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A novel, eco‐friendly direct graphite exfoliation method was developed using 1‐allyl‐pyridinium‐based ionic liquids (ILs) under microwave irradiation. Exfoliated graphene comprising a few layers was prepared from graphite using 1‐allyl‐pyridinium nitrate under 300 W microwave irradiation for 10 min, which was characterized by X‐ray diffraction, Raman spectroscopy, and X‐ray photoelectron spectroscopy. Density functional theory calculations indicated that the combination of the cations and anions in the ILs led to improved adsorption on the graphite surface. High‐power microwave irradiation can also allow cations to intercalate easily between the graphite layers and increase the efficiency of graphite exfoliation. Solid acid catalysts were prepared from exfoliated graphene via oxidation and sulfonation. The catalytic activity was evaluated for the saccharification of cellulose, where the highest monosaccharide yield of 15.9% was obtained after 24 h at 140°C with a cellulose/solid acid catalyst/water ratio of 0.1/0.05/3 (g/g/g). This performance was superior to that of several commercial catalysts. The magnetic solid acid catalyst which was prepared to facilitate separation from cellulose residue showed constant durability in three activity tests. [ABSTRACT FROM AUTHOR]

Aiming at enhancing the coke resistance of Ni-based catalysts, the Nd-doped Ni@A 2 O 3 core-shell catalysts were prepared and their catalytic performance was evaluated in the steam reforming of acetic acid (SRAA). The catalysts were characterized by BET, XRD, XRF, HRTEM, H 2 -TPR, NH 3 -TPD, and DTG. The catalytic performance was greatly enhanced by the incorporation of Nd, with decreased yields of CO, CH 4 , and acetone, increased yield of CO 2 , and remarkable carbon resistance. The decoking behavior of the spent catalyst was elucidated by H 2 O18-TSD. A low reaction temperature facilitates the formation of amorphous carbon, leading to catalyst deactivation. The decoking ability of the catalyst is greatly improved by the Nd incorporation but is also catalyzed by the exposed Ni surface. The Ni0.01Nd@Al catalyst greatly balanced the exposed Ni surface and the mobile lattice oxygen, showing the highest catalytic activity, lowest coke deposition, and superb decoking ability. • OSC was introduced to Ni@Al 2 O 3 core-shell catalyst by doping Nd. • Hydrogen yield was enhanced by Nd incorporation with remarkable coke resistance. • Low temperatures induced the formation of amorphous carbon. • Lattice-oxygen-involved surface reactions promoted coke removal and water dissociation. • Both the Ni and lattice oxygen affected the water decoking behavior. [ABSTRACT FROM AUTHOR]

Graphene oxide, which exhibits extraordinary acidic properties and a high theoretical surface area, is a good candidate for the catalytic transformation of biomass resources to valuable chemicals and biofuels. In this study, graphene oxide was prepared through various graphite oxide exfoliation methods, including sonication, microwave irradiation, and freeze-thaw cycling, and the activity of the prepared catalysts was evaluated in the saccharification of cellulose. The results indicated that graphene oxide prepared via these methods exhibited superior catalytic performances compared to graphite oxide; however, no significant difference in the catalytic activity of the graphene oxide catalysts was observed based on the exfoliation method used. Therefore, we proposed that thinning of graphite oxide improves its catalytic activity by increasing the contact efficiency between the substrate and the catalyst; however, this is not dependent on the exfoliation method used to prepare the graphene oxide. [ABSTRACT FROM AUTHOR]

A process of chemical activation with phosphoric acid from coconut shell in air to produce activated carbon was developed. The effects of various preparation parameters on the porous texture and surface characteristics were investigated by means of the nitrogen physisorption, Fourier transform‐infrared spectra (FT‐IR), and X‐ray photoelectron spectroscopy (XPS). The adsorption capacities of activated carbon for chromium, lithium, and cesium were also investigated. The surface modification of activated carbon using nitric acid was performed to enhance the adsorption capacities, and the relationship between the adsorption capacities and the surface functional groups was investigated. The oxygen‐containing functional groups on the surface of an activated carbon played a more important role than its textural structure in adsorption of metal ions, especially cesium ion. [ABSTRACT FROM AUTHOR]

