Partial oxidation of methanol over Fe2O3-supported (SiO2 or MoO3) aerogels
was investigated between 225 to 300 degreesC. Wide product selectivity was
observed dependent on percentage of iron oxide present, support used, and t
emperature. The reaction evaluations were done using 1:1.6 methanol to oxyg
en mole ratio in supercritical carbon dioxide (pressure of 90 bar). Dimethy
l ether was favored for higher iron oxide loadings (20 and 100%) and lower
temperatures (225 to 250 degreesC). This is related to the Lewis acidity of
the iron oxide surface sites. Formaldehyde was favored if the support was
changed to molybdenum oxide (20% iron oxide). This is related to the format
ion of iron molybdate as an active site. Methyl formate was favored for the
low percentage iron oxide on silica (250-275 degreesC). This is related to
the formation of surface formates that probably react with fluid phase met
hanol. FT-IR probe molecule characterization studies revealed that methanol
adsorbs as methoxy as the first step in all reaction processes. The work p
rovides further insight into the mechanistic nature of the partial oxidatio
n of methanol over iron oxide based materials. (C) 2001 Academic Press.