Iron oxide dehydrogenation catalysts supported on magnesium oxide. Part 3.—But-1-ene dehydrogenation activity

Abstract

The catalytic behaviour of iron oxide catalysts supported on magnesium oxide in the non-oxidative dehydrogenation of but-1-ene to buta-1,3-diene has been studied. Under dehydrogenation conditions the magnesium ferrite phase of the fresh catalyst was found to be reduced to FeO in the bulk of the ferrite particles, where FeO is strongly stabilized by the formation of a solid solution with MgO. At the surface of the particles magnesium ferrite is reduced to Fe₃O₄. In the reduced state a catalyst containing ca. 3 wt.% Fe shows a but-1-ene conversion of 26% combined with a buta-1,3-diene selectivity of 65% at 873 K. The activation energy for dehydrogenation was found to be 47 kcal mol^–1.

The (unpromoted) catalyst gradually deactivates owing to carbon deposition. Under dehydrogenation conditions the catalyst surface is completely covered by a layer of amorphous carbon within 20 h.