Mn-substituted Fe-K mixed oxide catalysts for dehydrogenation of ethylbenzene towards styrene

K-promoted iron oxide (Fe-K) and partially Mn-substituted Fe-K catalysts pr epared by the soi-gel method showed improvement of catalytic activity in th e dehydrogenation of ethylbenzene to styrene. Manganese, compared to the ot her transition metals (Co, Ni, Cu and Zn), was found to be an effective add itive element for enhancement of the catalytic activity as well as suppress ing of coke deposition. The Mn-substituted Fe-K catalysts with the atomic c ontent of Mn in Mn-Fe mixed oxides: Mn/(Mn + Fe) (between 0 and 100%) were characterized using X-ray diffraction. The largest rate formation of styren e was observed for catalyst with 20% of manganese. On the other hand, no ch ange in activation energy was observed. The lattice strain of the spinel ph ase between gamma -Fe2O3 and MnFe2O4 exhibited the maximum with 20% content of Mn. The experimental data suggest that enhancement of catalytic activit y by addition of the Mn is responsible for increasing of the number of acti ve sites in the spinel phase of the catalyst. (C) 2001 Elsevier Science B.V . All rights reserved.