Methanol dehydrogenation to formaldehyde was operated in a continuous fixed-bed reactor with external recycling in the presence of sodium carbonate catalyst supported on active carbon. Due to the importance of gas phase decompns. of methanol and mainly formaldehyde, selectivity of formaldehyde in such a reactor is small compared to that obtained in a fixed-bed reactor. Furthermore, the contribution of gas phase reactions to formaldehyde synthesis through global dehydrogenation of methanol complicates steady-state kinetic studies. However, transient and methanol isotope (CD3OD and CH3OD) transient expts. showed that a hydrogen species and also a methoxy and/or a hydroxymethyl intermediate(s) are strongly adsorbed on the catalyst surface. Based on these facts, a mechanism of methanol dehydrogenation on sodium carbonate catalyst supported on active carbon is proposed. [on SciFinder (R)]