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

摘要

HA1BEA zeolite is prepared by calcination of parent TEABEA zeolite at 823 K for 3 h in air following ionic exchange with NH4NO3 solution. Ni_xHAlBEA zeolites are prepared by impregnation of HA1BEA with an aqueous solution of Ni(NO3)2, following a drying at 333 K to obtain Ni_xHAlBEA. The calcination of HAlBEA and Ni_xHAlBEA at 773 K for 3 h in air leads to the formation of C-HA1BEA and C-Ni_xHAlBEA 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-HAIBEA and red-C-Ni_xHAlBEA are investigated as the catalysts in dehydrochlorination of 1,2-dichloroethane into vinyl chloride monomer in the presence of hydrogen at 503-523 K. Red-C-HAIBEA and red-C-Ni_(1.0)HAlBEA show an excellent selectivity toward vinyl chloride (~100%). Activity of HA1BEA and Ni_xHAlBEA 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-Ni_xHAlBEA 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-Ni_xHAlBEA deactivation. It is stronger for spent-red-C-Ni_(2.0)HAlBEA with larger nickel particles than for red-C-Ni_(1.0)HAlBEA containing smaller nickel particles (smaller than 5 nm).