A method for deep desulfurization of transportation fuels was presented. Reactive conversion of sulfur compounds and the following adsorption occurred inside adsorbents. The condensation reaction with formaldehyde catalyzed by phosphomolybdic acid was shown effective for the removal of thiophenic and benzothiophenic. c compounds. Thiophene or benzothiophene of model fuels was completely removed. Coupling with an oxidation reaction, the total sulfur content of commercial fuels was dropped to below 15 ppm. Appropriate desulfur condition was at 70-80 degrees C and ambient pressure without consumption of hydrogen. Saturated adsorbent was regenerated with heating in air at 400 degrees C, and the sulfur capacity was almost fully recovered. Fuel quality was not negatively affected by the desulfur operation. (C) 2009 American Institute of Chemical Engineers AIChE J, 55: 1872-1881, 2009