Journal of Molecular Catalysis A: Chemical最新文献_第8页

Efficient functionalization of olefins by arylsilanes catalyzed by palladium anionic complexes 钯阴离子配合物催化芳基硅烷高效功能化烯烃

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.07.023

E. Silarska , M. Majchrzak , B. Marciniec , A.M. Trzeciak

引用次数: 6

DRIFTS study of CO adsorption on Pt nanoparticles supported by DFT calculations DFT计算支持下CO在Pt纳米颗粒上吸附的DRIFTS研究

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.10.002

Claudia Lentz, Sara Panahian Jand, Julia Melke, Christina Roth, Payam Kaghazchi

{"title":"DRIFTS study of CO adsorption on Pt nanoparticles supported by DFT calculations","authors":"Claudia Lentz, Sara Panahian Jand, Julia Melke, Christina Roth, Payam Kaghazchi","doi":"10.1016/j.molcata.2016.10.002","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.10.002","url":null,"abstract":"<div>Extensive research has been devoted to the assignment of IR bands of CO adsorbed on Pt nanoparticles, which are widely used in heterogeneous and electrocatalysis (e.g. fuel cells). In contrast to single crystal studies, the assignment of CO adsorption to the nanoparticle structure is still controversial. Here we present a case study where we assign CO adsorption bands to the structure of Platinum nanoparticles with a given size distribution. Using a special diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) cell allows to achieve high quality data under in-situ conditions. Temperature dependent CO adsorption spectra are resolved into three bands which depend on the applied flow and pretreatment conditions. Our calculations using Density Functional Theory (DFT) can mimic the experimental findings and link these bands to the particle structure. By explicitly calculating the IR spectra of CO/Pt nanoparticles of different sizes we show that the IR bands are due to a combined size and site effect. For fully covered small nanoparticles the IR bands are attributed to all binding sites. For larger nanoparticles the dominant contribution is related to {111} facets but the other bands are still site independent. Here we provide a tool to assign CO adsorption bands on Platinum nanoparticles with a given size distribution. This can be related to the structure–acitvity relationship which is required for a tailored catalyst design.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 1-9"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.10.002","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2878502","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}

引用次数: 51

Catalytic etherification of alcohols in Shilov system: CO versus CH bond activation 希洛夫体系中醇的催化醚化反应:CO与CH键活化

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.07.012

Oleg V. Khazipov , Denys V. Nykytenko , Tatyana V. Krasnyakova , Alexander N. Vdovichenko , Dario A. Fuentes Frias , Serge A. Mitchenko

{"title":"Catalytic etherification of alcohols in Shilov system: CO versus CH bond activation","authors":"Oleg V. Khazipov , Denys V. Nykytenko , Tatyana V. Krasnyakova , Alexander N. Vdovichenko , Dario A. Fuentes Frias , Serge A. Mitchenko","doi":"10.1016/j.molcata.2016.07.012","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.07.012","url":null,"abstract":"<div>A novel catalytic reaction of alcohol etherification in the system ROH − PtCl42− ‐ PtCl62− was found. Methanol easily transforms into dimethyl ether in the presence of catalytic amounts of PtII chloro complexes at 70°C. Under the same conditions reaction of ethanol affords diethyl ether (catalytic) and π-ethylene PtII complex (stoichiometric). The reactions are accompanied by multiple H/D exchange, which is indicative of intermediacy of corresponding alkyl platinum derivatives. The plausible reaction mechanism involves oxidative addition of alcohol forming intermediate alkyl platinum(IV) derivative followed by decomposition of it via reductive elimination step under the action of alcohol giving the ether and regenerating catalyst. In the case of ethyl alcohol reaction, β-hydrogen abstraction from the intermediate Pt-ethyl species yields π-ethylene platinum(II) complex. Although it seems that the reaction does not involve the initial breaking of C<img>H bonds of an alcohol, this system can be regarded as a model for studying of some peculiarities of Shilov chemistry, in particular, of isotope scrambling mechanisms in Shilov alkane activation.In contrast to reactions of dimethyl and diethyl ethers formation, tert-butyl ethers formation in CD3OH/t-BuOH medium is catalyzed by PtIV chloro complexes also and is not accompanied by isotope scrambling. These observations argue against intermediacy of alkyl platinum derivatives suggesting that acid-catalyzed mechanism operates in tert-butyl alcohol etherification.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 490-498"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.07.012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2879564","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}

