Compared to a CuO/ZnO catalyst prepared by coprecipitation, much higher conversions of glycerol and space-time yields up to 9.8 g propylene glycol g Cu -1 h -1 are achieved with CuO/ZnO-OG, whereas both catalysts produced propylene glycol with selectivities of about 90%. Additionally, the influence of the temperature and the solvent was examined. Compared to a conversion of glycerol of only 5% in an aqueous glycerol solution, the use of 1,2-butanediol as a solvent leads to a high conversion of 55%. Moreover, experiments were carried out in pure glycerol and from transmission electron microscopy images of fresh and spent catalysts, it was obvious that the morphology of the catalyst changed during the reaction. By X-ray diffraction and N 2 O chemisorption, it was proved that a tremendous loss of copper surface area occurred during the hydrogenolysis of glycerol. Taking together the influence of the solvent on the conversion of glycerol and the results of the catalyst characterization, it can be concluded that water, as an unavoidable by-product of the reaction, is responsible for a strong deactivation of the catalyst.
A new catalyst system was used in the liquid phase hydrogenation of benzene to cyclohexene containing only an aqueous solution of Ru/La 2 O 3 and a very small quantity of sodium dicyanamide (NaDCA). This additive considerably improves the catalyst performance compared to DCA based ionic liquids. The effects of the amount of NaDCA and metal loading of the catalyst were investigated and a high initial selectivity to cyclohexene of 70% was reached.
A simple Pd/SiO2 catalyst which was modified with the ionic liquid [BMPL][DCA] gave an excellent yield of 88% towards cis-2-hexene in the stereoselective hydrogenation of 2-hexyne. The catalyst outperforms, even at full conversion, the commonly used lead-poisoned, toxic Lindlar catalyst and supported colloidal-based Pd as well.
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