Jinglei Cui

Water‐Promoted Hydrogenation of Levulinic Acid to γ‐Valerolactone on Supported Ruthenium Catalyst

A highly efficient and green process for the hydrogenation of biomass‐derived levulinic acid (LA) to γ‐valerolactone (GVL) has been developed. GVL was obtained in a yield of 99.9 mol % with a turnover frequency as high as 7676 h−1 in aqueous medium by using a Ru/TiO2 catalyst under mild reaction conditions (70 °C). The strong interaction between Ru and TiO2 facilitated both the dispersion of Ru nanoparticles and the stability of the catalyst. In addition, as solvent, water participated in the hydrogenation of LA, which was confirmed by an isotope‐ labeling experiment with D (D2O). Specifically, the H atom(s) in water took part in the hydrogenation of the CO group of LA, which promoted the catalytic activity and GVL yield remarkably.

One‐step Conversion of Furfural into 2‐Methyltetrahydrofuran under Mild Conditions

One-step direct conversion of biomass-derived furfural to 2-methyltetrahydrofuran was realized under atmospheric pressure over a dual solid catalyst based on two-stage-packed Cu-Pd in a reactor; this is the first report that one-step conversion of furfural resulted in high yield of 2-methyltetrahydrofuran (97.1 %) under atmospheric pressure. This strategy provided a successive hydrogenation process, which avoids high H2 pressure, uses the reactor efficiently, and eliminates the product-separation step. Therefore, it could enhance the overall efficiency as a result of low cost and high yield.

Efficient aqueous hydrogenation of levulinic acid to γ-valerolactone over a highly active and stable ruthenium catalyst

Efficient aqueous hydrogenation of levulinic acid over supported catalysts is of fundamental and industrial interest but is highly challenging. For Ru/γ-Al2O3 catalysts, the primary problems are low activity and stability that arose from the inhomogeneous dispersion of Ru and the unstable nature of γ-Al2O3 in water. In this work, an integrated strategy was proposed for developing a highly active and stable catalyst for aqueous hydrogenation of LA to GVL. By modification with 3-aminopropyltriethoxysilane (KH550), the abundant surface Al–OH groups of γ-Al2O3 were transformed into a stable Al–O–Si structure, while ruthenium active centres were bonded to a γ-Al2O3 surface via coordination with amino ligands of KH550. This modification favours the formation of highly dispersed Ru centres with an electron-rich state, leading to a superior activity at temperatures as low as 25 °C (GVL yield of 99.1%, TOF of 306 h−1) and high stability.

Conversion of carbohydrates to furfural via selective cleavage of the carbon–carbon bond: the cooperative effects of zeolite and solvent

Furfural is one of the most valuable biomass-derived platform molecules which is primarily produced from hemicellulose. It is of significant importance but still highly challenging to produce furfural from hexoses, which are extensively distributed in nature. In this paper, carbohydrates (cellulose, starch, inulin, maltose, sucrose, glucose and fructose) were transformed into furfural efficiently over Hβ zeolite in a γ-butyrolactone–water solvent. The key process for converting hexoses into furfural is the selective cleavage of the C–C bond in hexoses to pentoses. The Hβ zeolite was discovered to induce the formation of acyclic hexoses, and the synergy between Hβ and solvent enables the selective C–C bond cleavage of acyclic hexoses into pentoses and promotes the subsequent dehydration of pentoses into furfural. Furfural yields for converting fructose and glucose reached 63.5% and 56.5% under milder conditions (150 °C), respectively. Moreover, a favorable yield of 38.5% for furfural can be achieved by direct conversion of cellulose.