Graphene oxide, which exhibits extraordinary acidic properties and a high theoretical surface area, is a good candidate for the catalytic transformation of biomass resources to valuable chemicals and biofuels. In this study, graphene oxide was prepared through various graphite oxide exfoliation methods, including sonication, microwave irradiation, and freeze-thaw cycling, and the activity of the prepared catalysts was evaluated in the saccharification of cellulose. The results indicated that graphene oxide prepared via these methods exhibited superior catalytic performances compared to graphite oxide; however, no significant difference in the catalytic activity of the graphene oxide catalysts was observed based on the exfoliation method used. Therefore, we proposed that thinning of graphite oxide improves its catalytic activity by increasing the contact efficiency between the substrate and the catalyst; however, this is not dependent on the exfoliation method used to prepare the graphene oxide. [ABSTRACT FROM AUTHOR]

A series of mesoporous carbon‐based solid acid catalysts were prepared using tannic acid (C76H52O46), a polyphenol compound, as starting carbon materials and SBA‐15 as silica template. The tannic acid catalysts were characterized by use of N2 Adsorption‐Desorption Isotherm, XRD, FTIR, XPS, and titration method. Phenolic hydroxyl group with weak acidity was confirmed as main functional groups in these catalysts based on characterization using FT‐IR and XPS. The catalysts were tested in saccharification of cellulose. Effects of different preparation parameters of catalyst were correlated to its saccharification activity: (a) oxidation using H2SO4 was important factor determined the high catalytic activity of catalysts, proved by comparison of catalytic activity of catalysts after treatment in concentrated H2SO4 and parent materials lacking the functionalization, (b) higher carbon coating also promoted good catalytic activity since it has higher relative percentage of acid functional groups based on XPS measurement, and (c) catalyst that treated by short oxidation time (2 h) could exhibit higher catalytic activity compared with catalysts that treated by longer oxidation time. With a ratio of catalyst/substrate: 0.5/1 (g/g) at 180°C for 1 h, glucose yield and conversion of 31.45 and 53.86% could be obtained. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 850–860, 2018 [ABSTRACT FROM AUTHOR]

A series of sulfonated mesoporous carbon-based catalysts with intact silica template (MC) were prepared through incomplete carbonization of sucrose followed by sulfonation. The MC catalysts were characterized by use of Fourier Transform-infrared spectra, N2 adsorption-desorption, and titration method. The effects of preparation conditions such as carbonization temperature, amount of carbon precursor, sulfonation time, and temperature on the structural and acidic properties of the catalysts were investigated. Preparation conditions such as amount of carbon precursor, sulfonation time, and temperature significantly influenced the surface area and acidic properties of MC catalysts. The activity of prepared catalysts in saccharification was tested using cellulose and rice straw as substrates and high saccharification yield can be obtained using these catalysts. In saccharification of cellulose without pretreatment, the highest yield of 25.2% of C6 monosaccharide can be attained after reaction at 180°C for 3 h. In saccharification of rice straw, the total monosaccharide yield of 43.4% can be achieved after reaction at 150°C for 1 h. In addition, it was found that despite the versatility of mesoporous structure in varied chemical reactions has been confirmed, acid amount was the most important property that determined the effectivity of cellulose saccharification. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 574-581, 2016 [ABSTRACT FROM AUTHOR]

