Hydrothermal Liquefaction Of Water Hyacinth In Hot Compressed Water

As one of the most invasive plants in the world, water hyacinth can not only destroy the water ecosystem and irrigation works by its fast growth rate, but also cost great human resources with potential environmental problems existed. Thus, it’s really important to find an efficient way to resolve the environmental and economic problems caused by water hyacinth.Hydrothermal liquefaction of biomass in hot compressed has been a promising thermal chemical method for its dry-free process, which would be suitable for the conversion of wet biomass. Great attention has been drawn on the liquefaction of algae and aquatic plants.In this study, the liquefaction of cellulose, dealkalized lignin and water hyacinth was conducted in a batch reactor. The products obtained from the liquefaction process under different conditions were analyzed. Moreover, the reaction mechanism of cellulose and lignin in hot compressed water was also investigated, based on what a reaction process of the liquefaction of water hyacinth was proposed.The reaction temperature, reaction time, and solid-to-liquid ratio could significantly affect the yields of the liquefaction products from cellulose, lignin, their mixtures, and water hyacinth in hot compressed water. The convenient condition for the liquefaction of cellulose was the temperature of320℃with a reaction time of20min and the solid-to-liquid ratio of1:30, while for the liquefaction of lignin was300℃with a reaction time of20min and he solid-to-liquid ratio of1:30. As for the liquefaction of water hyacinth, with a reaction time of10min and a solid-to-liquid of9g:150mL, the highest yield of heavy oil (HO) was obtained at320℃. What’s more, the mixtures of cellulose and lignin with a ratio of2:1could get the highest yield of heavy oil compared to other mixtures.The Composition of oil products produced from the liquefaction of cellulose was proven to be high complex. Based on the analysis of liquefaction production, the liquefaction of cellulose could be divided into three steps:hydrolysis process→degradati on process→the deep reaction process of the degradation products. With an acid circumstance, firstly the cellulose could be hydrolyzed to glucose. Then the glucose would be rapidly degraded to5-HMF, which would further transformed to furans, furfurals, and esters through a series of reactions like decarburization and hydrogenation. With the reaction temperature raised to320℃, the deeper reactions of furans and furfurals could produce phenols.The main contents of heavy oil produced from the liquefaction of lignin were phenols, aldehydes, esters, ketones, and fatty acids, most of which contained benzene ring. In the liquefaction process, the lignin was first hydrolyzed to benzenoid compounds by the crack of chemical bonds between the monomers. Then there would be further reactions happened to the branched chain of benzene rings since the benzene rings was very stable.The oil products obtained from the liquefaction of water hyacinth were also highly complex. The higher heating value (HHV) of heavy oil illustrated that the liquefaction of water hyacinth in hot compressed water has the potential to produce the products with high energy density. The main contents of water soluble products were phenols and cyclopentenone, which could be used as useful biochemical.A liquefaction process of water hyacinth in hot compressed water was proposed, based on the investigation of the liquefaction of cellulose and lignin. It was found that, the conversion rates of cellulose part in water hyacinth were much faster than cellulose alone in hot compressed water. Phenols were detected in the water soluble products obtained at240℃, which made it impossible to determine the liquefaction of lignin part in water hyacinth.To explore the interaction between the cellulose and lignin parts in water hyacinth, the liquefaction of mixtures of cellulose and lignin were also conducted. The results showed that the mixture of cellulose and lignin led to higher yields of heavy oil but lower yields of water soluble oil and solid residue. However, the higher conversion rates of cellulose part in water hyacinth should have no relationship with the lignin part.