In situ C-13 NMR was used to monitor the catalytic behavior of supercritically 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 expanded montmorillonites have similar catalytic activity. Saponites give a wider variety of hydrocarbons and are more active than montmorillonites, in turn, AD saponite is more active than SCD saponite. With clay catalysts, acidic strength is less important than the size and distribution of the pores, so that different drying conditions lead to very different catalytic results. Because of the lower acidic strength and acid 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 ZSM-5.