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  • Recent Studies on Single Site Metal Alkoxide Complexes as Catalysts for Ring Opening Polymerization of Cyclic Compounds
    Catal. Surv. Asia (IF 2.25) Pub Date : 2020-01-09
    Asgar Kayan

    Abstract The selection of the catalyst is central to being able to control features and to better understand microstructures of polymers. New single-site metal alkoxide catalysts allow chemists to prepare regio/stereo regular polymers or copolymers that meet increasingly demanding performance requirements. These catalysts produce high molecular weights polymers with narrow polydispersity indexes or living properties and essentially regular polymers in structures. This review includes the synthesis, activity, and mechanistic aspects of especially single-site metal alkoxide catalysts with examples from my previous studies and recently published similar articles, beginning with an extensive survey on the aluminum, titanium, zirconium, and tin catalysts used to make polyethers, polyesters, and their derivatives. This review also compares the effects of ligands, substituents on ligands, and central metal atoms on ROP reactions. This review will provide the basis for the researchers who seek the new synthesis and application of catalysts in the future. Graphic Abstract

    更新日期:2020-01-09
  • Efficient Photocatalytic Hydrogen Production Achieved by WO 3 Coupled with NiP 2 Over ZIF-8
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-12-04
    Zhiliang Jin, Yupeng Zhang

    The photo-catalyst WO3/NiP2@ZIF-8 was synthesized by modifying the WO3 with NiP2@MOFs structure. High H2 production was achieved (341.2 µmol and 11.3 times than pure WO3 after 5 h) and the catalytic property of WO3 was improved. The XRD, FESEM and TEM were used to characterize and analyze the crystalline phase structure, namely, WO3 has nanowire structure and good crystalline phase, meanwhlie, ZIF-8 exhibits regular dodecahedron morphology. The catalysts were characterized and analyzed by electrochemical, steady-state and transient state, those results show that the composite has more efficient charge separation effect and better electrical performance than single catalyst, which provides a reliable basis for relative higher H2 production activity. The band gap structure and elemental valence of the composite catalysts were calculated and analyzed by UV–Vis DR and XPS, respectively. The possible reaction equation and H2 production mechanism of WO3/NiP2@ZIF-8 in HER were proposed.

    更新日期:2019-12-04
  • Mechanistic Study of Catalase- and Superoxide Dismutation-Mimic Activities of Cobalt Oxide Nanozyme from First-Principles Microkinetic Modeling
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-12-03
    Sibei Guo, Yu Han, Ling Guo

    Cobalt oxide (Co3O4) has attracted considerable interest because of its high catalytic activity, especially for intrinsic catalase (CAT)-mimic and superoxide dismutation (SOD)-mimic activities. However, understanding of its catalytic mechanism from atomic or molecular level remains limited. Here, we propose base-like dissociative, acid-like dissociative and bi-hydrogen peroxide associative mechanisms of CAT-mimic activity, Langmuir–Hinshelwood (LH) and Eley–Rideal (ER) mechanisms of SOD-mimic activity on cobalt oxide surface with atomistic thermodynamic and kinetic details by a combination of rigorous density functional theory and microkinetic modeling. The catalytic activity of Co3O4 depends strongly on their size and structure. In this study, Co3O4 nanozyme with different size and structure exhibited different catalytic activities in the order of (Co3O4)2 > (Co3O4)3 > Co3O4. This order is closely related to their weak, tunable Co–O bonds. Our microkinetic modeling analysis shows that bi-hydrogen peroxide associative mechanisms (mechanism C) of CAT-mimic activity and ER mechanism of SOD-mimic activity for (Co3O4)2 are favorable, which is identified by the rate-determining steps (RDS), Energy span model (ESM), and microkinetic modeling analysis. For the CAT-mimic activities on (Co3O4)n surface, Campbell’s degree of rate control analysis indicates the key to catalyst improvement and design is to stabilize the key steps, which are related to the formation of H2O molecular. For the SOD-mimic activities of (Co3O4)n, we find the formation of H2O2 molecular to be the sole rate-controlling step. Degree of the thermodynamic rate control analysis reveals that the stronger H2O2*, OH* binding would facilitate the reaction of CAT-like activities of (Co3O4)n. And the adsorbed OHOO* with large negative degree of thermodynamic rate control would inhibit the reaction of CAT-like activities of (Co3O4)n. Our results have not only provided new insights into deciphering (Co3O4)n artificial enzymes, but will also facilitate the design and construction of other types of target-specific artificial enzymes.

