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

摘要

Ethanol at different mass concentrations (0, 4, 8, 12, 16, and 20 wt %) was added into crude bio-oil fromrice husk pyrolysis with fluidized bed reactor to upgrade oil properties. The effect of ethanol addition onphysicochemical properties of bio-oil during 90 d storage was investigated. Multivariate Test of bio-oils with ethanoladdition showed that the effect of additive concentration and storage time had statistical meaning. For pH, watercontent and density of bio-oil, different mass concentration of ethanol had significant difference. Specifically, with theincrease 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-oilgroups, there were significant difference between experimental groups with ethanol addition and control group withoutethanol addition. Ethanol has significant effect on reducing oil viscosity, and 4wt% is an appropriate concentration foraddition. In addition, the pH, water content, viscosity, and density of bio-oil with 4wt% ethanol addition were changedfrom 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 dstorage ,respectively. FT-IR results indicated that all bio-oil samples have similar functional groups. In other words, ifthe spectrum of each bio-oil sample are compared, there is no significant difference in the integral shape of thespectrum. Wavenumbers of substantial functional groups in bio-oil were between 3420 and 3398 cm~(-1) as well asbetween 1713 and 1716cm~(-1), which indicated the existence of C=O bonds, C=C bonds, C–O bonds, C–H bonds, andO–H bonds, etc. in bio-oil. These functional groups demonstrated that there were alcohols, phenols, aromatics, andacids, etc. in bio-oil. GC-MS results indicated that, chemical composition of bio-oil was obviously changed by longterm storage. Results of GC-MS analysis of bio-oil with 8wt% mass concentration of ethanol before and after storageshowed that bio-oil consisted of elements such as carbon, hydrogen, oxygen and nitrogen, and the components weremainly ketones, phenols, organic acids and alcohols, etc.. On one hand, compared with the control group withoutethanol, the experimental group bio-oil with ethanol addition consisted of much more larger components, which weregenerated due to polymerization reactions. On the other hand, the results indicated that, for the bio-oil with ethanolafter 90 d storage, 51 kinds of chemical compounds were disappeared and 9 kinds of chemical compounds weregenerated. Through further analysis, it can be concluded that most of components participating in the chemical reactionswere from phenols and ketones. During storage period, aging reactions inside bio-oil could be affected by ethanoladdition. Microscopic analysis demonstrated that ethanol addition had a beneficial effect on the quality of thedispersion. Also, additive was miscible with the components of the bio-oil samples. The research can provide scientificreference for the application of bio-oil.