SYNTHESIS GAS SOLUBILITY IN FISCHER-TROPSCH SLURRY
Abstract
The solubilities of gases in n-paraffins and in wax mixtures are measured and correlated. Results of this work are useful for process design and for studying reaction kinetics of Fischer-Tropsch synthesis in slurry reactors. A semi-flow apparatus is designed and constructed for the measurements of gas solubilities in molten waxes. Test data of CO$\sb2$/toluene mixture show excellent agreement with literature data from a static apparatus. Five gases are studied: hydrogen, carbon monoxide, methane, ethane, and carbon dioxide. Data measurements are completed for each gas in n-eicosane (C$\sb{20}$), n-octacosane (C$\sb{28}$), and in n-hexatriacontane (C$\sb{36}$) as well as in an industrial wax over 100 to 300$\sp\circ$C and 10 to 50 atm. Solubilities of gas mixtures of H$\sb 2$ + CO in n-C$\sb{28}$ are also measured at several equilibrium gas compositions. The gas K-value, defined as the ratio of the composition in the vapor phase to that in the liquid phase, is found independent as gas compositions within experimental errors. The Krichevski-Kasarnovsky equation represents well the data of binary systems. Henry's constants and partial molar volumes of gases at infinite dilution are determined from the equation. The Redlich-Kwong-Soave equation of state is modified to describe the vapor pressures of n-paraffins up to n-C$\sb{100}$. The modified equation is combined with a new mixing rule, whose derivation is based on a polymer solution theory, to correlate our data, and the results are satisfactory. Furthermore, the adjustable parameter can be correlated as an asymptotical function of the solvent molecular weight except for H$\sb 2$ and CO at the lowest temperature. This asymptotical behavior makes it possible to predict gas solubilities in heavy n-paraffins. The modified equation with correlated parameter can predict the gas mixture solubilities in n-C$\sb{28}$. Also, gas solubilities in a wax mixture can be predicted if the wax is treated as a pure n-paraffin with the same number average molecular weight.
Degree
Ph.D.
Subject Area
Chemical engineering
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