Methanol synthesis from CO2 hydrogenation over a Pd4/In2O3 model catalyst: A combined DFT and kinetic study

Abstract

Methanol synthesis from CO 2 hydrogenation on a model Pd/In 2 O 3 catalyst, i.e. Pd 4 /In 2 O 3 , has been investigated using density functional theory (DFT) and microkinetic modeling. Three possible routes in the reaction network of CO 2 + H 2 → CH 3 OH + H 2 O have been examined. Our DFT results show that the HCOO route competes with the RWGS route whereas a high activation barrier blocked the HCOOH route kinetically. The DFT results also suggest that H 2 COO* + H* ↔ H 2 CO* +OH* and cis-COOH* + H* ↔CO* + H 2 O* are the rate limiting steps in the HCOO route and the RWGS route, respectively. Microkinetic modeling results demonstrate that the HCOO route is the dominant pathway for forming methanol from CO 2 hydrogenation. Furthermore, the activation of the H adatom on the Pd cluster and the presence of H 2 O on the In 2 O 3 substrate play important roles in promoting methanol production. The hydroxyl adsorbed at the interface of Pd 4 /In 2 O 3 induces structural transformation of the supported Pd 4 cluster from a butterfly shape into a tetrahedron one. This structural change not only indicates the dynamical nature of the supported nanocatalysts during the reaction but also causes the final hydrogenation step to change from CH 3 O to H 2 COH.

CO on Supported Cu Nanoclusters: Coverage and Finite Size Contributions to the Formation of Carbide via the Boudouard Process

“…Changes also in the kinetic barriers of the dissociation process cannot be excluded, as reported in the literature, but we could not tackle this point due to the large size of the system. 66,67 However, we recall that the cluster does not wet the surface, 55 and that CO does not stick onto the oxide surface.…”

A novel Core–Shell structured CuIn@SiO2 catalyst for CO2 hydrogenation to methanol

“…The adsorbed OH* reacts with H* to obtain H 2 O, and the CO* is desorbed to form CO gas. This reaction pathway can be suppressed by limiting surface COOH formation and thus results in high selectivity toward methanol . Moreover, HCOO* can be hydrogenated to H 2 COO* and H 2 CO*.…”

“…In addition, the defective In 2 O 3 displayed even better activity for CO 2 hydrogenation to methanol and the reaction followed a mechanism including the cyclic creation and annihilation of oxygen vacancies. They also predicted that the Pd/In 2 O 3 catalyst could be an excellent catalyst for CO 2 hydrogenation to methanol through DFT study . In addition to theoretical studies, there are several experimental studies made for methanol synthesis from CO 2 hydrogenation on In 2 O 3 and In 2 O 3 ‐based catalysts.…”

CO2 hydrogenation on Pt, Pt/SiO2 and Pt/TiO2: Importance of synergy between Pt and oxide support

“…[14,15] Previous studies have shown that Cu is very selective to convert CO 2 to CH 3 OH by H 2 , and the activity and selectivity can be further promoted by forming alloys or using oxides as supports. [1,[16][17][18][19][20][21][22][23] In comparison, Pt-based catalysts behave differently and are reported to be highly selective to CO [2], which undergoes the reverse-water-gas shift (RWGS) reaction via either carboxyl (*HOCO) or formate (*HCOO) intermediates. [1,[24][25][26] The production of CH 4 is also observed during this process; however, the corresponding selectivity is much lower than that of CO. [2] It is desirable to promote and control the selectivity of a catalyst to convert CO 2 to CO, CH 3 OH or CH 4 .…”