| Environmental issues caused by the use of energy resources had attracted people’s attention to carbon free alternative energy carriers.Hydrogen become a research hotspot due to its advantages such as high calorific value and low pollution.However,it is difficult to store and transport hydrogen.Among the existing hydrogen production methods,methanol steam reforming(SRM)is the most commonly used method for on-site hydrogen production.It has the advantages of low reaction temperature,high H2 selectivity,better water solubility of raw materials and high hydrogen loading capacity.Moreover,combined with fuel cells,it has characteristics of pollution-free and high efficiency.At present,industrial catalysts have high methanol conversion rates,but there were problems such as low H2 production,high CO content,and easy poisoning of fuel cells.Researchers have found that CeO2 has good oxygen storage and release functions,which can effectively reduce CO content.However,its thermal stability is poor,and the catalytic performance of CuO/CeO2 still needs to be improved.In this paper,the shortcomings of CuO/CeO2 catalysts were modified and applied to the methanol steam reforming(SRM)reaction system to improve the catalytic activity and stability of the catalyst.The main content is as follows:The support of CeMO2(M=Zr,Mn,Fe and Cr)was prepared by coprecipitation method.CuO/CeMO2 catalyst was obtained by depositation-precipitation method supported by CuO.Among them,Zr and Mn doped catalysts have the best activity,but CuO/CeMnO2 catalyst has poor stability.The methanol conversion rate of CuO/CeZrO2 catalyst reached 90%and the hydrogen production rate was 95 mL·g1·min-1 at the reaction temperature of 250℃,the water-alcohol ratio of 1.3 and space velocity of 2400 h1.XRD,H2-TPR and XPS showed that doping transition metals Zr and Mn in CeO2 carrier increased the specific surface area and dispersion of Cu,and the oxygen vacancy increased.At the same time,the interaction between CuO and CeO2 was strengthened,and the catalytic activity of the catalyst was improved.However,the addition of Fe and Cr reduced the specific surface area,reduced the oxygen vacancy,weakened the Cu-Ce interaction,and could not improve the catalytic activity.Effect of precipitation temperature on catalytic activity of CuO/CeZrO2 for methanol steam reforming to produce hydrogen were investigated.The precipitation temperature was 70℃,and CuO/CeZrO2 had the best activity.At 250℃,a water alcohol ratio of 1.3,and a space velocity of 2400 h-1,Methanol conversion rate reached 94%,and hydrogen production rate were 96 ML·g-1·min-1.Combined with XRD,H2-TPR and XPS characterization,found that the precipitation temperature effected on the crystallinity,specific surface area,dispersity and oxygen vacancy content of the catalyst.CuO/CeZrO2 catalyst prepared at temperature of 70℃ had large specific surface area,dispersity and rich oxygen vacancies.Interaction between CuO and CeO2 was strengthened,which makes it have a better methanol conversion and hydrogen production rate.Exploring the effect of CuO loading on catalytic activity of catalysts,the optimal CuO loading was 20%.At 250℃,a water alcohol ratio of 1.3,and a space velocity of 2400 h-1,methanol conversion rate of 20%CuO/CeZrO2 reached 97%,and hydrogen production 107 mL·g-1·min-1.Through characterization and catalytic evaluation,found that 20%CuO/CeZrO2 had smallest metal microcrystal size,highest surface area,best dispersion and rich oxygen vacancies content.Interaction between CeZrO2 carrier and CuO were stronger.The life test showed that the catalyst had better stability. |
