La. Boot et al., IRON-BASED DEHYDROGENATION CATALYSTS SUPPORTED ON ZIRCONIA .2. THE BEHAVIOR IN THE DEHYDROGENATION OF 1-BUTENE, Journal of catalysis, 163(1), 1996, pp. 195-203
The behavior of iron oxide-based catalysts supported on zirconia in th
e dehydrogenation of 1-butene was investigated, Iron oxide-on-zirconia
catalysts deactivate during operation due to carbon deposition, It wa
s shown with XRD that solid state reactions between the active phase a
nd the support do not take place in the zirconia-supported catalysts:
the iron-containing phase after reaction is Fe3O4. The total amount of
carbon deposited onto zirconia-supported catalysts containing only ir
on oxide as determined with temperature-programmed oxidation is about
2 wt% C after 20 h. It was also shown that a carbon species deposited
in narrow pores was present in iron oxide-on-zirconia catalysts, The K
Fe/ZrO2 catalysts proved to be more stable than KFe/MgO catalysts: for
catalysts containing highly dispersed iron oxide only a slight deacti
vation was observed after about 100 h on stream, This deactivation is
attributed to migration of potassium from the catalyst to the quartz r
eactor, Catalysts of low loadings (1 wt% Fe, 1 wt% K) or with less wel
l-dispersed iron oxide deactivate in a shorter period of time: an inco
mplete coverage of the zirconia support leads to deactivation by carbo
n deposition. The selectivity to butadiene of the KFe/ZrO2 catalysts i
s about 60%, which is related to a high production of CO2. This is att
ributed to carbon deposition taking place in the small pores of the zi
rconia-supported catalysts, The coke is subsequently gasified, probabl
y by the supported potassium carbonate. Eliminating the small pores su
bstantially improved the butadiene selectivity. (C) 1996 Academic Pres
s, Inc.