Oxidation Of Propyne Research Articles

An experimental and detailed kinetic modeling study of the pyrolysis and oxidation of allene and propyne over a wide range of conditions

Allene and propyne are important intermediates in the pyrolysis and oxidation of higher hydrocarbon fuels, and they are also a major source of propargyl radical formation, which can recombine into different C6H6 isomers and finally produce soot. In a prior work (Panigrahy et al., “A comprehensive experimental and improved kinetic modeling study on the pyrolysis and oxidation of propyne”, Proc. Combust. Inst 38 (2021)), the pyrolysis, ignition , and laminar flame speed of propyne were investigated. To understand the kinetic features of initial fuel breakdown and oxidation of the two C3H4 isomers, new measurements for allene pyrolysis and oxidation are conducted in the present paper at the same operating conditions as those studied previously for propyne. Ignition delay times of allene are measured using a high-pressure shock tube and a heated twin-opposed piston rapid compression machine in the temperature range 690–1450 K at equivalence ratios of 0.5, 1.0 and 2.0 in ‘air’, and at pressures of 10 and 30 bar. Pyrolysis species measurements of allene and propyne are also performed using a gas chromatography integrated single-pulse shock tube in the temperature range 1000–1700 K at pressure of 2 and 5 bar. Furthermore, laminar flame speeds of allene are measured at elevated gas temperatures of 373 K at pressures of 1 and 2 bar for a wide range of equivalence ratios from 0.6 to 1.5. A newly updated kinetic mechanism developed for this study is the first model that can well reproduce all of the experimental results for both allene and propyne. It is observed that in the pyrolysis process, allene dissociates faster than propyne. Both isomers exhibit similar ignition delay times at high temperatures (>1000 K), while, at intermediate temperatures (770–1000 K) propyne is the faster to ignite, and at lower temperatures (< 770 K) allene becomes more reactive. Furthermore, laminar flame speeds for propyne are found to be slightly faster than those for allene under the conditions studied in this work.

A comprehensive experimental and improved kinetic modeling study on the pyrolysis and oxidation of propyne

To improve our understanding of the combustion characteristics of propyne, new experimental data for ignition delay times (IDTs), pyrolysis speciation profiles and flame speed measurements are presented in this study. IDTs for propyne ignition were obtained at equivalence ratios of 0.5, 1.0, and 2.0 in ‘air’ at pressures of 10 and 30 bar, over a wide range of temperatures (690–1460 K) using a rapid compression machine and a high-pressure shock tube. Moreover, experiments were performed in a single-pulse shock tube to study propyne pyrolysis at 2 bar pressure and in the temperature range 1000–1600 K. In addition, laminar flame speeds of propyne were studied at an unburned gas temperature of 373 K and at 1 and 2 bar for a range of equivalence ratios. A detailed chemical kinetic model is provided to describe the pyrolytic and combustion characteristics of propyne across this wide-ranging set of experimental data. This new mechanism shows significant improvements in the predictions for the IDTs, fuel pyrolysis and flame speeds for propyne compared to AramcoMech3.0. The improvement in fuel reactivity predictions in the new mechanism is due to the inclusion of the propyne + HȮ2 reaction system along with ȮH radical addition to the triple bonds of propyne and subsequent reactions.

Oxidation of phenyl propyne catalyzed by copper(II) complexes of a benzimidazolyl schiff base ligand: Effect of acid/base, oxidant, surfactant and morphology

Copper(II) complexes with a new N-Substituted benzimidazolyl schiff base ligand are used as catalyst for the oxidation of 1-phenyl propyne. The oxidation is carried out under mild conditions using stoichiometric amounts of oxidant and catalytic amounts of Cu(II) complex as catalyst. Effect of acid/base, oxidant, morphology and surfactant has been studied. Two major products of phenyl propyne oxidation are the α-diketonic product and a terminal aldehyde. Diketone is the major product under acidic conditions while aldehyde formation is highest under basic conditions. The maximum conversion is found with the NO3− bound complex. GC–MS is used to find the percentage yields of products. SEM and PXRD of the reused complexes as catalyst suggest that morphology affects the catalytic efficiency.

Comparisons of propylene and propyne catalytic oxidation on a 100 Å Pt/Al 2O 3 thin film using in situ soft X-ray fluorescence methods

