Kinetic and Process Modeling of Guerbet Coupling Chemistry over Cu-Mg-Al Mixed Oxides

Abstract

In this paper we demonstrate the process chemistry for conversion of ethanol into C6+ alcohols that can then be converted into diesel fuel ethers. Ethers generated from the dehydration of C6+ alcohols produce a fuel that satisfies diesel engine requirements, therefore selective production of C6+ alcohols is of particular interest. The desired hexanol is synthetized through ethanol and butanol coupling, accompanied by formation of undesired products through several reaction pathways. We obtain kinetic data for ethanol and butanol conversion over Cu0.01Mg2.99AlOx to produce C6+ alcohols through Guerbet coupling reactions. Two series of catalytic tests were performed at 325 °C and 300 psig by using either pure ethanol feed or a cofeed ethanol-butanol 70-30 mole%. A kinetic model was developed to predict the product distribution over a wide range of contact times. Kinetic parameters were regressed by coding a routine that included solution of differential mole balances embedded in an optimization problem. The herein developed kinetic model was integrated in a process simulation flowsheet that models the upgrading of ethanol into C6+ oxygenates. The butanol cofeeding strategy in the simulations was approached by recycling the produced butanol into the coupling reactor. The simulation results reveal that cofeeding butanol into the Guerbet reactor enhances initial production rates of C6+ alcohols, at expenses of fostering production of byproducts from butanol self-coupling. A maximum carbon yield of 82.2% for C6+ diesel fuel precursors can be obtained by minimizing the byproducts production after introduction of a hydrogenation reactor .