Facile fabrication, characterization and catalytic activity of a NiMo/Al(2)O(3) nanocatalyst via a solution combustion method used in a low temperature hydrodesulfurization process: the effect of fuel to oxidant ratio

Novel bimetallic NiMo/Al(2)O(3) nanocatalysts were fabricated via a solution combustion method to evaluate the role of fuel to oxidant molar ratios on their structural properties and hydrodesulfurization activity. The citric acid/oxidant ratios of 0.5, 1, 2 and 4 were selected to address the optimum ratio. Characterization results demonstrated that the content of citric acid considerably influenced the morphological and textural properties of the nanocatalysts. Such morphology modification is attributed to the consequent difference of the effluent exhaust gas during combustion. We show that with our method a relatively homogeneous distribution of the active material over the support can be achieved. The obtained data from N(2) adsorption–desorption analysis illustrated that at a fuel/oxidant ratio of 4 the external and surface area were ca. 2.1 and 1.5 times more than the corresponding one in the fuel/oxidant ratio of 0.5, respectively. Furthermore, a higher amount of fuel can improve the catalyst reducibility by decreasing the interaction of metal active phase with the support surface. The catalytic performance of sulfided nanocatalysts is evaluated in a slurry reactor, operated at ambient pressure using high thiophene contamination as a model fuel. The solution combustion synthesis method was able to remove 100% of the sulfur compound in the reaction medium.