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Zeolites with uniform pore structures and surface properties are potential adsorbents for volatile organic compounds (VOCs) adsorption. Although various zeolites have been researched for VOCs adsorption, the adsorption capacity still needs to be improved. In this work, EMT zeolite was synthesized and modified by polyethylene glycol (PEG400) as a high-capacity adsorbent for acetone purification. The structures of sorbents were characterized by X-ray diffraction, scanning electron microscopy, N2 adsorption–desorption isotherm, Fourier transform infrared, thermogravimetric analysis, and X-ray fluorescence spectrometer. Experimental results indicated that 0.6PEG-modified EMT zeolite with high specific surface area, large mesoporous volume, and more hydroxyl groups significantly improved the acetone adsorption property, which was 20.6% higher than pure EMT zeolite. The addition of PEG400 also enhanced the cyclic stability. The adsorption mechanism was further analyzed via adsorption kinetics and thermodynamics, which demonstrated the adsorption of acetone in EMT zeolite belonged to physical adsorption. Overall, PEG400-modified EMT zeolite presented the potential to be a promising candidate for efficient acetone adsorption in commercial applications. [ABSTRACT FROM AUTHOR]

Coal gangue is a typical waste produced during coal mining and washing. Synthesis of zeolites via coal gangue can contribute to resource recycling and environmental protection. In this study, high-silica SSZ-13 was synthesized by one-step hydrothermal synthesis from coal gangue without the traditional pretreatment methods of high-temperature roasting and alkali melting, making it more convenient and energy efficient. The synthesis time, gel silicon–aluminum ratio and silicon source were systematically studied to optimize the synthesis of SSZ-13. Experimental results indicated that the nucleation time of SSZ-13 could be shortened to 7 h, which was half the synthesis time by using chemicals. Tetrahedral aluminum was the main factor for rapid synthesis, which also accelerated the transformation of octahedral aluminum and further accelerated the synthesis of SSZ-13. The DeNOx activity of the synthesized Cu-SSZ-13 was over 90% across a broad range from 180 to 400 °C, and it remained over 85% in this temperature range even after hydrothermal treatment for 12 h. It also demonstrated good water resistance (over 95% DeNOx in the range of 200 to 400 °C) and sulfur resistance (over 95% DeNOx in the presence of 100 ppm SO2). [ABSTRACT FROM AUTHOR]

The NOx conversion of Cu 3.1 -OFF-CHA-Fresh was maintained above 90 % in the range from 160 to 550 ℃, and it still remained above 80 % in the range 180–450 °C even after hydrothermal treatment. [Cu(OH)]+ was more affected by hydrothermal treatment than Cu2+ in Cu-OFF-CHA. Cu2+ in Cu-OFF-CHA was mainly migrated from CHA to OFF sites after hydrothermal treatment, and Cu2+ in OFF sites on Cu-OFF-CHA should be more stable, resulting in less conversion of Cu2+ to CuOx clusters. Thus, it is inferred that OFF zeolite was the main reason for excellent hydrothermal stability of Cu-OFF-CHA catalyst. [Display omitted] • Al-rich OFF-CHA zeolite twin-crystal was synthesized by one-pot hydrothermal method. • Cu-OFF-CHA exhibited excellent SCR activity and hydrothermal stability. • OFF zeolite was the main reason for excellent hydrothermal stability of Cu-OFF-CHA. Novel Al-rich OFF-CHA twin-crystal zeolite was synthesized by one-pot hydrothermal method, and applied in ammonia-selective catalytic reduction (NH 3 -SCR) after copper ion exchange. Results indicated that Cu content in Cu-OFF-CHA played a significant role in NH 3 -SCR reaction. The insufficiency of copper activity sites and the formation of CuOx were the main reasons affecting low and high temperature SCR activity of catalyst, respectively. Cu 3.1 -OFF-CHA, with the optimal copper content, demonstrated over 90 % NOx conversion and exhibited excellent N 2 selectivity in the range from 160 to 550 ℃. Further research verified that the SCR activity of Cu 3.1 -OFF-CHA maintained above 80 % in the temperature range from 180–450 °C after hydrothermal treatment 16 h. The reason might be that Cu2+ in Cu-OFF-CHA was migrated from CHA to OFF sites after hydrothermal treatment, and Cu2+ in OFF sites on Cu-OFF-CHA was more stable, resulting in less conversion of the active site to CuOx clusters. Cu-OFF-CHA has the potential to be applied in SCR after-treatment systems of diesel exhaust due to the excellent SCR activity and hydrothermal stability. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) with high toxicity and carcinogenicity are emitted from kinds of industries, which endanger human health and the environment. Adsorption is a promising method for the treatment of VOCs due to its low cost and high efficiency. In recent years, activated carbons, zeolites, and mesoporous materials are widely used to remove VOCs because of their high specific surface area and abundant porosity. However, the hydrophilic nature and low desorption rate of those materials limit their commercial application. Furthermore, the adsorption capacities of VOCs still need to be improved. Porous organic polymers (POPs) with extremely high porosity, structural diversity, and hydrophobic have been considered as one of the most promising candidates for VOCs adsorption. This review generalized the superiority of POPs for VOCs adsorption compared to other porous materials and summarized the studies of VOCs adsorption on different types of POPs. Moreover, the mechanism of competitive adsorption between water and VOCs on the POPs was discussed. Finally, a concise outlook for utilizing POPs for VOCs adsorption was discussed, noting areas in which further work is needed to develop the next-generation POPs for practical applications. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Binder-free zeolite pellets are synthesized by a citric acid sacrifice strategy. • Pellets with a well-defined macroscopic shape exhibit robust mechanical strength. • Pellets have superior VOCs adsorption capacity under dry and humid condition. • In situ dealuminization improves the specific surface area of zeolite pellets. Zeolites are promising materials for the adsorption of volatile organic compounds (VOCs), thanks to their unique pore structure, large specific surface area, and excellent stability. However, the synthesis of monolithic zeolites with a well-defined macroscopic shape, significant mechanical strength, and high VOCs adsorption capacity in humid conditions remains challenging. Here, the synthesis of binder-free monolithic zeolite pellets, possessing robust mechanical strength, high adsorption capacity, and excellent water tolerance, is reported through a citric acid sacrifice strategy. By in situ dealuminization, Y zeolite pellets have greatly improved the specific surface area and mesopore volume, leading to superior acetone and toluene adsorption performance. Moreover, the extracted aluminum species produced during the dealuminization act as a "bridge" to promote the zeolite particles into pelletization with a sufficiently high mechanical strength. Under 90% relative humidity, the acetone and toluene adsorption capacity of the synthesized zeolite pellets reach above 90% of the adsorption capacity under dry conditions, showing potential in practical industrial application. It is anticipated that this synthetic strategy will benefit the forming and development of monolithic zeolite. [ABSTRACT FROM AUTHOR]

