USE OF ORGANIC POLYSULPHIDES AGAINST CORROSION BY
ACIDIC CRUDES
The present invention pertains to the field of the treatment of acidic crude petroleums in refineries. It relates more especially to a method of combating corrosion in refining units which process acidic crudes, comprising the use of specific polysulphide compounds.
Petroleum refineries may be confronted with a serious corrosion problem when they are required to process certain crudes known as acidic crudes. These acidic crudes consist essentially of naphthenic acids, which
are the origin of this corrosion phenomenon, which is a very particular phenomenon since it takes place in a liquid medium which is a non-conductor of electrical current. These naphthenic acids correspond to saturated cyclic hydrocarbons which carry one or more carboxylic
groups. The acidity of a petroleum crude is described by a measurement standardized in accordance with ASTM standard D 664-01. It is expressed in mg of potassium hydroxide required to neutralize 1 g of petroleum and is referred to as TAN (total acid number) . It is known
in this technical field that a crude petroleum having a TAN of more than 0.2 is qualified as acidic, and may lead to damage within the units of a refinery.
This corrosion reaction depends heavily on local conditions such as, for example, the temperature and the metallic nature of the walls in the unit concerned, the space velocity of the hydrocarbon, and the presence of a gas/liquid interface. Accordingly, even after major studies on the topic, refiners encounter great difficulty in predicting the extent of the corrosion reactions and their location.
One of the industrial solutions to this corrosion problem involves using apparatus made of stainless

steels - that is, alloys of iron with, in particular, chromium and molybdenum. However, this solution remains little used, owing to the high capital investment cost. That choice, moreover, must preferably be considered during the design of the refinery, since stainless steels have mechanical properties inferior to those of the carbon steels normally used, and require an appropriate infrastructure.
The existence of these technical difficulties in processing acidic crudes therefore means that, in general, these crudes are sold to refiners at a price level lower than that of the standard crudes.
Another solution to the problem of processing an acidic crude petroleum, which is used in practice by refiners, involves diluting it with another, non-acidic petroleum crude, so as to give a low average acidity, lower for example than the 0.2 TAN threshold. In this case the
concentration of naphthenic acid becomes low enough to give rise to acceptable corrosion rates. This solution remains limited in scope, however. The reason for this is that certain acidic crudes have TANs of more than 2, which curtails their use to not more than 10% of the
total volume of crudes entering the refinery. Moreover, certain blends of crudes sometimes lead to the converse of the desired effect, even after dilution, in other words to an acceleration of the corrosion reactions by naphthenic acids.
An alternative approach for combating this corrosion problem is to introduce, into the acidic crude petroleum to be processed, chemical additives which inhibit or prevent the attack of the metal walls of the
unit in question. This route is often very economic in comparison to that indicated above, involving the use of special steels or alloys.
Laboratory studies, such as that of Turnbull

(Corrosion - November 1998 in Corrosion, volume 54, No. 11, page 922), have envisaged the addition of small amounts (of the order of 0.1%) of hydrogen sulphide to the crude petroleum, for the purpose of reducing the 5 corrosion by naphthenic acids. This solution, however, is not applicable in the refinery, since the hydrogen sulphide, which is gaseous at ambient temperature, is highly toxic, thereby making the consequences of any leak extremely serious, and limiting its use. Moreover, at even higher temperature, the hydrogen sulphide itself becomes highly corrosive and, in other parts of the refinery, will lead to aggravation of the generalized corrosion.
US Patent 5182013 describes the use, for solving this corrosion problem, of other sulphur compounds, namely polysulphides having alkyl radicals containing from 6 to 30 carbon atoms.
EP Patent 742277 describes the inhibitory activity of a combination of a trialkyl phosphate and an organic polysulphide. US Patent 5552085 recommends the use of thiophosphorus compounds such as organic thiophosphates or thiophosphites. AU Patent 693975 discloses as
inhibitor a mixture of trialkyl phosphate and phosphoric esters of sulphurized phenol neutralized with lime.
However, the handling of organophosphorus compounds is
very delicate, owing to their high toxicity. In
addition, they are poisons for the hydrotreating
catalysts which are installed to purify the hydrocarbon
cuts obtained from atmospheric and vacuum
distillations. For these two reasons at least, their
use in the field of refining is undesirable.
Surprisingly it has been found that the use of a specific class of organic polysulphides, namely poly-alkyl sulphides in which the number of carbons in each

