Remarkable effect of postsynthesis preparation procedures on catalytic properties of Ni-loaded BEA zeolites in hydrodechlorination of 1,2-dichloroethane

Abstract

Ni2.0SiBEA and Ni2.0HAlBEA zeolites were prepared by two different procedures: (i) a two-step postsynthesis method that consist of (1) creation of vacant T-atom sites by dealumination of HAlBEA (Si/Al=17) with nitric acid and then (2) impregnation of as resulting SiBEA (Si/Al>1300) with aqueous nickel nitrate solution and (ii) conventional wet impregnation of HAlBEA (Si/Al=17) respectively. The calcination of Ni2.0SiBEA and Ni2.0HAlBEA at 773K for 3h in air led to the formation of C-Ni2.0SiBEA and C-Ni2.0HAlBEA with appearance, for the former mainly pseudo-tetrahedral Ni(II) incorporated in BEA framework and for the latter, pseudo-tetrahedral and extra-framework octahedral Ni(II) as evidenced by XRD, DR UV–vis and XPS. After reduction at 873K for 3h in flowing 10% H2/Ar, red-C-Ni2.0SiBEA and red-C-Ni2.0HAlBEA were obtained and investigated as the catalysts in hydrodechlorination of 1,2-dichloroethane at 523–543K. The activity of the catalysts carried out at atmospheric pressure depended on the reaction temperature, nature of nickel species present in C-Ni2.0SiBEA and C-Ni2.0HAlBEA, acidity of zeolites, distribution and size of nickel nanoparticles present in red-C-Ni2.0SiBEA and red-C-Ni2.0HAlBEA catalysts. Selectivity to desired product – ethylene was very high for red-C-Ni2.0SiBEA (∼90%) and low for red-C-Ni2.0HAlBEA (maximally 30%). The latter catalyst promoted strongly formation of vinyl chloride (up to ∼70%). We have shown that prepared by two-step postsynthesis procedure red-C-Ni2.0SiBEA was more resistant to sintering during hydrodechlorination of 1,2-dichloroethane than red-C-Ni2.0HAlBEA prepared by conventional wet impregnation.