Guangyue Xu

Depolymerization of lignin via a non-precious Ni–Fe alloy catalyst supported on activated carbon

Lignin primarily composed of methoxylated phenylpropanoid subunits is an abundant biomass that can be used to produce aromatics. Herein, a series of non-precious bimetallic Ni–Fe/AC catalysts were prepared for efficiently depolymerizing lignin. When organosolv birch lignin was used to determine the efficiency of the catalysts in methanol solvent, the Ni1–Fe1/AC (the ratio of Ni and Fe was 1 : 1) achieved the highest total yield of monomers (23.2 wt%, mainly propylguaiacol and propylsyringol) at 225 °C under 2 MPa H2 for 6 h. From GPC analysis, it is also proved that lignin was efficiently depolymerized. The Ni–Fe alloy structure was formed according to XRD, HRTEM, H2-TPR and XPS characterization. Based on the model compounds’ tests, the Ni1–Fe1/AC catalyst showed high efficiency in ether bond cleavage without hydrogenation of aromatic rings which could be attributed to the synergistic effect of Ni and Fe on the alloy structure. The total yield of monomers by using the Ni1–Fe1/AC catalyst reached 39.5 wt% (88% selectivity to PG and PS) when birch wood sawdust was used as the substrate.

Selective hydrodeoxygenation of lignin-derived phenols to alkyl cyclohexanols over a Ru-solid base bifunctional catalyst

Cyclohexanol and alkyl cyclohexanol are important chemical intermediates. It is meaningful to prepare cyclohexanols from non-fossil-based biomass. Here we report Ru/ZrO2–La(OH)3, a metal-solid base bifunctional catalyst, to show its excellent performance on the partial hydrodeoxygenation of lignin-derived phenols. Guaiacol could be converted to cyclohexanol with a 91.6% yield in water. Alkyl phenols with one or two methoxy groups were converted into alkyl cyclohexanols with yields over 86.9%. The catalyst had good activity of removing a methoxy group and retaining a hydroxyl group. In this catalyst, Zr and La interacted with each other to form a mixed (hydr)oxide, thus making ZrO2–La(OH)3 a stable support. Ru was highly dispersed on the ZrLa support. The pathway from guaiacol to cyclohexanol was investigated and proposed as two parallel ways, demethoxylation followed by hydrogenation (I), the saturation of the aromatic ring through hydrogenation and then demethoxylation through direct hydrogenolysis (II).

Catalytic conversion of Jatropha oil to alkanes under mild conditions with a Ru/La(OH)3 catalyst

The long-chain alkanes obtained from the hydrodeoxygenation of plant oils are ideal substitutes for diesel. In this work, a new efficient catalytic system was established for the conversion of plant oil to long-chain alkanes under mild conditions with a bi-functional Ru/La(OH)3 catalyst. The hydrodeoxygenation of stearic acid was performed in an autoclave with Ru-based catalysts with different supports (HZSM-5, ZSM-5, SiO2–Al2O3, SiO2, ZrO2, Mg(OH)2, La(OH)3, and La2O3). Among these catalysts, Ru supported on basic La(OH)3 showed a remarkable catalytic performance for the reaction. Over 98% of long-chain alkanes were obtained with 100% conversion of stearic acid at 200 °C and 4 MPa H2. When crude Jatropha oil was hydrogenated, about 80.7 wt% of long chain alkanes were obtained under the optimized conditions (200 °C, 4 MPa H2, 8 h). The high efficiency of the Ru/La(OH)3 catalyst could be due to a co-effect of the high hydrogenation activity of Ru and the basic La(OH)3 support which can attract the acidic raw material. Additionally, the Ru/La(OH)3 catalyst was recycled four times and maintained a good activity and stability. The reaction pathway was also explored by using stearic acid as a model compound. Hydrogenation–decarbonylation could be the main pathway to produce n-heptadecane, which has one carbon atom less than stearic acid.

Selective Hydrogenation of Phenol to Cyclohexanone over Pd–HAP Catalyst in Aqueous Media

The production of pure cyclohexanone under mild conditions over catalysts with high reactivity, selectivity, compatibility, stability, and low cost is still a great challenge. Here we report a hydroxyapatite‐bound palladium catalyst (Pd–HAP) to demonstrate its excellent performance on phenol hydrogenation to cyclohexanone. Based on catalyst characterization, the Pd nanoclusters (≈0.9 nm) are highly dispersed and bound to phosphate in HAP. Only basic active sites on HAP surface are detected. At 25 °C and ambient H2 pressure in water, phenol can be 100 % converted into cyclohexanone with 100 % selectivity. This system shows a universal applicability to temperature, pH, solvent, low H2 purity, and pressure. The catalyst reveals high stability to be recycled without deactivation or morphology change; and Pd nano‐clusters barely aggregate even at 400 °C. During the reaction, HAP adsorbs phenol, and Pd nanoclusters activate and spillover H2. The mechanism is also investigated, proposed, and verified.