Structure and reactivity of Zn-Cr mixed oxides. Role of non-stoichiometry in the catalytic synthesis of methanol

Errani, E.; Trifirò, Ferruccio; Vaccari, Angelo; Richter, M.; Piero, G. Del

doi:10.1007/bf00765056

Cited by 42 publications

(20 citation statements)

References 14 publications

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“…E. Errani et al. stated that superabundant ZnO in catalyst is harmful for CO conversion . This is agreement with our results that Zn 2 Cr 1 shows relatively lower CO conversion and selectivity of lower olefins compared to Zn 1 Cr 1 .…”

Section: Resultssupporting

confidence: 93%

“…E. Errani et al stated that superabundant ZnO in catalyst is harmful for CO conversion. [26] This is agreement with our results that Zn 2 Cr 1 shows relatively lower CO conversion and selectivity of lower olefins compared to Zn 1 Cr 1 . The broad peak at 31.8°in Zn 1 Cr 1 could be considered as a shoulder of the ZnCr 2 O 4 spinel peak at 30.3°, implying an interaction between ZnO and ZnCr 2 O 4 phases and not mutual independence.…”

Section: Resultssupporting

confidence: 93%

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Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr₂O₄ Interface

et al. 2020

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This work reports that the ZnO−ZnCr2O4 interface was constructed by tailoring the Zn/Cr ratio and the role of ZnO−ZnCr2O4 interface in activating CO molecule for the synthesis of lower olefins over a tandem catalyst was studied. A lower olefins selectivity of 71 % at a CO conversion of 34 % was achieving on Zn1Cr1&SAPO‐34. The presence of ZnO−ZnCr2O4 interface effectively reduces the activation energy of CO hydrogenation (from 51.8 kJ/mol to 33.6 kJ/mol) and subsequently leading to the triple increase of intrinsic activity. In situ DRIFTS and XPS studies demonstrate that the better catalytic activities of Zn1Cr1 catalyst are related to the presence of ZnO−ZnCr2O4 interface, which provides more oxygen vacancy sites for CO adsorption and activation. In this sense, the Zn1Cr1 catalyst with ZnO−ZnCr2O4 interface is more active than the simple physical mixture of ZnO and Cr2O3 catalyst separately and Zn1Cr2 catalyst. This work provides fundamental insights for a rational design of Zn−Cr based catalysts and even other heterogeneous catalysts by constructing oxide‐oxide interface.

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Section: Resultssupporting

confidence: 93%

Section: Resultssupporting

confidence: 93%

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr₂O₄ Interface

et al. 2020

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“…Spinels are ternary oxides with the general formula AB 2 O 4 , where A and B are cations occupying tetrahedral and octahedral sites respectively. These oxides exhibit interesting electric, magnetic and catalytic properties [1][2][3][4] , depending on their nature, charge, and distribution of ions at interstices 5 . CuCr 2 O 4 crystallizes as a tetragonally distorted spinel structure.…”

Section: Introductionmentioning

confidence: 99%

Pechini synthesis and microstructure of nickel-doped copper chromites

et al. 2005

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Spinel-type solid solutions were synthesized by the Pechini method and calcined between 500 and 900 °C for 4 hours and at 900 °C for 8 hours to produce ceramic pigments. The resulting powders were characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis and BET surface area measurements. The formation of spinel took place upon calcination at 700 °C. IR spectroscopy revealed the presence of n1 and n2 bands, typical of spinel structures, broadened by the presence of more than one cationic species in the structure. The specific area of the resulting powder decreased from 24.7 to 1.4 m² g-1 as the calcination temperature increased from 700 to 900 °C. Microstructural analyses revealed the presence of crystalline spinel as the only phase present in powders calcined at 900 °C. Colorimetric analyses using L*a*b* coordinates and UV-visible spectroscopy revealed that the pigment was predominantly black

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“…Erranni pointed out that the presence of surface octahedral zinc ions, i.e. located in the non-stoichiometric spinels, is crucial for high activity of catalysts in methanol synthesis [29]. He suggested that such sites are responsible for heterolytic dissociative adsorption of hydrogen.…”

Section: Phase Compositionmentioning

confidence: 99%

Chromium-modified zinc oxides

Gac

Zawadzki

Słowik

et al. 2016

J Therm Anal Calorim

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Zinc oxides modified with chromium were prepared by the co-precipitation method. Samples were calcined at 400°C. Structural and surface properties of materials were studied by means of transmission electron microscopy, X-ray diffraction and low-temperature nitrogen adsorption methods. Temperature-programmed reduction methods were used for investigation of the influence of chromium on the redox properties of zinc oxides. The nature of surface sites and the course of surface reactions occurred during methanol decomposition were determined by the temperature-programmed desorption of methanol with detection of evolved gasses by mass spectrometry and in situ diffuse reflectance infrared Fourier transform spectroscopy. We have found that modification of ZnO with chromium led to the increase of the specific surface area of oxides and decrease of mean crystallite size of ZnO. Partial incorporation of chromium ions to the hexagonal ZnO structure, formation of strongly dispersed spinel (ZnCr 2 O 4 ) and chromium zinc oxide species (ZnOÁCrO 3 ) was observed. We have stated that methanol was adsorbed on the surface of ZnO at 100°C mainly via formation of methoxy species, and the main products of methanol desorption were carbon monoxide and hydrogen. The presence of chromium facilitated direct oxidation of methoxy groups to formate species at low temperatures (*100°C) and their transformation to hydrogen and carbon dioxide during temperature-programmed desorption. The enhanced transformation of methoxy to formate species was attributed to the labile oxygen in chromium-modified zinc oxides.

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Structure and reactivity of Zn-Cr mixed oxides. Role of non-stoichiometry in the catalytic synthesis of methanol

Cited by 42 publications

References 14 publications

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr₂O₄ Interface

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr₂O₄ Interface

Pechini synthesis and microstructure of nickel-doped copper chromites

Chromium-modified zinc oxides

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Structure and reactivity of Zn-Cr mixed oxides. Role of non-stoichiometry in the catalytic synthesis of methanol

Cited by 42 publications

References 14 publications

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr2O4 Interface

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr2O4 Interface

Pechini synthesis and microstructure of nickel-doped copper chromites

Chromium-modified zinc oxides

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Product

Resources

About

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr₂O₄ Interface

Synthesis Gas Conversion to Lower Olefins over ZnCr‐SAPO‐34 Catalysts: Role of ZnO−ZnCr₂O₄ Interface