Development of New Non-waste Catalytic Technology for Oil Desulfurization as a Method to Reduce the Environmental Pollution

This study is devoted to the development of non-waste technology of oil and petroleum refining. The experimental material of a soft catalytic oxidation of oil sulfurorganic compounds with formation of sulfoxides and sulfacides, having high consumer qualities is presented. Based on the IR-spectral data and mathematical calculations the optimal conditions of the process are defined, the kinetics of the oxidation is investigated and the process mechanism is offered. The results of research and approbation of highsulfurous oils of the Kazakhstan oilfields are presented. These materials are offered for introduction in the application by oil companies, which explore and produce the oil from oilfields of Western region of Republic of Kazakhstan.


Introduction
The republic of Kazakhstan is one of the leading countries in the world by pool hydrocarbon raw materials resources, however, a significant part of extracted oils is sulphurous and highsulfurous.
The production, preparation for transportation and transportation of such oils is accompanied by formation of sulfur-containing wastes, which represent serious danger not only to the state of natural environment possessing of their high aggression, but also render the influence on health of the population because of their high toxicity.
Besides, the presence of sulfurorganic compounds in raw materials promotes the fast corrosion of pipelines. During desulfurization the padding sources of losses of oil and petroleum are created, the level of environmental pollution by hydrocarbons and sulphurous compounds is high; the states of clearing of wastewater are more difficult. The consequent application of such oil in chemical processing results in the destruction of reactive vessels and poisoning of catalysts.
The highsulfurous oil is the oil of Tengiz oilfield, which is of one of the largest in the world. The distinct-ive peculiarity of Tengiz oil is the high content of volatile mercaptans having odor. Besides, the highsulfurous gas hydrogen sulfide accompanies the production of the oil. Taking into account the high toxicity and corrosion aggression of sulfurcontain compounds the development of new non-waste technology for treatment of oil and petroleum is really actual.
The ways of clearing, existing in the world practice, are limited by hydroclearing, i.e. at severe constraints to reduce the organic sulphurous compounds to H 2 S, which further by Clause method can be oxidized to free sulfur. The process is characterized by difficult technology and high power consumption. There is a large problem to remove the high-dispersed sulfur [7].
The sulfurorganic compounds of oil are represented basically by sulfides, tiophens, mercaptans etc. [2,3] One of the major reactions of sulphurous compounds is oxidation, which allows the formation of sulfoxides and sulfones, showing significant ability to donor-acceptor interactions with ions of noble metals. So, they can serve as high selective extraction reagents [1,[4][5][6].
It is known, that the Tengiz oilfield is located in a semidesert zone with a sharply continental climate.
This causes high responsivity of natural environment to negative techniques [7]. So, the introduction of nonwaste technology is one of the effective ways to lower the pressure on the environment.
The present work describes the experimental material on catalytic removing of sulfur compounds from oil.
The technology based on a liquid-phase method of soft oxidation, which does not demand difficult instrumentation and superstrong materials and allows utilizing available reagents (HNO 3 or NaNO 3 , H 2 SO 4 , H 2 O, air).
The current scheme to refine the oil from sulfur on Tengizchevroil (TCO) is the oxidation of mercaptans to disulfides, which are soluble in oil. So, there is a chemical transformation of one sulfur-containing compound to others, not having a smell. So, the aggression of sulfur is not eliminated. Unlike of the process used by TCO, we offer the catalytic system for oxidation of sulfur-organic oil compounds to sulfacides, which are insoluble in oil and remaining in aqueous phase, and, thus, can be extracted from petroleum composition.

Experimental
In order to find the optimal conditions for desulfurization of oil, which prevent the formation of sulfur-containing undesirable waste products we have investigated some inorganic metals sulfides as well as the catalysis of the process. The testing of the process on Karachaganac and Karazhanbas oils was done.
The inorganic sulfides were studied for determination of optimal conditions for sulfurorganic compounds oxidation.
A synthetic bismuth (CC-mark 85%), obtained by sintering of elementary sulfur and metal bismuth, with monitoring of composition by chemical and radiography analysis, was used as a starting material. The measurement of rate was done by volumetric method with absorption of oxygen by the system and reduction of bismuth sulfides amount during the time. The oxidation state of reacting particles in a solution were determined by redox potential measured by a platinum electrode in relation to a calomel half element. The IR-spectra were recorded using Specord, IR-25 and UR-20 spectrophotometers.
