29 results
Search Results
2. Cyclic dipeptides: catalyst/promoter-free, rapid and environmentally benign cyclization of free amino acidsElectronic supplementary information (ESI) available: Supplementary information including experimental procedures along with MW graphs for all the compounds studied, 1H, 13C NMR, ESI-MS data, elemental analysis, melting points, optical rotation, single crystal X-ray data collection procedure, tables containing crystallographic details of (1, 9, 11–13, bond length, bond angles, dihedral angles and hydrogen bonding interactions), CCDCs 783550–783553contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre viawww.ccdc.cam.ac.uk/data_request/cif. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1gc15043j
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Nonappa, Ahonen, Kari, Lahtinen, Manu, and Kolehmainen, Erkki
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CYCLIC peptides , *SUSTAINABLE chemistry , *CATALYSTS , *RING formation (Chemistry) , *AMINO acids , *GREENHOUSE gases , *MOLECULAR self-assembly - Abstract
“The best catalyst is no catalyst.” With growing public concern over global warming and the amount of greenhouse gases, it is important to reduce the amount of chemicals and eliminate waste, to obtain better results in a simple, selective, safe, and environmentally benign fashion compared to conventional tedious chemical synthesis. Herein, we disclose an environmentally benign, rapid, catalyst/promoter/coupling reagent-free cyclization procedure of free amino acids to furnish exclusively cyclic dipeptides (2,5-diketopiperazines, DKPs) in excellent or even quantitative yield, along with their solid state self-assembling properties. This process is extremely simple and highly efficient with little or no traditional synthetic skills and without any chromatographic purification. Synthesis of structurally diverse DKPs has been achieved with a dramatic decrease in the reaction time, the amount/number of solvents used, a significant increase in the yield and nearly complete elimination of waste. As a result, this is an excellent example for the environmentally benign, clean and green chemistry concept. The most exciting outcome of our investigation is an unusual case of chiral self-recognition encountered upon the cyclization of rac-pipecolic acid, which resulted in the formation of the meso-product exclusively. [ABSTRACT FROM AUTHOR]
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- 2011
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3. Temperature-responsive Zn-based catalysts for efficient catalytic conversion of biomass-derived carbohydrates to ethyl lactate.
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Wang, Jiangang, Wang, Jinghua, Liu, Yifan, Liu, Tihang, Pang, Zhaobin, Cui, Hongyou, Zhang, Yuan, and Song, Feng
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CARBOHYDRATES , *CATALYST poisoning , *CATALYSTS , *LACTATES , *LACTIC acid , *POLYLACTIC acid , *SUCROSE - Abstract
Chemical catalytic conversion of biomass-derived sugars to lactic acid has attracted considerable attention due to the cheap, abundant and renewable nature of biomass and its huge potential application in the synthesis of biocompatible and biodegradable polylactic acid resins. However, this route is still a huge challenge in view of the transformation efficiency. This paper reports a series of Zn-based catalysts, which are facile and cheap to prepare and highly efficient for the conversion of biomass-derived carbohydrates to ethyl lactate (EL). The microstructure, active site composition and surface properties were characterized by TEM, HRTEM, XRD, NH3-TPD, CO2-TPD, Py-IR, and XPS. The catalytic performance of catalysts in the conversion of biomass-derived carbohydrates to ethyl lactate (EL) and the effect of water content were investigated. It was found that the Zn species played a decisive role in regulating the strengths of the acidic and basic sites to match the rate of each reaction in the tandem reactions. The basic sites are beneficial for isomerization and retro-aldol condensation, while the temperature-responsive released H+ protons are responsible for the dehydration of triose to methylglyoxal, a rate-determining step in the conversion of triose to EL. Addition of a small amount of water could enhance the release of the protons and thus accelerate the dehydration reaction, but excessive water would favor the formation of humins. Using ZnSi-2 as a catalyst under optimal conditions, yields as high as 74.5% of EL from glucose, 81.0% from fructose, 70.9% from mannose, and 80.3% from sucrose could be achieved with tens of times higher productivity than the previously reported values in the literature. DFT calculations revealed that Zn(OEt)Cl, Zn(OH)Cl, and Zn(OH)(OEt) were probably the active components. In addition, the stability of the catalyst as well as the deactivation and regeneration was also studied. The findings in this research provide new insights into the exploration of efficient catalysts for biomass conversion to value-added chemicals. [ABSTRACT FROM AUTHOR]
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- 2023
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4. Progress in batch preparation of single-atom catalysts and application in sustainable synthesis of fine chemicals.
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Hu, Yifan, Li, Hongxuan, Li, Zesheng, Li, Bolin, Wang, Shaoyu, Yao, Yuancheng, and Yu, Changlin
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CHEMICAL synthesis , *GAS migration , *CATALYSTS , *CATALYTIC activity , *COORDINATION polymers , *BALL mills , *RESEARCH teams - Abstract
In 2011, Zhang's research team, in cooperation with Li and Liu, reported the Pt1/FeOx atomically dispersed catalysts for the first time in the world, and based on this, proposed the concept of "single-atom catalysts". Single-atom catalysts (SACs) have a wide range of industrial application prospects in the catalytic synthesis of fine chemicals due to their high atomic utilization rate and special catalytic activity. With the deepening of the research, the preparation methods of SACs emerge in an endless stream, but it is still an urgent problem to realize the industrial production of highly stable SACs prepared in small batches (gram level) or even in large batches (kilogram level). In this review paper, several typical solvent-free green synthetic strategies (e.g., ball milling, physical mixing, gas migration, and pyrolyzing coordination polymers (including MOFs)) for the batch preparation of SACs are introduced. And typical catalytic application of SACs in green synthesis of fine chemicals by means of oxidation reaction, hydrogenation reaction, coupling reaction and other reactions are also introduced. This is the first review paper focusing on the mass preparation techniques of SACs and their applications in fine chemicals production. [ABSTRACT FROM AUTHOR]
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- 2021
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5. A simple continuous reaction for the synthesis of quinoline compounds.
