Influence of silicon on uptake of H2S by a coke under elevated temperature

The effect of silicon, a “non-active” element, on uptake of H2S by carbon matrix of a coke under elevated temperature was studied. A quartz tube reactor was coupled with a flame photometric detector (FPD). The sulfur uptake/temperature programmed desorption (SU/TPD) process was used to simulate coal pyrolysis or coking process. The SU was carried out at 300 °C. The TPD was carried out from 300 to 1000 °C to desorb physically or loosely bonded sulfur species. Temperature programmed oxidation (TPO) process was used to measure amount of sulfur chemically or tightly imbibed by coke. The results show that the H2S uptake is higher for a demineralized coke than that for its parent coke. The presence of silicon showed a significant negative effect in H2S uptake. The H2S uptake decreased gradually as the silicon content increased from 0 to 0.6% (w/w). XPS and SEM-EDX were used to characterize silicon on the coke surface. The results show that the silicon loaded on the coke surface is in the form of SiO2 or metal-silicates which may possibly inhibit the reaction of H2S and coke. The silicon and sulfur distribute unevenly on the coke surface and tend to concentrate at similar locations, which indicate that the active sites for H2S adsorption and reaction at high temperatures are also active for attracting silicon species.