Tandem Hydrogenolysis–Hydrogenation of Lignin‐Derived Oxygenates over Integrated Dual Catalysts with Optimized Interoperations

Abstract

The efficient hydrodeoxygenation (HDO) of lignin‐derived oxygenates is essential but challenging owing to the inherent complexity of feedstock and the lack of effective catalytic approaches. A catalytic strategy has been developed that separates C−O hydrogenolysis and aromatic hydrogenation on different active catalysts with interoperation that can achieve high oxygen removal in lignin‐derived oxygenates. The flexible use of tungsten carbide for C−O bond cleavage and a nickel catalyst with controlled particle size for arene hydrogenation enables the tunable production of cyclohexane and cyclohexanol with almost full conversion of guaiacol. Such integration of dual catalysts in close proximity enables superior HDO of bio‐oils into liquid alkanes with high mass and carbon yields of 27.9 and 45.0 wt %, respectively. This finding provides a new effective strategy for practical applications.

Catalytic Hydrodeoxygenation of Lignin-Derived Oxygenates: Catalysis, Mechanism, and Effect of Process Conditions

“…In contrast, when employed in close proximity, where both the catalysts were in physical mixed state, complete conversion of guaiacol and more than 95% cyclohexane selectivity were observed. The enhanced HDO activity was attributed to the tandem catalysis action promoted by integrated catalysts …”

“…87,89 Even though the bifunctional catalysts are superior in the complex HDO process, their use in a tandem hydrogenolysis− hydrogenation reaction is challenging. To tackle this issue, Fang et al 104 investigated the applicability of integrated dual catalysts, in which one catalyst, WC/CS (CS: carbon sphere), was designed for C−O hydrogenolysis and the other, Ni/CNT (CNT: carbon nanotubes), for hydrogenation. At 300 °C and 30 bar H 2 partial pressure, ∼95% guaiacol conversion and 90% phenol selectivity were observed on the WC/CS catalyst.…”

“…The enhanced HDO activity was attributed to the tandem catalysis action promoted by integrated catalysts. 104 Bui et al 92 examined the role of support material on guaiacol HDO employing CoMoS supported on ZrO 2 , TiO 2 and the conventional γ-Al 2 O 3 . CoMoS/TiO 2 showed a mixed yield of cyclohexane and benzene.…”

Stable and Antisintering Tungsten Carbides with Controllable Active Phase for Selective Cleavage of Aryl Ether C–O Bonds

“…Selective hydrogenolysis of aryl ether C–O bonds in lignin-derived oxygenates to produce aromatic compounds such as phenol is an important and attractive process because it involves the transformation of lignocellulose into value-added chemicals for fossil energy substitution. , However, it remains challenging due to the strong bonding linkages and the competing side reactions, including the hydrogenation of arene, dehydroxylation and undesirable cracking of C–C bonds, resulting in a mixture of products with poor selectivities. , Guaiacol is the most widely considered model compound in lignin-derived oxygenates; it contains three kinds of C–O bonds, namely, Ar–OCH 3 (356 kJ mol –1 ), ArO–CH 3 (247 kJ mol –1 ), and Ar–OH (414 kJ mol –1 ) . Therefore, it is highly desirable to design a catalyst that can selectively cleave the C–O bonds in guaiacol to obtain the target product.…”