REACTIVE SILICA .I. FORMATION OF A REACTIVE SILICA BY THERMAL COLLAPSE OF METHOXY GROUPS OF METHYLATED AEROSIL

The degassing of methylated Aerosil silica was studied by infrared spectroscopic techniques. The surface methoxy groups were quite stable and were removed only very slowly at temperatures up to 600°. At higher temperatures, however, the removal of methoxy groups became very rapid. The methoxy groups cracked, and the silica surface was drastically modified. Surface silanol and silane groups were formed. Also, the spectra indicate that hydrocarbonic surface species were formed which were acetylenic in nature and which showed extreme stability to degassing. Silane and other groups were only slowly removed at 830°; their removal resulted in the formation of a silica surface exhibiting unusually high reactivity. A possible mechanism is discussed.