{"title":"Is metallic palladium formed in Wacker oxidation of alkenes?","authors":"Milan Hronec, Zuzana Cvengrošová, Štefan Holotík","doi":"10.1016/0304-5102(94)00043-3","DOIUrl":null,"url":null,"abstract":"<div><p>The oxidation of cyclohexene with molecular oxygen catalyzed by solid Pd/C or Pd<sup>II</sup> acetate—hydroquinone—iron phthalocyanine gives cyclohexane, benzene and oxygenated products. Oxygen pressure and solvent used influence significantly the distribution of the products and at the pressure above 2 atm no cyclohexane is formed. Over Pd/C catalyst in the absence of oxygen, disproportionation to cyclohexane and benzene (the ratio is nearly 2:1) proceeds exclusively. Under comparable conditions 2-cyclohexenol is disproportionated to cyclohexanol and phenol and some of it rearranges to cyclohexanone. The explanation for the disproportionation of cyclohexene under the Wacker conditions is that Pd<sup>0</sup> centres intermediately formed after stoichiometric oxidation of cyclohexene by Pd<sup>II</sup> are not completely reoxidized, but depending on the reaction conditions, they can partly aggregate and then, similarly to metallic surfaces, dehydrogenate cyclohexene to benzene. The hydrogen species formed migrate on the palladium surface and hydrogenate cyclohexene or at sufficient oxygen pressure they are oxidized to water.</p></div>","PeriodicalId":16567,"journal":{"name":"分子催化","volume":"91 3","pages":"Pages 343-352"},"PeriodicalIF":0.0000,"publicationDate":"1994-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/0304-5102(94)00043-3","citationCount":"6","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"分子催化","FirstCategoryId":"1089","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/0304510294000433","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"Chemical Engineering","Score":null,"Total":0}
引用次数: 6
Abstract
The oxidation of cyclohexene with molecular oxygen catalyzed by solid Pd/C or PdII acetate—hydroquinone—iron phthalocyanine gives cyclohexane, benzene and oxygenated products. Oxygen pressure and solvent used influence significantly the distribution of the products and at the pressure above 2 atm no cyclohexane is formed. Over Pd/C catalyst in the absence of oxygen, disproportionation to cyclohexane and benzene (the ratio is nearly 2:1) proceeds exclusively. Under comparable conditions 2-cyclohexenol is disproportionated to cyclohexanol and phenol and some of it rearranges to cyclohexanone. The explanation for the disproportionation of cyclohexene under the Wacker conditions is that Pd0 centres intermediately formed after stoichiometric oxidation of cyclohexene by PdII are not completely reoxidized, but depending on the reaction conditions, they can partly aggregate and then, similarly to metallic surfaces, dehydrogenate cyclohexene to benzene. The hydrogen species formed migrate on the palladium surface and hydrogenate cyclohexene or at sufficient oxygen pressure they are oxidized to water.
期刊介绍：
Journal of Molecular Catalysis (China) is a bimonthly journal, founded in 1987. It is a bimonthly journal, founded in 1987, sponsored by Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, under the supervision of Chinese Academy of Sciences, and published by Science Publishing House, which is a scholarly journal openly circulated both at home and abroad. The journal mainly reports the latest progress and research results on molecular catalysis. It contains academic papers, research briefs, research reports and progress reviews. The content focuses on coordination catalysis, enzyme catalysis, light-ribbed catalysis, stereochemistry in catalysis, catalytic reaction mechanism and kinetics, the study of catalyst surface states and the application of quantum chemistry in catalysis. We also provide contributions on the activation, deactivation and regeneration of homogeneous catalysts, solidified homogeneous catalysts and solidified enzyme catalysts in industrial catalytic processes, as well as on the optimisation and characterisation of catalysts for new catalytic processes.
The main target readers are scientists and postgraduates working in catalysis in research institutes, industrial and mining enterprises, as well as teachers and students of chemistry and chemical engineering departments in colleges and universities. Contributions from related professionals are welcome.
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