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Song, Suhong, Dai, Yuyu, Hong, Yunyang, Li, Xiaoqing, and Yan, Xinhuan
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HYDROGEN transfer reactions , *QUINOLINE , *CATALYSTS , *SUSTAINABLE chemistry , *NITROAROMATIC compounds , *RUTHENIUM catalysts - Abstract
In this paper, 2-methylquinoline compounds were synthesized continuously from nitroarenes and the ethanol/water system by a simple hydrogen transfer reaction in the presence of the Ru–Fe/γ-Al2O3 catalyst. This new simple synthesis reaction was heterogeneous and continuous. At the same time, green solvents were used, and strong acids, oxidants, and other environmentally harmful substances were not added, which conformed to the principles of green chemistry. Through the impregnation method, the nanocatalysts with a smaller particle size and uniform dispersion were obtained on the γ-Al2O3 particles (1–2 mm) and had good activity. The effects of the alcohol water volume ratio, pressure, flow rate and Ru–Fe mass ratios on the yields of 2-methylquinoline compounds in the reaction were investigated. The reaction can proceed smoothly for nitroarenes with different substituents, and a moderate to good yield (46%–88%) was obtained. [ABSTRACT FROM AUTHOR]
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- 2022
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6. Dual -functional carbon-based solid acid-induced hydrothermal conversion of biomass saccharides: catalyst rational design and kinetic analysis.
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Xiong, Shanshan, Luo, Chao, Yu, Zhihao, Ji, Na, Zhu, Lingjun, and Wang, Shurong
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FURFURAL , *ACID catalysts , *CATALYSTS , *SACCHARIDES , *BIOMASS conversion , *ACTIVATION energy , *ENERGY conversion , *THERMAL stability - Abstract
The isomerization–dehydration cascade conversion on the saccharide platform is a pivotal route for biomass valorization, although it exhibits a specific reaction complexity that makes achieving an efficient conversion a highly technical challenge. The rational design of novel versatile solid acids is deemed to be the key to improving the cascade catalytic performance. In this paper, a dual-functional carbon-based solid acid catalyst (DFCSA) with tunable Brønsted/Lewis acid sites was developed for the cascade conversion of saccharides. The combined modification of H3PO4 and HNO3 on the carbon substrate contributed to the grafting of protonated moieties with a reasonably porous structure. With the aid of AlPO4, which has an orthorhombic crystal structure, the newly developed catalyst was able to achieve good performance for the subsequent hydrothermal conversion. Under optimal conditions, glucose and xylose were transformed with high product yields: 38.2 mol% levulinic acid and 69.7 mol% furfural, respectively. In addition, the catalyst displayed excellent hydrothermal stability, with only a slight degradation in activity after 10 cycles, which was ascribed mainly to the high thermal stability of AlPO4 and the firm grafting of the surface functional groups. As shown by the kinetic analysis, the DFSCA catalyst had a higher conversion rate and lower activation energy in the cascade conversion of xylose than that of glucose, leading to a better yield of furfural. [ABSTRACT FROM AUTHOR]
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- 2021
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7. Selective production of bio-based para-xylene over an FeOx-modified Pd/Al2O3 catalyst.
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Xiao, Yuxue, Meng, Qingwei, Pan, Xiaoli, Zhang, Chao, Fu, Zaihui, and Li, Changzhi
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CATALYSTS , *METAL catalysts , *ELECTRON density , *PRECIOUS metals , *DECARBONYLATION , *POLYETHYLENE terephthalate - Abstract
para-Xylene (PX) is a basic building block of polyethylene terephthalate, which is currently produced from petroleum resources. Developing a renewable route to PX is highly desirable to address both economic and environmental concerns. Several attempts used noble metal catalysts, e.g. Pd/Al2O3, to synthesize PX from biomass-derived 4-methyl-3-cyclohexene-1-carboxaldehyde (4-MCHCA), but suffered from a severe decarbonylation reaction, resulting in toluene as the main product. In this paper, we report an FeOx modification strategy to suppress the decarbonylation reaction on a Pd/Al2O3 catalyst, leading to a drastic shift in selectivity towards PX with a yield up to 81% via a cascade dehydroaromatization–hydrodeoxygenation (DHA–HDO) pathway. Characterization and control experiments revealed that the electron density of Pd sites decreased in an FeOx-modified Pd/Al2O3 catalyst compared to Pd/Al2O3, thus tuning the preferential adsorption mode of the substrate from η2-(C,O), the key transition state of the decarbonylation reaction, to the η1-(O) mode that favors the hydrodeoxygenation process. Notably, this designed catalyst is highly stable and is readily applicable in the selective synthesis of a broad range of desired aromatic chemicals via the same DHA–HDO pathway from cyclohex-3-enecarbaldehyde derivatives. Overall, this work develops a controllable catalyst modification strategy that tailors an efficient catalyst for petroleum-independent bio-PX synthesis. [ABSTRACT FROM AUTHOR]
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- 2020
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8. Iron-catalysed 1,2-acyl migration of tertiary α-azido ketones and 2-azido-1,3-dicarbonyl compounds.
