N-叔丁基-α-苯基硝酮对纤维素超临界乙醇液化产物分布的影响

以N-叔丁基-α-苯基硝酮(PBN)为自由基结合剂,采用间歇式高温高压反应釜对玉米秸秆纤维素进行超临界乙醇液化,考察PBN用量(浓度)和反应温度(活性)对纤维素液化产物及生物油中主要化合物分布的影响。结果表明,在320℃,仅有超临界乙醇作用,生物油收率为37.17%,挥发分收率高达50.08%;随着PBN用量增加到0.4 g,生物油收率最高提升至48.35%,挥发分最低下降到35.65%。在超临界乙醇和PBN作用下,随着反应温度从250℃升高至340℃,纤维素转化率从23.10%急剧增加至88.92%,生物油收率从19.18%上升到最高48.35%(320℃)后略有下降,挥发分也从6.03%急剧上升至50.28%。GC-M S结果显示,酯类、酮类、烃类、醇类、酸类及苯类化合物是生物油的主要成分,各组分的最高相对含量分别为27.91%、15.77%、13.44%、12.42%、16.07%、19.81%。实验结果证实了PBN对纤维素超临界乙醇液化产物及生物油组分分布产生了较明显的影响,尤其能通过与含苯基、乙基等活性碎片结合促进挥发分与生物油之间的转化,且PBN用量及液化温度的改变可以促使生物油中主要化合物发生不同程度的相互转化。

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.