Palladium Intercalated into the Walls of Mesoporous Silica as Robust and Regenerable Catalysts for Hydrodeoxygenation of Phenolic Compounds

Abstract

Nanostructured noble-metal catalysts traditionally suffer from sintering under high operating temperatures, leading to durability issues and process limitations. The encapsulation of nanostructured catalysts to prevent loss of activity through thermal sintering, while maintaining accessibility of active sites, remains a great challenge in the catalysis community. Here, we report a robust and regenerable palladium-based catalyst, wherein palladium particles are intercalated into the three-dimensional framework of SBA-15-type mesoporous silica. The encapsulated Pd active sites remain catalytically active as demonstrated in high-temperature/pressure phenol hydrodeoxygenation reactions. The confinement of Pd particles in the walls of SBA-15 prevents particle sintering at high temperatures. Moreover, a partially deactivated catalyst containing intercalated particles is regenerated almost completely even after several reaction cycles. In contrast, Pd particles, which are not encapsulated within the SBA-15 framework, sinter and do not recover prior activity after a regeneration procedure.

Fundamentals and recent progress relating to the fabrication, functionalization and characterization of mesostructured materials using diverse synthetic methodologies

“…[145][146][147][148][149] Mesoporous catalysts synthesized via in situ oxidation possess remarkable characteristics, such as high surface areas, uniform and large pores, and good mechanical and thermal stabilities, making them favourable for various catalytic applications. [150][151][152][153][154][155][156]…”

CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

“…The higher temperature during the CO oxidation does not affect the integrity of the catalyst. However, the quantity of large mesopores and macropores is eliminated due to the collapse following the heat treatment, leading to a higher ratio of micropores and small mesopores, as reported by Gage et al [25]. BET results show that the average pore diameter of the Pd/SiO 2 aerogel slightly reduced to 15.6 nm and the pore volume slightly increased to 0.06 cm 3 /g, although the surface area reduced to~940.9 m 2 /g.…”

In Situ Hydrogen Peroxide Production for Selective Oxidation of Benzyl Alcohol over a Pd@Hierarchical Titanium Silicalite Catalyst

“…The encapsulation of metal particles in the microporous zeolitic materials can improve their stability against thermal sintering. 17 − 22 Owing to high thermal stability and a confining environment, zeolitic materials promise to be potential supports for preparing various metal catalysts. However, during the reaction or harsh thermal treatments, the active metal particles, which are located on the external surface of zeolites prepared by wet impregnation or ion exchange, may aggregate to form bigger particles, bringing about a decrease in activity.…”