Experimental Study On Methane Reforming And NO_x Storage-reduction Performance With Reforming Gas As Reducer

NOx storage-reduction technology is one of the efficient lean-burn engine NOx after-treatment technologies, and developing the more efficient NSR system is the main objective of this study. To get hydrogen-rich reforming gas and the more efficient NSR system with reforming gas as reducer, methane reforming system and the new NSR system has been studied, and the effects of monolithic catalyst coating processes on NSR performance had been studied as well.In the thesis, the methane steam reforming performance test bench, the methane partial oxidation performance test bench and NSR performance test bench were established.First of all, methane reforming performance was studied. Ni/γ-Al2O3 and Pt/Ni/γ-Al2O3 catalysts were prepared by impregnation method, and the surface characteristics of catalysts were tested by BET and XRD, the effects of different factors on methane reforming were researched by control variable method, including reaction temperature, space velocity, S/C, the different components concentration of mixed gas, the components of engine exhaust gas represented by CO2 and HC. The experiment results show that: the catalysts have good surface structure, both stability and activity are perfect; high reaction temperature can promote CH4 conversion; the O2 concentration will influence reaction temperature; the H2/CO can be adjusted by S/C; CO2 and HC will inhibit catalyst activity. When H2O/CH4 equals 4.2 in the methane partial oxidation reforming, the reaction temperature will go up to 660 oC, CH4 conversion rate will be 67.7% and H2/CO will be 6.03.Then in the study of NSR performance with reforming gas as reducer, Pt/Ba/Ce/γ-Al2O3 catalyst was prepared by the improved SOL-GEL method combined with incipient impregnation. Using NOx storage reduction circulation test, the impact of the reaction conditions, including reaction temperature, reductant concentration, reduction time and space velocity, and components of engine exhaust gas represented by CO2, HC and O2 on the performance of NSR with H2, as reductant were studied. The experiment results indicate that the specific surface area and catalytic activity are favorable; the optimal reaction temperature is 375 oC-425 oC; at 375 oC, with different reductant concentration there’s an optimum reduction time that the NOx conversion rate is highest; the increase of reductant concentration will speed up the NOx desorption, and if the reductant concentration is too high, the NOx conversion rate will drop; the space velocity characteristic is perfect, NOx conversion rate could maintain 86.9% under high space velocity 75000h-1; to some extent CO2 and HC inhibit the NOx storage activity, however the catalyst can regenerate; when O2 concentration is less than 4%, O2 concentration increase will promote NOx conversion; due to the limitation of catalyst NOx storage ability, NOx concentration increase will decrease NOx conversion rate.Lastly in the NSR catalyst coating process study, on the surface of monolithic catalyst coated by SOL-GEL method, the active ingredient distribute evenly and combine with Al2O3 coating closely. The monolithic catalyst has rich surface proe structure, thus NSR activity is high, and at 375 oC the NOx conversion rate can reach 77%.This thesis laid the foundation for efficient NOx aftertreatment technology development using NSR system combined with fuel reforming.