EP0269515B1 - Process for the thermal conversion of heavy petroleum fractions and of refining residues in the presence of oxygenated sulfur or nitrogen compounds, and compositions containing these compounds - Google Patents

Description

The invention relates to a process for the thermal conversion of a charge consisting of a heavy fraction of organic matter in the presence of oxygenated organic compounds of sulfur, or of nitrogen and a composition comprising these compounds.

It is particularly applicable to the petroleum and coal refining industry and in particular to visbreaking and catalytic hydrotreatment processes.

The improvement of heat treatment processes used in the petroleum industry for the refining of fossil organic materials rich in high-mass polyaromatic structures, coke promoters, such as heavy and related oils: bituminous shales, coal, asphalt sands, etc. and the refining residues, implies a control of the radical transformation processes by the use of efficient solvents or additives.

Numerous studies have been devoted to the use of hydrogen-donating solvents (hydroaromatic structures such as tetralin, dihydroanthracene or partially hydrogenated petroleum fractions), capable of effectively inhibiting the development of radical polycondensation or polymerization reactions. in chain.

However, under identical conditions, the use of an efficient hydrogen donor leads to a more moderate conversion into light fractions when reactive intermediates which promote chain fragmentation processes have been eliminated from the reaction medium. This aspect of the problem has led to the association of additives capable of carrying out together the radical capture and the activation of the fragments of the polymolecular aggregates present in these heavy fractions.

Various studies mention the effect of hydrogen sulphide, present during treatments of sulfur-rich petroleum fractions, as a compound capable of a double catalytic role: on the one hand, the improvement of the kinetics of hydrogen transfer therefore of the efficiency of free radical capture; on the other hand, the activation of fragmentation reactions. However, their synergy with hydrogen-donating solvents has been little exploited.

Recent work describes the activating effect of certain thiols (EP 0 175 511) and organic disulphides (benzenethiol, dodecanethiol and atures; diphenyisuifure, etc.) as well as a precursor of hydrogen sulphide, ammonium sulphide. These compounds have the disadvantage of being expensive and of decomposing in part during the heat treatment; they are then not regenerable. In an earlier document, in particular, dimethyldisulfide is used as a promoter of visbreaking in the presence of nickel naphthenate (BE 901 092).

• - le domaine thermique de formation des espèces réactives est trop limité à partir de générateurs tels que l'eau oxygénée, les hydroperoxydes et les peroxydes organiques. Cette température, inférieure en général à 200°C, conduit à une stabilité insuffisante pour leur action efficace dans le milieu aux températures habituellement en vigueur.
• - leur action consiste plutôt en une modification chimique préalable au traitement thermique proprement dit; de plus, une mauvaise sélectivité est observée du fait de la décomposition souvent brutale et exothermique de ces composés;
• - ils présentent une non-régénérabilité potentielle du fait de leur décomposition totale.

Other types of activators have been recommended in the prior art, such as radical generators (US 4,298,455); in general, these additives have various reaction shortcomings, in particular:

• - the thermal domain of formation of reactive species is too limited from generators such as hydrogen peroxide, hydroperoxides and organic peroxides. This temperature, generally lower than 200 ° C., leads to insufficient stability for their effective action in the medium at the temperatures usually in force.
• - their action rather consists of a chemical modification prior to the actual heat treatment; in addition, poor selectivity is observed due to the often brutal and exothermic decomposition of these compounds;
• - they present a potential non-regenerability due to their total decomposition.

Furthermore, the prior art described in patent EP 0 183 269 a mixture of molybdenum-based compounds chosen from the mixture of dithiophosphate and molybdenum carboxylate and the mixture of dithiocarbonate and molybdenum carboxylate.

Finally, US Pat. No. 4,298,455 is known, which mentions the association of azobisisobutyronitrile with sulfur and / or chlorinated compounds.

The object of the invention is in particular to remedy the drawbacks mentioned above.

It has in fact been discovered that the use, in heavy fractions of fossil organic materials to be subjected to heat conversion treatments, of oxidized spaces, more particularly in the form of organic mono-oxides of sulfur, and / or nitrogen made it possible to improve the conversion of these heavy fractions, probably by radical activation (these oxidized species can be added to the heavy fraction to be treated or produced in situ).

The presence of these oxidized species (added or produced in situ) during the heat treatment of the heavy fractions considered, makes it possible in particular to obtain, at lower temperature, conversions similar to those obtained, in their absence, in conventional treatments.