Catalytic oxidation is one of the most promising methods to remove VOCs. Herein, a zeolite-confined PtMn bimetal catalyst (PtMn 0.2 @ZSM5) was synthesized using a ligand-assisted hydrothermal method, which showed extraordinary catalytic activity with a T 95 of 165 ℃ for the acetone oxidation in the presence of 5 vol% water. Thanks to the zeolite confinement and bimetallic synergy effect, the PtMn 0.2 @ZSM5 exhibited small nanoparticle sizes, abundant acid sites, higher active Pt0 content, and sufficient active oxygen species. These excellent properties promoted the adsorption of VOC, the deep oxidation of VOC, and the desorption of CO 2. In-situ DRIFTS proposed an L-H mechanism for acetone oxidation over PtMn 0.2 @ZSM5. Significantly, the PtMn 0.2 @ZSM5 presented good durability and water resistance under high GHSV conditions. Also, it was confirmed effective for various VOCs oxidation, such as toluene, ethyl acetate, propane, and dichloromethane, showing a promising industrial prospect for eliminating VOCs. [Display omitted] • A zeolite-confined PtMn 0.2 @ZSM5 catalyst was successfully synthesized. • The PtMn 0.2 @ZSM5 showed excellent catalytic performance for VOCs oxidation. • Zeolite confinement effect and Pt-Mn synergy effect was verified to be the keys. • An L-H mechanism for acetone oxidation over PtMn 0.2 @ZSM5 was proposed. [ABSTRACT FROM AUTHOR]

• Y@St-DVB composites with hydrophobicity were synthesized successfully. • Samples had excellent the toluene adsorption capacity at dry and humid condition. • Y@St-DVB-12h exhibited excellent the adsorption and desorption performance. • A new class of zeolites and polymer core-shell composites could be prepared. Zeolites with high specific surface area and good stability are considered ideal adsorbent for volatile organic compounds (VOCs) adsorption. However, the hydrophilicity of zeolites surface limits their practical application because of the competitive adsorption between water and VOCs. In this work, we reported a strategy to synthesise Y zeolite and hydrophobic organic polymer core-shell composites (Y@St-DVB), which significantly improved the hydrophobicity and toluene adsorption capacity of Y zeolite. The TEM results showed that hydrophobic organic polymer was uniformly coated on the external surface of Y zeolite through the bridging effect of phenylsilane. The adsorption capacity of Y@St-DVB-12h was 69.9% higher than that of Y zeolite at dry condition, and increased about 96% under 90% relative humidity (RH). It also exhibited excellent adsorption and desorption performance under 60% RH, which was suitable for the practical application. In addition, such composite strategy was suitable for other zeolites (EMT, ZSM-5, and Beta zeolite) to realise hydrophobic modification, which increased the adsorption capacity under wet conditions. This work not only proposes a new hydrophobic zeolite-based VOCs adsorbent, but also provides a new idea for the preparation of a series of hydrophobic adsorbents. [ABSTRACT FROM AUTHOR]