The Comparative Effect of Particle Size and Support Acidity on Hydrogenation of Aromatic Ketones

Mesoporous molecular sieve-based materials for catalytic oxidation of VOC: A review

As the main contributor of the formation of particulate matter as well as ozone, volatile organic compounds (VOCs) greatly affect human health and the environmental quality. Catalytic combustion/oxidation has been viewed as an efficient, economically feasible and environmentally friendly way for the elimination of VOCs. Supported metal catalyst is the preferred type of catalysts applied for VOCs catalytic combustion because of the synergy between active components and support as well as its flexibility in the composition. The presence of support not only plays the role of keeping the catalyst with good stability and mechanical strength, but also provides a large specific surface for the good dispersion of active components, which could effectively improve the performance of catalyst as well as decrease the usage of active components, especially the noble metal amount. Mesoporous molecular sieves, owing to their large surface area, unique porous structures, large pore size as well as uniform pore-size distribution, were viewed as superior support for dispersing active components. This review focuses on the recent development of mesoporous molecular sieve supported metal catalysts and their application in catalytic oxidation of VOCs. The effect of active component types, support structure, preparation method, precursors, etc. on the valence state, dispersion as well as the loading of active species were also discussed and summarized. Moreover, the corresponding conversion route of VOCs was also addressed. This review aims to provide some enlightment for designing the supported metal catalysts with superior activity and stability for VOCs removal.

Ni@C Catalyzed Hydrogenation of Acetophenone to Phenylethanol under Industrial Mild Conditions in Flow Reactor

The catalytic hydrogenation of organic substrates containing plenty of unsaturated functional groups is an important step in the industrial preparation of fine chemicals and has always been a hot spot...

Formation and Location of Pt Single Sites Induced by Pentacoordinated Al Species on Amorphous Silica-Alumina

Alumina and its mixed oxides are popular industrial supports for emerging supported metal catalysts. Pentacoordinated Al (Al^V) species are identified as key surface sites for anchoring and stabilizing metal single-site catalysts; however, Al^V is rare in conventional amorphous silica-alumina (ASA). Recently, we have developed Al^V-enriched ASA, which was applied as a support for the synthesis of Pt single-site catalysts in this work. Each preparation stage and the interaction between Pt and surface Al species were explored by ¹H and ²⁷Al solid-state nuclear magnetic resonance spectroscopy, and the formation of the dominant Pt single sites on the surface of Al^V-enriched ASA was confirmed by high-angle annular dark-field imaging scanning transmission electron microscopy and energy dispersive spectroscopy line scanning. On the surface of supports without a significant Al^V population (Pt/Al₂O₃ and Pt/SiO₂), mainly Pt nanoparticles were formed. This indicates that Al^V contributes to the strong metal-support interaction to stabilize the Pt single sites on Pt/ASA, which was characterized by diffuse reflectance infrared Fourier transform spectroscopy combined with CO adsorption, X-ray photoelectron spectroscopy, and electron energy loss spectroscopy. Pt single sites supported on Al^V-enriched ASA exhibit excellent chemoselectivity in the hydrogenation of C═O groups, affording 2-3-fold higher yields compared to those of Pt nanoparticles supported on Al₂O₃ and SiO₂.

Selective Hydrogenation of Cinnamaldehyde over the Stepped and Plane Surface of Pd Nanoparticles with Controlled Morphologies by CO Chemisorption

Carbon monoxide (CO) molecules are attracting attention as capping agents that control the structure of metal nanoparticles. In this study, we aimed to control the shape and surface structure of Pd particles by reducing the supported Pd precursor with CO. The reduction of Pd nanoparticles with CO promoted the exposure of step sites and generated spherical and concave-tetrahedral Pd particles on carbon and SiO₂ supports. On the other hand, conventional H₂-reduced Pd particles show a flattened shape. The preferential exposure of the step sites by the adsorbed CO molecules was supported by the density functional theory-calculated surface energy and the Wulff construction. Morphology- and surface-controlled Pd nanoparticles were used to study the surface structure and morphology effects of Pd nanoparticles on cinnamaldehyde (CAL) hydrogenation. With an increase in the fraction of step sites on Pd nanoparticles, the hydrogenation activity and selectivity of hydrocinnamaldehyde (HCAL) increased. On step sites, the adsorption of the C═C bond of CAL proceeded preferentially, and HCAL was efficiently and selectively generated.