In association with hydrogen donors, these oxidized species make it possible to improve, at the usual temperatures of the heat treatment, the overall conversion of the charges with obtaining a clear reduction in the Conradson carbon and in the asphaltene level. In addition, the synergy observed with the hydrogen donors makes it possible to carry out converting heat treatments at higher temperatures and to obtain a higher conversion without the appearance of coke.

The effectiveness of organic monooxides in the process of the invention is probably due to the action at high temperature of oxygenated species such as nascent oxygen, and / or sulfinyl radicals (RSO-) in the case of sulfoxides, and turns out to be different and significantly superior when use in combination with hydrogen donors.

Another advantage of the process of the invention lies in the fact that some of the organic monooxides involved, after having acted during the heat treatment, can be found in a reduced form, stable at the treatment temperature and can then be recovered for example by distillation to be recycled, after re-oxidation under specific conditions ex situ.

The "heavy fractions" of fossil organic materials considered in the invention may more particularly consist of heavy crude oils, heavy petroleum fractions, refining residues, or even shales or bituminous sands or coal.

The invention applies to various heat treatments, in particular to visbreaking of distillation residue (at temperatures for example of about 350 to 470 ° C, advantageously from 380 to 450 ° C, preferably from 400 to 440 ° C) and at hydroviscoreduction at temperatures of the same order, under pressures which, in general, are between 10 and 150 bars at treatment temperatures with residence times of approximately 1 to 60 minutes.

In general, the invention relates to a process for converting a heavy oil, a heavy petroleum cut or a refined residue, in which said heavy petroleum, said heavy petroleum cut or said refined residue is subjected to a heat treatment, the method being characterized in that the heat treatment considered is carried out in the presence of a minor proportion of at least one oxygenated compound, generator of radicals, containing at least one heteroelement chosen from sulfur and l nitrogen and wherein said heteroelement carries an oxygen atom.

The oxygenated radical-generating compound, generally an organic sulfur, and / or nitrogen monooxide, can be added to the feed to be treated in a proportion of 1 to 50%, advantageously from 1 to 20% and preferably 5 to 15% by weight relative to said load.

The action of the oxygen-containing compound in the process of the invention can be reinforced by the use of a hydrogen donor diluent, generally used in a proportion of 10 to 400%, advantageously from 30 to 200% and preferably 50 to 100% by weight relative to the load to be treated.

• - des oxydes de composés soufrés ayant de 2 à 30 atomes de carbone tel que les dialkylsulfoxydes, par exemple le diméthylsulfoxyde, les diarylsulfoxydes, par exemple le diphénylsulfoxyde, les alkylarylsulfoxydes et les oxydes de soufre thiophénique, par exemple le benzothiophène-sulfoxyde ou le dibenzo- thiophène-sulfoxyde;
• - des oxydes d'amines contenant de 1 à 30 atomes de carbone et de préférence de 1 à 10 atomes de carbone tels que les oxydes de trialkyl- et de triarylamines ou les oxydes d'amines avec au moins un groupement alkyl et au moins un groupement aryl et les oxydes d'azote aromatiques, par exemple le N-oxyde de pyridine ou le N-oxyde de quinoléine.

Among the organic monooxides considered in this process of the invention, there may be mentioned more particularly;

• - oxides of sulfur compounds having from 2 to 30 carbon atoms such as dialkylsulfoxides, for example dimethylsulfoxide, diarylsulfoxides, for example diphenylsulfoxide, alkylarylsulfoxides and thiophenic sulfur oxides, for example benzothiophene-sulfoxide or dibenzo - thiophene sulfoxide;
• - amine oxides containing from 1 to 30 carbon atoms and preferably from 1 to 10 carbon atoms such as trialkyl- and triarylamine oxides or amine oxides with at least one alkyl group and at least one aryl group and aromatic nitrogen oxides, for example pyridine N-oxide or quinoline N-oxide.

At a concentration of atom (oxygen carrier) of sulfur or equivalent nitrogen, it is preferable to use additives of low molecular mass. The dimethyl sulfoxide prepared according to US Pat. No. 3,045,051 has the advantage of being inexpensive and of being a good solvent for oils and diluents which donate hydrogen. Diphenylsulfoxide is more expensive but recyclable, with low severity, from diphenylsulfide resulting from the loss of oxygen (Synthetic communication p.1025, 1981) Didodecylsulfoxide is prepared from didodecylsulfide (Synthésis p.447, 1975), which is then oxidized as described in "Synthetic communication". Pyridine N-oxide, for example, is easily prepared from pyridine which can be recycled (J. of Chem. Soc p.1769, 1957).

