Yubo Ma

Production of 5-hydroxymethylfurfural from fructose by a thermo-regulated and recyclable Brønsted acidic ionic liquid catalyst

In this work, a thermo-regulated recyclable catalytic system using ionic liquid [HO2CMMIm]Cl as the catalyst and isopropanol as the solvent has been demonstrated to be effective for the dehydration of fructose to synthesize 5-hydroxymethylfurfural (HMF). The solubility of [HO2CMMIm]Cl ionic liquid in isopropanol is temperature-dependent, being miscible with isopropanol at a temperature range suitable for fructose dehydration (e.g., above 80 °C) while not soluble at lower temperatures such as room temperature. Temperature-responsive solubilization/precipitation of [HO2CMMIm]Cl in isopropanol renders the acidic ionic liquid an appealing thermo-regulated phase-switchable catalyst. Furthermore, the effects of various parameters including catalyst loading, fructose concentration, reaction time and temperature on the catalytic performance of fructose dehydration have been studied systematically. Under optimized reaction conditions, up to 91.2 mol% HMF yield could be obtained. Additionally, when the ionic liquid catalyst precipitated out after the reaction, the solvent can be simply decanted and [HO2CMMIm]Cl could be directly reused for the next run with freshly added solvent and substrate. It was found that [HO2CMMIm]Cl could be reused at least five times without considerable loss of activity. Furthermore, a kinetic analysis was carried out, indicating the activation energy for the reaction to be 62.1 kJ mol−1. This catalytic system can be envisioned to find applications in a wide range of acid-catalyzed reactions with facile, thermo-regulated catalyst recovery features.

Tandem hydroformylation and hydrogenation of dicyclopentadiene by Co3O4 supported gold nanoparticles

A co-precipitation method was used to prepare a series of Co3O4 supported gold nanoparticles (Au/Co3O4), which were subsequently evaluated on their performance for “one-pot” synthesis of tricyclodecanedimethylol (TDDMO) from dicyclopentadiene (DCPD). Characterization methods including FTIR, XPS and TG-DTA were performed on the Au/Co3O4 catalyst during the course of reaction to reveal that three distinct stages of catalysis occurred while the catalyst possessed different physiochemical properties. The “one-pot” synthesis of TDDMO was successfully realized with selectivity over 90% under relatively mild reaction conditions of 140–150 °C reaction temperature and 7–9 MPa pressure. Experimental data suggested that the catalytically active species might be a Co(CO)x(PPh)y complex where the presence of gold can assist the in situ reduction of Co3O4 to metallic cobalt under reaction conditions, thereby increasing the number of active sites. Another role of Au was proposed as facilitating hydrogenation of an in situ formed intermediate aldehyde, diformyltricyclodecanes (DFTD), to produce the final product TDDMO.

Efficient degradation of lignin in raw wood via pretreatment with heteropoly acids in γ-valerolactone/water.

The aim of this work was to study the degradation of lignin in raw wood via pretreatment with heteropoly acids as substitutes for traditional H2SO4 in γ-valerolactone/water. By optimizing catalyst concentration, reaction time and temperature, the optimal lignin degradation conditions are obtained (130 °C, 3 h and 20 mM silicotungstic acid). SEM and FTIR measurements demonstrated the efficient lignin degradation ability of HPAs in the GVL/H2O solvent, with negligible damage to cellulose within the raw wood. Furthermore, an elaborated enzymatic hydrolysis study of the thus obtained cellulosic feedstock revealed its suitability for enzymatic digestion, with great potential as starting material for the production of fermentable sugar from biomass in future biorefinery applications.

Kinetics of dicyclopentadiene hydroformylation over Rh-SiO2 catalysts

The hydroformylation of dicyclopentadiene (DCPD) to monoformyltricyclodecenes (MFTD) represents a key intermediate step in the conversion of the C5 fraction derived from the petrochemical process to value-added fine chemicals, for example, diformyltricyclodecanes and tricyclodecanedimethylol. Although both heterogeneous and homogeneous catalysts can catalyse this reaction, the heterogeneously catalysed pathway has received significantly less attention due to its lower catalytic activities. We demonstrate in this work that a low Rh loaded heterogeneous 0.1% Rh–SiO2 catalyst can present a similar performance relative to the homogeneous Rh(PPh3)Cl, a reference catalyst for this reaction. Furthermore, an extensive kinetic study of DCPD hydroformylation to MFTD using heterogeneous 0.1% Rh–SiO2 catalysts has been performed. A series of kinetic experiments was carried out over a broad range of conditions (temperature: 100–120 °C; pressure: 1.5–5 MPa; catalyst-to-reactant mass ratio: 0.02–0.05; PPh3 concentration: 5–12.5 g L−1). A kinetic analysis was carried out, indicating the activation energy for the reaction to be 84.7 kJ mol−1. DCPD conversion and MFTD yield could be optimised to be as high as 99% at 0.1% Rh loading, a DCPD/catalyst mass ratio of 25, a PPh3 concentration of 10 g L−1, a reaction time of 4 h and a reaction pressure of 4 MPa.

Enhanced Ru/Alumina catalyst via the adsorption-precipitation (AP) method for the hydrogenation of dimethyl maleate

Two methods, incipient wetness impregnation (IM) and adsorption-precipitation (AP) were used to prepare alumina-supported Ru catalysts. Using the selective hydrogenation of dimethyl maleate as a probe reaction, the obtained results demonstrated an enhanced catalytic activity with the AP method as compared to the IM technique. It was also found that higher hydrogenation activity was obtained with samples that were directly activated in H2 flow. In contrast, the activity decreased seriously when the catalyst samples were subjected to a calcination pretreatment prior to activation with H2 reduction, especially for the IM technique. Additional catalytic testings on Ru/Al(AP)-R with chlorine addition demonstrated that the catalytic activity was greatly decreased, suggesting that chlorine has a negative effect on the hydrogenation behaviors of Ru. Combined with the characterization results of XRD, H2-TPR, H2-TPD and XPS, the advantage of the AP method can be summarized as the following: this technique effectively eliminates chlorine, thus resulting in a better dispersion of Ru species and decreasing the negative influence of chlorine on Ru. A superior Ru/alumina catalyst can be obtained with the AP followed by direct activation with H2 reduction.

Hydroformylation of dicyclopentadiene over Rh catalysts supported on Fe2O3, Co3O4 and Fe2O3-Co3O4 mixed oxide

Rh catalysts supported on Fe2O3, Co3O4 and Fe2O3–Co3O4 mixed oxide were prepared by the co-precipitation method. The effect of the support on the performance of the Rh catalysts for the hydroformylation of dicyclopentadiene was investigated using X-ray photoelectron spectroscopy, H2-temperature-programmed reduction, H2-temperature-programmed desorption and Brunauer–Emmett–Teller analysis techniques. The results indicated that the Fe2O3–Co3O4 supported catalyst had a higher dispersion of Rh and thus more Rh+ sites. As a result, the Fe2O3–Co3O4 supported Rh catalyst exhibited higher activity compared with counterparts supported on Fe2O3 and Co3O4.