Corundum Impregnation Conditions for Preparing Supported Ni Catalysts for the Synthesis of a Uniform Layer of Carbon Nanofibers

摘要

Impregnation techniques for corundum (S (BET) = 0.5 m(2)/g) as a support for Ni catalysts for C-3-C-4 alkane pyrolysis into catalytic filamentous carbon (CFC) are compared. The effects of the following factors on the uniformity of the active component (Ni) deposition on the inert support and on the CFC yield (g CFC)/(g Ni) are reported: (1) pH of the nickel nitrate solution, (2) presence of aluminum(III) nitrate in the solution, (3) addition of viscosifying agents (glycerol, glucose, sucrose) to the solution, (4) catalyst calcination conditions before pyrolysis, and (5) catalyst drying technique. The surface morphology of the Ni catalysts and of the carbon deposits resulting from the catalytic pyrolysis of C-3-C-4 alkanes in the presence of hydrogen has been investigated by scanning electron microscopy. The optimum way of preparing the supported Ni catalysts is by carrying out the incipient wetness impregnation of corundum with a nickel nitrate solution (0.05-0.1 mol/l) containing glycerol (20-25 vol %), drying the product in a microwave oven, and burning away the glycerol before alkane pyrolysis.