To introduce these organic monooxides into the feed to be treated, the substances can be used as they are when they are available. One can also advantageously use hydrocarbon cuts containing sulfur, and / or organic nitrogen in the state of monooxides, produced by specific known oxidative treatments described for example in the publication J. C. Petersen et al, A.C.S., Div. Fuel 26 (4), 898, 1981 and in USSR, SU 1,214,660.

According to another embodiment of the process of the invention, or can produce the oxygenated compounds of sulfur, and / or nitrogen in situ, in the feed to be treated, by implementing a gentle oxidation of the latter, in particular by means of a peroxide (in general hydrogen peroxide, for example in admixture with water or, preferably, with methanol). As the functions treated generally contain sulfur compounds and, in some cases, nitrogen compounds, the mild oxidation produced in the medium mainly by sulfoxides, and in some cases, organic nitrogen oxides according to the invention. The oxygen introduced in this way is then released during the heat treatment.

According to another mode of use, the oxygen compounds of sulfur and / or nitrogen can be produced ex situ in a feed and use this cut as a generator of oxygenated species in the treatment of a heavy cut of petroleum.

Among the hydrogen donor diluents which can be used in association with organic monooxides, mention may be made of those described in patent EP 0 032 019 and advantageously, for example, tetrahydronaphthalene (or "Tetraline"), or dihydroanthracene (DHA), or as in prior art, a partially hydrogenated LCO cut.

The invention also relates to a composition comprising at least one monooxygenated organic compound as defined above, and at least one diluent hydrogen donor as defined above, advantageously tetrahydronaphthalene or dihydroanthracene.

The weight ratio of the hydrogen donor relative to the monooxygenated organic compound in said composition is generally 0.2: 1 to 400: 1 and preferably from 3: 1 to 20: 1.

The proportion by weight of the composition introduced into the filler to be subjected to the heat treatment is usually from 11 to 450 parts per 100 parts of a filler consisting of a heavy fraction of organic matter and preferably from 55 to 115 parts per 100 parts of said charge.

The following examples illustrate the invention and should in no way be taken as limiting.

Figure 1 shows the temperature profile of the analysis method (pyroanalysis), while Figure 2 shows the pyrogram corresponding to the CO ₂ concentration as a function of time or the reference temperature.

Example 1

A first series of tests 1 to 22 relates to a hydroviscoreduction treatment of a residue under vacuum (RSV) 500 ° C ⁺ of Safaniya origin.

Tests 1, 3, 6, 10, 13, 14, 15, and 18 are given for comparison.

The characteristics of the residue are as follows:

Elementary analysis:

• - on chauffe l'échantillon sous atmosphère inerte à une température T₁ et on réalise une combustion par un mélange de gaz (He + 3% 0₂) des effluents de chauffage en présence d'un catalyseur d'oxydation (CuO); les composés d'oxydation, notamment CO₂, sont détectés par exemple par un détecteur à infrarouge; et
• - le résidu restant après chauffage en atmosphère inerte est à son tour oxydé avec le même mélange (He + 0₂ à 3%) jusqu'à une température T₂ et, après passage dans un catalyseur CuO, les composés d'oxydation du résidu (carbone résiduel) sont détectés par le même type de détecteur et les signaux traités par un calculateur.

The untreated vacuum residue and the liquid fraction resulting from the hydroviscoreduction were analyzed by pyroanalysis. This method includes the following steps:

• the sample is heated under an inert atmosphere to a temperature T ₁ and combustion is carried out with a mixture of gases (He + 3% 0 ₂ ) of the heating effluents in the presence of an oxidation catalyst (CuO); the oxidation compounds, in particular CO ₂ , are detected for example by an infrared detector; and
• - the residue remaining after heating in an inert atmosphere is in turn oxidized with the same mixture (He + 0 ₂ to 3%) up to a temperature T ₂ and, after passage through a CuO catalyst, the oxidation compounds of the residue (residual carbon) are detected by the same type of detector and the signals processed by a computer.

• V_A = V_C = 20°C/mn; V_e = 30° C/mn; V_G = 100°C/mn
• t_A=11 mn, t_B = 10 mn, t_e 6 mn; t_D = 10 mn, t_e = 12 mn,
• t_F=1 mn, t_G = 2 mn, t_H = 2 mn.

