Sorptive H2S removal by impregnated activated carbons for the production of SNG

The desulfurization ability for H2S enriched syngas of several impregnated activated carbons was investigated under dry, oxygen-free conditions to protect a commercial methanation catalyst for SNG production. All sorption experiments were performed at ambient temperature together with the methanation of an N2 diluted syngas at 400 °C. It could be shown that none of the examined activated carbons is able to protect the catalyst from poisoning. The non-impregnated activated carbon shows the best performance with a loss of catalyst activity < 1% until the breakthrough. Impregnations containing no oxygen showed the fastest loss of catalyst activity until the breakthrough. The loading capacities of all impregnated activated carbons are two to four times higher than of those without impregnation. The results show that syngas obtained by biomass gasification, which contains no oxygen, cannot be sufficiently desulfurized by activated carbons. In order to economically perform the desulfurization with activated carbons, it is necessary to add oxygen and water to the syngas. Several publications showed that thereby the loading capacity is elevated by 20 times and the breakthrough time was extended by 30 times.