Home – Home – Jornals – Chemistry for Sustainable Development 2019 number 1

The mechanical treatment of zeolites in mills of various types is a promising modification method not requiring complex instrumentation and not yielding harmful waste water. In addition, dry mixing is the only method that allows introducing nanoscale metal powders into the zeolite structure without changing their properties. The proposed work prepared nickel-containing zeolite samples by the dry mechanical mixing of ZSM-5 zeolite with silicate modulus 40 and nickel powder with an average particle size of 50 nm per 0.5 mass %. They were exposed to mechanical treatment in a vibratory ball mill for 24–120 h. In order to retain properties of Ni nanopowder and avoid nickel oxidation, the resulting catalysts were not calcined. The degree of crystallinity of the initial zeolite and its mechanically treated modifications was determined by IR spectroscopy and X-ray structural analysis. Acidic properties of the catalysts were explored by ammonia thermoprogrammed desorption enabling to determine the distribution of acid sites according to strength, and also their number. Changing the catalytic activity and the selectivity of the initial zeolite and mechanically treated nickel-containing samples was explored in the model reaction of n-hexane transformation. As shown, the preliminary mechanical treatment of Ni/ZSM-5 reduces its crystallinity degree, and also acid sites strength and concentration. The variation of mechanical treatment time may directionally change the catalytic reaction pathway, as established. That allows an increase in the yield of the catalysate with improved environmental characteristics resulting from a decrease in the contents of n-alkanes, aromatic hydrocarbons, and alkenes, and also from a simultaneous increase in the fraction of iso- and cyclo-alkanes therein.