T:Toxic;
108-95-2Relevant articles and documents
Chlorine-nickel interactions in gas phase catalytic hydrodechlorination: Catalyst deactivation and the nature of reactive hydrogen
Shin, Eun-Jae,Spiller, Andreas,Tavoularis, George,Keane, Mark A.
, p. 3173 - 3181 (1999)
The gas phase hydrodechlorination of chlorobenzene and 3-chlorophenol (where 473 K ≤ T ≤ 573 K) has been studied using a 1.5% w/w Ni/SiO2 catalyst which was also employed to promote the hydrogenation of benzene, cyclohexene and phenol. In the former two instances the catalyst was 100% selective in removing the chlorine substituent, leaving the aromatic ring intact. While the dechlorination of chlorobenzene readily attained steady state with no appreciable deactivation, the turnover of 3-chlorophenol to phenol was characterised by both a short and a long term loss of activity. Chlorine coverage of the catalyst surface under reaction conditions was probed indirectly by monitoring, via pH changes in an aqueous NaOH trap, HCI desorption after completion of the catalytic step. Contacting the catalyst with the chlorinated reactants was found to severely limit and, depending on the degree of contact, completely inhibit aromatic ring reduction although a high level of hydrodechlorination activity was maintained. Hydrogen temperature programmed desorption (TPD) reveals the existence of three forms of surface hydrogen which are tentatively assigned as: (i) hydrogen bound to the surface nickel; (ii) hydrogen at the nickel/silica interface; (iii) spillover hydrogen on the silica support. The effect of chlorine-nickel interactions on the resultant TPD profiles is presented and discussed. The (assigned) spillover hydrogen appears to be hydrogenolytic in nature and is responsible for promoting hydrodechlorination while the hydrogen that is taken to be chemisorbed on, and remains associated with, the surface nickel metal participates in aromatic hydrogenation. Hydrodechlorination proceeds via an electrophilic mechanism, possibly involving spillover hydronium ions. The experimental catalytic data are adequately represented by a kinetic model involving non-competitive adsorption between hydrogen and the chloroaromatic, where incoming chloroaromatic must displace the HCI that remains on the surface after the dechlorination step. Kinetic parameters extracted from the model reveal that chlorophenol has a higher affinity than chlorobenzene for the catalyst surface but the stronger interaction leads to a greater displacement of electron density at the metal site and this ultimately leads to catalyst deactivation.
Facile synthesis of CuCr2O4 spinel nanoparticles: A recyclable heterogeneous catalyst for the one pot hydroxylation of benzene
Acharyya, Shankha S.,Ghosh, Shilpi,Adak, Shubhadeep,Sasaki, Takehiko,Bal, Rajaram
, p. 4232 - 4241 (2014)
A facile hydrothermal synthesis method is developed to prepare CuCr2O4 spinel nanoparticle catalysts with sizes between 25-50 nm. A detailed characterization of the material was carried out by XRD, ICP-AES, XPS, EXAFS, SEM, TEM, and TGA. XRD revealed the formation of a CuCr2O4 spinel phase and TEM showed the that particles size was 20-50 nm. The catalyst was highly active for the selective oxidation of benzene to phenol with H2O2. The influence of reaction parameters such as temperature, solvent, substrate to oxidant molar ratio, reaction time, etc. were investigated in detail. The reusability of the catalyst was tested by conducting the same experiments with the spent catalyst and it was found that the catalyst did not show any significant activity loss, even after 5 reuses. A benzene conversion of 72.5% with 94% phenol selectivity was achieved over this catalyst at 80 °C. However, significant H2O2 decomposition occurs on the catalyst, necessitating its usage in five-fold excess.
