Catalytic hydrodechlorination of 4-chlorophenol: Role of metal phase supports and reaction pH

4-Chlorophenol belongs to a family of persistent organic pollutants frequently found in wastewater. This compound presents a significant environmental challenge due to its high stability and, consequently, slow degradation in natural conditions. Therefore, the study of methodologies to remove or degrade this compound is of utmost importance. Catalytic hydrodechlorination (HDC) is one technique that can be employed to eliminate it. However, it is important to bear in mind that some hydrochloric acid (HCl) may be formed during this process, potentially leading to catalyst poisoning. Thus, the evaluation of the pH is crucial. This study investigated two reaction media: water and a solution of 2 mM NaOH, which acts as a buffer to mitigate the pH decrease caused by HCl formation. Palladium, a noble metal well-regarded in the scientific community for its high activity in the HDC reaction and its resistance to catalyst poisoning, was used. This metal was impregnated onto four different supports: alumina (Al2O3), titanium dioxide (TiO2), activated carbon (AC) and carbon nanotubes ball milled (CNT BM). The catalytic tests revealed that the catalyst support plays a pivotal role in the reduction of chlorophenols, and the activity order among the different catalysts varied depending on the reaction media used. The better-performing catalysts were 5 % Pd/TiO2 and 5 % Pd/CNT BM in the more alkaline and acid media, respectively. Therefore, reusability tests of these catalysts were performed in their optimal reaction media. 5 % Pd/TiO₂ showed some activity loss in alkaline media but remained relatively stable. Conversely, 5 % Pd/CNT BM experienced significant activity loss in acidic media but was highly stable in alkaline conditions. [Display omitted] •Palladium-based catalysts were used for degradation of 4-chlorophenol•The reactional media influences the catalytic hydrochlorination of 4-chlorophenol•The degradation of 4-chloropenol was achieved due to the breakage of CCl bond•In an alkaline media no deactivation of the catalyst was registered