Elemental sulfur dissolution and solvation

Abstract

Methods for preventing elemental sulfur deposition from a hydrocarbon fluid is disclosed. A mercaptan is added to a hydrocarbon fluid that has elemental sulfur and reacted with the elemental sulfur to produce a disulfide and hydrogen sulfide. Amines and/or surfactants can assist with the process. Secondary reactions between the disulfide and the elemental sulfur result in a polysulfide and a solvated sulfur-disulfide complex. The disulfide, hydrogen sulfide, polysulfide and solvated sulfur-disulfide complex do not deposit, and can optionally be removed.

Claims

1. A method of preventing sulfur deposition onto equipment from hydrocarbon fluids, said method comprising: a) treating a hydrocarbon fluid containing elemental sulfur with a mercaptan under reaction conditions to produce a disulfide, a hydrogen sulfide, and optionally a polysulfide; b) removing said hydrogen sulfide from said hydrocarbon fluid; and c) wherein said disulfide and said optional polysulfide are dissolved and remain in fluid and do not deposit onto equipment from said hydrocarbon fluid.

2. The method of claim 1, wherein said treating step further includes the addition of an amine or a surfactant or heat or combinations thereof.

3. The method of claim 1, further comprising the steps of dissolving and solvating elemental sulfur with said produced disulfide to produce a solvated complex and removing said solvated complex from the hydrocarbon fluid.

4. The method of claim 1, wherein said mercaptan has a C1-C8 hydrocarbon chain.

5. The method of claim 1, wherein said mercaptan has a C1-C8 alcohol chain.

6. The method of claim 1, wherein said mercaptan is selected from m; ethanethiol; 1-propanethiol; 2-propanethiol; allyl mercaptan; butanethiol; tert-butyl mercaptan; pentanethiols; thiophenol; dimercaptosuccinic acid; thioacetic acid; 2 mercaptoethanol; dithiothreitol/dithioerythritol (an epimeric pair); 2 mercaptoindole; furan-2-ylmethanethiol; 3-mercaptopropane-1,2-diol; 3-mercapto-1-propanesulfonic acid; 1-hexadecanethiol; pentachlorobenzenethiol, and combinations thereof.

7. The method of claim 2, wherein said amine is selected from alkyl amines, alkyl-hydroxy amines, amino acids, amino saccharides, diamines, triamines, alkyl benzyl amines, methylamine, propyl amine, monoethanolamine, diethanolamine, isopropanolamine, diisopropanolamine, tris(2-aminoethyl)amine, glucosamine, ethylene diamine, methyldiethanolamine, triethanolamine, diethylenetriamine, pyrrolidone, triethylamine, 1-methyl-2-pyrrolidinone, N,N-dimethyl-N-(2-hydroxypropyl)amine, N,N,N′-trimethyl-N′-(2-hydroxypropyl)ethylenediamine, N,N,N′,N″-tetramethyl-N″-(2)-hydroxypropyl)diethylenetriamine, N,N,N′,N″,N′-pentamethyl-N″-(2-hydroxypropyl)triethylenetetramine, and combinations thereof.

8. A method of preventing sulfur deposition onto equipment from hydrocarbon fluids, said method comprising: a. treating a hydrocarbon fluid containing elemental sulfur under reaction conditions with a mercaptan and a surfactant to produce a disulfide, a hydrogen sulfide, and optionally a polysulfide; b. removing said hydrogen sulfide from said hydrocarbon fluid; c. wherein said disulfide and said optional polysulfide are dissolved and remain in fluid and do not deposit onto equipment from said hydrocarbon fluid; d. wherein said surfactant is selected from a group consisting of ethoxylated tetraethylene pentamine; ethoxylated hexamethylene diamine dimethyl quat; ethoxysulfated hexamethylene diamine dimethyl quat; ethoxysulfated hexamethyl tri(amine methyl quat); propoxysulfated hexamethylene diamine dimethyl quat; ethoxy hexamethylene poly(amine benzyl quat); ethoxysulfated hexamethylene poly(amine benzyl quat); ethoxylated-4,9-dioxa-1,12-dodecanediamine dimethyl quat tetrasulfate; propoxylated-ethoxylated benzyl-quaternized trans-sulfated bis(hexamethylene)triamine; 50% sulfonated, propoxylated, ethoxylated methyl quat of hexamethylene diamine; benzyl quaternary ammonium; mono- or di alkyl ammonium chloride with alkyl chains of C6-C30; and mixtures thereof.

