Use of sulphonated alkyl phenol formaldehydes in the stabilization of ashphaltenes in crude oil

Abstract

Sulfonated compounds prepared by reacting at least one compound selected from the group consisting of formula (I) and (II), with gaseous SO3 in an equimolar ratio: wherein each Ph represents a phenol residue, n represents a number of from 2 to 12 and each R independently represents a moiety selected from the group consisting of C3-24 alkyl groups, C6-12 aryl groups, C6-12 hydroxyaryl groups, and C7-12 aralkyl groups; and methods of stabilizing asphaltenes in crude oil with sulfonated compounds are described.

Description

This invention relates to certain sulfonated alkylphenol formaldehydes and to their use for stabilizing asphaltenes in crude oil and to a process for preventing the precipitation of asphaltenes in crude oils.

Crude oil is a complex mixture of various paraffinic and aromatic hydrocarbons in which the individual constituents have very different chemical and physical properties. Accordingly both readily volatile, low-viscosity constituents and wax-like, high-viscosity fractions are obtained in the distillation of crude oil. The second of these two groups includes petroleum resins and, to a predominant extent, asphaltenes which are colloidally dispersed in the oil phase.

The asphaltenes consist of a mixture of various saturated, unsaturated and aromatic hydrocarbons, more particularly naphthalene derivatives. They also contain heterocyclic hydrocarbons which, in part, also contain complexed metal ions. In addition, asphaltenes are rich in sulfur, nitrogen and oxygen compounds. Because of their complex composition, asphaltenes are generally characterized on the basis of their solubility. Thus, the petroleum fraction insoluble in heptane or pentane, but soluble in toluene is referred to as asphaltenes, the “dissolution” of asphaltenes involving a complex process for which there has as yet been no complete theoretical explanation (cf. E. Y. Scheu, O. C. Mullins, Asphaltenes—Fundamentals and Applications, Plenum Press, New York, 1995, Chapter I and Chapter III).

Asphaltenes are present as micelle colloids in the oil phase of crude oil, the individual micelles consisting of several different molecules. The micelles vary in size according to the temperature and composition of the oil phase. For example, it is known that relatively light aromatic hydrocarbons in crude oil stabilize the asphaltene micelles. Under the conditions prevailing in petroleum production, however, the asphaltenes are often precipitated which results in the formation of highly viscous, wax-like or solid residues on the surface of the production units and the petroleum-containing formation surrounding the well. The asphaltene residues block the pores of the formation which leads to a noticeable reduction in the production rates and, in the worst case, can make production completely impossible. Asphaltene residues on the surfaces of the production units, for example the delivery tube or the casing walls of pipelines or separators, can also considerably reduce production.

Accordingly, there are various known methods for keeping asphaltenes dispersed in crude oil and for preventing their precipitation. DE 197 09 797 describes synergistic mixtures of alkyl phenol formaldehyde resins and certain alkoxylated amines as asphaltene dispersants. It is known from U.S. Pat. No. 4,414,035 that alkyl aryl sulfonic acid derivatives, for example dodecyl benzenesulfonic acid, disperse asphaltenes in crude oils.

However, it has often been found in practice that known auxiliaries for stabilizing asphaltenes differ very considerably in their effectiveness according to the nature and origin of the crude oil. This is attributable in particular to the complex and highly variable structure of the asphaltenes. Accordingly, efforts have been made to find new asphaltene stabilizers. In addition, known asphaltene stabilizers are often either toxic and/or ecologically unsafe. Because of this, it is preferred to avoid using them both for reasons of environmental safety and in the interests of safety at work.

Accordingly, the problem addressed by the present invention was to provide effective alternatives to the stabilizers known from the prior art for stabilizing asphaltenes in crude oils, despite very different crude oil qualities. It has been found that certain sulfonated alkyl phenol formaldehydes solve this problem.

In a first embodiment, therefore, the present invention relates to the use of products obtainable by sulfonation of compounds corresponding to formula (I) or (II): in which n is a number of 2 to 12 and R is a C_3-24 alkyl, C_6-12 aryl or hydroxyaryl or C_7-12 aralkyl group, as stabilizers for asphaltenes in crude oil. In addition, Ph in formula(l) and (II) is a phenol residue.

The sulfonation products used in accordance with the invention are obtained by sulfonation of compounds known per se corresponding to general formulae (I) and/or (II). These starting products are known, for example, from DE 197 09 797 A1. Reference is made here to formulae (I) and (II) in claim 1 of DE 197 09 797 A1, to the disclosure on page 2, lines 40 to 44 and to the disclosure on page 3 of that document. The disclosures of those passages are specifically included in the disclosure of the present application. Formulae (I) and (II) in DE 197 09 797 are identical with those of the present application. The compounds in question are resins which are obtainable, for example, under the name of Dowfax DM 645 (Dow Chemicals).