The heating temperature profile is as follows (Figure 1):

• V _A = V _C = 20 ° C / min; V _e = 30 ° C / min; V _G = 100 ° C / min
• t _A = 11 min, t _B = 10 min, t _e 6 min; t _D = 10 min, t _e = 12 min,
• t _F = 1 min, t _G = 2 min, t _H = 2 min.

Points P ₁ and P ₂ correspond to n-alkanes heated under the same conditions and whose boiling points are equal to 500 ° C and 620 ° C respectively. From point P _3, the combustion of the residual carbon takes place.

Les fractions F₂ et F₃ représentent la fraction 500°C- fin de distillation dans les tableaux ci-dessous.The pyrogram obtained (Figure 2) delivers the CO ₂ concentration as a function of the time or the temperature of the oven. We can calibrate the abscissa scale in boiling temperature of reference compounds (n-alkanes for example), heated under the same conditions. You can easily split the pyrogram by integrating the signal between selected temperature values, for example according to the fractions below. In the case of the untreated vacuum residue, the percentages of the various fractions are given below:

The fractions F ₂ and F ₃ represent the fraction 500 ° C - end of distillation in the tables below.

By calibrating the response of the detector it is easy to obtain the carbon weights corresponding to the above fractions. Similarly, the percentages and weights of hydrogen and sulfur contained in the sample are obtained simultaneously with those of carbon.

The centesimal analysis of the charges subjected to hydroviscoreduction shows that the sum of the weights of C, H and S is always greater than or equal to 95%. Consequently, the simple addition of these weights makes it possible to obtain with sufficient precision the actual respective percentages of the various above fractions of the liquid fraction.

This analysis method is used for all tests 1 to 22 described in the invention.

The concentrations by weight of sulfur compound are such that the level of sulfur introduced expressed in% weight by weight relative to the feed is identical in each test, that is: 0.213 mole of sulfur per 100 g of residue under vacuum Safaniya.

The petroleum charge (RSV Safaniya) (approximately 30 g), after slight heating (100―120 ° C) to make it less viscous, is introduced into the reactor which is a stainless steel autoclave. Any additives are added after cooling. The whole is constantly agitated.

All the hydroviscoreduction tests were carried out under an initial pressure (at 20 ° C) of 50 bars of hydrogen, at high severity, at 430 ° C for 15 minutes in the presence of hydrogen donor and monooxidized compound and at low severity at 390 ° C., in the presence of a monooxidized compound alone, after a time of rise to the hydroviscoreduction temperature of approximately 25 minutes.

The weights chosen by way of example as a hydrogen donor diluent (DDH) are related to the charge comprising 50% of DDH and 50% of RSV to which a quantity of sulfur-containing additive is added such that it represents 0.213 atoms of sulfur per 100 g of residue.

In the simultaneous presence of DDH and of the monooxidized compound of sulfur and nitrogen, the concentrations of Weight relative to RSV are identical to those used with the additives alone.

• - une phase solide, le coke,
• - une phase liquide contenant une partie des produits initiaux ou des produits de craquage, et
• - une phase gazeuse.

After the visbreaking treatment, we generally obtain a multiphase system:

• - a solid phase, coke,
• a liquid phase containing part of the initial products or of the cracking products, and
• - a gas phase.

The liquid products and any coke are collected directly or by dissolution in benzene, this operation being followed by evaporation; the gases are not recovered but are calculated by difference between the quantities introduced and collected.

Coke is defined as the part insoluble in hot benzene. An assay is carried out for each test. The amount of liquid is calculated after determining the coke level.

• - un additif tel que la tétraline (TET) est, après pyrolyse, contenu intégralement dans la fraction liquide de laquelle il est déduit.
• - Le diméthylsulfoxyde est totalement converti (confirmé par dosage en chromatographie en phase gaz) en eau, méthane et hydrogène sulfuré. L'eau est déduite de la fraction liquide, les deux autres composés de la fraction gazeuse.

The gas, liquid and coke rates are expressed relative to petroleum alone after deduction of the additives. Two examples of deduction are presented below, with the following remarks relating to the additive (DDH) and to the monooxygenated sulfur compound:

• - an additive such as tetralin (TET) is, after pyrolysis, contained entirely in the liquid fraction from which it is deduced.
• - Dimethyl sulfoxide is completely converted (confirmed by metering by gas phase chromatography) into water, methane and hydrogen sulfide. Water is deducted from the liquid fraction, the other two compounds from the gaseous fraction.

