Synthesis and characterization of Pd/ZSM-5/MCM-48 biporous catalysts with superior activity for benzene oxidation

Abstract

a b s t r a c t ZSM-5/MCM-48 composite materials with different acidities and enhanced thermal stability have been synthesized via a simple and reliable in situ overgrowth method. The as-prepared biporous materials and the Pd-impregnated catalysts were systematically investigated by various techniques, including XRD, ICP-OES, N 2 adsorption/desorption, H 2 chemisorption, SEM, TEM/HRTEM, FT-IR, 27 Al MAS NMR, NH 3 -TPD, H 2 -TPR and XPS. The characterization results reveal that all composite catalysts exhibit high surface area, large pore volume and long pore diameter. The quantity of acid sites increases as the ZSM-5 additive amount increases, and Al atoms are in the tetrahedral coordination positions in composite materials. The activity tests demonstrate that all the Pd-loaded catalysts are active in the total elimination of benzene, while the catalytic activity values of Pd-loaded ZSM-5/MCM-48 composite catalysts are much higher than those of Pd/ZSM-5 or Pd/MCM-48 alone. Both Pd 0 and Pd 2+ are responsible for the oxidation reaction, and the catalytic activities are primarily related to the support acidity and the Pd dispersion. In addition, the stability of the composite catalysts also improves with an appropriate amount of ZSM-5 additives in MCM-48. This research shows that the novel Pd-loaded composite catalysts are promising materials in the elimination of VOCs.

Facile preparation of 3D ordered mesoporous CuOx–CeO2 with notably enhanced efficiency for the low temperature oxidation of heteroatom-containing volatile organic compounds

“…[46][47][48][49][50] Herein, for the first time, we have prepared a series of 3D ordered mesoporous CuO x -CeO 2 catalysts through reverse replication of the structure of FMA-SBA-16 for use in the low temperature oxidation of epichlorohydrin (ECH: a representative and highly toxic HCVOC widely used in industry) with the aim of developing a more efficient catalyst for HCVOC removal. The catalytic performance of these materials was extensively compared to that of the corresponding single oxide, and the CuO x -CeO 2 binary oxides synthesized via traditional incipient impregnation, coprecipitation and thermal combustion methods.…”

Ligand-assisted preparation of highly active and stable nanometric Pd confined catalysts for deep catalytic oxidation of toluene

“…Currently, VOCs catalytic oxidation has been widely investigated over different types of catalysts, such as supported noble metals, metal oxides, and mixtures of noble metals and metal oxides [6,7]. Particularly, Pd-loaded catalysts are extensively examined considering their superior activity and high tolerance to moisture [8].…”

Nanometric palladium confined in mesoporous silica as efficient catalysts for toluene oxidation at low temperature

“…Besides, many researchers reported that the performance of Pdsupported catalysts for the oxidation of VOCs is highly dependent on the oxidation state of Pd species [7,16,24]. Some investigators proposed that the metallic Pd (i.e., Pd 0 ) is the most active phase in hydrocarbons catalytic oxidation, whereas PdO is inactive [52,53].…”

“…In order to make the reaction economically competitive, it is of great importance to explore higher active catalysts to perform at low temperatures. Currently, different types of catalysts, such as supported noble metals, transition metal oxides and their mixtures, are being widely investigated in VOC oxidation [7]. Particularly, supported Pd catalysts are extensively studied considering their superior activity, excellent thermal stability and high tolerance to moisture [8].…”

“…Various strategies were developed for incorporating metal nanoparticles into mesoporous silica, such as chemical vapor deposition [23], wet impregnation [7,16,24,25] and ion exchange [26]. However, the aforementioned approaches could not ensure the encapsulation of Pd nanoparticles inside the mesoporous channels, and hence large metal aggregates would form on the external surface of supports during thermal treatments or reactions.…”