Enhanced performances in catalytic oxidation of o-xylene over hierarchical macro-/mesoporous silica-supported palladium catalysts

Abstract

A series of hierarchical macro-/mesoporous silica supports (MMSs) were successfully synthesized using dual-templating technique employing polystyrene (PS) spheres and the Pluronic P123 surfactant. Pd was next loaded on the hierarchical silica supports via colloids precipitation method. Physicochemical properties of the synthesized samples were characterized by various techniques and all catalysts were tested for the total oxidation of o-xylene. Among them, the Pd/MMS-b catalyst with tetraethoxysilane/polystyrene weight ratio of 1.0 exhibited superior catalytic activity, and under a higher gas hourly space velocity (GHSV) of 70000 h -1 , the 90% conversion of o-xylene has been obtained at around 200°C. The BET and SEM results indicated that Pd/MMSb catalyst possesses high surface area and large pore volume, and well-ordered, interconnected macropores and 2D hexagonally mesopores hybrid network. This novel ordered hierarchical porous structure was highly beneficial to the dispersion of active sites Pd nanoparticles with less aggregation, and facilitates diffusion of reactants and products. Furthermore, the Pd/MMS-b catalyst possessed good stability and durability.

Sodium-treated sepiolite-supported transition metal (Cu, Fe, Ni, Mn, or Co) catalysts for HCHO oxidation

“…All of the sorption isotherms were type I in the range of low relative pressures, due to the existence of a microporous structure [26]. When the relative pressure (p/p0) was in the range of 0.81.0, a type IV adsorption isotherm was observed, with a type H3 hysteresis loop, indicating the presence of slit-like mesopores [27]. BET surface areas of the NaSep and TM/NaSep samples are summarized in Table 1.…”

Catalytic Oxidation of HCHO over the Sodium-Treated Sepiolite-Supported Rare Earth (La, Eu, Dy, and Tm) Oxide Catalysts

“…The isotherm of each sample corresponded to the type I in the range of low relative pressures, which was due to the existence of a microporous structure [24]. When the relative pressure was in the range of 0.8-1.0, there was a type IV adsorption isotherm with a type H3 hysteresis loop, indicating the presence of the slit-like mesopores [25]. BET surface areas of the NaSep and RE/NaSep samples were listed in Table 1.…”

“…Surface area decreased in the order of NaSep (96 m 2 /g) > Tm/NaSep (64 m 2 /g) > La/NaSep (47 m 2 /g) > Eu/NaSep (43 m 2 /g) > Dy/NaSep (31 m 2 /g). 0.8-1.0, there was a type IV adsorption isotherm with a type H3 hysteresis loop, indicating the presence of the slit-like mesopores [25]. BET surface areas of the NaSep and RE/NaSep samples were listed in Table 1.…”