Sub/supercritical Catalytic Liquefaction Of Rice Straw In Synergistic Solvent

The energy consumption in the world has been increased in these years, as thedevelopment of this world. However, the fossil resource is limited, whose amount isdecreasing as the increasing requirement of human. People have to develop a new tripof renewable energy production. The conversion of biomass which is a huge amountand sustainable material to bio-energy is thought to be a hopeful solution for energycrisis.In this study, the liquefaction of rice straw, which is a typical biomass, wascarried out in sub/supercritical1,4-dioxane-water mixture with required solvent ratios.The effect of catalyst on liquefaction products was shown as that the addition ofalkaline catalyst can improve the formation of oil fraction, and decrease residueproduction, resulting in liquefaction conversion ratio increasing. However, when othercatalysts were added into reaction system individually, the residue yields decreased,while oil fraction yields couldn’t be enhanced. Compared with the control, lower oilfraction yields were obtained in several catalysts runs including titanic oxide andferrous sulfate. It can be due to that the several catalystic metal materials werereserved in the autoclave wall and residue film on the inner autoclave wall whichproduced from feedstock after many liquefaction runs. Meanwhile, several catalystadded in this study indeedly reduced the formation of oil fraction.The effects of temperature and residence time on the catalytic sub/supercriticalliquefaction of rice straw with sodium carbonate were studied in this research. Duringthe liquefaction of biomass, intermediate products and free radicals were reacted aspolymerization and repolymerization. The solid products, named as residue, were themain products, when the runs were operated at low temperature. The decomposition oflignin was enhanced with increasing the reaction temperature. The phenoxy radicalswere produced from the decomposition of lignin, while other kinds of radicals wereproduced from the the decomposition of cellulose and hemicellulose. They alwayspolymerized with the intermediate products from the redecomposition ofdecomposition products. After then, the final products were produced. The solubilityand mass transfer ability of mixture were significantly improved, and consequentlyenhanced the wet-decomposition of rice straw, which improved the formation of lightfractions. Meanwhile, higher oil fraction yields were achieved at higher1,4-dioxane ratio inmixed solvent (50,80and100vol.%). The highest heavy oil (PA+A) yield wasobtained at the1,4-dioxane ratio of20vol.%, while the lowest residue yield wasrealized in the mixture of1:1. In other words, more complete decomposition of ricestraw was obtained in the mixture with volume ratio of1:1.The oil and PA+A fractions were analyzed by FTIR and GC-MS, in order toidentify the main compounds in those fractions. the chemical compositions of oil werethe inclusion of a lot of complex compounds such as phenols, aromatics, esters(straight chain and aromatic esters), alkanes, alcohols, etc, while the compositions inthe PA+A were the inclusion of a lot of complex compounds such as phenols,aromatics, aromatic esters, aldehydes, alkanes, ketones, aethers, etc. Phenoliccompounds are the major compounds identified in all the liquefied products, followedby ester derivatives, hydrocarbon, organic acids and alcohols.