Topic
Cyclohexane
About: Cyclohexane is a research topic. Over the lifetime, 11706 publications have been published within this topic receiving 173665 citations. The topic is also known as: Benzene hexahydride & Hexahydrobenzene.
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TL;DR: Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide and the catalytic selectivity was found to be strongly affected by the nanoparticle shape.
Abstract: Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-H...Pt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for cyclohexane production on cubic nanoparticles is 10.9 +/- 0.4 kcal/mol, while for cuboctahedral nanoparticles, the apparent activation energies for cyclohexane and cyclohexene production are 8.3 +/- 0.2 and 12.2 +/- 0.4 kcal/mol, respectively. These activation energies are lower, and corresponding turnover rates are three times higher than those obtained with single-crystal Pt surfaces.
800 citations
TL;DR: It is demonstrated that the simple, commercially available room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) is a unique soft template for the easy synthesis of boronand fluorineenriched mesoporous polymeric carbon nitride, in which an organic precursor, for example dicyandiamide (DCDA), selfcondensed intocarbon nitride solids in the
Abstract: Recently, various lightweight materials with diverse nanomorphologies that contain heteroatoms such as nitrogen, boron, or fluorine have been actively pursued because of their unusual properties, such as in catalytic applications or as semiconductors. For example, ordered and disordered modifications of carbon nitride (C3N4) extend the property profile of carbon nanostructures and have numerous potential areas of applications ranging from semiconductors to fuel cells. A large number of reports deals with the synthesis of different modifications of bulk CxNy materials. [2] The synthesis of these nitrogen-rich species generally includes thermal condensation of nitrogen-rich precursors, often from molecules containing or generating triazine rings. For example, through a solid-state reaction of 2,4,6-triamino-1,3,5-triazine with 2,4,6-trichloro-1,3,5-triazine at high pressure and high temperature, Wolf and co-workers obtained a well-characterized and highly crystalline graphitic carbon nitride derivative. However, it was shown that the more ideal bulk carbon nitride solids perform rather weakly in some catalytic processes, while more disordered, polymeric versions showed nice activity, as structural defects or surface terminations seemed to play a key role for the catalytic activation. To enhance the performance of carbon nitride both as a support and as a catalyst, the specific surface had to be enhanced, and nanocasting with hard templates using porous silicas has been explored recently for the replication of porous carbon nitride materials with controlled mesopore structures. This nanocasting method is good for the proof of principle, but it is hardly transferable to a practical process, as the templates have to be removed in an extra step involving aqueous ammonium bifluoride (NH4HF2) or hydrogen fluoride (HF), which are hazardous and not environmentally friendly and also prohibit further functionalization. A general and robust method for the synthesis of porous polymeric carbon nitrides without the extra step of removing hard templating silica structures has yet to be developed. Ionic liquids are an especially promising choice to achieve this aim. Ionic liquids are generally defined as organic salts with a low melting point, usually below 100 8C. They inherit many features of inorganic molten salts, such as excellent chemical and thermal stability (in some cases in excess of 400 8C) and negligibly small vapor pressure, with the convenience of being liquid under ambient conditions. They have found application in numerous fields, for example as solvents or catalysts in organic synthesis, as electrolytes, or in chemical separations. Recently, the advantages of ionic liquids in inorganic synthesis have been gradually realized and have received more and more attention. For instance, they turned out to be interesting solvents in the synthesis of nanoparticles owing to their special solvent structure that derives from the ion–ion interaction and extended hydrogen-bonding motifs. From the many different available ionic liquids, we chose a class with BF4 counterions, as the anion might enter the C N condensation scheme, while boron and fluorine doping could improve the catalytic activity of the discussed systems and contribute to the performance of such materials. Herein we demonstrate that the simple, commercially available room-temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate (BmimBF4) is a unique soft template for the easy synthesis of boronand fluorineenriched mesoporous polymeric carbon nitride, in which an organic precursor, for example dicyandiamide (DCDA), selfcondensed into carbon nitride solids in the presence of BmimBF4. We show that the resulting materials possess high nitrogen, boron, and fluorine contents, high surface area, local graphitic order, and an excellent photoconductivity under visible light. We also demonstrate the catalytic properties of these CNBF materials in the heterogeneous, metal-free oxidation of cyclohexane. The CNBF materials show nice performance in the oxidation of cyclohexane with good conversion and excellent cyclohexanone selectivity. The structures of these hybrid materials were investigated by powder X-ray diffraction (XRD), nitrogen gas adsorption, and transmission electron microscopy (TEM) measurements. The XRD pattern, for example of CNBF-0.3 (r = 0.3, r denotes the mass ratio of BmimBF4 to DCDA), is dominated by the (002) interlayer-stacking peak of carbon nitrides, [*] Dr. Y. Wang, Prof. Dr. X. Wang, Prof. Dr. M. Antonietti Department of Colloid Chemistry Max-Planck Institute of Colloids and Interfaces Research Campus Golm, 14424 Potsdam (Germany) Fax: (+ 49)331-567-9502 E-mail: yong.wang@mpikg.mpg.de
626 citations
TL;DR: In this article, the most interesting systems for the cyclohexane synthesis with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen were reviewed.
