Thermochemical Liquefaction Of Rice Husk For Bio-oil Production In Mixed Solvent (Ethanol-water)

Thermochemical liquefaction of rice husk in mixed solvents ethanol-water （v/v,0:10,5:5,10:0） was investigated in a stainless steel autoclave at differenttemperatures from260to340°C. The paper analyzed reaction conditions (i.e. reactiontemperatures, ethanol-water ratio, feedstock/solvent ratio and solvent filling ratio)and the relationship between the liquefaction conditions and liquefied products yieldas well as characterization of products. Meanwhile, the optimized reaction conditionsof liquefaction was established by analyzing the total conversion of liquefaction, theyields of products（bio-oil, solid residue and gas/water. The properties and chemicalcomposition of bio-oils was analyzed by a series of chemical analysis methods toexplore controllable liquefaction route and provide theoretical basis for improvementof the yield and quality of bio-oil products.Thermochemical liquefaction characteristics of rice husk in mixed solvent(ethanol-water) were investigated in this study. The solvent and temperature wereimportant effects of liquefaction of biomass. Compared with pure water or ethanol,the mixed solvent showed synergistic effect at a relatively lower temperature. Thehighest bio-oil yield was obtained at533K in ethanol-water mixed solvent (V/V,5:5)and found to be21.15%. In pure water and mixed solvent treatments, the yield ofbio-oil declined with reaction temperature increasing from533K to613K. However,with the pure ethanol as solvent, the bio-oil yield increased firstly and then decreasedslightly. In addition to this, the effects of solid-liquid ratio and solvent filling ratio onthe distribution of liquefaction products were also explored with ethanol-water mixedsolvent as medium. The results show that higher solid-liquid ratio resulted in lowerbio-oil yield, while the increase of solvent filling ratio led to an incr ease in the bio-oilyield.It was established by the GC-MS analyses that the compositions of bio-oil fromrice husk consisted mainly of phenolic compounds, long-chain alkanes, saccharides,ketones and esters. On the other hand, compared with pure water or ethanol, therelative concentration of phenolic compounds in mixed solvent run was higher andreached up to21.22%.The elemental analysis results showed that, the heat value of bio-oils form mixedsolvent treatments were almost the same with that from sole ethanol solventtreatment（s27.04and27.56MJ/kg respectively）. And from this, we can conclude that, compared with the more expensive ethanol solvent, ethanol-water mixed solvent canbe a better choice as liquefaction solvent considering its lower cost a nd betterliquefaction effects.The results of SEM analyses indicated that during the liquefaction of biomass,the structure and composition of rice husk has changed a lot, while a mass ofinterspace was also existed in the SR. The experiments showed that compared withethanol solvent, water could be more helpful with the lignocellulosic biomassliquefaction, and the ethanol-water mixed solvent was effect well.China has an abundant supply of cheap rice husk resources. Considering the vastmajority of rice processing factory has implementation, to facilitate centralizedcollection and utilization of rice husk resources have advantages. Therefore,transferring the rice husk into new energy resources, instead of fossil fuel combustion,can effectively reduce resource waste and environmental pollution problems.