Gas phase hydrodechlorination of CCl4 over Pd–Cu and Pd–Fe bimetallic catalysts supported on an AlF3 matrix

Abstract

Two bimetallic catalytic systems composed of Pd–Cu and Pd–Fe supported over AlF3 were prepared by the sol–gel method and characterised by BET, X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (P-XRD). Analysis of the XPS and P-XRD data showed that the surface of these bimetallic catalysts may be described as Pd0–CuI and Pd0–FeIII hydroxides. The gas phase hydrodechlorination reaction (HDC) of CCl4 over these bimetallic catalysts showed that the presence of CuOH and Fe(OH)3 altered their catalytic activity, selectivity and product distribution compared to their monometallic Pd/AlF3 analogue. The bimetallic catalysts showed a very high selectivity for the formation of C1-products (CHCl3, CH2Cl2 and CH3Cl) in contrast with the tendency shown by the monometallic Pd/AlF3 analogue of forming coupled C2–C5 products. Interestingly, the pore-controlled version of the Pd–Fe*/AlF3 catalyst showed a greater efficiency favouring the formation of CHCl3 and CH2Cl2 compared with its Pd–Fe/AlF3 analogue which predominantly favoured the formation of CH3Cl. The effect of temperature, in the range of 458–513 K, and time on stream on the catalytic performance of the bimetallic catalysts in terms of percentage conversion, reaction rate and product distribution are discussed.