Photolysis Of Ethane Research Articles

Velocity map imaging studies of the Lyman α photodissociation mechanism for H atom production from hydrocarbons

H atoms produced in Lyman α photolysis of ethane, propane, and ethylene have been studied using velocity map imaging techniques. Two types of H atoms are identified, one formed along with an alkyl radical in the Rydberg state and the other by the subsequent decomposition of this Rydberg radical.

Primary processes in the photolysis of propane: the use of HI as a radical scavenger

The photolysis of C 3D 8 has been investigated with 8.4, 10.0, and 11.6–11.8 eV photons, using HI to scavenge the radicals through the reaction: R D + HI → R DH + I (where R D is a fully deuterated alkyl or alkenyl radical). Comparison of the results with the results of analogous experiments using H 2S as a scavenger leads to the conclusion that HI is a more efficient radical scavenger than H 2S. The results are discussed with particular emphasis on determining whether the primary processes include direct C C and C H bond cleavage. An examination of the effects of HI concentration, conversion, and pressure on the yield of ethyl radicals intercepted indicates that the ethyl radicals are formed in the primary process: C 3D 8* → C 2D 5 + CD 3. It is noted that the relative importances of this process and the other primary processes involving breaking of the C C bond (C 3D 8* → CD 4 + C 2D 4 and C 3D 8* → C 2D 6 + CD 2) do not change with energy, and it is thus suggested that they all occur from an excitation in the C C bond, and that RRKM considerations relating to equipartition of energy are not applicable to the dissociations of electronically excited alkanes. It is pointed out that, as in the photolysis of ethane, the dissociation leading to the formation of a molecule of hydrogen (deuterium) (C 3D 8* → D 2 + C 3D 6), which apparently occurs as a result of an excitation in a C H (C D) bond, predominates in the 8.4 eV photolysis, but diminishes sharply in importance with respect to the C C bond cleavage processes when the energy is increased. The insertion of methylene into a primary C H bond of C 3H 8 to give n-butane is examined, and information concerning the internal energy of the CH 2 species is derived and discussed in terms of the primary dissociation of propane.

Photolysis of Ethane at 11.6–11.8 eV

The photolysis of ethane, carried out with an argon resonance lamp, has been reinvestigated with the related purposes of (1) measuring quantum yields of all fragments formed in the dissociation of excited ethane and (2) associating these fragments with the primary processes occurring in the photolysis of ethane. These and their relative abundances are C2H6*→C2H6+, 5% →CH4+CH2, 16% →C2H5+H, 41% →C2H4+H2, 26% →CH3+CH3, 15%. These results are compared with conclusions reached in earlier studies on the photolysis of ethane with xenon and krypton lamps in order to determine the effect of energy on the relative probabilities of the primary processes. It is found that direct bond scission increases in importance with increasing energy, while processes involving rearrangement decrease in importance. The radical and molecular fragments formed in the dissociation of excited ethane were determined by (a) analyzing the products formed in C2H6–C2D6–NO (1:1:0.1) mixtures and (b) C2D6in the presence of H2S, which scavenges free radicals to form isotopically unique hydrocarbon products, and (c) C2H6 in the presence of C3D6, which scavenges H atoms to form propyl radicals, which in turn react with radicals in the system to form characteristic products. Such experiments, as well as quantum yield determinations, were also carried out at the krypton and xenon lines.

Pressure Effects in the Photolysis of Ethane at 1470 Å and 1577 Å, and Propane at 1470 Å

AbstractThe pressure dependence of the formation ratio of ethylene to acetylene in the photolysis of ethane at 1470 and 1577 Å has been studied, and the data have been analyzed according to the reaction scheme,magnified imageThe values of ks/kd and φ3/φ1 were obtained at both wavelengths. The C2H4 species produced in the photolysis of propane at 1470 Å following to the reaction,magnified imagewas found to undergo the reactions analogous to the above scheme and the corresponding values of ks/kd and φ3/φ2 were obtained.

Detection of Hydrogen Atoms and Free Radicals during the Photolysis of Ethane

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Primary Process in the Photolysis of Ethane at 1236 Å

The photolysis of ethane has been carried out at room temperature at the krypton resonance lines. The isotopic analyses of products in the photolysis of C2H6+C2D6 mixtures and CH3CD3 have been made to obtain information on the primary processes. From these results, the relative weights of the primary processes have been determined as follows: C2H6*→C2H4*+H2 41C2H4*→C2H2+H2 27C2H4*→ lim +MC2H4 14C2H6*→C2H4+2H 31C2H6*→CH4+CH2 22C2H6*→2CH3 <6These results agree with those reported by Hampson and McNesby.

Photolysis of Ethane at the Argon Resonance Lines 1067 and 1048 Å

Photolysis of Ethane at the Argon Resonance Lines 1067 and 1048 Å

Photolysis of Ethane at 1470 A

The photolysis of ethane at 1470 A has been investigated in the temperature range 25° to 240°C and over a wide range of initial ethane pressures. As reaction products were found mainly H2, CH4, C3H3, and C4H10. Traces of ethylene and, not identified, higher hydrocarbons were also detected. The results indicate that the primary step in the photolysis of ethane is C2H6+hν→C2H5+H.The amounts and ratios of products, formed during the photolysis, indicate that the reaction mechanism of the photolysis is similar to that of the Hg photosensitized decomposition of ethane. A few experiments on the photolysis of CO2 at 1470 A indicate that[open phi]CO increases with increasing temperatures.