A periodic density functional theory study of gallium-exchanged mordenite

Abstract

Several reconstructions of catalytic active sites in gallium-exchanged mordenite have been analyzed using periodic density functional theory method. It is found that a number of structures in which gallium is present as Ga (III) H x , Ga (II) Ga (II) H x , and Ga (III) Ga (I) H x can be reached under alkane dehydrogenation conditions. The transition barrier for the rate determining step in alkane dehydrogenation are evaluated. The values indicate that these gallium structures can catalyze alkane dehydrogenation and suggest an alternative reaction route in addition to those that have been proposed before.

Theoretical Study of CuIY Zeolite: Structure and Electronic Properties

“…[4][5][6][7][8][9][10] Larger unitcell zeolites like mordenite (144 atoms) and ZSM-5 (288 atoms) have also been studied, either fully siliceous 11,12 or with one (Al, cation) site and a guest molecule. [13][14][15][16][17] Mordenite with the natural composition, that is, 8 (Al, Na) per unit cell (152 atoms), has also been investigated. 11 Sn-BEA, with one Sn per unit cell, has also been studied recently.…”

Periodic model of an LTA framework

“…In recent years, such fully periodic calculations have become increasingly popular, especially for studies of the reactivity, functionalization, and catalytic applications of ionexchanged zeolites [20][21][22][23][24][25]. Such an approach (among others) allows various structural changes and the creation of active centers in zeolite structures to be analyzed and the energies and stabilities of reactions between ion-exchanged zeolites and (for example) organic molecules to be calculated [20][21][22][23].…”

“…Such an approach (among others) allows various structural changes and the creation of active centers in zeolite structures to be analyzed and the energies and stabilities of reactions between ion-exchanged zeolites and (for example) organic molecules to be calculated [20][21][22][23]. Periodic models are also used to study bonding mechanisms and the tendency for various sites to be occupied by extra-framework ions in zeolite frameworks, as well as the influence of these ions on the adsorption properties of the framework [23][24][25].…”

Swift hopping gallium over [AlO4]− tetrahedra in Ga/ZSM‐5: A DFT study

“…Most computational models include AlO 2 Ga (Fig. 1) cycle fragment representing the core of catalytic site 11–16. Some reaction pathways have stable intermediates with weak‐bonded neutral gallium containing molecules with one of [AlO 4 ] oxygen atom 11, 12, 16.…”

“…Some reaction pathways have stable intermediates with weak‐bonded neutral gallium containing molecules with one of [AlO 4 ] oxygen atom 11, 12, 16. However, a structure with neutral GaH bonded to both oxygen atoms of [AlO 4 ] was reported in mordenite 15 with charge compensating proton on third oxygen of aluminum–oxygen tetrahedron. There are three possible positions of gallium cation at aluminum tetrahedron (Fig.…”