N-Butane dehydrogenation over Ni-Sn/SiO2: Adsorption modes and reaction paths of n-butane and 1-butene

Abstract

Compared with i-butane dehydrogenation over Ni-Sn/SiO2 catalyst, the conversion is higher for n-butane dehydrogenation, the selectivity to butenes is obviously lower, and the catalyst deactivates more rapidly. In order to clarify the difference, adsorption modes of n-butane and 1-butene along with desorption activation energy of 1-butene were determined by in-situ FTIR and TPD. n-Butane is adsorbed on Ni-Sn surface with a H atom in methyl, and the formed intermediates are prone to the rupture of CC bonds, leading to the lower selectivity to butenes. In addition, secondary reactions of butenes also play an important role in decreased selectivity, but to a less extent due to the medium desorption activation of butenes (58 kJ mol−1 for 1-butene, for example). The generation of coke is the third reason for lower selectivity. The rapid deactivation of Ni-Sn/SiO2 catalyst mainly results from the formation of 1,3-butadiene, coke precursor, by further dehydrogenation of butenes.