Fig. 2. Concentration of the eucalyptol and its degradation products versus residence time. ‘‘Original’’ in the x-axis means the mixture of bio-oil with methanol at room
temperature. ‘‘Mix’’ means the mixture of bio-oil, methanol, and Amberlyst 70 at room temperature. ‘‘0 min’’ means that the temperature just reached the required reaction
temperatures. Experimental conditions: T = 170 C; catalyst loading: 15 wt.%; methanol/bio-oil mass ratio: 1.4.