CrO /SiO2 catalysts prepared by metal vapour synthesis: Physical–chemical characterisation and functional testing in oxidative dehydrogenation of propane

Botavina, Maria; Evangelisti, Claudio; Agafonov, Yu. A.; Gaidai, N. A.; Panziera, Nicoletta; Лапидус, А. Л.; Martra, Gianmario

doi:10.1016/j.cej.2010.11.070

Cited by 24 publications

(14 citation statements)

References 39 publications

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“…The volatile organics, such as hydrocarbon, aromatic, and aliphatic, might reduce Cr(VI) through direct reduction and indirect reduction. For direct reduction, the C–H bonds in the organics could easily react with Cr(VI) and subsequently reduce it. , The carbonyl products were formed after C–H bonds reacted with Cr(VI). , In the indirect reduction, the secondary cracking of the volatile organics could form new products, which could react with Cr(VI). For instance, H 2 and CO could form through the dehydrogenation of hydrocarbon , and the cracking of carbonyl products, , respectively.…”

Section: Resultsmentioning

confidence: 99%

“…For direct reduction, the C−H bonds in the organics could easily react with Cr(VI) and subsequently reduce it. 30,31 The carbonyl products were formed after C−H bonds reacted with Cr(VI). 32,33 In the indirect reduction, the secondary cracking of the volatile organics could form new products, which could react with Cr(VI).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Zhang

et al. 2016

Environ. Sci. Technol.

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ABSTRACT:The pyrolysis treatment with biomass is a promising technology for the remediation of chromite-oreprocessing residue (COPR). However, the mechanism of this process is still unclear. In this study, the behavior of pyrolysis reduction of Cr(VI) by cellulose, the main component of biomass, was elucidated. The results showed that the volatile fraction (VF) of cellulose, ie. gas and tar, was responsible for Cr(VI) reduction. All organic compounds, as well as CO and H 2 in VF, potentially reduced Cr(VI). X-ray absorption nearedge structure (XANES) spectroscopy and extended X-ray absorption fine-structure (EXAFS) spectroscopy confirmed the reduction of Cr(VI) to Cr(III) and the formation of amorphous Cr 2 O 3 . The remnant Cr(VI) content in COPR can be reduced below the detection limit (2 mg/kg) by the reduction of COPR particle and extension of reaction time between VF and COPR. This study provided a deep insight on the co-pyrolysis of cellulose with Cr(VI) in COPR and an ideal approach by which to characterize and optimize the pyrolysis treatment for COPR by other organics.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Zhang

et al. 2016

Environ. Sci. Technol.

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“…Dispersion and types of Cr 6+ species in the calcined catalysts are crucial in determining the catalytic performance, and can be generally tuned by pH, ligand effect, and surfactant. Synthetic approaches include (N 0 M n+ )I 0 pathway, 69 metal vapor synthesis method, 70 and sol−gel method. 71 Efforts are also devoted to improving selectivity while preserving activity of CrO x /ZrO 2 catalysts, as they present outstanding C 3 H 8 conversion and C 3 H 6 yield, though CH 4 is dominant (section 3.1.1.2).…”

Section: Oxidative Dehydrogenation Of Propane With Carbon Dioxidementioning

confidence: 99%

“…%. 70 An optimal Cr loading is obtained at 6.0 wt. % (Table 2), at which both C 3 H 8 conversion and C 3 H 6 yield have been substantially increased by ∼1.8and ∼1.7-fold, respectively, in comparison to Cr 0.25 / SiO 2 , while the reduction of C 3 H 6 selectivity is merely 7.3%.…”

