Journal of Molecular Catalysis A: Chemical最新文献

{"title":"Epoxy monomers obtained from castor oil using a toxicity-free catalytic system","authors":"Natalia L. Parada Hernandez ,&nbsp;Anderson J. Bonon ,&nbsp;Juliana O. Bahú ,&nbsp;Maria Ingrid R. Barbosa ,&nbsp;Maria Regina Wolf Maciel ,&nbsp;Rubens Maciel Filho","doi":"10.1016/j.molcata.2016.08.005","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.08.005","url":null,"abstract":"<div><p>In order to obtain monomers from vegetable source, the castor oil epoxidation process was investigated. The catalytic system used in this work, H₂O₂/alumina/ethyl acetate, can be considered as a green system, free of heavy metals and toxic solvents. These characteristics make the system appropriate for the purpose of this study since they increase the probabilities of obtaining a biomaterial with the desired specifications regarding toxicity. Reaction conditions of castor oil epoxidation were optimized using methyl ricinoleate as a model compound. In order to identify the operating region, it was developed an experimental design 2³ with 17 assays (6 axial points and central point in triplicate) in which, methyl ricinoleate, hydrogen peroxide and catalyst initial quantities in the reaction mixture were the studied variables. The system showed great efficiency with 100% of selectivity in the methyl ricinoleate epoxide production. In optimized conditions, it showed conversion of 99% in 6<!--> <!-->h. It was obtained a conversion of 94%, an epoxidation percentage of 84 and a selectivity of 89% toward the epoxides for the castor oil epoxidation. These results show the efficacy of the catalytic system used in this work. Epoxidized castor oil structure was confirmed by FTIR, Raman and ¹H NMR techniques.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 550-556"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.08.005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2660118","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oxidation of aromatic compounds by hydrogen peroxide catalyzed by mononuclear iron(III) complexes","authors":"Giselle C. Silva ,&nbsp;Nakédia M.F. Carvalho ,&nbsp;Adolfo Horn Jr. ,&nbsp;Elizabeth R. Lachter ,&nbsp;Octavio A.C. Antunes","doi":"10.1016/j.molcata.2016.08.037","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.08.037","url":null,"abstract":"<div><p>In the present work, four mononuclear iron(III) complexes containing BMPA (BMPA<!--> <!-->=<!--> <!-->bis-(2-pyridylmethyl)amine) and derivative ligands, have been studied as catalyst in toluene oxidation, at 25<!--> <strong>°</strong>C and 50<!--> <strong>°</strong>C, using hydrogen peroxide as oxidant and acetonitrile as solvent. All catalysts were able to oxidize toluene with satisfactory yields, producing <em>o</em>-, <em>m</em>-, <em>p</em>-cresols, benzaldehyde and benzyl alcohol, as main products, and traces of 2-methylbenzoquinone and benzoic acid. The catalyst [Fe(BMPA)Cl₃] presented the most promising results, reaching yields up to 30.2% at 50<!--> <strong>°</strong>C after 24<!--> <!-->h. Furthermore, [Fe(BMPA)Cl₃] was applied in the oxidation of other aromatic compounds as benzene, ethylbenzene, cumene, <em>n</em>-propylbenzene, <em>p</em>-xylene and anisole. The reaction with H₂O₂ was monitored by electronic UV–vis spectroscopy in the presence and absence of toluene and its oxidation products, as well as by ESI-(+)-MS/Q-TOF mass spectrometry, in order to provide some information about the reaction mechanism.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 564-571"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.08.037","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2391731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zeolite catalyzed highly selective synthesis of 2-methoxy-6-acetylnaphthalene by Friedel-Crafts acylation of 2-methoxynaphthalene in acetic acid reaction media","authors":"Tomoyoshi Yamazaki,&nbsp;Makoto Makihara,&nbsp;Kenichi Komura","doi":"10.1016/j.molcata.2016.11.012","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.11.012","url":null,"abstract":"<div><p>Zeolite catalyzed Friedel-Crafts acetylation of 2-methoxynaphthalene to produce 2-methoxy-6-acetylnaphthalene with high selectivity and conversion has been a challenging task, because the obtained compound is a key intermediate for an anti-inflammatory agent, Naproxen. However, no satisfactory results have been obtained with zeolite catalysts, and harmful solvents have been used to gain a high selectivity together with a high conversion. Here, we report the synthesis of 2-methoxy-6-acetylnaphthalene from 2-methoxynaphthalene with a high selectivity and a high conversion under an unprecedented simple reaction system; acetic anhydride as an acetylating agent, acetic acid as a solvent, and proton-type zeolite catalysts with low acidity. Among the examined zeolites, a proton-type H-MOR (SiO₂/Al₂O₃ <!-->=<!--> <!-->200) with a low acid content shows a conversion of 82% and an 86% selectivity for 2-methoxy-6-acetylnaphthalene. Further, detailed control experiments using H-MOR catalyst in acetic acid solvent were carried out to propose a plausible reaction mechanism.