In situ IR studies on the mechanism of methanol synthesis from CO/H2 and CO2/H2 over Cu-ZnO-Al2O3 catalyst

Abstract

Methanol synthesis from CO/H 2 and CO 2 /H 2 was carried out at atmospheric pressure over Cu/ZnO/Al 2 O 3 catalyst. The formation and variation of surface species were recorded by in situ FT-IR spectroscopy. The result revealed that both CO and CO 2 can serve as the primary carbon source for methanol synthesis. For CO/H 2 feed gas, only HCOOZn was detected; however, for CO 2 /H 2 , both HCOO-Zn and HCOO-Cu were observed, and without CH 3 O-Cu. HCOOZn was the key intermediate. A scheme of methanol synthesis and reverse water-gas shift (RGWS) reaction was proposed.

Comment on the “In situ IR studies on the mechanism of methanol synthesis from CO/H2 and CO2/H2 over Cu-ZnO-Al2O3 catalyst” by Wang et al

“…A closer inspection of the set of narrow bands observed by Wand et al [1] reveals that those exactly match the rotovibrational bands associated with gas-phase water, which is given in Fig. 1(b), collected at the same resolution (i.e.…”

“…5 reported by Wang et al in their paper [1] and it appears again that those are all assignable to gasphase water. Truly carbonate species can actually be observed on the spectra reported by the authors [1], i.e. the very broad bands at ca.…”

“…4 cm −1 ). This observation strongly suggests that all the narrow bands observed by Wang et al [1] are due to the absorption of water molecules, from ambient air and/or present in the cell due to the release/formation of water during the temperature-programmed reaction.…”

“…Wang et al [1] have recently reported an in situ IR investigation of the mechanism of methanol synthesis from CO/H 2 and CO 2 /H 2 mixtures over a Cu-based catalyst. Some IR bands were assigned by these authors to surface adsorbates such as formates and carbonates ( Fig.…”

Mechanism and kinetics for methanol synthesis from CO2/H2 over Cu and Cu/oxide surfaces: Recent investigations by first-principles-based simulation

“…It was also found that the selectivity to methanol varies significantly from catalyst to catalyst and is also sensitive to reaction condition, e.g., from < 1% [3,13] to > 99% [4]. To understand these puzzles, experimental studies on model catalysts using various techniques, especially in situ infrared spectrum [16], have been carried out to shed light into the microscopic mechanism of the reaction. It was shown that HCOO and H 3 CO are present as the common intermediates on different catalysts, implying that the addition of oxides, however, may not change markedly the catalytic mechanism.…”