Section: Oxidative Dehydrogenation Of Propane With Carbon Dioxidementioning

confidence: 99%

Oxidative Dehydrogenation of Propane to Propylene with Soft Oxidants via Heterogeneous Catalysis

et al. 2021

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Oxidative dehydrogenation of propane to propylene can be achieved using conventional, oxygen-assisted dehydrogenation of propane (O2–ODHP) or via the use of soft oxidants, such as CO2, N2O, S-containing compounds, and halogens/halides. The major roles of soft oxidants include inhibiting overoxidation and improving propylene selectivity, which are considered to be current challenges in O2-assisted dehydrogenation. For both CO2– and N2O–ODHP reactions, significant efforts have been devoted to developing redox-active (e.g., chromium, vanadate, iron, etc.), nonredox-type main group metal oxide (e.g., group IIIA, gallium), and other transition metal/metal oxide catalysts (e.g., molybdenum, palladium platinum, rhodium, ruthenium, etc.), as well as zeolite-based catalysts with adjustable acid–base properties, unique pore structures, and topologies. Metal sulfides have shown promising performance in DHP, whereas the development of suitable catalysts has lagged for SO2- or S-assisted ODHP. Recently, significant efforts have been focused on homogeneous and heterogeneous ODHP using halogens (e.g., Br2, I2, Cl2, etc.) and hydrogen halides (e.g., HCl and HBr) for the development of facile processes for C3H6 synthesis. This Review aims to provide a critical, comprehensive review of recent advances in oxidative dehydrogenation of propane with these soft oxidants, particularly highlighting the current state of understanding of the following factors: (i) relationships between composition, structure, and catalytic performance, (ii) effects of the support, acidity, and promoters, (iii) reaction pathway and mechanistic insights, and (iv) the various roles of soft oxidants. Theoretical and computational insights toward understanding reaction mechanisms and catalyst design principles are also covered. Future research opportunities are discussed in terms of catalyst design and synthesis, deactivation and regeneration, reaction mechanisms, and alternative approaches.

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“…It has been proved that volatile material from biomass pyrolysis, including reducing gases (e.g., CO, CH 4 , and H 2 ) and various molecular-weight tars, is involved in the Cr(VI) pyrolysis reduction. , Undoubtedly, the reducing gases CO, CH 4 , and H 2 can directly reduce Cr(VI). , These gases can be produced following two routes: (1) cracking of biomass components and (2) secondary cracking of large-molecular-weight tar compounds ( m / z > 350) with an aromatic and lignin/carboxylic rich alicyclic molecule (CRAM)-like structures via a decarbonylation reaction . Additionally, small-molecular-weight tar compounds, such as phenols, ketones, and furans, can also directly reduce Cr(VI) .…”

Section: Introductionmentioning

confidence: 99%

Biomass Cellulose Component and Fe Mineral Catalysis Help Cr(VI) to Realize Almost 100% Pyrolysis Reduction Efficiency

2021

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Low-temperature pyrolysis reduction (<500 °C) for Cr(VI) remediation in heavily polluted soil or slag has gained increasing attention. However, it is hard to realize almost 100% Cr(VI) pyrolysis reduction at a high concentration of Cr(VI) pollution (more than 104 mg/kg) due to insufficient reductive pyrolysis products. In the present study, almost 100% Cr(VI) reduction was achieved by cellulose-enriched biomass assisted by an Fe mineral catalysis. Quantitative analysis of tar, reducing gases, and char on the Cr(VI) reduction efficiency suggested that the produced tar is a crucial factor to promote Cr(VI) pyrolysis reduction. Our results indicated that both the cellulose component of biomass and the Fe minerals catalyst could produce susceptible-cracking tar to help Cr(VI) reduction indirectly. FT-ICR MS and online MS results further discerned that produced tar with aromatic and lignin/CRAM-like structures or high unsaturated and oxidized structures (DBE > 15, O x > O6) can be cracked via a decarbonylation reaction to generate reducing gases for promoting Cr(VI) reduction. Thus, our present study provides a method to completely reduce Cr(VI) in solid wastes, perfectly avoiding the reyellowing risk of residual Cr(VI).

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CrO /SiO2 catalysts prepared by metal vapour synthesis: Physical–chemical characterisation and functional testing in oxidative dehydrogenation of propane

Cited by 24 publications

References 39 publications

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Pyrolysis Treatment of Chromite Ore Processing Residue by Biomass: Cellulose Pyrolysis and Cr(VI) Reduction Behavior

Oxidative Dehydrogenation of Propane to Propylene with Soft Oxidants via Heterogeneous Catalysis

Biomass Cellulose Component and Fe Mineral Catalysis Help Cr(VI) to Realize Almost 100% Pyrolysis Reduction Efficiency

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