High yield production of 1,4-cyclohexanediol from lignin derived 2,6-dimethoxybenzoquinone via Raney NiMn catalyst in hydrogen free conditions

Transformation of lignin to valuable chemicals via sustainable pathways is recognized as one of the most efficient ways to explore its value and replace the nonrenewable petroleum resource. In this work, an environmental-friendly transfer hydrogenation process has been developed to convert lignin derived 2,6-dimethoxybenzoquinone to 1,4-cyclohexanediol. Compared with previous work under hydrogen pressure (30 bar), this process uses isopropanol as both solvent and hydrogen donor, which significantly simply the operation process. The core of this study is the design and preparation of Mn modified Raney Ni catalysts by ball milling process. A series of Raney NiMn catalysts with different ball milling time and Mn content were prepared and investigated. Characterizations by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscope (TEM) etc. showed that NiMnAl alloy was formed during the ball milling process and then transformed to NiMn alloy after treatment by aqueous NaOH. After optimization, a yield as high as 86.1% could be achieved for 1,4-cyclohexanediol at 200 °C in only 1 h.