Potassium promotion of iron oxide dehydrogenation catalysts supported on magnesium oxide: 1. Preparation and characterization

Abstract

Catalysts of iron oxide supported on magnesium oxide and promoted with potassium were prepared by incipient wetness impregnation of preshaped magnesium oxide support pellets with a solution of an iron complex, either ammonium iron(III) citrate or ammonium iron(III) EDTA and potassium carbonate. Iron and potassium were applied either simultaneously or consecutively. As determined using X-ray diffraction, thermogravimetric analysis, and magnetic measurements, calcination above 923 K results in the formation of a mixed oxide of iron and potassium, viz., KFeO 2 After calcination at 973 K the average crystallite size of the KFeO 2 phase is about 300 Å. The formation of KFeO 2 appeared to have a strong retarding effect on the reduction of the iron oxide phase to metallic iron. It was found that the KFeO 2 phase is unstable in atmospheric air due to reaction with carbon dioxide and moisture to form potassium (hydrogen)carbonate and (hydrated) iron oxide.