High sulfur-tolerant Pt/Ce_0.8Gd_0.2O_1.9 catalyst for liquid hydrocarbon fuel processing in PEMFC applications

A high sulfur tolerant Pt catalyst has been developed for fuel processor that is being developed for use with PEMFC, using a fluorite-type Ce_0.8Gd_0.2O_1.9(CeGdO) oxide as support that was synthesized by citric acid sol-gel method. Sulfur tolerance of the catalysts was tested in SR of iso-octane at 750°C and a WHSV (iso-octane) of 1.0h^-1 with a steam/C ratio of 3, using thiophene as sulfur source. It was found that catalyst calcination temperature is crucial to ensure the maintenance of the sulfur tolerance. The catalyst that was calcined at 800°C maintained its activity and selectivity for the entire 100h test using iso-octane with 300ppm or more sulfur whereas the catalyst that was calcined at 600°C lost its activity slowly in this course due to both sulfur poisoning and its poor thermal stability. The catalyst calcined at 800°C was also tested using iso-octane with 500ppm sulfur for a 100h run, and it was found that the conversion of iso-octane was slowly decreased to ∼90% within ~50h and then was sustained at ∼90% throughout the test while H₂ concentration was slightly dropped from ∼72% to ∼70%. In addition, sulfur balance measurements together with FTIR and microculounmetric titration analyses for surface sulfur-containing species on the used catalyst suggested that thiophene sulfur was completely converted into H₂S, probably complying with a redox mechanism. Furthermore, hydrogen TPR and XRD analyses, together with comparison of the reactivity for Pt/CeGdO catalysts with a Ni/CeGdO and a Pt/Al2O3, showed that synergetic effect between CeGdO oxide and Pt at the interface existed while being enhanced and consolidated with the calcination treatment at 800°C, which made Pt immune to sulfur poison and active to convert thiophene sulfur into H₂S. Its satisfying performance for ATR and SR of commercial gasoline with ∼200ppm sulfur will be also demonstrated.