Total Acid Number Reduction of Naphthenic Acid Using Subcritical Methanol: A Kinetic Study

Document Type: Research Article


1 Centre of Research in Ionic Liquids, Universiti Teknologi Petronas, 32610 Bandar Seri Iskandar, Perak, MALAYSIA

2 Department of Petroleum Engineering, Universiti Teknologi Petronas, 32610 Bandar Seri Iskandar, Perak, MALAYSIA


The aim of this study is to explore the capability of subcritical methanol to reduce the acidity of naphthenic acids and to determine reaction kinetics for large-scale reactor design.The experiments were carried out in a 25 mL autoclave reactor (China) at temperatures of 70-120oC, Methanol Partial Pressures (MPPs) of 0.1-1.5 MPa, and reaction times of 0-60 min. The total acid number content of the samples was analyzed using ASTM D 974 techniques. Experimental results reveal that total acid number reduction of naphthenic acids increased with increasing reaction temperature, MPP, and reaction time. Approximately 74.20% total acid number was reduced at a temperature of 120oC, a MPP of 1 MPa, and a reaction time of 60 min. Experimental data revealed that total acid number removal reaction kinetics followed second-order kinetics with an activation energy of 11.27 kcal/mol. Therefore, subcritical methanol is able to reduce the total acid number of naphthenic acids without the addition of any catalyst.


Main Subjects

[1] Hardacre C., Goodrich P., Anderson K., Processing for Removing Organic Acids From Crude Oil and Crude Oil Distillates, U.S. Pat. No. 20120132564 A1 (2012).

[2] Wang Y.-Z., Zhong D.-L., Duan H.-L., Song C.-M., Han X.-T., Ma X.-R., Removal of Naphthenic Acids From Crude Oils by Catalytic Decomposition Using Mg–Al Hydrotalcite/γ-Al2O3 as a Catalyst, Fuel, 134:499-504 (2014).  DOI:10.1016/J.FUEL.2014.06.026.

[3] Clemente J.S., Fedorak P.M., A Review of the Occurance, Analyses, Toxicity, and Bodegradation of Naphthenic Acids, Chemosphere, 60 (5): 585-600 (2005).

[4] Headley J.V., McMartin D.W., A Review of the Occurrence and Fate of Naphthenic Acids in Aquatic Environments, J. Environ. Sci. Health A, 39(8): 1989-2010 (2004).

DOI: 10.1081/ESE-120039370.

[5] Scott A.C., MacKinnon M.D., Fedork P.M., Naphthenic Acids in Athabasca Oil Sands Tailing Waters are Less Biodegradable than Commercial Naphthenic Acids, Environ. Sci. Technol., 39(21): 8388-8394 (2005).

DOI: 10.1021/es051003k.

[7]  Kane R., Cayard M., A Comprehensive Study on Naphthenic Acid Corrosion, Corrosion 2002, NACE International, Houston, U.S.A., Paper No. 02555, 1-16 (2002).

[8] Shukri N. M., Bakar W. A., Jaafar J., Majid Z.A., Removal of Naphthenic Acids From High Acidity Korean Crude Oil Utilizing Catalytic Deacidification Method, J. Ind. Eng. Chem., 28: 110-110 (2015).        DOI:10.1016/J.JIEC.2015.02.005.

[9]  Wang Y.-Z., Li, J.-Y., Sun X.-Y., Duan H.-L., Song C.-M., Zhang M.-M., Liu Y.-P., Removal of Naphthenic Acids From Crude Oils by Fixed-Bed Catalytic Esterification, Fuel, 116: 723-728 (2014).

[10] Ding L., Rahimi P., Hawkins R., Bhatt S., Shi Y., Naphthenic Acid Removal From Heavy Oils on Alkaline Earth-Metal Oxides and ZnO Catalyst, Appl. Catal. A-Gen., 371(1-2): 121-130 (2009).

[11] Zhang A., Ma Q., Wang K., Tang Y., Goddard W.A., “Improved Processes to Remove Naphthenic Acids, Final Technical Report”, California Institute of Technology, Pasadena, CA, DE-FC26-02NT15383, 1-96 (2005).

[12] Quiroga-Becerra H., Mejia-Miranda C., Laverde-Cataño D., Hernandez-López M., Gomez-Sánchez M., A Kinetic Study of Esterification of Naphthenic Acids From a Colombian Heavy Crude Oil, CT&F- Ciencia, Tecnologia y Futuro, 4(5): 21-32 (2012). ISSN 0122-5383. 

[13] Rudolf M.F., Process for Removing Naphthenic Acids From Hydrocarbon Oils, U.S. Pat. No. 2227811 A (1941).

[14] Oh H.Y., Park J.H., Rhee Y.W., Kim J.N., Decarboxylation of Naphthenic Acid Using Alkaline Earth Metal Oxide, J. Ind. Eng. Chem., 17(4): 788-793 (2011).

[15] Mandal P.C., Wahyudiono, Sasaki M., Goto M., Non-Catalytic Reduction of Total Acid Number (TAN) of Naphthenic Acids (NAs) Using Supercritical Methanol, Fuel Process. Technol., 106: 641-644 (2013).

[16] Kulawska M., Sadlowski J., Skrzypek J., Kinetics of the Esterification of Maleic Anhydride with Octyl, Decyl or Dodecyl Alcohol Over Dowex Catalyst, React. Kinet. Catal. Lett., 85(1): 51-56(2005).

[17] Wang Y., Chu Z., Qiu B., Liu C., Zhang Y., Removal of Naphthenic Acids From a Vacuum Fraction Oil with an Ammonia Solution of Ethylene Glycol, Fuel, 85(17-18): 2489-2493 (2006).

[18] Tesser R., Di Serio M., Guida M., Natasi M., Santhacesaria E., Kinetics of Oleic Acid Esterification with Methanol in the Presence of Triglycerides, Ind. Eng. Chem. Res., 44(21): 7978-7982 (2005).


[19] Mandal P.C., Shiraishi T., Wahyudiono, Sasaki M., Goto M., Kinetics and Reaction Pathways for Heptylbenzene Decomposition in Supercritical Water, J. Chem. Eng. Jpn., 44(7): 486-493 (2011)