Efficient Sc triflate mesoporous-based catalysts for the synthesis of 4,4′-methylenedianiline from aniline and 4-aminobenzylalcohol

Sc triflate mesoporous-based catalysts have been prepared using a two-step strategy (i.e., Atrane method) based on the formation of the hierarchic bimodal porosity in the first step and the formation of Sc triflate complexes at the materials surface in the second step. All solids were analyzed by EPMA, surface area, and pore size values, XRD, TEM, FTIR, and 45Sc NMR static spectra. The catalysts have been investigated in the synthesis of 4,4′-methylenedianiline (4,4′-MDA) from aniline and 4-aminobenzylalcohol. 4,4′-MDA was obtained with selectivities over 85.0% for a conversion of aniline of 31%, at 80 °C and after 24 h. Using microwaves, selectivities of 90% in 4,4′-MDA were reached in only 3 h. Important key parameters influencing the catalytic performances seem to be the scandium content and the nature of the formed Sc species. By replacing formaldehyde with 4-aminobenzylalcohol, the necessity of additional steps for neutralization and separation of the wastes can be eliminated.

Graphical abstractIsolated scandium triflate species incorporated in a UVM-7 porous bimodal support were prepared using a two-step strategy. These catalysts showed a high selectivity in the synthesis of 4, 40-methylenedianiline from aniline and 4-aminobenzylalcohol under mild conditions.Figure optionsDownload full-size imageDownload high-quality image (48 K)Download as PowerPoint slideHighlights► 4,4′-Methylenedianiline is a key intermediate for the production of polyurethanes with an annual production higher than two million metric tonnes. ► Its industrial production is still performed by reacting formaldehyde with stoichiometric amounts of HCl and aniline. ► The methodology requires additional steps for neutralization and separation and produce large amount of residual salt water. ► Replacing formaldehyde with 4-aminobenzylalcohol, the synthesis of 4,4′-MDA in heterogeneous catalysis may be substantially improved in terms of simplicity. ► The novel mesoporous ScOTf-UVM-7 materials, prepared using a two stage procedure, have been found to be effective catalysts for this synthesis.