Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results.

Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO3(2-) or NO3(-)). The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

Catalysts for heterogeneous oxidation reaction based on metalloporphyrins immobilized on kaolinite modified with triethanolamine.

Raw kaolinite was modified with triethanolamine (TEA), in an attempt to create a new support for the immobilization of metalloporphyrins. Anionic metalloporphyrins containing Fe(3+) or Mn(3+) as metallic centers were immobilized on the prepared support, and the obtained solids were characterized by Fourier-transform infrared (FTIR) spectroscopy, X-ray powder diffraction (XRPD), thermal analysis (thermogravimetric and differential thermal analyses--TGA/DTA), and scanning electron microscopy (SEM). The solids were used in heterogeneous oxidation catalysis of cyclooctene and cyclohexane. The yields from the oxidation of cyclooctene depended on the amount of TEA and/or water present in the solids. Good reaction yields were obtained for the oxidation of cyclohexane, with selectivity for the alcohol. In one specific case, a possible co-catalytic activity was verified for TEA during the oxidation of cyclohexane.