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Yang, Tonghao, Lin, Yajun, Yang, Chaoqun, and Yu, Wei
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KETONES , *BENZENE , *IRON compounds , *CATALYSTS - Abstract
Iron-catalysed 1,2-acyl migration of tertiary α-azido ketones and 2-azido-1,3-dicarbonyl compounds provides a simple and atom-economical approach toward enamides and isoquinolones. This paper reports two catalyst systems for these transformations which employ iron(II) complexes [Fe(dpbz)]Br2 (dpbz = 1,2-bis(diphenylphosphino)benzene) and FeBr2/Et3N, respectively. [Fe(dpbz)]Br2 was found to be highly effective at converting 2-azido-2,3-dihydro-1H-inden-1-ones to isoquinolones. The reagent combination of FeBr2/Et3N, on the other hand, exhibited a broader catalytic scope, owing to the beneficial effect of Et3N. This latter catalyst system enables 2-azido-2-methyl-1,3-dicarbonyl compounds to be converted to the corresponding enamides under mild conditions in good yields. [ABSTRACT FROM AUTHOR]
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- 2019
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9. Green chemistry perspectives of methane conversion via oxidative methylation of aromatics over zeolite catalysts.
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METHANE , *GREENHOUSE gases , *ZEOLITES , *CATALYSTS - Abstract
Methane gas is known to be the most destructive greenhouse gas. The current world reserves of natural gas, which contains mainly methane, are also still underutilized due to high transportation costs. Thus, considerable interest is presently shown in conversion of methane to transportable liquid fuels and chemicals of importance to the petrochemical industry. The catalytic methylation of aromatics is one possible new route for converting methane to more valuable higher hydrocarbons. This paper provides a general overview of the recent work that we and other researchers have done on the utilisation of methane for catalytic methylation of aromatic compounds and for direct coal liquefaction for the production of liquid hydrocarbons. In particular, the paper presents a detailed description of more recent substantial experimental evidence that we have provided for the requirement of oxygen as a stoichiometry reactant for benzene methylation with methane over moderately acidic zeolite catalysts. The reaction, which has been termed “oxidative methylation”, was thus postulated to involve a two-step mechanism involving intermediate methanol formation by methane partial oxidation, followed by benzene methylation with methanol in the second step. However, strongly acidic zeolites can cause cracking of benzene to yield methylated products in the absence of oxygen. The participation of methane and oxygen, and the effective use of zeolite catalysts in this methylation reaction definitely have some positive green chemistry implications. Thus, the results of these previous studies are also discussed in this review in light of the principles and tools of green chemistry. Various metrics were used to evaluate the greenness, cost-effectiveness, and material and energy efficiency of the oxidative methylation reaction. [ABSTRACT FROM AUTHOR]
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- 2007
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10. Recent advances in catalysis in micellar media.
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La Sorella, Giorgio, Strukul, Giorgio, and Scarso, Alessandro
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MICELLAR catalysis , *MICELLES , *SURFACE active agents , *CHEMICAL reagents , *CATALYSTS , *NUCLEAR magnetic resonance - Abstract
The present review paper deals with the development of catalytic systems in water in the presence of micelles obtained by addition of surfactants, focusing on the effects of these simple, economic, and green reaction media on important aspects like recyclability, activity, product and substrate selectivity. Contributions from 2005 to 2014 are surveyed with particular emphasis on emerging findings and directions in the field of catalysis. Surfactants enable formation of nanosized apolar aggregates in bulk water where the catalysts and reagents can be dissolved thanks to weak intermolecular interactions like the hydrophobic effect and ion pairing operating in a more concentrated system compared to the bulk solvent. While in the past the use of surfactants was a straightforward approach to enable solubilization of reaction mixtures in water, nowadays specific interactions between substrates, catalysts and micelles are investigated by means of NMR and other techniques to better understand the molecular basis of this kind of supramolecular catalysis. Specifically designed surfactants to engineer micelles in order to compete efficiently with traditional catalysis in organic solvents are nowadays available. [ABSTRACT FROM AUTHOR]
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- 2015
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11. Nanoporous catalysts for biomass conversion.
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Liang Wang and Feng-Shou Xiao
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CATALYSTS , *CHEMICAL inhibitors , *CATALYMETRIC titration , *RADIOENZYMATIC assays , *POLYMER aggregates - Abstract
Biomass conversion is potentially important for producing renewable fuels and chemicals in the future, and the nanoporous materials as acidic, basic, or metallic catalysts play important roles in the biomass conversion. This paper briefly summarizes recent developments on the nanoporous material-based catalysts used for biomass conversion, including mesoporous/macroporous resins, mesoporous metal oxides, microporous/mesoporous carbons, mesoporous silicas, hierarchically mesoporous polydivinylbenzene, and microporous zeolites. Due to their superior thermal and hydrothermal stability, controllable acidity, and relatively easy introduction of mesoporosity into the crystals, compared with other nanoporous catalysts, zeolites have good opportunities for application in biomass conversion. [ABSTRACT FROM AUTHOR]
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- 2015
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12. Magnetically recoverable nanoparticles as efficient catalysts for organic transformations in aqueous medium.
