Hy. He et al., IN-SITU C-13 SOLID-STATE NMR-STUDIES OF THE CATALYTIC CONVERSION OF METHANOL ON EXPANDED MONTMORILLONITES AND SAPONITES, Journal of physical chemistry, 99(18), 1995, pp. 6980-6985
In situ C-13 NMR was used to monitor the catalytic behavior of supercr
itically dried (SCD) and air dried (AD) expanded montmorillonites and
saponites in the conversion of methanol. The motion of MeOH molecules
in expanded montmorillonites is highly restricted. No carbon monoxide
is produced below 350 degrees C on either catalyst. Various aliphatic
and aromatic hydrocarbons are found after heating at 350 degrees C of
which n-pentane, n-hexane, and n-heptane are dominant. AD and SCD expa
nded montmorillonites have similar catalytic activity. Saponites give
a wider variety of hydrocarbons and are more active than montmorilloni
tes, in turn, AD saponite is more active than SCD saponite. With clay
catalysts, acidic strength is less important than the size and distrib
ution of the pores, so that different drying conditions lead to very d
ifferent catalytic results. Because of the lower acidic strength and a
cid site density of montmorillonites and saponites in comparison with
zeolites, the temperature at which a given hydrocarbon appears in the
conversion of methanol is higher for clay catalysts than for zeolite Z
SM-5.