Electrophilic chlorination of methane over superacidic sulfated zirconia

Catalytic chlorination of methane was studied over SO₄^2–/ZrO₂, Pt/SO₄^2–/ZrO₂, and Fe/Mn/SO₄^2–/ZrO₂ solid superacid catalysts. The reactions were carried out in a continuous flow reactor under atmospheric pressure, at temperatures below 240°C, with a gaseous hourly space velocity of 1000 ml/g h and a methane to chlorine ratio of 4 to 1. At 200°C with 30% chlorine converted the selectivity in methyl chloride exceeds 90%. At more elevated temperatures, the selectivity decreases but stays above 80% in methyl chloride at 225°C using the sulfated zirconia catalysts. The selectivity can be enhanced by adding platinum to sulfated zirconia catalysts. An iron and manganese-doped catalyst exhibited excellent selectivities at somewhat lower conversions. Methyl chloride is obtained at 235°C in selectivities greater than 85%. No chloroform or carbon tetrachloride is formed. The electrophilic insertion involves electron-deficient metal-coordinated chlorine into the methane C-H bond.Catalysis by solid superacids, 29. For part 28 see ref. [14].