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Lignin is an attractive renewable source of aromatics with a low effective hydrogen to carbon ratio (H/Ceff). The catalytic hydrodeoxygenation (HDO) of lignin-derived model compounds is a key strategy for lignin upgrading. In this work, the HDO of guaiacol, a typical lignin-derived compound, was carried out over metal–organic framework (MOF)-derived Ni-based catalysts. A monometallic Ni-MOF catalyst and different ratios of bimetallic NiMo-MOF catalysts were synthesized by a hydrothermal process, followed by a carbonization process. Among these catalysts, Ni3Mo1@C exhibited an excellent catalytic performance, affording a guaiacol conversion of 98.8% and a cyclohexanol selectivity of 66.8% at 240 °C and 2 MPa H2 for 4 h. The addition of Mo decreased the particle size of the spherical structure and improved the dispersion of metal particles. The synergistic effect between Ni and Mo was confirmed by various means, including ICP, XRD, SEM, TEM, and NH3-TPD analyses. In addition, the effect of the reaction temperature, time, and H2 pressure during the HDO process is discussed in detail. [ABSTRACT FROM AUTHOR]

A selected number of tetradentate N2Py2 ligand-supported ReO2+ complexes and a monodentate pyridine-supported ReO2+ complex have been investigated as catalysts for the deoxydehydration (DODH) of diols and polyols. In situ 1H NMR experiments showed that these N-donor ligand-supported ReO2+ complexes are only the pre-catalyst of the DODH reaction. Treatment of (N2Py2) ReO2+ with an excess amount of water generates an active species for DODH catalysis; use of the Re-product of this reaction shows a much shorter induction period compared to the pristine complex. No ligand is coordinated to the "water-treated" complex indicating that the real catalyst is formed after ligand dissociation. IR analysis suggested this catalyst to be a rhenium-oxide/hydroxide oligomer. The monodentate pyridine ligand is much easier to dissociate from the metal center than a tetradentate N2Py2 ligand, which makes the Py4ReO2+-initiated DODH reaction more efficient. For the Py4ReO2+-initiated DODH of diols and biomass-based polyols, both PPh3 and 3-pentanol could be used as a reductant. Excellent olefin yields are achieved. [ABSTRACT FROM AUTHOR]

CO2 hydrogenation to methanol was conducted using a set of activated carbon-supported Cu/ZnO/Al2O3 catalysts (CCZA) prepared by an incipient wetness impregnation approach. The effect of the Cu/Al ratio on the physicochemical properties of the catalysts, as well as their catalytic performance, were investigated. As Cu/Al ratio increased, the metallic Cu surface area displayed a reducing trend from 6.88 to 4.18 m2∙gcat−1, while the CO2 adsorption capacity exhibited an increasing trend. Meanwhile, aluminum content will have an important effect on the catalysts' reducibility and, thus, on their catalytic performance. The CCZA-2.7-de catalyst demonstrated the highest selectivity to methanol at 83.75% due to the excellent distribution and synergistic effect of copper and zinc. Although the CO2 conversion of CCZA-2.2-de and CCZA-3.5-de exceeded 10%, the CH3OH selectivity was less than 60%, which may be attributed to the larger particle sizes of ZnO and poor interactions in Cu–Zn. The present study offers a novel approach to increase the number of active sites, optimize the activated carbon-aided Cu/ZnO/Al2O3 catalyst's composition, and finally elucidate the mechanism for CO2 hydrogenation to methanol. [ABSTRACT FROM AUTHOR]