A mechanism for methanol conversion over HZSM-5 catalyst

1982 ◽  
Vol 35 (12) ◽  
pp. 2483 ◽  
Author(s):  
MB Sayed ◽  
RP Cooney
Keyword(s):  
Gas Phase ◽  
Internal Surface ◽  
Side Reaction ◽  
Methanol Conversion ◽  
Product Formation ◽  
Zeolitic Catalyst ◽  
Side Reactions ◽  
Organic Species ◽  
The Reformation ◽  
Aromatic Product

Mechanistic stages in the conversion of methanol into hydrocarbons, over the zeolitic catalyst HZSM-5, have been studied by means of infrared spectroscopy. Data are reported for both internal surface and gas-phase species. Evidence is presented on the following aspects: the involvement of Lewis sites in the initial dehydration of methanol; the existence of carboxylate side reactions generating CO and CO2; a role for intermediate isobutene; and the reformation of methanol. The extent of the CO2 side reaction appears to correlate with the extent of aromatic product formation. This is interpreted in terms of the involvement of the co-product, hydrogen, in the disproportionation of aromatic products. These observations are embodied in a mechanism invoking both organic species and surface sites for the overall process.

Energetic Control of Redox-Active Polymers Towards Safe Organic Bioelectronic Materials

2019 ◽  
Author(s):  
Alexander Giovannitti ◽  
Reem B. Rashid ◽  
Quentin Thiburce ◽  
Bryan D. Paulsen ◽  
Camila Cendra ◽  
...  
Keyword(s):  
Molecular Oxygen ◽  
Organic Semiconductors ◽  
Side Reaction ◽  
Semiconducting Polymers ◽  
Side Reactions ◽  
Redox Active ◽  
Donor Acceptor ◽  
Electrochemical Devices ◽  
Biological Environment ◽  
Device Operation

<p>Avoiding faradaic side reactions during the operation of electrochemical devices is important to enhance the device stability, to achieve low power consumption, and to prevent the formation of reactive side‑products. This is particularly important for bioelectronic devices which are designed to operate in biological systems. While redox‑active materials based on conducting and semiconducting polymers represent an exciting class of materials for bioelectronic devices, they are susceptible to electrochemical side‑reactions with molecular oxygen during device operation. We show that this electrochemical side reaction yields hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), a reactive side‑product, which may be harmful to the local biological environment and may also accelerate device degradation. We report a design strategy for the development of redox-active organic semiconductors based on donor-acceptor copolymers that prevent the formation of H<sub>2</sub>O<sub>2</sub> during device operation. This study elucidates the previously overlooked side-reactions between redox-active conjugated polymers and molecular oxygen in electrochemical devices for bioelectronics, which is critical for the operation of electrolyte‑gated devices in application-relevant environments.</p>

Gas phase reaction of Cl atoms with a series of oxygenated organic species at 295 K

1988 ◽  
Vol 20 (11) ◽  
pp. 867-875 ◽  
Author(s):  
Timothy J. Wallington ◽  
Loretta M. Skewes ◽  
Walter O. Siegl ◽  
Ching-Hsong Wu ◽  
Steven M. Japar
Keyword(s):  
Gas Phase ◽  
Phase Reaction ◽  
Gas Phase Reaction ◽  
Organic Species ◽  
Cl Atoms

Active site separation of photocatalytic steam reforming of methane using Gas‐Phase Photoelectrochemical system

2021 ◽  
Author(s):  
Tomoki Kujirai ◽  
Akira Yamaguchi ◽  
Takeshi Fujita ◽  
Hideki Abe ◽  
Masahiro Miyauchi
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
High Temperatures ◽  
Steam Reforming ◽  
Active Site ◽  
Side Reaction ◽  
System P ◽  
Steam Reforming Of Methane

Steam reforming of methane (SRM) requires high temperatures to be promoted, and the production of carbon dioxide from the side reaction has also become a problem. In this study, we...

scholarly journals Explicit modeling of volatile organic compounds partitioning in the atmospheric aqueous phase

2013 ◽  
Vol 13 (2) ◽  
pp. 1023-1037 ◽  
Author(s):  
C. Mouchel-Vallon ◽  
P. Bräuer ◽  
M. Camredon ◽  
R. Valorso ◽  
S. Madronich ◽  
...  
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
Water Content ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Water Soluble ◽  
Chemical Mechanism ◽  
Organic Species ◽  
Cloud Water Content ◽  
Isoprene Oxidation