The conversion of petroleum during hydroviscoruction is obtained in the following way (example of assay 12):

Step 1 Calculation of oil distribution between phases

The load subjected to visbreaking comprises 50 g of RSV Safaniya + 41.7 g of tetralin + 8.3 g of dimethyl sulfoxide, ie 100 g in total.

After treatment, 0.5 g of coke (insoluble benzene from the liquid fraction) and 91.9 g of overall liquid fraction are isolated. By difference at 100 g, the weight of the overall gas fraction is deducted, ie 7.6 g. The gas is composed of H2S and CH4 from DMSO, ie 6.6 g, therefore the weight of the petroleum cracking gas is 1 g. The petroleum liquid fraction consists of 91.9 g - 41.7 g (tetralin) - 1.7 g (oxygen from DMSO being in the form of water), or 48.5 g from the visbreaking of petroleum.

These results provide the gas / liquid / coke distribution of the water-reduction reduction recipe (deducted additives), namely:

2nd step Calculation of oil conversion

By pyroanalysis we measure the percentage of the overall liquid fraction having a boiling point below 500 ° C, or 74.2% taking into account the additives (tetraline and DMSO) in the case of test 12. This therefore represents 91.9 x 74.2 = 68.2 per 100 g of the initial charge. After deduction of 41.7 g of tetralin and 1.7 g of water, 24.8 g of petroleum are obtained having a boiling point below 500 ° C. in the liquid fraction.

The RSV Safaniya already having 6% fraction 500 ° C-, this represents 3 g for the 50 g of petroleum involved. They are therefore deducted from 24.8 g to give 21.8 g of liquid 500 ° C- and finally the weight of gas is added to result in the weight of 22.8 g of 500 ° C. created by the hydroviscoreduction.

The conversion is therefore (22.8 x 100) / 50 = 45.6%.

This calculation method is valid for all tests 1 to 22.

Table 1 summarizes the results of tests 1 to 7, carried out at a hydroviscoreduction temperature of 390 ° C.

The addition of dimethylsulfoxide (test 2), didodecylsulfoxide (test 4), diphenylsulfoxide (test 5), pyridine N-oxide (test 7) to the residue (RSV) contributes to improving the conversion of petroleum at 500 ° C. - compared to that carried out on the residue alone (test 1). By respective comparison, the additives such as dimethylsulfide (test 3) or diphenylsulfide (test 6) added to the residue contribute to results where the values of the conversion at 500 ° C. and of the distribution of the oil are substantially identical to those obtained on the vacuum residue.

Table 2 reports the results of tests 1 and 8 to 15 corresponding to a hydroviscoreduction temperature of 430 ° C.

The RSV alone (test 1) has a conversion of 47.2% and respective coke and gas levels of 6.6 and 7.8% by weight. The introduction of DMSO into the residue (tests 8.9) brings the conversion to a high level and makes it possible to obtain a higher level of coke and of gas, reflecting an interesting converting effect.

The introduction of tetralin into the RSV residue (test 10) results in an inhibition of the formation of coke and of gas but a limited conversion.

The combination of tetralin and DMSO (tests 11 and 12) makes it possible to gain in quality and to maintain the level of coke and of gas substantially at the level of Example 10 and also contributes to a favorable effect on the conversion.

By way of comparison, test 15 according to the prior art with a sulfur content comparable to that of test 12 carried out according to the invention, shows that the combination of thiophenol and tetralin contributes to a significantly lower conversion and to a better quality of the recovered oil (see gas and liquid rate as well as the distribution in fractions 40-500 ° C of the liquid fraction). Test 14 for its part shows the contribution of thiophenol alone, at a sulfur concentration substantially identical to that of tests 8 and 15.

Finally, by way of comparison, test 13 is also given where the combination of tetralin and dimethylsulfide (with substantially identical sulfur content) does not lead to the good results of Example 12 according to the invention.

Table 3 summarizes the results of tests 1, 10 and 16 to 22.

By tests 16 and 17, which are compared with tests 1 and 10, it is shown that the diphenylsulfoxide contributes essentially to a better conversion, that the association tetraline and diphenylsulfoxide contributes both to a good conversion and to a good distribution of the petroleum. , these results being better than those observed on the combination of tetralin and diphenyl sulfide (test 18).

Tests 21 and 22 show the influence on the one hand of didodecylsulfoxide and on the other hand that of didodecylsulfoxide and tetralin where the effect on both the conversion and the distribution of petroleum is always observed.

