Direct low-temperature hydrothermal synthesis of uniform Pd nanoparticles encapsulated mesoporous TS-1 and its excellent catalytic capability.

Abstract A simple and direct low-temperature hydrothermal synthesis approach (100 °C) has been developed to encapsulate Pd nanoparticles (ca. 2.3 nm) within nano-sized mesoporous TS-1 zeolite by utilizing dichloro(ethylenediamine)palladium (DEAP) and cetyltrimethylammonium bromide (CTAB) as palladium source and mesoporogen, respectively. It's demonstrated that the aging process of the mother liquid and low-temperature hydrothermal treatment can effectively inhibit the premature precipitation of metal precursor and thus the successful encapsulation of Pd nanoparticles into mesoporous TS-1 nanocrystals, so that the frequently occurring of Pd nanoparticle aggregation at high temperature was expectedly avoided. Consequently, the as-synthesized catalysts with highly thermal stability and mesoporous channels exhibit excellent catalytic activity and recyclability in the oxidation of CO with relatively low Pd content (0.53 wt% Pd) and catalytic wet air oxidation of phenol (66.2% of phenol conversion, 100 °C). Graphical abstract Image 1 Highlights • We report a direct synthesis of Pd encapsulated mesoporous TS-1 zeolite via low-temperature hydrothermal treatment. • The optimized synthesis condition (mesoporogen amount, temperature and time of hydrothermal treatment) are studied. • The small-sized Pd nanoparticles (2.3 nm) in mesoporous TS-1 show high stability at 600 °C under air/N 2 /H 2 atomsphere. • The hierarchical micro/mesoporous stucture endow the nano-sized TS-1 zeolite high mass transportation efficiency. • Excellent catalytic activities and recyclabilities of catalyst in the CO oxidation and wet air oxidation of phenol. [ABSTRACT FROM AUTHOR]