Study On Cu-Based Catalysts For On-board Hydrogen Production From Oxidative Steam Reforming Of Methanol

Diesel engines exhaust much higher nitrogen oxides,carbon particles,and other pollutants than gasoline counterparts,which brings serious challenges to air pollution control.Hydrogen-adding combustion can significantly improve the combustion efficiency of diesel engines and reduce exhaust gas pollutant emissions.It is an effective means to solve diesel exhaust pollution from the source.The reaction conditions for hydrogen production from methanol reforming are mild,and the reactor can be placed in the exhaust pipe to make full use of the residual heat of the exhaust gas to produce hydrogen.This dissertation focuses on the design and synthesis of high-performance copper-based heterogeneous catalysts for hydrogen production from methanol reforming of diesel engines.The copper-zinc-aluminum catalysts prepared by co-precipitation method and the copper-nickel catalysts prepared by impregnation method were studied,mainly the activity and stability tests.This work could provide some theoretical basis for expanding the copper-based catalysts in the on-board hydrogen production from methanol reforming.The experimental results showed that when the aluminum content was fixed for the co-precipitated Cu-Zn-Al catalysts(calcined at 350?),the catalyst performance increased with the increased Cu/Zn ratio in the temperature range of 200?600?.The addition of zinc significantly reduced the specific surface area of the catalysts,while the Cu-ZnO interaction has a significant effect on the catalytic activity because zinc could improve the metal dispersion and reducibility of the Cu2+ species.Zinc is essential to this catalyst.Zinc oxide alone had a catalytic effect at the high temperature range of 400?600?,but this effect was very limited.The synthesized Cu30Zn10Al catalyst behaved similarly to the commercial Cu-Zn-Al catalysts in terms of activity and hydrogen production rate,but the copper content in the former was much lower than that of the latter,thus reducing the metal cost.Moreover,the Cu30Zn10Al catalyst was more stable than the commercial one after aging treatment.In Cu/Ni/?-Al2O3 catalysts prepared by impregnation method(calcination temperature 550?),the methanol conversion rate increased at the beginning and then decreased with the decreased copper loading and increased nickel loading;and the hydrogen yield was also following the same trend.Copper and nickel have excellent synergistic effect,that is,loading copper and nickel simultaneously had a better catalytic effect than just loading copper or nickel alone when the total loading amount was fixed.Of all the catalysts prepared,the catalyst(CNA-2)with the load of wt.%:5%Cu5%Ni was the best one.A great change was observed for the selectivity of carbon monoxide in the bimetallic catalysts at 400?:Below this temperature,the selectivity of carbon monoxide was much higher than that of carbon dioxide,while the selectivity for carbon dioxide was much higher when above this temperature.Stability tests also found that the catalyst CNA-2 could maintain the activity and hydrogen production rate without any declining for a long period of time at 400?.