Synthesis of Heteroatom Pd-ZrOx Species on Zeolite for Complete Methane Oxidation

Abstract

Realizing the potential benefits of nanoscale metal catalysts requires highly dispersed active sites and control of their local environment. Herein, we develop a catalyst synthesis route for manipulating the local environment of highly dispersed metal-active sites via the targeted deposition of Pd near highly dispersed ZrOx on ZSM-5 zeolite using electrostatic interactions. The formed heteroatom Pd-ZrOx in zeolite catalysts is characterized by scanning transmission electron microscopy (STEM), in situ infrared spectroscopy, temperature-programmed desorption (TPD) of O2, and temperature-programmed surface reaction (TPSR) of CH4. The combination of diverse characterization results demonstrates the heteroatom Pd-ZrOx species rendering a higher dispersion and lower oxygen coordination of Pd species, appropriately tuning the strength of Pd–O bonds, and providing abundant active oxygen species to accelerate the dissociation of CH4. Therefore, the catalytic performance of Pd species is effectively enhanced with the lowest temperature of 90% CH4 conversion decreasing from 390 °C (without ZrOx) to 340 °C. Our work provides a strategy of engineering to anchor highly dispersed noble metal species and regulate the local environment to tune catalytic properties.