Relations Between Synthesis and Microstructural Properties of Copper/Zinc Hydroxycarbonates.

Bems, Bettina; Schur, Michael; Dassenoy, Alina; Junkes, Heinz; Herein, Daniel; Schloegl, Robert

doi:10.1002/chin.200332016

Cited by 4 publications

(21 citation statements)

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“…This is because of the fact that the above-mentioned thermal events in this sample are well resolved according to our experiments and the available literature data [11,20]. The Rietveld refinement of XRD patterns indicates that the crystalline content of the material could be considered as a phase-pure aurichalcite.…”

Section: Resultssupporting

confidence: 75%

“…The appearance of each phase depends on the Сu/Zn ratio, with a preference for zincian malachite at Zn contents lower than 30%, two-phase regime at 30 -50% and aurichalcite above 50% [20]. In general, at least two main decomposition steps are involved in the TG decomposition pattern of these mixed hydroxycarbonates with Cu/Zn ratios ranging from 30/70 to 70/30 [11]. The first step (573-673K) is usually attributed to simultaneous evolution of CO 2 and H 2 O, while the high temperature step (673-773K) is exclusively due to the release of CO 2 .…”

Section: Resultsmentioning

confidence: 99%

“…It is also known as anionmodified metal oxide MO (1-y) (CO 3 ) 2y and forms in the first step and decomposes to metal oxide afterwards [10,20]. No such intermediate is observed for the non-mixed malachite and hydrozincite synthetic precursors [11], as well as for malachite minerals 12. It is claimed in [21] that oxygen ions in this structure are substituted by OH -and CO 3 2-groups, although the existence of OH-groups is questionable.…”

Section: Resultsmentioning

confidence: 99%

“…The CRTA technique was used later for careful study of the decomposition mechanism of Cu/Zn hydroxycarbonates with different Cu-toZn ratio [7]. At the same time, the number of publications focusing on the description of the decomposition process and the influence of calcination conditions on the catalytic activity is quite limited [8,9,10,11]. Some studies [12,13] deal with the characterization of binary precursors for Cu/ZnO catalysts, which serve as a suitable model for technical ternary Cu/ZnO/Al 2 O 3 systems.…”

Section: Introductionmentioning

confidence: 99%

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Thermokinetic investigation of binary Cu/Zn hydroxycarbonates as precursors for Cu/ZnO catalysts

et al. 2014

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A combination of thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) coupled to mass spectrometry has been applied to study the thermal decomposition of Cu/Zn hydroxycarbonates, which are used as a precursor for the active methanol synthesis catalyst. Original TG and DSC profiles and results of a formal kinetic analysis of the calcination process are compared with transformations occurring in the solid phase, which has been studied by means of in-situ XRD. A series of hydroxycarbonate precursors with different Cu/Zn molar ratios (40/60, 60/40, 80/20) was synthesized under conditions reported as optimum for catalytic performance. The samples contain primarily two crystalline phases, aurichalcite (Cu,Zn) 5 (CO 3 ) 2 (OH) 6 and zincian malachite (Cu,Zn) 2 CO 3 (OH) 2 . At least four formal decomposition stages of CO 2 and H 2 O evolution cause the major mass loss in the TG experiments. The best-fit quality for the all studied samples was obtained for a four-step competitive reaction model. The experimental TG dependences are adequately described by the n-th order equation and 3D Jander diffusion equation. The effects of the gas flow, sample mass, and water transfer conditions on the reaction pathway were studied. The presence of H 2 O vapor in the reaction feed accelerates the decomposition and dramatically changes the reaction TG profile. The decomposition enthalpy of mixed Cu/Zn (80/20) hydroxycarbonate was determined, and the formation enthalpy of the decomposition intermediate, a carbonate-modified oxide, was calculated to be ΔH f 0 =-633.7±5.6 kJ/mol.

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Section: Resultssupporting

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermokinetic investigation of binary Cu/Zn hydroxycarbonates as precursors for Cu/ZnO catalysts

et al. 2014

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“…Finally, chromium oxide was replaced by aluminum oxide, which has been still adapted in industrial Cu/ZnO/Al2O3 catalysts. Cu/ZnO-based catalyst is usually prepared by coprecipitation method consisting of a series of the steps such as precipitation, ageing, washing, filtering, drying, calcination and reduction as depicted in Figure 1 [21]. The catalyst synthesis starts from the precipitation induced by contacting a basic precipitation agent and a mixed solution of Cu 2+ and Zn…”

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confidence: 99%

Preparation of Active Cu/ZnO-based Catalysts for Methanol Synthesis

Jeong¹,

Suh²

2016

Applied Chemistry for Engineering

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In recent years, methanol has attracted much attention since it can be cleanly manufactured by the combined use of atmospheric CO2 recycling and water splitting via renewable energy. For the concept of "methanol economy", an active methanol synthesis catalyst should be prepared in a sophisticated manner rather than by empirical optimization approach. Even though Cu/ZnO-based catalysts prepared by coprecipitation are well known and have been extensively investigated even for a century, fundamental understanding on the precipitation chemistry and catalyst nanostructure has recently been achieved due to complexity of the necessary preparation steps such as precipitation, ageing, filtering, washing, drying, calcination and reduction. Herein we review the recent reports regarding the effects of various synthesis variables in each step on the physicochemical properties of materials in precursor, calcined and reduced states. The relationship between these characteristics and the catalytic performance will also be discussed because many variables in each step strongly influence the final catalytic activity, called "chemical memory". All discussion focuses on how to prepare a highly active Cu/ZnO-based catalyst for methanol synthesis. Furthermore, the preparation strategy we deliver here would be utilized for designing other coprecipitation-derived supported metal or metal oxide catalysts.

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The effect of mixing on Co‐precipitation and evolution of microstructure of Cu‐ZnO catalyst

et al. 2018

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The influence of feeding point in conventional stirred tank reactor and flow characteristics in micro‐reactor on the microstructure of Cu‐ZnO catalyst was studied. Cu‐Zn distribution in co‐precipitate was characterized by EDS and Zn fraction in zincian malachite was estimated from the 20 true1¯ peak shift in XRD pattern. The theory analysis and experimental results, combining with measurement of segregation index, show that the contact pattern and mixing of reactants in precipitation process determine the uniformity of Cu‐Zn distribution in initial co‐precipitates at the micro‐scale. The uniform Cu‐Zn distribution is favorable for the formation of zincian malachite with higher Zn fraction, whereas the uneven distribution could lead to either zincian malachite with lower Zn fraction or aurichalcite‐like nonmalachite. These differences in the precursor structure act on subsequent calcination and reduction, as well as their products. Along this path, mixing affects the evolution of the catalyst microstructure by means of Cu‐Zn distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2647–2654, 2018

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Relations Between Synthesis and Microstructural Properties of Copper/Zinc Hydroxycarbonates.

Abstract: For Abstract see ChemInform Abstract in Full Text.

Cited by 4 publications

References 1 publication

Thermokinetic investigation of binary Cu/Zn hydroxycarbonates as precursors for Cu/ZnO catalysts

Thermokinetic investigation of binary Cu/Zn hydroxycarbonates as precursors for Cu/ZnO catalysts

Preparation of Active Cu/ZnO-based Catalysts for Methanol Synthesis

The effect of mixing on Co‐precipitation and evolution of microstructure of Cu‐ZnO catalyst

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