Thermal reactions of acetic acid: 13C/12C partitioning between CO2 and CH4

Analysis of the gaseous products from the thermal decomposition of acetic acid in the temperature range of 290 to 650°C shows CO2 contents to decrease from 94 to 2% and CH4 and CO contents to increase from 4 to 87% and 1 to 11% respectively. Ethane contents maximise at 1.6% at 500°C. Δ13C(CO2 CH4)‰ values at all reaction temperatures closely approximate those theoretically predicted at isotopic equilibrium and, by extrapolation, those commonly observed in natural gases of biogenic origin. The bulk isotopic composition of these product gases at all reaction temperatures reflects that of the acetic acid starting material, thus supporting the concept of isotope partitioning in a transition stage.