Low-Temperature H2S Removal from Steam-Containing Gas Mixtures with ZnO for Fuel Cell Application. 1. ZnO Particles and Extrudates

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• 作者：Ivan I. Novochinskii ; Chunshan Song ; Xiaoliang Ma ; Xinsheng Liu ; Lawrence Shore ; Jordan Lampert ; and Robert J. Farrauto
• 刊名：Energy & Fuels
• 出版年：2004
• 出版时间：March 2004
• 年：2004
• 卷：18
• 期：2
• 页码：576 - 583
• 全文大小：198K
• 年卷期：v.18,no.2(March 2004)
• ISSN：1520-5029

文摘

Sulfur removal is important for a fuel cell that uses a hydrocarbon fuel, such as natural gas,liquefied petroleum gas, and gasoline, to prevent the downstream sulfur poisoning of catalystsin the fuel processor and in the fuel cell anode. Although most sulfur species are removed priorto reforming, the reducing environment of the reforming stage (such as autothermal reforming)converts residual sulfur to hydrogen sulfide (H₂S). H₂S in the reformate must be removed toensure longevity of the catalysts in downstream processing and in the anode chamber of fuel cellsystems. A unique modified ZnO sample with a different morphology has been prepared andcomparatively studied together with a commercially available ZnO sample under variousconditions. Extremely low H₂S outlet concentrations-as low as 20 parts per billion by volume(ppbv)-have been observed over the modified ZnO sample for extended periods of times. Thesulfur-trap capacity (the amount of H₂S trapped before breakthrough) also is dependent on spacevelocity, temperature, steam concentration, CO₂ concentration, and particle size. Higher capacityis observed at higher H₂S inlet concentration of 8 ppmv, compared to lower inlet concentrationsof 1-4 ppmv. The trap capacity decreases monotonically as the temperature increases. Steam inthe reformate inhibits the capture of H₂S by ZnO; it seems to shift the equilibrium of the reactionZnO(s) + H₂S(g) ZnS(s) + H₂O(g) to the left, toward ZnO and H₂S. The effect of steam seemsto be reversible. Increasing the CO₂ concentration in the feed up to 12 vol % decreases the capacityof ZnO for the capture of H₂S.