Radiation-induced Isomerization Research Articles

Radiation-induced isomerization reaction mechanism of hydrocarbons on the surface of solid acid

This paper's goal is to investigate how petroleum's n-alkane isomerization reaction occurs on the surface of a solid nanocatalyst. In this experiment, the isomerization of aromatic-rich crude oil is being studied as a result of radiation exposure. It was discovered that sodium-rich bentonite –solid acid, from the Alpoid deposit works well as a catalyst for refining petroleum. Possible mechanisms of the radio-catalytic reaction that converts n-alkanes to branched hydrocarbons have been researched by methods of FT- IR spectroscopy and gas chromatography. The effect of acidity type of the nanostructured bentonite clay on Lewis acid cites is proposed to explain observed results. Additional radiation energy, which is mainly generated due to the nanobentonite volume, results in a more efficient aromatic- rich petroleum radiolysis process. Also, it was investigated the dynamics of dose –dependent changes in the amount of branched hydrocarbons. One of the primary objectives of this research work is increasing the efficiency of transformation of adsorbed beam energy in solid phase to the system and improvement of hydrocarbon isomerization reactions in crude oil. The results of hydrocarbon transformations are discussed in terms of the behavior of excited electrons in solids. Novel eco-friendly nanocatalyst creates new opportunities for hydrocarbons with multi- branched structures.

On the nature of radiation-excited unstable states of hydrocarbon molecules in heavy oil and bitumen

The high concentrations of the radiation-generated unstable molecular states necessary for propagation of the low-temperature chain cracking reactions in the petroleum feedstock are interpreted in association with the earlier reported effect of the intense radiation-induced isomerization especially characteristic for the high-viscous oils. The hypothesis of the interconnection between cracking and isomerization reactions is supported by the available experimental data on the dose rate dependence of radiation cracking rate and the data on the kinetics of radiation-induced isomerization.

Radiation-induced isomerization of thiourea into ammonium thiocyanate

The products of γ-radiolysis of solutions of thiourea are reported to be ammonia, sulfur, cyanamide, dicyanamide, and possibly guanidine sulfate. Ammonium thiocyanate, the product of isomerization, has not been observed although it is found to be one of the products in the themal decomposition of aqueous solutions of thiourea over the temperature range of 100–180°C. Hence, the observation of a close to 1% yield of the isomerization product in a 6.25% (0.82M) solution of thiourea, at neutral pH on exposure to γ-radiation from a60Co suurce at room temperature, would appear to be a result of interest in radiation chemistry. This paper present results on the variation of the yield of the isomerization product with the γ-dose. The experiments consisted in irradiating 2 ml of 0.82M aqueous solution of thiourea at neutral pH and under normal atmospheric conditions, i.e., at room temperature and with dissolved air present. The source of radiation was a 2.5 kCi (nominal)60Co source. The method used to detect and measure the isomerization product, ammonium thiocyanate was based on the well-known color reaction between CNS− and Fe+3 monitored spectrophotometrically at 450 nm, after obtaining the calibration curve of absorbance and concentration of NH4CNS. The yield of NH4CNS, expressed as\(G_{NH_4 CNS} \) was 0.083 molecules of NH4CNS for 100 eV absorbed. A suitable mechanism for the process of isomerization is suggested involving the hydrated electroneaq, the major primary product of water radiolysis. The mechanism is consistent with the observed effect of the addition of acetone, a well-known electron scavenger. This suppressed the yield NH4CNS by about 25%.

Radiation-induced gas-phase dealkylation and isomerization of p-tert-butyltoluene

D3+ ions, produced by deuterium γ-radiolysis, were allowed to react with gaseous p-tert-butyltoluene. The excited arenium ions formed, if not collisionally stabilized, underwent predominantly dealkylation to form toluene and, to a minor extent, isomerization. The dependence of reaction product yields on the substrate pressure is discussed.