Propyne and propylene deep oxidation to form CO 2 and H 2O in flowing oxygen pressures up to 0.01 Torr has been studied on a 100 Å Pt/Al 2O 3 thin film catalyst using a combination of synchrotron based soft X-ray techniques. In situ temperature-programmed and isothermal kinetic experiments have been used to evaluate reaction mechanisms and energetics. Propyne oxidation on the thin film occurs in a simple, one-step process with a C 3H 4 (propyne) intermediate. Propylene oxidation on this surface is more complex. Initial propylene desorption and oxydehydrogenation results in the formation of a C 3H 5 intermediate (1-methylvinyl). Skeletal oxidation begins with increasing temperature and additional oxydehydrogenation results in the formation of a C 3H 4 propyne-like intermediate. Thus, as observed previously on the Pt(1 1 1) surface, skeletal oxidation of both propyne and propylene above 370 K proceeds through a C 3H 4 intermediate. Even for this complex, supported Pt thin film sample, the oxidation mechanisms for propyne and propylene remain stable over the entire range of oxygen pressures studied. The propyne and propylene oxidation temperatures on the Pt film are quite similar to the Pt(1 1 1) surface. Propyne adsorbs on the 100 Å Pt/Al 2O 3 thin film through the π system nearly parallel to the surface, in a manner very similar to the Pt(1 1 1) surface. However, molecular adsorption of propylene on the Pt film surface is more complex. A new weakly adsorbed bonding mode is observed on the Pt film in addition to a strongly adsorbed form similar to propylene bonding on the Pt(1 1 1) surface. This weakly bound species desorbs between 200 and 270 K, while the more tightly bound propylene species that remains on the surface undergoes oxydehydrogenation and skeletal oxidation as outlined above.

An experimental and kinetic modeling study of propyne oxidation

The oxidation of propyne was studied experimentally in an atmospheric-pressure flow reactor and in laminar premixed flames. Species profiles were obtained for propyne oxidation experiments conducted in the Princeton turbulent flow reactor (PTFR) in the intermediate- to high-temperature range (∼1170 K) for lean, stoichiometric, and rich conditions. Laminar flame speeds of propyne/(18% O 2 in N 2 ) mixtures were determined, over an extensive range of equivalence ratios, at room temperature and atmospheric pressure, using the counterflow twin flame configuration. A detailed chemical kinetic model of high-temperature propyne oxidation, consisting of 437 reactions and 69 species, was developed. It is shown that this kinetic model predicts reasonably well the flow-reactor and flame-speed data determined in this study and the shock tube ignition data available in the literature. The remaining uncertainties in the reaction kinetics of propyne oxidation are discussed.

Propyne Oxidation: A Kinetic Modeling Study

Abstract Propyne oxidation was modeled using a comprehensive kinetic reaction mechanism including the most recent findings concerning the kinetics of the reactions involved in the oxidation of propyne. The proposed mechanism is able to reproduce experimental data obtained in our high-pressure jet stirred reactor and in shock tube in the pressure range 1-13 atm, for temperatures extending from 950 to 2000 K and equivalence ratios 0.5 to 2. The proposed propyne oxidation mechanism is able to correctly reproduce ignition delay times measured in shock tube and molecular species concentrations measured in our jet stirred reactor.

Allene oxidation in jet-stirred reactor : a kinetic modeling study

Allene oxidation was modeled using a comprehensive kinetic reaction mechanism including the most recent findings concerning the kinetics of the reactions involved in the oxidation of allene. The proposed mechanism is able to reproduce experimental data (molecular species concentration profiles) obtained in our jet stirred reactor at 1 atm, for temperatures extending from 1030 to 1070K and equivalence ratios of 0.2 to 2. The proposed oxidation mechanism is also able to correctly reproduce ignition delay times measured in shock tube and molecular species concentrations measured in our jet stirred reactor for the oxidation of propyne.

Kinetics of the Ignition of Fuels in Artificial Air Mixtures. II: Oxidation of Propyne

Abstract Shock tube measurements of the ignition delay times of propyne-oxygen-nitrogen and propyne-oxygen-argon mixtures are presented. Temperatures in the range of 1125-2000 K are achieved and the reflected pressure varies from 4 to 13 atmospheres. The measured delay times are well correlated by the following overall kinetic equation The reaction mechanism for propyne-oxygen-nitrogen and propyne-oxygen-argon mixtures is investigated numerically using the routines LSODE and CHEMEQ. This investigation resulted in a kinetic scheme of 68 reactions among 26 species. The agreement between the measured ignition delay times and the numerical calculations is mixed. An overall ignition delay time correlation deduced from the numerical predictions is more similar to experimentally obtained correlations for propane and propene than for propyne. For some of the experimental conditions, a detonation-like pattern is observed after ignition. This phenomenon is investigated by comparing the measurements with calculated ...

INFRARED STUDY OF INTERMEDIATES IN PROPYNE OXIDATION ON ZnO USING [18O2]OXYGEN AND DINITROGEN OXIDE

Abstract The oxidation of propyne on ZnO by 18O2 and N2O has been studied by IR spectroscopy. The lattice oxygen participates in the formation of diketone-like species and that adsorbed oxygen forms ketene-like species. No formate species is formed in the oxidation by N2O.

The competitive oxidation of acetylene and propyne

The competitive oxidation of acetylene and propyne between 280 and 330° has shown that σ-radicals, produced by the reaction of chain-propagating radicals with acetylene, abstract a proton from propyne rather than add oxygen, and that branching in propyne oxidation proceeds through addition of the chain-propagating radicals to propyne.