Sustainable utilization of chlorine via converting HCl to Cl2 over a robust copper catalyst

Abstract

Offering a substantial method to convert HCl to Cl2 over CuCl2/pumice, Deacon process is of great importance in chemical industry. In the process, the difficulty of Cl2 formation/desorption and catalyst re-oxidation have been unanimously recognized as the origin of the instability of CuO-based catalysts. In this work, the stability of the CuO/Al2O3 catalyst was significantly improved by adding Co. The fabricated CuO(12)–CoOx(13)/Al2O3 catalyst showed unprecedented stability with HCl conversion (xHCl) above 80%, lasting for at least 1000 h. The X-ray diffraction (XRD), Raman spectra, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and H2-temperature programmed reduction (H2-TPR) characterizations suggested that the addition of Co greatly enhanced the dispersion of CuO on Al2O3 and hindered the reduction of CuO due to their strong interaction. The results of reaction kinetics suggested that the lattice oxygen participated in the reaction and the reaction order on oxygen was estimated to be 0.15, suggesting that the catalyst obeyed the Mars-van Krevelen (M-K) mechanism, while only small amount of oxygen was required to maintain the activity of catalysts compared to CuO/Al2O3. Density functional theory (DFT) calculations proved that the CuO–CoOx/Al2O3 ternary system was more stable than CuO/Al2O3 binary system and easier to be oxidized by O2, which greatly reduced the difficulty of Cl2 associative desorption.