Dual Functionalities of Inexpensive Mn/Tio2 Catalyst to Produce Oxychar for Ammonia Capture

Abstract

This study explores the dual functionality of a manganese/titanium dioxide (Mn/TiO2) catalyst in a low-temperature partial oxidation process to enhance the performance of oxychar for NH3 capture. The Mn/TiO2-modified oxychar demonstrated a significant increase in NH3 capture, achieving NH3 uptake of 62.8 mg/g at 140°C. The superior performance is attributed to strong chemical adsorption between NH3 and the oxygen-containing functional groups (OCFGs) associated with dissolved organic carbon. Mechanism study showed that O2 adsorbed on Mn/TiO2 surface can be activated for OCFG formation on oxychar. The second function of Mn/TiO2 is to enhance the product yields by inhibiting free radical chain reactions. At 220°C, Mn ions act as free radical scavengers, converting highly reactive radicals into less reactive species, preventing uncontrolled combustion, and promoting selective oxidation. This work advances the understanding of Mn-based catalysts in oxychar production, offering a scalable pathway for NH3 capture and sustainable waste recycling.

Keywords: Biomass, oxygen activation, reactive radical, circular economy, adsorption