The effect of the thermal pretreatment on the performance of ZnO/Cr 2 O 3 catalysts applied in high-temperature methanol synthesis

Song, Haiyang; Watermann, Clara; Laudenschleger, Daniel; Yang, Fei; Ruland, Holger

doi:10.1016/j.mcat.2017.10.033

Cited by 15 publications

(11 citation statements)

References 41 publications

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“…Calcination at 600 °C significantly reduces the hydrogen consumption associated with the first reduction peak, from 1.37 to 0.46 mmol/g. The consumption of hydrogen by CrZn mixed oxides is generally associated with reduction of Cr(VI) to Cr(III) species. , The Cr(VI) species are typically formed during the calcination of the CrZn hydroxycarbonate precursors (formed in the coprecipitation step) at temperatures lower than 400–500 °C. ,, Increasing the calcination temperature to 600 °C leads to thermal reduction of Cr(VI) to Cr(III) and ultimately to the formation of ZnCr 2 O 4 , explaining the lower hydrogen consumption for catalysts that were calcined at higher temperatures . The presence of crystalline Cr(VI) containing species such as zinc chromate ZnCrO 4 was not observed with XRD, indicating that these phases either are highly dispersed and/or exhibit low crystallinity.…”

Section: Resultsmentioning

confidence: 99%

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

Pollefeyt

Santos

Yancey

et al. 2022

Ind. Eng. Chem. Res.

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A bifunctional catalyst was developed utilizing a physical mixture of a CrZn-based mixed metal oxide and zeotype SAPO-34 for the direct conversion of syngas to short-chain olefins. A series of promoted CrZn-M (M = Fe, Ga, Al) mixed oxide catalysts were synthesized by coprecipitation and calcined at different temperatures. CrZn-Fe-SAPO-34 catalysts calcined at 400 °C selectively converted syngas to C 2 −C 4 olefins, while maintaining high CO conversion and olefin stability over time. The high olefin yield is ascribed to the stabilization effect of iron on inversed spinel phase ZnCr 2 O 4 and to reduction of the detrimental ZnO phase formed during syngas conditions. At a higher calcination temperature of 600 °C, the stabilization effect is less pronounced. Ga and Al-doped CrZn oxides enabled high and stable olefin selectivity of the hybrid catalysts CrZn-Ga-SAPO-34 and CrZn-Al-SAPO-34, regardless the applied calcination temperature. Spectroscopy analysis demonstrated that these promoters are able to scavenge free ZnO formed on the catalyst, thus stabilizing the inversed spinel. This work demonstrates that a rational design of mixed metal oxide components of the hybrid catalyst process is required to maximize olefin yield and catalyst stability. The selection of dopants capable of stabilizing an inversed spinel phase and scavenging detrimental ZnO is a critical step in successful catalyst design.

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Section: Resultsmentioning

confidence: 99%

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

Pollefeyt

Santos

Yancey

et al. 2022

Ind. Eng. Chem. Res.

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“…As XPS results of Cr 2p (Figure a) showed, such valence state variation was accompanied by the obvious appearance of Cr(VI) located at 579.7 eV in ZnCrO x -O 2 . The binding energy of Cr(III) in ZnCrO x -H 2 (577.2 eV) was also slightly higher than ZnCrO x -O 2 (576.4 eV), which may also imply the different electron excited ability . Meanwhile, the binding energy of 1021.9 eV (1021.5 eV) and 1045 eV localized in Zn 2p3/2 and Zn 2p1/2 (SI Figure S3) consisted of Zn 2+ .…”

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confidence: 93%

“…Once calcined, the basal reflections of LDH (Supporting Information (SI), Figure S1) disappeared in an Xray diffraction pattern, while the reflections of ZnO and spinel structure of ZnCr 2 O 4 appeared as shown in Figure 1a. 13,14 ZnCrO x -O 2 consisted of both ZnO and ZnCr 2 O 4 . As displayed in Figure 1d, there was no clear boundary of oxide and support in ZnCrO x -O 2 due to the state of Zn existence as ZnO and nonstoichiometry ZnCr 2 O 4 spinel, in which the Zn atoms occupied the octahedral sites.…”

