Optimization of bio-oil production from hydrothermal liquefaction of cyanophyta

To optimize the HTL process of Cyanophyta, and study the influence of interactions of reaction conditions as well as the reaction mechanism, this paper conducts a research on the effects of reaction temperature (250-370℃), reaction time (20-50 min), solid concentrations (5%-20%) and their interactions on the bio-oil yield using hydrothermal liquefaction of Cyanophyta through designing a response surface experiment with three factors and three levels. In addition, the distribution and conversion of compounds in bio-oil were analyzed by determining the total organic carbon (TOC), the ammonia content in water soluble product and the organic structures in bio-oil. The result showed that, with the temperature rising, the bio-oil yield and nitrogen recovery are both increased, however the TOC recovery in water soluble product is decreased significantly; the increase of reaction time and solid concentrations had positive influence on nitrogen recovery, but little effect on TOC recovery. The results of FT-IR analysis of bio-oil sample demonstrated that bio-oil contains alkanes, esters, ketones, carboxylic acid, olefine and alcohols, etc. Based on the analysis of variance and regression fitting of quadratic polynomial regression models, the optimum reaction conditions of hydrothermal liquefaction of Cyanophyta can be obtained:reaction temperature 369.99℃, reaction time 40.33 min, solids concentrations 5%. In this condition, the highest predicted bio-oil yield of 33.73% can be reached.