The sulfide coating generated during oxidizing dissolution of bismuth was washed by benzene, then again was introduced into the reaction mixture.
The kinetics of soft catalytic oxidation process of sulphurous compounds from Karazhanbas oil fractions is investigated.
The composition of starting and refined fractions of oil was established with the help of elemental analysis and IR-spectroscopy.
During the study the detection of the factors influencing the oxidation of halkpyrite and pyrite was done, and the opportunity for refining of sulfurcontaining oil by a method of homogeneous catalytic soft oxidation using the distillates from Karazhanbas and Karachaganac oil fields was shown.

Oxidation of metal sulfides
The obtained experimental data indicate, that in the absence of nitrogen oxides the oxidation of bismuth sulfide proceeds slowly (W O2 < 0.2×10 -5 mol -1 ⋅ L⋅s -1 ) owing to the exclusion till a back at interaction by lowest free molecular sulfides orbital. In the presence of NO x the rate of oxygen absorption by Bi 2 S 3 -HNO 2 -MCl 2 -KI -H 2 O system increases in 2-3 orders.
The obtained experimental data are summarized in the Table 1. The typical dependencies of oxygen absorption rate (W O2 ) as well as the values of redox potential of the system (ϕ) on amount of oxygen absorbed (Q O2 ) are shown in Fig. 1. The analysis of electrode equilibrium, possible in the investigated system is shown below: Based on the absence of the second saltus on the experimental potentiometric curves one can conclude that it is one-electron process (4); and its redox potential is determined by the following equation: (1)  e  w  t  h  g  i  g  ,   o  p  m  o  c  x  e  l  p  m  o  C  n  u  l  o  m  ,  d  L  /  t  s  e  T ti ,  e  m  m n  i   -t  a  r  e  p  m  e  T  u K  ,  e  r  ϕ V  ,  s  s  e  r  P  u e  r  O 2 a  P  ,   .  t  r  a  t  S  W O2 ,  0  1  to the following reactions (6) and (7): The second site, which affects the catalytic processes, is connected with the dissolution of bismuth. The kinetics of HNO 2 disproportion is investigated. The rate of direct reaction is defined by the following expression: In the presence of oxygen the disproportion of HNO 2 is shifted to the right with formation of NO 2 . The comparison of redox potentials for HNO 2 (HNO 2 + e -+ H + > NO + H 2 O φ=0.9 V) and for NO 2 (NO 2 + H + e -> HNO 2 φ =1.09 V), and also the kinetic results of the Table 2, specify the fact, that as a result of reactions (6) and (7) in the solution stronger is formed as contrasted to HNO 2 an oxidizer -NO 2 .
Separately we investigated the kinetics of HNO 2 oxidation by oxygen in HCl -MCl 2 -KI -H 2 O solution in conditions identical to oxidizing dissolution of bismuth. The kinetic results are presented in the coordinates W O2 -Q O2 in Fig. 1b. The dependence of absorbtion rate of oxygen in the solution HNO 2 -MCl 2 -KI -H 2 O (W O2 at τ > 0) on starting concentration of Table 1 Continued These results were used for determination of oxidizing dissolution rate of bismuth by a subtraction from common absorbtion rate of oxygen in Bi 2 S 3 -MCl 2 -KI -HCl -H 2 O system W O2 , concerning with the oxidation of nitrite to NO 2 only. The obtained, thus, kinetic regularities are summarized in Fig. 1.
The curves had an extreme nature ( Fig. 1c) in coordinates W O2 = F(α). In the beginning of the reaction the rate is small, then it increases, passes through a maximum and decreases practically to a zero, or to the values, which are distinct from zero, feebly time-  nitrite is described by the equation: dependent. Such character of the curves frequently meets the kinetics of topochemical behavior reaction in the systems, which are powering up even one solid reagent and a solid product of the reaction. So, the solid products can be and on its basis a polysulfides. The inclination of sulfur atoms to formation of polysulfides phases, is probably conditioned by aspiration of sulfur atoms to acquisition of energetically steady electronic configurations, that is possible as a result of acquisition by one atom of sulfur s 2 p 6 , and another sp 3 (s 2 p 4 + s 2 p 4 > s 2 p 6 + sp 3 ) with continuous interchanging by configurations between these atoms and realization of bond between them by pair of electrons crossing from atom to atom. The presence of elementary sulfur and of polysulfides phases formed during disalcalining on a surface of bismuth, is tested by IR -spectra of benzene extracts from the cover of disinclining samples (Fig. 2). The absorption band in the field of 470 cm -1 belongs to the valence vibrations of S-S group. Upon contact of gas with starting solid (Bi 2 S 3 ) the reaction rate is small. As the nucleuses (kernel), and phase of solid product of the reaction are formed, there is an interface of solid phases. The value of this interface increases in the process of sulfides oxidation and the reaction rate increases.
