蒸馏温度对核桃壳生物油馏分组分分布的影响

Influence of heating temperatures on the component distribution of distillates derived from walnut shell bio-oil

通过改变蒸馏温度对生物油进行常压蒸馏并将馏分分为油水两相,研究了馏分的组分分布变化。结果表明,在120-300℃随着蒸馏温度的升高,生物油馏出率不断增加;蒸馏温度低于240℃的油相馏分中萘、甲苯等芳烃类化合物和乙酸等羧酸类化合物明显富集,以120℃油相馏分为例,芳烃类和羧酸类化合物的相对含量是生物油原油的13.86倍和3.15倍;当蒸馏温度高于240℃时苯酚、愈创木酚等酚类化合物大量馏出,使得油相馏分的产率明显增加;同时,所获水相馏分中的水分含量皆高于60%,水分的富集效果明显;在馏分中检测到了2-乙基乙酸丁酯和环戊酮等原油中未检测到的组分并且馏分中水分总量高于生物油原油,这些都表明生物油在蒸馏过程中发生了酯化、缩聚等化学反应。通过对油相馏分的组分分布进行分析,发现改变蒸馏温度可以有效富集生物油中的高价值化合物,如苯酚、愈创木酚、4-甲基愈创木酚、4-乙基愈创木酚和4-丙基愈创木酚的相对含量在300℃的油相馏分中分别比生物油提高了109%、160%、84%、53%和444%。

Influence of heating temperatures on the component distribution of distillates distilled from walnut shell bio-oils was studied.Meanwhile,distillates were further separated into water-soluble and water-insoluble fraction to characterize product distribution.The results showed that distillate fraction yield increased with strengthening heating temperature from 120 to 300℃.Aromatic hydrocarbons(e.g.naphthalene)and carboxylic acids(e.g.acetic acid)significantly concentrated in water-insoluble fraction as heating temperatures were below240℃.Notably,the relative concentration of aromatic and carboxylic compounds in the water-insoluble fraction derived from 300℃was 13.86 and 3.15 times higher than that of crude bio-oil,respectively.Large amounts of phenols such as phenol and guaiacol was distilled as heating temperatures exceeded 240℃,which induced enhanced yield of water-insoluble fraction.Moreover,the moisture of all the water-soluble fractions was higher than 60%,which demonstrated the water-soluble fraction remarkably concentrated moisture.In addition,undetected components(e.g.butyl 2-ethylacetate and cyclopentanone)in crude bio-oil surprisingly existed in distillates and the total moisture of distillates was higher than that of crude bio-oils,which proved esterification and polycondensation reactions occurred in bio-oil distillation process.Furthermore,the component distribution of distillates also indicated modifying heating temperatures effectively enriched commodity chemicals.Note that water-insoluble fraction distilled from 300℃exhibited relative concentration of phenol,guaiacol,4-methyl-2-methoxyphenol,4-ethyl-2-methoxyphenol and 4-propyl-2-methoxyphenol was 109%,160%,84%,53%and444%higher than that in crude bio-oil,respectively.