The influence of ZnO on the differential heat of adsorption of CO on Cu catalysts: a microcalorimetric study

d’Alnoncourt, Raoul Naumann

doi:10.1016/s0021-9517(03)00288-4

Cited by 72 publications

(15 citation statements)

References 29 publications

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“…This shows that the KIE and thus the nature of the RDS of CO 2 hydrogenation to methanol are not affected by different supports or different active metals within the range of tested materials despite very different performance in methanol synthesis. This observation provides support for the view that the widely observed promotional effect of ZnO on Cu-based catalysts [2,[36][37][38] affects the activity of methanol synthesis, but does not change its mechanism. We have recently shown that this promotion effect can be successfully modeled by assuming the active site to be a fully Zn-decorated surface step of Cu [25].…”

Section: Methanol Synthesissupporting

confidence: 80%

Hydrogenation of CO2 to methanol and CO on Cu/ZnO/Al2O3: Is there a common intermediate or not?

Kunkes

Studt

Abild‐Pedersen

et al. 2015

Journal of Catalysis

257

207

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This work is dedicated to the memory and achievements of Dr. Haldor Topsøe.Keywords: H/D substitution Methanol Copper Reverse water gas shift DFT Kinetics Mechanism CO 2 hydrogenation a b s t r a c t H/D exchange experiments on a Cu/ZnO/Al 2 O 3 catalyst have shown that methanol synthesis and RWGS display a strong thermodynamic isotope effect, which is attributed to differences in the zero-point energy of hydrogenated vs. deuterated species. The effect is larger for methanol synthesis and substantially increases the equilibrium yield in deuterated syngas. In the kinetic regime of CO 2 hydrogenation, an inverse kinetic isotope effect of H/D substitution was observed, which is stronger for methanol synthesis than for CO formation suggesting that the two reactions do not share a common intermediate. Similar observations were also made on other catalysts such as Cu/MgO, Cu/SiO 2 , and Pd/SiO 2 . In contrast to CO 2 hydrogenation, the CO hydrogenation on Cu/ZnO/Al 2 O 3 did not show such a strong kinetic isotope effect indicating that methanol formation from CO 2 does not proceed via consecutive reverse water gas shift and CO hydrogenation steps. The inverse KIE is consistent with formate hydrogenation being the rate-determining step of methanol synthesis from CO 2 . Differences in the extent of product inhibition by water, observed for methanol synthesis and reverse water gas shift indicate that the two reactions proceed on different surface sites in a parallel manner. The consequences for catalyst design for effective methanol synthesis from CO 2 are discussed.

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Section: Methanol Synthesissupporting

confidence: 80%

Hydrogenation of CO2 to methanol and CO on Cu/ZnO/Al2O3: Is there a common intermediate or not?

Kunkes

Studt

Abild‐Pedersen

et al. 2015

Journal of Catalysis

257

207

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“…Investigation of model catalysts, such as the above‐mentioned Pt/Fe 3 O 4 , is a general strategy to reduce the complexity of real systems. Another side on the coin is to accurately understand the complicated industrial catalysts, say, Cu/ZnO, a major industrial catalyst for methanol synthesis (Naumann d'Alnoncourt et al ., ; Naumann d'Alnoncourt et al ., ; Behrens et al ., ; Schott et al ., ). The ZnO stabilizes the Cu nanoparticle within the Cu/ZnO system structure, due to a SMSI and a synergistic effect that tunes the catalyst.…”

Section: Industrial Catalyst Cu/znomentioning

confidence: 99%

Real‐space observation of strong metal‐support interaction: state‐of‐the‐art and what's the next

Shi

Zhang

et al. 2015

Journal of Microscopy

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The real-space resolving of the encapsulated overlayer in the well-known model and industry catalysts, ascribed to the advent of dedicated transmission electron microscopy, enables us to probe novel nano/micro architecture chemistry for better application, revisiting our understanding of this key issue in heterogeneous catalysis. In this review, we summarize the latest progress of real-space observation of SMSI in several well-known systems mainly covered from the metal catalysts (mostly Pt) supported by the TiO2 , CeO2 and Fe3 O4 . As a comparison with the model catalyst Pt/Fe3 O4 , the industrial catalyst Cu/ZnO is also listed, followed with the suggested ongoing directions in the field.

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“…Furthermore, it is proposed that high coverages of oxygen-containing intermediates like formate only exist under industrially relevant high-pressure conditions and lead to a partial oxidation of the metallic Zn sites due to the oxophilic nature of Zn compared with Cu 0 13 . However, there is no characterisation method available for the Cu/ZnO/Al 2 O 3 catalyst typically operated above 200 °C and 50 bar 4 , which is able to identify this oxidising effect, because the adjustment of both high-temperature and high-pressure conditions and surface sensitivity is technically impossible for typical single-crystal investigations 11 , transient in situ experiments 17 , 18 , adsorption and desorption studies 12 , 19 , in situ infrared (IR) spectroscopy 11 , 20 , N 2 O frontal chromatography 12 , 19 , X-ray photoelectron spectroscopy (XPS) 11 , 12 , 15 , 19 , ambient pressure XPS 13 , neutron scattering 13 , microcalorimetry 21 , 22 , scanning tunnelling microscopy 11 , in situ IR reflection-absorption spectroscopy 11 , high-resolution transmission electron microscopy (TEM) 14 , 23 , in situ TEM 24 , electron energy loss spectroscopy 14 , in situ X-ray absorption spectroscopy 16 , or operando X-ray diffraction 25 . To confirm the positive charge of the Zn species in close contact with Cu 0 , we establish a surface-sensitive operando method, which allows us to inject selective reversible poisons as probe molecules such as NH 3 into the syngas feed.…”

Section: Introductionmentioning

confidence: 99%

Identifying the nature of the active sites in methanol synthesis over Cu/ZnO/Al2O3 catalysts

2020

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The heterogeneously catalysed reaction of hydrogen with carbon monoxide and carbon dioxide (syngas) to methanol is nearly 100 years old, and the standard methanol catalyst Cu/ ZnO/Al 2 O 3 has been applied for more than 50 years. Still, the nature of the Zn species on the metallic Cu 0 particles (interface sites) is heavily debated. Here, we show that these Zn species are not metallic, but have a positively charged nature under industrial methanol synthesis conditions. Our kinetic results are based on a self-built high-pressure pulse unit, which allows us to inject selective reversible poisons into the syngas feed passing through a fixed-bed reactor containing an industrial Cu/ZnO/Al 2 O 3 catalyst under high-pressure conditions. This method allows us to perform surface-sensitive operando investigations as a function of the reaction conditions, demonstrating that the rate of methanol formation is only decreased in CO 2-containing syngas mixtures when pulsing NH 3 or methylamines as basic probe molecules.

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The influence of ZnO on the differential heat of adsorption of CO on Cu catalysts: a microcalorimetric study

Cited by 72 publications

References 29 publications

Hydrogenation of CO2 to methanol and CO on Cu/ZnO/Al2O3: Is there a common intermediate or not?

Hydrogenation of CO2 to methanol and CO on Cu/ZnO/Al2O3: Is there a common intermediate or not?

Real‐space observation of strong metal‐support interaction: state‐of‐the‐art and what's the next

Identifying the nature of the active sites in methanol synthesis over Cu/ZnO/Al2O3 catalysts

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