Process for removing naphthenic acids from crude oil and crude oil distillates

Abstract

The present invention relates to a process for the removal of naphthenic acids from crude oils and crude oil distillates by use of supported basic ionic liquids.

Claims

1. A process for removing organic acids from at least one of a crude oil and a crude oil distillate containing organic acids comprising the steps of: (i) contacting at least one of the crude oil and the crude oil distillate containing organic acids with a supported basic ionic liquid having a basic anion selected from hydrogencarbonate or alkylcarbonate, wherein the ionic liquid and at least one of the crude oil and the crude oil distillate are contacted in a mass ratio of from greater than 1:40; and (ii) obtaining at least one of a crude oil and a crude oil distillate product having reduced acidity which is separated from the supported basic ionic liquid.

2. A process according to claim 1, wherein the ionic liquid and at least one of the crude oil and the crude oil distillate are contacted in a mass ratio of from greater than 1:40 to up to 1:300.

3. A process according to claim 1, wherein the basic anion is selected from alkylcarbonate anions, wherein the alkyl group of the alkylcarbonate anion comprises from 1 to 20 carbon atoms.

4. A process according to claim 3, wherein the alkyl group is selected from at least one member of a group consisting of: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl and decyl.

5. A process according to claim 1, wherein the support is selected from silica, alumina, carbon, zirconia, alumina-silica, or a zeolite.

6. A process according to claim 1, wherein the ionic liquid is adsorbed onto the support in an ionic liquid support mass ratio of from 10:1 to 1:10.

7. A process for removing organic acids from at least one of a crude oil and a crude oil distillate containing organic acids comprising the steps of: (i) contacting at least one of the crude oil and the crude oil distillate containing organic acids with a basic ionic liquid having a basic anion selected from hydrogencarbonate or alkylcarbonate, and further wherein the ionic liquid and at least one of the crude oil and the crude oil distillate are contacted in a mass ratio of from greater than 1:40; and (ii) obtaining at least one of a crude oil and a crude oil distillate product having reduced acidity which is separated from the basic ionic liquid.

8. A process according to claim 7, wherein the basic anion is selected from alkylcarbonate anions, wherein the alkyl group of the alkylcarbonate anion comprises from 1 to 20 carbon atoms.

9. A process according claim 7, wherein the organic acids are naphthenic acids.

10. A process according claim 7, wherein the basic ionic liquid comprises a cation selected or derived from the group consisting of: ammonium, azaannulenium, azathiazolium, benzimidazolium, benzofuranium, benzotriazolium, borolium, cinnolinium, diazabicyclodecenium, diazabicyclononenium, diazabicyclo-undecenium, dithiazolium, furanium, imidazolium, indazolium, indolinium, indolium, morpholinium, oxaborolium, oxaphospholium, oxazinium, oxazolium, iso-oxazolium, oxothiazolium, pentazolium, phospholium, phosphonium, phthalazinium, piperazinium, piperidinium, pyranium, pyrazinium, pyrazolium, pyridazinium, pyridinium, pyrimidinium, pyrrolidinium, pyrrolium, quinazolinium, quinolinium, iso-quinolinium, quinoxalinium, selenozolium, sulfonium, tetrazolium, iso-thiadiazolium, thiazinium, thiazolium, thiophenium, triazadecenium, triazinium, triazolium, iso-triazolium, and a cation selected from the group consisting of: ##STR00012## wherein: R.sup.a, R.sup.b, R.sup.c, R.sup.d, R.sup.e, R.sup.f and R.sup.g are each independently selected from hydrogen, a C.sub.1 to C.sub.30, straight chain or branched alkyl group, a C.sub.3 to C.sub.8 cycloalkyl group, or a C.sub.6 to C.sub.10 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or are substituted by one to three groups selected from: C.sub.1 to C.sub.6 alkoxy, C.sub.2 to C.sub.12 alkoxyalkoxy, C.sub.3 to C.sub.8 cycloalkyl, C.sub.6 to C.sub.10 aryl, CN, OH, SH, NO.sub.2, C.sub.6 to C.sub.10 aryl and C.sub.7 to C.sub.10 alkaryl, CO.sub.2(C.sub.1 to C.sub.6)alkyl, OC(O)(C.sub.1 to C.sub.6)alkyl, or any two of R.sup.b, R.sup.c, R.sup.d, R.sup.e and R.sup.f attached to adjacent carbon atoms form a methylene chain (CH.sub.2).sub.q wherein q is from 3 to 6, or a cation is selected from the group consisting of:
[N(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+, [P(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+, and [S(R.sup.a)(R.sup.b)(R.sup.c)].sup.+.

