ITRM20060581A1 - STABILIZING ADDITIVE FOR FUEL OIL - Google Patents

Description

2 0 06 A 0 00581

SIB BI3756R

Description of the industrial invention entitled: "STABILIZING ADDITIVE FOR FUEL OIL" in the name of CHIMEC S.p.A. of Rome (Italy)

DESCRIPTION

Field of the invention

The present invention relates to additives for the stabilization of fuel oil, compositions containing them and processes for their use, in particular in the stabilization of fuel oil leaving Visbreaking plants (VSB).

State of the prior art

Visbreaking (VSB) is a thermal conversion process that is applied to petroleum distillation residues, otherwise destined for bitumen or fuel oil (products notoriously of low commercial value), to partially convert them into lighter products of greater value. The conversion makes it possible to partially obtain distillate products, such as gas, petrol, kerosene, diesel oil, and partially a residue (hereinafter also referred to as tar or TAR), which can still form the basis for use as oil.

Fuel fi. The conversion process is carried out in such a way as to maximize the yield in distilled products, lowering the overall yield in tar oil. It should be noted that already a conversion increase equal to 1% of the charge treated is to be considered extremely satisfactory in terms of economic yield.

The VSB plant includes the following parts: a train of exchangers into which the feed charge to the VSB enters, for preheating; an oven in which the actual thermal cracking takes place; a fractionation column, from whose head the distillates are extracted and from the bottom of which the residue (TAR) comes out. This residue passes through the exchangers, yielding part of its heat to the feed charge and is stored in tanks. It is possible to provide a Soaker and a Preflash column between the oven and the fractionation column.

The operating conditions of the VSB can be briefly described as follows: a charge, generally consisting of a residue of primary distillation or vacuum, is introduced into the oven which operates at temperatures ranging from 420 ° C to 500 ° C and at pressures included between 3 bar and 20 bar. The charge thus treated passes to the fractionation column, which operates with known procedures; from it can be obtained, for example in the following proportions: light distillates (gas and petrol, 3-10%), middle distillates (kerosene and gas oil, 15-20%) and the residue (TAR, 65-75%); % are by weight with respect to the total of products leaving the VSB. The TAR, present in a higher rate than the other components, to be used as fuel oil, must comply with the specifications imposed by the market, for example those indicated in Table 1.

TABLE 1

SiB - Italian Patent Society

* Required by Italian law

** Viscosity ° E at 50 ° C above 12 and diluted ASTM color min 4.0;

*** IP: The Institute of Petroleum (recognized standard method);

**** SAA: Atomic Absorption Spectrophotometry Usually the plant is managed in such a way that the TAR obtained, except for slight viscosity corrections, already satisfies the specifications required as fuel oil, therefore in the following "TAR" and "oil fuel "will be considered synonyms for the purposes of the present invention.

The ASTM D4870 method for the determination of HFT is attached

The previous patents EP-B-0321424 and EP-B-0818524 (Chimec Spa), describe methods for decreasing the quantity of TAR produced, with the same quantity of Visbreaking filler. That is to say, increase the yield in light distillates (products with high

SiB - Italian Patent Company) by decreasing the quantity of residual product (low value). To do this it is necessary to raise the temperature of the VSB furnace, and in any case, in general, to raise the severity of the march. In addition to the teaching contained in the patent, this is currently a general trend, as it leads to the production of greater quantities of valuable products and therefore to a high economic efficiency of the plant. However, conducting the VSB plant to the maximum possible severity involves some drawbacks due to the formation of greater carbon residues and fouling compounds (due to polymerization and dehydrogenation phenomena, consequent to the increase in process temperatures). Furthermore, it has been verified that in some situations, the tar produced with high severity has the drawback of not being stable over time, which jeopardizes its sale as fuel oil complying with commercial specifications.

The fuel oil, which leaves the VSB plants, is stored in tanks, where it is kept at a temperature between 70 and 110 ° C, until it is pumped into the tank or when it arrives in the burners. This time can be a few weeks.