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 170-176"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.11.012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2878507","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High yields of piperylene in the transfer dehydrogenation of pentane catalyzed by pincer-ligated iridium complexes","authors":"Akshai Kumar ,&nbsp;Jason D. Hackenberg ,&nbsp;Gao Zhuo ,&nbsp;Andrew M. Steffens ,&nbsp;Oleg Mironov ,&nbsp;Robert J. Saxton ,&nbsp;Alan S. Goldman","doi":"10.1016/j.molcata.2016.10.019","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.10.019","url":null,"abstract":"<div><p>Conjugated dienes are desirable reagents for several important applications. We report that sterically uncrowded PCP-pincer iridium complexes, including precursors of (<em>ⁱ</em>^Pr4PCP)Ir and (^{Me2<em>t</em>Bu2}PCP)Ir, catalyze the transfer dehydrogenation of pentane, using high concentrations of <em>t</em>‐butylethylene (TBE) as hydrogen acceptor, to give high yields of 1,3-pentadiene (piperylene). Piperylene yields are ca. 100-fold greater than those obtained with the more widely used di(t‐butyl)phosphino substituted pincer iridium catalysts. This represents, to our knowledge, the first reported high-yield synthesis of dienes via the dehydrogenation of <em>n</em>-alkane using molecular catalysts. To our knowledge, this is the first reported high-yield synthesis of dienes achieved via the dehydrogenation of n-alkane using molecular catalysts.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 368-375"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.10.019","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2391728","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ordered mesoporous MCo2O4 (M = Cu, Zn and Ni) spinel catalysts with high catalytic performance for methane combustion","authors":"Tae Hwan Lim ,&nbsp;Su Bin Park ,&nbsp;Ji Man Kim ,&nbsp;Do Heui Kim","doi":"10.1016/j.molcata.2016.11.002","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.11.002","url":null,"abstract":"<div><p>Ordered mesoporous MCo₂O₄ (M<!--> <!-->=<!--> <!-->Cu, Zn and Ni) spinel catalysts were synthesized via nano-replication method using mesoporous silica KIT-6 as the hard template. They were applied to methane combustion, in comparison with bulk MCo₂O₄ spinel catalysts prepared by co-precipitation method. A combined N₂ adsorption-desorption, XRD and TEM results clearly confirm that mesoporous MCo₂O₄ (m-MCo₂O₄) spinel catalysts contain ordered mesostructure, resulting in the higher BET surface area and pore volume than bulk ones (b-MCo₂O₄). Moreover, the former catalysts demonstrate the better thermal stability as indicated by larger amount of MCo₂O₄ phase and smaller size of crystallite domain after calcination at 550<!--> <!-->°C. Therefore, such excellent properties rationalize that the m-MCo₂O₄ spinel catalysts reveal higher catalytic activity for methane combustion than bulk counterparts. When it comes to the catalytic performance of the meso catalysts for methane combustion, the m-CuCo₂O₄ spinel catalyst has superior performance, which is related to the high normalized amount of Co³⁺ cations on the surface, as evidenced by XPS.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 68-74"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.11.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2878504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"DFT mechanistic study of reactions of С6H6 and 1,3,5-Ad3C6H3 with CBr3. The first example of hydride transfer from aromatic CH bond to electrophile","authors":"Yurii A. Borisov,&nbsp;Irena S. Akhrem","doi":"10.1016/j.molcata.2016.10.027","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.10.027","url":null,"abstract":"<div><p>The DFT B3LYP/6-31G* calculations were carried out for the reactions of C₆H₆ and Ad₃C₆H₃ (Ad<!--> <!-->=<!--> <!-->1,3,5-adamantyl) with superelectrophile CBr₃⁺ as a model of superelectrophilic catalyst CBr₃⁺ Al₂Br₇⁻. The reaction of C₆H₆ with CBr₃⁺ proceeds <em>via</em> the classical scheme of electrophilic reactions of aromatic C<!--> <!-->−<!--> <!-->H bond to form initially the barrier-free σ-complex C₆H₆CBr₃⁺. This mechanism was confirmed by the aug-cc-pVDZ basis set calculations. The reaction of Ad₃C₆H₃ with CBr₃⁺ occurs <em>via</em> a quite novel mechanism involving aryl cation formation followed by hydride abstraction of the Ar⁺ from the 2-Ad group and the rearrangement of the 2-Ad⁺ cation into the 4-phenyl-4-protoadamantyl cation. The hydride transfer from both arenes was shown to be more favorable than H radical transfer by more than 40 and 55<!--> <!-->kcal<!--> <!-->mol⁻¹ in the case of C₆H₆ and Ad₃C₆H₃, respectively.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 610-617"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.10.027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2798707","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The KA2 coupling reaction under green, solventless, heterogeneous catalysis","authors":"Giovanna Bosica,&nbsp;Roderick Abdilla","doi":"10.1016/j.molcata.2016.09.028","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.09.028","url":null,"abstract":"<div><p>Amberlyst A-21 supported CuI was found to be highly efficient novel heterogeneous catalyst for the three-component reaction between ketones, amines and alkynes, commonly called KA²-coupling. This inexpensive, easy-to-prepare, simple and recyclable catalyst has been employed in solventless conditions in the KA² coupling reaction involving both primary and secondary amines, ketones and various alkynes. The secondary and tertiary propargylamine products were obtained in good to excellent results in moderate reaction times.