Direct conversion of carbohydrates to γ-valerolactone facilitated by a solvent effect

The carbohydrates (cellulose, starch, inulin, maltose, sucrose, glucose and fructose) were converted efficiently into γ-valerolactone (GVL) over combined H3PW12O40 and Ru/TiO2 catalysts under mild conditions. The basicity of oxygen-containing solvents had a remarkable effect on the acid strength of H3PW12O40, which resulted in great variation in the yield of GVL. H3PW12O40 was more effective in 20 vol% water/γ-butyrolactone than in pure water and other water/organic solvents (methanol, ethanol and 1,4-dioxane). GVL yields for inulin and fructose reached 70.5 mol% and 67.6 mol% respectively. Meanwhile, a GVL yield of 40.5 mol% was achieved for cellulose. In addition, a practical method for catalyst recycling and GVL separation was developed by adding sugar into the reaction mixture. H3PW12O40 and Ru/TiO2 maintained their activity after three recycling runs.

Conversion of Xylose to Furfuryl Alcohol and 2-Methylfuran in a Continuous Fixed-Bed Reactor

An efficient process was designed for the synthesis of furfuryl alcohol and 2-methylfuran from xylose using a continuous fixed-bed reactor over a catalyst combining Hβ zeolite and Cu/ZnO/Al2 O3 in γ-butyrolactone (GBL)/water as solvent. The cooperative effect of Hβ zeolite and GBL facilitated the dehydration of xylose and enhanced largely the furfural yield. The production of furfuryl alcohol and 2-methylfuran can be simply tuned by changing the hydrogenation temperature for furfural over the Cu/ZnO/Al2 O3 catalyst. The yield for furfuryl alcohol reached 87.2 % at 150 °C whereas a yield of 86.8 % was achieved for 2-methylfuran at 190 °C.

Role of alkali earth metals over Pd/Al2O3 for decarbonylation of 5-hydroxymethylfurfural

A series of Pd/Al2O3 catalysts with different alkali earth metals (Mg, Ca, Sr, Ba) and varying Sr loadings (1.8, 3.5, 5.3, 7 and 8.8 wt%) were investigated for 5-hydroxymethylfurfural (HMF) decarbonylation. The alkali earth metal and content were demonstrated to have profound influences on the metal dispersion, electron density of the metal, acid–base properties of the catalyst, and catalytic performance. The Pd3Sr/Al2O3 catalyst exhibited the highest initial activity and furfuryl alcohol selectivity, achieving a yield of 92%. The key to high decarbonylation selectivity is the suppression of hydrogenolysis and etherification side reactions through the attenuation of the acidity of catalysts. Successful catalytic activity not only lies in the increased metallic surface area, but is also affected by the adsorption properties of the carbonyl group and the poisoning CO produced. The catalytic activity is linearly correlated to the surface metallic area at low modifier loading over PdM/Al2O3 catalysts. But along with further increased metallic surface area over PdXSr/Al2O3, HMF conversion initially increased, reaching a plateau over Pd3Sr/Al2O3 and then decreased with increasing Sr loading. A synergistic effect between the Sr species and metallic Pd was proposed, which promoted the migration of carbonyl adsorption from the support to the surface Pd through the electron donation of Sr species to Al2O3 and metallic Pd.

Effect of hierarchical meso–macroporous structures on the catalytic performance of silica supported cobalt catalysts for Fischer–Tropsch synthesis

A series of meso–macroporous silica supports with the same macroporous diameter but different mesoporous diameters were prepared by introducing phase separation into a sol–gel process and used to prepare cobalt catalysts for Fischer–Tropsch synthesis. The mesoporous diameter could be controlled in the range 6.5–35.0 nm while the macroporous diameter was kept at approximately 500 nm. The mesoporous porosity of the meso–macroporous silica supports greatly influenced the size, reducibility and dispersion of cobalt nanoparticles, and therefore resulted in different catalytic performances for Fischer–Tropsch synthesis. The meso–macroporous catalyst with an appropriate mesoporous size of 8.5 nm displayed a higher catalytic activity due to the best combination of the Co dispersion and reduction degree. The product distribution strongly depended on the mesoporous diameter due to the following two reasons: 1) the difference in the H2/CO ratio on the active sites due to the diffusional limitations of CO in the mesopores; 2) the Co crystallite size effect. In addition, large pellet catalysts (800–1700 μm) exhibited similar product distributions to small pellet catalysts (180–250 μm), which indicated that the macropores played an important role in reducing internal diffusion limitations for large pellet catalysts.