Abstract. The gas phase oxidation of organic species is a multigenerational process involving a large number of secondary compounds. Most secondary organic species are water-soluble multifunctional oxygenated molecules. The fully explicit chemical mechanism GECKO-A (Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere) is used to describe the oxidation of organics in the gas phase and their mass transfer to the aqueous phase. The oxidation of three hydrocarbons of atmospheric interest (isoprene, octane and α-pinene) is investigated for various NOx conditions. The simulated oxidative trajectories are examined in a new two dimensional space defined by the mean oxidation state and the solubility. The amount of dissolved organic matter was found to be very low (yield less than 2% on carbon atom basis) under a water content typical of deliquescent aerosols. For cloud water content, 50% (isoprene oxidation) to 70% (octane oxidation) of the carbon atoms are found in the aqueous phase after the removal of the parent hydrocarbons for low NOx conditions. For high NOx conditions, this ratio is only 5% in the isoprene oxidation case, but remains large for α-pinene and octane oxidation cases (40% and 60%, respectively). Although the model does not yet include chemical reactions in the aqueous phase, much of this dissolved organic matter should be processed in cloud drops and modify both oxidation rates and the speciation of organic species.

scholarly journals Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – reactions of organic species

2005 ◽  
Vol 5 (4) ◽  
pp. 6295-7168 ◽  
Author(s):  
R. Atkinson ◽  
D. L. Baulch ◽  
R. A. Cox ◽  
J. N. Crowley ◽  
R. F. Hampson ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Kinetic Data ◽  
Photochemical Reactions ◽  
Data Evaluation ◽  
Organic Species ◽  
Summary Sheet

Abstract. This article, the second in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Organic species, which were last published in 1999, and were updated on the IUPAC website in late 2002. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and eight appendices containing the data sheets, which provide information upon which the recommendations are made.

scholarly journals Plasma Catalysis: Distinguishing between Thermal and Chemical Effects

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 185 ◽  
Author(s):  
Guido Giammaria ◽  
Gerard van Rooij ◽  
Leon Lefferts
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Thermal Effects ◽  
External Surface ◽  
Plasma Chemistry ◽  
Internal Surface ◽  
Plasma Power ◽  
External Surface Area ◽  
Internal Surface Area ◽  
Chemical Effects

The goal of this study is to develop a method to distinguish between plasma chemistry and thermal effects in a Dielectric Barrier Discharge nonequilibrium plasma containing a packed bed of porous particles. Decomposition of CaCO3 in Ar plasma is used as a model reaction and CaCO3 samples were prepared with different external surface area, via the particle size, as well as with different internal surface area, via pore morphology. Also, the effect of the CO2 in gas phase on the formation of products during plasma enhanced decomposition is measured. The internal surface area is not exposed to plasma and relates to thermal effect only, whereas both plasma and thermal effects occur at the external surface area. Decomposition rates were in our case found to be influenced by internal surface changes only and thermal decomposition is concluded to dominate. This is further supported by the slow response in the CO2 concentration at a timescale of typically 1 minute upon changes in discharge power. The thermal effect is estimated based on the kinetics of the CaCO3 decomposition, resulting in a temperature increase within 80 °C for plasma power from 0 to 6 W. In contrast, CO2 dissociation to CO and O2 is controlled by plasma chemistry as this reaction is thermodynamically impossible without plasma, in agreement with fast response within a few seconds of the CO concentration when changing plasma power. CO forms exclusively via consecutive dissociation of CO2 in the gas phase and not directly from CaCO3. In ongoing work, this methodology is used to distinguish between thermal effects and plasma–chemical effects in more reactive plasma, containing, e.g., H2.

scholarly journals Dehydrogenation of Propane to Propylene Using Promoter-Free Hierarchical Pt/Silicalite-1 Nanosheets

