Relationship between stable monovalent copper in copper–chromia catalysts and activity of methanol formation

Apai, G.; Monnier, John R.; Hanrahan, Michael

doi:10.1039/c39840000212

Cited by 31 publications

(7 citation statements)

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“…As discussed in the Introduction, the active site for methanol synthesis has been debated for decades and opposing results appear in the literature with some studies linearly correlating methanol activity to the amount of metallic Cu 65 and others to the surface Cu + species. 64,66,67 Our results possibly indicate that CO is activated on both Cu 0 and Cu + sites on the surface. This has also been demonstrated recently in a detailed study by Pérez-Ramírez's group, 53 who investigated simultaneously CO hydrogenation, CO 2 hydrogenation, and water-gas shift (WGS) reactions over industrial Cu/Zn/Al catalysts and concluded that CO is converted to methanol over both metallic and partially oxidized copper.…”

Section: View Article Onlinementioning

confidence: 67%

On the Mn promoted synthesis of higher alcohols over Cu derived ternary catalysts

Liakakou

Isaacs

Wilson

et al. 2017

Catal. Sci. Technol.

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Section: View Article Onlinementioning

confidence: 67%

On the Mn promoted synthesis of higher alcohols over Cu derived ternary catalysts

Liakakou

Isaacs

Wilson

et al. 2017

Catal. Sci. Technol.

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“…The issue has been controversially debated for decades; which copper site is the active one in methanol synthesis. Monnier et al 45 found a linear correlation for the amount of Cu + in Cu-Cr 2 O 3 catalysts and their activity for CO hydrogenation. They demonstrated subsequently that this type of catalyst does not exhibit a promotional effect by CO 2 at 543 K and 5.2 MPa like ZnO-containing catalysts.…”

Section: Evolution Of Copper Surface Upon Reactionmentioning

confidence: 99%

New and revisited insights into the promotion of methanol synthesis catalysts by CO2

Martin

Pérez‐Ramírez

2013

Catal. Sci. Technol.

152

136

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CO hydrogenation, CO 2 hydrogenation, and water-gas shift (WGS) reactions have been simultaneously investigated over industry-like catalysts based on Cu-ZnO-Al 2 O 3 , under methanol synthesis conditions (513 K, 5.0 MPa). For this, a novel methodology has been applied: the concentration of carbon dioxide in the syngas feed was consecutively increased (R = CO 2 :(CO + CO 2 ) = 0-100) resulting in a volcano-type plot of the rate of methanol formation and forming a hysteresis loop when decreasing the CO 2 concentration again. H 2 O co-feeding experiments revealed that the enhancement of activity can be correlated with the WGS activity linking both hydrogenation paths of CO and CO 2 . On the other hand, excessive amounts of surface hydroxyls seem to inhibit methanol production, explaining the drop in activity at high CO 2 concentrations. An investigation of the catalytic performance was accompanied by an extensive characterisation of the fresh and used catalytic materials by X-ray diffraction, temperature-programmed reduction by H 2 , N 2 O pulse chemisorption, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. It was shown that the copper surface area affects the CO 2 hydrogenation; however, this parameter is unambiguously not the key descriptor for CO 2 -promoted methanol synthesis, which is a consequence of the synergistic interaction of zinc oxide and copper. This structural feature is further promoted by Al 2 O 3 through stabilisation of the surface.The position of the activity maximum is determined by the surface ratio Cu : Zn. The hysteresis behaviour is a result of the continuous decrease of Cu dispersion and the fixation of copper species in its monovalent oxidation state, both detrimental for CO 2 hydrogenation. CO hydrogenation is strongly affected by the Cu : Zn bulk ratio and thus the reducibility of the catalyst. These facts could be substantiated by the use of impregnated model catalysts.

