Selective liquid phase oxidation of o-xylene with gaseous oxygen by transition metal containing polysiloxane initiator/catalyst systems

• Published in: Journal of catalysis Vol. 283; no. 1; pp. 25 - 33
• Main Authors: Förster, Tobias, Schunk, Stephan A., Jentys, Andreas, Lercher, Johannes A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 06.10.2011; Elsevier; Elsevier BV
• Subjects: adsorption; alcohols; Catalysis; catalysts; catalytic activity; Chemistry; Co 2+ and Mn 3+ containing polysiloxane; cobalt; Colloidal state and disperse state; desorption; Exact sciences and technology; Gases; General and physical chemistry; hydrophobicity; Liquid phase oxidation; Liquids; manganese; Metals; o-Xylene; Oxidation; Oxygen; Phase transitions; Porous materials; siloxanes; Surface physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; xylene; Co 2+ and Mn 3+ containing polysiloxane; o-Xylene; Liquid phase oxidation; Water; Alcohol; Hydroperoxide; Decomposition; Selectivity; Hydrophobicity; Liquid phase; Co; Porous material; Solid; Oxidation; Oxygen; Catalytic reaction; Reaction product; and Mn; containing polysiloxane; Desorption; Transition metal; Heterogeneous catalysis; Adsorption; Benzenic compound; Catalyst activity; Catalyst
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2011.06.019

New solid initiator/catalyst systems (Co 2+ and Mn 3+ cation modified hydrophobic polysiloxanes) for the selective liquid phase oxidation are introduced, which show a high stability under reaction conditions and a higher activity than the Co naphthenate benchmark system. [Display omitted] ► A new solid catalyst is described for the liquid phase oxidation of o-xylene. ► Co 2+ and Mn 3+ cations act as initiators/catalysts for radical formation/decomposition. ► Heterogeneous polysiloxane materials showed a higher activity than Co naphthenate. The selective liquid phase oxidation of o-xylene over hydrophobic porous Co 2+ and Mn 3+ containing polysiloxane catalysts showed that both catalysts had higher activity than the homogeneous benchmark system Co naphthenate. The solid catalyst/initiator systems accelerate the radical initiation and the hydroperoxide decomposition. 2-Methylbenzyl hydroperoxide plays a key role in the reaction network as it is the first observed intermediate and is efficiently decomposed by the catalysts. The selectivity of the hydroperoxide decomposition can be controlled to some extent by the choice of transition metal. Co 2+ enhances the formation of o-tolualdehyde, while Mn 3+ increases the tendency to 2-methylbenzyl alcohol formation. The hydrophobic character, demonstrated by the weak adsorption of water, retards the interaction with the polar reaction products and allows their fast desorption, which in turn is a major cause for the high catalytic activity.