The Influence of Naphthenic Acid and Sulfur Compound Structure on Global Crude Corrosivity under Vacuum Distillation Conditions

摘要

At temperatures between 220 and 400°C, naphthenic acid and sulfur-containing species present in many global crudes are known to cause refinery corrosion. Naphthenic acids are organic acids often described as cycloalkane ring(s) with an attached aliphatic chain having a terminal carboxylic acid group. Elemental sulfur, mercaptan, sulfide and polysulfide species convert to hydrogen sulfide which attacks metal. However, neither total acid contents measured by total acid number (TAN) nor total sulfur contents measured by elemental analyses have been found to correlate well with corrosivity. A fundamental study of the relationships of molecular structures of organic acid and sulfur compounds to corrosivity has been performed in a test unit that simulates corrosion found under vacuum distillation conditions. The corrosivities of model oil mixtures consisting of specific organic acid compounds in the presence or absence of specific sulfur compounds in white oil were measured. The corrosivities of global crudes including Athabasca are discussed in terms of their contents of different types of organic acid and sulfur species. In particular, analyses of coupon surfaces and crude oil organic acid subspecies identify the most corrosive species. This work was partially supported by the Canadian Association of Petroleum Producers and Alberta Innovates - Energy and Environment Solutions (formerly Alberta Energy Research Institute).