METHODS FOR REDUCING HYDROGEN SULFIDE IN CRUDE OIL

Abstract

The invention provides a method of removing or lowering amounts of hydrogen sulfide in a crude oil, the method comprising adding to the crude oil an imine compound represented by the formula R.sup.1C(CH.sub.3).sub.2NCH.sub.2, wherein R.sup.1 represents a (1-5C)alkyl group.

Claims

1. A method of removing or lowering amounts of hydrogen sulfide in a crude oil, the method comprising adding to the crude oil an imine compound represented by the formula R.sup.1C(CH.sub.3).sub.2NCH.sub.2, wherein R.sup.1 represents a (1-5C)alkyl group.

2. A method of producing a distillate fuel component boiling in the kerosene range from a crude oil, wherein the crude oil contains an imine compound represented by the formula R.sup.1C(CH.sub.3).sub.2NCH.sub.2, wherein R.sup.1 represents a (1-5C)alkyl group, and/or an amine residue thereof, the method comprising distilling the crude oil to form the distillate fuel component.

3. The method according to claim 1, wherein R.sup.1 represents a methyl group or a 5C alkyl group.

4. The method according to claim 2, wherein R.sup.1 represents a methyl group or a 5C alkyl group.

5. The method according to claim 3, wherein R.sup.1 represents a 5C alkyl group.

6. The method according to claim 4, wherein R.sup.1 represents a 5C alkyl group.

7. The method according to claim 1, wherein the imine compound is tert-butylimine or tert-octylimine.

8. The method according to claim 2, wherein the imine compound is tert-butylimine or tert-octylimine.

9. The method according to claim 3, wherein the imine compound is tert-butylimine or tert-octylimine.

10. The method according to claim 4, wherein the imine compound is tert-butylimine or tert-octylimine.

11. The method according to claim 7, wherein the imine compound is tert-octylimine.

12. The method according to claim 8, wherein the imine compound is tert-octylimine.

13. The method according to claim 9, wherein the imine compound is tert-octylimine.

14. The method according to claim 10, wherein the imine compound is tert-octylimine.

15. The method according to claim 1, wherein the imine compound is prepared from tert-octyl amine and formaldehyde or paraformaldehyde.

16. The method according to claim 2, wherein the imine compound is prepared from tert-octyl amine and formaldehyde or paraformaldehyde.

17. The method according to claim 3, wherein the imine compound is prepared from tert-octyl amine and formaldehyde or paraformaldehyde.

18. The method according to claim 4, wherein the imine compound is prepared from tert-octyl amine and formaldehyde or paraformaldehyde.

19. A composition comprising a crude oil and an imine compound represented by the formula R.sup.1C(CH.sub.3).sub.2NCH.sub.2, wherein R.sup.1 represents a (1-5C)alkyl group.

20. The composition according to claim 19, wherein R.sup.1 represents a methyl group or a 5C alkyl group.

21. The composition according to claim 20, wherein R.sup.1 represents a 5C alkyl group.

22. The composition according to claim 19, wherein the imine compound is tert-butylimine or tert-octylimine.

23. The composition according to claim 22, wherein the imine compound is tert-octylimine.

24. The composition according to claim 19, wherein the imine compound is prepared from tert-octyl amine and formaldehyde or paraformaldehyde.

25. A distillate fuel component boiling in the kerosene range obtainable by a method of producing a distillate fuel component boiling in the kerosene range from a crude oil, wherein the crude oil contains an imine compound represented by the formula R.sup.1C(CH.sub.3).sub.2NCH.sub.2, wherein R.sup.1 represents a (1-5C)alkyl group, and/or an amine residue thereof, the method comprising distilling the crude oil to form the distillate fuel component.

26. The method of producing a distillate fuel component boiling in the kerosene range according to claim 2, wherein the distillate fuel component has improved thermal stability when compared to a distillate fuel component produced in the same way but from a crude oil containing an imine compound represented by the formula R.sup.2NCH.sub.2, wherein R.sup.2 represents an alkyl group having 10 or more carbon atoms, and/or an amine residue thereof.

27. The distillate fuel component boiling in the kerosene range according to claim 25, wherein the distillate fuel component has improved thermal stability when compared to a distillate fuel component produced in the same way but from a crude oil containing an imine compound represented by the formula R.sup.2NCH.sub.2, wherein R.sup.2 represents an alkyl group having 10 or more carbon atoms, and/or an amine residue thereof.