    更新日期:2019-12-03
  • Preparation and Application of Ordered Mesoporous Metal Oxide Catalytic Materials
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-11-26
    Zihao Fu, Guodong Zhang, Zhicheng Tang, Haitao Zhang

    The ordered mesoporous metal oxides as catalytic carrier or active center have been reported by many literatures. The large specific surface area and ordered mesoporous structure had caused great concern in the field of catalysis. In the catalytic reaction, the ordered mesoporous materials had great mechanical properties and the active centers had strong interaction between each other. There were obviously advantages of these ordered mesoporous materials than bulk materials or routine nano-materials in the catalytic conversion of volatile organic compound, CO, NOx and other polluting gases. At present, researchers prepared a variety of ordered mesoporous metal oxides by different synthetic methods. Based on the analysis and summary of the literature, this paper briefly reviewed the preparation methods and application of ordered mesoporous metal oxide catalysts and the prospect of future development is worth expecting.

    更新日期:2019-11-27
  • Experimental Study on SO 2 -to-SO 3 Conversion Over Fe-Modified Mn/ZSM-5 Catalysts During the Catalytic Reduction of NO x
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-07-17
    Haiping Xiao, Chaozong Dou, Jian Li, Zonghai Yuan, Hongkun Lv

    Mn–Fe/ZSM-5 catalysts with different Fe loading amounts were prepared using wet impregnation and the effects of these catalysts on SO3 formation during the catalytic reduction of NOx were assessed. Variations in the catalysts’ physicochemical properties with different Fe contents were also investigated using BET, XRD, SEM–EDS, FT-IR, H2-TPR and XPS techniques. The 9Mn9Fe catalyst gave the highest SO2-to-SO3 and NOx conversions, and adding Fe also improved the catalyst’s SO2 resistance. The presence of NO2 caused the formation of nitrate ions on the catalyst surface during fast SCR. These nitrate ions re-oxidized the active sites more rapidly than O2 at low temperatures, thereby promoting the redox reaction. BET, XRD and SEM–EDS showed that optimal Fe loading amount reduced MnOx crystallinity while improving surface dispersion. Adding excessive Fe caused the active compositions to accumulate on the catalyst surface. FT-IR, H2-TPR and XPS demonstrated that optimal Fe loading amount increased the quantity of Mn4+=O bonds while raising the concentrations of Mn4+ ions and lattice oxygen, thus enhancing SO2-to-SO3-conversion. Therefore, although suitable amounts of Fe and NO2 promoted NOx conversion, these species also significantly increased SO2-to-SO3 conversion.

    更新日期:2019-11-04
  • MoS 2 /NiTiO 3 Heterojunctions as Photocatalysts: Improved Charge Separation for Promoting Photocatalytic Hydrogen Production Activity
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-07-17
    Yanru Li, Jing Xu, Meirong Peng, Zeying Liu, Xuanhao Li, Sheng Zhao

    In this study, a novel molybdenum disulfide modified nickel titanate composite photocatalyst MoS2/NiTiO3 was designed and synthesized by a simple hydrothermal method. The petal-like MoS2 is highly dispersive, which provides many active sites. The photocatalytic activity of MoS2/NiTiO3 for hydrogen evolution is better than that of pure MoS2 and NiTiO3 nanosheets. The hydrogen evolution amount of MoS2/NiTiO3 is 300.43 μmol, which is 5.3 and 1.9 times higher than of pure NiTiO3 and MoS2, respectively. In addition, the catalyst 7% MoS2/NiTiO3 has good stability through cyclic experiments. The results of photoluminescence spectroscopy and photoelectrochemical measurements show that the introduction of MoS2 accelerates the separation and transfer efficiency of photogenerated electrons. We have also proposed new discoveries for charge transfer mechanism of MoS2/NiTiO3 composite catalyst, which will provide a novel way to develop simple and inexpensive photocatalysts.

