Preparation, characterization and reactivity of Pd/Nb2O5 catalysts in hexa-1,5-diene hydrogenation

Palladium/niobia catalysts are prepared by various methods involving either gas or liquid phase reduction. Although giving rise to average or low disp ersion, the reduction of palladium precursors in a liquid medium (hydrazine or ethylene-glycol) appears to be a promising method since a low dispersio n favors the activity in the hydrogenation of hexa-1,5-diene in liquid phas e. The substitution of alumina by niobia improves the fractional selectivit y and the yield of hex-l-ene in all cases. A very good global selectivity i s also observed. (C)2000 Elsevier Science B.V. All rights reserved.