Effective utilisation of the catalyst bed deactivating in the course of oxidative coupling of methane

Abstract

The possibility of improving the effectiveness of utilisation of a LiMgO catalyst fixed bed, gradually deactivating in the course of oxidative coupling of methane, was examined. It was confirmed that a hot-spot area was the only working region of the bed and the area of the catalyst ageing. Applying a scaled-up laboratory unit with a heat-resistant stainless-steel tubular reactor, it was demonstrated that under applied conditions, the deactivation attributed to the loss of a significant part of Li led to the decrease in selectivity of C2 hydrocarbon formation. It was shown that by changing the feed inlet locations, parallel to the progress of ageing, the successive active catalyst layers could be involved in the process, giving unchanged overall selectivity. It was discovered that during the process of CH4 transformation over the bed prepared from the mixture of a fresh and deactivated LiMgO, the transport of Li from the component richer in Li (its deactivation) to the poorer one (its regeneration) occurred. This fact should be taken into consideration in establishing the proper mode of operation and, eventually, the sequence of changes in the feed inlet locations, applied with time on stream.