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1.4. Vanadilovye complexes and free stable radicals in neftjah and oil components


Paramagnetism neftej is caused, basically, presence in them of free stable radicals (not coupled electrons, affairs okal izovan - nyh on polyconjugated systems, g = 2,003) and atoms of paramagnetic metals, first of all V4 + (basically present at a kind of complexes of an ion of vanadyl V02 +).
The maintenance of the paramagnetic centres in petroleum crudes is in limits 1017-101 s sp./g [65].
Concentration of the paramagnetic centres in asphaltenes routinely connect with their fragrance, representing a molecule of asphaltenes as a polyconjugated system which promotes stabilisation of a not coupled electron [85],
Method EPR it is possible to receive the following information [5: 1]. Qualitatively to analyze paramagnetic connections, to define type of kernels, the radicals interreacting with not coupled electrons.
On a parity intensivnostej spectrum lines it is possible to make quantitative measurements, to calculate number of kernels, radicals, vyzy-vajushchih thin and hyperfine structure of a spectrum.
To investigate the mechanism of reactions at which as intermediate products free radicals and so forth are formed
To study electronic structure of complexes of ions of transitive metals, etc.
On fig. 12 the typical spectrum smolisto-asfaltenovyh substances neftej is resulted at 77 K.Na it superposition of three groups of lines - lines of free radicals and two groups of lines on eight in everyone is visible, corresponding to complexes of the quadrivalent vanadium which axis of symmetry is oriented collaterally (qn) and is perpendicular (qt) to a direction of an external magnetic field. The number of lines in each group (8) corresponds to interaction of not coupled 3d1-electron V4 + with its nuclear spin 1=7/2.

Fig. 12. Typical spectrum EPR smolisto-asfaltenovyh substances
As work [8] affirms, that asphaltenes of some West Siberian neftej have concerning the big paramagnetism - 1021 sp. It is noticed, that sometimes spectrums of petroleum crudes contain a wide line of the absorption which intensity is estimated as 102О~Ю21 sp/sm3 [87].
Concentration of paramagnetic particles substantially depends on value of molecular weight of asphaltenes, degree of fragrance, a way of allocation, from the maintenance of heteroatomic connections, especially oxygen-containing which, apparently, can have quinoid structure [88]. It has been shown, that concentration of the paramagnetic centres [89] and solubility of asphaltenes [90] rectilinearly depend on the relation With: N.Nabljudajutsja private laws between concentration of the paramagnetic centres and relations N: With, S: With and About: With.
In other work inverse relationship between paramagnetism and solubility of asphaltenes [91] is revealed. According to EPR for all asphaltenes big time of backs-trellised of a relaxation that confirms a conclusion about significant delokalizatsii not coupled electron having a small constant of backs-orbital of interaction is observed.
For the present moment enough proved and known is, so-called, cellular model free radicals in neftjah. According to this model [76, 92, 93], free radicals effectively ekranirovany asphaltenes that preserves them from reactions of recombination with hydrogen etc., and also conserves radicals in oil during geological time. Similar model [92] explains many important experimentally registered properties connected with aggregation of asphaltenes, but it is completely based on semiempirical kvantovo-chemical calculation and results of modelling by methods of molecular mechanics.
Authors [94] study reliability of formation of traps on an example metilnyh radicals and neutral tsikloaromaticheskih systems. It is shown, that interaction energy corresponds to energy of formation van - d er-vaal sovyh complexes.
Thus, effective business kal izovan - nyh on polyaromatic fragments of molecules of asphaltenes similar fragments of asphaltenes and resins result ins shielding of radicals of high stabilisation of radicals and finally to constant paramagnetism nativnyh neftej. At technogenic influences on oil or its long-term storage the maintenance of the paramagnetic centres can change considerably. At standard allocation of asphaltenes, possibly, change of concentration CP in the evolved (solid) asphaltenes in comparison with maintenance CP in asphaltenes before their allocation from oil will be observed. And it is obvious, that degree of change of paramagnetism will depend on features of composition and structure of asphaltenes. Similar researches of communication structure - paramagnetic properties of asphaltenes in the literature are absent.
Studying of interrelation of paramagnetic complexes neftej, in particular vanadilovyh, with the condensed polyaromatic structures in neftjah helps to solve a fundamental side of the problem of extraction of trace elements. The vanadium maintenance plays an essential role in questions of petroleum refining and definition of perspective deposits for allocation of a concentrate of valuable metal.
In structure of oil components vanadium can be, in particular, in a kind vanadilovyh the complexes including in the composition difficult high-molecular ligands (fig. 13).
S

