Published October 2009

Photochemical processes and energy transfer among components of petroleum luminophores

A.P.Mamedov

R.A.Jafarova

During exploitation and storage in many cases petroleum luminophores ( PL ) undergo an action of light of Sun and artificial sources that brings about photochemical and photooxidative processes in them, as a result of which composition and properties change. So, it is of a large interest to elucidate stages and mechanism of these processes which enables to purposefully change them and to find ways of light-stabilization of PL and resinous – asphaltene substances. The present work is dedicated to a study of photochemical processes and energy transfer in PL obtained both from heavy gasoil of catalytic cracking and heavy resin of pyrolysis. For studying the mentioned processes methods of UV- and IR-spectroscopy, photoluminescence, photothermoluminescence, photothermochemiluminescence and EPR have been applied. It has been shown that under an action of mono- and polychromatic action in the whole of UV- and visual field of spectrum photochemical processes occur with different efficiency. Thus, in unsubstituted polycyclic aromatic hydrocarbons (PAH) in airless medium during photoirradiation in the range of their electron spectra of absorption decomposition does not take place which is related to the circumstance that E* In alkyl-substituted PAH af monochromatic irradiation process of dimerization does not occur. Upon irradiating them by polychromatic light photodecomposition of alkylsubstituents takes place. This process apparently proceeds according to two-photon mechanism. It has been shown that with dilution of PL a decrease of concentration of PAH of the highest molecular mass occurs ( below a critical concentration ). In this case their luminescence becomes insufficient for observing it. This fact indicates that PL in distinetion to synthetic luminophores possess changeable luminescing properties. In other words, when dissolving PL a colour of luminescence changes. It has been established that, despite the fact that in native petroleums and products of their refining mono-, bi-, tri- and more cyclic aromatic hydrocarbons are contained, upon irradiating them by UV-light glow is observed which is stipulated by highly-condensed PAH. It shows that among PAH components in PL a “cascade” transfer of energy from low-molecular PAH to high-molecular ones takes place which causes an observed luminescent glow.

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