里川 重夫

For the development of small-scale desulfurization processes such as fuel cell systems, catalytic decomposition of dimethyl sulfide (DMS) to H2S without H2 addition was investigated using a Co/H-Beta zeolitic catalyst, with its acidity controlled via post-synthesis modification. The protonated zeolite (H-Beta) exhibited little catalytic activity at 400 °C, but Co modification significantly promoted DMS decomposition, with a high H2S yield of 50% observed. The optimum Co amount was equivalent to half of the ion-exchange capacity of the original H-Beta zeolite. While the Co/SiO2 did not display catalytic activity, and thus, the coexistence of acid and Co ion sites is necessary in DMS decomposition. The Co species were introduced at the cation sites of the zeolite, suppressing Co sulfurization, which contributed to the high catalytic activity.

This study focused on evaluating the catalytic properties for the reverse water gas shift reaction (RWGS: CO2 + H-2 -> CO + H2O Delta H-0 = 42.1 kJ mol(-1)) in the presence of hydrogen sulfide (H2S) over a Fe/CeO2 catalyst, commercial Cu-Zn catalyst for the WGS reaction (MDC-7), and Co-Mo catalyst for hydrocarbon desulfurization. The Fe/CeO2 catalyst exhibited a relatively high catalytic activity to RWGS, compared to the commercial MDC-7 and Co-Mo catalysts. In addition, the Fe/CeO2 catalyst showed stable performance in the RWGS environment that contained high concentrations of H2S. The role of cofeeding H2S was investigated over the Fe/CeO2 catalyst by the temperature programmed reaction (TPR) of CO2 and H-2 in the presence of H2S. The result of TPR indicated that the co-feeding H2S might enhance RWGS performance due to H2S acting as the hydrogen source to reduce CO2.