Synthesis and optimization nanocomposite catalyst based on silver@Zeolite imidazolite frameworks - 67 (Ag@ZIF-67) and...

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.