11. A process according to claim 7, wherein the ionic liquid additionally comprises a basic cation represented by the formula:
Cat.sup.+-(Z-Bas).sub.n wherein: Cat.sup.+ is a positively charged moiety; Bas is a basic moiety; Z is a covalent bond joining Cat.sup.+ and Bas, or is a divalent linking group; and n is an integer of from 1 to 3.

12. A process according to claim 11, wherein Cat.sup.+ represents a heterocyclic ring structure selected from at least one member of a group consisting of: imidazolium, pyridinium, pyrazolium, thiazolium, isothiazolinium, azathiozolium, oxothiazolium, oxazinium, oxazolium, oxaborolium, dithiozolium, triazolium, selenozolium, oxaphospholium, pyrollium, borolium, furanium, thiophenium, phospholium, pentazolium, indolium, indolinium, oxazolium, isooxazolium, isotriazolium, tetrazolium, benzofuranium, dibenzofuranium, benzothiophenium, dibenzothiophenium, thiadiazolium, pyrimidinium, pyrazinium, pyridazinium, piperazinium, piperidinium, morpholenium, pyranium, annolinium, phthalazinium, quinazolinium, quinazalinium, quinolinium, isoquinolinium, thazinium, oxazinium and azaannulenium.

13. A process according to claim 11, wherein Cat.sup.+-Z-Bas is selected from:
[N(Z-Bas)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+ and [P(Z-Bas)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+ wherein: Bas and Z are as defined in claim 11 and each of R.sup.b, R.sup.c, and R.sup.d are independently selected from methyl and ethyl.

14. A process according to claim 7, wherein the material to be deacidified is crude oil or a crude oil distillate selected from liquefied petroleum gas, gasoline, gas oil, diesel, jet fuel, kerosene, home heating oil, and mixtures thereof.

15. A process according to claim 7, wherein at least one of the crude oil and the crude oil distillate having reduced acid content is separated from the basic ionic liquid containing organic acids by means of a liquid-liquid extraction.

16. A process according claim 7, further comprising recovering the basic ionic liquid from the organic acids by way of a regeneration process, wherein the regeneration process comprises: a) contacting the basic ionic liquid with a carbonic acid, having a pKa of less than 6.75.

17. A process according to claim 16, wherein the pKa of the acid is less than 6.25.

18. A process according to claim 7, for removing organic acids from at least of one of the crude oil and the crude oil distillate containing organic acids comprising the steps of: (i) contacting at least one of the crude oil and the crude oil distillate containing organic acids with a supported ionic liquid having the formula:
[SUPPORT-Z-Cat.sup.+][X.sup.] wherein: SUPPORT represents a solid support; Z is a covalent bond joining Cat.sup.+ and Bas, or is a divalent linking group; [Cat.sup.+] is a cationic moiety; and [X.sup.] is an anion selected from alkylcarbonates and hydrogen carbonate; and (ii) separating at least one of the crude oil and the crude oil distillate product having reduced acidity from the solid supported ionic liquid wherein [SUPPORT-Z-Cat.sup.+] is selected from: ##STR00013## ##STR00014## wherein: R.sup.b, R.sup.c, R.sup.d, R.sup.e, R.sup.f and R.sup.g can be the same or different, and are each independently selected from hydrogen, a C.sub.1 to C.sub.40, straight chain or branched alkyl group, a C.sub.3 to C.sub.8 cycloalkyl group, or a C.sub.6 to C.sub.10 aryl group, wherein said alkyl, cycloalkyl or aryl groups are unsubstituted or may be substituted by one to three groups selected from: C.sub.1 to C.sub.6 alkoxy, C.sub.6 to C.sub.10 aryl, CN, OH, NO.sub.2, C.sub.7 to C.sub.30 aralkyl and C.sub.7 to C.sub.30 alkaryl, or any two of R.sup.b, R.sup.c, R.sup.d, R.sup.e and R.sup.f attached to adjacent carbon atoms form a methylene chain (CH.sub.2).sub.q wherein q is from 8 to 20, or an acyclic moiety, and comprises or consists of a group selected from amino amidino, imino, guanidino, phosphino, arsino, stibino, alkoxyalkyl, alkylthio, alkylseleno and phosphinimino, and is selected from:
[N(Z-SUPPORT)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+ and [P(Z-SUPPORT)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+.

