Source and major species of CH_x(x = 1–3) in acetic acid synthesis from methane–syngas on Rh catalyst: a theoretical study

Abstract

Density functional calculations have been carried out to investigate the source and major species of CH x (x ¼ 1-3) involved in acetic acid synthesis from methane-syngas on the Rh(111) surface. All possible formation pathways of CH x (x ¼ 1-3) from methane and syngas have been systematically investigated. For CH x formation from methane, our results show that CH is the most abundant species; for CH x formation from syngas, all CH x (x ¼ 1-3) species form from CHO by CO hydrogenation, and the optimal formation routes of CH x show that CH and CH 3 are the most abundant species rather than CH 2 and CH 3 OH. On the other hand, CH formed by methane is more favourable than CH and CH 3 formed by syngas; meanwhile, CO insertion into CH x species to form C 2 oxygenates as acetic acid precursors is more favourable than CO hydrogenation to CH and CH 3 . As a result, in acetic acid synthesis from methanesyngas, CH x (x ¼ 1-3) species come from methane rather than syngas, and the corresponding primary species is CH. In addition, the CO in syngas is predominantly responsible for insertion reactions that produce CHCO, which is a C 2 oxygenate precursor leading to the formation of acetic acid. Furthermore, microkinetic modelling analysis shows that the major product of acetic acid synthesis from methanesyngas on the Rh(111) surface is CH 3 COOH, and that the production of CH 3 OH cannot compete with that of CH 3 COOH.

Insight into Crystal Phase Dependent CO Dissociation on Rh Catalyst from DFT and Microkinetic Modeling

“…The metal Rh has been known as a promising element toward the formation of ethanol from CO hydrogenation. ,,, The Rh catalyst with FCC crystal phase structure has been studied widely in both experiment and theory. The experimentally prepared Rh-based catalysts with FCC crystal phase exhibit a high selectivity of C 2+ oxygenates but a low CO conversion. , Numerous DFT studies have been focused on CO dissociation on FCC Rh surfaces. − The results showed that the H-assisted pathway through CHO is the underlying activation way on Rh surfaces, and the studies also indicated that the stepped surfaces have higher activity than the flat surfaces. − However, CO dissociation on HCP Rh has rarely been studied, although the other metal nanoparticle with HCP crystal phase was reported to show different catalytic properties compared to FCC crystal phase. − Recent studies by Huang et al have successfully synthesized HCP Rh crystal phase by the experimental technology for the first time. As a result, the metal Rh can exist in the form of HCP and FCC crystal phase.…”

Preparation of TiO2 Nanorods Composites Doped with Silver Nanoparticles and Their Bactericidal Properties under Visible Light Irradiation

“…We previously synthesized TiO 2 NR using a low temperature hydrothermal method at normal pressure, employing NaF or KBr as shape control agent. [ 24,32 ] In this study, we introduced the Ag precursors into the system to enable in situ formation of Ag nanoparticles that can tightly adhere to the surfaces of TiO 2 nanorods during refluxing at 100 °C. The SEM and TEM images of the TiO 2 NR–Ag composite nanoparticles and pure TiO 2 NR were shown in Figure , respectively.…”

Thermodynamic and Kinetic Study on Carbon Dioxide Hydrogenation to Methanol over a Ga3Ni5(111) Surface: The Effects of Step Edge

“…In order to estimate the selectivity of the major production of CH 4 and CH 3 OH on Ga 3 Ni 5 (111) surface, microkinetic modeling − has been used to calculate the reaction rate of the major production and the overall reaction rate under experimental conditions (1 atm, CO 2 :H = 1:3, T = 500–600 K). The detailed information about microkinetic modeling is given in section 3 of the Supporting Information.…”