OPTIMIZATION OF THE SIMULATED COUNTERCURRENT MOVING-BED CHROMATOGRAPHIC REACTOR FOR THE OXIDATIVE COUPLING OF METHANE

This work deals with the further development and optimization of a sim ulated countercurrent moving bed chromatographic reactor (SCMCR) for t he oxidative coupling of methane (OCM). To optimize the adsorptive sep aration of OCM products from unreacted methane, different adsorbents w ere selected and tested. Hydrophobic carbon molecular sieve, examined along with other adsorbents (activated charcoal and zeolite with high silica/alumina ratio), appears to be the most suitable choice, both fo r methane storing and for efficient handling of the OCM separation. Th ree catalysts, Sm2O3, Y1Ba2Zr3O9.5, and Y1Ba2Ge1O3.5 have been studied in microcatalytic reactor experiments. The Y1Ba2Zr3O9.5 catalyst prov ed to be the best, giving 84% selectivity to C-2-products at a CH4/O-2 ratio of 11 and nearly complete oxygen conversion. A detailed model o f the SCMCR employing experimental information about the catalyst and adsorbent properties was developed to analyze the complex cyclic behav ior of the SCMCR. It was found that observed methane loss, and therefo re decreased conversion, are caused by incomplete desorption of methan e in the carrier section of the SCMCR. This effect can be minimized by selecting a better adsorbent. The influence of the switching time and CH4/O-2 ratio in the make-up feed, the two most important parameters in this system, on reactor performance was analyzed. It was shown that for the best catalyst (Y1Ba2Zr3O9.5) at optimal operating conditions the SCMCR can give 55% yield for C2 products at 75% methane conversion . Adaptive flow switching and the use of a non-uniform make-up feed ap pear to be promising methods for further optimization of the SCMCR.