Abstract
This study deals with the effect of CO2/carbon molar ratio (CO2/C) on syngas production in the dry reforming (DR) of real bio-oil with a NiAl2O4 spinel derived catalyst, which has high activity and H2 selectivity in the raw bio-oil reforming. The reaction tests were carried out at 700 ºC, steam/carbon (S/C) molar ratio of 0.4 (corresponding to the water contained in the bio-oil feed), space time of 0.25 gcatalysth/goxygenates, and CO2/C ratio of 0, 0.5 and 1. The results evidence a higher syngas yield in the DR reaction tests (88%, not dependent on CO2/C ratio) compared to the conventional steam reforming (SR, 76%) because of the increase in CO yield, which leads to a decrease in H2/CO ratio (from 1.8 in SR to 1.2 and 1 for CO2/C ratio of 0.5 and 1, respectively). For both CO2/C ratios positive CO2 conversions (22-24 %) and a reduction of CO2 emissions over SR are obtained. The characterization of spent catalysts by several techniques proves that the main cause of deactivation is coke deposition, that is mainly composed of structured carbon (filamentous carbon), with a small fraction of amorphous coke. The DR reaction tests lead to a noticeable higher deposition of filamentous carbon, which does not lead to a noticeable difference in the catalyst stability compared to SR, in spite of the significant higher amount of coke deposited (34 and 46 wt% for CO2/C ratios of 0.5 and 1, respectively) than in the SR (18 wt%).
