THERMAL-ACTIVATION OF SILICA AT TEMPERATURES BELOW 500-DEGREES-C

A simple low-temperature treatment (below 500 degrees C) of several ty pes of silica was found to induce catalytic activity toward hydrogen-d euterium exchange, the degree of which was measured with a pulse-flow microreactor. Silica samples were heated in a microreactor in the pres ence of an argon carrier gas. Pulses of hydrogen and deuterium gas mix tures were injected into the flow and the effluent stream was monitore d for H-2, D-2, and HD. In some cases equilibrium amounts of the efflu ent gases were observed. Activation of the silicas appeared to be rela ted to the dehydration of the silica surfaces. After activation, the s urface of one of the silicas, Cabosil M5, was found to catalyze the hy drogenation of ethylene to ethane and to catalyze extensive exchange w hen deuterium was used as the hydrogenation reagent. (C) 1994 Academic Press, Inc.