Debromination of 2,4,6-tribromophenol coupled with biodegradation
Weidlich, Tomas,Prokes, Lubomir,Pospisilova, Dagmar
, p. 979 - 987 (2013)
The application effect of aluminium and their alloys and mixtures with nickel was studied for the complete hydrodebromination of 2,4,6-tribromophenol (TBP) to phenol in aqueous NaOH solution at room temperature. It was found that the Raney Al-Ni alloy can
Mixed-donor N,N,O-tridentate ligands for palladium-catalyzed Suzuki reactions
Zhou, Zhonggao,Du, Ziyi,Hu, Qiaosheng,Shi, Jicheng,Xie, Yongrong,Liu, Yulan
, p. 149 - 153 (2012)
Efficient Suzuki-Miyaura cross-coupling reactions of arylboronic acids with aryl halides catalyzed by Pd/N,N,O-tridentate ligands, using methanol as solvent and K3PO4 as base, afforded the corresponding cross-coupled biaryls in good to excellent yields. Springer Science+Business Media B.V. 2012.
Photocatalytic degradation of 2,4-dichlorophenol with V2O5-TiO2 catalysts: Effect of catalyst support and surfactant additives
Sinirtas, Eda,Isleyen, Meltem,Soylu, Gulin Selda Pozan
, p. 607 - 615 (2016)
Binary oxide catalysts with various weight percentage V2O5 loadings were prepared by solid-state dispersion and the nanocomposites were modified with surfactants. The catalysts were analyzed using X-ray diffraction, diffuse-reflectance spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption-desorption. The photocatalytic activities of the catalysts were evaluated in the degradation of 2,4-dichlorophenol under ultraviolet irradiation. The photocatalytic activity of 50 wt% V2O5-TiO2 (50V2O5-TiO2) was higher than those of pure V2O5, TiO2, and P25. Interactions between V2O5 and TiO2 affected the photocatalytic efficiencies of the binary oxide catalysts. Cetyltrimethylammonium bromide (CTAB) and hexadecyltrimethylammonium bromide (HTAB) significantly enhanced the efficiency of the 50V2O5-TiO2 catalyst. The highest percentage of 2,4-dichlorophenol degradation (100%) and highest reaction rate (2.22 mg/(L·min)) were obtained in 30 min with the (50V2O5-TiO2)-CTAB catalyst. It is concluded that the addition of a surfactant to the binary oxide significantly enhanced the photocatalytic activity by modifying the optical and electronic properties of V2O5 and TiO2.
Synthesis, structural characterization, and catalytic activity of IPrNi(styrene)2 in the amination of aryl tosylates
Iglesias, Maria Jose,Blandez, Juan F.,Fructos, Manuel R.,Prieto, Auxiliadora,Alvarez, Eleuterio,Belderrain, Tomas R.,Nicasio, M. Carmen
, p. 6312 - 6316 (2012)
A novel bis-styrene IPrNi0 derivative has been synthesized from the reaction of Ni(COD)2 and free 1,3-bis(2,6-diisopropylphenyl) imidazolidene (IPr) ligand in the presence of styrene. The complex has been characterized by spectroscopic data as well as by X-ray crystallography. Its catalytic performance in the amination reaction of aryl tosylates is also reported. The catalytic reactions proceed in a very selective manner, affording moderate to high yields of cross-coupling products in short reaction times at 110 °C.
Spectroscopic and QM/MM investigations of Chloroperoxidase catalyzed degradation of orange G
Zhang, Rui,He, Qinghao,Huang, Yi,Wang, Xiaotang
, p. 1 - 9 (2016)
Chloroperoxidase (CPO), a heme-thiolate protein, from Caldariomyces fumago catalyzes a plethora of reactions including halogenation, dismutation, epoxidation, and oxidation. Although all CPO-catalyzed reactions go through a common intermediate, compound I, different mechanisms are followed in subsequent transformations. To understand the mechanism of CPO-catalyzed halide-dependent degradation of orange G, the role of halide and pH was systematically investigated. It is revealed that formation and protonation of compound X, a long-sought after hypochlorite heme adduct intermediate existed during CPO-catalyzed halide-dependent reactions, significantly lowers the reaction barrier and increases the efficiency of CPO-catalyzed orange G degradation. The extremely acidic optimal reaction pH suggests the protonation of a residue, presumably, Glu 183 in CPO catalysis. Halide dependent studies showed that Kcat is higher in the presence of Br- than in the presence of Cl-. The degradation products of orange G indicate the cleavage at a single position of orange G, demonstrating a high regioselectivity of CPO-catalyzed degradation. Based on our kinetic, NMR and QM/MM studies, the mechanism of CPO-catalyzed orange G degradation was proposed.