Finally, the addition of pyridine N-oxide and of the pyridine N-oxide and tetralin combination according to the invention (tests 19 and 20) makes it possible to respectively improve the conversion and the whole conversion and quality of the oil recovered (tests compare with tests 1 and 10) but in a more limited way.

Tetralin was used as the hydrogen donor diluent but it was noted that with other hyrogen donors such as dihydroanthracene, used under the same conditions, substantially the same results were observed.

It has also been shown that substantially similar results can be obtained, particularly at the level of low gas and coke levels in visbreaking units operating in dynamics.

Example 2

A second series of tests 23 to 30 relates to visbreaking treatments of an atmospheric residue of BOSCAN origin. Tests 23, 25, 27 and 39 were carried out for comparison.

• le % poids d'asphaltènes: 27,_5%
• et la viscosité à 100°C: 2500 cP (mPa.s).

Certain characteristics of the atmospheric residue used, denoted in the RAB series, are given in Tables 4, 5 and 6 below. Table 4 gives in particular:

• the% weight of asphaltenes: 27.5 _%
• and the viscosity at 100 ° C: 2500 cP (mPa.s).

Table 6 gives the basic analysis of the RAB.

Tables 4 and 5 give the percentages of the fractions 100―500 ° C, 500―570 ° C, 570 ° C ^* and of the residue (residual peak) obtained by the pyroanalysis method already described above in connection with tests 1 to 22.

The atmospheric residue was subjected to gentle oxidation using hydrogen peroxide according to the procedure described below.

20 g of atmospheric residue of BOSCAN origin are dissolved in 450 ml of a 50/50 mixture by volume of methanol and benzene. 6.5 ml of a 30% aqueous solution of hydrogen peroxide (H ₂ 0 ₂ ) are added to at least 110 volumes, which corresponds to 0.076 mole of H ₂ 0 ₂ , ie a molar ratio H ₂ 0 ₂ / sulfur of 2.3.

The solution is then brought to reflux (70-75 ° C) for 15 hours, then cooled to 20 ° C. Decanting is carried out. The solution is then washed twice with water and dried by azeotropic distillation and then evaporated to dryness.

Some of the characteristics of the oxidized atmospheric residue obtained, denoted in the following RAO, are given in Tables 4, 5 and 6 can be compared with those of the atmospheric residue before oxidation.

We have preceded tests of visbreaking under hydrogen pressure (visbreaking) and visbreaking with water.

The technique used is that of pyrolysis in a closed reactor under hydrogen or steam pressure, as the case may be.

The temperature and pressure inside the reactor are controlled by sensors linked to a computer which ensures data acquisition and automatic piloting of the reactor. The pressure and temperature ranges are 0-60 bar and 0-600 ° C, respectively. The pressure is ensured by the addition of 30 cm3 of water or by an initial hydrogen pressure of 20 bars.

The desired temperature is reached after about twenty minutes, the duration of the plateau is fifteen minutes. The temperature level pressure is then about 40 bars for the tests under hydrogen and 20 bars for the tests in the presence of water.

The liquid fractions are collected in benzene; the optional coke is separated by filtration in hot benzene. In the water tests, the aqueous phase is separated by decantation or by entrainment with Dean-Stark, which ensures effective drying of the organic phase.

In Table 4, the viscosity, merit and asphaltene values of the various tests are indicated.

The merit, rated from 1 to 10, results from a spot test carried out on filter paper making it possible to determine the concentration of isooctane in an isooctane-xylene mixture from which the coke or the flocculation of asphaltenes appears. For example, the merit value will be 8.5 for a mixture of 85% xylene and 15% isooctane.

The gas rate corresponds approximately to a fraction 100 ° C- and results from the weight loss after evaporation of the benzene which is the recovery solvent.

The visbreaking temperature is fixed at 420 ° C. which corresponds to obtaining a satisfactory stability recipe (merit = 7, in test 23).

The recipes of tests 23, 24, 25 and 26 are analyzed according to a technique called "pyroanalysis", as described above, which gives in particular access to the residual peak values and to the conversion rates.

The temperature rise program for this pyroanalysis is as follows:

20 ° C / min for 22.5 min of heating in an inert atmosphere and 100 ° C / min for 2.5 min of combustion of the residue. The boiling points of n-alkanes at 500 ° C and 570 ° C correspond to heating times of 13.5 min and 16 min.

