A novel process was developed for oxidative desulfurization (ODS) in the absence of a phase transfer catalyst (PTC) using only Keggin heteropolyacids and their aluminum salts as catalysts. Reactions were performed in biphasic mixtures of isooctane/acetonitrile, with dibenzothiophene (DBT) as a model sulfur compound and hydrogen peroxide as the oxidant. Remarkably, only the AlPMo12O40-catalyzed reactions resulted in complete oxidation of DBT into DBT sulfone, which was totally extracted by acetonitrile, reducing the sulfur content of isooctane from the 1000？ppm to <1？ppm. Ranking of catalyst efficiency is as follows: AlPMo12O40？>？H3PMo12O40？>？AlPW12O40？>？H3PW12O40. The absence of a PTC, acidic organic peroxides, and the use of hydrogen peroxide, an environmentally benign oxidant, make up the positive aspects of AlPMo12O40-catalyzed ODS reactions. In these reactions, high rates of DBT removal (ca. 100%) were achieved within a short time (ca. 2 hours) and under mild reaction conditions. 1. Introduction Demand for the production and use of more environment-friendly fuels are increasing due to the introduction of the legislative regulations requiring rigid control of green-house gas emissions [1]. Nowadays, many countries are introducing stringent regulations to reduce sulfur content in liquid fuels to ultralow levels, making the development of deep desulfurization processes an important research goal [2]. Among the main industrial processes for the sulfur removal of liquid fuels, the most important is referred as hydrodesulfurization (HDS) and operates with oxide-supported heterogeneous metal catalysts, typically Co- (or Ni-) promoted Mo/Al2O3, under high temperatures (593–653？K) and hydrogen pressures (3–7？MPa) [3]. The HDS process is an efficient technology used by the petroleum refining industries to remove aliphatic and acyclic sulfur compounds present in the liquid fuels. However, due to the high stereo hindrance and as consequence of proximity between the values of C–S and C–H bond energy, some sulfured aromatic compounds such as dibenzothiophene (DBT) and their derivatives are especially refractory to the HDS processes [4]. Moreover, the lower sulfur level achieved by the HDS process is still high when compared to the futures legal exigencies (ca. 50–15？ppm) [5]. Consequently, the development of processes for the fuels production with low sulfur content is a great challenge to overcome [6]. Alternative processes to HDS, in which high temperatures or hydrogen pressures are avoided, have been proposed, and the main examples are the biodesulfurization
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