Naphthenic acids in crude oil is a main contributor to the corrosion problem in the petroleum industry and removal of these acids from the crude oil fraction become a great concern nowadays. Catalytic neutralization is an alternative technique to be investigated in this study. A basic chemical with a dosing of 0.4% and 4% of ammonia solution in ethylene glycol (NH3-EG) were used as the acid removal agent with a concentration of 100 mg/L, 500 mg/L, and 1000 mg/L for three different crude oils which are Petronas Penapisan Melaka heavy (crude A) and light crude (crude B) and Korean crude (crude C). A series of alkaline earth metal oxide catalysts; calcium, barium and magnesium supported onto alumina with different calcination temperatures were used to enhance the reaction. The results showed 67.4% (3000 mg/L of 4% NH3-EG) reduction in TAN for crude A and 78.7% (10,000 mg/L of 4% NH3-EG) reduction for crude C by using the best studied catalyst which was Ca/Al2O3 with a calcination temperature of 1100 ℃. For crude B, there was 71.2% reduction of TAN with 1000 mg/L of 0.4% of NH3-EG. Additionally, based on the results obtained, a mechanistic naphthenic acid reduction reaction pathway was postulated.