The conversion rates are calculated by the difference between the 100 ° ―500 ° C fraction of the recipe and that of the initial RAB, plus the gas rate. For example, the conversion rate for trial 23 is equal to:

Table 5 gives the percentages of the different fractions of the liquid phase and Table 6 gives the percentage analyzes (C, H, N, 0, S, metals) of the liquid phase.

In tests 25 and 26, 15% by weight of dihydroanthracene (DHA) was used. The weight of DHA has been deducted whenever this is possible: for the% 100 ,500 ° C, the% of asphaltenes, the% C and H of the centesimal analyzes.

The viscosity is measured over the entire petroleum + dihydroanthracene recipe at a temperature of 60 ° C.

The comparison of tests 23 and 24 leads to the following remarks:

Under the same temperature conditions, we find the phenomenon of advance coking. With the oxidation pretreatment, there is 8% of coke and the liquid has a higher viscosity, a residual peak and a level of asphaltenes than with the unoxidized RAB (170 cP against 115 cP; 33.3% of asphaltenes C _s against 26%).

On the other hand, the atomic ratio H / C goes from 1.54 for the initial RAB, to 1.41 for test 23 and to 1.34 for test 24, which shows the hydrogen depletion due essentially to the formation of gases, the content of which is very important for the visoreduced RAO (14.5%).

Indeed, test 24 has a higher conversion rate than that of test 23, but this increase is essentially due to the increase in the gas rate.

Tests 25 and 23 in Table 5 indicate that the dihydroanthracene used RAB does not act on the formation of light products (practically identical conversion rate), but rather on the heavy fraction: the rate of asphaltenes and the content of the residual peak are falling. The visbreaking residue has a satisfactory even improved stability with a merit of 6.5 and is richer in hydrogen (the atomic ratio H / C which is 1.55, that is to say equal to that of the initial RAB, confirms the ability of the DHA to be a very good inhibitor of dehydrogenation). The comparison between tests 24 and 26 indicates that the presence of the hydrogen donor with the oxidized RAB makes it possible to completely avoid the formation of coke and also to maintain a significant conversion gain compared to the non-preoxidized RAB, while having a visbreaker liquid with good stability.

The conversion gain is due to an increase in the fraction 100-500 ^° C. and no longer to an increase in the gas rate.

Stability is satisfactory; it manifests itself by residual peak contents and especially fairly low asphaltenes (18.4% and 20.3% respectively). In addition, the viscosity is lower than that of the RAB-DHA mixture pyrolyzed under the same conditions, but not preoxidized (330 cP at 60 ° C against 420 cP for test 25).

In general, the centesimal analyzes of sulfur and metals do not show any change for the hydroviscoreduction tests (Table 6).

The comparison between tests 25 and 26 shows the advantage of the oxidative pretreatment associated with a diluent hydrogen donor; this results in a better conversion of the heavy fraction (% of asphaltenes,% 570 "C decreasing) into recoverable liquid which has a lowered viscosity and a satisfactory stability.

The results of the visbreaking tests under water vapor pressure (P = 20 bars at 420 ° C) at RAB and RAO in the presence or not of the hydrogen donor are shown in Tables 7, 8 and 9.

As in water reduction, the oxidative pretreatment (test 28) results in an increase in the viscosity reduction (high viscosity) recipe but no coke) and a gain in conversion compared to test 27. A 30% increase in the conversion ( the rate goes from 18 to 24%) and due for the increased formation of the gas and for half, with the fraction 100―500 ° C.

The study of the distribution of the liquid phase of test 28 compared to that of test 27 shows that approximately 15% of the fraction 500-570 ° ⁺ C (48.3% to 41.4%) are transformed by disproportionation to form on the one hand, lighter products, responsible for the conversion, and, on the other hand, heavier products.

Analysis of the metals (vanadium and nickel) shows that the heat treatment of the oxidized charge provides good demetallization, since more than half of the nickel and vanadium in place is eliminated in the aqueous phase, while test 27 gives , after extraction, a demetallization of approximately 25%. Oxidation with hydrogen peroxide in the presence of methanol does not give direct demetallization.

The comparison of tests 27 and 29 shows a weak role of dihydroanthracene on the RAB itself. The high value of merit for test 18 (merit = 8) is due to the presence of the DHA / antracene mixture which distorts the validity of the spot test. On the other hand, the action of DHA on the RAO increases the gain in conversion compared to test 29 by more than 50% (the conversion rate increases to 28.1%), of which only a small part is due to the gas rate increase. It is always the fraction 500-570 ° ⁺ C which is responsible for this modification, but the introduction of DHA in oxidized petroleum makes it possible in particular to act very strongly on the fraction 570 ° ⁺ C which sees its reduced importance of a third (from 2.5% to 17.3%).

