Improvement of the stability of Hg/AC catalysts by CsCl for the high-temperature hydrochlorination of acetylene

Activated carbon-supported mercuric chloride (HgCl₂) is used as an industrial catalyst for acetylene hydrochlorination. However, the characteristic of easy sublimation of HgCl₂ leads to the deactivation of the catalyst. Here, we showed that the thermal stability of the Hg/AC catalyst can be evidently improved when CsCl is added into the Hg/AC catalyst. Compared with the pure Hg/AC catalyst, the sublimation rate of HgCl₂ from the Hg-Cs/AC catalyst decreased significantly and the Hg-Cs/AC catalyst showed better catalytic activity and stability in the reaction. This promoting effect is related to the existence of cesium mercuric chlorides (Cs_xHg_yCl_x+2y) highlighted by XRD, HR-TEM and EDX analyses. Thus, reacting HgCl₂ with alkali chlorides to form alkali-mercuric chlorides may be a key to design highly efficient and thermally stable mercuric chloride catalyst for hydrochlorination reactions.