Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

The model reactions of ethylene polymerization and hydrogenolysis of linear alkanes ( propane, n-butane, and n-pentane) on the silica-supported zirconium hydrides (equivalent toSi-O)(3)(ZrH)-H-IV, (equivalent toSi-O)(2)(ZrH2)-H-IV, and (equivalent toSi-O)(2)(ZrH)-H-II were studied using the DFT approach. Catalytic processes under study were shown to occur involving different surface hydrides. The ethylene polymerization was found to proceed at comparable rates on the zirconium monohydrides, (equivalent toSi-O)(3)ZrH, and dihydrides, (equivalent toSi-O)(2)ZrH2. Cleavage of linear alkanes on the monohydrides (equivalent toSi-O)(3)ZrH is thermodynamically unfavorable; however, the dihydrides (equivalent toSi-O)(2)ZrH2 can act as catalysts of the process under mild conditions. Hydrides of the trivalent zirconium, (equivalent toSi-O)(2)(ZrH)-H-III, can also contribute to the hydrogenolysis reaction. A feature of all the systems studied is low regioselectivity of the corresponding processes.