| The pollution of engines' exhaust has already attracted widespread attention, in which the nitrogen oxides may cause acidic rain and photochemical smog. It takes serious danger to agriculture, forestry and human health. Therefore, how to remove the nitrogen oxides in automobile exhaust was an important problem. There are many measures to eliminate nitrogen oxides, Selective Catalytic Reduction (SCR) process is one of the effective measures.In this paper, the activity of the Cu series catalysts modified by silica-sol with cordierite honeycomb as support and urea as reductant was studied. NO was reduced in fixed-bed fluxion reactor using temperature progress method. And systematically investigated the influences of the methods with different roasted temperature, different Cu loading. The addition of Mn element was also investigated. We analyzed the physical properties, crystal structures and surface structures of the catalysts by SEM, BET and XRD techniques.The results showed that the activity of the Cu catalysts increased remarkably after modification using silica-sol at the researched temperature between 300℃and 500℃. The optimal concentration of Cu(NO3)2 for making Cu-O/SiO2/CC was 1mol/L. The conversion rate of NO reached 52% when the reaction temperature was 400℃.Activity was investigated at different airspeed. The results revealed that the airspeed had important effects on catalytic activity. The catalytic activity decreased when airspeed was improved. The activity of CU-O/SiO2/CC had not decreased when the catalytic reactions were conducted 48 hours in fixed-bed fluxion reactor under 400℃. And the surface structures of the catalysts were not destroyed.The effect of the addition of La in Cu/SiO2 was also researched. The results showed that addition of La could not improve the activity of catalysts and make the activity decreased to some extent. Moreover, with the La loading increasing, the extent was enlarged. The addition of Ce would enhance the high temperature activity of catalysts on No conversion .The addition of Ni improved catalytic activity at high and low temperature, especially when the concentration of Ni(NO3)2 was 0.3mol/L.The addition of Co had not changed the activity. The catalytic reactions of the mixed metal oxides added with Mn were conducted under different temperature and airspeed The results revealed that the activity of Cu-Ni-Mn-O/SiO2/CC much better than that of Cu-Ce-Mn-O/SiO2/CC.The catalytic samples were characterized by XRD, BET, and SEM techniques. The research results showed that the larger BET surface area and pore diameter, the more favorable for SCR NOx with CO(NH2)2. The results indicated that the surface elements of the catalysts existed in the form of oxides. The diffraction peak of Mn element was not found. From SEM investigated, the active center of Cu-Ni-Mn-O/SiO2/CC appeared more homogeneous and smaller compared with other catalysts. And the activity of Cu-Ni-Mn-O/SiO2/CC reached 94%, the surface area reached 29.71 m2·g-1.
|
PDF Full Text Request