Mechanism of CO₂conversion to methanol over Cu(110) and Cu(100) surfaces

Abstract

<p>Density functional methods are applied to explore the reaction mechanism for CO₂ hydrogenation to methanol over low-index Cu surfaces, namely Cu(110) and Cu(100).</p>

Concluding remarks: Reaction mechanisms in catalysis: perspectives and prospects

“…Recently, as a precursor to a mechanistic investigation of the Cu/ZnO system, a detailed computational (DFT) study was reported of the mechanism of CO 2 hydrogenation over metallic copper surfaces. 19 The mechanistic possibilities are summarized in Fig. 7.…”

“…Mechanisms of hydrogenation are, however, widely debated; see, for example, the recent review of Nitopi et al 18 The Cu/ZnO catalyst used in methanol synthesis from both CO 2 and syngas has been intensively studied, without the emergence of clear Fig. 7 Schematic depicting all of the mechanistic pathways for CO 2 hydrogenation to methanol over Cu(110) and Cu(100) surfaces investigated by Higham et al 19 Intermediates framed with orange borders correspond to those unique to the CO hydrogenation processes subsequent to CO 2 dissociation, whilst the intermediates framed with purple borders are unique to direct CO 2 hydrogenation processes. The species and intermediates framed with black borders are common to all of the mechanistic pathways investigated.…”

Understanding catalytic CO2 and CO conversion into methanol using computational fluid dynamics

“…Apart from their potential as a reactor design and optimization tool, CFD models also have many benefits as an investigation tool. Unlike DFT, [34][35][36][37] Aspen, 9,38 and Matlab 8,21,39 models, CFD considers local variations in flow properties, such as temperature, pressure, and diffusion, along with species concentrations, to evaluate chemical reactions. In addition, CFD models offer a dynamic, in situ representation of the distribution, conversion and spatial transfer of chemical species.…”

“…The exclusion of direct CO hydrogenation seems counter-intuitive, since CO hydrogenation, while less impactful than CO 2 hydrogenation, can still occur. Its significance however, varies greatly in the literature; as an example, Grabow and Mavrikakis 34 predicted ≈1/3 of MeOH being produced from CO, while Sahibzada et al 23 predicted MeOH synthesis from CO 2 may be 20 times higher than MeOH synthesis from CO. Grabow and Mavrikakis 34 investigated the Cu(111) surface of the commercial catalyst, while in the DFT study of Higham et al 37 the Cu(110) and the Cu(100) facets were investigated instead; it was identified that the Cu(110) and Cu(100) facets could be even more active for CO 2 dissociation into CO and its subsequent hydrogenation to MeOH 37 compared to the Cu(111) facet, yet the impact of CO hydrogenation in MeOH synthesis was not defined. Wilkinson et al 43 investigated the species concentration at different lengths along the catalytic bed, by having different catalyst loads in the reactor each time.…”

“…In addition, combining our available investigative methods can lead to invaluable information regarding the MeOH synthesis process. As an example, Higham et al37 predicted that CO 2 could bond dissociatively on Cu(110) and Cu(100) facets, thus initialising CO hydrogenation on these sites. Yet the adsorption of CO feedstock on these facets was not considered.…”