    更新日期:2019-11-04
  • Controlled Synthesis of Mesoporous CeO 2 -WO 3 /TiO 2 Microspheres Catalysts for the Selective Catalytic Reduction of NO x with NH 3
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-06-12
    Jie Guo, Guodong Zhang, Zhicheng Tang, Jiyi Zhang

    A series of mesoporous TiO2 supports were synthesized by changing the hydrothermal temperature. Subsequently, CeO2-WO3/TiO2 catalysts were prepared by impregnation method and applied for selective catalytic reduction (SCR) of NOx with NH3. In addition, the morphology of TiO2 changed from microspheres to ellipsoidal microspheres by gradually increasing the hydrothermal temperature which was 120 °C, 160 °C and 200 °C. Obviously, the SCR activity was exhibited in the following order: CeO2-WO3/TiO2-160 > CeO2-WO3/TiO2-120 > CeO2-WO3/TiO2-200. Among, the CeO2-WO3/TiO2-160 catalyst exhibited better catalytic activity for the NH3-SCR reaction. Through a series of characterizations, it was concluded that the mesoporous structure, redox ability and abundant surface acidity of the CeO2-WO3/TiO2 catalyst played a critical role in improving the activity, resistant of H2O and SO2.

    更新日期:2019-11-04
  • An Overview of Light Olefins Production via Steam Enhanced Catalytic Cracking
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-06-17
    Aaron Akah, Jesse Williams, Musaed Ghrami

    Steam thermal cracking is an established technology for the production of light olefins, such as ethylene and propylene. The shift to lighter, ethane-based feeds means that propylene production from steam crackers will be lower than the corresponding ethylene production. Therefore, alternative technologies have to be developed to produce more propylene to make up for the shortfall from steam cracking. This review looks at the steam catalytic cracking technology, which combines both catalytic cracking and steam cracking to maximize the production of light olefins. This review looks at the effect of catalyst and technology applied in fluid catalytic cracking reactors to enhance light olefins production. The influence of reaction conditions and the reaction mechanism are also presented.

    更新日期:2019-11-04
  • Effects of Cu/Al Mass Ratio and Hydrothermal Aging Temperature on Catalytic Performance of Cu/SAPO-18 for the NH 3 -SCR of NO in Simulated Diesel Exhaust
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-07-20
    Qi Gao, Qing Ye, Shuai Han, Shuiyuan Cheng, Tianfang Kang, Hongxing Dai

    The Cu/SAPO-18 samples with different Cu/Al mass ratios were prepared, their catalytic activities for the NH3-SCR of NO in simulated diesel exhaust were evaluated, and effects of Cu/Al mass ratio and hydrothermal aging temperature on catalytic performance of Cu/SAPO-18 was examined. Physicochemical properties of the samples were characterized by means of various techniques. It is found that the activity of the sample changed with a rise in Cu/Al mass ratio, with the highest overall activity being achieved over the sample with a Cu/Al mass ratio of 0.045. The H2-TPR results indicate that the Cu/Al mass ratio could affect the distribution of Cu species, and the Cu/SAPO-18-0.045 sample possessed the highest amount of the isolated Cu2+ species. BET and XRD results reveal that the Cu/Al mass ratio exerted little effect on the structure of the sample. Low-temperature hydrothermal treatment had the least influence on the sample, and the effect of high-temperature hydrothermal treatment on the sample became increasingly obvious with a rise in hydrothermal treatment temperature. It is concluded that the hydrothermal aging treatment mainly affected the sample by destroying the structure, blocking the pores, migration and transformation of the Cu species, and changing the acidic sites of the sample.

