Non-catalytic thermal decomposition of naphthenic acids of petroleum crudes

Abstract

The thermal decomposition of naphthenic acids was carried out in a 50 mL glass vessel equipped with a bottom sparger (for bubbling a gas: H2, N2, steam) and a removable head cap for charging the oil and also containing the gas outlet connections. Gas at a suitable flowrate (1.5–4.5 mL min−1) was used for stripping the decomposition products formed at different heating temperatures (360, 380, 400 °C). Results show that the thermal decomposition of naphthenic acids follows a second order kinetic model. Three carrier gases were tested, nitrogen, hydrogen and steam. The gases stripped the fluid phase from the produced dioxide carbon. Best results were obtained when using nitrogen as stripping gas, at 400 °C and 1.5 L h−1 stripping rate. A 90% decrease of acidity was achieved with a treatment of 4 h. This final TAN value is considered acceptable for a subsequent refining of the crude in a common refinery. Graphical abstract: Naphthenic acid present in crude oil leads to corrosion problems within oil refineries. The objective of this study was to reduce the total acid number through non-catalytic thermal decarboxylation of the naphthenic acids using a gas–liquid reactor and different carrier gases. The results indicate an acidity reduction without significant changes to its physical properties. [Figure not available: see fulltext.]