ChemInform Abstract: Radiation‐Induced Gas‐Phase Concurrent Dealkylation and Isomerization of p‐Cymene

ChemInform Abstract: Radiation‐Induced Gas‐Phase Concurrent Dealkylation and Isomerization of p‐Cymene

Radiation-Induced Gas-Phase Concurrent Dealkylation and Isomerization of ρ-Cymene

D3+ ions, produced by deuterium γ-radiolysis, were allowed to react with gaseous p-cymene (p-isopropyltoluene ). The reaction leads to the formation of excited arenium ions, which, if not stabilized by collision, undergo predominantly dealkylation and, alternatively, isomerization. Dealkylation is favoured with respect to isomerization by an increase in substrate concentration, these results showing that dealkylation requires a lower activation energy.

Determination of H-crosslinks in γ-irradiated polybutadiene by 13C-NMR

The solid-state 13C NMR spectra of a 99% cis-1,4-polybutadiene after γ-irradiation at 25°C showed a reduction in the intensity of the -CH=resonance at 130.1 ppm and the development of a broad resonance at 45.8 ppm due to H-crosslinks. The -CH2-signal comprises the original narrow resonance at 28.2 ppm due to -CH2-groups remote from crosslinks, and a broad resonance centred at 30.5 ppm attributable to -CH2-groups adjacent to crosslinks. There was an increase in the intensity of the -CH2-resonance at 33.6 ppm due to trans -CH2-groups resulting from radiation-induced isomerization. Quantitative determinations of (i) the decrease in -CH= and (ii) the increase in crosslinked carbon atoms both gave G values of about 14 after 3 MGy. The crosslinks are evidently located in clusters, since literature G(X) values derived from gel contents and swelling ratios range from 3 to 6. The high G(X) value from NMR is consistent with a chain reaction for the crosslinking process.

Isomer yields for butanes and butanes from the radiation degradation of polyolefins

γ-Irradiation of high and low density polyethylenes and ethylene-α-olefin copolymers at temperatures from 30 to 175° produces butane, and above 100°, butene, in addition to hydrogen and other volatile hydrocarbons. The butane has been shown to be mainly isobutane at 30°, except for polymers with butyl branches; the isobutane/ n-butane ratio decreases with increasing temperature. The butene is mainly isobutene, with a lesser amount of 1-butene and only a trace of 2-butene. Scavenger studies indicate that both free radical and ionic intermediates are involved in the formation of the isomers. Irradiation of samples containing added n-butane show that only a portion of the isobutane can be formed by radiation-induced isomerization of primary product n-butane. Similarly, it is shown that 1-butene is an effective scavenger of H atoms to form n-butane, but is not significantly isomerized to isobutene.

RADIATION-INDUCED CHAIN ISOMERIZATION OF cis-2-BUTENE IN BENZENE SOLUTION

Abstract Radiation-induced isomerization of cis-2-butene was found to proceed in benzene solution by an ionic chain mechanism when total radiation dose is low. The yield of trans-2-butene reaches 103 in G unit under optimum conditions. Scavenging studies indicate that charge transfer from benzene cations to cis-2-butene and direct isomerization of cis-2-butene cations take place. Outlines of the results are presented.

1, 2-Dichloroetheneのγ線照射による異性化反応

1, 2-Dichloroetheneのγ線照射による異性化反応

Radiation-induced isomerization of the 1,2-diphenylpropenes in polar liquids

Radiation-induced isomerization of the 1,2-diphenylpropenes in polar liquids

Radiation-Induced Isomerization of [2,2,1] Bicycloheptadiene (Norbornadiene) to [2,2,1,02,6,03,5] Quadricycloheptane (Quadricyclene) in Cyclohexane Solutions

Radiation-induced isomerization of norbornadiene (NBD) into quadricyclene (Q) was studied in cyclohexane solutions. From the effects of charge and radical scavengers it could be concluded that at low NBD concentrations isomerization is initiated by a reaction of NBD with electrons and probably proceeds via singlet excited NBD. Low yields of Q show that this is not an efficient process. At higher NBD concentrations the isomerization becomes more efficient, indicating that other reactions may begin to contribute. Selfquenching of NBD* also becomes important at higher concentrations. In the presence of SF6, electron transfer from NBD− to this second solute occurs. Enhanced isomerization yields are observed in the presence of benzene, toluene, and acetophenone. Scavenger studies indicate that triplet-excited states of these solutes contribute to this increase in G(isom). They are formed by charge transfer from cyclohexane positive ions to the aromatic additives followed by neutralization. Complex formation between triplet-excited aromatic molecules and NBD is suggested to be an essential step in the isomerization reaction. Relative reactivities towards cyclohexane positive ions, estimated for methanol, toluene, and benzene, are, respectively, 1.0, 0.32, and 0.27. Calculated lifetimes of triplet-excited acetophenone, toluene, and benzene are between 10−6 and 10−7 sec. The excited states all react with NBD with rate constants between 5 × 108 and 5 × 109 M−1·sec−1.