    更新日期:2019-11-04
  • Role of Cobalt Oxide-Based Catalysts for Styrene Production: A Review on Significance of Various Promoters, Calcination Temperature, Chemical Behavior of Support Materials and Synthesis Procedure
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-08-08
    Venkata Rao Madduluri, Kamaraju Seetha Rama Rao

    The direct CO2 oxidative dehydrogenation of ethyl benzene (ODH-EB) is a great potential for the production of valuable styrene monomer. In contrast, past/present styrene (ST) synthesis is mainly obtained from oxidative dehydrogenation of ethyl benzene (EB) and being transformed into pilot scale under CO2 atmosphere. It was due to few unresolved restrictions existed in the synthesis of styrene monomer using the steam assisted process and commercial ST production technology. These problems are being rectified by ODH-EB process using CO2 as a soft oxidant. Therefore, ODH of EB is well-known high temperature process to convert the EB (petroleum by product) into valuable ST monomer through the utilizing of CO2. Present study clearly explains the concise history of dehydrogenation process used to convert EB to ST monomer, which is essential feedstock in the wide range of industrial commodities production. In this discussion we majorly devoted to design, development and synthesis of different Co based catalysts by applying different support materials such as SiO2, MgO, MgAl2O4 and γ-Al2O3 respectively. Moreover, this study extensively deals with chemical behavior of oxidants, utilization of viable active promoters and its characteristics features in the oxidative dehydrogenation process. Different reaction mechanisms in the ODH of EB process to describe CO2 utilization as well as surface styrene monomer formation and evaluation of other by products were discussed widely in this review paper. The surface acidic and basic chemistry of various support materials, its preparation, utilization and its catalytic activity applications have been discussed. Acidic–basic textural properties of different solid oxide support materials have been extensively illustrated through incorporation of variety active metallic oxide and promoters. The catalyst activity evaluation in ODH of EB process as well as plausible reaction mechanism of styrene monomer formation has been explained.

    更新日期:2019-11-04
  • Surfactant-Free Synthesis of Single-Crystalline Bi 4 Ti 3 O 12 Nanosheets with Excellent Visible-Light Photocatalytic Activity
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-06-28
    Wan Jiang, Tongzhou Chen, Xin Yang, Luoyuan Ruan, Yong Liu, Xianqian Meng, Gang Xu, Gaorong Han

    Single-crystalline Bi4Ti3O12 nanosheets with a thickness less than 10 nm and a lateral size larger than 20 μm have successfully synthesized via a surfactant-free hydrothermal route by employing K2Ti6O13 nanofibers prepared in advance as titanium sources. The as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction, respectively. The results revealed that the single-crystalline Bi4Ti3O12 nanosheets are dominated with (010) facets. In general, the slow exfoliation of TiO6 octahedron lamella and the fast combination of the subnitrate radicals with the Bi3+ ions situated in (010) planes induce the crystallization of the single-crystalline Bi4Ti3O12 nanosheets. In addition, the as-prepared single-crystalline Bi4Ti3O12 nanosheets propose a narrowed gap of ca. 2.41 eV and after modified by Pt-quantum-dots exhibit excellent visible-light photocatalytic activity. It is believed that the surfactant-free in the hydrothermal system induce more amount of surface state responsible for the narrowed gap and the excellent visible-light photocatalytic activity.

    更新日期:2019-11-04
  • Anchored Silicotungstates: Effect of Supports on Catalytic Activity
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-06-25
    Anjali Patel, Nilesh Narkhede, Anish Patel

    In this review, we have summarized the work carried out on anchored silicotungstates, an upcoming important field of heterogeneous catalysis. Relation between the structural diversity, especially geometry of the supports, and acid catalysed reactions have been discussed by taking some case studies. It was found that the structure geometry of the supports plays an important role towards the activity as well as selectivity of the products.

