Phosphorus deactivation on co-based catalysts for Fischer-Tropsch

Abstract

The effect of phosphorus on a cobalt-based catalyst for Fischer-Tropsch Synthesis (FTS) has been investigated. Phosphorus is an impurity present in biomass and, in this work, its deposition on the catalyst during biomass to liquid (BTL) operation, based on gasification and FTS, has been mimicked. For this purpose, four different cobalt-manganese-rhenium catalysts supported on alumina were prepared by incipient wetness impregnation with different phosphorus loadings. The results showed that below 800 ppm of phosphorus, the catalysts performance was not significantly affected, possibly because the interaction of phosphorus mainly was with the alumina support. However, above this threshold, the effect of phosphorus was noticeable with a decrease in intrinsic activity. The reduced performance can be attributed to a physical blocking of cobalt sites. But, in all poisoned catalysts, the product distribution was affected and shifted towards less valuable products as methane and light paraffins. The electronegativity of phosphorus might be the cause for this effect, as the effective H2/CO ratio on the catalyst surface may be increased due to a weakened metal-CO bonding and consequently, the selectivity of the hydrogenated products increased.