Surface and catalytic characteristics of thermally and chemically activated bentonite catalysts used in the polymerization of styrene

The most active bentonite samples in the polymerization of styrene were found to be one thermally treated for 2 hr at 550 °C and one chemically treated with 35% (ww) H2SO4. Surface studies of various bentonite samples showed that the characteristic pore system and Lewis acid sites resulting from the removal of the adsorbed water were responsible for the catalytic activity of the thermally treated bentonite. Overheating could destroy both the catalyst activity and the exposed surface. Upon activating bentonite with H2SO4, it was found that both the produced pore system and the creation of new Brønsted acid sites could be responsible for the catalytic activity. The different factors affecting the polymerization reaction over the most active samples and the dependence of the structure of the produced polymer on the pretreatment of the bentonite were also investigated.