    更新日期:2019-11-04
  • A Review on Pd Based Catalysts for CO 2 Hydrogenation to Methanol: In-Depth Activity and DRIFTS Mechanistic Study
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-10-19
    Opeyemi A. Ojelade, Sharif F. Zaman

    Global warming, the environmental curse, created mainly by anthropogenic uses of fossil resources causing an excessive amount of CO2 emission in the earth’s atmosphere. Scientists are focusing to utilize CO2 to produce value added chemicals, i.e. methanol, DME, formic acid, etc. to reduce the effect of this greenhouse gas (GHG) and also provide an alternative carbon source and carbon neutral pathway for valuable chemicals. Despite significant achievements so far on the conversion of CO2 to methanol via hydrogenation over Cu–ZnO–Al2O3 catalyst, palladium and palladium based bimetallic catalysts showed a superior activity (> 10% CO2 conversion) and selectivity (~ 100%) to methanol over Cu based catalysts especially at low pressure (≤ 30 bar) and low temperature (≤ 250 °C). The alloying effect of Pd with the support ZnO, ZrO2, Ga2O3, etc. forming PdZn, PdZr2, PdGa species, which are identified as the main active phase of methanol synthesis. Also, reducible oxidic supports like CeO2, ZrO2, Ga2O3, etc. played important roles in adsorbing and activating CO2 as CO and or CO3− over the surface and hydrogenated to formate species, which has been regarded as the pivotal intermediate for methanol synthesis. Though there are challenges involving the costs of noble metal palladium, hydrogen production from renewable sources and carbon capture and storage (CSS) processes. There are several review articles on CO2 hydrogenation to methanol in the past few years but none of the existing review articles uniquely dealt with Pd-based catalysts. On this premise, this article presents a brief review comprising catalytic activity of Pd and Pd based bimetallic catalysts, effects of supports and promoters, reaction mechanism (DRIFTS studies) and perspectives on future researches necessary to achieve industrial acceptability of Pd-based catalyst for CO2 hydrogenation to methanol.

    更新日期:2019-11-04
  • ZSM-5 Zeolite Based Additive in FCC Process: A Review on Modifications for Improving Propylene Production
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-09-25
    Mohammed F. Alotibi, Basheer A. Alshammari, Mohammad Hayal Alotaibi, Faisal M. Alotaibi, Saeed Alshihri, R. M. Navarro, J. L. G. Fierro

    Propylene is a very essential building block in the petrochemical industry. There is a fast growing in its demand that is steadily expanding its market. Fluid catalytic cracking units is the second largest propylene source for petrochemical application. FCC units are primarily used in the production of gasoline. However, refiners have taken advantage with the aim of producing and recovering large amounts of propylene from their Fluid catalytic cracking unit by raising the severity of reaction through riser temperature, installation of a propylene recovery unit and addition of a catalyst that is shape selectivity. ZSM-5 is nowadays used as a very efficient fluid catalytic cracking additive for increasing light olefins production i.e. propylene. This short review will be exclusively focused on ZSM-5-containing additives and look at the main strategies used in the design and modifications of ZSM-5 catalysts to increase the propylene production in the FCC units. The review will highlight the most important and the recent modification methods used in enhancing ZSM-5 performance in the FCC process to maximize the yield of light olefins in general, and in particular that of propylene. These methods include particle size and acidity modification, phosphorus treatment, mesoporous/hierarchical structure creation, incorporation alkali metals and some selected transition metals and introduction of rare-earth metal.

