Enhancing the interaction between Mn and Ce oxides supported on fly ash with organic acid ligands interface modification for effective VOC removal: A combined experimental and DFT plus U study

This work reports a procedure for increasing VOC removal from flue gas using binary oxides (Ce-Mn) supported on fly ash by facile mechanochemical synthetic method in the presence of a solid organic acid ligand (OAL). The presence of OAL during the synthesis process helped produce larger and more accessible particle surface areas, by generating an abundance of micro-/meso porous structures. Meanwhile, the Ce-Mn interaction was enhanced in the catalyst produced (Ce-Mn-OFA) by the presence of OAL during the milling process, yielding a higher ratio of Mn3+/Mn4+ and Ce3+/Ce4+, more lattice defects and surface oxygen vacancies, and greater lattice oxygen mobility. The resulting changes in the fly ash properties substantially improved the oxidation and adsorption activity of Ce-Mn-OFA thus enhancing the catalyst's potential for VOC removal. The Ce-Mn-OFA catalyst showed the highest catalytic activity for benzene, toluene, m-xylene, and ethylene, which reached 90% conversion at 283 degrees C, 237 degrees C, 216 degrees C, and 264 degrees C, respectively. More importantly, the presence of the OAL increased the reactive oxygen species and acid sites on the surface of Ce-Mn-OFA, thus weakening the inhibiting effect of NO, NH3, H2O, and SO2 on the VOCs oxidation process. Furthermore, when Ce-Mn-OFA was applied using a special injection system to a large-scale pilot unit, the total concentration of 12 VOCs in the flue gas was reduced from 1347.3 mu g/m(3) to 131.2 mu g/m(3). The main contributions of the present work can be summarized as follows: 1) Providing a facile and environmentally friendly new process for the preparation of a heterogeneous catalyst; 2) Revealing the mechanism by which OAL enhances the activity of Ce-Mn in a binary metal oxide catalyst; 3) Evaluating the performance of Ce-Mn-OFA in a real flue gas, which provides feasibility support for its industrial application, such as in coal-fired power plants.

Automated summary

This work presents a method for increasing VOC removal from flue gas. By using a mechanochemical synthesis method and adding a solid organic acid ligand (OAL), the catalyst, Ce-Mn-OFA, showed improved oxidation and adsorption activity, making it a potential solution for VOC removal.