Ionic conducting ceramic membrane reactor for partial oxidation of light hydrocarbons

Dense tubular membrane reactors using Bi_1.5Y_0.3Sm _0.2O_3-δ (BYS) may provide a method for increasing the selectivity and yields of partial oxidation of methane across the threshold required for commercial application. The development of a dense tubular membrane reactor that successfully optimizes reaction variables for maximal efficiency requires the preparation of dead end dense tubular membranes, the design of a reactor, high temperature sealing of the tubes, and systematic empirical and theoretical studies of process variables.; Dense BYS tubes are fabricated by cold isostatic pressing method. The membrane reactor vessel is designed to ensure isothermal conditions for the tubes and for monitoring and controlling of the experiments. The isothermal condition requires the successful accomplishment of a high temperature sealing of tubular membranes onto inert ceramic tubes. A methodology to select a ceramic-glass composite seal is developed. Based on this methodology, BYS tubes are successfully sealed onto a mullite tube using a pyrex glass and BYS powder based seal.; Following the design of the BYS tubular dense membrane reactor, a series of experiments that vary over ranges of P_O2, P_CH4, temperature and flow rates are conducted. Best one-pass C₂ (C₂H ₄+C₂H₆) yield achieved for oxidative coupling of methane in the BYS dead-end membrane reactor is 35% at a C₂ selectivity of 54% at 900°C. The oxygen permeation fluxes through tubular BYS membrane reactors under oxidative coupling of methane reaction conditions are approximately 1.5 to 3.5 times higher than those under oxygen permeation conditions with He as the purge. The same membrane reactor was also used to conduct a series of experiments to study the selective oxidation of ethane to ethylene.; At 875°C, per pass ethylene yield of 56% with ethylene selectivity of 80% was obtained in the membrane reactor. Under reaction conditions, the oxygen permeation flux through the dense membrane is over an order of magnitude higher than those under oxygen permeation conditions with He as the purge. The differences in the oxygen permeation fluxes obtained through the BYS membrane during oxidative coupling of methane and selective oxidation of ethane experiments are explained by a mathematical model that takes into account the downstream conditions and reaction taking place.