    更新日期:2019-11-04
  • Influence of MnO 2 Morphology on the Catalytic Performance of Ag/MnO 2 for the HCHO Oxidation
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-04-08
    Suhong Lu, Qinyu Zhu, Yaxin Dong, Yiming Zheng, Xue Wang, Kelun Li, Fenglin Huang, Bo Peng, Yuliang Chen

    A series of Ag/MnO2 catalysts employing MnO2 nanorods (MnO2-r) and nanoparticles (MnO2-n) as the supports were prepared by conventional incipient wetness impregnation. Their structures had been characterized by BET, SEM, TEM, XRD, H2-TPR, O2-TPD and XPS. The catalytic activities in HCHO oxidation had also been investigated. The results showed that MnO2-r and MnO2-n exhibited different reducibility and surface active oxygen. Ag/MnO2-r performed better reducibility and more surface active oxygen than that of Ag/MnO2-n. It had observed that Ag/MnO2-r could achieve complete oxidation of HCHO at 80 °C, due to the low-temperature reducibility and abundant surface active oxygen. Meanwhile, the Ag/MnO2-r catalyst exhibited good stability.

    更新日期:2019-11-04
  • Catalytic Removal of Benzene at Mild Temperature over Manganese Oxide Catalysts
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-02-19
    Hao Guo, Zhixiang Zhang, Hajime Hojo, Mingxia Chen, Hisahiro Einaga, Wenfeng Shangguan

    Series of MnOx catalysts were synthesized through oxalate route and calcined at facile temperatures. Characterizations through XRD, N2-adsorption/desorption, HRTEM, C6H6-TPD, O2-TPD, XPS, and H2-TPR revealed that MnOx calcined at 250 °C (N250) with a main crystal phase of Mn2O3 showed micro-mesopores and largest specific surface area, and therefore had a high adsorption capacity of C6H6. N250 also presented better oxygen mobility, rich surface adsorbed oxygen species (Oads), and proper ratio of surface Mn4+/Mn3+. The starting temperature of H2-TPR of N250 was the lowest among the obtained MnOx samples. As a result, N250 exhibited the lowest T90 value of 191 °C in C6H6 thermal catalytic oxidation (WHSV 60,000 mL gcat.−1 h−1, initial C6H6 concentration 190 ppm) among all the catalysts, and this T90 value is lower than those reported in many research. At last, a potential reaction pathway was proposed according to the results of in-situ FTIR measurement.

    更新日期:2019-11-04
  • CdS Photocorrosion Protection by MoSe 2 Modification for Photocatalytic Hydrogen Production
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-05-22
    Yang Liu, Xiaohua Ma, Haiyu Wang, Yanbing Li, Zhiliang Jin

    As a promising and low-cost semiconductor photocatalyst, CdS can be excited under visible-light-driven and it has attracted extensive attention. In order to effectively avoid CdS photocorrosion, MoSe2/CdS composite is fabricated by mean of a special method. The MoSe2/CdS composite exhibits high photo-catalytic activity and stability, when the loading of MoSe2 is 5%, the H2-evolution yield of MoSe2/CdS composite photocatalyst reach 112.4 μmol h−1 under visible light irradiation, which is 4.94 times of pure CdS. In addition, the more detailed studies show that the improvement of photocatalytic activity and stability is due to the following reasons: it can be clearly found from the results of the UV–Visible diffuse reflectance spectrum that MoSe2 in MoSe2/CdS composite greatly improves the light absorption performance,which effectively increases the light absorption intensity of the MoSe2/CdS composite photocatalyst in the photocatalytic reaction system and promotes the electronic transition of the MoSe2/CdS composite photocatalyst. In addition, due to the excellent electron-transfer ability of MoSe2, the rapid transfer of photo-generated charges is further promoted, and the recombination of electron–hole pairs is effectively reduced, thereby MoSe2/CdS catalysts can provide more active sites for hydrogen evolution reaction. Moreover, the MoSe2/CdS composite photocatalyst shows higher photocurrent response, lower overpotential, faster electron transfer rate constant (KET) (3.33 × 108 s−1) and shorter fluorescence lifetime (2.52 ns) than pure CdS and pure MoSe2 because of the effective interface-electron transfer. The MoSe2/CdS composite photocatalyst effectively hinder the photoetching of CdS and achieves high photo-catalytic stability. And the possible mechanism of H2-evolution for MoSe2/CdS is proposed.