alkyl radical is between 2 and 5, allows the corrosion caused by naphthenic acids to be inhibited more effectively than using the organic polysulphides known to date, and without the need to introduce phosphorus inhibitors as well.
The invention accordingly provides a method of combating the corrosion caused by naphthenic acids to the metal walls of a refining unit, characterized in that it comprises the addition to the hydrocarbon stream for processing by the unit of an effective amount of one or more hydrocarbon compounds of formula
in which
n is an integer between 2 and 15 and the symbols R1 and R2, which are identical or different, each represent a linear or branched alkyl radical containing between 2 and 5 carbon
atoms, it being possible for these radicals to contain, optionally, one or more heteroatoms such as oxygen or sulphur; or
R1 and R2, which are identical or different, each represent a cycloalkyl radical containing between
3 and 5 carbon atoms, it being possible for these radicals to contain, optionally, one or more heteroatoms such as oxygen or sulphur.
The polysulphides of formula (I) are prepared according to processes which are known per se, such as those described in patents US 2708199, US 3022351 and US 3038013. Some of them are commercial products.
Preferably R1 and R2 are linear or branched alkyl radicals and n is between 2 and 6.
According to another preferred version the radicals R1 and R2 are identical, owing to the improved stability

V
of the corresponding compound of formula (I).
According to a version which is even more preferred, poly(di-tert-butyl sulphide)s are used as a mixture of compounds of formula (I). These products, industrial in origin, are obtained for example from the reaction of sulphur with tert-butyl mercaptan. The reaction conditions allow industrial products to be prepared that are composed of a mixture of polysulphides with a number of sulphur atoms varying between 3 and 10, with a number-average value of between 2 and 6.
The amount of compound(s) of formula (I) to be added to the hydrocarbon stream for processing by the refining
unit corresponds generally to a concentration, expressed by equivalent weight of sulphur of the said compound relative to the weight of the hydrocarbon stream, of between 1 and 5000 ppm, preferably between 5 and 500 ppm. While remaining within this concentration
range, it will be possible to set a high content at the start-up of the method according to the invention, then to reduce this content subsequently to a maintenance level.
The method according to the invention makes it possible advantageously to process hydrocarbon streams, and more particularly crude petroleums, whose TAN is greater than 0.2 and preferably greater than 1.
The temperature at which the method is employed corresponds to that at which the corrosion reactions by naphthenic acids take place, and is generally between 200 and 450°C and more particularly between 250 and 350°C.
The addition of the compound of formula (I) to the hydrocarbon stream may be carried out in close proximity to where the corrosion reaction occurs or else, at a lower temperature, upstream of the process

of the said unit. This addition may be carried out by any means known to the skilled person which ensures control of the injection rate and effective dispersion of the additive in the hydrocarbon: for example, by means of a nozzle or of a mixer.
The metal walls of the refining unit in which the corrosion can be prevented by the method according to the invention are any walls liable to come into contact
with the stream of acidic hydrocarbon to be processed. The walls involved may therefore equally be the inner walls proper of units such as the atmospheric and vacuum distillation towers, or the surface of internal elements thereof, such as their plates or packings, or
else peripheral elements thereof, such as their offtake and entry lines, pumps, preheating ovens or heat exchangers, in so far as these elements are taken to a local temperature of between 200 and 450°C.
Non-limiting examples of hydrocarbon streams to be processed in accordance with the method according to the invention include the petroleum crude, the residue from atmospheric distillation, the gas-oil cuts obtained from atmospheric and vacuum distillations, and
the vacuum residue and distillate obtained from vacuum distillation.
The examples which follow are given purely to illustrate the invention and should not be interpreted as limiting its scope.
In these examples a corrosion test is implemented whose conditions are given below.
Description of the corrosion test:
This test employs an iron powder, which simulates a metal surface, and a mineral oil in which is dissolved a mixture of naphthenic acids, simulating an acidic

crude stream. The characteristics of these reactants are as follows:
white mineral oil having a density of 0.838 powder of spherical iron particles having a size of -40+70 mesh (i.e. from approximately 212 to 425 nun)
mixture of naphthenic acids having from 10 to 18 carbon atoms, a boiling point of between 270 and 324°C and an average molar mass of 244 g/mol.
The following components are introduced into a 150 ml glass reactor equipped with a dropping funnel and a water condenser and fitted with a stirring system and a temperature-measurement system:
70 ml (or 58.8 g) of the mineral oil, 2 g of the iron powder, 2.8 g of the naphthenic acid mixture.
The initial TAN of the reaction mixture is 10.
These reactants are kept in contact at a temperature of 250°C for 2 hours under an atmosphere of dry nitrogen, in order to avoid oxidation reactions.
At the end of the test the concentration of iron dissolved in the medium is determined by a conventional method employing mineralization of a sample, the taking-up of the residue in acidified water, and an assay using an electron torch.
This concentration of dissolved iron (expressed in ppm) is directly proportional to the corrosion rate of the iron powder that is generated by the mixture of naphthenic acids present in the mineral oil.
EXAMPLE 1: Reference test in the absence of inhibitor
The above test is employed without any compound of formula (I) being added, with 2 repetitions.

