EFFECT OF ETHANOL ADDITION ON PHYSICOCHEMICAL PROPERTIES AND STABILITY OF BIO-OIL DURING STORAGE

Ethanol at different mass concentrations (0, 4, 8, 12, 16, and 20 wt %) was added into crude bio-oil from rice husk pyrolysis with fluidized bed reactor to upgrade oil properties. The effect of ethanol addition on physicochemical properties of bio-oil during 90 d storage was investigated. Multivariate Test of bio-oils with ethanol addition showed that the effect of additive concentration and storage time had statistical meaning. For pH, water content and density of bio-oil, different mass concentration of ethanol had significant difference. Specifically, with the increase of ethanol mass concentration, pH increased while water content and density decreased. For viscosity of biooil, different mass concentration of ethanol had no significant difference on viscosity of bio-oil, but for all the bio-oil groups, there were significant difference between experimental groups with ethanol addition and control group without ethanol addition. Ethanol has significant effect on reducing oil viscosity, and 4wt% is an appropriate concentration for addition. In addition, the pH, water content, viscosity, and density of bio-oil with 4wt% ethanol addition were changed from 3.15, 35.27wt%, 6.81 mm(2)/s and 1.1400 g/cm(3) to 3.46, 35.24wt%, 9.77 mm(2)/s and 1.1489 g/cm(3) after 90 d storage, respectively. FT-IR results indicated that all bio-oil samples have similar functional groups. In other words, if the spectrum of each bio-oil sample are compared, there is no significant difference in the integral shape of the spectrum. Wavenumbers of substantial functional groups in bio-oil were between 3420 and 3398 cm(-1) as well as between 1713 and 1716 cm(-1), which indicated the existence of C=O bonds, C=C bonds, C-O bonds, C-H bonds, and O-H bonds, etc. in bio-oil. These functional groups demonstrated that there were alcohols, phenols, aromatics, and acids, etc. in bio-oil. GC-MS results indicated that, chemical composition of bio-oil was obviously changed by long term storage. Results of GC-MS analysis of bio-oil with 8wt% mass concentration of ethanol before and after storage showed that bio-oil consisted of elements such as carbon, hydrogen, oxygen and nitrogen, and the components were mainly ketones, phenols, organic acids and alcohols, etc.. On one hand, compared with the control group without ethanol, the experimental group bio-oil with ethanol addition consisted of much more larger components, which were generated due to polymerization reactions. On the other hand, the results indicated that, for the bio-oil with ethanol after 90 d storage, 51 kinds of chemical compounds were disappeared and 9 kinds of chemical compounds were generated. Through further analysis, it can be concluded that most of components participating in the chemical reactions were from phenols and ketones. During storage period, aging reactions inside bio-oil could be affected by ethanol addition. Microscopic analysis demonstrated that ethanol addition had a beneficial effect on the quality of the dispersion. Also, additive was miscible with the components of the bio-oil samples. The research can provide scientific reference for the application of bio-oil.