The first part of this paper deals with the morphology of the MoS2 phase and its oxide precursor, the MoO3 phase, mainly from a geometrical point of view. After giving a brief review of the literature describing the structure of these compounds, Mo densities in both phases were calculated along various crystallographic planes. Further, using structural models recently proposed by others, Mo densities in MoS2 were also calculated in the case of an epitactic growth on γ-Al2O3 and TiO2 model surfaces. Then, the calculated Mo densities were compared with experimental results (Mo density when HDS activity is maximal) previously obtained for catalysts constituted of MoS2 supported on a low SSA TiO2, a high SSA TiO2 and a conventional γ-alumina. It was suggested that either on alumina or titania the MoS2 phase is growing as (100) MoS2 planes. However, while on the alumina the optimal MoS2 phase might be constituted of dispersed MoS2 slabs covering only a part of the alumina surface (2.9–3.9 Mo atoms/nm2), on titania the optimal MoS2 phase might be constituted of a uniform MoS2 monolayer (5.2 atoms/nm2 for the high SSA titania, which is equal to the Mo density of a perfect MoS2 (100) plane). This difference may originate in the creation of a 'TiMoS' phase enhancing the S atoms mobility over Mo/TiO2-sulfided catalysts. Indeed, while in the case of a γ-alumina carrier the active sites (labile S atoms) are located on the edge of MoS2 slabs making the ratio Moedge/Mototal a crucial parameter for the catalytic performances, in the case of a titania carrier the labile sulfur atoms might be statistically distributed all over the TiMoS active phase. Further, the higher Mo density observed over the high SSA titania (5.2 atoms/nm2) when compared to that over the low SSA titania (4.2 atoms/nm2) was supposedly due to the pH-swing method advantageously used to prepare the former carrier. Indeed, this method allows giving a solid with enhanced mechanical properties providing a good stability to the derived catalysts under experimental conditions. In addition, this TiO2 carrier exhibits a great homogeneity, with a surface structure substantially uniform, which might be adequate for a long-range growth of (100) MoS2 slabs. [ABSTRACT FROM AUTHOR]

The first part of this paper is a short review of the [sup 35]S radioactive tracer methods developed in recent years. Then, the experimental results obtained so far on Mo/Al[sub 2]O[sub 3] catalysts are compared with computer simulation results recently claimed in order to elucidate the coordinatively unsaturated site (CUS) creation/replenishment/ regeneration mechanism over MoS[sub 2] crystallites. The computer simulations allowed us to pre-select thermodynamically acceptable mechanisms among a set of suggested ones. Then, by comparison of the calculated activation energies with the [sup 35]S experiments results we could further validate the most probable mechanism. This mechanism involved the dissociative adsorption of an H[sub 2] molecule on the metallic edge of a MoS[sub 2] crystallite surface with further creation of a CUS by release of one H[sub 2]S molecule in the gas phase. Both laboratory and computer simulated experiments permitted to calculate the activation energy for the H2S liberation reaction. In both cases, this energy was about 10- 12 kcal/mol, confirming the accuracy of the proposed mechanism. Moreover, the calculated activation energy of the rate-limiting step for the creation of one CUS by the proposed mechanism was about 23 kcal/mol, which was also in good agreement with the experimental activation energy of the dibenzothiophene (DBT) hydrodesulphurisation (HDS) reaction (typically about 20- 22 kcal/mol). This correlation indicated that the DBT HDS reaction rate might be intrinsically governed by the CUS formation/replenishment process, i.e. that the vacancy formation process is a crucial parameter in the global HDS reaction mechanism. Nevertheless, in the case of the 4,6-dimethyl DBT (4,6-DMDBT) HDS reaction, the experimental activation energy is higher (approx. 30 kcal/mol), confirming that external parameters induced by the 4,6-DMDBT-specific properties themselves are likely to play an important role in the reaction process, in addition to the ones intrinsic to the catalytic phase. [ABSTRACT FROM AUTHOR]

In order to investigate the behavior of sulfur on sulfided Ni-Co-Mo/Al2O3 catalyst in the ultra deep hydrodesulfurization (HDS), a novel radioactive 35S tracer method was developed. Both radioactive 35S-labeled elemental sulfur and dibenzothiophene (DBT) were used to label the catalyst under the practical HDS, and then HDS reactions of DBT of 0.001–1.0 wt.% (content of sulfur: ca. 2–200 ppm) were carried out over the 35S-labeled catalyst at 260 °C and under 5.00 MPa. By tracing the changes in the radioactivity of formed [35S]H2S, the behavior of sulfur on the catalyst was determined. Either [35S]S or [35S]DBT can be used to label the catalyst well and the behavior of sulfur on the catalyst did not change with the type of 35S agent. The release rate of [35S]H2S from 35S-labeled catalyst in the HDS of DBT became remarkably slow when the concentration of DBT decreased to less than 0.01 wt.%. The amount of labile sulfur participating in the HDS of DBT also decreased with decreasing the concentration of DBT. This indicates that the labile sulfur on the catalyst is not uniform and only some part but not all of labile sulfur participates in the ultra deep HDS. [Copyright &y& Elsevier]