Catalytic activity of HAlBEA and NixHAlBEA zeolites in hydrogen-assisted dehydrochlorination of 1,2-dichloroethane into vinyl chloride monomer

Abstract

HAlBEA zeolite is prepared by calcination of parent TEABEA zeolite at 823K for 3h in air following ionic exchange with NH4NO3 solution. NixHAlBEA zeolites are prepared by impregnation of HAlBEA with an aqueous solution of Ni(NO3)2, following a drying at 333K to obtain NixHAlBEA. The calcination of HAlBEA and NixHAlBEA at 773K for 3h in air leads to the formation of C-HAlBEA and C–NixHAlBEA with appeared, for the latter, an octahedral and tetrahedral Ni(II) species incorporated in BEA framework as evidenced by XRD, DR UV–vis and XPS. Red-C-HAlBEA and red-C–NixHAlBEA are investigated as the catalysts in dehydrochlorination of 1,2-dichloroethane into vinyl chloride monomer in the presence of hydrogen at 503–523K. Red-C-HAlBEA and red-C–Ni1.0HAlBEA show an excellent selectivity toward vinyl chloride (∼100%). Activity of HAlBEA and NixHAlBEA in the catalytic conversion of 1,2-dichloroethane strongly depends on the acidic properties of these materials and for the latter the catalytic activity depend on metal dispersion. The small Ni particles favor the dehydrochlorination of 1,2-dichloroethane to vinyl chloride. With increasing nickel particles size decreases activity of the red-C–NixHAlBEA catalysts. For these catalysts after kinetic run sintering of nickel phase is observed. Besides of carburization the nickel sintering is the main cause of red-C–NixHAlBEA deactivation. It is stronger for spent-red-C–Ni2.0HAlBEA with larger nickel particles than for red-C–Ni1.0HAlBEA containing smaller nickel particles (smaller than 5nm).