Qinglei Meng

A new porous Zr-containing catalyst with a phenate group: an efficient catalyst for the catalytic transfer hydrogenation of ethyl levulinate to γ-valerolactone

Catalytic transfer hydrogenation (CTH) of ethyl levulinate (EL) to gamma-valerolactone (GVL) is a very attractive reaction in the field of biomass transformation. In this work, a new porous Zr-containing catalyst with a phenate group in its structure was prepared by the coprecipitation of 4-hydroxybenzoic acid dipotassium salt and ZrOCl2 (Zr-HBA) in water and characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N-2 adsorption-desorption, and Fourier transform infrared spectroscopy. The Zr-HBA was used as the catalyst for CTH of EL to GVL in the presence of isopropanol, and the effects of temperature, time, and the amount of the catalyst on the reaction were studied. It was found that Zr-HBA was very active for the reaction and a GVL yield of 94.4% could be achieved. Meanwhile, the Zr-HBA could be reused at least five times without a notable decrease in activity and selectivity. The main reason for the high catalytic activity of the Zr-HBA was that the existence of a phenate in the structure of Zr-HBA increased the basicity of the catalyst, which is favourable for the CTH of EL.

Porous Zirconium–Phytic Acid Hybrid: a Highly Efficient Catalyst for Meerwein–Ponndorf–Verley Reductions

The utilization of compounds from natural sources to prepare functional materials is of great importance. Herein, we describe for the first time the preparation of organic-inorganic hybrid catalysts by using natural phytic acid as building block. Zirconium phosphonate (Zr-PhyA) was synthesized by reaction of phytic acid and ZrCl4 and was obtained as a mesoporous material with pore sizes centered around 8.5 nm. Zr-PhyA was used to catalyze the mild and selective Meerwein-Ponndorf-Verley (MPV) reduction of various carbonyl compounds, e.g., of levulinic acid and its esters into γ-valerolactone. Further studies indicated that both Zr and phosphate groups contribute significantly to the excellent performance of Zr-PhyA.

Water-Enhanced Synthesis of Higher Alcohols from CO2 Hydrogenation over a Pt/Co3O4 Catalyst under Milder Conditions

The effect of water on CO2 hydrogenation to produce higher alcohols (C2-C4) was studied. Pt/Co3O4, which had not been used previously for this reaction, was applied as the heterogeneous catalyst. It was found that water and the catalyst had an excellent synergistic effect for promoting the reaction. High selectivity of C2-C4 alcohols could be achieved at 140 °C (especially with DMI (1,3-dimethyl-2-imidazolidinone) as co-solvent), which is a much lower temperature than reported previously. The catalyst could be reused at least five times without reducing the activity and selectivity. D2O and (13)CH3OH labeling experiments indicated that water involved in the reaction and promoted the reaction kinetically, and ethanol was formed via CH3OH as an intermediate.

Biomass-derived γ-valerolactone as an efficient solvent and catalyst for the transformation of CO2 to formamides

Efficient conversion of carbon dioxide (CO2) into valuable chemicals is a very attractive topic. Herein, we conducted the first work on the utilization of biomass-derived γ-valerolactone (GVL) as the solvent and catalyst for transformation of CO2 with various primary and secondary amines in the presence of phenylsilane (PhSiH3), and the corresponding desired formamides were produced with high yields without any additional catalyst. Systematic studies indicated that the lactone structure of GVL played a key role in the formation of the active silyl formates and the activation of N–H bonds in amines, thus leading to the excellent performance of GVL for the catalytic reactions.

One-pot conversion of carbohydrates into gamma-valerolactone catalyzed by highly cross-linked ionic liquid polymer and Co/TiO2

The acid catalytic conversion of carbohydrates into levulinate esters followed by metal catalytic hydrogenation is an important approach to obtain gamma-valerolactone (GVL) from biomass. In this work, we prepared the highly cross-linked polymer of divinylbenzene with acid ionic liquid (PDVB-IL) and supported Co on TiO2 (Co/TiO2), which were characterized by Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental analysis. It was demonstrated that the PDVB-IL polymer could efficiently catalyze the esterification reaction of furfuryl alcohol (FAL), 5-hydroxymethylfurfural (HMF), and fructose with ethanol to produce the intermediate ethyl levulinate (EL), and the EL in the reaction mixture was directly hydrogenated to GVL over the Co/TiO2 without requiring purification and with high yields.