Abstract: Many efforts have been made to develop new catalysts to oxidize cyclohexane under mild conditions. Herein, we review the most interesting systems for this process with different oxidants such as hydrogen peroxide, tert -butyl hydroperoxide and molecular oxygen. Using H 2 O 2 , Na-GeX has been shown to be a most stable and active catalyst. Mesoporous TS-1 and Ti-MCM-41 are also stable, but the use of other metals such as Cr, V, Fe and Mo leads to leaching of the metal. Homogeneous systems based on binuclear manganese(IV) complexes have also been shown to be interesting. When t -BuOOH is used, the active systems are those phthalocyanines based on Ru, Co and Cu and polyoxometalates of dinuclear ruthenium and palladium. Microporous metallosilicates containing different transition metals showed leaching of the metal during the reactions. Molecular oxygen can be used directly as an oxidant and decreases the leaching of active species in comparison to hydrogen peroxide and tert -butyl hydroperoxide. Metal aluminophosphates (metal: Mn, Fe, Co, Cu, Cr V) are active and relatively stable under such conditions. Mn-AlPO-36 yields directly adipic acid, but large amounts of carboxylic acids should be avoided, as they cause metal leaching from the catalysts. Rare earth exchanged zeolite Y also shows good selectivity and activity. In the last part of the review, novel alternative strategies for the production of cyclohexanol and cyclohexanone and the direct synthesis of adipic acid are discussed.
585 citations
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TL;DR: In this article, the effect of adding copper to nickel was investigated for the hydrogenolysis of ethane to methane and the dehydrogenation of cyclohexane to benzene over a series of copper-nickel alloys.
585 citations
TL;DR: In this paper, a new theory of solvent effects on the optical rotations of chiral molecules is presented, where the frequency-dependent electric dipole−magnetic dipole polarizability, βαβ(ν), is calculated using density functional theory (DFT).
Abstract: A new theory of solvent effects on the optical rotations of chiral molecules is presented. The frequency-dependent electric dipole−magnetic dipole polarizability, βαβ(ν), is calculated using density functional theory (DFT). Solvent effects are included using the polarizable continuum model (PCM). DFT/PCM calculations of sodium D line specific rotations, [α]D, have been carried out for seven conformationally rigid chiral organic molecules (fenchone, camphor, α-pinene, β-pinene, camphorquinone, verbenone, and methyloxirane) for a diverse set of seven solvents (cyclohexane, carbon tetrachloride, benzene, chloroform, acetone, methanol, and acetonitrile). The predicted variation in [α]D for the solvents cyclohexane, acetone, methanol, and acetonitrile are in excellent agreement with experiment for all seven molecules. For the solvents carbon tetrachloride, benzene, and chloroform, agreement is much poorer. Since only electrostatic solute−solvent interactions are included in the PCM, our results lead to the con...
580 citations