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confidence: 99%

“…More TEM observation images and diffraction patterns were enclosed as seen in SI Figure S2 It was noted that spinel structure formation could be chromate (ZnCrO 4 ) decomposition at high temperatures and ZnCrO 4 was generated by oxidation of Cr(III) in the presence of ZnO and O 2 . 14,19,20 Hence, oxidative atmosphere during calcination was one of the necessary factors in the formation of chromate and Zn−Cr spinel. The calcined atmosphere changed from oxidative to reductive atmosphere may affect the spinel formation.…”

mentioning

confidence: 99%

“…13 The binding energy of Cr(III) in ZnCrO x -H 2 (577.2 eV) was also slightly higher than ZnCrO x -O 2 (576.4 eV), which may also imply the different electron excited ability. 14 Meanwhile, the binding energy of 1021.9 eV (1021.5 eV) and 1045 eV localized in Zn 2p3/2 and Zn 2p1/2 (SI Figure S3) consisted of Zn 2+ . Previous XPS experiments also demonstrated Cr(III)−Cr(VI) (formed as CrO 4…”

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confidence: 99%

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How CO₂ Chemisorption States Affect Hydrogenation Activity

Yang

Wang

Hua

et al. 2019

Ind. Eng. Chem. Res.

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Carbon dioxide (CO 2 ) activation and then hydrogenation is an alternative route to achieve the efficient control of CO 2 emission. For activation, the neutral CO 2 molecule is first chemisorbed as carboxylate (CO 2 δ− ) or carbonate (CO 3 2− ) on catalysts, which is an important step. Up to now, the relationship elucidation between CO 2 chemisorption states and hydrogenation activity still lacks of direct experimental evidence. Herein, the model Zn−Cr mixed oxide catalysts were created to fulfill the goal. The chemisorption states and hydrogenation mechanism were carefully identified by in situ DRIFTS experiments. Furthermore, additional characterizations demonstrated that CO 2 chemisorption states depended on surface oxygen concentration and species. Combined with the results of CO 2 hydrogenation experiments, the conclusion that chemisorption state as carboxylate was beneficial for higher hydrogenation activity was concluded.

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Cr₂O₃ Promoted In₂O₃ Catalysts for CO₂ Hydrogenation to Methanol

Yang,

Guo,

Zhao

2023

ChemPhysChem

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Cr2O3 was applied to study the modification of In2O3 based catalysts for CO2 hydrogenation to methanol reaction. Combined with X‐ray diffraction (XRD), scanning transmission electron microscopy (STEM), X‐ray photoelectron spectroscopy (XPS), etc., the structure of the catalysts was characterized. The reaction performances for CO2 hydrogenation to methanol were evaluated on a stainless steel fix‐bed reactor. The results showed that solid solutions were formed for the Cr2O3 promoted In2O3 catalysts. The important role of electronic interaction between Cr2O3 and In2O3 was revealed in the hydrogenation reaction. In1.25Cr0.75O3 sample exhibited the highest methanol yield, which was 2.8 times than that of pure In2O3. No deactivation was observed for In1.25Cr0.75O3 sample during the 50 h reaction. The improved catalytic performance may due to the formation of the solid solutions and the highest amount of oxygen vacancies.

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The effect of the thermal pretreatment on the performance of ZnO/Cr 2 O 3 catalysts applied in high-temperature methanol synthesis

Cited by 15 publications

References 41 publications

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

How CO₂ Chemisorption States Affect Hydrogenation Activity

Cr₂O₃ Promoted In₂O₃ Catalysts for CO₂ Hydrogenation to Methanol

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The effect of the thermal pretreatment on the performance of ZnO/Cr 2 O 3 catalysts applied in high-temperature methanol synthesis

Cited by 15 publications

References 41 publications

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

Direct Conversion of Syngas to Olefins over a Hybrid CrZn Mixed Oxide/SAPO-34 Catalyst: Incorporation of Dopants for Increased Olefin Yield Stability

How CO2 Chemisorption States Affect Hydrogenation Activity

Cr2O3 Promoted In2O3 Catalysts for CO2 Hydrogenation to Methanol

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Product

Resources

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How CO₂ Chemisorption States Affect Hydrogenation Activity

Cr₂O₃ Promoted In₂O₃ Catalysts for CO₂ Hydrogenation to Methanol