THE EFFECT OF THE REACTOR TYPE ON THE SELECTIVITY OF THERMAL-REACTIONS OF P-XYLENE IN TEMPERATURE-GRADIENT SYSTEMS

Thermal reactions of p-xylene were investigated in two kinds of reactors, batch type and flow type, with a large temperature gradient. Excellent differences of the resulting products were observed between these two types of reactors. As for a batch type reactor, 4,4'-dimethylbibenzyl was produced in a high yield with [2.2]paracyclophane and toluene as by-products, and as for as a flow type reactor, toluene was obtained as a major product with a low selectivity of 4,4'-dimethylbibenzyl, respectively. These results were different from those of the conventional fast flow pyrolysis method in which [2.2]paracyclophane or poly(3,6-dimethylene-1,4-cyclohexadiene) was formed as a major product. These differences can be accounted for by the partial separation of a reaction mixture caused by the thermal diffusion effect, which arises when the mixture is subject to a temperature gradient.