Catalysts ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 174 ◽  
Author(s):  
Wannaruedee Wannapakdee ◽  
Thittaya Yutthalekha ◽  
Pannida Dugkhuntod ◽  
Kamonlatth Rodponthukwaji ◽  
Anawat Thivasasith ◽  
...  
Keyword(s):  
Hierarchical Structures ◽  
Pt Nanoparticles ◽  
Side Reaction ◽  
Diffusion Path ◽  
Side Reactions ◽  
Complete Suppression ◽  
Metal Support Interaction ◽  
Defect Sites ◽  
Propylene Yield ◽  
Propylene Production

Propane dehydrogenation (PDH) is the extensive pathway to produce propylene, which is as a very important chemical building block for the chemical industry. Various catalysts have been developed to increase the propylene yield over recent decades; however, an active site of monometallic Pt nanoparticles prevents them from achieving this, due to the interferences of side-reactions. In this context, we describe the use of promoter-free hierarchical Pt/silicalite-1 nanosheets in the PDH application. The Pt dispersion on weakly acidic supports can be improved due to an increase in the metal-support interaction of ultra-small metal nanoparticles and silanol defect sites of hierarchical structures. This behavior leads to highly selective propylene production, with more than 95% of propylene selectivity, due to the complete suppression of the side catalytic cracking. Moreover, the oligomerization as a side reaction is prevented in the presence of hierarchical structures due to the shortening of the diffusion path length.

Organoaluminium compounds. VII. The reactions of organoaluminium compounds with phenylacetylene

1964 ◽  
Vol 17 (11) ◽  
pp. 1229 ◽  
Author(s):  
T Mole ◽  
JR Surtees
Keyword(s):  
Triple Bond ◽  
Side Reaction ◽  
Similar Process ◽  
Side Reactions ◽  
Crystalline Solids ◽  
Ethereal Solution ◽  
Presence And Absence

The reactions of trimethyl-, triethyl-, tripropyl-, tri-isobutyl-, and triphenylaluminium with phenylacetylene in the presence and absence of benzene or toluene have been studied. In every case phenylethynylaluminium compounds are formed. Dimethyl(phenylethynyl)aluminium and diphenyl(phenylethynyl)aluminium are crystalline solids. The former compound disproportionates partially in ethereal solution. Side reactions competing with the formation of phenylethynylaluminium compounds are also observed. Triethylaluminium and tripropylaluminium add to phenylacetylene to give PhC(AlR2)=CHR (R = Et, Pr), but these alkenylaluminium compounds metallate further phenylacetylene and are so transformed to alkenes. A similar process occurs in the reaction with triphenylaluminium, but in this case both possible products of cis addition are observed. Tri-isobutylaluminium yields phenylethenyl compounds by reduction of the triple bond in the principal side reaction.

Chloroform as an accelerator of propane oxidation

1963 ◽  
Vol 274 (1358) ◽  
pp. 413-426 ◽  
Keyword(s):  
Gas Phase ◽  
Maximum Rate ◽  
Isotopic Exchange ◽  
Pressure Change ◽  
Product Formation ◽  
Pressure Measurements ◽  
Chain Mechanism ◽  
Phase Oxidation ◽  
Gas Phase Oxidation ◽  
Simple Chain

Chloroform and the other chloromethanes, except carbon tetrachloride, accelerate the gas-phase oxidation of propane in the 'low-temperature' region. The relation of pressure change to reactant consumption and final product formation is not significantly modified in the catalyzed reaction, which can still be followed by pressure measurements. The value of the maximum rate in the presence of chloroform is given fairly closely by the expression (( ρ max .) [CHCL 3 ])/( ρ max .) 0 = 1 + constant x [CHCI 3 ]/[ R H]. The form of this suggests that, in the rate-determining steps, chloroform and paraffin are involved in analogous processes, and the key step is postulated to be R O 2 · + CHCI 3 → R OOH + CCl 3 · which re-inforces the reaction R O 2 · + R H → R OOH + R · in competing with those steps normally leading to degradation of R O 2 · radicals. Since little or no isotopic exchange occurs when CDCl 3 is used in place of CHCl 3 , the radical CCl 3 · does not regenerate chloroform, but initiates chains of the type CCl 3 ·→ ·CCl 2 · + Cl·, Cl· + R H → HCl + R · A slow consumption of chloroform (the oxidation of which is unimportant in the absence of propane) occurs, together with a slow build-up of hydrogen chloride. With certain approximations, a simple chain mechanism reproduces the experimental kinetic formula.

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