引用次数: 2

DFT modeling of the post-titanocene catalytic system LTiCl2-Bu2Mg-Et2AlCl for alkene polymerization: The role of alkyl bridge Mg–C–Ti and β-agostic C–H–Ti bonds in the formation of active centers 烯烃聚合后二茂钛催化体系LTiCl2-Bu2Mg-Et2AlCl的DFT建模:烷基桥Mg-C-Ti和β-agostic C-H-Ti键在活性中心形成中的作用

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.09.027

Leila Y. Ustynyuk

{"title":"DFT modeling of the post-titanocene catalytic system LTiCl2-Bu2Mg-Et2AlCl for alkene polymerization: The role of alkyl bridge Mg–C–Ti and β-agostic C–H–Ti bonds in the formation of active centers","authors":"Leila Y. Ustynyuk","doi":"10.1016/j.molcata.2016.09.027","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.09.027","url":null,"abstract":"<div>DFT modeling of the active centers formation in the catalytic system LTiCl2-Bu2Mg-Et2AlCl for alkene polymerization, where L is a bidentate ligand of saligenin type, suggests the three-step mechanism of this process. This mechanism includes the addition of the most probable alkylating agent, RMg(μ-Cl)2AlR2 or RMg(μ-Cl)2MgR (R=alkyl), to LTiCl2 with the formation of the trinuclear heterocomplex with the alkyl bridge bond Mg–C–Ti, followed by its two-step isomerization into the active center via the β-agostic intermediate. The free energy changes at the stages of the addition and isomerization are negative; the maximal energy barrier on the reaction pathway is small. In the Mg-free system LTiCl2-AlR3, the isomerization proceeds through the single energy barrier with a significantly higher amplitude. This could be the reason for a relatively high activity of the Mg-containing system and inactivity of the Mg-free system.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 600-609"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.09.027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2879566","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}

引用次数: 5

Functionalization of the naturally occurring linalool and nerol by the palladium catalyzed oxidation of their trisubstituted olefinic bonds 钯催化氧化天然芳樟醇和橙醇三取代烯烃键的功能化

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.07.033

Luciana A. Parreira , Ana F. Azevedo , Luciano Menini , Elena V. Gusevskaya

{"title":"Functionalization of the naturally occurring linalool and nerol by the palladium catalyzed oxidation of their trisubstituted olefinic bonds","authors":"Luciana A. Parreira , Ana F. Azevedo , Luciano Menini , Elena V. Gusevskaya","doi":"10.1016/j.molcata.2016.07.033","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.07.033","url":null,"abstract":"<div>Linalool and nerol, bio-renewable terpenic alkenyl alcohols found in many essential oils, were selectively oxidized by molecular oxygen in the presence of the chloride-free Pd(OAc)2/p-benzoquinone catalytic system. An efficient dioxygen-coupled catalytic turnover was achieved in the absence of auxiliary electron-transfer mediators under 5–10atm of oxygen pressure. In both substrates, only one of two olefinic bonds was involved in the interaction with palladium, whereas the other one remained intact. Primary allylic acetates were formed as major reaction products: 8-linalyl acetate and 8-neryl acetate from linalool and nerol, respectively. In the case of linalool, the intramolecular cyclization product (known as herboxide), also resulted from the oxidation of the internal double bond, was also formed in significant amounts. All monoterpenic compounds obtained in the present work are natural products found in exotic plants or grape wines and are potentially useful as fragrance ingredients due to their pleasant scents.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 429-434"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.07.033","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2171629","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}