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Tanyu Cheng, Dacheng Zhang, Hexing Li, and Guohua Liu
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NANOPARTICLES , *CATALYSTS , *NANOSTRUCTURED materials , *CHEMICAL inhibitors , *ENVIRONMENTAL chemistry - Abstract
Development of magnetic nanoparticles (MNPs) for use as supports and exploration of their applications in aqueous catalysis represent an important branch of green chemistry as they enable environmentally friendly and sustainable catalytic processes. Besides the significant merit of easily recovering magnetic nanoparticles from reaction systems, various strategies through surface modification, grafting and selfassembly offer a broad range of approaches for constructing magnetically recoverable heterogeneous catalysts. In this review, we focus on the green catalytic processes and summarize recent advances in organic transformations catalyzed by magnetically recoverable catalysts (MRCs). This paper is divided into two main parts: the first part provides background information on the general preparation, modifications, and characterization, where the modifications of various magnetic nanoparticles through coating with silica, carbon, metal, or polymer are also presented. The second part provides a basic outline of aqueous catalysis based on water-only or water-and-organic solvent cosolvent systems, in which numerous types of organic transformations are catalyzed by magnetically recoverable catalysts. Lastly, perspectives for further development of magnetically recoverable heterogeneous catalysts in aqueous catalysis are addressed. [ABSTRACT FROM AUTHOR]
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- 2014
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13. Entrainer-intensified vacuum reactive distillation process for the separation of 5-hydroxylmethylfurfural from the dehydration of carbohydrates catalyzed by a metal salt–ionic liquid.
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Wei, Zuojun, Liu, Yingxin, Thushara, Dilantha, and Ren, Qilong
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DISTILLATION , *DEHYDRATION reactions , *CARBOHYDRATES , *IONIC liquids , *CATALYSTS , *GLUCOSE , *FRUCTOSE - Abstract
As more and more novel catalyst systems are being developed for the dehydration of carbohydrates, especially glucose, an effective way to separate the dehydration product 5-hydroxylmethylfurfural (5-HMF) is also required for industrial manufacturing. In this paper, for the first time, we have developed a process called EIVRD (entrainer-intensified vacuum reactive distillation) to separate 5-HMF from the dehydration solutions of carbohydrates catalyzed by a metal chloride/1-methyl-3-octyl imidazolium chloride ([OMIM]Cl) ionic liquid, in which high vacuity and entrainers were applied to intensify the distillation of 5-HMF as well as the dehydration of fructose or glucose. In such an EIVRD process, the average recoveries of 5-HMF dehydrated from fructose and glucose are around 93% and 88%, respectively. The recycling of the catalyst system in the EIVRD process is so convenient that the recovery and actual yield of 5-HMF is successfully repeated during the whole five recycled reactions. [ABSTRACT FROM AUTHOR]
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- 2012
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14. Soaking of pine wood chips with ionic liquids for reduced energy input during grinding.
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Brandt, Agnieszka, Erickson, James K., Hallett, Jason P., Murphy, Richard J., Potthast, Antje, Ray, Michael J., Rosenau, Thomas, Schrems, Michael, and Welton, Tom
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IONIC liquids , *GRINDING & polishing , *SOLVENTS , *CATALYSTS , *LIGNOCELLULOSE , *HYDROLYSIS - Abstract
Ionic liquids are of great interest as potential solvents/catalysts for the production of fuels and chemicals from lignocellulosic biomass. Attention has focused particularly on the pretreatment of lignocellulose to make the cellulose more accessible to enzymatic hydrolysis. Any biomass processing requires a reduction in the size of the harvested biomass by chipping and/or grinding to make it more amenable to chemical and biological treatments. This paper demonstrates that significant energy savings can be achieved in the grinding of pine wood chips when the ionic liquid is added before the grinding operation. We show that this is due to the lubricating properties of the ionic liquids and not to physico-chemical modifications of the biomass. A brief impregnation of the chipped biomass results in higher savings than a longer treatment. [ABSTRACT FROM AUTHOR]
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- 2012
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15. An atom-efficient synthetic method: carbosilylations of alkenes, alkynes, and cyclic acetals using Lewis and Brønsted acid catalysts.
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Motokura, Ken and Baba, Toshihide
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CHEMICAL reactions , *LEWIS acids , *ALKENES , *ALKYNES , *BUTYNE , *ACETAL resins , *CATALYSTS - Abstract
Carbosilylation is a straightforward procedure to install both silyl and organic functional groups onto organic molecules. For example, allylsilylation of alkenes with allylsilanes affords 5-silyl-1-pentene derivatives. In this review paper, catalytic allylsilylations and arylsilylations of alkenes, alkynes, and cyclic acetals are summarized. Specific catalyses of Lewis and Brønsted acids, such as HfCl4 and proton-exchanged montmorillonite, will be discussed. Intramolecular reactions as well as intermolecular allyl- and arylsilylations have been achieved. In the case of the Brønsted acid catalyst, cationic Si species generated and acted as catalytically active species. The structure of the cationic Si species depends on the type of Brønsted acid used. A disilyl cation was proposed as the catalytically active site for carbosilylations of alkenes and alkynes, while a monomeric Si species was active for allylsilylation of cyclic acetals. [ABSTRACT FROM AUTHOR]
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- 2012
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16. Tungsten-Vanadium mixed oxides for the oxidehydration of glycerol into acrylic acid.
