Preparation of wrapped carbon nanotubes poly(4-vinylpyridine)/MTO based heterogeneous catalysts for the oxidative desulfurization (ODS) of model and synthetic diesel fuel

Abstract

The preparation of novel wrapped carbon nanotubes poly(4-vinylpyridine)/methyl trioxorhenium based heterogeneous catalysts has been reported by two different procedures: a) the wrapping by grinding of multiwall carbon nanotubes with pre-formed adducts, respectively, [poly(4-vinylpyridine)·methyltrioxorhenium] or [poly(4-vinylpyridine)-N-oxide·methyltrioxorhenium] and, b) the loading of methyltrioxorhenium on previously wrapped multiwall carbon nanotubes with poly(4-vinylpyridine) and poly(4-vinylpyridine)-N-oxide resins. The novel catalysts were characterized by SEM, TEM, ICP-MS and XPS analyses. Both types of catalysts were efficient systems in the oxidation of recalcitrant aromatic sulfur derivatives with H2O2, as representative models of oxidative desulfurization processes, affording the corresponding sulfones with yields ranging from moderate to quantitative. The oxidation of a complex model fuel oil and of synthetic diesel fuel, under optimal experimental conditions, is also reported. The performance of novel catalysts was dependent on the specific procedure applied for the immobilization of the active species, and was more efficient for both model oil and synthetic diesel fuel samples (with quantitative conversions and selectivities to the corresponding sulfones), than for isolated substrates.