Luca

Publication date: 1 November 2018

Source: Computational and Theoretical Chemistry, Volume 1143

Author(s): Yung-Ching Chou

Publication date: 1 October 2018

Source: Computational and Theoretical Chemistry, Volume 1141

Author(s): Laimutis Bytautas, Jorge Dukelsky

Publication date: October 2018
Source:Surface Science, Volume 676
Author(s): Yuhai Hu, Keith Griffiths
SOx poisoning has been a critical problem in the chemistry of selective catalytic reduction of NOx, and many fundamental issues surrounding the reactions remain unclear. In this paper, reactions taking place in the ¹³C2H5OHNO-S¹⁸O2 O2 system on a platinum single crystal surface were studied. Oxidation of ¹³C2H5OH by S¹⁸O2 proceeds mainly through ¹⁸O-H reaction, and oxidation of the backbone carbon atoms can occur at high S¹⁸O2 exposures, e.g., 1.6 Ls of S¹⁸O2 for 0.4 L of ¹³C2H5OH. Thus, the presence of S¹⁸O2 only slightly suppresses the catalytic reduction of NO by ¹³C2H5OH. Co-adsorbed O2 evidently exerts a suppressive effect. When oxygen is lean (relative to S¹⁸O2), the S¹⁸O2 O2 reactions mainly give rise to surface sulphoxy species at temperatures between 400 and 500 K and thus, the NO-¹³C2H5OH reactions can still proceed. The NO reduction reaction is completely suppressed when oxygen is rich, a result of the Pt surface being passivated. This finding provides a valuable guide for optimizing the reaction atmosphere to improve the efficiency of the selective catalytic reduction of NO by hydrocarbons (or oxygen-containing fragments from oxidation of hydrocarbons in this case).

Graphical abstract

Abstract

In this work, the effect of the exact exchange in hybrid functionals based on one parameter is explored over the electronic structure of \(\hbox {Ti}_2\hbox {O}_3\) , \(\hbox {V}_2\hbox {O}_3\) , \(\hbox {Cr}_2\hbox {O}_3\) , \(\hbox {Fe}_2\hbox {O}_3\) , \(\hbox {MnO}, \hbox {SiO}_2\) , \(\hbox {GeO}_2\) , and \(\hbox {SnO}_2\) , such that oxides with different nature are included in this data set. Structural parameters and magnetic states of these oxides are reproduced according to experimental information, which are discussed in the context of the exact exchange inclusion. Several exchange-correlation functionals are considered to reach this goal, two of them, HSE06 and B1WC, which were designed ad hoc to study metal oxides are contrasted with hybrid exchange-correlation functionals that contain a fraction ( \(\alpha \) ) of the exact exchange, like PBE0. Thus, in this work, hybrid functionals where \(\alpha \) is varied systematically provide a linear relationship between band gap and \(\alpha \) , which gives one way to match the theoretical band gap with experimental information. If this optimum \(\alpha \) is used to predict cell parameters or bulk modulus, then the corresponding results are close to experimental data. For the systems considered in this work, all-electron calculations were performed using a periodic ab initio code, which uses Gaussian localized basis set functions for the expansion of Bloch orbitals by linear combinations of atomic orbitals.

The 16th International Congress of Quantum Chemistry (16th ICQC) will be held in ‘le Palais de l’Europe’ in the town of Menton, France, between 18−23 June 2018. It brings together the international community of theoretical chemists in the form of a one-week conference aimed at presenting the state of the art and latest advances in terms of developments and applications in the field of theoretical and computational chemistry.

Physical Chemistry Chemical Physics (PCCP) is pleased to be supporting the meeting and will provide two poster prizes.

Register now: the deadline for registration is 31 May 2018 and abstract submission will close on 15 May 2018.