Fig. 6 presents the reusability of 0.5 wt% Cu-modified -zeolite for bio-oil upgrading. The complete chemical identification of light oil in the upgraded bio-oil and the corresponding GC–MS spectra can be found in Table S2 and Fig. S4 of Supplementary data.One can see that the catalyst has good stability with less than 5%selectivity degradation when reused until three times. It should be noted that phenols, ether, and compounds with carboxyl functional group begin to appear in the light oil of upgraded bio-oil for the reused catalyst, which results in the increase of the oil yield.Fig. 7 depicts the mass balance of pyrolysis products as 0.5 wt% Cu-modified -zeolite is reused without regeneration. By comparing Figs. 6 and 7, it can be seen that the appearance of carboxyl functional group is accompanied by the decrease of CO2 yield, indicating the activity decrease for the decarboxylation reaction. However, it should be noted that the activity for the decarboxylation reaction can be maintained to some extent even though the reduction gas products (CO and H2) decrease slightly. Herein, the slight decrease of CO and H2O yields might be attributed to the accumulation of coke which slightly degrades the deoxygenation activity. This result indicates that there is an optimum Cu loading amount for achieving the maximum catalytic performance with good reusability.