Hydrodechlorination of tetrachloroethylene over sulfided catalysts: kinetic study

In this work, a commercial sulfided hydrotreatment catalyst (2.8% NiO, 13.5% MoO3, supported on γ-alumina, supplied by Shell) is compared with different iron sulfide based catalysts. These catalysts were prepared from a by-product (called red mud (RM)) of the bauxite leaching in the Bayer process. Two different activation procedures were tested, both based in dissolving the RM in an acid solution (HCl or HCl+H3PO4) followed by a precipitation with ammonia at pH=8 and calcining at 500 °C. All the catalysts were sulfided at 400 °C. The commercial catalyst was more active than the iron sulfide catalysts in all the range of space times tested. However, considering the low prize of the RM based catalysts, they could be an interesting alternative to the hydrotreatment catalysts. The selectivity for ethane was near 100% for all the catalysts tested. Kinetics results were successfully modeled with a Langmuir–Hinshelwood model, assuming that the chemisorption of hydrogen (considered as associative) and TTCE occurs over analogous active sites.