A novel method for the separation of high-molecular-weight saturates from paraffinic petroleum based samples

The precise chromatographic isolation of saturates is a common problem of the characterization of highly paraffinic petroleum based samples. Incomplete elution of high-molecular-weight saturates (HMWS) or contamination of saturates by aromatics can occur when alumina or silica gel are used to separate highly paraffinic samples. Here, we present a precise, fast and simple method for the quantitative isolation of HMWS from samples of highly paraffinic crude oils, crude oil deposits, high-boiling petroleum distillates, distillation residues and waxes. The method is based on a direct chromatographic elution of HMWS with n-heptane at 80 degrees C on a column packed with silica gel modified with silver nitrate. The pre-separation of asphaltenes from samples is not necessary. This allowed for a quantitative elution of all present HMWS (up to C-100) with no contamination by aromatics. As an example of a practical application to benefit from this efficient hydrocarbon fractionation procedure, is the analysis of crude oils and deposits. A detailed knowledge of the content of high-molecular-weight n-alkanes in these samples can help to prevent problems during crude oil transport and storage. (C) 2018 Elsevier Ltd. All rights reserved.