Title : The effect of physico-chemical properties obtained by various preparation techniques on CoCuAl Oxide for CO2 purification of industrial flue gas
Abstract:
Human and environmental health has become a critical concern due to various pollutants mainly CO2 from industrial flue gases that require carbon capture and purification before valorization. For the purification of industrial flue gas (CO2, O2, CO, NO, H2O), selective catalytic reduction (SCR) of NO by CO under oxidative and wet conditions is conducted effectively in the presence of transition metal-based catalysts, particularly cobalt and copper [1]. Recent studies revealed that hydrothermal treatment for Layered Double Hydroxide (LDH) materials could promote better crystallinity and enhance active site dispersion [2]. In addition, the use of anionic β-cyclodextrin is known to be an effective approach in the preparation of heterogeneous catalysts for better dispersion and smaller particle size [3]. Therefore, the aim is to study the effect of various LDH-modified preparation techniques on CoCuAl-based catalysts for the SCR process of industrial flue gas under oxidative and wet conditions.
Cobalt-Copper-Aluminum LDH (Co4Cu2Al2) was synthesized via the co-precipitation method using either sodium carbonates or carboxymethyl-β-cyclodextrins (CM-β-CD) as the interlayer anion [3]. For carbonates-prepared LDH, the aging (maturation) step was modified using either classical room temperature or hydrothermal treatment. All samples were calcined under CO2 at 400 °C, characterized by various techniques (XRD, TGA, FTIR, Raman …), and then tested in a continuous-flow reactor under simulated flue gas conditions4 (20.5% CO2, 8.8% O2, 8.2% H2O, 1300 ppm of CO and 500 ppm of NO) at temperatures ranging from 100 to 400 °C.
Various LDH modifications affected the catalytic activity of CO2 purification differently. In comparison with the classical LDH preparation route, hydrothermal treatment performed at 60 °C for Co4Cu2Al2 LDH preparation resulted in an enhancement in the NO reduction compared to both classical and cyclodextrin samples. The NO reduction (N2 yield) increased from 35% (Classical) to 47 % (Hydrothermal) at 300 °C where the CM-β-CD sample showed lower NO reduction temperature with minimal N2 yield. In comparison to the classical sample, a higher content of polydentate carbonate species (as observed by TGA and FTIR), higher BET surface area and enhanced voids spacing (N2 physisorption) were present within the hydrothermally treated sample promoting higher N2 yield. Further characterization (TPR, Raman …) will validate the enhanced catalytic activity occurrence.
