Shaojun Qing

Cu–Al Spinel Oxide as an Efficient Catalyst for Methanol Steam Reforming†

Cu-Al spinel oxide, which contains a small portion of the CuO phase, has been successfully used in methanol steam reforming (MSR) without prereduction. The omission of prereduction not only avoids the copper sintering prior to the catalytic reaction, but also slows down the copper-sintering rate in MSR. During this process, the CuO phase can initiate MSR at a lower temperature, and CuAl2O4 releases active copper gradually. The catalyst CA2.5-900, calcined at 900 °C with n(Al)/n(Cu) = 2.5, has a higher CuAl2O4 content, higher BET surface area, and smaller CuAl2O4 crystal size. Its activity first increases and then decreases during MSR. Furthermore, both fresh and regenerated CA2.5-900 showed better catalytic performance than the commercial Cu-Zn-Al catalyst.

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.

Microwave synthesis of cellulose/CuO nanocomposites in ionic liquid and its thermal transformation to CuO.

The purpose of this study is to develop a green strategy to synthesize the cellulose-based nanocomposites and open a new avenue to the high value-added applications of biomass. Herein, we reported a microwave-assisted ionic liquid route to the preparation of cellulose/CuO nanocomposites, which combined three major green chemistry principles: using environmentally friendly method, greener solvents, and sustainable resources. The influences of the reaction parameters including the heating time and the ratio of cellulose solution to ionic liquid on the products were discussed by X-ray powder diffraction, Fourier transform infrared spectrometry, and scanning electron microscopy. The crystallinity of CuO increased and the CuO shape changed from nanosheets to bundles and to particles with increasing heating time. The ratio of cellulose solution to ionic liquid also affected the shapes of CuO in nanocomposites. Moreover, CuO crystals were obtained by thermal treatment of the cellulose/CuO nanocomposites at 800 °C for 3 h in air.

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.

Effect of calcination temperature of starch-modified silica on the performance of silica supported Cu catalyst in methanol conversion

A series of starch-modified SiO2 (SSi-temp) were obtained by calcining the extrudate of SiO2 and starch at different temperatures and used as the support to prepare Cu catalysts (Cu/SSi-temp, 10%) by the impregnation method. The Cu catalysts were characterized by N2 sorption, FT-IR, TG, XRD, SEM and H2-TPR; their catalytic performance in methanol conversion was investigated in a fixed bed reactor. The results indicated that starch can reduce the removal rate of silanol groups (Si-OH) from the surface of the support during calcination and the surface silanol groups are beneficial to the dispersion of Cu species. The calcination temperature of starch-modified SiO2 exhibits a significant influence on the surface silanol (Si-OH) concentration, the surface area and porous structure of the support; as a result, it may be used to adjust the size of supported CuO crystal grains and dispersion of Cu species, which determine the performance of the silica supported Cu catalysts in methanol conversion.

Reshaping CuO on silica to generate a highly active Cu/SiO2 catalyst

Reduction–oxidation treatment [RO] of an impregnated CuO/SiO2 catalyst has been found to be effective in re-dispersing CuO particles on the support. During the process, CuO was actually reshaped within a confined area on silica, forming an annular morphology consisting of highly dispersed nano CuO particles. The reshaping might happen during the oxidation process following the reduction step, while no re-dispersion could be observed by applying the oxidation step alone. After activation with H2, the RO treated samples demonstrated improved catalytic activity for methanol decomposition. These findings clearly indicate that the “shape” of CuO can be memorized during the activation process, resulting in the formation of a specific Cu metal and thus demonstrating different catalytic activities. Such a memory effect correlates the catalytic performance with the characterization data of CuO directly, which has the potential to provide a convenient approach for further catalyst development.

Effect of zinc introduction on catalytic performance of ZSM-5 in conversion of methanol to light olefins

The effect of Zn on the catalytic performance of ZSM-5 in the methanol-to-olefin conversion was investigated. The samples were characterised by X-ray diffraction, N2 adsorption, FTIR, temperature-programmed desorption of ammonia and water, and Py-IR. The experimental results revealed Znmodified ZSM-5 to show a lower selectivity to light olefin at the higher reaction temperature of 520°C but a higher selectivity to light olefin at lower temperatures. As a comparison, the catalytic performance of Ca-modified ZSM-5 for the methanol conversion is also given. From the above results, it is concluded that Zn may play another role in the methanol conversion in addition to tuning the surface acidic property after modification.

A novel supported Cu catalyst with highly dispersed copper nanoparticles and its remarkable catalytic performance in methanol decomposition

Using starch modified SiO2 as the support, an efficient copper catalyst with superior catalytic performance for methanol decomposition can be obtained, suggesting the key role of the nature of the support in preparing Cu/SiO2 catalysts with stable and highly dispersed copper nanoparticles using an impregnation method.

Temperature dependence of Cu–Al spinel formation and its catalytic performance in methanol steam reforming

A series of Cu–Al spinel nanoparticles have been prepared by a green solid phase reaction method between 800 and 1200 °C. Characterization techniques show a strong temperature dependence of the textural and crystal properties, reduction behavior, and surface composition. It is illustrated that the prepared materials rich in Al were mixed spinel solid solutions having a surface Cu/Al ratio lower than the bulk. The samples have surface areas of 19.9–86.6 m2 g−1 with spinel crystallite sizes between 8.7 and 34.5 nm. The catalytic behavior of these spinel catalysts together with a reference Cu/γ-Al2O3 sample is studied in methanol steam reforming (MSR). By omitting the pre-reduction step, the Cu–Al spinel catalysts present an initial increase and then a gradual decrease of conversion rate with time on stream, which leads to enhanced catalytic performances compared to the conventionally adopted pre-reduction method. During the catalytic reaction, the catalyst is firstly activated in situ by non-spinel Cu2+ followed by the gradual release of more active Cu from the spinel structure. The in situ generated Cu species present high catalytic ability and simultaneously agglomerate to larger nanoparticles, which seem to be well stabilized by surface defect spinels rather than by γ-Al2O3. The sample obtained at 950 °C reveals the best catalytic performance, showing the highest activity and durability. In addition, several key points for a good spinel catalyst are proposed.

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.