Synthesis and Characterization of Ni/Mo Nanocatalysts on Alumina and Zeolite Supports

A series of nickel/molybdenum bimetallic nanocatalysts were prepared by wet impregnation method on USY  zeolite and alumina as support. The catalysts were characterized by nitrogen-sorption (for Brauneur-Emmet-Teller,  BET surface area determination), X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Scanning  Electron Microscopy-Electron Dispersive X-ray Spectroscopy (SEM-EDX) , Transmission Electron Microscopy  (TEM) and Temperature Programmed Reduction (TPR). The results of nitrogen sorption reveal a reduction of BET  surface area of about 40% for nanocatalyst on alumina and zeolite. With the increase of zeolite content of our  catalyst, the micropore volume and surface area increased while the average pore size decreased. Hence, as the  micropores increased the mesopores and macropores decreased. The SEM surface morphologies of the catalysts  confirmed that deposition of metals occurs in the pores and on the surface of the catalysts which have contributed to  reduction in the surface area as indicated in the BET result. The EDX revealed the deposition of metals onto the  surfaces. The presence of Al and Si in the support and Ni and Mo as active metals was confirmed. The TEM  displayed a homogeneous dispersion of metals on the supports. The micrograph showed a worm-like motif with a  random channel system which matches the plate-like particles assembled in parallel identified by the N-2  adsorption-desorption isotherm. However, the catalysts had darker coloration as the percentage of the zeolite was  increased on the support due to the coating of pores with the metals which had better interactions as corroborated by  the TPR profiles. The results of TPR showed that the weaker interaction between the Mo and Ni species and the  support leads to better reducibility of the metal oxides on zeolite than on alumina. As the zeolite content of the  mixed support was increased, the peak mainly due to the reduction of Mo became weaker, hence the reducibility of  metal precursor on the support varies with different zeolite content.