    更新日期:2019-11-04
  • Efficient Synthesis of Ethyl Levulinate Fuel Additives from Levulinic Acid Catalyzed by Sulfonated Pine Needle-Derived Carbon
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-03-27
    Ning Li, Xiao-Li Zhang, Xiu-Cheng Zheng, Gui-Hong Wang, Xiao-Ying Wang, Guang-Ping Zheng

    The low-cost and environmentally friendly solid acid catalysts for the efficient synthesis of ethyl levulinate fuel additives were prepared from pine needles through the partial carbonization, followed by a hydrothermal H2SO4 sulfonation procedure. The resultant sulfonated carbon catalysts possessed an amorphous carbon structure and high contents of the sulfate groups. Other than that, they had good thermal stability and the total acid density was as high as 2.28 mmol g−1. In this work, noticeably, the parameters of both synthetic and catalytic reactions were optimized to enhance the conversion of levulinic acid (LA). The results showed that the LA conversion was as high as 96.1% over the catalysts carbonizated at 700 °C for 90 min and sulfonated at 160 °C for 15 h under the optimized conditions (5:1 ethanol/LA molar ratio, 5 wt% catalyst dosage, 80 °C reaction temperature, 8 h reaction time). Meanwhile, the recyclability experiments confirmed that the resultant catalysts exhibited satisfactory reusability and the corresponding conversion of LA was maintained as 63.0% in the fourth run. Remarkably, the reused catalysts can be easily activated again and the corresponding LA conversion could reach up to 90.1%. The results demonstrated that the catalysts had great potential in the synthesis of biofuels, which could be efficient and could have excellent recyclability.

    更新日期:2019-11-04
  • Tailoring the Size and Shape of Colloidal Noble Metal Nanocrystals as a Valuable Tool in Catalysis
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-04-03
    Miriam Navlani-García, David Salinas-Torres, Kohsuke Mori, Yasutaka Kuwahara, Hiromi Yamashita

    The pivotal role of size and morphology-controlled nanocrystals in catalysis is a recognized fact nowadays. Among the strategies developed to adjust such features, colloidal synthetic approaches have been proven to be a valuable alternative through which noble metal nanocrystals with tailored sizes and morphologies can be formed upon proper selection of the experimental conditions. This review summarizes some of the main aspects to be considered in the synthesis of colloidal noble metal and includes representative examples of their catalytic applications by spotlighting the experimental conditions used in the synthesis and how the size and/or shape of the nanocrystals influence in the final catalytic performance.

    更新日期:2019-11-04
  • The Titanium–Aluminum Binary Oxide Immobilized over Long-Axis SBA-15 as Efficient and Benign Catalyst for Conversion of Sucrose into 5-Hydroxymethylfurfural
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-02-19
    Benhua Huang, Yu Cheng, Jinyi Ma, Zhen Chen, Kun Yu, Yang Sun

    The 5-hydroxymethylfurfural (HMF) is a versatile platform molecule that could be transformed into many fine chemicals. This compound is usually obtained by dehydration of fructose or glucose, but use of sucrose as substrate often demands high temperature and shows poor yield, deserving optimization. In this work, a series of titanium–aluminum binary oxides are prepared over long-axis SBA-15 through co-precipitation of metal salts, and metal ratio of solid product could be controlled by changing metal content of preparative solution. Catalysis reveals solvent, temperature, UV irradiation, and surface composition of catalyst show important influences on output, while catalyst having equimolar titanium and aluminum shows the most promising activity. Additionally, a catalytic mechanism is proposed based on catalyst characterization, catalytic results and calculations. This work would contribute to the synthesis of new oxide catalyst, as well as to utilization of biomass.

