HYDROCHLORINATION OF ACETYLENE USING GOLD CATALYSTS - A STUDY OF CATALYST DEACTIVATION

A detailed study of the processes occurring during the deactivation of gold catalysts used for the acetylene hydrochlorination reaction is described. Catalyst deactivation is a common feature of supported metal chloride catalysts for this reaction, but in the case of HAuCl4/C catalysts the deactivation is not due to loss of Au from the catalyst during use. The effect of a range of parameters on the deactivation rate is discussed, including method of preparation of the HAuCl4/C catalyst, [Au] and reaction conditions (GHSV and temperature). Deactivated and fresh catalysts were characterised using 197An Mössbauer spectroscopy in combination with X-ray diffractometry, TGA, and BET surface area determinations. On the basis of this study, two deactivation processes have been identified. At low reaction temperatures, 60-100°C, deposition of carbonaceous residues is the predominant deactivation mechanism. However, at higher reaction temperatures, 120-180°C, the main deactivation process is ascribed to the reduction of Au(III), and possibly Au(I), to the less active Au(0) during the catalytic reaction. Consequently, for the experimental conditions investigated in this study, the optimum temperature for operating these catalysts is in the range 100-120°C when both these deactivation processes can be minimised. © 1991.