ACTIVITIES AND SELECTIVITIES OF COPPER/METAL-OXIDE CATALYSTS AT TEMPERATURES RELEVANT TO CHEMICAL HEAT-PUMPS BASED ON ISOPROPANOL/ACETONE INTERCONVERSIONS

摘要

Results are presented concerning the possible suitability of various oxide supported copper catalysts for utilization in proposed chemical heat pumps, featuring isopropanol dehydrogenation as a 'low' temperature endothermic process coupled with acetone hydrogenation as a higher temperature exothermic process. For each of those processes, separate determinations have been made of the temperature ranges within which adequate levels of pseudo-steady-state activity and selectivity were maintained at vapour/solid interfaces over Cu/Al_2O_3, Cu/Cr_2O_3, Cu/SiO_2 and Cu/TiO_2 catalysts. For acetone hydrogenation over Cu/Al_2O_3 and Cu/SiO_2, that range extended over 423-550 K. However, over Cu/Cr_2O_3 and Cu/TiO_2 it was restricted to 423-473 K, limited by insufficient activity at the lower end, and at the upper end by a fall-off in selectivity caused by onset of acetone oligomerization to C_6, C_9 and C_(12) ketones. Similar temperature ranges were found to be necessary for attainment of adequate levels of activity and selectivity for dehydrogenation of isopropanol vapour over oxide-supported copper catalysts. Again over Cu/TiO_2 materials, selectivity declined above 473 K owing to the formation of oligomeric ketone products. System modifications to overcome the indicated difficulties are briefly considered.