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Soriano, M. Dolores, Concepción, P., Nieto, J. M. López, Cavani, F., Guidetti, S., and Trevisanut, C.
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GLYCERIN , *ACRYLIC acid , *TUNGSTEN bronze , *VANADIUM oxide , *ACROLEIN oxidation , *CATALYSTS - Abstract
In this paper we report on the one-pot transformation of glycerol into acrylic acid, catalyzed by W/V mixed oxides, with hexagonal tungsten bronze (HTB) structure. The reaction requires two different catalyst functions, i.e., an acid one, which is given by W oxide, and an oxidizing one, given by the V ions incorporated within the WO3 lattice. W–O bronze is very active and moderately selective in acrolein formation, but yields only traces of acrylic acid. The incorporation of increasing amounts of V inside the hexagonal tungsten bronze structure, with the development of a monophasic compound, allows the consecutive oxidation of acrolein into acrylic acid. An optimal atomic ratio between W and V equal to V/(W + V) = 0.12–0.21 made it possible to obtain an acrylic acid yield of 25% (with selectivity to residual acrolein of 11%). However, during reaction under the oxygen-containing feed, the V4+ incorporated into the hexagonal bronze structure underwent a slow oxidation into V5+, which caused a progressive decline of selectivity to acrylic acid and a concomitant increase of COx formation; the hexagonal structure however was stable during lifetime experiments. On the other hand, in the absence of oxygen a very rapid deactivation of the catalyst occurred, with a decrease in selectivity to acrolein and increase in heavy by-products. [ABSTRACT FROM AUTHOR]
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- 2011
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17. Simple and recyclable ionic liquid based system for the selective decomposition of formic acid to hydrogen and carbon dioxide.
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Berger, M. E. M., Assenbaum, D., Taccardi, N., Spiecker, E., and Wasserscheid, P.
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IONIC liquids , *CHEMICAL decomposition , *FORMIC acid , *HYDROGEN , *CARBON dioxide , *SOLVENTS , *CATALYSTS - Abstract
Exploitation of hydrogen as an energy carrier requires the development of systems for its storage and delivery. Formic acid has been proposed as valuable hydrogen carrier compound, due to its relatively high hydrogen content (53 g L−1), the latter being easily and cleanly released in catalytic reactions under mild conditions (HCOOH → H2 + CO2). Ionic liquids are interesting solvents for homogeneous catalyzed formic acid decomposition systems as their extremely low volatility avoids solvent contamination of the produced hydrogen stream. In this paper an outstandingly simple, robust and active catalyst system is presented, namely RuCl3 dissolved in 1-ethyl-2,3-dimethylimidazolium acetate (RuCl3/[EMMIM][OAc]). This system proved to be fully recyclable over 10 times. Turnover frequencies (TOF) of 150 h−1 and 850 h−1 were obtained at 80 °C and 120 °C, respectively. [ABSTRACT FROM AUTHOR]
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- 2011
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18. Decarboxylation of dialkyl carbonates to dialkyl ethers over alkali metal-exchanged faujasitesElectronic supplementary information (ESI) available: (i) A synopsis of MS signals for major gaseous and liquid products, including DME, CO2, propylene, diethyl ether, diproyl ether, isomeric octenes, and glycidol; (ii) an IR spectrum for a reaction mixture from the decarboxylation of DMC, including dimethyl ether, CO2, and DMC. See DOI: 10.1039/c0gc00536c
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Maurizio Selva, Massimo Fabris, and Alvise Perosa
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DECARBOXYLATION , *CARBONATES , *ETHERS , *ZEOLITES , *CATALYSTS , *TEMPERATURE effect , *CHEMICAL reactions - Abstract
Non-toxic DAlCs, especially lighter dimethyl- and diethyl-carbonate, are regarded as very green alkylating reagents, particularly when coupled with metal-exchanged Y- and X-faujasites as catalysts. These reactions are selective, free from wastes or byproducts, and often require no additional solvent other than the carbonate. Nonetheless, this paper demonstrates that the operating temperature and the nature of the faujasite must be carefully chosen in order to avoid DAlC decomposition. In fact, at temperatures ranging from 150 to 240 °C, faujasites can promote decarboxylation of light DAlCs to the corresponding ethers CH3OCH3and CH3CH2OCH2CH3plus CO2. Heavier DAlCs (dipropyl- and dioctyl-carbonate) undergo a similar decomposition pathway, followed by further reactions to the corresponding alcohols (n-propanol and n-octanol) and alkenes [propylene and octene(s)]. These transformations not only consume DAlCs, but also give rise to dangerously flammable ethers, as well as undesirable alcohols, alkenes and CO2. The present work reports an original investigation of the decarboxylation of DAlCs on faujasites with the aim of providing operative boundaries to the experimental conditions to minimise unwanted decomposition. The reaction is strongly affected by the nature of the catalyst: the more basic zeolites, NaX and CsY, are by far more active systems than NaY and LiY. However, solid K2CO3proves to be rather inefficient. The temperature also plays a crucial role: for example, the onset of the decarboxylation of DMC requires a temperature of ∼30 °C lower than that for DEC and DPrC. Overall, awareness that certain zeolites cause decomposition of DAlCs under conditions similar to the ones used for DAlC-promoted alkylations allows determination of the correct experimental boundaries for a safer and more productive use of DAlCs as alkylating agents. [ABSTRACT FROM AUTHOR]
- Published
- 2011
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19. Chloride ions enhance furfural formation from d-xylose in dilute aqueous acidic solutions.