Radiation-induced isomerization of the 1,2-diphenylpropenes in benzene and cyclohexane

Radiation-induced isomerization of the 1,2-diphenylpropenes in benzene and cyclohexane

Radiation-induced isomerization of 1-bromobutane by a free radical chain reaction

Radiation-induced isomerization of 1-bromobutane by a free radical chain reaction

Intersystem crossing in irradiated benzene and toluene

By use of the photosensitized (254 nm) cis-trans isomerization of butene-2 the triplet yields in liquid benzene and toluene at 25°C have been measured; they are 0.57 and 0.45. Internal conversion efficiencies are about 0.41 (benzene) and 0.48 (toluene). The effect of added xenon is to increase the triplet yield of benzene to unity. From these and similar experiments on the γ-radiation induced isomerization the rate constants for the 1S →3S and 3S → S processes in benzene catalyzed by the spin orbit coupling effect of xenon are deduced to be 2 × 108 M–1 s–1 and 3 × 108 M–1 s–1 respectively. There is evidence that xenon has an effect on ionic and other processes in the high-energy radiation-induced isomerization experiments. The application of benzene and toluene as organic photosensitizers is discussed.

Effect of charge scavengers on radiation-induced isomerization of stilbene in cyclohexane

Effect of charge scavengers on radiation-induced isomerization of stilbene in cyclohexane

Radiation-induced isomerization of cyclohexane on silica-alumina

Radiation-induced isomerization of cyclohexane on silica-alumina

Radiation-induced isomerization of stilbene in 2-propanol and acetone

Radiation-induced isomerization of stilbene in 2-propanol and acetone

Efficient and highly selective radiation-induced isomerization in the crystalline state

Efficient and highly selective radiation-induced isomerization in the crystalline state

Effect of dose-rate, and L.E.T., on the radiation-induced cis-trans isomerization of butene-2 in liquid benzene solution

Previous work with low dose-rate 60Co γ-rays has shown that the irradiation of cis-butene-2 dissolved in liquid benzene at room temperature causes isomerization to trans-butene-2, the G value rising with the concentration of cis-butene-2 to a plateau of G(trans)= 2.4 at ≈ 0.3 mole/1. of cis-butene-2. Experiments in which known triplet state scavengers (e.g., O2, anthracene) were added suggested that the triplet state of benzene was the main agent of the isomerization, and the concentration dependence was attributed to the competition between the normal decay of the triplet state, and reaction with cis-butene-2. [graphic omitted] The same measurements were done with a beam of 0.5 MeV protons as the radiation source, and G(trans) was depressed at all concentrations of cis-butene-2, e.g., at 0.3 mole/1. G(trans) was 1.2, These results could be explained on the basis of diffusion and reaction of the species involved if the self-annihilation of triplet states occurred BT+ BT→Bs+ B to form a singlet excited state and a ground-state molecule. Diffusion calculations show that for a normal spur size of ≈30 A diameter the rate-constant for this reaction would be high, ≈10101. mole–1 sec–1. The effect of the decay of singlet states to form triplets during diffusion was considered. A dose-rate effect was also found with fast (2–4 MeV) electrons in the sense of lower values of G(trans) at high dose-rate and substantial effects were noted for effectively steady irradiation at 3.9 × 1020 eV cm–3 sec–1. This dose-rate is much lower than that expected on the mechanism above, using the rate constants needed to explain the L.E.T. effect with protons. It is suggested that radicals formed in the bulk of the solution at high dose-rates are efficient quenching agents of excited states, and that the effective collision diameter for the quenching of excited molecules by radicals is ∼100 A.