The further increasing of nucleuses of the phase of solid product begin to merge. The formation of new nucleuses practically does not occurred because the absence of a free surface and the reaction rate is decreased. The kinetic curves of topochemical reactions contain a special point, the maximum of reaction rate. According to the independent growth of nucleuses of the phase of the solid product the maximal rate should be observed at the moment of a contingence of growing nucleuses. So, the value of specific rate can be defined from the following equation: g-weight, S g -specific cover of the sample.
The useful information is presented by IR -spectra of the gas phase (Fig. 3). In the spectra of the sample selected from the reactor, containing aqueous solution HCl -MCl 2 -NaNO 2 -KI -H 2 O through 3, 20, 60, 90 minutes after experiment was started there are bands with frequencies of vibrations of nitrogen dioxide (1318 cm -1 ), (749 cm -1 ) and (1617 cm -1 ) and N 2 O (1200-1300 cm -1 ) with maximum at 1250 and 1270 cm -1 , NO (500-600 cm -1 ) with peak 588 cm -1 and NO (2150-2240 cm -1 ) with peaks 2190 and 2220 cm -1 . The absence of absorption bands, characteristic for N 2 O without of bismuth sulfides gives foundation to believe, that N 2 O is the product of more deep reduction of NO 2 by bismuth by the reaction: And the amount of N 2 O as increased as higher the weight of Bi 2 S 3 and higher the acidity of the solution. The redox potential for N 2 O (N 2 O + 2 e -+ 2H + →N 2 ) is 1.59 V and the nitrous oxide does not oxidate by oxygen. According to it, the part of nitrogen oxides irrevocably disappears from a catalytic cycle, which includes the following reaction: Using the IR-spectra of N 2 O (vol.%) and IR-spectra of samples selected during experiment (Fig. 2) it was possible to calculate the amount of N 2 O formed and accordingly amount of sodium nitrite leaving from a catalytic cycle in each case. For further accounting of the rate constants value of maximal rate on the curve W O2 =f (Q O2 ) and value, accordingly to NaNO 2 concentration were used.
The dependence of the process rate on the sodium nitrite concentration is described by the equation of the first order: The increase of the weight of bismuth is a result of increase in the process rate.
The dependence of k 1 '' on the amount (g) of Bi 2 S 3 is described by the expression: At Ð O2 > 0.6×10 5 Pa practically there is no influence of a partial pressure of the oxygen in the mixture on the rate of Î 2 absorbtion in the system. In gases enriched by oxygen the formal regularities are observed, and on the contrary, at Ð O2 < 0.5×10 5 Pa, the following equation is realized: W O2 =k'× P O2 The order of reaction on bismuth is lowered and the order of reaction on concentration of sodium nitrite is increased, i.e. the conditions are created, when the stage with oxygen participation is limiting.
At P O2 =1.01×10 5 Pa the influence of solution acidity on oxidation rate of bismuth in HCl -MgCl 2 -KI -NaNO 2 -H 2 O solution is investigated. The increasing of acidity in the interval of C HClO4 from 0 up to 1 mol/L positively has the effect on the reaction kinetics (3). The increasing of activity of the solution in this interval C HClO4 is a result of the accumulation of NO 2 HCl and NO 2 HI particles in solution by the following equilibrium (8): As a result of the oxidation the salts of sulfuric acid are formed. It is the important moment, because it determines the opportunity for extraction of heavy metals as soluble forms in the liquid phase from petroleum composition, and, generating, the acid accelerates process and extraction of a vanadium and nickel from the oil of Tengiz oil field becomes possible.