’T'-iL ·; -,;. v <'> · ·. 1 701 ίί During these manipulations the oil can come into contact with the air and is subjected to heat, conditions which, combined with the variable time, can favor the formation of insoluble compounds in the oil itself.

In fact, it has been noted that over time, i.e. during storage in the tank, the fuel oil exhibits aging phenomena which are highlighted with a progressive increase in the HFT value (index of the presence of sediments), even in a very short time of the order of a few days, the fuel oil-out of specification. The aged TAR no longer meets the specifications imposed by the markets and its viscosity increases, as the value of HFT increases. -This translates operationally, at the time of use (combustion), in the occurrence of the following problems:

- Abundant formation of coke in preheaters, due to the coking of heavy carbonaceous materials

- Abundant formation of soot produced by incomplete combustion of heavy insoluble, precipitated compounds

- Sediments, paraffins and rubber-like substances

hjin Br found on the lines of the combustion system The solutions that can be adopted to date to counteract the instability of the TAR all have drawbacks. For example, it is possible to lower the outlet temperature of the VSB furnace, but this entails a lower production of light (valuable) products, or the TAR can be mixed with suitable distillates, for example with diesel oil, in order to counteract the separation of the compounds. insolubles present in oil, but in this way a product with low added value is diluted with other products with higher added value. Therefore, in both cases, the solutions that can be adopted have too high a cost. It follows that the problem of an effective and at the same time economically advantageous stabilization of the TAR as fuel oil remains unsolved.

The purpose of the present application is therefore to offer new advantageous solutions to the problems seen above

Summary of the Invention

The present invention is based on the unexpected discovery that compounds belonging to the class of stable free radicals can be used as additives capable of stabilizing during

YES ibi English E »storage of fuel oil and to counteract the formation of insoluble compounds in it. The object of the present invention is therefore a stabilizing composition soluble in fuel oil containing at least one compound belonging to the class of stable free radicals, selected from nitroxides and dinitroxides, and a solvent, or a mixture of solvents, capable of maintaining stably in solution in the range temperature between -10 ° C and 50 ° C, called compound. Preferably the fuel oil is the residue or tar of the Visbreaking thermal conversion process

(VSB).

A second object of the invention is a stabilization method of fuel oils, such as those based on the residue (tar) of the Visbreaking thermal conversion process (VSB), comprising a step in which the composition of the invention is added to the oil in quantity between 1 and 2000 ppm with respect to fuel oil, for example between 100 and 600 ppm with respect to fuel oil.

A third object of the invention are stabilized fuel oils obtained in accordance with the method of the invention.

Further objects are procedure and plant

òiB - Soci »· Hnliana i + 3⁄4v., .i thermal conversion for the production of petroleum distillates, such as plants for conducting Visbreaking processes, including an addition station to the distillation residue (tar) of the stabilizing compositions according to the invention on the line between the column and the storage tank.

The compositions of the invention confer to the distillation residue (tar), and therefore to the fuel oil obtainable from this, surprising characteristics of storage stability, low viscosity, low content in solid fraction as demonstrated in detail in the experimental part of the application. These advantageous properties increase the intrinsic and commercial value of the product.

Detailed description

For the purposes of the present invention, by stabilizing additive, compound or composition is meant an additive, compound or composition capable of influencing at least one of the parameters normally considered as indicative of the stability of the residue or tar of a thermal conversion process of petroleum. These parameters are 1 'HFT (Hot Filtration Test) or index of the presence of

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sediments. The parameter is determined by carrying out the ASTM D4870 method described in detail in the examples and must not have a value greater than 0.30% w / w. Higher values indicate levels outside the commercial specifications of the solid fraction contained in the oil and the viscosity of the oil. A second parameter is the PV which is the stability index of asphaltenes placed in flocculation conditions. This parameter is calculated according to the SHELL method. In normal running conditions of a Visbreaking process the parameter value is 1.1. Lower values reflect a decreased stability of the residue.

The stabilizing compositions of the invention comprise as an essential component one or more stabilizing compounds capable of counteracting the increase in the HFT value during storage. These belong to the class of stable free radicals and in particular to the class of nitroxides or dinitroxides, containing a free radical in their molecule.