引用次数: 11

Cobalt and cobalt-iron spinel oxides as bulk and silica supported catalysts in the ethanol combustion reaction 钴和钴铁尖晶石氧化物作为乙醇燃烧反应的体积和二氧化硅负载催化剂

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.11.005

Yasmina Hammiche-Bellal , Nabila Zouaoui-Mahzoul , Ibtissem Lounas , Amel Benadda , Rafik Benrabaa , Aline Auroux , Laaldja Meddour-Boukhobza , Amar Djadoun

{"title":"Cobalt and cobalt-iron spinel oxides as bulk and silica supported catalysts in the ethanol combustion reaction","authors":"Yasmina Hammiche-Bellal , Nabila Zouaoui-Mahzoul , Ibtissem Lounas , Amel Benadda , Rafik Benrabaa , Aline Auroux , Laaldja Meddour-Boukhobza , Amar Djadoun","doi":"10.1016/j.molcata.2016.11.005","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.11.005","url":null,"abstract":"<div>Cobalt and mixed iron-cobalt spinel oxides CoxFe(3-x)O4 supported on SiO2 ‘IMP-Cox-500′ and their bulk analogues ‘CP-Cox-500′ were prepared via impregnation and co-precipitation methods respectively and calcined at 500°C. Thermogravimetric analysis ‘ATG/DTG’, X-ray Diffraction method ‘XRD’, Texture measurements ‘BET/BJH’ and Temperature Programmed Reduction technique ‘TPR’ were used for their characterization. Their catalytic behavior in ethanol combustion was investigated. Results showed that nanostructured oxide materials with spinel structure were obtained with a good dispersion of the active phase at the surface of silica in the case of IMP-Cox-500 compounds. The reduction behavior of the prepared samples is highly dependent on the oxide composition and interaction with the support; which is directly related to the catalytic behavior. The use of supported catalysts improves the catalytic performance and leads the reaction towards a total oxidation by decreasing greatly the formation of partial oxidation products. The obtained values of activation energies are relatively low in comparison with the literature data. A compensation effect was found by carrying out ethanol combustion through the spinel systems considered in this work.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 97-106"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.11.005","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2171631","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}

引用次数: 15

Clean synthesis of alkyl levulinates from levulinic acid over one pot synthesized WO3-SBA-16 catalyst 用一锅合成WO3-SBA-16催化剂催化乙酰丙酸清洁合成乙酰丙酸烷基酯

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.10.032

Siva Sankar Enumula, Venkata Ramesh Babu Gurram, Raji Reddy Chada, David Raju Burri, Seetha Rama Rao Kamaraju

{"title":"Clean synthesis of alkyl levulinates from levulinic acid over one pot synthesized WO3-SBA-16 catalyst","authors":"Siva Sankar Enumula, Venkata Ramesh Babu Gurram, Raji Reddy Chada, David Raju Burri, Seetha Rama Rao Kamaraju","doi":"10.1016/j.molcata.2016.10.032","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.10.032","url":null,"abstract":"<div>The present work highlights the application of solid acid catalyst to produce alkyl levulinate from levulinic acid in continuous mode under vapor phase conditions. In this context, tungsten oxide incorporated SBA-16 catalysts were prepared by one pot direct synthesis method and evaluated for the titled reaction. Under optimized reaction conditions, 3 wt% WO3-SBA-16 catalyst delivered complete conversion of levulinic acid with 95% selectivity towards ethyl levulinate. The synthesized catalysts were characterized to know the physico-chemical features by various techniques, namely, X-ray diffraction, N2 physisorption, temperature programmed reduction of hydrogen (H2-TPR), temperature programmed desorption of ammonia (NH3-TPD), DR-UV–vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The characterization results suggest that, the superior catalytic activity can be ascribed due to the enhanced acidity of SBA-16 obtained through incorporation of tungsten oxide and easy of accessibility for the dispersed active sites through uniform pore channels. The constant catalytic activity in 10h time on study shows the sturdiness of the catalyst and the spent catalyst can be regenerated several times. Moreover, various alkyl levulinates (methyl, n-propyl, and n-butyl) were synthesized with more than 90% selectivity over this catalyst.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 30-38"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.10.032","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2171634","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}

