The correlation between the iodine value of coconut shell carbon and their reaction performance for NO2 to NO

Abstract

AbstractBACKGROUNDThe precise detection of nitrogen dioxide (NO2) requires the conversion of NO2 to nitric oxide (NO) using a molybdenum conversion furnace. Currently, molybdenum wire is utilized as the conversion agent for the molybdenum furnace; however, the high operating temperature of the molybdenum wire can inadvertently convert ammonia (NH3) in industrial exhaust gas to NO, potentially impacting the accuracy of the detection process. Consequently, there is a pressing need to develop low‐temperature conversion agents. The study aims to establish a correlation between the iodine value, which characterizes the liquid‐phase adsorption properties of activated carbon (AC), and its capacity for NO2 conversion, with the potential to provide valuable theoretical insights supporting the development of commercial molybdenum furnace conversion agents.RESULTSThe iodine value of coconut shell carbon (C) is closely related to their reaction performance for NO2‐to‐NO among three samples with different iodine values. AC‐900, AC‐1200 and AC‐1500 exhibited notable NO2‐to‐NO conversion capabilities. Specifically, AC‐900 demonstrated significantly superior reaction performance compared to AC‐1200 and AC‐1500. Under conditions of 175 °C and 1 L min−1, the NO2 conversion rates for AC‐900, AC‐1200 and AC‐1500 were measured at 97.3%, 88.2% and 86.4%, respectively. Furthermore, the evaluation of AC‐1200 and AC‐1500 at different flow rates at 125 °C revealed a decrease in NO2 conversion with increasing gas flow rate. AC‐1200 exhibited better reaction performance compared to AC‐1500.CONCLUSIONThe structure–activity relationship between iodine value of coconut shell C and their NO2‐to‐NO performance is revealed. The capacity of AC to convert NO2 is significantly influenced by the presence of oxygen (O) functional groups and the proportion of micropores. The content of micropores and O‐containing functional groups, especially phenolic hydroxyl groups, decreases with the increase of iodine value, leading to a decrease in the reaction performance of the conversion agent. © 2024 Society of Chemical Industry (SCI).