Effect of temperature and hydrogen concentration on the activity and selectivity of selected heterogeneous, noble-metal based catalysts in the hydrogenation of methylacetylene and propadiene

The Pd/Al2O3, Pd/TiO2 and Pt/Al2O3 catalysts obtained by the impregnation-redn. method were used for selective hydrogenation of MeC CH and CH2=C=CH2 (contained in the C-3 fraction stream from the steam cracking process) to MeCH=CH2. Pd-contg. catalysts showed higher activity and selectivity than Pt/Al2O3, but the excess of H-2 caused a decrease in their selectivity to a greater extent. In the presence of Pd/TiO2, a greater increase in the MeCH=CH2 content was obsd. than in Pd/Al2O3 at low temps., but at the same time higher concns. of residual MeC CH and CH2=C=CH2 were obsd. Under conditions of increased H-2 concn. and moderate temps., the Pd/TiO2 catalyst showed higher activity (and a slight decrease in selectivity), which makes it an interesting alternative to the Pd/Al2O3 catalysts commonly used in the process.