19. A process according to claim 18, wherein [SUPPORT-Z-Cat.sup.+] is: ##STR00015## wherein: SUPPORT and Z are as defined in claim 18.

20. A process according to claim 18, wherein the solid support is selected from at least one member of a group consisting of: silica, alumina, carbon, zirconia, alumina-silica, and a zeolite.

21. A process according claim 10, wherein: [Cat.sup.+] is selected from:
[N(R.sup.a)(R.sup.b)(R.sup.c)(R.sup.d)].sup.+, and wherein R.sup.a, R.sup.b, R.sup.c and R.sup.d are each independently selected from C.sub.1 to C.sub.8 alkyl.

22. A process according claim 16, wherein the regeneration process further comprises the steps of: b) contacting the mixture of step a) with a solvent which is immiscible with the basic ionic liquid; and c) separating the solvent from the ionic liquid.

23. A crude oil/crude oil distillate having reduced acid content, the crude oil/crude oil distillate including a basic ionic liquid as defined in claim 7 and produced in accordance with the processes of claim 7.

Description

EXAMPLES

(1) Test Oils

(2) The oils used in the examples below are as follows: Model oil (dodecane doped with naphthenic acids, TAN 2.00 mg/g KOH); and Crude oil (Chad crude oil (TAN 3.91 mg/g KOH))
Ionic Liquids

(3) A series of alkylcarbonate and hydrogencarbonate ionic liquids based on a tetraalkylammonium cation were chosen for the extraction of naphthenic acids from model and crude oil. The ionic liquids were produced using known methods.

(4) Experimental Procedures

(5) General Procedure for the Removal of Naphthenic Acids Using Bases with Model/Crude Oil in a Solid-Liquid or Liquid-Liquid Extraction

(6) To a sample vial containing 100 g of model/crude oil (TAN 2.00 mg KOH/g and TAN 3.91 respectively) was added the specified mass of ionic liquid. The resulting mixture was stirred for the desired length of time at the specified temperature. For the liquid-liquid and solid-liquid extractions, the sample was centrifuged at 3000 rpm for 10 minutes. After separation of the phases, 5.00-10.00 g of the model/crude oil was taken and analysed by titration.

(7) General Procedure for the Recycling of the Ionic Liquids and the Solid Systems

(8) After phase separation, to the resultant lower layer was added 10 ml of water saturated with CO.sub.2. This was stirred for ten minutes and then the cloudy solution was centrifuged at 3000 rpm for 60 minutes. For the ionic liquid extractions the upper oil phase was removed and the lower aqueous phase was dried to leave the ionic liquid which was recycled according to the general procedure above. For the supported ionic liquid systems both the oil and aqueous phase were removed before drying of the solid prior to recycle.

(9) Unsupported Basic Ionic Liquids

(10) Two basic ionic liquids derived from methylcarbonate and hydrogencarbonate were tested with the crude oil sample, and the results are shown in Table 1 below.

(11) TABLE-US-00001 TABLE 1 Resultant TAN number upon extraction of ~100 g of crude oil with [N.sub.1,2,2,2][MeCO.sub.3]and [N.sub.1,2,2,2] [HCO.sub.3] IL OIL/IL Crude Oil mass mMoles Mass Resultant Entry IL (g) of IL ratio TAN 1 [N.sub.1,2,2,2][MeCO.sub.3] 1.38 7.2 72 <0.1 2 [N.sub.1,2,2,2][HCO.sub.3] 1.27 7.2 79 <0.1

(12) The results clearly demonstrate that for both the methyl and hydrogencarbonate systems an IL:OIL mass ratio of 1:75 is capable of reducing naphthenic acids in the crude to below 0.1 mg/g.

(13) Similar results were obtained for tests using the [N.sub.1,4,4,4][HCO.sub.3]N.sub.1,4,4,41[MeCO.sub.3] ionic liquids.

(14) Recycling of Unsupported Basic Ionic Liquids

(15) The application of ionic liquids as reagents to remove naphthenic acids from oil was further explored by subjecting these reagents to recycle.

(16) Table 2 (below) demonstrates the advantages of regeneration via a carbonic acid wash in accordance with an aspect of the present inventions, versus non-regeneration. Two basic ionic liquids derived from methyl and hydrogencarbonate were used.

