Dehydrogenation of ethane to ethylene via radical pathways enhanced by alkali metal based catalyst in oxysteam condition

摘要

The dehydrogenation of ethane to ethylene in the presence of oxygen and water was conducted using Na2WO4/SiO2 catalyst at high temperatures. At 923 K, the conversion rate without water was proportional to ethane pressure and a half order of oxygen pressure, consistent with a kinetically relevant step where an ethane molecule is activated with dissociated oxygen on the surface. When water was present, the ethane conversion rate was drastically enhanced. An additional term in the rate expression was proportional to a quarter of the oxygen pressure and a half order of the water pressure. This mechanism is consistent with the quasi-equilibrated OH radical formation with subsequent ethane activation. The attainable yield can be accurately described by taking the water contribution into consideration. At high conversion levels at 1073 K, the C2H4 yield exceeded 60 in a single-pass conversion. The C2H4 selectivity was almost insensitive to the C2H6 and O-2 pressures. (c) 2016 American Institute of Chemical Engineers AIChE J, 63: 105-110, 2017