Refinery Corrosion, Organic Acid Structure, and Athabasca Bitumen

Since 1920, certain crude oils have been found to be corrosive in refineries.  At temperatures between 220 and 400°C, sulphur-containing and organic acid species are known to be involved.  Elemental sulphur, mercaptan, sulfide and polysulphide species convert to hydrogen sulphide which attacks metal. Organic acids and particularly naphthenic acids consisting of cycloalkane ring(s) with an attached aliphatic chain having a terminal carboxylic acid group, have been implicated.  However, neither total sulphur contents measured by elemental analyses nor total acid contents measured by total acid number (TAN) have been found to correlate well with corrosivity.

A fundamental study of the relationships of molecular structures of sulphur and organic acid compounds to refinery corrosivity is being performed.  To understand acid species, the corrosivity of homologous series of organic acids with respect to temperature and vacuum are being assessed in a test unit that simulates corrosion found in vacuum distillation towers. The organic acids from globally-sourced heavy crude oils and bitumen including Athabasca bitumen are being isolated and characterized.  Petroleum corrosivity will be discussed in terms of their contents of different types of organic acids.  This work is partially supported by the Canadian Association of Petroleum Producers and Alberta Energy Research Institute.