An active, stable cubic molybdenum carbide catalyst for the high-temperature reverse water-gas shift reaction.

Although technologically promising, the reduction of carbon dioxide (CO2) to produce carbon monoxide (CO) remains economically challenging owing to the lack of an inexpensive, active, highly selective, and stable catalyst. We show that nanocrystalline cubic molybdenum carbide (α-Mo2C), prepared through a facile and scalable route, offers 100% selectivity for CO2 reduction to CO while maintaining its initial equilibrium conversion at high space velocity after more than 500 hours of exposure to harsh reaction conditions at 600°C. The combination of operando and postreaction characterization of the catalyst revealed that its high activity, selectivity, and stability are attributable to crystallographic phase purity, weak CO-Mo2C interactions, and interstitial oxygen atoms, respectively. Mechanistic studies and density functional theory (DFT) calculations provided evidence that the reaction proceeds through an H2-aided redox mechanism.

Effect of surface acidity and basicity of aluminas on asphaltene adsorption and oxidation.

This study investigates the effect of surface acidity and basicity of aluminas on asphaltene adsorption followed by air oxidation. Equilibrium batch adsorption experiments were conducted at 25°C with solutions of asphaltenes in toluene at concentrations ranging from 100 to 3000 g/L using three conventional alumina adsorbents with different surface acidity. Data were found to better fit to the Freundlich isotherm model showing a multilayer adsorption. Results showed that asphaltene adsorption is strongly affected by the surface acidity, and the adsorption capacities of asphaltenes onto the three aluminas followed the order acidic>basic and neutral. Asphaltenes adsorbed over aluminas were subjected to oxidation in air up to 600°C in a thermogravimetric analyzer to study the catalytic effect of aluminas with different surface acidity. A correlation was found between Freundlich affinity constant (1/n) and the catalytic activity. Basic alumina that has the lowest 1/n value, depicting strongest interactions, has the highest catalytic activity, followed by neutral and acidic aluminas, respectively.

Scavenging H(2)S((g)) from oil phases by means of ultradispersed sorbents.

Ultradispersed catalysts significantly enhance rates of reaction and mass transfer by virtue of their extended and easy accessible surface. These attractive features were exploited in this study to effectively capture H(2)S((g)) from an oil phase by ultradispersed sorbents. Sorption of H(2)S((g)) from oil phases finds application for scavenging H(2)S((g)) forming during heavy oil extraction and upgrading. This preliminary investigation simulated heavy oil by (w/o) microemulsions having 1-methyl-naphthalene; a high boiling point hydrocarbon, as the continuous phase. H(2)S((g)) was bubbled through the microemulsions which contained the ultradispersed sorbents. The type and origin of sorbent were investigated by comparing in situ prepared FeOOH and commercial alpha-Fe(2)O(3) nanoparticles as well as aqueous FeCl(3) and NaOH solutions dispersed in the (w/o) microemulsions. The in situ prepared FeOOH nanoparticles captured H(2)S((g)) in a chemically inactive form and displayed the highest sorption rate and capacity. Temperature retarded the performance of FeOOH particles, while mixing had no significant effect.