Thus, visbreaking without diluent hydrogen donor of preoxidized RAB brings about a conversion gain, but gives a less stable visbreaking recipe.

The use of dihydroanthracene allows a much higher gain in conversion compared to the visbreaking of the non-oxidized RAB / DHA mixture, DHA acting more particularly on the 570 ⁰⁺ C fraction.

The oxidative pretreatment with H ₂ 0 ₂ / CH ₃ 0H associated with a hydrogen donor diluent, is favorable in the two visbreaking cases (tests 30 and 26). The gain in conversion is proportionally greater in visbreaking with water, which gives a recipe (test 30) having a percentage of 500 ° "C and a viscosity comparable to those obtained in visbreaking. But the quality of the visbreaking liquid for l 'test under hydrogen pressure (test 26) is higher: asphaltenes rate and percentage of residual peak lower, respectively 20.3% against 27% and 18.4% against 24.3%.

Another advantage of visbreaking with water of preoxidized oils is based on the elimination of the subsequent aqueous phase which allows demetallization up to 60% thanks to the oxidation pretreatment (test 28).

Claims (12)

1. Process for the thermal conversion of a charge consisting of a heavy fraction of organic materials, said process comprising subjecting said fraction to a thermal treatment in the presence of a minor proportion of at least one radical generating monooxygenated organic compound, selected from the group comprising the sulfur oxides and the nitrogen N-oxides and in which the oxygen is borne by the sulfur and/ or nitrogen atom, said monooxygenated compound being employed in the proportion of 1 to 50% by weight with respect to the heavy fraction.

2. Process according to claim 1, wherein the sulfur oxide is a dialkylsulfoxide, a diarylsulfoxide, an alkylarylsulfoxide and a thiophenic sulfur oxide, wherein the nitrogen N-oxide is a trialkylamine oxide, a triarylamine oxide, an amine oxide having at least one alkyl group and at least one aryl group and an aromatic nitrogen oxide.

3. Process according to any one of claims 1 to 2, wherein said oxygenating compound is dimethylsulfoxide, diphenylsulfoxide, didodecylsulfoxide, thiophene oxide or benzothiophene oxide, or a hydrocarbon fraction containing sulfur and/or nitrogen, oxygenated ex situ.

4. Process according to any one of claims 1 to 3, wherein said oxygenated compound, reduced after heat treatment, is separated, regenerated by oxidation ex situ and recycled into the charge.

5. Process according to any one of claims 1 to 4, wherein before the thermal treatment said heavy fraction is subjected to gentle oxidation by at least one peroxide, preferably the hydrogen peroxyde.

6. Process according to any one of claims 1 to 5, wherein at least one hydrogen donor diluent is used in addition.

7. Process according to claim 6, wherein said hydrogen donor diluent is used in a proportion comprised between 10 and 400% by weight with respect to said charge.

8. Process according to claim 7, wherein said hydrogen donor diluent is tetrahydronaphthalene or di- hydroanthracene, or a hydro-aromatic petroleum fraction, such as a partially hydrogenated LCO. fraction.

9. Process according to any one of claims 1 to 8, wherein said thermal treatment consists of a vis- breaking or a hydrovisbreaking.

10. Composition useful for practising the process according to any one of claims 1 to 9, said composition comprising on the one hand, at least one radical generating monooxygenated organic compound selected from the group comprising the sulfur oxydes and the nitrogen N-oxides and in which the oxygen is borne by the sulfur and/or nitrogen atom and on the other hand at least one hydrogen donor diluent, the ratio by weight of said hydrogen donor with respect to the oxygenated organic compound is form 0.2:1 to 400:1.

11. Composition according to claim 10, wherein the hydrogen donor diluent is tetrahydronaphthalene, dihdyroanthracene or a hydroaromatic petroleum fraction.

12. Composition according to any one of claims 10 to 11, wherein said monooxygenated compound is a sulfoxide selected from the group consisting of dialkylsulfoxides, diarylsulfoxides, alkylary sulfoxides, and thiophenic sulfur oxides, and in which said compound is a nitrogen oxide selected from the group consisting of trialkylamine oxides, triarylamine oxides, oxides of amines having at least one alkyl group and at least one aryl group and aromatic nitrogen oxides.

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