The educts corresponding to formulae (I) and (II) are sulfonated in known manner with gaseous SO₃. According to the invention, however, the sulfonation products are not neutralized, but are present as free acids. The sulfonation of the educts is preferably carried out by a continuous process in a falling film reactor. The gaseous sulfur trioxide is produced in situ by pyrolysis of pure sulfur. The polyalkyl formaldehyde resin used is preferably reacted with sulfur trioxide in an equimolar ratio. The reaction itself advantageously takes place at a temperature of 75 to 80° C. The end product is preferably not neutralized. The products according to the invention are obtained in the form of aqueous solutions which may be directly formulated and used as asphaltene dispersants without any further steps. The sulfonated products surprisingly exhibit distinctly better properties as asphaltene inhibitors or asphaltene stabilizers than the compounds known from the prior art or mixtures thereof according to the teaching of DE 197 09 797 A1.

Crude oil in the context of the present invention is understood to be the unrefined petroleum coming directly from the ground. This unrefined petroleum consists of complex mixtures of, predominantly, hydrocarbons with densities of 0.65 to 1.02 g/cm³ and calorific values of 38 to 46 MJ/kg. The boiling points of the most important constituents of crude oil are in the temperature range from 50 to 350° C. (cf. Römpp, Chemielexikon, Vol. 2, 1997, pages 1210 to 1213).

The use of the sulfonated alkylphenol formaldehydes in accordance with the invention, i.e. their addition to crude oils, effectively prevents the precipitation of asphaltenes and the formation of residues. In order to prevent the precipitation of asphaltenes, it is of advantage to add the sulfonated alkylphenol formaldehydes to the crude oil in quantities of 50 to 2500 ppm, preferably in quantities of 100 to 1000 ppm and more particularly in quantities of 150 to 500 ppm (active substance).

The present invention also relates to a process for preventing the precipitation of asphaltenes from crude oils, characterized in that sulfonated alkylphenol formaldehydes corresponding to the foregoing description are added to the crude oils as stabilizers in quantities of 100 to 2500 ppm.

The present technical teaching also encompasses the use of the sulfonated alkylphenol formaldehydes in the form of dilute solutions in aromatic solvents, preferably toluene. These dilute solutions contain the polyester amides in quantities of preferably 2 to 50% by weight, more preferably 2 to 20% by weight and most preferably 2 to 15% by weight. Corresponding formulations may also contain other additives, such as corrosion inhibitors or defoamers.

EXAMPLES

Production of the Sulfonation Products:

The educts were sulfonated by a continuous process in a falling film reactor. The gaseous sulfur trioxide was produced in situ by pyrolysis of pure sulfur. The polyalkyl formaldehyde resin used was reacted with sulfur trioxide in an equimolar ratio. The reaction itself was carried out at a temperature of 75 to 80° C. The end product was not neutralized. The active substance content as measured by Epton titration, the molecular weight and the acid number were determined as characteristics.

Typical values for a resin based on Dowfax DM 650 are shown by way of example below:

		Molecular
Additive	Acid value	weight [g/mol]	Active substance content [%]
A1	85-90	641	62-66

Testing of the Dispersing Properties:

The test is based on the fact that asphaltenes are soluble in aromatic hydrocarbons, but not in aliphatic hydrocarbons. Accordingly, dispersants can be tested by dissolving the oil or extracted asphaltenes in an aromatic solvent and then adding a nonaromatic solvent to produce a deposit. Since asphaltenes are dark in color, the size of the deposit can be determined by UV-spectroscopic measurement of the supernatant liquid.

Dispersing Test—Procedure

• a) A 20% solution of isolated asphaltenes in toluene is prepared;
• b) 9.5 ml heptane as precipitant for asphaltenes, 0.5 ml of the asphaltene solution in toluene and the corresponding quantity of dispersant solution for the required concentration are mixed and thoroughly shaken in a 10 ml graduated glass tube;
• c) a test tube without any dispersant solution is prepared as a negative sample and the solvent heptane is replaced by toluene as a positive sample; two commercial products (Anticor DSA 800 and 711) were included in the tests for further comparison;
• d) the test tubes were observed for 3 hours and the precipitation time of the asphaltenes was recorded, the sediment collecting at the bottom of the test tubes;
• g) evaluation of the sediment volume and appearance of the solution was carried out in comparison with the positive and negative samples. Evaluation of the sediment volume was based on a scale of 1 to 3 where 3 represents the largest volume.

