Distinguishing between reaction intermediates and spectators: A kinetic study of acetone oxidation using ozone on a silica-supported manganese oxide catalyst

Reed, Corey; Xi, Yan; Oyama, S. Ted

doi:10.1016/j.jcat.2005.08.014

Cited by 99 publications

(61 citation statements)

References 15 publications

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“…The elementary steps involved for both mechanisms are presented in Table 3. For the L-H s mechanism, the proposed steps by Oyama et al [10] as well as Rezaei and Soltan [24] were fully adopted and listed in the left of Table 3. Briefly, the L-H s mechanism consists of two cycles: ozone decomposition, as shown in steps (1) to (3), and toluene equilibrated adsorption [step (4)], migration [step (5)], and activation [step (6)], which are involved in one another.…”

Section: L-h Kinetic Model Developmentmentioning

confidence: 99%

“…Other than the recent study by Rezaei and Soltan [24], no studies were performed to test the validity of the L-H s mechanism on the catalytic ozonation of toluene over alumina-supported manganese oxide catalysts. The toluene activation step in this model differs from that proposed by Oyama et al [10]. Moreover, the model was established based on the assumption that toluene is activated by extracting hydrogen from the methyl group of toluene, and C-H bond cleavage is the relevant kinetic step for catalytic ozonation of toluene.…”

Section: Introductionmentioning

confidence: 99%

“…Catalytic ozonation is a promising approach used to degrade VOCs [5][6][7][8][9]. The catalytic ozonation of VOCs is considered a surface reaction, which follows the Langmuir-Hinshelwood mechanism and comprises adsorbed VOC molecules and atomic oxygen species; this process was originally proposed by Oyama et al [10] to investigate the kinetics and mechanism of the catalytic ozonation of acetone over MnO x /SiO 2 by combining in situ Raman spectroscopy with transient kinetics techniques. To the best of our knowledge, Oyama et al study is the only systematic study on the kinetics and mechanism of the catalytic ozonation of VOCs, which has been widely used to explain the experimental results of the catalytic ozonation of several VOCs, such as toluene [11,12], propanol [13], benzene [14], and cyclohexane [15].…”

Section: Introductionmentioning

confidence: 99%

“…To the best of our knowledge, Oyama et al study is the only systematic study on the kinetics and mechanism of the catalytic ozonation of VOCs, which has been widely used to explain the experimental results of the catalytic ozonation of several VOCs, such as toluene [11,12], propanol [13], benzene [14], and cyclohexane [15]. Moreover, the Langmuir-Hinshelwood dual-site (L-H d ) mechanism was proposed to explain the elementary steps involved in the reaction [10], in which the SiO 2 support was applied for acetone adsorption, whereas ozone was adsorbed on MnO x . However, only one site (MnO x ) was involved in the derivation of the proposed kinetic model; thus, the derived kinetic equation was actually based on the Langmuir-Hinshelwood single-site (denoted as L-H s ) mechanism.…”

Section: Introductionmentioning

confidence: 99%

“…Two models [10,24] were developed based on the L-H s mechanism, in which surface reactions occurred only on active metal oxide sites. Supports, such as SiO 2 and alumina, served as platforms for active site dispersion, which were meaningless from the kinetic point of view of rate expression development.…”

Section: Introductionmentioning

confidence: 99%

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Novel mechanistic view of catalytic ozonation of gaseous toluene by dual-site kinetic modelling

Yao

Hui

et al. 2017

Chemical Engineering Journal

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe catalytic ozonation of VOCs is a promising approach for degradation of indoor VOCs, such as gaseous toluene. However, the mechanism and relevant kinetic steps involved in this reaction remain unclear. In this study, the catalytic ozonation of toluene over MnO 2 /graphene was investigated using the empirical power law model and classic Langmuir-Hinshelwood single-site (denoted as L-H s ) mechanism. The apparent activation energy determined using the power law model was 29.3±2.5 kJ mol −1 . This finding indicated that the catalytic ozonation of toluene over MnO 2 /graphene was a heterogeneous reaction, and the Langmuir-Hinshelwood mechanism was applicable. However, the L-H s mechanism did not fit the experimental data, suggesting that the reaction was non-single-site governed. A novel Langmuir-Hinshelwood dual-site (denoted as L-H d ) mechanism was then proposed to explain the experimental observations of the catalytic ozonation of toluene over MnO 2 /graphene through a steady-state kinetic study. This mechanism was based on the hypothesis that MnO 2 was responsible for ozone decomposition and toluene adsorption on graphene; these two types of adsorption were coupled by an adjacent attack. Furthermore, XPS results confirmed the presence of a strong connection between MnO 2 and graphene sites on the surface of MnO 2 /graphene. This connection allowed the adjacent attack and validated the dual-site mechanism. The L-H d model was consistent with the predicted reaction rate of toluene removal with a correlation coefficient near unity (r 2 = 0.9165). Moreover, the physical criterion was in accordance with both enthalpy and entropy of toluene adsorption constraints. Fulfillment of mathematical and physical criteria indicated the catalytic ozonation of toluene over MnO 2 /graphene can be well described by the L-H d mechanism. This study helps understand the catalytic ozonation of toluene over MnO 2 /graphene in a closely mechanistic view.

