Dehydration mechanisms in the thermal decomposition of gaseous formic acid

Abstract

The homogeneous thermal decomposition of formic acid has been studied in flow and static systems between 457 and 780°C. Dehydration is of the second order below 600°C, k= 10^8·44 exp(–132,500/RT) l mol^–1 s^–1, but the Arrhenius plot then becomes curved, straightening out again above 670°C to give k= 10^12·39 exp(–253,000/RT) s^–1. The order in this region is 1·5 and dehydration here appears to be a unimolecular reaction in the fall-off region. Decarboxylation is of the first order throughout the temperature range, with k= 10^9·47 exp(–203,000/RT) s^–1.