Conversion of Methane to Methanol with a Bent Mono(μ- oxo)dinickel Anchored on the Internal Surfaces of Micropores

摘要

The oxidation of methane to methanol is a pathway to utilizing this relatively abundant, inexpensive energy resource. Here we report a new catalyst, bent mono(μ-oxo)dinickel anchored on an internal surface of micropores,which is active for direct oxidation. It is synthesized from the direct loading of a nickel precursor to the internal surface of micropores of ZSM5 following activation in O_2. Ni 2p_(3/2) of this bent mono(μ-oxo)dinickel species formed on the internal surface of ZSM5 exhibits a unique photoemission feature, which distinguishes the mono(μ-oxo)dinickel from NiO nanoparticles. The formation of the mono(μ-oxo)dinickel species was confirmed with X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). This mono(μ-oxo)dinickel species is active for the direct oxidation of methane to methanol under the mild condition of a temperature as low as 150 °C in CH_4 at 1 bar. In-situ studies using UV-vis, XANES, and EXAFS suggest that this bent mono(μ- oxo)dinickel species is the active site for the direct oxidation of methane to methanol. The energy barrier of this direct oxidation of methane is 83.2 kJ/mol.