The nitroxides of the invention are compounds having the following general formula (I):

- s-ocreta itsIL-nj 8; and go

Formula 1}

where the substituents R, R ', and R "represent a group selected from H; (C1-C15) alkyl, for example methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, tert-butyl , pentyl, hexyl; (Cl-C15) cycloalkyl, for example cyclobutyl, cyclopentyl, cyclohexyl; (C1-C15) aryl, for example phenyl, benzyl, naphthyl, or where two symmetrical substituents [R] or [R '] or [ R "] together form a cyclic nucleus, all substituted or unsubstituted with heteroatoms such as 0, N, S, P or halogens. Alternatively, the compound belonging to the stable free radical class is a dinitroxide or a trinitroxide, or mixtures of all the above compounds. Examples of compounds usable in the present invention are:

4-hydroxy-1-oxyl-2,2,6,6-tetramethylpiperidine (40H TIME);

4-ethoxy-1-oxyl-2,2,6,6-tetramethylpiperidine;

4-propoxy-1 -oxyl-2,2,6,6-tetramethylpiperidine;

SiB - Sociotà tal .ina Srs <3⁄4>: iii 4-acetamido-1-oxyl-2,2,6,6-tetramethylpiperidine; l-oxyl-2,2,6,6-tetramethylpiperidine (TEMPO);

1-oxyl-2,2,6,6-tetramethylpiperidin-4-one (OXO TEMPO);

1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl acetate; 1-oxyl-2, 2,6,6-tetramethylpiperidin-4-yl-2 ethylhexanoat and;

1-oxyl-2, 2,6,6-tetramethylpiperidin-4-yl stearate; 1 -oxyl-2,2,6,6-tetramethylpiperidin-4-yl benzoate; 1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl 4-t-butylbenzoate;

N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) caprolactam;

N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) dodecylsuccinimide;

4,4'-ethylenebis (1-oxyl-2,2,6,6tetramethyl piperazin-3-one};

2-oxyl-1,3,3-tetramethyl-2-isobenzazole;

1-oxyl-2,2,5,5-tetramethylpyrrolidine;

bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) sebacate;

bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) succinate;

bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) adipate;

bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl), nbutylmalonate;

bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl) phthalate;

bis {1-oxyl-2, 2,6,6-tetramethylpiperidin-4 -yl) isophthalate;

bis (1-oxyl-2, 2,6,6-tetramethylpiperidin-4-yl) terephthalate;

bis (1-oxyl-2, 2,6,6-tetramethylpiperidin-4-yl) hexahydroterephthalate;

N, N '-bis (1-oxyl-2,2,6,6-tetramethylpiperidin-4 -yl} adipamide;

N, N-bis- (1,1,3,3-tetramethylbutyI) nitroxide;

2,4,6-tris- [N-butyl-N- (1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)] -s-triazine.

Preferred nitroxides or dinitroxides are:

4-hydroxy-2, 2, 6.6 tetramethyl-piperidin-N-oxyl (-40K TIME); bis (1-oxyl-2,2,6,6-tetramethylpiperidin - 4 yl) sebacate; 2.2, 6.6 tetraraethyl-piperidin-N-oxyl (TIME); 1-oxyl-2, 2,6,6 tetramethyl-piperidin-4-one (0X0 TIME); 4-acetamido-2, 2,6, 6 tetramethylpiperidin-N-oxyl.

An essential condition of the free radical compound is that it be soluble in the residue (tar) or in the fuel oil at the various operating temperatures to which the residue or the fuel oil is subjected during preparation or storage. The compound must preferably be soluble in the temperature range between 50 ° C and 300 ° C, in particular between 70 ° C and 110 ° C, the storage temperature of the fuel oil.

