Study of the properties of molybdenum compounds for the catalytic oxidation of logistic fuels

This work is focused on the study of the properties of molybdenum compounds as catalytic materials for the reforming of logistic fuels such as gasoline and jet fuel. The starting point for this investigation was the previous work performed in our lab by other fellow researchers about the study of molybdenum carbide, Mo2C, as catalytic material for the reforming of methane. Thus, encouraged by the promising results with methane, Mo2C was evaluated as potential catalyst for the steam reforming of liquid hydrocarbons. Our data indicates that Mo2C displays high activity for the reforming of isooctane--a surrogate gasoline--even at temperatures as low as 700 C. However, as the temperature becomes lower than 700 C, the catalytic activity of Mo2C experiences a decline to eventually disappear. The particular electron configuration of the Mo atoms appears to be responsible for the stability issues, given that it allows phase transitions that can significantly affect the catalytic activity. Thus, Mo2C is thought to loss activity due to an oxidation process that leads to the formation of Mo dioxide. The presence of the species Mo4+ (assigned to the Mo dioxide phase) on the surface of active spent samples of Mo carbide led us to hypothesize that this oxide phase may play a role in the catalytic activity of Mo2C. To test this hypothesis, MoO2 was tested as reforming catalyst and our experimental results showed that MoO 2 can be used as steam reforming catalyst with a higher activity than that of Mo2C itself. Nevertheless, the structure and properties of this transition metal oxide led us to believe that Mo dioxide may work in a more efficient manner under partial oxidation conditions. Our findings were in agreement with this hypothesis and demonstrated that Mo exhibits high catalytic activity for the reforming of both gasoline and jet fuel. In addition to the catalytic activity, Mo dioxide also displays a significant coking resistance as compared with Ni catalysts. Finally, MoO2 was tested for sulfur poisoning and found to tolerate concentrations as high as 1000 ppm of either thiophene or benzothiophene without affecting in high extent the catalytic performance