Chemisorption of N2O and H2 for the Surface Determination of Copper Catalysts

Co-precipitation of CuZn(Al) precursor materials is the traditional way of synthesizing Cu/ZnO/(Al2O3) catalysts for industrial methanol synthesis. This process has been investigated by titration experiments of nitrate and formate solutions. It was found that the solidification of the single components proceeds sequentially in case of nitrates: Cu 2+ is precipitated at pH 3 and Zn 2+ (as well as Al 3+ ) near pH 5. This behavior prevents a homogeneous distribution of all metal species in the initial precipitate upon gradual increase of pH and requires application of the constant pH micro-droplet method. This effect is less pronounced if formate instead of nitrate is used as counter ion. This can be explained by the strong modification of the hydrolysis chemistry of the metal ions due to the presence of formate anions, which act as ligands and buffer. A formate-derived Cu/ZnO/Al2O3 catalyst was more active in methanol synthesis compared to a nitrate-derived sample although the same crystallographic phases were present in the precursor after co-precipitation and ageing. The effect of precipitation temperature was studied for the binary CuZn nitrate model system. Increasing the temperature of co-precipitation above 50 °C leads to down-shift of the precipitation pH of Zn 2+ by a full unit. Thus, in warm solutions more acidic conditions can be used for complete co-precipitation, while in cold solutions, some Zn 2+ may remain dissolved in the mother liquor at the same precipitation pH. The higher limit of temperature is given by the tendency of the initial Cu precipitate towards formation of CuO by oxolation. On the basis of these considerations, the empirically determined optimal pH and temperature conditions of the industrially applied synthesis can be rationalized.

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“…[16]. For fast on-line gas analysis, a calibrated quadrupole mass spectrometer (Pfeiffer Vacuum, Thermostar) was used.…”

Section: Methodsmentioning

confidence: 99%

“…The catalytic activity under steady-state conditions was determined at 220°C and at 10 bar pressure, using a flow rate of 50 N ml min -1 . The copper surface area was determined applying N 2 O reactive frontal chromatography according to the method proposed by Chinchen et al [17] at somewhat more moderate reaction conditions [16].…”

Section: Methodsmentioning

confidence: 99%

Understanding the complexity of a catalyst synthesis: Co-precipitation of mixed Cu,Zn,Al hydroxycarbonate precursors for Cu/ZnO/Al2O3 catalysts investigated by titration experiments

Behrens

Brennecke

Girgsdies

et al. 2011

Applied Catalysis A: General

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“…[51,52]. The catalyst (100 mg) before the test was oxidised in a 30 vol.% O2 in N2 mixture at 350 o C for 30 min, then cooled to 50 o C in the flow of He followed by reduction in a 5 vol.% H2 in N2 mixture for 30 min at 300 o C. After the reduction step, the sample was cooled in a He flow (10 mL min -1 STP) to 30 o C and then the flow was switched to a mixture of CO (500 ppm) and Ar (400 ppm) in He.…”

Section: Characterisationmentioning

confidence: 99%

Hydrogenation of bio-oil into higher alcohols over Ru/Fe3O4-SiO2 catalysts

Cherkasov

Jadvani

Mann

et al. 2017

Fuel Processing Technology

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Permanent WRAP URL:http://wrap.warwick.ac.uk/91922 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP URL' above for details on accessing the published version and note that access may require a subscription. AbstractLiquid-phase hydrogenation of a solution of furfural, phenol and acetic acid has been studied in the 50-235 o C range over magnetic Ru/Fe3O4-SiO2 catalyst targeting the renewable production of second generation biofuels with minimum hydrogen consumption.Phenol was fully hydrogenated to cyclohexanol in the entire temperature range. Below 150 o C, furfural was mainly hydrogenated to tetrahydrofurfuryl alcohol while hydrogenolysis to cyclopentanol was the main reaction pathway above 200 o C. The hydrogenation rate was doubled in an acidic solution (pH=3) as compared to that at a pH 6. The spent catalyst was regenerated and reused in subsequent catalytic runs.

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“…The experiments were performed in quartz micro-reactor at 303 K to avoid subsurface oxidation [29]. Prior to each experiment the catalysts was reduced in 5 vol.% H 2 (He) at 523 K. Subsequently, the reactor was purged for 1 h with He and cooled down to ambient temperature to achieve an adsorbate-free reduced Cu surface.…”

Section: Specific Cu Surface Area Determinationmentioning

confidence: 99%

Microstructural characterization of Cu/ZnO/Al2O3 catalysts for methanol steam reforming—A comparative study

Kurr

Kasatkin

Girgsdies

et al. 2008

Applied Catalysis A: General

113

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Microstructural characteristics of various real Cu/ZnO/Al 2 O 3 catalysts for methanol steam reforming (MSR) were investigated by in situ X-ray diffraction (XRD), in situ X-ray absorption spectroscopy (XAS), temperature programmed reduction (TPR) and electron microscopy (TEM). Structure-activity correlations of binary Cu/ZnO model catalysts were compared to microstructural properties of the ternary catalysts obtained from in situ experiments under MSR conditions. Similar to the binary system, in addition to a high specific copper surface area the catalytic activity of Cu/ZnO/Al 2 O 3 catalysts is determined by defects in the bulk structure. The presence of lattice strain in the copper particles as the result of an advanced Cu-ZnO interface was detected only for the most active Cu/ZnO/Al 2 O 3 catalyst in this study. Complementarily, a highly defect rich nature of both Cu and ZnO has been found in the short-range order structure (XAS). Conventional TPR and TEM investigations confirm a homogeneous microstructure of Cu and ZnO particles with a narrow particle size distribution. Conversely, a heterogeneous microstructure with large copper particles and a pronounced bimodal particle size distribution was identified for the less active catalysts. Apparently, lattice strain in the copper nanoparticles is an indicator for a homogeneous microstructure of superior Cu/ZnO/Al 2 O 3 catalyst for methanol chemistry.

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Chemisorption of N2O and H2 for the Surface Determination of Copper Catalysts

Cited by 106 publications

References 12 publications

Understanding the complexity of a catalyst synthesis: Co-precipitation of mixed Cu,Zn,Al hydroxycarbonate precursors for Cu/ZnO/Al2O3 catalysts investigated by titration experiments

Understanding the complexity of a catalyst synthesis: Co-precipitation of mixed Cu,Zn,Al hydroxycarbonate precursors for Cu/ZnO/Al2O3 catalysts investigated by titration experiments

Hydrogenation of bio-oil into higher alcohols over Ru/Fe3O4-SiO2 catalysts

Microstructural characterization of Cu/ZnO/Al2O3 catalysts for methanol steam reforming—A comparative study

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