Guojun Lan

Enzyme confined in silica-based nanocages for biocatalysis in a Pickering emulsion

The encapsulation of lipase into the nanocages of FDU-12 and the amphiphilic modification of the surfaces of FDU-12 can concurrently be accomplished via a facile silylation method. The obtained lipase-loaded FDU-12 particles featuring superior biocatalytic activity and negligible enzyme leaching can serve as efficient stabilizers for a Pickering emulsion to enhance the performance of biphasic enzymatic reactions.

Direct Synthesis of Ruthenium‐Containing Ordered Mesoporous Carbon with Tunable Embedding Degrees by Using a Boric Acid‐Assisted Approach

Uniform ruthenium nanoparticles (1–2 nm) confined in ordered mesoporous carbon (Ru‐OMC) with various embedding degrees have been fabricated by using a boric acid‐assisted hard template method. The catalytic performance of Ru‐OMC catalysts was determined through the hydrogenation of toluene at 110 °C and 4.0 MPa. The effects of pore size and embedding degree on the catalytic performance were studied and compared with those of OMC‐supported ruthenium (Ru/OMC) catalysts with various pore sizes. The catalytic activities of embedding Ru‐OMC catalysts are much higher than those of supported Ru/OMC catalysts, which can be attributed to the strong interaction between ruthenium nanoparticles and the carbon support. Furthermore, the activities of Ru‐OMC catalysts are closely related to the embedding degree of ruthenium nanoparticles in the carbon matrix. The Ru‐OMC catalysts with an appropriate embedding degree affords a turnover frequency of up to 4.69 s−1 in toluene hydrogenation.

Improved catalytic performance of encapsulated Ru nanowires for aqueous-phase Fischer–Tropsch synthesis

Fischer–Tropsch (F–T) synthesis at low temperature has attracted a lot of research attention due to its thermodynamically favorable nature at low temperature. Herein, we report a highly efficient solid nanoreactor for low temperature liquid-phase F–T synthesis. The solid nanoreactor was fabricated by encapsulation of Ru–PVP nanowires in ethane–silica hollow nanospheres via a one-pot co-condensation method. Under similar reaction conditions, the solid nanoreactor shows higher activity (activity: 6.35 versus 5.96 molCO mol−1Ru h−1) and selectivity towards oxygenate products (41.3 versus 21.6%) than free Ru–PVP in aqueous F–T synthesis. The high activity and selectivity of the encapsulated Ru–PVP is mainly attributed to the low PVP/Ru ratio and the unique yolk–shell nanostructure in increasing the degree of exposure of the active sites. It was also observed that the selectivity towards C5–12 products could be increased to 63.8% in a water/cyclohexane biphasic system. Encapsulation not only gave rise to the quasi-homogeneous Ru–PVP with facile recycling ability, but also enhanced its activity and selectivity towards oxygenates.

Solid state synthesis of Ru–MC with highly dispersed semi-embedded ruthenium nanoparticles in a porous carbon framework for benzoic acid hydrogenation

A mesoporous ruthenium containing carbon Ru–MC-g catalyst with a semi-embedded uniform Ru particle distribution was synthesized by using a dry grinding method using nano-silica as a hard template. The structure and catalytic performance of the embedded Ru–MC-g catalysts were compared with those of the Ru–MC-i catalyst prepared via a wet impregnation method and the carbon supported Ru catalyst (Ru/MC). Among all the obtained catalysts, the Ru–MC-g catalyst prepared by the dry-grinding process shows excellent hydrogenation catalytic activity performance for the chemoselective hydrogenation of benzoic acid to cyclohexane carboxylic acid. The turnover frequency of the Ru–MC catalyst reaches ca. 2400 h−1 at 4 MPa, 120 °C, which is a 6 times improvement compared with that of supported Ru/MC catalyst. The dry-grinding process is expected to be easily scaled up for large-scale production of Ru-based catalysts.

Direct synthesis of nitrogen-doped mesoporous carbons for acetylene hydrochlorination

Nitrogen-doped ordered mesoporous carbon (N-OMC) catalysts were directly synthesized using SBA-15 as a hard template and sucrose as a carbon source. Urea, which was used as the nitrogen source, was carbonized with sucrose. A 3.6 wt% nitrogen doping of the carbon framework was achieved, with more than 70% of the nitrogen incorporated as quaternary nitrogen species. Only 0.2 wt% nitrogen doping, with only 32.7% quaternary nitrogen incorporation was obtained in an N-OMC catalyst (N-OMC-T) prepared using a two-step post-synthesis method. The acetylene hydrochlorination activities of N-OMC catalysts prepared via the one-step method were higher than that of the N-OMC-T catalyst because of the higher nitrogen loadings.

