Activated Carbons for Syngas Desulfurization: Evaluating Approaches for Enhancing Low-Temperature H2S Oxidation Rate

Abstract

Its relatively low cost and high surface area makes activated carbon an ideal adsorbent candidate for H2S removal. However, physical adsorption of H2S is not very effective; therefore, methods to facilitate reactive H2S oxidation on carbons are of interest. The performance of H2S removal of non-impregnated, impregnated, and doped activated carbon in low-temperature syngas was evaluated in fixed-bed breakthrough tests. The importance of oxygen content and relative humidity was established for reactive H2S removal. Impregnates especially improved the adsorption rate compared to non-impregnated carbons. Non-impregnated carbons could however retain a high capture capacity with sufficient contact time. In a relative performance test, the best performance was achieved by doped activated carbon, 320 mg g−1. Ammonia in syngas was found to significantly improve the adsorption rate of non-impregnated activated carbon. A small quantity of ammonia was consumed by the carbon bed, suggesting that ammonia is a reactant. Finally, to validate ammonia-enhanced desulfurization, bench-scale experiments were performed in biomass-based gasification syngas. The results show that when the ammonia concentration in syngas was in the tens of ppm range, 40–160 ppm H2S oxidation proceeded rapidly. Ammonia-enhanced oxidation allows utilization of cheaper non-impregnated activated carbons by in situ improvement of the adsorption kinetics. Ammonia enhancement is therefore established as a viable method for achieving high-capacity H2S removal with unmodified activated carbons.

Hydrogen Sulphide and Carbonyl Sulphide Removal from Biogas for Exploitation in High-Temperature Fuel Cells

“…Other similar results for the removal of H 2 S are reported in [44][45][46][47][48] for Cu-functionalized activated carbons, in [49][50][51] for K-functionalized activated carbons, and in [45,52,53] for metal oxides.…”

Development of a simplified gas ultracleaning process: experiments in biomass residue-based fixed-bed gasification syngas

“…To promote more selective and effective removal of each species, i.e., with bed 1 for removal of hydrocarbons and bed 2 for removal of sulfur compounds, air/oxygen feeding to the adsorbent reactor should be directed to bed 2. In our previous articles, it was established that H 2 S removal by the oxidative route in moist gas is limited to low space velocities in its application, while the removal rate significantly improves by the presence of ammonia in syngas [25,26]. Although a high H 2 S removal rate was achieved even in the small bed 1, ammonia-enhanced desulfurization unlikely occurred.…”

Comparison between Conventional and Metakaolin bi-functional Catalyst in the Hydrodesulfurization Operation

“…Studies have been clarified lower LHSV to the half by increasing the catalyst volume to doubling lead to decrease the HDT reactor temperature and reach the same hydro-treating performance when the other conditions remain constant [31]. The surface area, pore volume, and pore size distribution directly effect on HDS operation, it is known that altering the surface functional groups present on the prepare catalyst during prepare step, for example by changing the octahedral layer after calcination step greatly effect on the reaction mechanism of HDS and thus the removal performance [32]. This was evident through the performance evaluation of the prepared catalyst in comparison with the conventional catalyst.…”