Abstract:Bio-oil which derivates from fast pyrolysis of biomass is a promising product for replacing the traditional fossil oil. Bio-oil with high oxygen, high viscosity, strong acid, low heat value and poor thermal stability is not beneficial to the industry application. Therefore, it is necessary to improve the quality of bio-oil. The technology of ultrasonic emulsification and additives was used to improve the stability and decrease the oxygen content. The influence of ultrasonic power, ultrasonic time, the kinds of alcohol and the ratio of alcohol on the improvement of bio-oil quality was investigated. The result showed that the stability and heat value can be effectively improved when adding alcohol or using ultrasonic emulsification appropriately. With the increase of ultrasonic time or the ultrasonic power, the viscosity was increased first and then increased after a decreasing. When the content of alcohol was not enough, the addition of emulsification auxiliaries could improve the stability of the emulsification liquid effectively. Heavy oil combined with alcohol showed a better stability, and the TG curve was significantly shifted to lower temperature zone. The results of TG curve of emulsified heavy oil and alcohol showed that methanol and ethanol were more conducive to the heavy oil in polymer or oligomer ester alcoholysis. When the ratio of additional methanol to bio-oil was 3∶1, the viscosity was decreased from 32.47mm2/s to 1.73mm2/s and calorific value was increased from 15.21MJ/kg to 19.43MJ/kg, the quality of the emulsified oil was improved significantly. With the increase of carbon chain, the caloric value of bio-oil was increased gradually. And there was no obvious delamination in the mixture and the viscosity was decreased. The ultrasonic time and ultrasonic power had significant influence on the physicochemical properties of the emulsion, when n-butanol and heavy oil were mixed by 1∶1， the viscosity of heavy oil emulsion was effectively reduced after ultrasonic treatment for 10min under 150W. Under the condition of low alcohol content, the emulsifier can effectively increase the stability of emulsion.