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Marcotullio, Gianluca and De Jong, Wiebren
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FURFURAL , *CHLORIDES , *ENERGY consumption , *CHEMICAL reactions , *CATALYSTS , *CHEMICAL kinetics , *SOLUTION (Chemistry) - Abstract
Furfural production through traditional processes is accompanied by acidic waste stream production and high energy consumption. Modern furfural production process concepts will have to consider environmental concerns and energy requirements besides economics, moreover will have to be integrated within widened biorefinery concepts. In this paper, some particular aspects of the chemistry of d-xylose reaction to furfural are addressed, with the aim to clarify the reaction mechanism leading to furfural and to define new green catalytic pathways for its production. Specifically, reducing the use of mineral acids is addressed by the introduction of alternative catalysts. In this sense, chloride salts were tested in dilute acidic solutions at temperatures between 170 and 200 °C. Results indicate that the Cl−ions promote the formation of the 1,2-enediol from the acyclic form of xylose, and thus the subsequent acid catalyzed dehydration to furfural. For this reason the presence of Cl−ions led to significant improvements with respect to the H2SO4case. The addition of NaCl to a 50 mM HCl aqueous solution gave 90% selectivity to furfural. Among the salts tested FeCl3showed very interesting preliminary results, producing exceptionally high xylose reaction rates. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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20. A green and efficient route for preparation of supported metal colloidal nanoparticles in scCO2Electronic supplementary information (ESI) available: N2adsorption and desorption isotherms; pore size distribution curves. See DOI: 10.1039/c004647g.
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Wang, Qiang, Cheng, Haiyang, Liu, Ruixia, Hao, Jianmin, Yu, Yancun, and Zhao, Fengyu
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NANOPARTICLES , *COLLOIDS , *CATALYSTS , *STABILIZING agents , *ACTIVE metals , *SOLVENTS , *SUSTAINABLE chemistry - Abstract
An efficient method for dispersing active metal colloidal nanoparticles onto supports uniformly is revealed in this paper. The critical feature of this method is to separate the stabilizer simply with the phase-switch function of scCO2; with it the highly dispersed Pd colloidal catalysts were prepared, and the forming procedure is analyzed and discussed in detail. The present work not only overcame the common difficulties of removing the stabilizers in the preparation of supported colloidal particles, but also provided a facile and green process for preparing supported metal colloidal nanoparticles with using the environmentally benign solvent of scCO2. [ABSTRACT FROM AUTHOR]
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- 2010
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21. An efficient synthesis of α-acyloxyacrylate esters as candidate monomers for bio-based polymers by heteropolyacid-catalyzed acylation of pyruvate esters.
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Wataru Ninomiya, Masahiro Sadakane, Shinji Matsuoka, Hiroki Nakamura, Hiroyuki Naitou, and Wataru Ueda
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MONOMERS , *PYRUVATES , *CATALYSTS , *POLYMERS , *INORGANIC acids , *CHEMICAL reactions , *ORGANIC acids - Abstract
A series of α-acyloxyacrylate esters are candidate monomers for bio-based polymers, converted from biomass feedstock. Polymers from these monomers are useful materials for bio-based plastics showing high heat resistance and transparency. In this paper, a new efficient method for α-acyloxyacrylate ester synthesis with a strong inorganic acid, heteropolyacid, is presented. The reaction in the presence of the heteropolyacid catalyst was carried out in liquid phase under mild conditions and showed higher productivity than that of the conventional synthesis with a typical organic acid, p-toluenesulfonic acid. Among the various heteropolyacids examined, α-Keggin-type tungsten-based phosphotungstic acid, H3PW12O40, showed the best performance, suggesting that the acid strength of the heteropolyacid is the crucial property for this reaction. We also found that pyruvate ester was consecutively converted into α-acyloxyacrylate ester via2,2-diacyloxypropionate ester. [ABSTRACT FROM AUTHOR]
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- 2009
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22. Grafting sulfated zirconia on mesoporous silica.
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Kwan-Young LeeOn leave from Deptartment of Chemical Engineering, Korea University, Korea., Saemin ChoiPresent address: Visteon Corporation, Jun Liu, Li-Qiong Wang, and Charles H. F. Peden
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ZIRCONIUM oxide , *SILICA , *CATALYSTS , *ISOPROPYL alcohol - Abstract
Recently, sulfated zirconia has received considerable attention as a potential solid acid catalyst to replace problematic homogeneous acid catalysts. In this paper, the preparation and properties of acid catalysts obtained by grafting ziconia with atomic precision on MCM-41 mesoporous silica were studied. TEM and potential titration characterizations revealed that ZrO2/MCM-41 with monolayer coverage can be obtained using this grafting technique. Sulfated ZrO2/MCM-41 exhibits improved thermal stability than that of bulk sulfated zirconia, as evidenced by temperature programmed characterizations and XRD analysis. Temperature programmed reaction of isopropanol was used to evaluate the acidity of sulfated ZrO2/MCM-41. It was found that the acid strength of sulfated ZrO2/MCM-41 with monolayer coverage is weaker than bulk sulfated zirconia but stronger than SiO2–Al2O3, a common strong acid catalyst. [ABSTRACT FROM AUTHOR]
- Published
- 2007
23. Integrated design of an amination process of lignin oxygenated model compounds to synthesize cyclohexylamine: catalyst nanostructure engineering and catalytic conditional strategy.
