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

Realizingthe potential benefits of nanoscale metal catalysts requireshighly dispersed active sites and control of their local environment.Herein, we develop a catalyst synthesis route for manipulating thelocal environment of highly dispersed metal-active sites via the targeteddeposition of Pd near highly dispersed ZrO x on ZSM-5 zeolite using electrostatic interactions. The formed heteroatomPd-ZrO x in zeolite catalysts is characterizedby scanning transmission electron microscopy (STEM), in situ infrared spectroscopy, temperature-programmed desorption (TPD) ofO(2), and temperature-programmed surface reaction (TPSR)of CH4. The combination of diverse characterization resultsdemonstrates the heteroatom Pd-ZrO x speciesrendering a higher dispersion and lower oxygen coordination of Pdspecies, appropriately tuning the strength of Pd-O bonds, andproviding abundant active oxygen species to accelerate the dissociationof CH4. Therefore, the catalytic performance of Pd speciesis effectively enhanced with the lowest temperature of 90% CH4 conversion decreasing from 390 degrees C (without ZrO x ) to 340 degrees C. Our work provides a strategy ofengineering to anchor highly dispersed noble metal species and regulatethe local environment to tune catalytic properties.