F. Lepeltier et al., IN-SITU FT-IR AND KINETIC-STUDY OF METHANOL SYNTHESIS FROM CO2 H-2 OVER ZNAL2O4 AND CU-ZNAL2O4 CATALYSTS/, Journal of molecular catalysis. A, Chemical, 132(1), 1998, pp. 91-100
The kinetics of the CO2/H-2 reaction over ZnAl2O4 and Cu-ZnAl2O4 catal
ysts at 250 degrees C up to 0.3 MPa have been followed by in situ FT-I
R spectroscopy, Both methanol and carbon monoxide formation were enhan
ced in presence of copper. They were also produced by independent rout
es through different adsorbed species. Formate (type I, I' and II), me
thoxy and carbonate species were identified on the support and, in add
ition, copper formate and copper carbonyl species when copper was pres
ent, The hydrogenation of carbonate species to copper formate species
was found rate determining in methanol synthesis over the Cu-ZnAl2O4 c
atalyst whereas type I formate species were shown to be the active int
ermediate for this reaction over the ZnAl2O4 support. Carbon monoxide
resulted from the water gas shift reaction probably through the same s
pecies as methanol formed over the Cu-ZnAl2O4 catalyst whereas it seem
ed to stem from formate species of type II in the case of the ZnAl2O4
support. Type II formate species were shown inactive in presence of co
pper whereas the methoxy species adsorbed on the support were found in
active in presence and in absence of copper. The comparison of these r
esults with those previously obtained with the CO/H-2, mixture showed
that the nature and the role of the detected species strongly depended
on the reactive atmosphere and on the presence or not of copper in th
e catalyst composition. (C) 1998 Elsevier Science B,V. All rights rese
rved.