[en] Elevated-temperature pressure swing adsorption could potentially replace wet methods in the field of syngas purification. However, the reversibility of sulfur removal in this technique needs to be validated. In this study, the H₂S adsorption reversibility of two types of activated carbon sorbents were evaluated on a fixed-bed reactor. The effects of desorption method and desorption temperature were studied. Elevated-temperature vacuum desorption was found to be effective for regenerating adsorbents saturated with H₂S. The necessities of both vacuum desorption and elevated temperature were reported. The findings were explained on the basis of the characterization results obtained using pore distribution analysis, inductively coupled plasma, and X-ray photoelectron spectroscopy. The oxidative functional groups or adsorbed O₂ reacted with H₂S on the surface of the adsorbents and the resultant, i.e., elemental sulfur, damaged the pore structure. The richness of the pores with a diameter range of 0.7–0.8 nm decreased by nearly 50% after several adsorption–desorption cycles. At high temperatures and under vacuum atmosphere, element sulfur could be easily distilled and removed from the fixed bed. Thus, element sulfur would not accumulate on the adsorbent, thus ensuring the reversibility of H₂S.

[en] Hydrogen from coal-based syngas is usually purified by deep desulfurization and decarbonization scrubbing technologies. Such electricity consuming processes cost a large number of heat exchangers and compressors. In this study, a two-stage demonstration unit had been constructed and demonstrated to purify hydrogen (including useful nitrogen for ammonia synthesis) from on-site sideline shift gas mixture at Yangmei Fengxi ammonia plant. For the first stage, an 8-column hydrogen purification process by novel elevated temperature pressure swing adsorption (ET-PSA, operated at 180 to 220 °C) was developed and demonstrated to capture H₂S and CO₂ simultaneously by hydrophobic activated carbon (AC) to reduce the impurities compared to that of room temperature PSA. Working condition at elevated temperature was proved to be appropriate and stable for reversible H₂S removal by AC. The second stage was a temperature swing adsorption for deep purification of CO to 0.2 ppm by commercial CuCl monolayer dispersed zeolites (PU-1 synthesized by Beijing Peking University Pioneer Technology Co., Ltd.). In order to examine the standard of trace impurities such CO and H₂S in product H₂, the purified H₂ was offered to a 3 kW proton exchange membrane fuel cell (PEMFC) stack to prove that all carbon and sulfur impurities met the demand not only for ammonia synthesis, but for PEMFC as well. Besides, two novel PSA steps: high pressure steam rinse and low pressure nitrogen purge were adopted to improve H₂ recovery to above 93%. To demonstrate its stability, over 2500 h of operation had been carried out on the small-scale demonstration rigs by far.