Evidence for HOOO radicals in the formation of alkyl hydrotrioxides (ROOOH) and hydrogen trioxide (HOOOH) in the ozonation of C - H bonds in hydrocarbons
Cerkovnik, Janez,Erzen, Evgen,Koller, Joze,Plesnicar, Bozo
, p. 404 - 409 (2002)
Low-temperature ozonation of cumene (1a) in acetone, methyl acetate, and tert-butyl methyl ether at -70° C produced the corresponding hydrotrioxide, C6H5C(CH3)2OOOH (2a), along with hydrogen trioxide, HOOOH. Ozonation of triphenylmethane (1b), however, produced only triphenylmethyl hydrotrioxide, (C6H5)3COOOH (2b). These observations, together with the previously reported experimental evidence, seem to support the "radical" mechanism for the first step of the ozonation of the C - H bonds in hydrocarbons, i.e., the formation of the caged radical pair (R??OOOH), which allows both (a) collapse of the radical pair to ROOOH and (b) the abstraction of the hydrogen atom from alkyl radical R? by HOOO? to form HOOOH. The B3LYP/6-311++G(d,p) (ZPE) calculations revealed that HOOO radicals are considerably stabilized by forming intermolecularly hydrogen-bonded complexes with acetone (BE = 8.55 kcal/mol) and dimethyl ether (7.04 kcal/mol). This type of interaction appears to be crucial for the relatively fast reactions (and the formation of the polyoxides in relatively high yields) in these solvents, as compared to the ozonations run in nonbasic solvents. However, HOOO radicals appear to be not stable enough to abstract hydrogen atoms outside the solvent cage, as indicated by the absence of HOOOH among the products in the ozonolysis of triphenylmethane. The decomposition of alkyl hydrotrioxides 2a and 2b involves a homolytic cleavage of the RO-OOH bond with subsequent "in cage" reactions of the corresponding radicals, while the decomposition of HOOOH is most likely predominantly a "pericyclic" process involving one or more molecules of water acting as a bifunctional catalyst to produce water and singlet oxygen (Δ1O2).
Solvent-Induced Single Crystal-Single Crystal Transformation of an Interpenetrated Three-Dimensional Copper Triazole Catalytic Framework
Wang, Ying,Meng, Shan-Shan,Lin, Peng-Xiang,Xiao, Yi-Wei,Ma, Qing-Qing,Xie, Qiong,Chen, Yuan-Yuan,Zhao, Xiao-Jun,Chen, Jun
, p. 4069 - 4071 (2016)
The 2-fold interpenetrated 3D framework 1 can be solvent-induced to noninterpenetrated framework 1′ in a reversible single crystal-single crystal transformation fashion. In addition, 1′ represents the first catalyst based on triazole to catalyze the aerobic homocoupling of various substituted arylboronic acids.
2,2,6,6-Tetramethylpiperidine-1-Oxyl-promoted hydroxylation of benzene to phenol over a vanadium-based catalyst using molecular oxygen
Chen, Jiaqi,Gao, Shuang,Li, Jun,Lue, Ying
, p. 1446 - 1451 (2011)
Rapid benzene hydroxylation was achieved using a reaction system that consisted of a vanadium-based catalyst, ascorbic acid, and 2,2,6,6- tetramethylpiperidine-1-oxyl (TEMPO) with molecular oxygen as the oxidant. The hydroxyl radicals that form by a Fento
