R. Dziembaj et al., On the deactivation of Fe, K/active carbon catalysts in the course of oxidative dehydrogenation of ethylbenzene with carbon dioxide, TOP CATAL, 11(1-4), 2000, pp. 317-326
Highly active and selective Fe2O3-K2O/C-act catalysts for oxidative dehydro
genation of ethylbenzene with CO2 undergo deactivation. The course of deact
ivation up to a loss of 95% activity is described, and related to the forma
tion of an inactive carbonaceous deposit. The catalysts and deposits were c
haracterized after various times-on-stream (TOS) by textural, structural an
d chemical analysis, as well as by temperature-programmed decomposition and
oxidation. XPS spectra of O 1s and K 2p confirmed the removal of OH and di
minishing of carbonyl groups, as well as segregation of K2CO3 onto the surf
ace. Prolonged TOS, at temperatures above 500 degrees C caused removal of h
eteroatoms from the carbonaceous deposits and even the appearance of graphi
tized structure in XRD patterns. It was found that the activity depended al
most linearly on the amount of and the decrease in surface area. An excess
of CO in relation to styrene in the product distribution suggests that the
deposit is formed owing to styrene polymerization, and further dehydrogenat
ion, on the catalyst surface.