Characterization of Asphaltenes in Solution and Inside the Pores of Catalysts by 1H NMR Relaxometry

The upgrading of heavy petroleum fractions needs the development of more and more efficient heterogeneous catalysts. One of the major issues of these processes is the diffusion of asphaltenes to the active site through the porous network of the alumina support. The catalytic efficiency is deeply impacted by the transport phenomena and the interfacial interactions. The aim of this work is to capture the extent to which low-field two-dimensional (2D) 1H NMR relaxation time correlations can contribute to a better understanding of the dynamics of asphaltene in solution and within the pores of catalyst supports. Two-dimensional T1–T2 maps for asphaltenes in solution in toluene exhibit several T1–T2 contributions, varying with the asphaltene concentration and the size of the asphaltenic fractions obtained by ultrafiltration separation. According to the nanoaggregate structure proposed by the Yen–Mullins aggregation model of asphaltenes, it was possible to unravel the different asphaltenic proton relaxation beha...