We investigated the reactions of saturated (palmitic and stearic acids) and unsaturated fatty acids (oleic and linoleic acids) in supercritical water at 400 degrees C, 240 bar, over zeolites Y, beta, and ZSM-5. The highest total yield of liquid and gaseous products, 97 +/- 2 wt%, was obtained from palmitic acid by applying ZSM-5 with a silica/alumina ratio of 23. The liquid products had a high concentration of single-ring aromatics, and the total molar yield of aromatics was 102% (42 wt% yield). This catalyst could be regenerated and reused. ZSM-5 with silica/alumina ratio of 23 gave a total product yield of 76 +/- 3 wt% (which includes 40 +/- 5 molar yield of xylenes) at its third use, after undergoing regeneration twice previously. We also report herein the effects of different zeolites, catalyst loadings, degrees of unsaturation in the fatty acids, and silica/alumina ratios of zeolite ZSM-5 on the product yields. (C) 2015 Elsevier B.V. All rights reserved.