Activation of a Carbon Support Through a Two‐Step Wet Oxidation and Highly Active Ruthenium–Activated Carbon Catalysts for the Hydrogenation of Benzene

A two‐step liquid oxidation approach was developed for the activation of carbon materials. Following nitric acid treatment and subsequent liquid oxidation by a mild oxidant such as H2O2, the number of surface acidic functional groups was increased without destroying the physical structures of the carbon materials. Ruthenium catalysts supported on activated carbon prepared by this two‐step liquid oxidation method show significantly improved Ru dispersion and excellent catalytic performance in the hydrogenation of benzene. The dispersion of ruthenium and the catalytic performance of Ru/activated carbon increases monotonically with the amount of surface functional groups.

Enhancing the catalytic activity of Ru NPs deposited with carbon species in yolk–shell nanostructures

The synthesis of metal NPs with a well-defined size, shape and composition provides opportunities for tuning the catalytic performance of metal NPs. However, the presence of a stabilizer on the metal surface always blocks the active sites of metal NPs. Herein, we report an efficient method to remove the stabilizer on the metal surface via H2 pyrolysis with Ru–poly(amindoamine) encapsulated in silica-based yolk–shell nanostructures as an example. The CO uptake amount of Ru NPs increases sharply after H2 pyrolysis, indicating that the exposure degree of Ru NPs is increased. No aggregation of the colloidal Ru NPs occurs after H2 pyrolysis, which could be mainly assigned to the protection effect of C and N species formed on Ru NPs. The overall activity of Ru NPs in the yolk–shell nanostructure after the pyrolysis could reach as high as 20 300 mmol per mmol Ru per h in the hydrogenation of toluene, which is much higher than that of most reported Ru-based solid catalysts. It was found that the yolk–shell nanostructure could efficiently prevent the leaching of Ru NPs during the catalytic process. Ru NPs in the yolk–shell nanostructure could also catalyze the hydrogenation of benzoic acid and Levulinic acid with high activity and selectivity.

Yolk-shell nanospheres with soluble amino-polystyrene as a reservoir for Pd NPs

The fabrication of silica/polymer composites with high polymer content, high stability and unique nanostructures still remains a difficult task though they have wide potential applications in the field of sensing, catalysis, bio-imaging and so on. Herein, the synthesis of yolk–shell nanospheres with soluble amino-polystyrene as a core material (PS-NH2@mesoSiO2 YSNs) have been reported, which is achieved by successive nitration and reduction of polystyrene nanospheres (PS) confined in silica hollow shells. Both the thermal stability and anti-swelling ability of PS-NH2 in the core of yolk–shell nanospheres are greatly enhanced due to the confinement effect. PS-NH2@mesoSiO2 could be used as a reservoir for stabilizing Pd NPs. PS-NH2@mesoSiO2 YSNs with high amino content have high anti-swelling ability and result in Pd NPs with small particle size and high stability. Pd/PS-NH2@mesoSiO2 is an efficient catalyst for the selective hydrogenation of acetophenone (AP) to produce α-phenyl ethanol (PE). NH2 groups in the core of PS-NH2@mesoSiO2 yolk–shell nanospheres not only stabilize Pd nanoparticles but also provide basic surroundings for suppressing the hydrogenolytic splitting of the C–OH to improve the selectivity for α-phenyl ethanol.

Effect of pore structure of mesoporous carbon on its supported Ru catalysts for ammonia synthesis

Mesoporous carbon (MC) was prepared by a hard-template method and used as support for the preparation of a Ru-based ammonia synthesis catalyst, Ba-Ru-K/MC. N2 adsorption-desorption, scanning electron microscopy, and transmission electron microscopy were used to characterize the mesoporous carbon and its supported Ru catalysts. The effects of pore structure of the Ba-Ru-K/MC catalyst on its performance for ammonia synthesis were studied. The results show that the surface area of the mesoporous carbon material varies with the SiO2/C mass ratio and reaches the largest at 1.0 of SiO2/C. The catalytic activity of Ba-Ru-K/MC for ammonia synthesis increases with increased mesoporous surface area of the mesoporous carbon. The reaction rate of ammonia synthesis is 139 mmol/(gcat·h) at 425 °C, 10 MPa, and a gas hourly space velocity of 10000 h−1.

Easy synthesis of iron doped ordered mesoporous carbon with tunable pore sizes

Abstract Precise control of the pore sizes for porous carbon materials is of importance to study the confinement effect of metal particles because the pore size in nanosize range will decide the physical and chemical properties of the metal nanoparticles. In this paper, we report a new approach for the synthesis of iron doped ordered mesoporous carbon materials with adjustable pore size using Fe-SBA-15 as hard template and boric acid as the pore expanding reagent. The pore size can be precisely adjusted by a step of 0.4 nm in the range of 3–6 nm. The carbonization temperature can be lowered to 773 K due to the catalytic role of the doped iron. The present approach is suitable for facile synthesis of metal imbedded porous carbon materials with tunable pore sizes.