Novel periodic mesoporous organosilicas containing pyromellitimides and their application for the photodegradation of asphaltenes

Abstract

Periodic mesoporous organosilicas containing pyromellitic diimide units embedded in the pore walls (PMOPMI) were synthesized by co-condensation of the bridged silsesquioxane precursor N,N′-bis(3-triethoxysilylpropyl)pyromellitimide with tetraethoxysilane (TEOS) in acidic conditions, in the presence of the structure-directing agent Pluronics P-123. PMOPMI were also synthesized from the corresponding amic acid precursors. The PMOPMI were studied by different techniques, including N2 adsorption isotherms, transmission electron microscopy, infrared and diffuse reflectance spectroscopy and contact angles. The studied samples displayed well-organized 2D-hexagonal structures. The PMOPMI were able to adsorb petroleum asphaltenes from toluene solutions, and were efficient photosensitizers for the photodegradation of the adsorbed asphaltenes when irradiated. Most of the asphaltenes were removed from solutions by the combined action of adsorption and photodegradation processes.