Hydrochloric acid-modified CuAlOx catalyst for simultaneous removal of hydrogen sulfide and phosphine at low temperature

Abstract

Chemical modification is a critical method to improve the properties and structures of catalysts, which remains challenging. In this study, a series of Cu–Al catalysts were prepared by a hydrothermal synthesis method for hydrogen sulphide (H₂S) and phosphine (PH₃) removal at 80 °C, and the role of metal complexes and acid were discussed in detail. Results showed that the HCl-treated CuAlO_x catalyst with the molar ratio of Cu : Al : HCl = 5 : 5 : 1 exhibited the highest performance among all the materials tested, corresponding to capacities of 37.25 mgS g⁻¹ for sulfur and 64.15 mgP g⁻¹ for phosphorus. The catalysts were characterized by X-ray diffraction, Brunauer–Emmett–Teller analysis, X-ray photo electron spectroscopy, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma, and in situ IR. Results showed that HCl was able to expose more active sites and expand the catalyst channel by speciation generation and structural corrosion. Cu⁺ species was the most important constituent in the catalyst. It was derived from the reduction of Cu²⁺ species, facilitated by the provision of additional electrons from Cl ions and H₂ in the thermal treatment process. Metal coordination promoted the interaction of metal crystal faces, which offered more advantages in pollutant removal than single copper or aluminum. Pollutant molecules were vertically adsorbed on the Cu⁺ species to generate sulfur species and phosphorus species with the help of oxygen species and active sites. Subsequently, the products rapidly shifted to the surface of the catalyst and occupied the active sites and vacancies, resulting in inactivation. The strategy of metal coordination and acid treatment is an important approach that provides possibilities for enhanced catalytic performance in various applications.