HC-SCR: NOx Reduction using Mn and Cu Catalysts Impregnated on Coconut Shell-based and Palm Kernel Shell-based Activated Carbon

Sherra Bellina, Barrabas Kuta (2021) HC-SCR: NOx Reduction using Mn and Cu Catalysts Impregnated on Coconut Shell-based and Palm Kernel Shell-based Activated Carbon. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

A need of economical and tenable resources for Selective Catalytic Reduction (SCR) metallic catalyst production, the characteristics of catalysts and the coconut shells (CS) and palm kernel shells (PKS) activated carbon were determined as potential precursors for the catalyst used in the system of flue gas denitrification at low temperature. Hydrocarbon Selective Catalytic Reduction (HC-SCR) has been a promising method to be an alternative approach for reduction of NOx emissions because it consumes inherent hydrocarbon and is operated at low temperature. Therefore, the aim of this research is to investigate the potential of selective catalytic reduction activity towards NOx reduction along with the factors that influence the efficiency of catalysts performance. In this reserach, adsorption and reduction phenomenon are believed to happen simultaneously. Therefore, activated carbon CS and PKS were studied for its adsorption capability, thermodynamic as well as adsorption isotherms (i.e Langmuir and Freundlich). For catalytic activity, activated carbon (AC) was impregnated with Manganese (Mn) and Copper (Cu) metals prior undergoing low temperature treatment of calcination process for their NOx reduction potential. The potential of impregnated of CS and PKS with manganese and copper, respectively, with different concentration (8%, 10% and 12%) have been studied in the catalytic studies utilizing fixed-bed catalytic reactor was used to investigate the activities of catalysts in order to compare the NOx gas reduction performance by varying temperature ranging from 150 °C-250 °C. Both raw ACs and the metallic catalysts were further characterized using BET, SEM, XRF, H2-TPR, and XRD to support the findings obtained from the activities of the NOx reduction catalysts. Better performance of adsorption was observed in CSAC compared to PKSAC under different temperature conditions which was recorded 27.32% while PKSAC, 21.95%. This was due to the size of pores of CS was slightly bigger than PKS in BET analysis. For isotherm studies, the value of R2 of Langmuir isotherm plot was very near to the most fitting value of R2 = 1, meanwhile, for Freundlich isotherms with R2 > 0.98, it was noticed that it fitted less with the NO sorption by CS and PKS. NO sorption result at different NO initial concentration versus capacity of sorption shows both ACs were favorable for adsorption since both of the R-squared were near to 1. The error difference between the experiment and predicted data was less than 4% and 5% respectively for CS and PKS indicates that the isotherm model exhibit excellent reproduction of the experimental data at the whole concentration range for the component adsorption of NO from flue gas. As for thermodynamic study, both CS and PKS adsorption of NOx was found increase with increase in temperature. Results show a negative value for Gibb’s free energy at all temperature ranges and ∆G⁰ increases with increase in temperature. These negative values represent spontaneous nature as well as feasibility of adsorption reaction. Decrease in ∆G with the increase in temperature reflects better sorption at elevated temperature. The positive value for change in entalphy is due to endothermic nature of adsorption of NOx. For catalytic study, the highest NOx reduction percentage of NOx conversion can be seen at 200 °C for both CS-Cu8 and CS-Cu10, respectively recorded 70.02% and 76.83% due to the advantage of having better potential in redox reaction in SCR system for the selectivity of NOx proven by H2-TPR analysis. Overall, CS-Cu10 has demonstrated the potential of the metallic catalyst for NOx reduction; however improvisation on the synthesis technique is required to combat generation of impurities during the combustion may clog the pore structure of the catalyst supports at higher temperature than 200 °C.

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