The compounds of the invention are known to those skilled in the art (see WO-A-00/36052) and all commercially accessible from Sigma Aldrich Corporation or A.H. Marks and Company Limited (UK). The compositions object of the invention further comprise a solvent or a mixture of solvents suitable for solubilizing and maintaining stably in solution the free radical compound in a wide temperature range, ie at least between -10 ° C and 50 ° C. Examples of usable solvents are water, alcohols, glycols, glycol-ethers, aromatic solvents and their mixtures, such as: water, 2-butoxyethanol, iso-octyl alcohol, iso-butyl alcohol, isopropyl alcohol, methyl alcohol, toluene, ortho-meta and para-xylene, ethylbenzene or mixtures thereof. The compound belonging to the class of stable free radicals is present in the composition in any percentage quantity

Company i & lians or * 'suitable for achieving the desired stabilizing effect, for example between 0.1% and 50% w / w of the composition.

The stabilization method according to the invention provides that the stabilizing composition is added to the tar or fuel oils in a quantity ranging from 1 to 2000 ppm with respect to the product to be stabilized. Advantageous results have been obtained using quantities ranging from 50 to 600 ppm. Preferably, the addition of the composition is on the tar coming out from the bottom of the VSB column on the line that goes to the storage tank. The stabilized product thus obtained, whether tar or fuel oil, maintains the specific characteristics imposed by the market and by the provisions of the law as indicated in table 1 and with extremely low additional costs. In concrete terms, its combustion causes low coke formation in the preheaters, low soot formation and reduced gummy paraffinic sediments in the ducts of the combustion systems.

The use of the stabilizing compositions of the invention has a positive impact on the conduct of the entire Visbreaking process.

kdhna In fact, another important advantage offered by the invention is the possibility of increasing the conversion, increasing the severity of the process, and therefore of improving the yield of high value products, without however losing in terms of the quality of the tar produced. In fact, the conversion increase obtainable for example through temperature increase would be negatively balanced by a downgrading of the tar produced, if this were not stabilized with the compositions of the invention. In other words, the advantage of a higher yield of valuable products would be nullified by the fact that the tar would not reach the expected specifications and therefore would not have the commercial value normally expected.

For this reason, the practical realization of the invention implies the modification of the known plants for the management of the classic Visbreaking processes with the introduction of a station equipped with suitable introduction devices, such as a special detachment from the tar line, equipped with valves. safety, a line dedicated to the product, an additive pump and a storage tank, which allow the addition of the stabilizing composition directly to the

SiB - .wcmt * l'-iliana Tar patents leaving the VSB column on the line between the column and the tar storage tank. Thanks to the invention, the Visbreaking method itself is advantageously modified with respect to its usual embodiment by providing the additional step of adding the stabilizing composition.

The invention is described below in all experimental details in the following examples, which have an illustrative but not limitative purpose.

EXPERIMENTATION

Example 1: determination of the HFT test

The HFT method involves hot filtration (100 ° C, maintained through a thermostatic jacket heated by steam), on Grade GF / A glass fiber filters, of an aliquot of the tar (approx. 10 g) to be analyzed. Filtration is carried out under vacuum and the sediments remaining on the filter are washed with a mixture of solvents (85% n-heptane and 15 3⁄4 toluene). The deposit is weighed and related to the weight of filtered tar: the result is expressed as a percentage of sediment left on the filter. Example 2:

The tar samples obtained for VSB taken after raising the furnace outlet temperature

Sia- liulnnaÙÌ-JVCÌÌÌ (TUF) of 3 ° C and 6 ° C with respect to the temperatures normally maintained were stabilized with a composition A formulated as follows:

20% of 40H-TEMP0 and 40% 2-butoxy-ethanol and 40% iso-octyl alcohol. To age the TAR we followed a standard procedure foreseen by the ASTM D 4870 A method and a more severe non-standard procedure where the aging at a temperature of 70 ° C is prolonged for 96 hours.

1) TAR VSB at TUF 3 ° C

The tar sample taken with an increase in the TUF of 3 ° C was stabilized obtaining a containment of the HFT below 0.3% even in severe aging conditions.

The blank used as the comparison term is the same sample without stabilizer additive.

The samples, with and without additive, are placed in an oven or in a thermostatic bath for 24 hours at 100 ° C to simulate aging (STD procedure ASTMD4870A).