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“…The Cu+ species had been proposed to be the active components in copper chromite catalyst for hydrogenation reaction. 7 It is known that a very finely dispersed metal is difficult to fully reduce. 31 The increase of hydrogenation activity of copper with the increase of dispersion of copper on Cr203 is also possibly correlated to the high Cu+ concentration in Cu/Cr203 catalysts with smaller copper particles.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the number and frequency of the Raman features depend on the symmetry and the bonding 1 Present address: Catalysis Laboratory, Central Research and Development, The Dow Chemical Company, 1776 Building, Midland, MI 48674. of the transition metal oxide complex and, consequently, can be used to discriminate between alternate molecular structures proposed for a given chemical species. 7 The catalyst systems that have received the most study by LRS are supported vanadium oxide, tungsten oxide, and molybdenum oxide, and a good understanding of the interaction of these oxides with their support oxides has been developed. 5 Of the supported molybdena systems, molybdenum oxide supported on alumina has received the most attention due to its importance as a precursor to the industrial hydrodesulfurization catalyst.…”

Section: Discussionmentioning

confidence: 99%

Carbon monoxide hydrogenation on chromium sesquioxide-promoted copper catalysts

Chen¹,

Lin²

1992

J. Phys. Chem.

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Ids (v 1 0.5 1 .o 1 .s 0 Figure 6. Photocurrent quantum efficiency ( q ) vs plots obtained from the experimental data of Figure 2.the vertical axis gives us a k'\ = 5.0 X and the slope a k12 = 5.0 X cmz cl, very close to k'2 and kN2 values associated with ND values obtained from Mott-Schottky plots.As far as eq 19 and 20 are valid, these results shows that the catalytic activity of Ti203 corundum units associated with oxygen vacancies is characterized by a rate constant for OHo, reaction about 5 orders of magnitude greater than that the characterizing rutile regions free of this kind of lattice defect. ConclusionsWe have shown that the time decay characterizing the photocurrent transients observed during water photoelectrolysis at (001) n-Ti02 rutile in basic medium, and in the absence of surface recombination (high enough band-bending) is very sensitive to the concentration of donor centers ND Under these conditions, the photocurrent-time dependence is due to the surface accumulation of positive holes, the photocurrent-time decay being controlled by rate of generation of (HzOJ, specia from the surface reaction between photogenerated OHo, radicals.'" The experimental observation that the rate constant for (H2Oz)# generation, k2, increases linearly with ND suggests that Ti3+-Vo-Ti3+ lattice defects generated by Ti02 reduction in H2 atmosphere behave as active centers for the photoassisted oxidation of H20 to H20z on the semiconductor surface. The catalytic properties of Ti203 corundum units are attributed to the short distance between adjacent Ti3+ ions (2.59 A), which is considerably smaller than the comsponding Tibc-Tibc distance in the nondefective rutile regions (4.59 A). This assumption is supported by recent calculations of Harding, according to which for 0-0 separations lower than =3.0 A the covalent bonding involved in the formation of H202 peroxo species is found to be the dominant attractive force between two interacting OHo radicals.Acknowledgment. This work was supported by the CICyT, Spain (Project MAT 89-0862-CO3-01). R-try No.The promotion effect of Cr203 on copper catalysts has been studied on Cu/Cr203, Cu/Cr/Si02, and Cu/Si02 catalysts. CO hydrogenation reaction was applied as a probe to test the activity of the catalysts. The activities of Cu/Cr203 catalysts for CO hydrogenation are highly dependent on the variations of the particle size of the supported copper and the temperature of reduction treatments. Cu/Cr/Si02 catalysts have similar behavior as the Cu/Cr203 catalysts. Si02-supportcd copper catalysts are insensitive to the change of pretreatment conditions of the catalysts and the amounts of copper loading on the support. The origin of the promotion ability of Cr203 on copper catalysts was discussed on the basis of an electronic interaction model.

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Relationship between stable monovalent copper in copper–chromia catalysts and activity of methanol formation

Cited by 31 publications

References 1 publication

On the Mn promoted synthesis of higher alcohols over Cu derived ternary catalysts

On the Mn promoted synthesis of higher alcohols over Cu derived ternary catalysts

New and revisited insights into the promotion of methanol synthesis catalysts by CO2

Carbon monoxide hydrogenation on chromium sesquioxide-promoted copper catalysts

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