A wide variety of solid bases, including alkali-exchanged zeolites X,
Y, L and beta, and alkali-impregnated carbon and magnesia, were tested
as catalysts for the side-chain alkylation of toluene with methanol t
o form styrene and ethylbenzene. In addition, the effects of adding Gr
oup ILIA elements (B, Al, Ga, In) to the catalysts were examined. At 6
80 K and atmospheric pressure, the major reaction products were styren
e, ethylbenzene, and carbon monoxide. Cesium-exchanged zeolite X was t
he most effective alkali-containing catalyst for the alkylation reacti
on. Of the Group IIIA additives that were tested, only boron promoted
the alkylation reaction. The primary effect of adding boron was to red
uce the decomposition of methanol to carbon monoxide. Apparently, boro
n selectively modifies the sites associated with methanol decompositio
n without inhibiting the sites active for alkylation. A berated Cs-car
bon sample also catalyzed the alkylation reaction, demonstrating that
a zeolite framework is not necessary to form the active site. Micropor
osity seems to play an important role in these catalysts since both th
e alkali-modified carbons and the zeolites are microporous.