Enhancing Formaldehyde Selectivity of SnO2 Gas Sensors with the ZSM-5 Modified Layers

High performance formaldehyde gas sensors are widely needed for indoor air quality monitoring. A modified layer of zeolite on the surface of metal oxide semiconductors results in selectivity improvement to formaldehyde as gas sensors. However, there is insufficient knowledge on how the thickness of the zeolite layer affects the gas sensing properties. In this paper, ZSM-5 zeolite films were coated on the surface of the SnO2 gas sensors by the screen printing method. The thickness of ZSM-5 zeolite films was controlled by adjusting the numbers of screen printing layers. The influence of ZSM-5 film thickness on the performance of ZSM-5/SnO2 gas sensors was studied. The results showed that the ZSM-5/SnO2 gas sensors with a thickness of 19.5 μm greatly improved the selectivity to formaldehyde, and reduced the response to ethanol, acetone and benzene at 350 °C. The mechanism of the selectivity improvement to formaldehyde of the sensors was discussed.

Low Concentration Synthesis of Super-Amphiphilic Nanoflake ZSM-5 Film with Adjustable Property

High silica zeolite ZSM-5/glass film was successfully synthesized by an in-situ sol–gel dip-coating process combined with the steam-assisted conversion (SAC) technique with low concentration of the synthesis solution. The resulting zeolite films grown on the glass slide show amphiphilic properties. The growing process and the effect of the concentration of SiO2 in the silica source were examined. The mechanism of the formation of the nanoflake crystals and their wetting behavior was investigated. By simply adding fluorescein in the synthesis solution during the preparation, ZSM-5 films showing luminescence property can be obtained. Furthermore, these ZSM-5 zeolite films are easily modified to exhibit hydrophobic property.

A New Method for the Measurement of the Diffusion Coefficient of Adsorbed Vapors in Thin Zeolite Films, Based on Magnetoelastic Sensors

In the current work an experimental method is used in order to calculate the diffusivity D (diffusion coefficient) of various vapors in thin zeolite films. The method is based on adsorption data from magnetoelastic sensors on top of which a zeolite layer was synthesized, and the diffusivity is extracted by fitting the data to Fick’s laws of diffusion. In particular, the method is demonstrated for two volatile organic compound (VOC) vapors on two different zeolites, the p-Xylene adsorption in Faujasite type zeolite with D = 1.89 × 10 − 13 m 2 / s at 120 ° C and the propene adsorption in Linde Type A type zeolite with D = 5.9 × 10 − 14 m 2 / s at 80 ° C , two diffusion coefficients which are extracted experimentally for first time. Our results are within the order of magnitude of other VOC/zeolite values reported in literature.

Microfluidic processing of HZSM-5 films in a capillary microreactor for the continuous acetalisation reaction of glycerol with acetone

This work presented microfluidic processing of zeolite films in a capillary microreactor and its potential application for biomass conversion.