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Ji, Na, Lei, Yaxuan, Yu, Zhihao, Li, Hanyang, Diao, Xinyong, Lu, Xuebin, and Wang, Shurong
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CYCLOHEXYLAMINE , *LIGNIN structure , *AMINATION , *LIGNINS , *BIOMASS chemicals , *CATALYSTS , *CYCLOHEXANONES - Abstract
Nowadays, the vigorous development of biomass catalytic valorization is gradually moving towards a promising era. Integrating nitrogen elements into biomass catalytic systems promises more possibilities for upgrading the roadmap of biomass feedstocks. The amination of lignin to cyclohexylamine and its derivatives is a potential alternative to the fossil-based pathway. One-pot catalytic amination of lignin model compounds is challenging and inefficient due to their structural characteristics. Concerning the amination pathway, cyclohexanone and cyclohexanol are important intermediates. Based on this, we discuss the structural preferences of catalysts in the selective hydrogenation process, as well as the amination process of cyclohexanone and cyclohexanol to guide the design of catalysts for the one-pot amination of lignin. Then, the catalytic amination systems are deeply analyzed based on their catalytic conditions. Finally, according to the current development status of lignin amination, the challenges and prospects are proposed for a better lignin valorization. [ABSTRACT FROM AUTHOR]
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- 2022
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24. Iridium supported on porous polypyridine-oxadiazole as high-activity and recyclable catalyst for the borrowing hydrogen reaction.
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Li, Jiahao, Mao, Anruo, Yao, Wei, Zhu, Haiyan, and Wang, Dawei
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CATALYSTS , *HETEROGENEOUS catalysts , *IRIDIUM catalysts , *BENZYL alcohol , *IRIDIUM , *CATALYTIC activity , *WASTE recycling ,CATALYSTS recycling - Abstract
Homogenization of heterogeneous catalysts is a valuable and interesting research topic. Porous polypyridine-oxadiazole (PPO), as not only a carrier but also a ligand, was designed and synthesized from pyridine-oxadiazole and 1-iodo-4-vinylbenzene. Iridium was anchored onto the skeleton of this polymer (ligand) through coordination bonds. This porous polypyridine-oxadiazole iridium catalyst (PPO-Ir) was clearly characterized by XRD, BET, EDS, HRTEM, SEM, and XPS, and revealed high catalytic activity for the reaction of dimethyl-6-aminouracil with benzyl alcohols, 1,3-dimethylbarbituric acid with benzyl alcohols and 2-aminobenzylamine and benzyl alcohols through dehydrogenation and the borrowing hydrogen strategy with alcohol or water as the solvent. In addition, this PPO-Ir catalyst could be recycled and reused without a manifest loss of catalytic activity for at least five times and revealed potential application value. The mechanism explorations were further conducted to clarify this PPO-Ir and these transformations. [ABSTRACT FROM AUTHOR]
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- 2022
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25. Solvent effect on xylose-to-furfural reaction in biphasic systems: combined experiments with theoretical calculations.
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Lin, Qixuan, Zhan, Qiwen, Li, Rui, Liao, Shouwei, Ren, Junli, Peng, Feng, and Li, Libo
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MOLECULAR dynamics , *DENSITY functional theory , *PARTITION coefficient (Chemistry) , *ORGANIC solvents , *SOLVENTS , *FURFURAL , *CATALYSTS - Abstract
The present report focuses on the solvent effect on furfural production from xylose in biphasic systems with methods including combined experiments, molecular dynamics (MD) simulations and density functional theory (DFT) calculations. Six most effective and commonly used biphasic solvents for furfural production were comparatively analyzed and discussed based on the kinetic study, partition coefficient, degradation behavior of furfural in organic solvents, distribution of solvent molecules around xylose/furfural molecules, hydrogen bonding, moving trajectories of xylose/furfural, and the solvation free energy. During the hydrothermal reaction of xylose to furfural in biphasic systems, it was found that the conversion efficiency of biphasic systems can be ordered as DCM/H2O > 2-MTHF/H2O > 2-butanol/H2O ≈ MIBK/H2O > CPME/H2O > toluene/H2O according to the xylose conversion and furfural yield, which are dominated by the solvation free energy (ΔGsol) of furfural in organic solvents, and also be affected by three other factors, namely, the maximum solubility of furfural in organic solvents, the ΔGsol value of organic solvents in water, and the side reaction of furfural in organic solvents. The degradation rate of furfural in 2-butanol was detected to be the fastest, and molecular dynamics simulation data showed that the hydrogen bonding between furfural and 2-butanol may accelerate the degradation of furfural. DCM has excellent extraction ability for furfural, and the maximum furfural yield in the DCM/H2O system (81.64%) is much higher than that in other systems during the hydrothermal reaction without additional catalysts. [ABSTRACT FROM AUTHOR]
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- 2021
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26. Fabrication of lignin nanospheres by emulsification in a binary γ-valerolactone/glycerol system and their application as a bifunctional reducer and carrier for Pd nanoparticles with enhanced catalytic activity.
