The liquefaction of pure -cellulose with hydrogen-donor solvents such as tetralln and 2-propanol was studied In a batch autoclave system under both inert and hydrogen atmospheres. Reaction conditions Involved temperatures between 270 and 400 °C, residence times between 0 and 60 min, and hydrogen pressures between 0 and 500 psi. The use of homogeneous and heterogeneous hydrogenolysis catalysts was also Investigated. Under these conditions, up to 100% of the initial cellulose feed was converted, resulting in oil yields greater than 50%. The oxygen content of the product oil was significantly lower than that of the cellulose feed (less than 25 wt % in most cases), and it generally decreased with increasing reaction temperature. Low and Intermediate temperatures (<360 °C) favored oil production, while higher temperatures Induced severe hydrocracking of the product oil to gases.
The specific physical and chemical characteristics of supercritical solvents and solvent mixtures that can affect the yield and the properties of coal extracts were experimentally investigated. Strong nonideal interactions, such as polar bonding and hydrogen transfer, as well as synergistic interactions in multicomponent solvent mixtures, were shown to produce large deviations from the simple, density-driven supercritical solubility. These interactions can be manipulated to optimize supercritical coal extraction by reducing the severity of the extraction conditions (pressure In particular). Physical and chemical changes occurring in the coal structure during supercritical solvent extraction were also examined.
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