The quantum characteristics for NO 2 , NO 2 HCl, NO 2 HI were calculated, and are presented in the following table: For NO 2 the lowest vacant molecular orbital (LVMO) is basically presented by P y -orbital of nitrogen, also there is a composition P z -orbital of halogen, and at transferring from NO 2 HCl to NO 2 HI in it's the contribution of this orbital increases. The values of E LVMO show that the acceptor properties of NO 2 HÕ are higher, than that of NO 2 .
Upon the increase of C HClO4 > 1 mol/L the character of the kinetic curves varies, the maxima decreases, the sharp decrease of the rate is observed during the oxidation of bismuth. In IR -spectra of the gas phase in these solutions there are some absorption bands in the field of 500-600 cm -1 , 1500-1650 cm -1 , 1700-1820 cm -1 with maximum at 595-1580 cm -1 , 1798 and 1802 cm -1 , concerning with the NO in NOX (X-Cl, I), that specifies the realization in data states of equilibrium (12), (13):

HNO 2 + HI ↔ NOI + H 2 O HNO 2 + HCl ↔ NOCl + H 2 O
The particles of NOX are reduced by bismuth sulfide to the N 2 O and so the concentration of sodium nitrite from 4.56×10 -1 mol/L (C NaNO2 ) to 0.16 mol/L is originated.
The increase of temperature in the interval from 22 to 40°C results in the fact that the maximum on the curve becomes brightly expressed and it is displaced to the side of smaller time.
The values of maximal rate calculated on the foundation, that the value of activation energy of the bismuth sulfide oxidation by oxygen in the presence of NO x equal to 10.205 kcal/mole and is decreased up to 7 kcal/mole at Q O2 = 2.5×10 -2 mol/L (after a maximum).
The above mentioned fact indicates the diffusive stopping of the reaction after reaching maximal rate, that results in the sample covering by the polysulfide coating.
In order to remove the sulfides coating, the generating during oxidizing dissolution a sample was washed by benzene, then again reverted to the reaction ( mixture. The increase of oxidation rate of bismuth sulfide testifies the dissolution of a sulfur coating. This fact is confirmed by the IR-spectrum of a benzene extract from washed bismuth surfaces. The absorption band at 470 cm -1 corresponds to the frequency vibrations of the S-S band (Fig. 4).
This experiment has a practical importance for originating of bismuth oxidizing dissolution in mixed solvent.
The obtained results have allowed offering the following mechanism of the oxidation of bismuth sulfide by oxygen in the presence of nitrogen oxides: According to the reactions (14,15) the NO 2 and more reactive forms of NO 2 HX are formed. In limiting stages (17) and (21) the NO 2 HX attacks coordinated sulfide or polysulfide with transferring of one electron and formation of ÍNO 2 . As a result of the reaction (22) the concentration of the catalyst NO x is decreased. According to the offered scheme and the theory of topochemical reactions as well as the method of sta-tionary concentrations the obtained rate law describing the experimental results in kinetic conditions are described by the equation (24).
In investigated interval of Ñ HClO4 the value of k' practically does not depend on the acidity of the solution.

NO 2 + H + → NO(OH) +
The solution of the equation (25) by the least squares method has allowed defining the parameters of the equation (25), which are the following: k 1 " = 4 ·10 -1 g -2/3 ⋅s -1 and γ = 7.8×10 -2 The segment of the axis ordinate, cutting off by straight line gave us the value of the constant of oxidation rates of the sodium nitrite by oxygen (k') in the investigated conditions. The tangent of inclination corner allows determining the rate constant of interaction of NO 2 or him of the protons forms with bismuth in (k''). The results presented in the Table 3 testify that the k' and the k'' do not depend on starting nitrite concentration in the system and on the weight of bismuth sulfides. The values of k' are in accordance with the literature data. The obtained data prove the proposed mechanism. Table 3 Kinetic characteristics of bismuth sulfides oxidation by oxygen in HCl -MCl 2 -KI -NaNO 2 -H 2 O system Ò=295Ê, C MCl 2 = 1.5 mol/L.

Oxidation of sulfur compounds of oil
The method of homogeneous soft catalytic oxidation was investigated on the sulfur-containing oil fractions. The sample from Karachaganac oil field (¹ 126 well) was taken for the study. According to the data obtained in our study the common sulfur is 1.28% by weight. The weight fraction of mercaptanous and hydrosulfurous sulfur compounds is 0.21%.
