Patial Oxidation Of Methane To Syngas Over Ni-based Catalysts

The monolithic Ni/Al₂O₃ catalysts with the calcination temperature varied from300℃to 800℃were investigated for partial oxidation of methane to syngas and thecatalysts were charactered by XRD and TPR methods. The results show that whenthe calcination temperature is in the range of 300-500℃, the dispersion of the activesite increases with the increasing of the calcination temperature. The activity of thecatalysts enhances with the increasing of the calcination temperature. When thecalcination temperature in the range of 500-800℃, the reduction of the catalystbecomes harder and harder with the increasing of the calcination temperature. Theactivity of the catalysts decreases with the increase of the calcination temperature.The catalyst calcined at 500℃shows the best activity.The influence of the reduction temperature and calctination temperature on theactivity of Ni/Al₂O₃ catalyst calcined from 1200 to 1400℃were also investigated.The catalysts were charactered by XRD. The results show that NiAl₂O₄ forms whenthe catalyst was calcined at 1200℃. When the reduction temperature is below800℃, the catalyst exhinbits poor activity because NiAl₂O₄ could not be reduced atthat temperature. When the reduction temperature is 800℃, some NiAl₂O₄ could bereduced to Ni⁰ and the catalyst become more active for partial oxidation of methane.The catalyst exhibits the best activity when the reduction temperature is 900℃because all the NiAl₂O₄ could be reduced to Ni⁰. When the calcinatio is in the range of 1200 to 1400℃, the crystal size of NiAl₂O₄ increases with the increasing of thecalcination temperature, thus NiAl₂O₄ becomes more and more harder to reduce. Sothe activity of the catalyst decreases with the increasing of the calcinationtemperature. When La was added to Ni/Al₂O₃ catalyst, La-Ni/Al₂O₃ exhibits betteractivity for partial oxidation of methane, it is plausible that La can effectivelyinhibit the increasing of the NiAl₂O₄ crystal size.Ni/CeO₂-ZrO₂-Al₂O₃ catalysts for partial oxidation of methane weresuccessfully prepared and the catalysts were characterized by XRD, BET, TPR andXPS methods. The catalytic performance and carbon deposition over the catalystswere investigated in partial oxidation of methane as well. The results show thatNi/CeO₂-ZrO₂-Al₂O₃ catalysts have large BET area, excellent NiO dispersionwhich notably inhibits carbon deposition over the catalysts. All of these factorsmake the catalysts display high activity and good coking resistance and maintainlong-time stability in partial oxidation of methane. The coking resistant ofNi/CeO₂-ZrO₂-Al₂O₃ increases with the increasing of the Al content which canstrengthen the interaction between the active site and the support.