Ab Initio Calculation of Surface Thermochemistry for Popular Solid Transition Metal-Based Species.

This work reports the thermochemistry calculations for solid-phase periodic models of ten popular transition metal-based species. These model structures were refined to stable geometry by geometric optimization along with calculating the thermodynamic properties including enthalpy, entropy, heat capacity at constant pressure, and Gibbs free energy by DMol3 package via first-principles ab initio calculations. The temperature-dependent thermochemistry values were converted to a NASA seven-polynomial format. The behavior of different thermodynamic parameters based on temperature was investigated and their comparative analysis was done. A higher number of atoms tends to show higher thermodynamic values. Moreover, these thermodynamic values agree reasonably well with previously reported experimental and computational values. Metal copper shows higher thermodynamic values as compared to its oxide. The thermodynamic properties of lanthanum-based oxides have been newly calculated through the ab initio method. Amorphous structures reveal higher thermodynamic values compared to their crystalline counterparts. A comparison between different transition metal-based species gives a better understanding of the different crystalline structures and their surface sites. These calculated thermodynamic data and polynomials can be used for a variety of thermodynamic calculations and kinetic modeling.

An efficient and innovative catalytic reactor for VOCs emission control.

Efficient mixing and thermal control are important in the flow reactor for obtaining a high product yield and selectivity. Here, we report a heterogeneous chemical kinetic study of propene oxidation within a newly designed catalytic jet-stirred reactor (CJSR). To better understand the interplay between the catalytic performances and properties, the CuO thin films have been characterized and the adsorbed energies of propene on the adsorbed and lattice oxygen were calculated using density functional theory (DFT) method. Structure and morphology analyses revealed a monoclinic structure with nano-crystallite size and porous microstructure, which is responsible for holding an important quantity of adsorbed oxygen. The residence time inside the flow CJSR (1.12-7.84 s) makes it suitable for kinetic study and gives guidance for scale-up. The kinetic study revealed that using CJSR the reaction rate increases with O2 concentration that is commonly not achievable for catalytic flow tube reactor, whereas the reaction rate tends to increase slightly above 30% of O2 due to the catalyst surface saturation. Moreover, DFT calculations demonstrated that adsorbed oxygen is the most involved oxygen, and it has found that the pathway of producing propene oxide makes the reaction of C3H6 over CuO surface more likely to proceed. Accordingly, these findings revealed that CJSR combined with theoretical calculation is suitable for kinetic study, which can pave the way to investigate the kinetic study of other exhaust gases.