Effects of N-tert-butyl-α-phenylnitrone on the product distribution of cellulose liquefaction in supercritical ethanol

With N-tert-butyl-α-phenylnitrone (PBN) as free radicals trapper, the effects of PBN dosage and reaction temperature on the product distribution and bio-oil component distribution of cellulose liquefaction in supercritical ethanol were investigated using an autoclave. The results showed that the yields of bio-oil and volatile compounds were 37.17% and 50.08% without PBN, respectively; meanwhile the highest yield of bio-oil increased to 48.35%, whereas the volatile compound yield decreased to 35.65% with the PBN dosage increased from 0 to 0.4 g. With the increase of reaction temperature from 250℃ to 340℃, the cellulose conversion rate increased sharply from 23.10% to 88.92% while the bio-oil yield increased from 19.18% to 48.35% (320℃) and the volatile compound yield increased from 6.03% to 50.28% quickly. The GC-MS results showed that the dominant compounds in bio-oil were esters, ketones, alkanes, alcohols, acids and benzenes with the highest relative contents of 27.91%, 15.77%, 13.44%, 12.42%, 16.07% and 19.81%, respectively. The present results proved that PBN has obvious effects on the product distribution and bio-oil component distribution of cellulose liquefaction in supercritical ethanol, especially PBN can enhance the transformation between bio-oil and volatile compounds via reacting with benzyl radicals, methyl radicals, ethyl radicals, etc. The transformation among dominant compounds in bio-oil can be regulated by varying PBN dosage and reaction temperature.