Study Of The Preparation And Catalytic Properties Of Cu/Ni/Zr Methanol Cracking Catalyst For Vehicle

The waste heat of engine tail gas is used to crack methanol to generate combu stible gases such as pyrolysis gas H₂ and CO,which are then passed into the engin e for combustion to improve the economy and emission of the engine.The perform ance of the catalyst directly affects the content of each component of the pyrolysis gas and plays a crucial role in the whole alcohol-hydrogen power system.Before the study,other team member has found Zr additives for methanol crack ing performance of Cu/Ni catalyst is better than other element.In this paper,the C u/Ni/Zr methanol cracking catalyst has been further optimized,respectively from the preparation methods,Zr content changes,thermal stability and time stability,combi ned with XPS,XRD,TGA-DSC,TPR,SEM,BET and other characterization metho ds are analyzed.the mechanism of methanol cracking over Cu/Ni/Zr catalyst was ob tained.Finally,the differences of engine power,economy and emission between the improved catalyst and the original catalyst were compared and analyzed.The effects of co-precipitation,co-impregnation and citric acid complex methods on the performance of the catalyst were studied in the temperature range from 220℃to 320℃.The experimental results showed that from the perspective of pyrolysis rate and H₂ content,the order of activity of catalysts prepared by different preparat ion methods was as follows:co-impregnation method≥citric acid complex method>co-precipitation method.The effect of Zr content variation on the performance of Cu/Ni/Zr catalyst was studied.From the perspective of practicality and economy,the Cu/Ni/Zr catalyst wit h 10wt%Zr has the highest cracking rate and catalytic activity.The Cu/Ni/Zr catalys t with 5wt%Zr has overall higher H₂ and CO selectivity than other catalysts,but its pyrolysis rate is lower at low temperatures.The thermal stability of the catalyst was analyzed,and the pyrolysis rate increa sed gradually with the increase of temperature.When the temperature was higher th an 300℃,the pyrolysis rate basically approached to 100%and remained unchanged.The content of H₂ and CO increases first and then decreases and increases;by-prod ucts such as CH₄ and CO₂ first decrease,then increase and decrease,and reach a p eak at 550°C.According to the analysis of the time stability of the catalyst,the pyr olysis rate and product content of the catalyst did not change with time.Regarding the reaction mechanism of Cu/Ni/Zr catalysts,Cu⁰ is the active cente r of the catalyst during methanol cracking reaction.Among them,the discovery of t he reaction pathHCOOCH₃→CH₄（10）CO₂ and the reactionHCOOCH₃→H₂（10）CO ar e the important basics to determine the reaction rate.Compared with the original catalyst used in the engine experiment,the Cunizr（10wt%Zr）catalyst prepared in this experiment can increase the methanol cracking r ate.Under the condition of the same methanol substitution ratio,the engine’s econo my and CO,HC and NOx emissions are better than those of the engine using the original catalyst.