The Catalytic Performance Over Diesel Oxidation Catalyst (DOC) In Presence Of Simulated Diesel Exhaust

Pt-based noble metal has been popularly used in diesel oxidation catalytic system due to its excellent activity,high selectivity,and little gap between light-off temperature and completely converted temperature in the reaction of CO and C3H6 oxidation.However,there are several disadvantages existing:the resource of precious metal in our country,the sulfur in diesel is much higher than that in gasline,and the exhaust temperature in diesel system is lower than that of gasline.Thus,how to improve the low temperature activity&sulfur resistance and reduce the use of precious metal is the most focus in the next research.In this paper,the performance of Pt/Ce-Zr catalyst was improved by two methods:one is loading non-noble metal(V?Mo?Ni),and the other is treated the Ce-Zr support by acid.The catalytic activity and sulfur resistance of all catalysts were investigated in presence of simulated diesel exhaust.Besides,the characterization for catalyst was also investigated using BET,XRD?XPS?H2-HPR?CO-TPD?TEM?EDS?NH3-TPD?FT-IR and so on.Firstly,Ce-Zr support with cerium to zirconium mol ratio of 4:1 was prepared by co-precipitation,then a series of Pt-M/Ce-Zr(M=V?Mo?Ni)diesel oxidation catalysts was prepared using the impregnation method.Results showed that:after loading non-noble metals,the low temperature activity for catalysts was improved and the completely converted temperature was reduced.The promoting effect was reduced in descending order of V>Mo>Ni,and the 1Pt-1V/Ce-Zr catalyst showed the highest performance,which was even better than that of 2Pt/Ce-Zr catalyst.The sulfur resistance of catalyst was ameliorated after loading the three non-noble metals.In order to further develop the low temperature activity and sulfur resistance,the Ce-Zr support was treated with 1mol/L H2SO4,labled as Ce-Zr-S.It showed that the low temperature activity of vulcanized catalyst was obviously enhanced,and C3H6 and CO were completely converted before 180 oC over 1Pt/Ce-Zr-S catalyst.What is more important,the catalytic performance of 0.5Pt/Ce-Zr-S was much better than that of 1Pt/Ce-Zr sample.The use of precious metal is obviously reduced,which has a positive effect in energy conservation and environmental pollution control.