9. The method of claim 1, wherein said reaction conditions comprises temperatures between about 15 and about 80° C.

10. The method of claim 1, wherein said reaction conditions comprises a temperature of about 30° C.

11. The method of claim 1, wherein said hydrocarbon fluids comprise a liquid or emulsion that is used in completion or treatment operations for a reservoir, a crude oil, a crude oil and produced water emulsion, hydrocarbon condensates, gasoline, jet fuel, waxes, kerosene, methanol, monoethylene glycol, triethylene glycol, or tetraethylene glycol.

12. A method of transporting hydrocarbon fluids in a pipeline, said method comprising: a) treating a hydrocarbon fluid containing elemental sulfur with a mercaptan under reaction conditions to produce disulfides, hydrogen sulfides, and optionally polysulfides; b) removing said hydrogen sulfides from said hydrocarbon fluid; and c) transporting said hydrocarbon fluid in a pipeline, wherein said disulfides and said optional polysulfides are dissolved and do not deposit onto a surface of said pipeline from said hydrocarbon fluid.

13. The method of claim 12, wherein said treating step further includes the addition of heat or an amine or a surfactant or combinations thereof.

14. The method of claim 12, further comprising the steps of dissolving and solvating elemental sulfur with said produced disulfides to produce a solvated complex and removing said solvated complex from the hydrocarbon fluid.

15. The method of claim 12, wherein said mercaptan has a C1-C8 hydrocarbon chain or hydrocarbon chain with an alcohol.

16. The method of claim 12, wherein said mercaptan is selected from a group consisting of methanethiol (CH.sub.3SH), ethyl mercaptan (ethanethiol) (CH.sub.3CH.sub.2SH), propyl mercaptan (propanethiol) (CH.sub.3CH.sub.2CH.sub.2SH), butyl mercaptan (C.sub.4H.sub.9SH), amyl mercaptan (C.sub.5H.sub.11SH), beta mercaptoethanol (BME), and dithiothreitol (DTT).

17. A method of transporting hydrocarbons from fluids in a pipeline, said method comprising: a. treating a hydrocarbon fluid containing elemental sulfur with a mercaptan and an amine under reaction conditions to produce a disulfide, a hydrogen sulfide and optionally a polysulfide; b. removing said hydrogen sulfide from said fluid; c. wherein said disulfide and said optional polysulfide are dissolved and remain in fluid and do not deposit onto equipment from said hydrocarbon fluids; and d. wherein said amine is selected from a group consisting of triethylamine, N,N-dimethyl-N-(2-hydroxypropyl)amine, N,N,N′-trimethyl-N′-(2-hydroxypropyl)ethylenediamine, N,N,N′,N″-tetramethyl-N″-(2)-hydroxypropyl)diethylenetriamine, and N,N,N′,N″,N′-pentamethyl-N′-(2-hydroxypropyl)triethylenetetramine.

18. A method of transporting hydrocarbons from fluids in a pipeline, said method comprising: a. treating a hydrocarbon fluid containing elemental sulfur with a mercaptan and a surfactant under reaction conditions, to produce a disulfide, a hydrogen sulfide and optionally a polysulfide; b. removing said hydrogen sulfide from said fluid; c. wherein said disulfide and said optional polysulfide are dissolved and remain in fluid and do not deposit onto equipment from said hydrocarbon fluids; and d. wherein said surfactant is selected from a group consisting of ethoxylated tetraethylene pentamine; ethoxylated hexamethylene diamine dimethyl quat; ethoxysulfated hexamethylene diamine dimethyl quat; ethoxysulfated hexamethyl tri(amine methyl quat); propoxysulfated hexamethylene diamine dimethyl quat; ethoxy hexamethylene poly(amine benzyl quat); ethoxysulfated hexamethylene poly(amine benzyl quat); ethoxylated-4,9-dioxa-1,12-dodecanediamine dimethyl quat tetrasulfate; propoxylated-ethoxylated benzyl-quaternized trans-sulfated bis(hexamethylene)triamine; 50% sulfonated, propoxylated, ethoxylated methyl quat of hexamethylene diamine; benzyl quaternary ammonium; mono- or di alkyl ammonium chloride with alkyl chains of C6-C30; and mixtures thereof.

