Hydrogenation of Toluene on Zirconium-Modified Hexagonal Molecular Sieve Supported Platinum and Palladium Catalysts

Abstract

Hexagonal molecular sieve (HMS) and Zr-HMS materials were synthesized and employed as supports for preparation of hydrogenation catalyst. Supports and catalysts were characterized by using inductively coupled plasma atomic emission spectroscopy, X-ray diffraction, energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), temperature-programmed desorption, Brunauer–Emmett–Teller surface area, and CO chemisorptions techniques. Results from SEM and EDX confirm the hexagonally ordered mesoporous structure and incorporation of Zr into the HMS support, respectively. The detailed kinetic study of hydrogenation of toluene over Pt(0.15wt%)–Pd(0.15wt%)/HMS and Pt(0.15wt%)–Pd(0.15wt%)/Zr-HMS was performed in a continuous-upflow stainless steel catalytic fixed bed reactor at varied weight hourly space velocity (WHSV), hydrogen partial pressure, and temperature. It was observed that toluene conversion was increased on increasing H2 partial pressure and decreased with increasing WHSV. The conversion is dependent on temperature and shows a well-defined maximum. It was found that incorporation of Zr into the HMS structure increased the toluene conversion and reducibility of the catalysts. It was found that Pt(0.15wt%)–Pd(0.15wt%)/Zr-HMS catalysts showed better performance in the hydrogenation of toluene than Pt(0.15wt%)–Pd(0.15wt%)/HMS catalyst.