The Hydrogenation of Aromatic Compounds under Mild Conditions by Using a Solid Lewis Acid and Supported Palladium Catalyst

High yield production of 1,4-cyclohexanediol and 1,4-cyclohexanediamine from high molecular-weight lignin oil

The complete utilization of all lignin depolymerization streams obtained from the reductive catalytic fractionation (RCF) of woody biomass into high-value-added compounds is a timely and challenging objective. Here, we present a catalytic methodology to transform beech lignin-derived dimers and oligomers (DO) into well-defined 1,4-cyclohexanediol and 1,4-cyclohexanediamine. The latter two compounds have vast industrial relevance as monomers for polymer synthesis as well as pharmaceutical building blocks. The proposed two-step catalytic sequence involves the use of the commercially available RANEY® Ni catalyst. Therefore, the first step involves the efficient defunctionalization of lignin-derived 2,6-dimethoxybenzoquinone (DMBQ) into 1,4-cyclohexanediol (14CHDO) in 86.5% molar yield, representing a 10.7 wt% yield calculated on a DO weight basis. The second step concerns the highly selective amination of 1,4-cyclohexanediol with ammonia to give 1,4-cyclohexanediamine (14CHDA) in near quantitative yield. The ability to use RANEY® Ni and ammonia in this process holds great potential for future industrial synthesis of 1,4-cyclohexanediamine from renewable resources.

Reaction Rate Acceleration of Cooperative Catalytic Systems: Metal Nanoparticles and Lewis Acids in Arene Hydrogenation

Employing two distinct catalysts in one reaction medium synergistically is a powerful strategy for activating less reactive substrates. Although the approach has been well-developed in homogeneous conditions, it remains challenging and rare in heterogeneous catalysis, especially under gas-liquid-solid multiphase reaction conditions. Here, we describe the development of cooperative and synergistic catalyst systems of heterogeneous Rh-Pt bimetallic nanoparticle catalysts, Rh-Pt/DMPSi-Al₂ O₃ , and Sc(OTf)₃ in the liquid phase for the hydrogenation of arenes under very mild conditions. Dramatic rate acceleration was achieved with cooperative activation. Remarkably, more challenging substrates that contained strong electron-donating groups and sterically hindered substituents were smoothly hydrogenated. Mechanistic insights into the cooperative activation of an aromatic substrate by heterogeneous metal nanoparticles and a soluble Lewis acid was obtained by kinetic studies and by direct observation of ¹ H and ⁴⁵ Sc NMR spectra.

Intensifying strategy of ionic liquids for Pd-based catalysts in anthraquinone hydrogenation

Pd–IL complex catalyst was first employed in anthraquinone hydrogenation. ILs are uniformly dispersed around Pd species, which adjust acidic sites, accomplish charge transfers, stretch CO bond lengths and promote occurrence of desirable reactions.

Comparative Study on the Hydrogenation of Naphthalene over Both Al2O3-Supported Pd and NiMo Catalysts against a Novel LDH-Derived Ni-MMO-Supported Mo Catalyst

Naphthalene hydrogenation was studied over a novel Ni-Al-layered double hydroxide-derived Mo-doped mixed metal oxide (Mo-MMO), contrasted against bifunctional NiMo/Al₂O₃, and Pd-doped Al₂O₃ catalysts, the latter of which with Pd loadings of 1, 2, and 5 wt %. Reaction rate constants were derived from a pseudo-first-order kinetic pathway describing a two-step hydrogenation pathway to tetralin (k ₁) and decalin (k ₂). The Mo-MMO catalyst achieved comparable reaction rates to Pd_2%/Al₂O₃ at double concentration. When using Pd_5%/Al₂O₃, tetralin hydrogenation was favored over naphthalene hydrogenation culminating in a k ₂ value of 0.224 compared to a k ₁ value of 0.069. Ni- and Mo-based catalysts produced the most significant cis-decalin production, with Mo-MMO culminating at a cis/trans ratio of 0.62 as well as providing enhanced activity in naphthalene hydrogenation compared to NiMo/Al₂O₃. Consequently, Mo-MMO presents an opportunity to generate more alkyl naphthenes in subsequent hydrodecyclization reactions and therefore a higher cetane number in transport fuels. This is contrasted by a preferential production of trans-decalin observed when using all of the Al₂O₃-supported Pd catalysts, as a result of octalin intermediate orientations on the catalyst surface as a function of the electronic properties of Pd catalysts.

Highly-efficient Ru/Al–SBA-15 catalysts with strong Lewis acid sites for the water-assisted hydrogenation of p-phthalic acid

A Ru/Al–SBA-15 catalyst with excess Lewis acid sites displayed excellent efficiency (100%), high cis-isomer selectivity (84%), and exceptional stability towards hydrogenation of p-phthalic acid in water.

Highly active electron-deficient Pd clusters on N-doped active carbon for aromatic ring hydrogenation

Pyridinic nitrogen species in N-doped active carbon (xN-AC) are responsible for high activity of ring hydrogenation via the formation of a high percentage of electron-deficient Pd clusters.

Palladium modified magnetic mesoporous carbon derived from metal–organic frameworks as a highly efficient and recyclable catalyst for hydrogenation of nitroarenes

Magnetic mesoporous carbon (Fe–MC) derived from MOFs as catalyst support to fabricate Pd nanoparticles based catalyst Fe@Pd–MC for hydrogenation of nitroarenes.