Interplay between carbon dioxide enrichment and zinc oxide promotion of copper catalysts in methanol synthesis

Dalebout, Remco; Visser, Nienke L.; Pompe, Cornelia E.; Jong, Krijn P. de; Jongh, Petra E. de

doi:10.1016/j.jcat.2020.10.006

Cited by 18 publications

(37 citation statements)

References 59 publications

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“…A series of CuZnO x /C catalysts, with similar Cu weight loadings (8.0 ± 0.4 wt %) but varying Zn/Cu molar ratios, were prepared via incipient wetness impregnation following a published method. 5 In brief, powdered high-surface-area graphite (TIMREX E-HSAG500, TIMCAL Graphite & Carbon) was dried at ca. 443 K under dynamic vacuum for 1.5 h. The support was impregnated at room temperature under static vacuum to 95% of the total pore volume with an acidified aqueous solution containing 1.8 M copper nitrate (Acros Organics, 99%) and 0–1.8 M zinc nitrate (Sigma-Aldrich, ≥99%).…”

Section: Experimental Sectionmentioning

confidence: 99%

“…1 − 6 Generally accepted is that Cu is the main active component where ZnO x plays a crucial role in promoting the catalyst activity with about an order of magnitude. 5 , 7 − 11 Yet, the exact role of the ZnO x promoter is still under debate, 12 − 14 especially due to a lack of detailed knowledge on the ZnO x speciation, structure, and its interaction with Cu under the typical methanol synthesis conditions at 473–573 K and 20–100 bar. 15 , 16 …”

Section: Introductionmentioning

confidence: 99%

“… 28 , 29 Also in a pure H 2 /CO 2 feed, an optimal Zn coverage of 0.20, or an atomic Zn/Cu ratio of 1.2–1.6, was reported for Cu/ZnO catalysts. 19 , 22 , 23 , 30 , 31 The question remains what the actual state of the ZnO x is during working conditions in different feeds at high pressure (e.g., H 2 /CO feed), syngas enriched with a relevant amount of CO 2 (2–6 vol % 1 − 5 ), or an H 2 /CO 2 feed.…”

Section: Introductionmentioning

confidence: 99%

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Insight into the Nature of the ZnO_x Promoter during Methanol Synthesis

et al. 2022

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Despite the great commercial relevance of zinc-promoted copper catalysts for methanol synthesis, the nature of the Cu–ZnO x synergy and the nature of the active Zn-based promoter species under industrially relevant conditions are still a topic of vivid debate. Detailed characterization of the chemical speciation of any promoter under high-pressure working conditions is challenging but specifically hampered by the large fraction of Zn spectator species bound to the oxidic catalyst support. We present the use of weakly interacting graphitic carbon supports as a tool to study the active speciation of the Zn promoter phase that is in close contact with the Cu nanoparticles using time-resolved X-ray absorption spectroscopy under working conditions. Without an oxidic support, much fewer Zn species need to be added for maximum catalyst activity. A 5–15 min exposure to 1 bar H 2 at 543 K only slightly reduces the Zn(II), but exposure for several hours to 20 bar H 2 /CO and/or H 2 /CO/CO 2 leads to an average Zn oxidation number of +(0.5–0.6), only slightly increasing to +0.8 in a 20 bar H 2 /CO 2 feed. This means that most of the added Zn is in a zerovalent oxidation state during methanol synthesis conditions. The Zn average coordination number is 8, showing that this phase is not at the surface but surrounded by other metal atoms (whether Zn or Cu), and indicating that the Zn diffuses into the Cu nanoparticles under reaction conditions. The time scale of this process corresponds to that of the generally observed activation period for these catalysts. These results reveal the speciation of the relevant Zn promoter species under methanol synthesis conditions and, more generally, present the use of weakly interacting graphitic supports as an important strategy to avoid excessive spectator species, thereby allowing us to study the nature of relevant promoter species.

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Section: Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Insight into the Nature of the ZnO_x Promoter during Methanol Synthesis

et al. 2022

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“…This is advantageous, as even though from an environmental perspective, the direct hydrogenation of CO 2 would be desirable, catalyst stability would be compromised 4 because of the high water concentrations unmitigated by WGS. 5 It should be noted that the direct conversion of CO 2 to methanol through hydrogenation is structure sensitive, i.e. catalytic properties are strongly influenced by the dimension of the catalytically active particles, and the geometry and composition of the catalyst-substrate interface.…”

Section: Introductionmentioning

confidence: 99%

Effect of linker functionalisation on the catalytic properties of Cu nanoclusters embedded in MOFs in direct CO and CO₂ reduction by H₂

Pompe

Szilágyi

2021

Faraday Discuss.

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“…It has been determined from isotope labeling experiments that the reaction proceeds more efficiently from CO 2 than CO ( 16 ), but it remains unresolved how the mixture of the two gases yields the highest production rate of methanol ( 17 ). However, the cooperative action of ZnO x and CO 2 has also been reported to enhance the rate of methanol synthesis from CO, even when the CO 2 fraction is as low as 3% ( 18 ).…”

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The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst

Amann

Klötzer

Degerman

et al. 2022

Science

102

117

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The active chemical state of zinc (Zn) in a zinc-copper (Zn-Cu) catalyst during carbon dioxide/carbon monoxide (CO 2 /CO) hydrogenation has been debated to be Zn oxide (ZnO) nanoparticles, metallic Zn, or a Zn-Cu surface alloy. We used x-ray photoelectron spectroscopy at 180 to 500 millibar to probe the nature of Zn and reaction intermediates during CO 2 /CO hydrogenation over Zn/ZnO/Cu(211), where the temperature is sufficiently high for the reaction to rapidly turn over, thus creating an almost adsorbate-free surface. Tuning of the grazing incidence angle makes it possible to achieve either surface or bulk sensitivity. Hydrogenation of CO 2 gives preference to ZnO in the form of clusters or nanoparticles, whereas in pure CO a surface Zn-Cu alloy becomes more prominent. The results reveal a specific role of CO in the formation of the Zn-Cu surface alloy as an active phase that facilitates efficient CO 2 methanol synthesis.

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Interplay between carbon dioxide enrichment and zinc oxide promotion of copper catalysts in methanol synthesis

Cited by 18 publications

References 59 publications

Insight into the Nature of the ZnO_x Promoter during Methanol Synthesis

Insight into the Nature of the ZnO_x Promoter during Methanol Synthesis

Effect of linker functionalisation on the catalytic properties of Cu nanoclusters embedded in MOFs in direct CO and CO₂ reduction by H₂

The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst

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Interplay between carbon dioxide enrichment and zinc oxide promotion of copper catalysts in methanol synthesis

Cited by 18 publications

References 59 publications

Insight into the Nature of the ZnOx Promoter during Methanol Synthesis

Insight into the Nature of the ZnOx Promoter during Methanol Synthesis

Effect of linker functionalisation on the catalytic properties of Cu nanoclusters embedded in MOFs in direct CO and CO2 reduction by H2

The state of zinc in methanol synthesis over a Zn/ZnO/Cu(211) model catalyst

Contact Info

Product

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Insight into the Nature of the ZnO_x Promoter during Methanol Synthesis

Insight into the Nature of the ZnO_x Promoter during Methanol Synthesis

Effect of linker functionalisation on the catalytic properties of Cu nanoclusters embedded in MOFs in direct CO and CO₂ reduction by H₂