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Wang, Guanhua, Pang, Tairan, Chen, Shilin, Sui, Wenjie, Si, Chuanling, and Ni, Yonghao
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LIGNINS , *NANOPARTICLES , *CATALYTIC activity , *GLYCERIN , *FORMIC acid , *CHEMICAL stability , *CATALYSTS - Abstract
Lignin nanosizing has received much interest as it offers new potential for value-added applications of the currently under-utilized lignin biopolymers. However, conventional lignin nanosizing technologies often rely on the use of large amounts of toxic organic solvents, and a time-consuming dialysis process that is required to remove the solvents. Herein, we present a novel and effective approach using a binary system consisting of green γ-valerolactone (GVL) and glycerol solvents to prepare lignin nanospheres (LNS) without lignin modification and additional dialysis processes. The rationale of LNS formation lies in the emulsification of uniform lignin-containing GVL droplets in glycerol by a process consisting of (1) heating to 80 °C, and (2) cooling to room temperature. Through this simple process, we obtained very high LNS yield (over 90%), with narrow size distribution (about 275 nm) by using maple kraft lignin as the raw material. This lignin nanosizing approach is universal when applied to different sources/types of lignins. The as-prepared LNS were further applied as a green reducing agent and carrier for the synthesis of Pd nanoparticles (NPs) in a facile in situ reduction process. Pd@LNS exhibited significantly enhanced catalytic capacity in the hydrogen evolution from formic acid and in the reduction of Cr(VI) to Cr(III) compared with bare Pd NPs. The Pd@LNS catalyst demonstrated high recyclability owing to the good chemical stability of LNS and robust loading of Pd NPs on LNS. Consequently, this work offers a green, universal and effective approach for LNS fabrication and presents a promising application of LNS as metal NP carriers for catalysis purposes. [ABSTRACT FROM AUTHOR]
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- 2020
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27. Oxidative cleavage of β-O-4 bonds in lignin model compounds with a single-atom Co catalyst.
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Liu, Sijie, Bai, Lichen, van Muyden, Antoine P., Huang, Zhangjun, Cui, Xinjiang, Fei, Zhaofu, Li, Xuehui, Hu, Xile, and Dyson, Paul J.
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SCISSION (Chemistry) , *LIGNINS , *CATALYSTS , *OXYGEN compounds - Abstract
Single-atom catalysts are emerging as primary catalysts for many reactions due to their 100% utilization of active metal centers leading to high catalytic efficiencies. Herein, we report the use of a single-atom Co catalyst for the oxidative cleavage of the β-O-4 bonds of lignin model compounds at a low oxygen pressure. Under the optimized reaction conditions, the conversion of 2-(2-methoxyphenoxy)-1-phenylethanol up to 95% with high selectivities was achieved with a variety of substrates investigated. The reusability of the Co catalyst with a high catalytic efficiency indicates its potential application in the oxidative cleavage of C–O bonds. [ABSTRACT FROM AUTHOR]
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- 2019
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28. Selective aerobic oxidation of biomass-derived HMF to 2,5-diformylfuran using a MOF-derived magnetic hollow Fe–Co nanocatalyst.
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Fang, Ruiqi, Luque, Rafael, and Li, Yingwei
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OXIDATION , *POLYMERS , *HYDROXYMETHYLFURFURAL , *CATALYSTS , *BIOMASS - Abstract
The conversion of renewable biomass resources into fuels, polymers, and fine chemicals provides solutions for the growing shortage of fossil resources, environmental pollution and a possible crisis in energy supply. 5-Hydroxymethylfurfural (HMF) is an important biomass-derived platform chemical, and its selective oxidation to multifunctional molecules such as 2,5-diformylfuran (DFF) remains an ongoing challenge. The present work reports a sustainable, cost-effective, and highly efficient catalytic system for directly transforming HMF to DFF that afforded >99% DFF yield under relatively mild reaction conditions. The reaction was catalyzed by naturally abundant and non-noble Fe–Co based catalysts derived from a metal–organic framework (MIL-45b) employed as a sacrificial template. The unique hollow structure of the nanomaterial favored the adsorption of HMF and quick desorption of the formed DFF from the catalyst surface, leading to a high yield of DFF that could be comparable to that obtained with noble metal catalysts under similar conditions. The catalyst could also be easily recovered and reused up to six runs without any significant loss in reactivity. [ABSTRACT FROM AUTHOR]
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- 2016
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29. Efficient and selective aerobic oxidation of alcohols catalysed by MOF-derived Co catalysts.
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Bai, Cuihua, Li, Aiqin, Yao, Xianfang, Liu, Hongli, and Li, Yingwei
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ALCOHOLS (Chemical class) , *OXIDATION , *CATALYSTS , *NANOPARTICLES , *CHEMICAL synthesis , *RAMAN spectroscopy , *X-ray photoelectron spectroscopy - Abstract
A simple and highly efficient nanostructured catalyst system comprising magnetic Co nanoparticles stabilized by N-doped carbon composite (Co/C–N) was synthesized by one-pot thermal decomposition of a Co-containing MOF. The catalysts were characterized by temperature programmed desorption (TPD), N2 physical adsorption, powder X-ray diffraction (PXRD), Raman spectroscopy, transmission electron microscopy (TEM), scanning electronic microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The catalytic activity of Co/C–N materials was investigated in the selective aerobic oxidation of alcohols in neat water under an atmospheric pressure of air and base-free conditions. As compared to those prepared by traditional impregnation methods, Co/C–N exhibited an efficient performance with significantly improved catalytic activities. Besides conferring high activity and selectivity to the target products, the proposed catalytic system featured a broad substrate scope for both aryl and alkyl alcohols. Furthermore, the magnetically recoverable Co/C–N catalyst could be easily separated from the reaction system by using an external magnetic field and reused at least five times without any significant loss in catalytic efficiency under the investigated conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
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