Investigation of highly active Fe-Al-Cu catalysts for water-gas shift reaction

The Fe-Al-Cu formulation was demonstrated to be a highly promising Cr-free WGS catalyst in our previous work. Cu contributes significantly to the activity enhancement as a structural promoter. The extent of Cu’s promotional effect is largely dependent on how Cu is doped into the iron oxide structure during catalyst preparation. In this paper, effects of preparation methods on catalyst activity were investigated. A sol–gel technique was introduced for catalyst synthesis. Catalysts synthesized by a sol–gel technique were compared to those prepared by a 1-step precipitation or a 2-step precipitation–impregnation techniques. Steady state reaction data showed that sol–gel Fe-Al-Cu exhibited a much higher activity than Fe-Al-Cu catalysts prepared with the other two methods and surpassed the commercial catalyst over a wide reaction temperature range. Characterization results indicated that Cu was uniformly distributed in the iron oxide structure for the sol–gel catalysts. A mixture of iron oxide crystal phases were observed for sol–gel Fe-Al-Cu. Sol–gel preparation created a large amount of oxygen vacancies in the structure, which facilitates the redox cycle during the WGS reaction.

Catalysts prepared by a modified sol–gel techniques have shown very different activity and very different pore structure from the catalysts prepared by precipitation or precipitation/impregnation techniques. Figure shows adsorption–desorption isotherms of N2 at 77 K for Fe-Al-Cu catalysts. Filled symbols represent adsorption while open symbols denote desorption.Figure optionsDownload as PowerPoint slide