(17) TABLE-US-00002 TABLE 2 Comparison of regenerative and non-regenerative recycle of [N.sub.1,2,2,2][MeCO.sub.3] and [N.sub.1,2,2,2] [HCO.sub.3] on resulting TAN numbers in crude oil Non-regenerated Carbonic wash Ionic liquid (mg/g KOH) (mg/g KOH) 7.2 mmol 1 2 1 2 [N.sub.1,2,2,2][MeCO.sub.3] <0.1 3.9 <0.1 0.45 [N.sub.1,2,2,2][HCO.sub.3] <0.1 3.87 <0.1 0.23

(18) In both ionic liquids studied the resulting TAN number shows no decrease where the alkylcarbonate ionic liquid is recycled without regeneration. In clear contrast, the use of carbonic acid regeneration of the alkylcarbonate ionic liquids results in good activity being retained.

(19) The results demonstrate a cheap and facile process for basic ionic liquid recycling.

(20) Supported Basic Ionic Liquids

(21) [N.sub.1,2,2,2][HCO.sub.3], [N.sub.1,2,2,2][MeCO.sub.3] and [N.sub.1,4,4,4][MeCO.sub.3] ionic liquids were supported onto silica (IL:SiO.sub.2 mass 1:2) by wet impregnation and its performance compared at various ionic liquid to oil mass ratios (see Table 3 below).

(22) TABLE-US-00003 TABLE 3 Resultant TAN number upon extraction of ~100 g of model oil at 20 C. for different silica supported ionic liquids IL OIL/IL Model Oil mass mMoles Mass Resultant Entry Ionic liquid (g) of IL ratio TAN 1 [N.sub.1,2,2,2][HCO.sub.3] 0.635 3.5 157 <0.1 2 [N.sub.1,2,2,2][MeCO.sub.3] 0.69 3.6 145 <0.1 3 [N.sub.1,4,4,4][MeCO.sub.3] 0.98 3.6 102 <0.1

(23) The results in table 3 demonstrate that supported basic ionic liquids can also be used for naphthenic acid removal.

(24) Covalently Bound Ionic Liquids

(25) The use of covalently bound ionic liquids for solid adsorption of naphthenic acids has also been explored using covalently bound ionic liquids, such as an alkylammonium propyl silicas (see Structure 1 below), results of which are shown in Table 4 (also below).

(26) Structure 1: Structure of the Covalently Tethered Aminopropyl Silica

(27) ##STR00011##

(28) As was noted with the physisorbed supported basic ionic liquids, the chemisorbed supported ionic liquids have also been shown to reduce naphthenic acids content in both model oil and crude oil systems. A major advantage of this system is that the aminopropyl silicas negate reagent leaching into the bulk oil.

(29) TABLE-US-00004 TABLE 4 Remaining TAN number after extraction of the liquid phase when using covalently bound basic ionic liquids Supported IL N loading TAN TAN (0.25 g) (mmol g.sup.1) Model Oil* Crude Oil* [SiO.sub.2NH.sub.3] [HCO.sub.3] 1.01 <0.1 3.37 [SiO.sub.2NEt.sub.3] [HCO.sub.3] 0.98 0.18 3.13 *reactions conducted using 7 g of oil
Recycling of Basic Solids

(30) Similar to the basic ionic liquid recycle experiments, regeneration of the chemisorbed basic ionic liquid can also be achieved with the use of carbonic acid (see Table 5 below).

(31) TABLE-US-00005 TABLE 5 Recycle of the covalently bound basic ionic liquid/model oil using carbonic wash Silica Non-regenerated Carbonic wash 0.25 g TAN 1 TAN 2 TAN 1 TAN 2 [SiO.sub.2NEt.sub.3] 0.12 1.83 0.17 0.31 [HCO.sub.3]

(32) Bound IL [SiO.sub.2NEt.sub.3][HCO.sub.3] shows similar activity after regeneration compared to the initial experiments. In contrast without regeneration the extraction ability of these solids decreases significantly.

CONCLUSION

(33) The use of the selected alkylcarbonate or hydrogencarbonate basic ionic liquids of the present inventions allows for TAN levels in crude oil to be reduced to <0.1 with OIL/IL ratios as high as 80.

(34) Solid supporting of these ionic liquids, such as for example alkylammonium and alkylcarbonates, also allows a significant naphthenic acid reduction to be achieved.

(35) The use of covalently bound basic ionic liquids can also be employed as supported reagents to remove naphthenic acids from crude oil.

(36) Both the supported ionic liquid and covalently bound basic ionic liquids reagents can be effectively recycled after use by simple regeneration using carbonic acid.