The tar, VSB residue, used in the tests (taken after raising the TUF by 3 ° C) has a PV value of 1.06 and an HFT value as such <0.01% w / w. In normal driving conditions the PV value of the VSB tar is equal to 1.1.

This PV value demonstrates that the raising of the TUF caused an increase in severity, thus producing a less stable tar (lower PV). The sample was stabilized by addition of composition A at different dosages to verify its efficiency against the blank. The aging of the sample was carried out according to the standard method, therefore at a temperature of 100 ° C for 24 hours.

The results are reported in table 1

Table 1

As shown in the data in Tab. 1, the tar sample has a clear aging tendency, reaching an HFT value of approximately 0.2 w / w. The use of the additive in the ratio of 300 ppm manages to contain the aging of the sample by 78%, bringing it back to a HFT value below 0.05% w / w.

At this point we wanted to test the occurrence of this behavior in conditions of

Si B - Società Ite Ibi IA more severe aging, therefore an aliquot of stabilized sample was aged at 70 ° C for 96 hours. The results are reported in table 2

Table 2

The sample according to the non-standard procedure used has an aging tendency greater than 47% compared to that identified by the STD procedure and results to have an HFT out of the required specification (0.3% w / w). Product A, at the optimal dosage of 300 ppm, is able to counteract aging by 27%, bringing the sample back within the specification.

2) TAR VSB at TUF 6 ° C

The sample, taken after raising the oven outlet temperature (TUF) by 6 ° C, has a PV value of 1.01 and an HFT as such <0.01% w / w. In normal running conditions, the PV value of the TAR VSB is equal to 1.1.

Sil3 - Company Scream! The sample was added with Product A, at different dosages to verify its efficiency with respect to the blank.

The aging of the sample was carried out according to the standard method, therefore at a temperature of 100 ° C for 24 hours. The results are reported in table 3

Table 3

The VSB tar sample taken under severe running conditions shows a much more critical behavior than the sample taken at 3 ° C. The HFT value is higher than 61% resulting in 35% out of specification. Product A, at the optimal dosage of 500 ppm, reports the HFT value within the required specification.

The sample processed according to the NON STO procedure after 96 hours showed a critical HFT value equal to 0.66% w / w (Table 4), Product A, at a dosage of 500 ppm, managed to contain this

SiB - Società Itali.iru BrevallS aging by as much as 27%, even if the specification value has not been reached. The results are reported in table 4.

Table 4

Example 3: Plant test

Composition A was also tested in the plant during an industrial test lasting approx. 3 months. To adequately illustrate the test it is necessary to recall the following concept, namely that the VSB plant is managed with the aim of obtaining the maximum transformation into medium and light distillates (products with high added value). This objective is achieved by increasing the Oven Outlet Temperature (TUF), but this entails the disadvantage of obtaining an unstable and easily out of specification TAR. The addition of the additive allows to raise the TUF and at the same time obtain a stable TAR.

SiB - Società Italiana Brevetti Table 6 shows the trend of the TUF (increased by about 8 degrees during the test) during the period 1 February - 4 May 2006.

Composition A was added with an average dosage of about 100 ppm to the TAR produced by the plant, during the periods in which the furnace outlet temperature had been progressively raised. The samples taken by casting were subjected to analysis after aging in an oven for 96 hours and the results are shown in table 5 below.

The "HFT96h (additive)" column indicates the value (% w / w) of the sediment content on the sample taken after the point of addition of the additive. The "HFT24h blank) column indicates the value (% w / w) of the sediment content on the sample taken before the point of addition of the additive.

As can be seen from the data reported in Tab. 5, the composition A used in the plant shows an average efficiency of 28%.

