Naphthenic acid (NA) present in crude oil leads to corrosion problems within oil refineries. The objective of this study is to reduce total acid number (TAN) from NA using a catalyst-free supercritical methanol (SC-MeOH), a process novel in this area. The reaction was carried out in an 8.8 mL batch reactor fabricated from Hastelloy C-276 with respective design temperature and pressure of 500 degrees C and 50 MPa. The ability of SC-MeOH to reduce TAN was explored at temperatures from 300 to 350 degrees C and methanol partial pressure (MPP) of 10 MPa. Experimental results revealed that TAN removal was 99.77% at a temperature of 350 degrees C, MPP of 10 MPa and reaction time of 60 min. The TAN removal followed first order kinetics, with Arrhenius parameters of activation energy 5.78 kcal/mol and a pre-exponential factor 1.56 s(-1). These results suggest that SC-MeOH is capable of reducing TAN from NA with no use of catalyst or additives. (C) 2012 Published by Elsevier B.V.