The experimental data of regular study of the sample of oil and catalizate by the method of homogeneous soft catalytic oxidation is shown in the Tables 4-9 and Figures 5-11.
The potential contents of fractions in starting oil and catalizate were determined by the method of rectifying distillation on the ROD-2.
According to the diagram of samples distillation the initial boiling temperature moving almost to 40°C, the weight fraction of 10-grades of fractions varies. At temperature higher than 150°C, for oil boils away 28.39% of total weight, and for catalizate only 18.22% (Table 4, Figs. 5,6). It is possible to approve, that the hydrocarbon composition of catalyst significantly "is weighted" as contrasted with starting sample of oil. The pressure of 10-grades of fractions also significantly varies.
The results of chromatographic study are presented in Table 5. These data confirm and supplement the   results of distillation. The most significant result of the study is the fact, that the catalyst does not contain even traces of mercaptanous and hydrosulfurous sulfur after originating the homogeneous catalytic oxidation of raw oil. The sulfur containing organic compounds are absent in all fractions.
The addition of nitrogen oxides to the solution of the acid, or their addition to oxidizer promotes the increase of oxidation rate. The oxides of nitrogen are easily deleted from oil at temperature of the reaction (80-90°C) and are dissolved in sour water solution, in which they are collected as a result of sulfoxides and sulfacides oxidation.

Table 5
Chromatographic analysis (component composition) 10grades of fractions of oil and catalizate from ¹ 126 well.
The aqueous solution can be utilized multiply up to concentration of sulfacides -70%. The obtained by abovementioned procedure solution, represents acid contact obtained in the industry at the suffocation of oil. It has surface-active properties and can be utilized as marketable products for preparation of washing-up liquids, flotators, etc.
At present time the industry and transport of Republic of Kazakhstan consumptions are increased and great money are required. According to the  Table 6 Physical-chemical properties of Karazhanbas oil.
In order to determine the optimal composition of the catalyst and optimal state of a catalytic oxidation of the sulfurous sulfur, the mechanism of reaction as well as the kinetics of soft catalytic oxidation processes of sulphurous compounds from fractions of Karazhanbas oil was investigated in details. The characteristic spectra of the oils are presented in Figs. 7,8,9. The absorption bands corresponding to sulphurous compounds have the maxima in the area 460, 580, 620, 680, 700, 1070, 1330, 1450 cm -1 , which are characteristic for sulfidous and mercaptanous sulfur.
The data of IR -spectra have shown predominance of absorbed structures as CH, CH 2 and ÑÍ 3 (absorption bands in the field of 3000-2800,1470,1380 cm -1 ) and group CH 2 of long paraffin links, included in the composition (absorption band 730 cm -1 ), weakly expressed [1,[8][9][10]. For all samples the presence of aromatic structures of different types of substitution (900-750 cm -1 ) (one -, di -, three-substituted derivatives of benzene is typical). The absorption band at 815 cm -1 together with absorption band at 1610 cm -1 can be attributed to the presence of para-substituted benzene ring [1,[8][9][10] The kinetic regularities of the catalytic oxidation in the temperature interval 293-323 Ê were investigated depending on the concentration of all reagents making up the catalytic system, partial pressure of oxygen and temperature of experiment.
The typical conversion curves of the catalytic oxidation of oil sulfides by oxygen in system FeSO 4 × 7H 2 O -Kt -H 2 SO 4 -oil fraction -H 2 O, where Kt-water soluble Ð-oxide being the with -catalyst of the given process of activation of oxygen are presented in Figs. 10,11. In the absence of Kt and compounds of iron the rate of oxygen absorption, as for petrol, and for diesel fractions is small and also does not exceed the  Table 8 Data of distillation of hallmark of Karazhanbas oil.

Table 9
The data of distillation of hallmark of Karazhanbas oil at atmospheric pressure.  Fig. 7. IR-spectra of the petrol fraction. Fig. 8. IR-spectra of diesel fraction. At Ò=303 K the rate constant for petrol and diesel fractions is equal to 1.32 s -1 and 8.7×10 -1 s -1 accordingly.
It is necessary to note, that the activity of sulfides of the petrol fraction is higher, than the activity of sulfides of the diesel fraction.