28. An aviation turbine fuel composition comprising a distillate fuel component boiling in the kerosene range obtainable by a method of producing a distillate fuel component boiling in the kerosene range from a crude oil, wherein the crude oil contains an imine compound represented by the formula R.sup.1C(CH.sub.3).sub.2NCH.sub.2, wherein R.sup.1 represents a (1-5C)alkyl group, and/or an amine residue thereof, the method comprising distilling the crude oil to form the distillate fuel component.

29. The aviation turbine fuel composition according to claim 28, wherein the aviation turbine fuel has improved thermal stability as measured by ASTM D3241 when compared to an aviation turbine fuel produced in the same way but from a crude oil containing an imine compound represented by the formula R.sup.2NCH.sub.2, wherein R.sup.2 represents an alkyl group having 10 or more carbon atoms, and/or an amine residue thereof.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0087] For a better understanding of the invention, and to show how exemplary embodiments of the same may be carried into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

[0088] FIG. 1 shows the amine content found in distillation fractions treated with Scavenger C in Example 1, with % w/w of the Scavenger C on the y axis and the distillation fraction (in C.) on the x axis;

[0089] FIG. 2 shows the amine content found in distillation fractions treated with tert-octylamine in Example 1, with % w/w of the tert-octylamine on the y axis and the distillation fraction (in C.) on the x axis;

[0090] FIG. 3 shows the amine content found in distillation fractions treated with Scavenger A in Example 1, with % w/w of the Scavenger A on the y axis and the distillation fraction (in C.) on the x axis;

[0091] FIG. 4 shows the amine content found in distillation fractions treated with Primene 81R Amine in Example 1, with % w/w of the Primene 81R on the y axis and the distillation fraction (in C.) on the x axis;

[0092] FIG. 5 shows hydrogen sulfide scavenging efficiency for Scavenger C according to Example 2, with the concentration of hydrogen sulfide remaining (in mg/L) on the y axis and time (in minutes) on the x axis; and

[0093] FIG. 6 shows hydrogen sulfide scavenging efficiency for Scavenger C according to Example 3, with the concentration of hydrogen sulfide remaining (in mg/L) on the y axis and time (in minutes) on the x axis.

EXAMPLES

[0094] The invention will now be described with reference to the following non-limiting examples.

[0095] Scavenger A is a terminal imine formed by the reaction of Primene 81R Amine and formaldehyde (or paraformaldehyde) and is a known commercial hydrogen sulfide scavenger. Primene 81R is a primary aliphatic amine in which the amino nitrogen is linked to a tertiary carbon and the total number of carbon atoms is in the C12-C14 range. Thus Scavenger A is a compound of the formula R.sup.2NCH.sub.2, wherein R.sup.2 represents an alkyl group having 12-14 carbon atoms.

Preparative Example Scavenger A (Comparative)

[0096] Primene 81R amine (10 g, 50.3 mmol) was dissolved in toluene (50 ml). Paraformaldehyde (1.81 g, 60.3 mmol) was added and the mixture heated to reflux for 1 hour with a Dean Stark trap in place to capture the water produced. After cooling to room temperature, the organic phase was concentrated in vacuo to afford Scavenger A (9.52 g, 45.1 mmol, 90%) as a yellow oil.

Preparative Example Scavenger C (Inventive; Tert-Octylimine)

[0097] Paraformaldehyde (0.94 g, 31.1 mmol) was added to in EtOAc (20 ml) to form a suspension. tert-Octylamine (4.03 g, 31.1 mmol) was added and the mixture stirred at room temperature for 1 hour, then at 60 C. for 1 hour. After cooling to room temperature, the aqueous phase was separated and the organic phase dried over MgSO.sub.4 and concentrated in vacuo to afford tert-octylimine, Scavenger C (3.43 g, 24.3 mmol, 78%) as a colourless oil.