The results of the precipitation tests at three concentrations of various formulations A to H according to the invention are set out in the following Table.

TABLE 1
Asphaltene test for various formulations
	Formulation	100 ppm	500 ppm	1000 ppm
	Negative sample	T = 30 mins	T = 30 mins	T = 30 mins.
		SV = 3	SV = 3	SV = 3
	A	No SV	No SV	No SV
	B	No SV	No SV	T = 30 mins.
				SV = 2
	C	No SV	No SV	T = 30 mins.
				SV = 2
	D	No SV	No SV	No SV
	E	No SV	No SV	No SV
	F	No SV	No SV	No SV
	G	T = 45 mins.	No SV	No SV
		SV = 1
	H	No SV	No SV	No SV
	Positive sample	No SV	No SV	No SV
	Anticor DSA 800	T = 2 h	T = 16 h	No SV
		T = 1-2	SV = 1
	Anticor DSA 711	T = 60 mins.	T = 16 h	No SV
		SV = 2	SV = 1
	T = precipitation time,
	SV = sediment volume (3 = maximum)

In order to be able to compare the results of the spectroscopic analysis, the absorption values of the experimental formulations were divided by the corresponding value of the positive sample (pure toluene)—shown in the Tables as relative absorption. The nearer the values are to 1.0, the better the effect of the dispersant formulation. The values are set out in the following Table.

TABLE 2
Relative absorption values of the asphaltene solutions
	Formulation	100 ppm	500 ppm	1000 ppm
	A	0.81	0.85	0.86
	B	0.79	0.81	0.72
	C	0.76	0.79	0.73
	D	085	0.87	0.89
	E	0.84	0.82	0.86
	F	0.79	0.80	0.84
	G	0.76	0.79	0.83
	H	0.82	0.86	0.87
	Positive sample	1	1	1
	Anticor DSA 800	0.74	0.76	0.78
	Anticor DSA 711	0.75	0.78	0.78

Claims

1-5. (canceled)

6. A method comprising: (a) providing one or more sulfonated compounds prepared by sulfonating one or more compounds corresponding to the general formulae (I) or (II):

7. The method according to claim 6, wherein the one or more sulfonated compounds are combined with the crude oil composition in an amount of from 50 to 2500 ppm.

8. The method according to claim 6, wherein the one or more sulfonated compounds are combined with the crude oil composition in an amount of from 100 to 1000 ppm.

9. The method according to claim 6, wherein the one or more sulfonated compounds are combined with the crude oil composition in an amount of from 150 to 500 ppm.

10. The method according to claim 6, wherein the one or more sulfonated compounds are combined with the crude oil composition in the form of an aromatic solution.

11. The method according to claim 10, wherein the aromatic solution comprises toluene.

12. A process for producing a sulfonated compound, said process comprising: (a) providing at least one compound selected from the group consisting of formula (I) and (II): wherein each Ph represents a phenol residue, n represents a number of from 2 to 12 and each R independently represents a moiety selected from the group consisting of C3-24 alkyl groups, C6-12 aryl groups, C6-12 hydroxyaryl groups, and C7-12 aralkyl groups; and (b) reacting the at least one compound with gaseous SO3 in an equimolar ratio.

13. The process according to claim 12, wherein the at least one compound is reacted with gaseous SO3 in a falling film reactor.

14. The process according to claim 12, wherein the at least one compound is reacted with gaseous SO3 at a temperature of from 75 to 80° C.

15. The process according to claim 12, wherein the at least one compound is reacted with gaseous SO3 in a falling film reactor at a temperature of from 75 to 80° C.

16. A sulfonated compound prepared by a process comprising: (a) providing at least one compound selected from the group consisting of formula (I) and (II): wherein each Ph represents a phenol residue, n represents a number of from 2 to 12 and each R independently represents a moiety selected from the group consisting of C3-24 alkyl groups, C6-12 aryl groups, C6-12 hydroxyaryl groups, and C7-12 aralkyl groups; and (b) reacting the at least one compound with gaseous SO3 in an equimolar ratio.

17. The sulfonated compound according to claim 16, wherein the at least one compound is reacted with gaseous SO3 in a falling film reactor.

18. The sulfonated compound according to claim 16, wherein the at least one compound is reacted with gaseous SO3 at a temperature of from 75 to 80° C.

19. The sulfonated compound according to claim 16, wherein the at least one compound is reacted with gaseous SO3 in a falling film reactor at a temperature of from 75 to 80° C.