摘要
将超临界CO2萃取与酯化反应耦合,研究了萃取酯化提质生物油过程。乙酸(AC)、丙酸(PA)和丙烯酸(AR)在超临界CO2(scCO2)条件下酯化时的平衡转化率显著高于常压酯化时的平衡转化率,表明scCO2对酯化反应具有明显的促进作用。这主要是由于生成的酯不断被萃入scCO2相。在恒温下scCO2的密度随压力升高而增大,因而酯化率随着CO2压力的升高而增加,与有机酸单独酯化时相比,混酸(AC、PA和AR)酯化后各种酸的转化率却比较接近,表明酯化过程中存在着酯交换机制。真实生物油的酯化结果表明,在80℃和28.0MPa下酯化3.0h,总酸的转化率可达86.78%。酯化后生物油的pH值从3.78提高到5.11,萃出生物油在140℃下挥发率接近100%,表明油品质量得到显著提升。
Esterification of acetic acid（AC）,propanoic acid（PA） and a mixed acid（AC ＋ PA ＋ acrylic acid） as well as real bio-oil with ethanol under supercritical CO2（scCO2） conditions were investigated.It was found that these carboxylic acids could afford much higher conversions under scCO2 condition in comparison with esterification at atmosphere pressure,revealing the promoting effect of scCO2 as a result of that the formed esters are prone to be phase-transferred into the scCO2 phase.Since raising pressure at constant temperature can enhance the dissolving power of scCO2,it was observed that esterification conversion increased with pressure.The results esterifying these acids separately showed significant difference in their conversions,whereas simultaneous esterification of the mixed acid mixture afforded very close conversions,suggesting that a transesterification mechanism might occur in the case of simultaneous esterification under scCO2.The appropriate operation conditions for upgrading bio-oil by scCO2 extractive esterification were determined as at 80℃ and 28.0MPa for 3.0h.Under this condition,the total acid conversion could reach up to 86.78%.pH value for the upgraded bio-oil increased from 3.78 to 5.11.The total volatile components in the upgraded bio-oil approached up to 100% at 140℃.
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2010年第6期673-678,共6页
Journal of Fuel Chemistry and Technology
基金
国家高技术研究发展计划(863计划
2009AA05Z401)
山东省自然科学基金(ZR2009BL023)
关键词
生物油
超临界
萃取
酯化
提质
bio-oil
supercritical
extraction
esterification
upgrading
