scholarly journals Gas-Phase Photocatalytic Oxidation of Dimethylamine: The Reaction Pathway and Kinetics

2007 ◽  
Vol 2007 ◽  
pp. 1-4
Author(s):  
Anna Kachina ◽  
Sergei Preis ◽  
Juha Kallas
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Continuous Flow ◽  
Kinetic Data ◽  
Photocatalytic Oxidation ◽  
Reaction Pathway ◽  
Tubular Reactor ◽  
Order Process ◽  
First Order ◽  
Long Run

Gas-phase photocatalytic oxidation (PCO) and thermal catalytic oxidation (TCO) of dimethylamine (DMA) on titanium dioxide was studied in a continuous flow simple tubular reactor. Volatile PCO products of DMA included ammonia, formamide, carbon dioxide, and water. Ammonia was further oxidized in minor amounts to nitrous oxide and nitrogen dioxide. Effective at 573 K, TCO resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The PCO kinetic data fit well to the monomolecular Langmuir-Hinshelwood model, whereas TCO kinetic behaviour matched the first-order process. No deactivation of the photocatalyst during the multiple long-run experiments was observed.

scholarly journals Gas-Phase and Aqueous Photocatalytic Oxidation of Methylamine: The Reaction Pathways

2007 ◽  
Vol 2007 ◽  
pp. 1-6 ◽  
Author(s):  
Anna Kachina ◽  
Sergei Preis ◽  
German Charles Lluellas ◽  
Juha Kallas
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Continuous Flow ◽  
Photocatalytic Oxidation ◽  
Organic Nitrogen ◽  
Flow Reactor ◽  
Ammonia Nitrogen ◽  
Alkaline Media ◽  
Reaction Pathways ◽  
Continuous Flow Reactor

Photocatalytic oxidation (PCO) of methylamine (MA) on titanium dioxide in aqueous and gaseous phases was studied. A simple batch glass reactor for aqueous PCO and an annular continuous flow reactor for the gas-phase PCO were used. Maximum aqueous PCO efficiency was achieved in alkaline media. Two mechanisms of aqueous PCO—decomposition to formate and ammonia, and oxidation of organic nitrogen directly to nitrite—lead ultimately toCO2, water, ammonia, and nitrate: formate and nitrite were observed as intermediates. A part of the ammonia formed in the reaction was oxidized to nitrite and nitrate. Volatile PCO products of MA included ammonia, nitrogen dioxide(NO2), nitrous oxide(N2O), carbon dioxide, and water. Thermal catalytic oxidation (TCO) resulted in the formation of ammonia, hydrogen cyanide, carbon monoxide, carbon dioxide, and water. The gas-phase PCO kinetics is described by the monomolecular Langmuir-Hinshelwood model. No deactivation ofTiO2catalyst was observed.

Gas-phase pyrolysis of thiopheneacetic acids, thienylethanols, and related compounds — protophilicity of ring π-electrons and relative acidities of hydrogen-bond donors of hydroxyl groups

2002 ◽  
Vol 80 (5) ◽  
pp. 499-503 ◽  
Author(s):  
Ibtehal A Al-Juwaiser ◽  
Nouria A Al-Awadi ◽  
Osman ME El-Dusouqui
Keyword(s):  
Carbon Dioxide ◽  
Hydrogen Bond ◽  
Gas Phase ◽  
Kinetic Data ◽  
Reaction Pathway ◽  
Hydroxyl Groups ◽  
Pyrolysis Kinetics ◽  
Elimination Reactions ◽  
Related Compounds ◽  
Phase Elimination

