Catalytic performance of dealuminated H–Y zeolite supported bimetallic nanocatalysts in Hydroizomerization of n-hexane and n-heptane

摘要

A series of dealuminated Y-zeolites impregnated by 0.5wt% Pt catalysts promoted by different amounts of Ni, Pd or Cr (0.3 and 0.6wt%) were prepared and characterized as hydrocracking catalysts. The physicochemical and structural characterization of the solid catalysts were investigated and reported through N2physisorption, XRD, TGA-DSC, FT-IR and TEM techniques. Solid catalysts surface acidities were investigated through FT-IR spectroscopy aided by pyridine adsorption. The solid catalytic activities were evaluated through hydroconversion of n-hexane and n-heptane employing micro-catalytic pulse technique directly connected to a gas chromatograph analyzer. The thermal stability of the solids was also investigated up to 800°C. Crystallinity studies using the XRD technique of all modified samples proved analogous to the parent Y-zeolite, exhibiting nearly an amorphous and microcrystalline character of the second metal oxides. Disclosure of bimetallic catalysts crystalline characterization, through XRD, was not viable. The nitrogen adsorption–desorption isotherms for all samples concluded type I adsorption isotherms, without any hysteresis loop, indicating that the entire pore system is composed of micropores. TEM micrographs of the solid catalysts demonstrate well-dispersed Pt, Ni and Cr nanoparticles having sizes of 2–4nm and 7–8nm, respectively. The catalytic activity results indicate that the bimetallic (0.5Pt–0.3Cr)/D18H–Y catalyst is the most active towards n-hexane and n-heptane isomerization while (0.5Pt–0.6Ni)/D18H–Y catalyst can be designed as most suitable as a cracking catalyst.