Thermal Activation of Silica at Temperatures Below 500°C

A simple low-temperature treatment (below 500°C) of several types of silica was found to induce catalytic activity toward hydrogen-deuterium exchange, the degree of which was measured with a pulse-flow microreactor. Silica samples were heated in a microreactor in the presence of an argon carrier gas. Pulses of hydrogen and deuterium gas mixtures were injected into the flow and the effluent stream was monitored for H2, D2, and HD. In some cases equilibrium amounts of the effluent gases were observed. Activation of the silicas appeared to be related to the dehydration of the silica surfaces. After activation, the surface of one of the silicas, Cabosil M5, was found to catalyze the hydrogenation of ethylene to ethane and to catalyze extensive exchange when deuterium was used as the hydrogenation reagent.