- Thesis topic: The Application of Recycled Fly Ash as a Low-Cost Catalyst for NOx Removal

- ORCID or ResearchGate: orcid.org/0000-0003-2158-5557 

- Abstract: 

        Fly ash, an abundant industrial waste by-product containing complex compounds is produced from coal-fired power plants and the incineration of municipal and industrial solid waste. The global annual production of fly ash is approximately 1.5 to 2.0 billion tons. Notably, this significant amount is primarily generated in four major countries, namely China, India, the United States, and Indonesia, with each portion amounting to 40%, 30%, 12%, and 7%, respectively. This study addresses environmental challenges associated with nitrogen oxide (NOx) emissions by exploring the potential utilization of fly ash—an abundant industrial waste byproduct—as a catalyst. The widely used method for NOx reduction is selective catalytic reduction (SCR) using ammonia (NH3) with a vanadium catalyst. However, conventional catalysts like vanadium oxide have limitations, including narrow temperature ranges and toxicity concerns. In order to overcome these challenges, this study investigates a modified fly ash catalyst for NOx removal, considering the porous material and large specific surface area of fly ash, making it an effective adsorbent and catalyst carrier. The research conducted two sets of experiments focusing on modifying fly ash catalysts. The first experiment utilized three types of metal oxides such as ZrO2, TiO2, and MgO, while the second experiment employed the metal oxides CuO and MnO2. The results indicate that the optimal combination for the synthesis of the first experimental catalyst is FA/Zr-10, with a weight ratio of fly ash to ZrO2 at 90:10. For the second experimental catalyst, FA/Cu/Mn-5, with a weight ratio of fly ash to CuO and MnO2 at 90:5:5, proved to be the optimal catalyst. In the first experiment, variations of a single metal oxide produced surface areas ranging from 10.2 m2 g-1 to 46.1 m2 g-1. In the second experiment, using a combination of CuO and MnO2, the surface area ranged from 26.5 m2 g-1 to 45.43 m2 g-1. The first experimental catalyst demonstrated an efficiency of 90.3% in removing NOx at a temperature of 250°C, while the second experimental catalyst achieved an efficiency of 98.6% at a temperature of 200°C. The SCR process with FA/Cu/Mn-5 exhibited a reaction rate approximately ten times higher, around 6.108×10-3 min-1, compared to FA/Zr-10, which was approximately 6.287×10-2 min-1. This validates that the utilization of a modified fly ash catalyst with bimetallic oxide FA/Cu/Mn-5 is the best combination in this research for NOx removal in the SCR process. Additionally, this study provides valuable insights into the efficacy of modified fly ash catalysts in NOx removal by comparing their performance and operational conditions.

Keywords: Adsorption, Environmental, Fly Ash, Low-cost Analysis, Metal Oxide, Surface-modified Fly Ash Catalysts