Polyoxometalate as effective catalyst for the deep desulfurization of diesel oil

Aiming at the deep desulfurization of the diesel oil, a comparison of the catalytic effects of several Keggin type POMs, including H3PWxMo12−xO40 (x = 1, 3, 6), Cs2.5H0.5PW12O40, and H3PW12O40, was made, using the solution of DBT in normal octane as simulated diesel oil, H2O2 as oxidant, and acetonitrile as extractant. H3PW6Mo6O40 was found to be the best catalyst, with a desulfurization efficiency of 99.79% or higher. Hence, it is promising for the deep desulfurization of actual ODS process. The role of the main factors affecting the process including temperature, O/S molar ratio, initial sulfur concentration, and catalyst dosage, was investigated, whereby the favourable operating conditions were recommended as T = 60 °C, O/S = 15, and a catalyst dosage of 6.93 g (H3PW6Mo6O40)/L (simulated diesel). With the aid of GC–MS analysis, sulfone species was confirmed to be the only product after reaction for 150 min. Furthermore, macro-kinetics of the process catalyzed by H3PW6Mo6O40 was studied, from which the reaction orders were found to be 1.02 to DBT and 0.38 to H2O2, and the activation energy of the reaction was found to be 43.3 kJ/mol. Moreover, the catalyst recovered demonstrated almost the same activity as the fresh.