Journal of Molecular Catalysis A: Chemical 217 (2004) 121–131 Anionic iron(III) porphyrin immobilized on silanized kaolinite as catalyst for oxidation reactions Shirley Nakagaki ∗ , Flávio Luiz Benedito, Fernando Wypych Bioinorganic Laboratory, Departamento de Qu´ ımica, Universidade Federal do Paraná, C.P. 19081, CEP 81531-990 Curitiba, PR, Brazil Received 12 September 2003; received in revised form 1 March 2004; accepted 3 March 2004 Available online 17 April 2004 Abstract Kaolinite (KGa-2, standard poorly crystallized) was reacted with 3-aminopropyltriethoxysilane (3-APTS) (silanization reaction) after inter- calation with urea and delamination under ultrasonic treatment. The silane groups were grafted partially on the layered kaolinite outer surface and aqueous treatment could hydrolyze the remaining ethoxy groups. The silanized kaolinite (compound 4) was used as a new inorganic sup- port for immobilization of the anionic iron(III) porphyrin: 5,10,15,20-tetrakis(2,6-difluoro-3-sulfonatophenyl) porphyrinato iron(III) chloride [(FeTDFSPP)Cl] 4- (compound 3). It was found that compound 4 was an appropriated structure to immobilize the [(FeTDFSPP)Cl] 4- by electrostatic interactions. The obtained material (kaolinite-iron(III) porphyrin, compound 5) was characterized by different techniques such as UV-Vis and infrared (FTIR) spectroscopy, electron paramagnetic resonance (EPR), proton nuclear magnetic resonance ( 1 H NMR), atomic absorption spectrometry (AAS) and thermal analysis (simultaneous TG/DSC). Compound 5 was investigated in brand oxidation reactions using cyclooctene, heptane and cyclohexane. Iodosylbenzene (PhIO) was used as oxygen atom donor in different molar ratios of iron(III) porphyrin:PhIO. It was observed that compound 5 was an efficient and highly selective catalyst system for epoxidation of cyclooctene (97% of cyclooctene oxide) and hydroxylation of cyclohexane (90% cyclohexanol) after 1h. The heptane hydroxylation gave 50% of heptanols. The hydrogen peroxide was also used as oxidant but moderate results were obtained. After reuse (3–5 times) the catalyst showed a higher conversion than the primary reactions. © 2004 Elsevier B.V. All rights reserved. Keywords: Porphyrin; Kaolinite; Silanization; Catalysis; Oxidation 1. Introduction Metalloporphyrins are known to perform alkane hydroxy- lation and alkene epoxidation in a biomimetic catalytic way. In order to recover the catalyst from the reaction media for future reuse or recycling, heterogenization methods of the catalyst have been intensively investigated [1-7]. Main aim of these studies has been to obtain a solid compound that can stabilize the metalloporphyrin for reuse in the reactions and at the same time, promote the catalytic reaction in a selective and desirable stereo-specific manner. To achieve this, many different inorganic materials such as silica, zeolite, alumina, glasses, natural and synthetic layered material (clays and layered double hydroxides) have been used [8-12]. Kaolinite, Al 2 Si 2 O 5 (OH) 4 is a dioctahedral layered hy- drated aluminosilicate of the 1:1 type with two distinct in- ∗ Corresponding author. Tel.: +55-11-3665915; fax: +55-11-3665915. E-mail address: shirley@quimica.ufpr.br (S. Nakagaki). terlayer surfaces. One side of the layer is gibbsite-like with aluminum atoms coordinated octahedrally to corner oxygen atoms and hydroxyl groups. The other side of the layer is constituted by a silica-like structure, where the silicon atoms are coordinated tetrahedrally to oxygen atoms. The adja- cent layers are linked by hydrogen bonds involving aluminol (Al–OH) and siloxane (Si–O) groups. These binding forces hinder the intercalation processes, but the hydroxyl groups on the aluminum side of the layer are passive to solvation and covalent grafting reactions [13,14]. In the case of large molecules, it is expected that only the surface would be grafted. In this sense, a delamination process would be help- ful to provide a small number of stacked layers producing crystals with a large basal surface area [15]. Mechanochem- ical intercalation of urea and treatment with water under ultrasound stirring is a very easy way to promote the de- lamination of kaolinite and produce high surface basal area crystals, ideal for the grafting reaction and subsequent im- mobilization of anionic porphyrins. 1381-1169/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2004.03.004