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 542-549"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.09.028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2595832","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rhodium-BiPhePhos catalyzed hydroformylation studied by operando FTIR spectroscopy: Catalyst activation and rate determining step","authors":"Andreas Jörke ,&nbsp;Andreas Seidel-Morgenstern ,&nbsp;Christof Hamel","doi":"10.1016/j.molcata.2016.10.028","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.10.028","url":null,"abstract":"<div><p>The homogeneously rhodium catalyzed hydroformylation of 1-decene was studied using operando FTIR spectroscopy. The bulky chelating diphosphite ligand BiPhePhos was used for catalyst modification. Special emphasis was given to the transformation of the Rh-precursor Rh(acac)(CO)₂ to the activated HRh(BiPhePhos)(CO)₂ catalyst. Under hydroformylation conditions, this complex was found to be the most abundant catalyst species over a wide range of olefin conversion. Other inactive or non-selective rhodium species were not detectable. Analysis of the turnover frequency revealed a first order dependence of the hydroformylation rate with respect to the concentration of 1-decene. These findings indicate that the coordination of the olefin to the Rh-BiPhePhos catalyst is determining the hydroformylation rate of 1-decene.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 10-14"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.10.028","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2595834","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of oxidative pre-treatment on hydrogen spillover for a Ni/SiO2 catalyst","authors":"Abdel-Ghani Boudjahem ,&nbsp;Mohammed M. Bettahar","doi":"10.1016/j.molcata.2016.11.014","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.11.014","url":null,"abstract":"<div><p>The chemisorption and hydrogenating properties of Ni/SiO₂ catalysts prepared by the hydrazine method then calcined at 400<!--> <!-->°C with various times were investigated. Metal dispersion and activity in benzene hydrogenation increased with increasing calcination time whereas desorbed amounts of hydrogen significantly decreased. Dilution of a calcined sample by the support led to a sharp increase of both hydrogen storage by the support and catalytic activity. Metal dispersion and hydrogen storage capacity influenced the reaction mechanisms of hydrogenation of benzene which, therefore, is believed to occur on the metal phase or/and on the support by the hydrogen spillover mechanism. The metal active phase would be composed of an ensemble of metallic and oxidized nickel species.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 190-197"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.11.014","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2171637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Catalytic C-H oxidations by nonheme mononuclear Fe(II) complexes of two pentadentate ligands: Evidence for an Fe(IV) oxo intermediate","authors":"Mainak Mitra ,&nbsp;Hassan Nimir ,&nbsp;David A. Hrovat ,&nbsp;Albert A. Shteinman ,&nbsp;Michael G. Richmond ,&nbsp;Miquel Costas ,&nbsp;Ebbe Nordlander","doi":"10.1016/j.molcata.2016.10.010","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.10.010","url":null,"abstract":"<div><p>The oxidation reactions of alkanes with hydrogen peroxide and peracids (peracetic acid (PAA) and <em>m</em>-chloroperoxybenzoic acid (mCPBA)) catalysed by two Fe(II) complexes of pentadentate {N₅}-donor ligands have been investigated. Kinetic isotope effect experiments and the use of other mechanistic probes have also been performed. While the total yields of oxidized products are similar regardless of oxidant (e.g. 30–39% for oxidation of cyclohexane), the observed alcohol/ketone ratios and kinetic isotope effects differ significantly with different oxidants. Catalytic reactions in H₂O₂ medium are consistent with the involvement of hydroxyl radicals in the C<img>H bond cleavage step, and resultant low kinetic isotope effect values. On the other hand, catalytic reactions performed using peracid media indicate the involvement of an oxidant different from the hydroxyl radical. For these reactions, the kinetic isotope effect values are relatively high (within a range of 4.2–5.1) and the C3/C2 selectivity parameters in adamantane oxidation are greater than 11, thereby excluding the presence of hydroxyl radicals in the C<img>H bond cleavage step. A low spin Fe(III)-OOH species has been detected in the H₂O₂-based catalytic system by UV/Vis, mass spectrometry and EPR spectroscopy, while an Fe(IV)-oxo species is postulated to be the active oxidant in the peracid-based catalytic systems. Computational studies on the C<img>H oxidation mechanism reveal that while the hydroxyl radical is mainly responsible for the H-atom abstraction in the H₂O₂-based catalytic system, it is the Fe(IV)-oxo species that abstracts the H-atom from the substrate in the peracid-based catalytic systems, in agreement with the experimental observations.</p></div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 350-356"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.10.010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2595829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}