Hydrothermal Conversion Of Desert Shrub Salix Psammophila To Bio-oil And Hydrochars

With the intensification of desertification, sand-fixing plants Salix Psammophila were researched increasingly. Its stumping physiological characteristics make the development and utilization of Salix branches attentions. And with the gradual depletion of fossil fuels and the intensification of environmental pollution, the development and use of biomass renewable energy has received worldwide concern. Hydrothermal convertion can covert biomass to liquid fuels in a quick and efficient way for their excellent solvent properties, which makes it a research focus in the field of bio-energy conversion.In this study, the hydrothermal conversion of Salix Psammophila in a batch reactor was investigated. Different processing conditions on the liquefaction yields were studied, and liquefaction products (bio-oil and hydrochar) were analyzed using a variety of detection methods, then the mechanisms of Salix Psammophila liquefaction in water were discussed.Temperature, reaction time, ratio of liquid to solid and the recycling times of processing water significantly affected the liquefaction yields of Salix Psammophila. In the condition without catalyst, temperatures of300℃, the liquid ratio to solid of5:1and reaction time of10min led to the highest bio-oil yield of30.25%, with hydrochar yield of19.21%. The recycling of the processing water could significantly increase the yield of bio-oil from30.3%to46.9%.NaHCO3and K2CO3as catalysts showed good catalytic effect for promoting the liquefaction of Salix Psammophila, and to a certain extent, improved the bio-oil yield. The liquefaction of Salix Psammophila in water at300℃, reaction time of10min, with5%NaHCO3yielded a3.3%improvement of total bio-oil, and the low boiling point fraction (<400℃) of bio-oil was added from64%to73%.The composition of bio-oil obtained by hydrothermal conversion of Salix Psammophila was very complex, containing ketones, phenols, alcohols, olefins, aromatics, furfural and furans. Catalysts showed almost no effects for altering the composition of bio-oils. The water-soluble organics were mainly composed of organic acid the cyclopentenone class and furfural, in which the highest relative content was acetic acid. The hydrothermal conversion process of Salix Psammophila was very complex. It mainly involved hydrolysis and condensation reactions of hemicellulose and lignin, and also interactions between the intermediate products.The HHV of hydrochar from the hydrothermal conversion of Salix Psammophila was from21-27MJ/Kg, and the BET surface area of hydrochar can be288m2.g-1after physical activation. So the hydrochar have the potential to be the solid fuel and adsorbent material.The hydrothermal conversion of Salix Psammophila to obtain bio-oil and hydrochar is of great significance in desertification control, relieving some of the oil crisis and carbon sequestration.