Fig. 13. A hypothetical molecular structure containing tetrakoor - dinirovannyj a vanadyl ion (drawing is executed by the author)
In work [95] results EPR of spectroscopy of heavy oil fractions for the characteristic of internal coordination sphere round vanadyl-ion V02 + are resulted. It has been positioned, that isotropic parametres of spectrum EPR are more informative.
Definition vanadilporfirinovyh complexes (VP) in neftjah the Western Kazakhstan is made in [96]. Temperature effect on intensity of lines in spectrum EPR has been studied. It is positioned, that temperature depressing result ins to lower limit of detection of vanadium method EPR.
neporfirinovye vanadium and nickel structures were studied by authors [97]. neporfirinovye vanadium connections are similar vanadiltetrafenillor - firinam with four atoms of nitrogen and one atom of oxygen.
In work [98] defined the maintenance of the paramagnetic centres in a considerable quantity of samples of pitchy components of modular West Siberian oil. Weak stability of resins in relation to various physical and chemical influences is noted. Concentration of paramagnetic particles in the pitchy substances evolved with the standard adsorptive
Methods from the West Siberian oil and petroleum residue, reach (3-7 1 ft
10 sp. the Least paramagnetism is characteristic for nativnyh the resins which were present at composition of petroleum crude. Paramagnetic are to 1-2 % of total number of molecules of resins. Radical paramagnetism of resins does not exceed 10 % from maintenance CP in initial oil.
From data of work [99] follows, that on a share of resins it is necessary to 50 % COMPARE Thus the total maintenance CP calculated in asphaltenes and resins, according to the maintenance of the last exceeds sizes of concentration CP measured immediately for samples of oil, the Yielded fact speaks destruction of a part of diamagnetic complexes CP and VK at fractionation of oil and their formation again at preparation of mo-efficient oil from fractions.
However it is known, that paramagnetism nativnyh resins and the resins subjected to processing (extraction on silica gel, heating to 100С at otgonke solvent), differs in tens times. Resins by right fall into, so-called, to substances with variable paramagnetism [87]. Therefore, generation CP in the evolved resins is caused more likely by the reasons of transferring of a part of electrons in a triplet state. Being reverted to work [99] it is necessary to notice, that along with generation CP in the evolved resins and asphaltenes "lack" of 25 % vanadilovyh complexes which it agree to the logician of authors is observed should were to be generated opposite. However this fact authors does not speak.
Laws of change of maintenance CP depending on maintenance VK and other components in neftjah and smolisto-asfaltenovyh veshchest-vah (CAB) are investigated enough [17, 99-102]. And practically significant it is possible to consider as the Most informative by right existing vzaimoza-visimosti various paramagnetics neftej, in particular VK and COMPARE However the unequivocal reasons of existing dependences of maintenance CP from maintenance VK (CP = F (BK)) in neftjah and asphaltenes are not positioned.
Data about a kind of dependence CP = F (BK) in neftjah are inconsistent. So, employees of the All-Russia oil and gas scientific research institute of akad. A.P.Krylov [99, 100] is positioned obratnoproportsionalnyj a kind of the specified dependence for neftej deposits of the Ulyanovsk area. It is necessary to notice, that for group neftej with the depressed maintenance of vanadium the tendency to dependence has a directly proportional appearance. According to yielded R.N.Nasirova [102] for neftej Kazakhstan, characterised by wide distinction under the vanadium maintenance, observes the tendency of increase in share CP with increase in concentration VK.
For asphaltenes the discussed tendency in general obratnoproportsio - nalnaja [17, 101], however there are private tendencies for asphaltenes from neftej, bitumens and bituminous breeds.
V.E.Galtseva's work with sotr. [99] - one of the few in whom authors the explanation of the nature received by them obratnoproportsio - nalnoj is offered to dependence CP = F (BK) for neftej. On the basis of a return parity of relaxation properties of electrons in neftjah obosnovanno and logically the conclusion about small mobility of system Vk-ASPHALTENES becomes. On-slednee contacts formation of strong associates VK with asphaltenes. Further under formula Vijarda [103] on the basis of spin-spin relaxation times calculation of the agent ushirjajushchego a signal of free radicals, i.e. vanadilovyh complexes is manufactured. The average values of maintenance VK received experimentally below calculated on the basis of fixed times of spin-spin relaxation. This material lack VK speaks that increase of local concentration VK in associates can result in to formation of diamagnetic complexes VK with fragments of the asphaltenes, containing COMPARE
However average values of concentration VK resulted by authors fall into to oil system as a whole. The values calculated under formula Vijarda local concentration VK fall into to associative formations (micelles) of oil and, naturally, received values above. If chzhe to carry out calculation of maintenance VK not on oil as a whole, and on total quantity CAB which are the basic components of micelles compared concentration VK will not differ considerably. Thus, the conclusion about formation of diamagnetic complexes between molekuami vanadilovyh complexes and fragments of the asphaltenes containing nespa - rennyj an electron is represented, at least, not quite proved.
