Chromium-doped magnetite is the traditional catalyst used in the high
temperature shift reaction in industrial processes. This work reports
a method for preparing this solid, by heating chromium-doped iron(III)
hydroxoacetates (IHA), prepared both by coprecipitation and by impregn
ation. This method provides the production of the catalyst in its acti
ve form avoiding the step of activation in industrial processes. It wa
s noted that the presence of chromium affects magnetite formation as w
ell as its characteristics. IHA containing chromium produces magnetite
at higher temperature than does the pure IHA. Chromium-doped magnetit
es have higher surface areas, are less crystalline, have lower Fe(II)/
Fe(III) ratios and are catalysts more active than those obtained from
plain IHA. These effects depend on the preparation method of the precu
rsor. It was also found that the impregnated sample is made of aggrega
tes of a few crystals whereas the coprecipitate is made of smaller pol
ycrystalline particles. In addition, the coprecipitation method leads
to a more even distribution of chromium in solids. These observations
are consistent with the best performance shown by the catalyst prepare
d by coprecipitation.