The traditional deposition–precipitation (DP) method is common but not universal in manipulating Au nanoparticles’ spatial locations in propene epoxidation catalysts, especially for hierarchical hydrophilic TS-1 supports. Directional loading of Au nanoparticles to hierarchical hydrophilic TS-1 pores is challenging because the strong hydrophilicity of the hierarchical TS-1 zeolite would make Au nanoparticles loaded by the DP method tend to be deposited on the hydrophilic support surface, thus blocking the pore mouths and leading to deactivation. Therefore, manipulating Au nanoparticles’ spatial locations on hierarchical hydrophilic TS-1 supports is of great significance to enhance the catalytic performance but is a bottleneck problem. In this work, taking hierarchical hydrophilic HTS-1 supports as an example, we propose a new modified isometric impregnation (NIMG) method to manipulate the spatial location of Au nanoparticles. Moreover, the Au spatial location inside HTS-1 pores is quantitatively reflected by introducing the V na parameter. Combined with the N2 physisorption, high-angle annular dark-field scanning transmission electron microscopy, inductively coupled plasma, and X-ray photoelectron spectroscopy, it is found that the Au nanoparticles loaded by the NIMG method tend to be uniformly distributed inside the pores of HTS-1 due to the capillary effect. As expected, the Au/HTS-1­(NIMG) catalyst (with the Au nanoparticles inside the pores) exhibits a much higher propylene oxide (PO) formation rate, PO selectivity, and H2 efficiency than the Au/HTS-1­(DP) catalyst (with the Au nanoparticles on the outer surface). This is possibly because loading Au nanoparticles inside the pores is conducive to the transfer of H2O2 from Au to the nearby abundant Ti active sites, thus weakening the decomposition of H2O2 to H2O, avoiding the ring-opening side reactions, and promoting propene epoxidation into PO. This work sheds new light for controlling the spatial location of Au in hierarchically structured hydrophilic catalysts for direct propene epoxidation.

A series of alkali metal (Li, Na, and K)-modified Pd catalysts and Pd/Al2O3 were prepared and used to remove oxygen in a propylene flow with hydrogen’s existence. The results showed that the alkali metals could enhance the performance of the Pd catalysts and the effect followed the order of K > Na > Li. X-Ray diffraction (XRD), N2-physisorption, transmission electron microscopy (TEM), hydrogen temperature programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS) were carried out to investigate the alkali metal-modified Pd catalysts and the promotional effect mechanism was explained. The results showed that alkali metal modification increased the electron density of Pd atoms to induce the negatively charged Pd species, which could enhance the adsorption of oxygen while weakening the adsorption of propylene, and then enhance the performance of the modified catalysts for oxygen removal from unsaturated hydrocarbon. The Pd-K/A catalyst performed the best on both oxygen removal and propylene hydrogenation inhibition.

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Synthesis of zeolites in more efficient and greener methods is of great significance in both industrial and academic fields. However, the relative long time for zeolite crystallization and much consumption of water solvent make the target challengeable. Herein, a route for ultrafast synthesis of nano Silicalite-1 zeolites in 10 min with much less water consumption has been developed. Comprehensive characterizations, i.e., X-ray powder diffraction, N2 sorption, scanning electron microscope, and NMR, confirm the high quality of such obtained Silicalite-1 zeolites. In the catalytic deoxygenation of O2-containing ethylene (mixture of O2 and ethylene), these reported Silicalite-1 zeolite samples show the comparable performance with the conventional Silicalite-1 zeolites synthesized under hydrothermal conditions. This research therefore provides a new trial toward the ultrafast synthesis of zeolite materials in an environment-friendly route.