Simulated countercurrent moving-bed chromatographic reactor for the oxidative coupling of methane: Experimental results

摘要

The oxidative coupling reaction of methane (OCM) represents a potential commercial ethylene production route. However, the highest reported yields do not exceed 20%. The methane coupling reaction is accompanied by the undesired conversion of methane to carbon oxides. The relative amount of oxygen and methane along with other parameters, including temperature, determine the favored reaction pathway. High hydrocarbon to oxygen feed ratios give high ethane/ethylene selectivities but at the expense of the hydrocarbon conversion. When the methane to oxygen feed ratio is low, combustion is favored. The simulated countercurrent moving-bed chromatographic reactor (SCMCR) is applied to the OCM. A modified experimental configuration is designed and evaluated. A four-section apparatus, each containing a reaction and two separation columns, is used to quickly separate the reactants and products using the principles of simulated countercurrent flow. Simultaneous reaction and separation of the reactive products column is desired, but unattainable because of an incompatibility between OCM reaction and separation temperatures. Microreactor yields with a samarium oxide catalyst gives yields between 2% and 10%. Yields as high as 50% are observed with the same catalyst and run conditions in the SCMCR. These yields are significantly higher than previously reported values. The effects of temperature, feed switching time, and methane to oxygen feed ratio have been investigated. The reactor, while not fully optimized, does give promise as an alternative production method for ethylene.