Synthesis and optimization nanocomposite catalyst based on silver@Zeolite imidazolite frameworks − 67 (Ag@ZIF-67) and catalytic application for ethyl benzene vapor removal in air matrices

The presence of volatile organic compounds (VOCs) poses significant health and environmental risks. This study investigates the catalytic oxidation of ethylbenzene (EB) vapor using a silver-impregnated zeolitic imidazolate framework-67 (Ag@ZIF-67). The effectiveness of the catalyst in converting EB was evaluated in a continuous-flow fixed-bed reactor. The Ag@ZIF-67 catalyst was synthesized and characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier-transform infrared spectroscopy (FTIR). The XRD patterns of the synthesized ZIF-67 and Ag@ZIF-67 showed distinct peaks, confirming the successful formation of the sodalite framework. The results indicate that relative humidity (RH) significantly influences performance: at low RH (30%), removal efficiency improved at lower temperatures due to enhanced pollutant transport to active sites. In contrast, high RH (70%) reduced efficiency at temperatures above ≈ 250 °C as water molecules blocked EB access to active sites. Space velocity (SV) was also critical: lower SVs resulted in higher removal efficiency for both 50% (T₅₀) and 90% (T₉₀) conversions of EB. As SV increased, T₅₀ shifted from 97 °C to 111 °C and T₉₀ from 211 °C to 223 °C, indicating decreased efficiency. Higher EB concentrations initially increased removal efficiency at low temperatures, but at higher concentrations active-site saturation occurred, reducing efficiency. For example, increasing the EB concentration raised T₅₀ from 87 °C to 127 °C and T₉₀ from 198 °C to 231 °C, demonstrating a decline in catalyst performance. These findings advance the understanding of metal-organic framework (MOF) based catalysts for VOC control and provide insights for developing air pollution mitigation technologies.