Peroxidation Activation of Ethane with Hydrogen and Oxygen by Au-Based MWW Zeolite Acidic Catalyst

The oxidative activation of ethane to produce ethene and oxygenates has attracted wide interest. An alternative reaction process for peroxidation activation of ethane in the presence of H₂ and O₂ at mild temperatures is performed by Au-based MWW zeolite acidic catalysts to produce acetic acid and ethene without the CO_x generation. A nanometal oxide encapsulated Au nanoparticle catalyst was synthesized by homogeneously distributing Au nanoparticles on the atom-planting introduced TiO_x or SnO_x in the hydroxyl group of MWW zeolite. The Au cluster size, the catalyst Brønsted, and Lewis acidity determine the stability of in situ generated H₂O₂ and control acetic acid and ethene selectivity. We propose a heterogeneous catalytic mechanism in which the Au cluster can promote ethane activation through α-H cracking of the C–H bond; this activated ethane then interacts with hydroperoxyl radicals (HOO*) on the Au cluster surface or the hydroxyl radicals (OH*) from decomposition of the in situ generated H₂O₂, and ethylhydrogen peroxide and ethanol are formed as key reaction intermediates for acetic acid. The Au surface OH* can promote β-H scission of ethane dehydrogenation for ethene. The Brønsted acid and Au–Ti in aluminosilicate MWW zeolite can activate ethane at 623 K and stabilize hydroperoxyl radicals with an acetic acid productivity of 4.04 mol g_Au^–1 h^–1 and 87.08% selectivity. At 823 K, Au–Sn in deborosilicate MWW zeolite promotes ethane dehydrogenation to ethene with a productivity of 4.33 mol g_Au^–1 h^–1 and 98.5% selectivity.