Toluene hydrogenation on bimetallic palladium/platinum catalysts supported on zeolite beta synthesized with rice husk silica

摘要

Zeolite beta in proton form (HBEA) was synthesized with rice husk silica and employed as a support for mono- and bimetallic catalysts containing Pd and/or Pt. The metal was deposited to HBEA by impregnation with Pd(acac)2 and/or H2Pt(NH3)4; and the quantities of each metal was 3 wt%. Results from X-ray diffraction indicated that the structure of HBEA did not change after impregnated with the metal. Results from nitrogen adsorption indicated that the HBEA surface area did not change after impregnation implying good dispersion of metal. The total catalyst acidity determined by temperature-programmed desorption of ammonia was consistent with the surface area. The positions of metal were likely on strong acid sites of HBEA as observed by a decrease of ammonia desorption at high temperature with high Pt content. Both monometallic and bimetallic catalysts were tested for gas-phase toluene hydrogenation in a tubular flow reactor from 30 to 300℃ and products were analyzed by an online gas chromatograph. The temperature that the bimetallic gave both high toluene conversion and high selectivity for methylcyclohexane was from 100 to 200℃. At these temperatures, catalyst deactivation was not observed during the testing period of six hours.