Testing Metal–Organic Framework Catalysts in a Microreactor for Ethyl Paraoxon Hydrolysis

• Main Authors: Palani Elumalai, Nagat Elrefaei, Wenmiao Chen, Ma’moun Al-Rawashdeh, Sherzod T. Madrahimov
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Catalysts
• Subjects: MOF; catalyst; microreactor; kinetic studies
• Online Access: https://www.mdpi.com/2073-4344/10/10/1159

We explored the practical advantages and limitations of applying a <b>UiO-66</b>-based metal–organic framework (MOF) catalyst in a flow microreactor demonstrated by the catalytic hydrolysis of ethyl paraoxon, an organophosphorus chemical agent. The influences of the following factors on the reaction yield were investigated: a) catalyst properties such as crystal size (14, 200, and 540 nm), functionality (NH₂ group), and particle size, and b) process conditions: temperature (20, 40, and 60 °C), space times, and concentration of the substrate. In addition, long-term catalyst stability was tested with an 18 h continuous run. We found that tableting and sieving is a viable method to obtain MOF particles of a suitable size to be successfully screened under flow conditions in a microreactor. This method was used successfully to study the effects of crystal size, functionality, temperature, reagent concentration, and residence time. Catalyst particles with a sieved fraction between 125 and 250 µm were found to be optimal. A smaller sieved fraction size showed a major limitation due to the very high pressure drop. The low apparent activation energy indicated that internal mass transfer may exist. A dedicated separate study is required to assess the impact of pore diffusion and site accessibility.