Based on kinetic data of thermal gas-phase elimination reactions, the following Arrhenius log A (s–1) and Ea (kJ mol–1) values, respectively, are obtained: 10.76 and 153.5 for 3-thiopheneacetic acid (1), 10.08 and 149.4 for 2-thiopheneacetic acid (2), 12.04 and 207.1 for 2-(3-thienyl)ethanol (3), 11.55 and 203.3 for 2-(2-thienyl)ethanol (4), 10.91 and 123.4 for 2-thiopheneglyoxylic acid (5), 11.05 and 223.8 for 1-(2-thienyl)propan-1-one (6), and 10.33 and 149.8 for 3-thiophenemalonic acid (7). The products of these pyrolytic reactions were either carbon dioxide or formaldehyde in addition to methylthiophene or thiophenecarboxaldehyde. Both positional and molecular reactivities of the substrates and related compounds are compared, and the results are rationalized on the basis of a reaction pathway involving a concerted six-membered transition state.Key words: thiophenes, gas-phase, pyrolysis, kinetics, mechanism.

scholarly journals Development of a tubular continuous flow reactor for the investigation of improved gas–solid interaction in photocatalytic CO2 reduction on TiO2

2019 ◽  
Vol 18 (2) ◽  
pp. 314-318 ◽  
Author(s):  
Martin Dilla ◽  
Ahmet E. Becerikli ◽  
Alina Jakubowski ◽  
Robert Schlögl ◽  
Simon Ristig
Keyword(s):  
Gas Phase ◽  
Continuous Flow ◽  
Flow Reactor ◽  
Tubular Reactor ◽  
Co2 Reduction ◽  
Continuous Flow Reactor ◽  
Reactor Geometry

Newly developed tubular reactor geometry allows intensive gas–solid interaction in photocatalytic gas-phase CO2 reduction.

The thermal decompositions of carbamates. I. Ethyl N-Methyl-N-phenylcarbamate

1971 ◽  
Vol 24 (12) ◽  
pp. 2541 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Constants ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
Order Rate

Ethyl N-methyl-N-phenylcarbamate decomposes in the gas phase over the range 329-380� to give N-methylaniline, carbon dioxide, and ethylene. The reaction is quantitative, and is first order in the carbamate. First-order rate constants are described by the equation ������������������� k1 = 1012.44 exp(-45,380/RT) (s-1) and are unaffected by the addition of cyclohexene or by increase in the surface to volume ratio of the reaction vessel. The reaction is considered to be unimolecular and likely to proceed by means of a mechanism of the type represented by the pyrolyses of acetates, xanthates, and carbonates.

Artificial Photosynthesis - Use of a Ferroelectric Photocatalyst

2012 ◽  
Vol 1446 ◽  
Author(s):  
Steve Dunn ◽  
Matt Stock
Keyword(s):  
Carbon Dioxide ◽  
High Pressure ◽  
Titanium Dioxide ◽  
Lithium Niobate ◽  
Gas Phase ◽  
Remnant Polarization ◽  
Artificial Photosynthesis ◽  
Reaction Pathway ◽  
Mercury Lamp ◽  
Low Levels

ABSTRACTThe solid-gas phase photoassisted reduction of carbon dioxide (artificial photosynthesis) was performed using ferroelectric lithium niobate and titanium dioxide as photocatalysts. Illumination with a high pressure mercury lamp and visible sunlight showed lithium niobate achieved unexpectedly high conversion of CO2 to products despite the low levels of band gap light available and outperformed titanium dioxide under the conditions used. The high reaction efficiency of lithium niobate is explained due to its strong remnant polarization (70 μC/cm2) thought to allow longer lifetime of photo induced carriers as well as an alternative reaction pathway.

The thermal decompositions of carbamates. IV. The reactions of isopropyl N,N-dimethylcarbamate and t-butyl N,N-dimethylcarbamate

1980 ◽  
Vol 33 (3) ◽  
pp. 481 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Gas Phase ◽  
Rate Equations ◽  
First Order ◽  
Temperature Range ◽  
Ammonium Carbamate

The thermal decompositions of isopropyl N,N-dimethylcarbamate and t- butyl N,N-dimethylcarbamate are shown to occur over the temperature range 485-602 K through the reactions Me2NCO2Pri → Me2NH+CO2+MeCH=CH2 Me2NCO2But → Me2NH+CO2+Me2C=CH2 which are described as first-order unimolecular processes for which the rate equations are isopropyl k = 1013.04exp(-181209/8.314T) s-1 �t-butyl k = 1012.87exp(-157904/8.314T) s-1 For both carbamates these rate equations describe the rates of formation of the amine and the appropriate alkene but apparently overestimate the rate of carbon dioxide formation. The discrepancy in the carbon dioxide data is explained in terms of the formation of an amine-carbon dioxide adduct during the condensation stage of the analyses. The adduct is described as an ammonium carbamate which undergoes hydrolysis in solution to free the original amine. The existence of transesterification in the gas phase is ruled out.