The results are indicated in Table I below.
Table Remove

EXAMPLE 2: Tests in the presence of polyalkyl sulphides
Example 1 is repeated with the addition of different
types of polyalkyl sulphides in mineral oil during the
charging of the reactor. The amount of these
derivatives added is calculated so as to give a
concentration of 500 ppm, expressed in equivalent
weight of sulphur, in the mineral oil present in the
reactor.
The results collated in Table II below are obtained.


Likewise indicated in this table is the degree of
inhibition of the corrosion brought about by the
naphthenic acid mixture. This degree is expressed in %
and is defined by the following formula:



inhibition (%) - 1 -

[iron} with inhibitor ] [iron] without inhibitor )

xlOO

in which [iron] is the concentration of dissolved iron 25 measured with or without inhibitor, the concentration of iron without inhibitor being equal to 203.5 ppm in accordance with Example 1.

Table Remove

* supplier: ARKEMA

CLAIMS
We claim:
1. A polypeptide from 30 to 500 amino acids capable of binding to CD11b/CD 18
selected from the group consisting of:
a. a fragment of a Bordetella adenylate cyclase comprising a wild type
CD11b/CD 18 interaction domain of said Bordetella adenylate cyclase consisting
of:
(i) the amino acids extending from position 1166 to position 1281 of SEQ
ID NO:l;
(ii) the amino acids extending from position 1165 to position 1280 of SEQ
ID NO:3;or
(iii) the corresponding domain of the adenylate cyclase of a Bordetella
species as identified by aligning the sequence of the adenylate cyclase of
said Bordetella species with the sequence extending from amino acid 1166
to amino acid 1281 of SEQ ID NO: 1 to provide best local alignment; or
b. a fragment of said wild type CD11b/CD 18 interaction domain, as defined in
options (i) to (iii), sufficient to retain the capacity to bind to CD11b/CD 18.
c. a polypeptide having at least 70% identity with the polypeptide defined in option
a) or b), wherein said variant retains the capacity to bind to CD11b/CD 18.
2. The polypeptide as claimed in claim 1, option c), wherein said identity is at least 80% or at least 90%.
3. The polypeptide as claimed in claim 1, having from 50 to 300 or from 50 to 150 amino acids.
4. The polypeptide as claimed in claim 1, wherein said polypeptide is:
(i) the fragment of the Bordetella pertussis adenylate cyclase, extending from amino acid 1166 to amino acid 1281 of SEQ ID NO:l;
(ii) a fragment comprising the region extending from amino acid 1208 to amino acid
1243 of the B. pertussis adenylate cyclase; or
(iii) the corresponding domain of the adenylate cyclase of a Bordetella species as
identified by aligning the sequence of the adenylate cyclase of said Bordetella
species with the sequence as defined in option (i) or option (ii), to provide best local
alignment.
5. The polypeptide as claimed in any one of claims 1 to 4, wherein said polypeptide is capable of raising antibodies recognizing specifically Bordetella species adenylate cyclase, preferably Bordetella pertussis adenylate cyclase.
6. The polypeptide as claimed in any one of claims 1 to 4, which further comprises an acylation domain of adenylate cyclase and/or the hydrophobic domain.
7. The polypeptide as claimed in any one of claims 1 to 4, wherein said polypeptide is not toxic when administered in vivo to a mammal.
8. Use of the polypeptide as claimed in any one of claims 1 to 4, in the preparation of medicament for the prevention or treatment, in human or in an animal, of disease symptoms associated with whooping cough and/or for protecting a human or an animal against the disease symptoms associated with Bordetella infection.
9. Use of the polypeptide as claimed in any one of claims 1 to 4, in the preparation of a vector for specifically targeting to CD11b expressing cells a molecule of interest coupled to said polypeptide.
10. A proteinaceous vector for targeting a molecule of interest to CD11b/CD 18 expressing cells, characterized in that said vector comprises the polypeptide according to claim 1, coupled to a molecule of interest.
11. The proteinaceous vector as claimed in claim 10, wherein said molecule of interest is selected from the group consisting of: peptides, glycopeptides, lipopeptides, polysaccharides, oligosaccharides, nucleic acids, lipids and chemicals.
12. The proteinaceous vector as claimed in claim 10, wherein said molecule of interest is the active principle of a medicament.
13. The proteinaceous vector as claimed in claim 10, wherein said molecule of interest is coupled by chemical linkage.
