A study of Ni–Al–O mixed oxides as catalysts for the oxidative conversion of ethane to ethylene

TLDR: In this article, a series of Ni-Al-O mixed oxides with different aluminum content were synthesized via a facile co-evaporation route and tested in ethane oxidative dehydrogenation.

Abstract: A series of Ni–Al–O mixed oxides with different aluminum content ranging from 1% to 50% (metal atomic content) were synthesized via a facile co-evaporation route and tested in ethane oxidative dehydrogenation. In samples with Al loading up to 30%, the crystal structure of NiO is retained and the interaction between nickel oxide and alumina leads to smaller crystal sizes, higher surface areas and decreased reducibility, along with a gradual decrease in the amount of desorbed oxygen observed by O 2 -TPD measurements. At higher aluminum loadings the formation of an amorphous spinel-like precursor phase is evidenced. Correlation between the catalytic performance of Ni–Al–O mixed oxide and their oxygen desorption properties showed that as the excess oxygen per catalyst surface area decreases, the catalysts become less active in the activation of ethane, but more selective toward ethylene. The catalyst containing 30% aluminum represents the optimum composition among Ni–Al–O mixed oxides studied in this work. Further optimization of the catalyst preparation method with the use of an organic aluminum precursor led to the development of a catalyst presenting up to 85% selectivity toward ethylene. The enhanced performance of this material was correlated with the further reduction of catalyst over-stoichiometry and oxygen lability induced by the organic precursor, according to O 2 -TPD and isotopic oxygen exchange experiments respectively.