Liquid-phase chloroform hydrodechlorination catalyzed by Pd/TiO₂-Na

Chloroform (CLF) liquid-phase catalytic hydrodechlorination (HDC) using isopropanol as solvent and hydrogen source has been studied over Na-promoted and unpromoted titania-supported Pd catalysts, which were synthetized by wet-impregnation. The effect of the addition of NaOH on the catalytic activity and properties has been analyzed. The modification of the TiO₂ with NaOH improves the catalytic activity of the final palladium catalyst. Thus, a high final conversion for chloroform was obtained over Pd/TiO₂-Na (85.7%), in comparison to that over Pd/TiO₂ (14.7%) or Pd/TiO₂ + NaOH (37.0%). When NaOH was directly added to the reaction mixture, a negative effect was observed on the textural and metallic properties of the Pd/TiO₂ catalyst, decreasing the specific area BET from 73 to 61 m²/g and Pd dispersion from 16.4 to 10.5%. On the contrary, the same physicochemical properties remained almost identical within experimental error, in the recycled Pd/TiO₂-Na catalyst (around 68 m²/g and 24% for specific area BET and Pd dispersion, respectively), nonetheless, close to 40% of the sodium in the catalyst leaches during the reaction, but interestingly, the residual Na in the catalyst after its first use («2.6 wt%) was stable and enough to attain significant CLF conversion (»79.8%), which suggest an acceptable stability for this material.