Pd/silicalite-1: An highly active catalyst for the oxidative removal of toluene.

Catalytic combustion is thought as an efficient and economic pathway to remove volatile organic compounds, and its critical issue is the development of high-performance catalytic materials. In this work, we used the in situ synthesis method to prepare the silicalite-1 (S-1)-supported Pd nanoparticles (NPs). It is found that the as-prepared catalysts displayed a hexagonal prism morphology and a surface area of 390-440 m2/g. The sample (0.28Pd/S-1-H) derived after reduction at 500°C in 10 vol% H2 showed the best catalytic activity for toluene combustion (T50% = 180°C and T90% = 189°C at a space velocity of 40,000 mL/(g·hr), turnover frequency (TOFPd) at 160°C = 3.46 × 10-3 sec-1, and specific reaction rate at 160°C = 63.8 µmol/(gPd·sec)), with the apparent activation energy (41 kJ/mol) obtained over the best-performing 0.28Pd/S-1-H sample being much lower than those (51-70 kJ/mol) obtained over the other samples (0.28Pd/S-1-A derived from calcination at 500°C in air, 0.26Pd/S-1-im derived from the impregnation route, and 0.27Pd/ZSM-5-H prepared after reduction at 500°C in 10 vol% H2). Furthermore, the 0.28Pd/S-1-H sample possessed good thermal stability and its partial deactivation due to CO2 or H2O introduction was reversible, but SO2 addition resulted in an irreversible deactivation. The possible pathways of toluene oxidation over 0.28Pd/S-1-H was toluene â†’ p-methylbenzoquinone â†’ maleic anhydride, benzoic acid, benzaldehyde â†’ carbon dioxide and water. We conclude that the good dispersion of Pd NPs, high adsorption oxygen species concentration, large toluene adsorption capacity, strong acidity, and more Pd0 species were responsible for the good catalytic performance of 0.28Pd/S-1-H.

Stable and Versatile Pd Precursors for the Preparation of Robust Pd Catalysts under Continuous-Flow.

The chemical and engineering communities require the development of versatile precursors that can be used to synthesize robust catalysts to achieve global sustainability. To meet this demand, we developed a new Pd precursor for incorporating fine Pd metal into supports in a highly efficient manner. An atmospherically stable Pd precursor (Pd-80) was prepared by the thermally promoted aerobic oxidation of tetrakis(triphenylphosphine)palladium. The physical properties of Pd-80 were investigated using NMR spectroscopy, SEM, XPS, solvent-relaxation NMR spectroscopy, and dynamic light scattering (DLS) experiments. We also prepared a cordierite-supported Pd catalyst (Pd/cordierite) by stirring Pd-80 and cordierite powder in chloroform at room temperature. Pd/cordierite selectively catalyzes the hydrogenation of various reducible functional groups, including alkynes, azides, nitro groups, olefins, CO2Bn, N-Cbz, O-Bn, aromatic ketones, and styrene oxide, in continuous-flow hydrogenation reactions. The Pd/cordierite-catalyzed continuous-flow hydrogenation of nitrobenzene derivatives afforded the corresponding anilines, with catalyst activity maintained for over 250 h of continuous operation and a turnover number (TON) of 61,090 recorded.

Chitosan derived efficient and stable Pd nano-catalyst for high efficiency hydrogenation.

The design and development of green and efficient supported catalysts is the frontier direction in the field of green synthesis, which conforms to the strategic concept of green sustainable chemistry and "carbon neutrality". Herein, we used a renewable resource chitosan (CS) derived from seafood wastes of chitin as carriers to design two different chitosan-supported palladium (Pd) nano-catalysts through different activation methods. The Pd particles were firmly and uniformly dispersed on the chitosan microspheres due to the interconnected nanoporous structure and functional groups of chitosan, proved by diverse characterizations. The chitosan supported catalysts (Pd@CS) was applied to hydrogenation of 4-nitrophenol, which showed competitive catalytic activity compared to commercial Pd/C, un-supported nano-Pd and Pd(OAc)2 catalysts, as well as excellent catalytic activity, good reusability, long-life and broad applicability in selective hydrogenation of aromatic aldehydes, suggesting potential of applications in green industrial catalysis.