Synthesis of catalytic materials based on system Ni/alfa-Al2O3 suported on monolith ceramic foams

Abstract

In the present investigation, nanostructured Ni/Al2O3 catalyst supported on reticulated alumina-mullite foam was synthesized by aerosol assisted coating. The synthesis process was optimized from the technological and economic aspect. Ultrasonically generated NiCl2 water solutions were applied to α-Al2O3-mullite foam in a tubular quartz reactor. The first procedure involved calcination at 773 K for 1 h in order to obtain NiO/Al2O3 precursor. The second procedure involved drying at 473 K for 1 h without oxidation. The activation step involved hydrogen reduction at 633 K. The effectiveness of the low-temperature hydrogen reduction was compared for those systems. It was determined that the samples were reduced in a high degree at 633 K for 90 minutes and the hydrogen flow rate of 20L/h. However, SEM of calcined sample shows presence of agglomerates. The samples reduced from NiCl2 had no agglomerates and the metallic phase was homogeneously dispersed compared to the samples obtained by NiO reduction. The most probable reason for the effective low-temperature reduction was the formation of thin coatings consisted of oxide and chloride precursors for the catalytically active components. XRD analyse of the samples after the reduction at 633 K for 90 minutes showed only metallic nickel, alumina and mullite phases. Residual phases of NiO and NiCl2, as well as NiAl2O4, were not detected. The production process can be simplified and economically more favourable by avoiding the calcination step.