Abstract: CO or/and NO co-adsorption on reduced Co/Al_2O_3, Mo/Al_2O_3 and Co-Mo/Al_2O_3 was studied by TPD-MS, IR and XPS. It was found that there exist two kinds of Mo-sites and three kinds of Co-sites on reduced Co-Mo/Al_2O_3. For Mo--sites, One is a weaker adsorption NO (T_(max): 100 ℃) which can be replaced by adsorption CO another is a stronger adsorption NO (T_(max): 300 ℃) which is not replaced by CO. Three kinds of Co--sites for NO adsorption emerged desorption peaks of NO at 80 ℃, 180 ℃ and 330 ℃ respectively. Former two can adsorb CO however, the latter only adsrb NO and all CO adsorbed on Co—sites can be replaced by co-adsorptoin NO.
Results of IR provided further evidence about existence of various Mo—sites and Co—sites. Results of XPS indicate that ratio of total Mo/Al is constant, but relative density of Mo~(4+) increase with reduction temperature. While ratio of Co/Al decrease due to Co on surface introduced in bulk phase of Al_2O_3 when reduction temperature raised. In this work it was not observed the existence of direct interaction between Co—sites and Mo—sites, which results in change of property relative to adsorption of CO and/or NO on Co—sites and/or Mo—sitews in the range of reduction temperature from 400 to 600 ℃.