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Section: L-h Kinetic Model Developmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Novel mechanistic view of catalytic ozonation of gaseous toluene by dual-site kinetic modelling

Yao

Hui

et al. 2017

Chemical Engineering Journal

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Catalytic Materials for Low Concentration VOCs Removal through “Storage‐Regeneration” Cycling

Chen

et al. 2019

ChemCatChem

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Compared with other approaches for the removal of VOCs, the concept of “storage‐regeneration” cycling is proposed as an effective and promising way to eliminate low‐concentration indoor VOCs. A key issue in this approach is the design of catalytic materials which should possess balanced properties between storage and regeneration. The materials used for the storage of VOCs such as formaldehyde and benzene should not only possess high and selective VOC storage capacity, but also be easily regenerated without any release of the VOCs or generation of secondary pollutants. To this end, appropriate regeneration methods have been proposed, including thermal regeneration, plasma (nonthermal plasma) oxidation or ozone enabled regeneration. In this short review, these essential features of the cycled “storage‐regeneration” concept for VOC destruction are considered and the prospects for the implementation of this technology are assessed.

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Experimental methods in chemical engineering: Raman spectroscopy

2020

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When photons impinge on a substrate, most scatter with the same frequency (elastic scattering or Rayleigh dispersion) and only 10 −7 scatter with a different energy (inelastic scattering). This inelastic interaction (Raman scattering) exchanges energy in the region of molecular vibrational transitions for crystalline and amorphous materials. Raman bands in a spectra represent vibrational transitions, like infrared, however the selection rules are different. Typically, the vibrations that are intense in Raman are weak in infrared and vice versa. A remarkable feature of the Raman effect is that it is highly sensitive to nanocrystals, even below 4 nm, which are too small to generate XRD patterns. Plasmonic enhancement, like surface-enhanced Raman spectroscopy (SERS) boost the Raman signal by 10 4 , providing single-molecule detection capability. Glass, quartz, and sapphire are transparent to Raman effect (depending on the energy of the incident excitation radiation), which makes it ideal to examine materials under reaction conditions (in-situ cells and operando reactors that operate over a broad range of temperature, pressures, and environments). Raman spectroscopy emerged in the 1930s; however, infrared spectrometry displaced it. With the advent of powerful lasers in the 1970s, more researchers began to apply Raman routinely. In 2019, the Web of Science indexed 20 400 articles mentioning Raman against 50 000 articles mentioning infrared. Chemical engineers apply Raman less frequently than in material science, physical chemistry, and applied physics, with 887 articles vs 6250, 3700, and 3510 for the other disciplines. A bibliometric analysis identified four research clusters centred on thin films and optics, graphene and nanocomposites, nanoparticles and SERS, and photocatalyst. K E Y W O R D S operando, Raman, Rayleigh, Stokes bands, surface enhanced Raman spectroscopy 1 | INTRODUCTION Raman spectroscopy has become an important and popular analytical tool since it is non-destructive and identifies molecular structure properties and how they change under reactive environments. The technique is based on the Raman effect that C.V. Raman described in 1928 [1] : when electromagnetic radiation (typically monochromatic laser light; near ultraviolet, visible, or near infrared) interacts with a materials molecular vibrations, the incident energy of the photons are scattered with a predominantly lower energy (inelastic scattering). However,

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Distinguishing between reaction intermediates and spectators: A kinetic study of acetone oxidation using ozone on a silica-supported manganese oxide catalyst

Cited by 99 publications

References 15 publications

Novel mechanistic view of catalytic ozonation of gaseous toluene by dual-site kinetic modelling

Novel mechanistic view of catalytic ozonation of gaseous toluene by dual-site kinetic modelling

Catalytic Materials for Low Concentration VOCs Removal through “Storage‐Regeneration” Cycling

Experimental methods in chemical engineering: Raman spectroscopy

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