Synthesis and characterization of polymeric activated carbon-supported vanadium and magnesium catalysts for ethylbenzene dehydrogenation

The preparation and characterization of activated carbon obtained from the sulfonated styrene-divinylbenzene copolymer and the effect of vanadium and magnesium on its catalytic activity and selectivity to styrene were described. These new catalysts were evaluated in ethylbenzene dehydrogenation without steam to produce styrene, an important intermediate for petrochemical industries. It was found that the activated carbon is active and selective to styrene, a fact which was related to the presence of quinone groups on the surface. The addition of vanadium increased the activity even more and this was assigned to the activity of vanadium in dehydrogenation reactions as well as to an increase of the amount of oxygen groups on the surface. However, no significant effect of vanadium on the selectivity to styrene was found. Magnesium increased the quinone groups on surface leading to an increase of the initial activity of activated carbon-supported vanadium depending on its amount, but the catalysts deactivated during reaction, a fact which was related to coke deposition; at the end of reaction no effect of magnesium on the activity and selectivity was found. The catalysts were more active than a commercial hematite-based one, evaluated in the presence and in the absence of steam. The catalyst with 5% of vanadium was the most promising sample, showing the highest ethylbenzene conversion which was three times the value obtained with the commercial catalyst in the presence of steam. This result is especially advantageous for the economy of the process, since the addition of superheated steam can be avoided during reaction, saving energy for the process. (C) 2008 Elsevier B.V. All rights reserved.