How nitric oxide affects the decomposition of supported nickel nitrate to arrive at highly dispersed catalysts

An explanation is put forward for the beneficial effect of thermal decomposition of supported Ni-3(NO3)(2)(OH)(4) in NO/He flow (0.1-1 vol%) that enables preparation of well-dispersed (3-5 nm particles) 24 wt% Ni-catalysts via impregnation and drying using aqueous [Ni(OH2)(6)](NO3)(2) precursor solution. Moreover, combining electron tomography, XRD and N-2-physisorption with SBA-15 support yielded a clear picture of the impact of air, He and NO/He gas atmospheres on NiO shape and distribution. TGA/MS indicated that NO2, N2O, H2O products evolved more gradually in NO/He. In situ XRD and DSC revealed that NO lowers the nitrate decomposition rate and appears less endothermic than in air supposedly due to exothermic scavenging of oxygen by NO, which is supported by MS results. The Ni/SiO2 catalyst prepared via the NO-method displayed a higher activity in the hydrogenation of soybean oil as the required hydrogenation time decreased by 30% compared to the traditionally air calcined catalyst. (C) 2008 Elsevier Inc. All rights reserved.