Fig. 4

PTR-MS spectrum for experiment 3 (119 h) where background VOCs, reactor off-gas air sampled through the catalyst, have been subtracted from the reactor off-gas spectrum. The figure uses a logarithmic scale of intensity to aid in illustrating both major ions and ions of interest. Ions used for quantification of ethanol (47, 65, 93), methanol (33, 51), acetaldehyde (45) and terpenes and terpenoids (81, 137) are marked accordingly