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Hierarchical porous ZSM-5 (HP-ZSM-5) was constructed using organosilanes as the growth inhibitors for CO2 capture. The properties of adsorbents were characterized by X-ray diffraction, N2 adsorption/desorption, scanning electron microscopy, temperature-programmed desorption of carbon dioxide, and 27Al magic angle spinning nuclear magnetic resonance. It was found that HP-ZSM-5 samples synthesized by organosilanes had a significant effect on the microstructure and morphology. CO2 adsorption capacity of HP-ZSM-5 was up to 58.26 cm3 g–1 at 0 °C and 1 bar, significantly higher than that of the ZSM-5 sample. The effective improvement of CO2 adsorption performance mainly originated from the micro-/mesoporous composite structure and complex surface morphology, which can provide low-resistant pathways for CO2 through the porous network. Besides, in situ Fourier transform infrared spectroscopy was carried out to study the adsorption process on adsorbents, and the results indicated that a faster physical adsorption process was achieved as a result of the introduction of mesopores.

Ce x Zr 1-x O 2 oxides prepared by a soft reactive grinding (SRG) procedure have been investigated as the catalysts for HCl oxidation. The results show that the catalytic activities and stabilities of Ce x Zr 1-x O 2 oxides are remarkably dependent on the Ce/Zr ratio. A correlation between the physicochemical properties and catalytic performances of these samples reveals that the cubic phase in Ce x Zr 1-x O 2 with higher oxygen storage capacity (OSC) is more activity for HCl oxidation, but the tetragonal phase is crucial to the stability of catalysts. The Ce 0.5 Zr 0.5 O 2 catalyst with mixed phases and the highest OSC (80 µmol O2 ·g cat -1 ) exhibits an excellent activity (1.89 g Cl2 ·g cat -1 ·h -1 at 430 °C) and stability (300 h) in the target reaction. Kinetic studies show that both O 2 and HCl competed for the active sites rendering desorption of surface Cl is the rate-determining step. Accelerating the replacement of surface Cl by O 2 is the essence for the activity improvement of Ce 0.5 Zr 0.5 O 2 .

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Alkyltrimethoxysilanes with different chain lengths (trimethoxypropylsilane, trimethoxyoctylsilane, and dodecyltrimethoxysilane) were utilized as mesopore-generating agents to synthesize hierarchical ZSM-5 samples with different amounts of mesoporous volume. The samples were characterized by X-ray powder diffraction, nitrogen adsorption–desorption, scanning electron microscopy, transmission electron microscopy, and CO2-temperature-programmed desorption. With the growth of chain length, the alkyl­trimethoxy­silanes showed low reactivity and affinity for the surfaces of zeolite precursors due to the increase of hydrophobic character of the alkyl moiety, which resulted in the decrease of mesoporous volume. CO2 adsorption behaviors of the samples including adsorption capacity, adsorption kinetics, adsorption selectivity, adsorption thermodynamics, and adsorbent stability were studied. The experimental results indicated that hierarchical ZSM-5 modified by trimethoxy­propyl­silane exhibited the highest mesopores volume (0.12 cm3·g–1), corresponding to the fastest capture rate (about 2.5 times of conventional ZSM-5) and the highest capture capacity (2.15 mmol·g–1 at 25 °C and 100 kPa). Therefore, hierarchical ZSM-5 synthesized by the alkyl­trimethoxy­silanes with short chain length can generate extra mesopores and active adsorption sites, which provided a new strategy to regulate the structure of ZSM-5 for rapid CO2 adsorption.