The origin of extraordinary selectivity in dehydrogenation of methylcyclohexane over Ni-Sn-based catalysts

[Display omitted] •Ni-Sn catalysts with superior selectivity were created for LOHCs hydrogen evolution;•They are based on high-loaded nickel catalyst formulation;•Optimal catalyst has atomic ratio of Ni:Sn of 5:1 and is reduced at 500 °C;•Dehydrogenation selectivity reached over 99 % at MCH conversion of 92 %;•High selectivity of the Ni-Sn catalysts is due to formation of NiSn solid solutions. High-loaded nickel catalysts (HLNCs) modified with Sn were synthesized and tested in dehydrogenation of methylcyclohexane (MCH) as a liquid organic hydrogen carrier. The catalyst composition and its reduction temperature were optimized that enabled to achieve the dehydrogenation selectivity of 99.0 % at a MCH conversion of 92 % and WHSV of 6.0 h−1, while the 99.9 % selectivity was reached at the conversion of 60.4 %, and WHSV of 18.5 h−1. Further, stability of the high selectivity of Sn-modified HLNCs was demonstrated in the long-run (100 h) catalyst test. The genesis of the HLNCs during their modification with Sn and reductive activation in hydrogen was studied. It was shown that the activation at temperatures above 450 °C resulted in a uniform distribution of Sn with the predominant formation of solid NiSn solutions having a crystal lattice of metallic nickel. The formation of the solid solutions provided a decrease in the adsorptive properties relating to the reaction product, toluene, which, in turn, led to an increase in the selectivity of MCH dehydrogenation.