Huazhang Liu

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.

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.

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.

Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst

A series of high surface area graphitic carbon materials (HSGCs) were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x (x is the ball-milling time in hour) catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

Preparation of efficient ruthenium catalysts for ammonia synthesis via high surface area graphite dispersion

Abstract High surface area graphite (HSAG) was tested as a support of ruthenium catalyst for ammonia synthesis. As it is in the form of fine powder, it can be dispersed in the ruthenium precursor solution achieving high dispersion of Ru and efficiency. The surface area, porosity, crystalline structure of support, morphology, dispersion of Ru, desorption of H2 and N2 and methanation of the catalyst were investigated by N2 physisorption, XRD, SEM, TEM and TPD/TPSR techniques. The results show that higher ammonia synthesis rates of the HASG catalyst compared to activated carbon can be achieved with the assistance of ultrasonic treatment. As expected, the methanation rate over HSAG is much lower than that of activated carbon over the whole temperature range studied.

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.