Example 1: Distillation Profile of Nitrogen-Containing Oil Additives

[0098] A mixture of diesel (100 ml), aviation turbine fuel (100 ml) and gasoline (50 ml) was placed in a 500 ml round bottom flask. A stirrer bar was added followed by an additive to be tested (0.3 ml). Distillation equipment, comprising a thermometer, water-cooled condensing tube and receiver vessel were then attached to the round bottom flask. The system was purged with nitrogen and heat was applied to the round bottom flask while the contents were stirred. Separate fuel distillation fractions were then collected based on the temperature reading of the thermometer. Fractions collected corresponded to the following temperature ranges 0-100 C., 100-120 C., 120-140 C., 140-160 C., 160-180 C., 180-200 C. The non-distilled residue was collected and classed as the >200 C. fraction. Each fraction was then tested to determine the amine/nitrogen content. Results are shown in FIGS. 1 to 4.

[0099] The Additives tested were: Scavenger C, tert-octylamine, Scavenger A, and Primene 81R Amine.

[0100] FIGS. 1 and 2 show that Scavenger C and tert-octylamine (the potential nitrogen-containing constituents present when treating oil-products with Scavenger C) are found solely in the low temperature (i.e. <200 C.) distillation fractions. Consequently, only a small amount of these materials would be expected within higher temperature cuts. In contrast, Scavenger A and Primene 81 R Amine (the potential nitrogen-containing constituents present when treating oil-products with Scavenger A) were found in all distillation fractions (see FIGS. 3 and 4). Amines from Scavenger A and Primene 81 R Amine would therefore be considerably more likely to be present within higher temperature cuts, including those corresponding to aviation turbine fuel.

Example 2: Hydrogen Sulfide Scavenging Efficiency

[0101] Caromax 20 (20 ml) was placed into a reaction vessel containing a stirrer bar and the system sealed. A stock solution of Caromax 20/H.sub.2S (4 ml, about 525 mg/L H.sub.2S) was added to the reaction vessel and the mixture heated to 75 C. with stirring. Once the temperature had stabilised the time=0 liquid H.sub.2S content was determined (in mg H.sub.2S/L). Hydrogen sulfide Scavenger C (415 mg/L) was then injected into the system and the liquid H.sub.2S content determined at the following time points after injection; 1, 5, 10, 20 and 30 minutes. The results are shown in FIG. 5.

[0102] FIG. 5 shows that Scavenger C reduces the amount of hydrogen sulfide in the system.

Example 3: Hydrogen Sulfide Scavenging Efficiency

[0103] Crude oil (20 ml) was placed into a reaction vessel containing a stirrer bar and the system sealed. A stock solution of Caromax 20/H2S (1.3 ml, about 525 mg/L H2S) was added to the reaction vessel and the mixture heated to 49 C. with stirring. Once the temperature had stabilised the time=0 liquid H2S content was determined (in mg H2S/L). Hydrogen sulfide Scavenger C (525 mg/L) was then injected into the system and the liquid H2S content determined at the following time points after injection; 1, 5, 10, 20 and 30 minutes. The results are shown in FIG. 6.

[0104] FIG. 6 shows that Scavenger C reduces the amount of hydrogen sulfide in the system.

Example 4: Hydrogen Sulfide Scavenging Efficiency

[0105] A series of tests were performed to study the effectiveness of Scavenger C. In these tests, 2 ml of a stock solution containing 0.6 mg/ml of Na.sub.2S in MeOH was added to 8 ml of Caromax and the vessel sealed. Hydrogen sulfide was generated in situ by injecting 0.07 ml of 0.5M HCl (2 molar equivalents). Thus, the solution contained approximately 50 mg/L of hydrogen sulfide. Scavenger C was then injected in an amount as shown in Table 1. The mixture was heated to 75 C. for 30 minutes and then allowed to cool. The presence of hydrogen sulfide remaining was assessed using a colourimetric test which tests positive if >1 mg/L of hydrogen sulfide is present. Thus, a positive test indicates a failure to reduce the hydrogen sulfide concentration to <1 mg/L.

[0106] Multiple tests were performed over an extended period of time (several weeks) using different batches of Scavenger C and the results are summarised in Table 1.

TABLE-US-00001 TABLE 1 Amount of Total Scavenger C added number of Molar Equivalents tests Passes Fails % pass 0.5 31 24 7 77 1.0 40 40 0 100 2.0 36 36 0 100 5.0 8 8 0 100 10.0 2 2 0 100 15.0 2 2 0 100

[0107] The results show that at treat rates at or above 1 mole of Scavenger C per mole of hydrogen sulfide, all tests resulted in hydrogen sulfide levels <1 mg/L.