Zhou Dan, Wang Linlin, Chen Xiaopeng, Wei Xiaojie, Liang Jiezhen, Zhang Dong, Ding Guoxin
School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, People's Republic of China.
Guangxi Key Laboratory of Petrochemical Resources Processing and Process Intensification Technology, Guangxi University, Nanning 53004, People's Republic of China.
R Soc Open Sci. 2018 Jul 4;5(7):171031. doi: 10.1098/rsos.171031. eCollection 2018 Jul.
Rosin esters are widely applied as masticatory substances and beverage stabilizers, while classical acid-catalysed processes will lead to metal residue or environmental issues. Super/subcritical CO-enriched high temperature liquid water (HTLW) as a green acid catalyst in the esterification reaction of rosin with glycerol was investigated. The pH of CO-HO binary system, as calculated based on gas-liquid equilibrium, charge balance and chemical equilibrium equations, ranged from 3.49 to 3.70 depending on the reaction conditions, indicating effective acid catalysis. Response surface methodology experiments showed the optimum conditions were 3.5 h, 3.9 MPa CO pressure, a rosin-to-glycerol molar ratio of 1.32 and 269°C, and an enhanced esterification yield of 94.74% was achieved, which was superior to that obtained using a ZnO catalyst. It was found that the esterification kinetics was a pseudo first-order reaction, and the enthalpy and entropy of activation were calculated using the Arrhenius-Polanyi equation. The presence of super/subcritical CO-enriched HTLW catalyst can decrease the activation energy and significantly accelerate the reaction rate.
松香酯被广泛用作咀嚼物质和饮料稳定剂，而传统的酸催化工艺会导致金属残留或环境问题。研究了超临界/亚临界富含CO的高温液态水（HTLW）作为松香与甘油酯化反应中的绿色酸催化剂。基于气液平衡、电荷平衡和化学平衡方程计算得出，CO-H₂O二元体系的pH值在3.49至3.70之间，具体取决于反应条件，表明具有有效的酸催化作用。响应面法实验表明，最佳条件为反应时间3.5小时、CO压力3.9MPa、松香与甘油的摩尔比为1.32以及温度269°C，酯化产率提高到94.74%，优于使用ZnO催化剂时获得的产率。研究发现酯化动力学为拟一级反应，并使用Arrhenius-Polanyi方程计算了活化焓和活化熵。超临界/亚临界富含CO的HTLW催化剂的存在可以降低活化能并显著加快反应速率。