It is necessary to notice, that presence of associates of resins, vanadilovyh complexes and asphaltenes it is marked by other researchers [87, 92, etc.]. In the specified works formation of associates is represented at the expense of exchange, orientation, "l-l-aromatic" and other interactions.
Authors [104, 105] notice, that in spectrum EPR in the presence of paramagnetic ions of metals it is possible to explain the observable phenomena of a flare of signal CP shorter relaxation times of ions of metals in comparison with those for CP owing to what the spectrum line form, in particular, changes, that often result ins to understating of integrated intensity of registered signals.
In works [106, 107] it is underlined, that in spectrums EPR of asphaltenes neftej, besides peaks of organic radicals typical for oil asphaltenes and peaks of hyperfine structure VK, there is the wide strip corresponding to multispin metals with the g-factor 1 and 2: Fe, With, Mp, Si and another. Concentration of the carbon and vanadic paramagnetic centres in asphaltenes residual neftej above, than in asphaltenes taken neftej.
Because of differences in structure and composition of asphaltenes distinctions of properties of the oil disperse systems having similar componental composition are observed. However features of paramagnetic characteristics of asphaltenes which finally are defined by structure of asphaltenes, are poorly shined in the literature. Separate works concern only quantitative estimations of paramagnetism of asphaltenes and their fractions. 1. 1.5. Research problems
It is necessary to notice, that in Russia there are advanced works in the field of basic researches of oil disperse systems. However, in studying of structural features of asphaltenes which form a dispersed phase neftej and, finally, define properties neftej at all stages of extraction, preparation and processing, there are white spots. In bolshej degrees it falls into to researches of features of asphaltenes neftej with the various maintenance of vanadium. In this respect, deposits of Tatarstan are unique, as extracted oil (depending on geological conditions zaleganija) are characterised by wide distinction of composition, for example the maintenance of asphaltenes from 0,4 to 12 mas. %, vanadium from 0,0003 to 0,08 mas. %.
Studying of character of interrelation of maintenance VK and CP in neftjah different authors has yielded ambiguous results that does not allow to systematise them. Attempts of an explanation of the nature of observable dependences CP = F (BK) are inconsistent.
Revealing of the nature of dependences of maintenance CP from maintenance VK in neftjah and asphaltenes probably at the decision of following problems:
Studying of degree of possible interaction oil vanadilovyh complexes and the models containing free stable radicals;
Working out of the methodical approach to unification of relative units of measure of concentration of paramagnetics in neftjah both asphaltenes, and the analysis of interdependence of the maintenance in them of paramagnetics.
The literature review on studying of structure of asphaltenes has not yielded the unequivocal answer about localisation of the fragments containing not coupled electron in structure of "volume" molecules of asphaltenes. There are no authentic data about possible changes in concentration CP in asphaltenes after their allocation from oil.
Qualified and rational use of an oilstock is possible only with deepening of knowledge of a place and a role of asphaltenes and metallic connections as a part of oil supermolecular structures, about structural features of the asphaltenes differing with the maintenance of vanadium. Expansion of knowledge in the specified areas predetermines necessity of following researches:
The analysis of degree of extraction of the paramagnetic centres asphaltenes from neftej with the various maintenance of vanadium;
Studying of distinctions of asphaltenes on spectral factors characterising features of structure of asphaltenes, their comparison to paramagnetic characteristics of asphaltenes and the vanadium maintenance.
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A source: Tagirzjanov, Marseilles Ilgisovich. ASPHALTENES VANADIJSODERZHASHCHIH neftej (on an example of oil objects of deposits of Tatarstan) the Dissertation on competition of a scientific degree of a Cand.Chem.Sci. Kazan - 2003. 2003

More on topic 1.4. Vanadilovye complexes and free stable radicals in neftjah and oil components:

  1. 6.1. Degree of extraction of free stable radicals and vanadilovyh complexes asphaltenes from neftej
  2. 3. CHARACTER of INTERRELATION of MAINTENANCE VANADILOVYH of COMPLEXES, SULFUR And FREE RADICALS In neftjah IASFALTENAH.
  3. 3.1. Laws of interrelation of the maintenance vanadilovyh complexes with the maintenance of sulphur, asphaltenes and free radicals in neftjah and asphaltenes.
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  9. 1.2. Vanadium connections in neftjah and their distribution on a compo-nentam
  10. 2.2.7 Technique of definition of maintenance VK and CP in neftjah and asphaltenes method EPR
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