    更新日期:2019-11-04
  • Effective Electron–Hole Separation Over Controllable Construction of CdS/Co-Ni-P Core/Shell Nanophotocatalyst for Improved Photocatalytic Hydrogen Evolution Under Visible-Light-Driven
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-04-23
    Lijun Zhang, Zhiliang Jin

    In artificial photocatalysis, the slow kinetics of electron–hole transfer and high charge recombination rate have been the Achilles heel of photocatalytic conversion efficiency. Therefore, methods for promoting exciton splitting and charge separation have received sustained attention. Here, Co-Ni-P is used as a molecular cocatalyst, which is designed onto the surface of cadmium sulfide nanorods. CdS-Co-Ni-P constitutes a unique CdS/Co-Ni-P core/shell structure, which is a new type of efficient heterostructure photocatalysts used for photocatalytic decomposition of water to produce hydrogen. The modification strategy maximizes the contact area between the cocatalyst and the reactant, which effectively increases the light absorption capacity of the composite catalyst, reduces the overpotential of generating hydrogen, and accelerates the interface transfer rate of electron–hole pairs, thus achieving better photocatalytic decomposition of water. The reaction kinetics of the reduction is enhanced. Compared with pure CdS of the same quality, the optimal photocatalyst CdS-Co-Ni-P has a hydrogen evolution rate of 9.67 mmol g−1 h−1, which is about 5.3 times that of pure CdS. This work demonstrates that the new and efficient CdS/Co-Ni-P core/shell photocatalyst has great potential for photocatalytic production of H2.

    更新日期:2019-11-04
  • Advances in Catalyst Design for the Conversion of Methane to Aromatics: A Critical Review
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-03-04
    Ahmad Galadima, Oki Muraza

    The catalytic methane aromatization (CMA) via the non-oxidative approach is increasingly becoming an interesting process for natural gas, shale gas and biogas valorization. However, the design of catalytic materials that could produce very high methane conversion and aromatics selectivity at affordable stability is still difficult. We have carefully documented herein a comprehensive literature survey on the advances in different catalysts designed, characterized and evaluated for the CMA reaction in the recent times. Details on metal-modified zeolite systems including the active sites identification, role of different metals and their loadings, reaction mechanisms and influence of synthetic and catalytic parameters were substantially discussed. The scope was extended to include zeotypes, oxides, un-modified Mo-based compounds and associated catalysts recently evaluated. There are indications that the powdered GaN material is currently been considered as a CMA catalyst. Therefore, relevant studies were carefully surveyed and discussed. In all cases, parameters varied for ensuring conversion and selectivity control were simultaneously highlighted. The paper identified new research paths based on the areas partly explored for further investigations.

    更新日期:2019-11-04
  • Role of Mn: Promotion of Fast-SCR for Cu-SAPO-34 in Low-Temperature Selective Catalytic Reduction with Ammonia
    Catal. Surv. Asia (IF 2.25) Pub Date : 2019-05-27
    Minhua Zhang, Haibo Cao, Yifei Chen, Haoxi Jiang

    There is a required need for improving low-temperature selective catalytic reduction with ammonia (NH3-SCR) activities of catalysts. In this paper, Cu-SAPO-34 and Mn/Cu-SAPO-34 catalysts were prepared by a one-pot hydrothermal synthesis method. ICP-OES, N2 adsorption/desorption, XRD, FT-IR, SEM, H2-TPR, XPS, NH3/NO-TPD were performed to study the properties of the catalysts. Mn promoted Cu-SAPO-34 shows considerably improvement in low-temperature NH3-SCR activity with almost 100% NOx conversion between 220–300 °C. It is suggested that the excellent catalytic activity of Mn/Cu-SAPO-34 is ascribed to MnO2 which can promote “fast-SCR”. H2O/SO2 resistance tests were also investigated and the results show that the catalysts both exhibit strong resistance to H2O but the introduction of Mn doesn’t improve the SO2 resistance of Cu-SAPO-34.

    更新日期:2019-11-04
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