The deactivation study of titanium dioxide catalyst in thermochemical processes via density functional theory

Abstract

In this study, the investigation of catalytic deactivation of TiO2 by coking was performed using DFT. The effect of the Hubbard U, which was varied as U equal 4 to 6 eV and Van der Waal corrections on electronic properties were also investigated. The effect of temperature in the range of 400-1000°C was also studied. This work aims to understand relatives of coke formation, oxygen vacancy, phase transformation. The increment of the Hubbard U values provide a more accurate quantitative cited by the energy gap from the experimental investigation, the appropriate U value of the A-TiO2 (101) is 4 eV, while the R-TiO2 (110) is 6 eV. The coke formation of C1 is strongly adsorbed on the A-TiO2 (101) surface, while on the R-TiO2 (110) surface, C2 is strongly adsorbed. For oxygen vacancy on coke formation, C2 coke is strongly adsorbed on O-vac A-TiO2 (101) and O-vac R-TiO2 (110) surfaces. This can be suggested that the defect surface is more active than the perfect surface which may lead to higher stability of coke deposition. For the effect of temperature, the interaction between cokes and surfaces becomes weaker when the temperature is increased. Moreover, during the thermochemical process, the TiO2 catalyst can transform anatase to the rutile phase. It is suggested that the coke formation on the R-TiO2 (110) surface is more severe than on the A-TiO2 (101) surface.