As a result of catalytic process the data of IRspectra have shown the absence of absorption bands in the hydrocarbon stratum, characteristic for sulphurous compounds. It is the fact that the complete absence of sulfur in the organic stratum. According to Fig. 9 the absorption band in the area 460, 580, 620, 680, 700 cm -1 have vanished. These data are confirmed by the results of elemental analysis.
The potentiometric results and analysis of literature data on catalysis by compounds of iron on oxidation of different substratum by oxygen have shown, that the most limiting stage of the process is connected with regeneration of three-valence iron by oxygen. So, the catalyst (Kt) in the system was selected. The concentration of Kt was changed in the interval: 5×10 -2 -2.5×10 -1 mol/L the concentration of other components is remained consternated and were: Ð O2 =1.05×10 5 Pa, C FeSO4 =1.0×10 -1 mol/L, C H2 SO4 =1.75 mol/L. The rectilinear dependence of initial rate of the oxidation on starting concentration of the catalyst (Kt) in the system, as for petrol, and for diesel fraction is observed: At 303 Ê the value k 1 for petrol and diesel fractions is equal accordingly: 9.0×10 -1 s -1 ; 4.6×10 -1 s -1 .
The comparison of k 1 values for petrol and diesel fractions specifies the large activity of sulfides of petrol fraction to the oxidation as contrasted to diesel.
The sulfuric acid was selected as the proton-donating agent, which concentration in the system was varied from 1.75-7.0 mol/L, at constant concentrations of the other components of the system, which were: C Fe =1.0×10 -1 mol/L, C Kt =2.0×10 -1 mol/L, P O2 = =1.05×10 5 Pa.
When the concentration of the acid in the investigated interval was increased the character of the conversion curves was not varied. The starting potential according to the increase of concentration of the acid is increased on 0.1-0.15 V. When the acid concentration is increased, the character of movement of potential varies at the end of the reaction up to the concentration of the acid equal to 3.5 mol/L (at the end of experiment). All this specifies the influence of acidity of environment on the oxidizing ability of the system, activation rate of oxygen in a sluggish stage.
The dependence of initial rate of oxygen absorption, as for petrol, and for a diesel fraction from concentration of the acid is described by the follow- tinguished by a way the intake of the trickle fluid, section and length of a neck, by arrangement etc. It is usual intake of the fluid is carried out immediately in the neck at right angle to a stream of gases, and precipitation of drops in the device of the centrifugal operation. The fluid (in this case catalyst) is brought to confessor on some distance from the neck with the help of nozzles allowing to inspect the sputtering. As the liquid trap after the pipe is established the straightflow a cyclone. The mathematical accounts of pipe of Venture made on the basis of filtration model.

Conclusion
At the condition of development of oil industry in our republic expedient and necessary the introduction of non-waste technologies is made. The soft catalytic desulfuration of oil allows to solve not only the task of improvement of state of environment of region arranging of the plant, but also will open new ways of deriving of quality fuel, and defined after sulfurtreatment of oil and the gas, probably, will let off for the prices appropriate to high-quality fuel raw material in the world market. The degree of desulfuration of the given technology is great enough (92%), and it allows to recommend it to introduction on TCO oil company. The solution of the equation (28) by the least squares method has allowed defining the partial rate constants k 1 and k 2 and value of the equilibrium constant The absence of sulfur as the product of the reaction, and the quality detection of sulfoacides in water solution after reaction, allow to assume, that the oxidation of sulfides of petrol and diesel fractions origins up to water-soluble sulfoacides in the studied conditions.
The completely exceeded kinetic results are described by the equation (31) The indicated mechanism of the oxidation of oil sulfides in our conditions includes two slow stages (32), (33): Selection of the equipment now is made, the designer account of installation is picked up by productivity 20 t/day of raw oil and tested apparatus ensuring intensive of mass transfer a gas -fluid during oxidizing desulfurization of oils.
The review of the literature of last years has shown, that the apparatus which is carrying out gas liquid agitating in a turbulent state is the most suitable for this purpose. The most widespread device of a rotational type is the scrubber of Venture, which main body of it for purposes of lowering harmful hydraulic losses is executed as the pipe of Venturi having smooth lowering on the input of gas (conphuzor) and smooth expansion on its exit (diffuser). There is the great of constructions of scrubbers of Venture dis-k I (32) k II (33)