Pt/hierarchical ZSM-5 zeolites were successfully synthesized by the steam-assisted crystallization and subsequent wetness impregnation method. Structural features were characterized by XRD, N 2 isotherm, SEM, and TEM. Its catalytic behaviors for o-xylene storage at room temperature, and catalytic combustion of stored o-xylene at elevated temperatures were evaluated. It was found that crystallinity of the product underwent a reducing tendency after introduction of mesostructure, but the mesoporosity and pore volume were remarkably increased. Compared with Pt/conventional ZSM-5 zeolite, the o-xylene adsorption capacity of Pt/hierarchical HZSM-5 was around 8 times as that of the counterpart without mesostructure. Moreover, the Pt dispersion was improved due to mesoporosity. The highly dispersed Pt nanoparticles were beneficial for catalytic combustion of o-xylene. Futhermore, Pt/hierarchical ZSM-5 showed the efficient bi-functional performance during adsorption/catalytic combustion cycling process for o-xylene. Carbon balance was kept for three cycles without secondary pollutants, showing higher adsorption capacity and better reusing stability.
Avoiding the use of templates and employing natural minerals as raw materials could promote the cost-efficient preparation of mesoporous materials. This work demonstrated a template-free route to process natural halloysite into mesoporous silica with high specific surface area (SSA) up to 767 m 2 /g and pore size of about 5 nm.The halloysite was successively calcined, alkali-treated and acid-treated. The transformation of calcined halloysite into crystalline sodium aluminosilicate (zeolite LTA) by longtime alkali-treating, was found to be the key for obtaining high-SSA mesoporous silica in the final acid treatment. The optimized mesoporous silica showed a monolayer adsorption capacity as high as 741 mg/g for methylene blue, suggesting its great potential in adsorption applications.
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