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Medium and low temperature NH3-SCR is an effective method for the nitrogen oxides (NOx) removal in industrial furnaces. The chromium (Cr) and cerium (Ce) based catalysts perform excellent NH3-SCR potential...

BACKGROUND: Coal gangue causes a series of environmental problems due to its low utilization rate and high amount of hoarding. However, the preparation of porous materials with coal gangue is an effective method of resource utilization. Mesoporous silica and meso-microporous ZSM-5 were prepared with alkali melting activation-acid leaching and hydrothermal synthesis, respectively. The orthogonal experiment was used to explore the optimal preparation conditions for mesoporous silica. Meso-microporous ZSM-5 were characterized with instruments. The adsorption and desorption performance of the porous material was explored by dynamic adsorption/desorption on volatile organic compounds (VOCs).RESULTS: The optimal preparation conditions for mesoporous silica are a roasting temperature of 800 °C, mass ratio of coal gangue to sodium carbonate of 1:0.6, and sulfuric acid leaching of 4 mol L −1 . The characterization results show that the molecular sieve has a superior specific surface and a certain amount of mesoporous pores due to the addition of the appropriate mesoporous template. The results of toluene dynamic adsorption experiments show that the meso-microporous ZSM-5 (ZSM-5-0.025PAC) has excellent adsorption and desorption performance (the adsorption capacity is up to 47.02 mg g −1 ), water resistance (the adsorption capacity decreased only 4.64%), and renewability (the adsorption and desorption efficiency is up to 95% and 97%).CONCLUSION: The porous materials prepared presented excellent VOCs ad/desorption performance, which has good industrial application prospects. The research provides a novel approach for the utilization of coal gangue.

BACKGROUND: The meso-microporous ZSM-5 is used for treating the complicated industrial organic waste gas, owing to its good hydrophobicity, excellent thermal and hydrothermal stability, and lower mass transfer resistance than conventional ZSM-5, resulting in its great adsorption property for volatile organic compounds (VOCs). In this paper, different types of meso-microporous ZSM-5 (NZ5, MZ5) were prepared using the templates and then characterized by X-ray diffraction, infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, and so on. The adsorption/desorption performance and diffusion mechanism of VOCs on meso-microporous ZSM-5 were further investigated. RESULTS: The meso-microporous ZSM-5 (MZ5), prepared with the cationic surfactant, contained not only large and uniform mesopores but also certain amounts micropores. Moreover, it exhibited excellence adsorption performance for organic molecules due to its relatively reasonable porous structure. The rich porous structure might mean that the cationic surfactant had better effects for producing mesopores in zeolite than the organic additives, such as phenyltriethoxy silane. More importantly, it showed the excellent thermal and hydrothermal stability and great desorption property, which was more than 95% within 20 min at 200°C. Finally, the diffusion mechanism of toluene on the meso-microporous ZSM-5 was investigated, which was suitable for Fick's second law under the low adsorption pressure. CONCLUSION: The meso-microporous ZSM-5 (MZ5, NZ5), prepared by hydrothermal synthesis method with the template, exhibited excellent adsorption/desorption performance, thermal and hydrothermal stability and lower mass transfer resistance than the conventional ZSM-5 (CZ5) for handling the VOCs.