Preparation And Study Of Metallic Monolithic Catalysts For Preferential CO Oxidation In Excess Hydrogen

Hydrogen production from methanol reforming of hydrocarbons and water gas shift reaction is one of the most promising approaches for proton exchange membrane fuel cells (PEMFC). The so produced gases mixture typically contain l % CO which poisons the noble metal anode of fuel cells dramatically. Among the CO removing methods reported, the preferential oxidation of CO (CO-PROX) appears to be the simplest and the most cost-efficient and effective method for CO removing. It is reported that noble catalyst is the most potential catalyst for CO-PROX in hydrogen rich-gases. Due to the high cost and limited reverses, it is necessary to decrease its content in the catalysts. On the other hand, the metallic honeycomb support with micro-channel not only can improve the mechanical strength of the catalyst, but can compact the reactor volume. For the reasons mentioned above, this paper focuses on the low content Pt monolith catalysts for CO-PROX. The main investigations of this research are as follows:Firstly, the adhesion of Al₂O₃ washcoat has been studied. The results indicate that the bond-boehmite play an important role in the improvement of the washcoat adhesion. Moreover, some factors which influence the adhesion and loading of the washcoat have been investigated. The results indicate that an adhesive washcoat could be obtained when the solid content is 30%, the slurry pH is 4 and the CeZr solid solution was added in the slurry.Secondly, four different methods of loading the catalysts onto the monolithic supports were investigated, including: impregnation, dip-coating, combustion and microemulsion method. The results indicate that the monolithic catalysts with the supporting impregnation and dip-coating methods have good performances, especially the 1%Pt-Ni/Al₂O₃ monolithic catalyst using impregnation method: in the gas of 1%CO,1%O₂,50%H₂,N2 balance, at the space velocity of 2100 h-1 , the CO conversion is 97.5% at 40℃, which greatly improves the CO removing effect at low temperature.Finally, due to the excellent performance of the impregnation 1%Pt-Ni/Al₂O₃ monolithic catalyst, the resistant performance of CO₂ and H₂O was tested. The CO conversion decreased after adding CO₂ and/or H₂O to some extent. Also, in the experiment of optimizing the 1%Pt-Ni/Al₂O₃ preparation conditions, we find that when 1%Pt-Ni/Al₂O₃ catalyst was calcined at 500℃and reduced at 300℃, CO was totally converted to CO₂ at 75℃and the total oxidation temperature range is about 100℃.