Total Acid Number Reduction of 2, 6-Naphthalenedicarboxylic Acid Using Subcritical Methanol for Reducing Acidity of Heavy Oil: A Kinetic Study

Abstract

Naphthenic acid (NA) found in hydrocarbon deposits is responsible for acidity of petroleum oils. In this study, a model compound of NAs, 2, 6-Naphthalenedicarboxylic acid (NDCA), is used for total acid number (TAN) reduction kinetic analysis. This goal of this paper is to investigate the capability of subcritical methanol (SubC-MeOH) for reducing acidity of NDCA without the addition of any catalyst or additives. The reaction kinetics is also discovered for large scale reactor design. The experiments were carried out in a 25 ml autoclave reactor (China) at temperatures of 180-220oC, a methanol partial pressure (MPP) of 0.1 MPa, reaction times of 0-60 min and a NDCA initial gas phase concentration of 0.03 g/mL. The TAN content of the samples were analyzed using American Society for Testing Materials (ASTM) D 974 techniques. The reaction products were identified and quantified with the help of GC/MS and GC-FID respectively. Experimental results reveal that TAN reduction of NDCA was increasing with increasing reaction temperature and time. Approximately, 52.12% TAN was reduced at a temperature of 220oC, a MPP of 0.1 MPa, and a reaction time of 60 min. Experimental data revealed that TAN removal reaction kinetics followed second order kinetics with an activation energy of 8.24 kcal/mol and a pre-exponential factor of 2.087 fraction-1s-1. Therefore, SubC-MeOH is capable to reduce TAN of NDCA without the addition of any catalyst or additives.