引用次数: 65

Synergism studies on alumina-supported copper-nickel catalysts towards furfural and 5-hydroxymethylfurfural hydrogenation 铝负载铜镍催化剂对糠醛和5-羟甲基糠醛加氢的协同作用研究

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.11.023

Sanjay Srivastava, G.C. Jadeja, Jigisha Parikh

{"title":"Synergism studies on alumina-supported copper-nickel catalysts towards furfural and 5-hydroxymethylfurfural hydrogenation","authors":"Sanjay Srivastava, G.C. Jadeja, Jigisha Parikh","doi":"10.1016/j.molcata.2016.11.023","DOIUrl":"https://doi.org/10.1016/j.molcata.2016.11.023","url":null,"abstract":"<div>The structure of alumina-supported copper-nickel catalysts prepared by impregnation method was studied by using a combination of various characterization techniques including XRD, N2-sorption, TEM, H2-TPR, NH3-TPD, XANES/EXAFS and CHNS methods. A series of characterizations revealed that dispersion of copper increases with an increase in nickel loading on ɣ-Al2O3 due to strong interaction between nickel and copper oxide particles. This also led to the formation of mixed copper-nickel oxides in calcined catalysts at the highest loading of nickel and copper (i.e. Cu/Ni=1). In catalytic activity, both the monometallic Cu/ɣ-Al2O3 and Ni/ɣ-Al2O3 showed lower activity and selectivity towards hydrogenation of both Furfural and 5-Hydroxymethylfurfural to 2-methylfuran (2-MF) and 2, 5-dimethylfuran (DMF), respectively. However, with increase in nickel loading, the activity and the selectivity of Cu/ɣ-Al2O3 drastically increased for both the cases and Cu-Ni/ɣ-Al2O3 (Cu/Ni=1) showed the highest catalytic activity. Furthermore, combination of Cu/Ni ratios and temperature plays a significant role in the product distribution, as in the case of furfural hydrogenation, at a lower temperature, furfuryl alcohol (FOL) appears as the main product while at a higher temperature, 2-methylfuran (2-MF) is found to be the dominant product over Cu-Ni/ɣ-Al2O3 (Cu/Ni=1) catalysts. Similarly, 2,5-bishydroxymethylfuran (BHF) is found to be the major product at a lower temperature and 2,5-dimethylfuran (DMF) is selectively produced at a higher temperature in the HMF hydrogenation. Furthermore, reaction pathways are discussed for both the reactions.</div>","PeriodicalId":370,"journal":{"name":"Journal of Molecular Catalysis A: Chemical","volume":"426 ","pages":"Pages 244-256"},"PeriodicalIF":5.062,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.molcata.2016.11.023","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"2391734","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}

引用次数: 109

Synthesis, characterization and catalytic application of a novel polyethylene-supported Fe/ionic liquid complex 新型聚乙烯负载铁离子液体配合物的合成、表征及催化应用

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.11.015

Davar Elhamifar , Dawood Elhamifar , Frood Shojaeipoor

引用次数: 21

NNN-pincer-copper complex immobilized on magnetic nanoparticles as a powerful hybrid catalyst for aerobic oxidative coupling and cycloaddition reactions in water 磁性纳米颗粒固定化nnn -钳子-铜配合物作为水中有氧氧化偶联和环加成反应的强大杂化催化剂

IF 5.062

Journal of Molecular Catalysis A: Chemical Pub Date : 2017-01-01 DOI: 10.1016/j.molcata.2016.11.007

Nasrin Zohreh, Mahboobeh Jahani

引用次数: 19