Aldehyde, ketone and carbonyl concentration in hardwood pyrolysis oil with aging time, the higher aldehyde concentrations belong to NMR measurements at 400 MHz and lower to measurements at 44 MHz.

t/h	c (aldehydes)/mmol g−1	c (ketones)/mmol g−1	c (ketones)/c (aldehydes)	c (carbonyls)/mmol g−1
0	0.31–0.40	4.36–4.45	11–14	4.76
4	0.24–0.31	3.89–3.98	13–17	4.21
24	0.19–0.26	4.00–4.07	15–21	4.26