óit - Solisi <'> · Iidhii. Bs; .tii i Table 5

In Table 6 the HFT data (without aging) were collected on the samples taken in the storage tanks, for the entire duration of the test. During the period prior to the plant test, despite the fact that the TUF had not been raised compared to the normal running of the plant, there were as many as 17 withdrawals

Sil3 - Its! Lin.- P Company; out of specification within 2 months, with very high HFT values, around 0.5 - 0.6%. The results are reported in table 6

Table 6

SiB - Iteli Company, Γ

As the data in the table show, during the whole test period, by increasing the TUF up to a maximum of 8 ° C (initial TUF = 480 ° C) and therefore increasing the severity of the system, the HFT values on the samples with additives always remain within the specified specification. During the first month of testing (February) the average HFT of the Fuel Oil produced was 0.226% (average monthly TUF 482.2 ° C); during the second month (March), the average TUF was raised to 485 ° C, but the average HFT did not increase, on the contrary, thanks to the effect of Product A, it was reduced to 0.198 3⁄4. For the third month of testing, the average TUF was still raised to 487.8 but the average HFT value was contained at 0.185%.

SiD - Itéh.iru Uri Company ·. ι.ϋί

Claims (15)

<l> / J «GV 06 0 r A CLAIMS 1. Stabilizing composition soluble in fuel oil characterized by the fact of containing at least one compound belonging to the class of stable free radicals (selected from nitroxides and dinitroxides) and a solvent, or a mixture of solvents, capable of maintaining stably in solution in the range of temperature between -10 ° C and 50 ° C, called compound. 2. Composition according to claim 1 characterized in that the fuel oil is the residue (tar) of a thermal conversion process of the Visbreaking (VSB) type. 3. Composition according to any one of claims 1 or 2 characterized in that the compound belonging to the free radical class is selected from nitroxides, dinitroxides, trinitroxides or mixtures thereof. 4. Composition according to claim 3 characterized in that the compound is a nitroxide of formula (I): Formula (I) KiB 3oci "iia iMlhna Bi" vaiti where R, R ', and R "represent a group selected from H, {C1-C15) alkyl, (C1-C15) cycloalkyl, (Cl-C15) aryl, substituted or unsubstituted with heteroatoms selected from 0, N, S, P, halogens or where the two R groups form a cyclic structure or mixtures of such compounds. 5. Composition according to claim 3 characterized in that the compound belonging to the free radical class is selected from: 4-hydroxy-2,2,6,6 tetramethyl-piperidin-N-oxyl (40H TIME); bis (1-oxyl-2,2,6,6-tetramethylpiperidin - 4 yl) sebacate; 2,2,6,6 tetramethyl-piperidin-N-oxyl (TIME); 1-oxyl-2,2,6,6 tetramethyl-piperidin-4-one (0X0 TIME); 4-acetamido-2,2,6,6 tetramethyl-piperidine-N-oxyl. 6. Composition according to any one of claims 1 or 5 characterized in that the solvent is selected from water, alcohols, glycols, glycol-ethers, aromatic solvents or their mixtures. 7. Composition according to any one of claims 1 or 6 characterized in that the compound belonging to the class of stable free radicals is present in a percentage amount between 0.1% and 50% w / w of the composition. 8. Method of stabilization of fuel oils WIB - Sociui 1? Sli .->. I »a comprising a step in which the composition according to any one of claims 1 to 7 is added to the oil in a quantity ranging from 1 to 2000 ppm with respect to the fuel oil. 9. A method according to claim 8 wherein the composition is added to the oil in a quantity ranging from 50 to 600 ppm with respect to the fuel oil. Method according to claims 8 or 9 wherein the combustible oil is the residue (tar) of the Visbreaking thermal conversion process (VSB). 11. Stabilized fuel oil obtainable by the method according to any one of claims 8 to 10. 12. Visbreaking thermal conversion process comprising a step in which the distillation residue (tar) is added to the composition according to any one of claims 1 to 7 in a quantity ranging from 1 to 2000 ppm with respect to the residue quantity. 13. Process according to claim 12 characterized in that the step of adding the stabilizing composition takes place on the residue leaving the column on the line towards the storage tank. Hear it 14. Thermal conversion plant for the production of petroleum distillates characterized in that it comprises an addition station to the distillation residue (tar) of the composition according to any one of claims 1 to 7 on the line between the column and the storage tank. 15. Plant according to claim 14 characterized in that it is a Visbreaking plant (VSB). p.p. Chimec S.p.A. the <1> - halmna Oi