Thermal decomposition of citraconic anhydride

1971 ◽  
Vol 24 (4) ◽  
pp. 771 ◽  
Author(s):  
NJ Daly ◽  
F Ziolkowski
Keyword(s):  
Carbon Dioxide ◽  
Thermal Decomposition ◽  
Gas Phase ◽  
Rate Constant ◽  
Arrhenius Equation ◽  
Volume Ratio ◽  
Reaction Vessel ◽  
First Order ◽  
First Order Kinetics ◽  
Citraconic Anhydride

Citraconic anhydride decomposes in the gas phase over the range 440- 490� to give carbon dioxide, carbon monoxide, and propyne which undergoes some polymerization to trimethylbenzenes. The decomposition obeys first-order kinetics, and the Arrhenius equation ������������������� k1 = 1015.64 exp(-64233�500/RT) (s-1) describes the variation of rate constant with temperature. The rate constant is unaffected by the addition of isobutene or by increase in the surface/volume ratio of the reaction vessel. The reaction appears to be unimolecular and if a diradical intermediate is involved it may not be fully formed in the transition state.

Gas-Phase Photocatalytic Oxidation of Styrene in a Simple Tubular TiO2 Reactor

2003 ◽  
Vol 6 (2) ◽  
Author(s):  
Marina Krichevskaya ◽  
Sergei Preis
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Gas Phase ◽  
Uv Irradiation ◽  
Photocatalytic Oxidation ◽  
Humid Air ◽  
Oxygenated Hydrocarbons ◽  
Initial Stage ◽  
By Products

AbstractGas-phase photocatalytic oxidation (PCO) of styrene was studied. Styrene appeared to poison the photocatalyst easily degrading its PCO efficiency at concentrations above certain level. Below this level no poisoning of the photocatalyst was observed. The presence of humidity extended the photocatalyst’s lifetime. The yield of carbon dioxide also increased in humid air, although lower conversion degrees of styrene were observed. Carbon dioxide was the main gaseous PCO product; carbon monoxide was formed in trace amounts. The apparent styrene PCO rate was independent of temperature at the initial stage of oxidation. However, the PCO rate noticeably increased with temperature at stages close to complete photocatalyst poisoning. The photocatalyst’s activity was entirely restored by UV -irradiation in humid airflow: adsorbed by-products were successfully oxidised. The simultaneous PCO of styrene with oxygenated hydrocarbons-alcohols and ethers-resulted in the photocatalyst poisoning along the same pattern as for styrene alone.

THE THERMAL DECOMPOSITION OF PHENYLACETIC ACID

1960 ◽  
Vol 38 (8) ◽  
pp. 1261-1270 ◽  
Author(s):  
Margaret H. Back ◽  
A. H. Sehon
Keyword(s):  
Carbon Dioxide ◽  
Activation Energy ◽  
Thermal Decomposition ◽  
Carbon Monoxide ◽  
Rate Constant ◽  
Phenylacetic Acid ◽  
Order Process ◽  
First Order ◽  
Kinetics Of ◽  
Dissociation Step

The thermal decomposition of phenylacetic acid was investigated by the toluene-carrier technique over the temperature range 587 to 722 °C. The products of the pyrolysis were carbon dioxide, carbon monoxide, hydrogen, methane, dibenzyl, and phenylketene. From the kinetics of the decomposition it was concluded that the reaction[Formula: see text]was a homogeneous, first-order process and that the rate constant of this dissociation step was represented by the expression k = 8 × 1012.e−55,000/RT sec−1. The activation energy of this reaction may be identified with D(C6H5CH2—COOH). The possible reactions of carboxyl radicals are discussed.

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