Selective reduction of NO over cobalt phosphate catalyst with C3H6 or CH4

Activity of metal phosphate catalyst in selective reduction of NO with C3H6 was investigated. It was found that Co-3(PO4)(2) and GaPO4 exhibited high catalytic activities in NO selective reduction with C3H6 Among the metal ph osphates tested, Co-3(PO4)(2) exhibited the highest activity. In addition, thermal stability of this catalyst is sufficient to meet practical applicat ion. Co-3(PO4)(2) catalyst, therefore, is promising as a thermostable de-NO , catalyst for lean combustion engines. Selective reduction of NO hardly pr oceeded when CH4 was used as reductant. It was found, however, that loading Pt on Co-3(PO4)(2) is effective for improving the activity in selective re duction of NO. The reaction mechanism in reduction of NO over Co-3(PO4)(2) catalyst was further studied with temperature programmed desorption (TPD) t echniques. Results of NO-TPD and NO direct decomposition experiments sugges ted that N-2 was formed by the dissociative adsorption of NO which is the i nitial reaction step in NO reduction. On the other hand, adsorption of oxyg en on this catalyst is too strong to desorb. Therefore, it is considered th at propene as a reductant removes the surface oxygen formed by decompositio n of NO. In conclusion, this study revealed that Co-3(PO4)(2) is highly act ive and selective in reduction of NO with hydrocarbon, in the presence of o xygen.