Cooperative catalysis of Pt/C and acid resin for the production of 2,5-dimethyltetrahydrofuran from biomass derived 2,5-hexanedione under mild conditions

Conversion of biomass into 2,5-dimethyltetrahydrofuran (DMTHF), an excellent fuel additive, solvent, and industrial intermediate, is an important reaction in green chemistry. In this work, different combinations of supported metal catalysts and solid acids were investigated for the synthesis of DMTHF from biomass derived diketone (2,5-hexanedione, 2,5-HD). The results showed that commercial Pt/C and solid acid Amberlite®IR-120H had an excellent cooperative effect on the reaction. 2,5-HD could be converted into DMTHF with a yield up to 99% under milder conditions. Further experiments indicated that 2,5-hexanediol (2,5-HDO) is a key intermediate in the reaction. The catalyst system could be facilely recovered due to the heterogeneity and reused several times without notable change in the performance.

Free-radical conversion of a lignin model compound catalyzed by Pd/C

Efficient cleavage of a C–O bond in lignin and its model compounds is of great importance for transformation of lignin into fuel and value-added chemicals. In this work, we explored the transformation of a lignin model compound benzyl phenyl ether (BPE) at 150 °C by using Pd/C as the catalyst under an argon atmosphere in the presence of Na2CO3 and N-methyl-2-pyrrolidone (NMP). The effects of different reaction parameters such as the amounts of Pd/C, Na2CO3 and NMP as well as reaction times were investigated. It was found that Pd/C played a key role in the conversion of BPE. At the same time, Na2CO3 and NMP also promote the transformation effectively. The yields of phenol and toluene reached 71.6% and 50.4%, respectively. Analytical results of electron paramagnetic resonance (EPR) indicated that the reaction proceeded through a free-radical reaction mechanism. Control experiments indicated that direct pyrolysis of BPE was the main route to generate the target products.

Synthesis of ketones from biomass-derived feedstock

Cyclohexanone and its derivatives are very important chemicals, which are currently produced mainly by oxidation of cyclohexane or alkylcyclohexane, hydrogenation of phenols, and alkylation of cyclohexanone. Here we report that bromide salt-modified Pd/C in H2O/CH2Cl2 can efficiently catalyse the transformation of aromatic ethers, which can be derived from biomass, to cyclohexanone and its derivatives via hydrogenation and hydrolysis processes. The yield of cyclohexanone from anisole can reach 96%, and the yields of cyclohexanone derivatives produced from the aromatic ethers, which can be extracted from plants or derived from lignin, are also satisfactory. Detailed study shows that the Pd, bromide salt and H2O/CH2Cl2 work cooperatively to promote the desired reaction and inhibit the side reaction. Thus high yields of desired products can be obtained. This work opens the way for production of ketones from aromatic ethers that can be derived from biomass.

Efficient Transformation of Anisole into Methylated Phenols over High‐Silica HY Zeolites under Mild Conditions

Transformation of anisole (methoxybenzene), a typical component of bio‐oil, into phenol and methylated phenols was studied over HY zeolites with framework Si/Al ratios of 5, 15, 25, and 35. It was demonstrated that the amounts of Brønsted acid and Lewis acid sites, the ratio of Lewis acid and Brønsted acid sites, and the textural properties of the zeolites were all crucial parameters that influenced the catalytic performance. The Brønsted acid and Lewis acid sites of the zeolites catalyzed the reaction cooperatively and efficiently promoted the transmethylation. The hierarchical channel system with fully open micropore–mesopore connectivity was favorable to reduce the amount of coke generated.

Synthesis of Hierarchical Porous Metals using Ionic Liquid-Based Media as Solvent and Template

It was found that nanodomains existed in the ionic liquid (IL)-based ternary system containing IL 1-ethyl-3-methylimidazole tetrafluoroborate (EmimBF4 ), IL 1-decyl-3-methylimidazole nitrate (DmimNO3 ) and water, and the size distribution of the domains varied continuously with the composition of the solution. A strategy to synthesize hierarchical porous metals using IL-based media as solvent and template is proposed, and the hierarchical porous Ru and Pt metals were prepared by the assembly of metal clusters of about 1.5 nm using this new method. It is demonstrated that the metals have micropores and mesopores, and the size distribution is tuned by controlling the composition of the solution. Porous Ru was used for a series of hydrogenation reactions. It has an outstanding catalytic performance owing to its special morphology and structure.