Base Metal Nano Catalysts Supported On Oxides For Steam Reforming Of Ethanol To Produce Hydrogen

The critical challenge for steam reforming of ethanol(SRE) is to develop qualified catalysts. The reported catalysts have been proved to be active for SRE. Recently, researchers focus on the improvement on catalyst stability, carbon deposition and sintering of active metal particles are the main reasons for the deactivation of the catalysts. In our work, two approaches were proposed to improve the stability of catalysts: one was to choose oxides with abundant oxygen vacancies as catalyst carriers and the other was to prepare supported bimetallic catalysts, the structure and performance of catalysts for SRE were investigated.Firstly, two schemes for design and preparation of Ni-La-Ce oxide catalysts were proposed. Citrate complexing and modified impregnation method were used to prepare catalysts and the results indicated that the preparation methods had a significant influence on the structure of catalysts. Both of the catalysts exhibited very good performance for SRE. The catalyst made according to citrate complexing method kept stable which was tested at 650 °C and a high space velocity of 180,000 ml·gcat-1·h-1 with reaction mixture of H2O/C2H5 OH = 3 in mole ratio, the abundant oxygen vacancies in the catalyst led to the superior stability.Then the perovskites of LaCoxNi1-xO3 was used as precursors to prepare supported bimetallic catalysts. The cobalt and nickel ions in LaCoxNi1-xO3 were reduced simultaneously, and the results of XRD, TPR and TEM revealed that nanoparticles of Ni-Co solid solution alloy were obtained after reduction treatment. It was deduced that varied bimetallic or polymetallic nanoparticles derived from perovskite precursors would be produced as a lot of metal ions can enter into perovskite lattice. Compared with the reported catalysts in literatures, the resultant catalysts of Ni-Co alloy supported on La2O3 presented high activity and good stability for SRE. After 10 hours’ running at the relatively low reaction temperature of 550 °C, Co-rich catalysts showed some deactivation. The cobalt sites in the catalysts were inclined to form amorphous carbon, while the nickel sites tended to generate filamentous carbon, and the former led to more severe deactivation. At the relatively high reaction temperature of 700 ° C, the resultant catalysts presented good stability and the bimetallic alloy catalysts presented better anti-sintering ability than the monometal catalysts.Finally, the precursors of CuO/LaNiO3 and CuO/LaCoO3 were prepared by citrate complexing method and supported Cu-Ni and Cu-Co catalysts were prepared by reducing the perovskite precursors. As for the perovskite precursors, CuO particles were highly dispersed on perovskite-type oxides and reduced to form Cu at low reduction temperature. While the metallic ions in PTOs were transferred into metal at higher reduction temperature as the perovskite structure restrained the reduction of metallic ion. The generated metal nickel or cobalt was covered on the surface of metal copper particles due to differnet reduction performance of copper ions and nickel(cobalt) ions, and the particles with core-shell structure were obtained. The resultant samples presented good catalytic performance for steam reforming of ethanol to produce hydrogen.