14. The proteinaceous vector as claimed in claim 10, wherein said molecule of interest comprises an antigen or an epitope.
15. The proteinaceous vector as claimed in claim 10, wherein said molecule of interest is a peptide or a polypeptide comprising an antigen or an epitope.
16. A nucleic acid which encodes a polypeptide as claimed in any one of claims l_to 4.
17. A nucleic acid which encodes a proteinaceous vector which comprises the polypeptide a as claimed in any one of claims 1 to 4 coupled to a molecule of interest selected from the group consisting of peptides, glycopeptides, and lipopeptides.
18. A nucleic acid as claimed in claim 17, wherein the molecule of interest comprises an antigen or an epitope, or is a peptide or a polypeptide comprising an antigen or an epitope.
19. An expression vector comprising the nucleic acid as claimed in claim 16, appropriate for the expression of the encoded polypeptide in a host cell.
20. An expression vector as claimed in claim 19, which is a plasmid, a cosmid, a phagemid or viral DNA.
21. A host cell comprising the nucleic acid as claimed in claim 16.
22. A host cell comprising an expression vector as claimed in claim 19.
23. A pharmaceutical composition comprising the polypeptide as claimed in any one of claims 1 to 4, in combination with a pharmaceutically acceptable vehicle.
24. A pharmaceutical composition comprising the proteinaceous vector as claimed in claim 10, in combination with a pharmaceutically acceptable vehicle.
25. A vaccine comprising an immunoprotective amount of the proteinaceous vector as claimed in claim 10.
26. A polyclonal serum obtainable by the immunization of an animal or a human with the polypeptide as claimed in any one of claims 1 to 4, a pharmaceutical composition according to claim 24 or a vaccine according to claim 25.
27. A monoclonal antibody directed specifically against the polypeptide as defined in any one of claims 1 to 4.
28. The polyclonal serum as claimed in claim 26, which is capable of blocking the binding of adenylate cyclase to CD11b/CD18.
29. The monoclonal antibody as claimed in claim 27, which is capable of blocking the binding of adenylate cyclase to CD11b/CD 18.
30. A pharmaceutical composition comprising the polyclonal serum as claimed in claim 26, in combination with a pharmaceutically acceptable vehicle.
31. A pharmaceutical composition comprising the monoclonal antibody as claimed in claim 27, in combination with a pharmaceutically acceptable vehicle.
32. The use of a polyclonal serum as claimed in claim 26, in the preparation of medicament for the prevention or treatment, in human or in an animal, of disease symptoms associated with whooping cough and/or for protecting a human or an animal against the disease symptoms associated with Bordetella infection.
33. The use of a monoclonal antibody as claimed in claim 27, in the preparation of medicament for the prevention or treatment, in human or in an animal, of disease symptoms associated with whooping cough and/or for protecting a human or an animal against the disease symptoms associated with Bordetella infection.
34. A method for in vitro targeting a molecule of interest to CD11b expressing cells, said method comprising:
a. providing CD11b expressing cells extracted from a living organism; and
b. culturing said CD11b expressing cells with the proteinaceous vector according to
claim 10 under appropriate conditions for targeting said vector to said CD11b
expressing cells.

35. The method as claimed in claim 34, wherein said molecule of interest comprises an antigen or an epitope.
36. The method as claimed in claim 34, wherein said CD11b expressing cells are myeloid dendritic cells.
37. CD11b-expressing cells comprising a molecule of interest obtainable by the method as claimed in claim 34.
38. CD11b-expressing cells comprising an antigen or an epitope obtainable by the method as claimed in claim 35.
39. A cell therapy product for immunizing a human or an animal against an antigen, characterized in that it comprises an efficient amount of CD11b expressing cells as defined in claim 37 or 38, in combination with a pharmaceutically acceptable vehicle.
40. A use of an efficient amount of CD11b-expressing cells comprising a proteinaceous vector as claimed in claim 14 or 15, said CD11b-expressing cells being obtained by in vitro culturing CD11b-expressing cells with said proteinaceous vector, for the preparation of a medicament for priming a CD4+ and/or CD8+ response in a patient and thereby immunizing said patient.
41. Use as claimed in claim 40, wherein said CD11b-expressing cells are myeloid dendritic cells.