19. The method of claim 12, wherein said reaction conditions comprises temperatures between about 15 and about 80° C.

20. The method of claim 12, wherein said reaction conditions comprises temperatures of about 30° C.

Description

DETAILED DESCRIPTION

(1) The disclosure provides novel methods of preventing sulfur deposits in hydrocarbon fluid handling equipment through the use of added mercaptans. Adding mercaptans is counterintuitive to conventional desulfurizing methods, which aim to remove mercaptans and other sulfur-containing species. However, it was found that mercaptans can be added to the hydrocarbon fluids and reacted with elemental sulfur to produce more readily dissolved and/or solvated sulfur compounds, leading to a decrease in total solids of at least 30%.

(2) In more detail, a mercaptan is added to a hydrocarbon fluid containing elemental sulfur under reaction conditions suitable for solvating sulfur and sulfur deposits. In some embodiments, mercaptans with a C1-C8 hydrocarbon chain may be utilized. Alternatively, mercaptans with an alcohol chain (OH—R—S) may be used.

(3) The mercaptan reacts with the elemental sulfur to produce hydrogen sulfide and a disulfide compound, per Eq. 1. This reaction dissolves and/or solvates about 30 to 35% of the elemental sulfur in the hydrocarbon fluid via the formation of the hydrogen sulfide. The hydrogen sulfide can be removed from the hydrocarbon using known methods such as stripping with an amine gas. H.sub.2S/mercaptan scavengers are used to move sulfur species to the water phase or change the sulfur to less corrosive materials. For example, H.sub.2S and mercaptans can be scavenged with triazines to less volatile, less corrosive species. The sulfur compounds no longer deposit and thus do not negatively impact equipment, and if desired can be removed at a suitable point or not.

(4) The extent of partitioning to the water phase is currently undetermined, but this is one of the planned studies. Any sulfur compounds in the aqueous phase can easily be separated in the oil and water separator and disposed of accordingly.

(5) The other reaction product, the produced disulfide, is capable of removing additional elemental sulfur by either (1) dissolving and solvating the elemental sulfur or (2) reacting with the elemental sulfur per Eq. 2. Both methods result in the formation of sulfur-containing components that can move through the process equipment without depositing sulfur.

(6) As shown in Eq. 2, the disulfide reacts with elemental sulfur to form a polysulfide. The polysulfide is able to move through the system without depositing on process equipment and pipelines.

(7) Alternatively, the disulfide dissolves and solvates the elemental sulfur much like a disulfide surfactant. Like the polysulfide, the solvate solid elemental sulfur can be carried through the equipment without deposition.

(8) As both these reaction pathways for the disulfide can occur together, the amount of elemental sulfur being removed is theoretically about a 1:1 ratio with the produced disulfide. In other words, every gram of disulfide produced via Eq. 1 will remove an equal amount of elemental sulfur. Alternatively, the ratio of gram of disulfide to gram of removed elemental sulfur is between about 1:0.3 to about 1:1, or about 1:0.3 to about 1:0.5, or about 1:0.4 to about 1:0.75.

(9) As mentioned above, the methods are somewhat counterintuitive as one with skill in the art would not expect to need to add the very chemicals (sulfur-containing chemicals) they are usually trying to remove.

(10) In test experiments with pure mercaptan in excess of the elemental sulfur present at room temperature and 1 atm, full dissolution occurred in 15-60 min in a static bottle test. In some embodiments, an amine can be added alongside the mercaptan to catalyze the reactions and decrease the reaction time. In addition, temperature increases will also speed reaction time. It is expected that such an amine can result in a reaction rate that is less than 5 minutes, less than 3 minutes, or 1 minute or less.

(11) In other embodiments, a surfactant can be added alongside the mercaptan to enhance the dissolution reaction and help keep the dissolved components from depositing elsewhere in the process. Alternatively, both amines and surfactants can be added together with the mercaptan. The optimal order of addition is not yet known, and thus any order may be used, but for simplicity co-addition may be used.

(12) The presently disclosed methods are exemplified with respect to the examples below. These examples are included to demonstrate embodiments of the appended claims. However, these are exemplary only, and the invention can be broadly applied to any combination of mercaptan, with and without an amine catalyst and/or surfactant. Those of skill in the art should appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a similar result without departing from the spirit and scope of the disclosure herein. In no way should the following examples be read to limit, or to define, the scope of the appended claims.

Phase 1: Proof of Concept

(13) A solution of 99+% 2-mercaptoethanol (25 mL), water (20 mL), and 99+% triethylamine (5 mL) was made and pH adjusted to pH 4 with HCl. This solution is not considered optimized, but provides an initial demonstration of the concept. 4 mL of solution was pipetted over varying amounts of 99+% purity elemental sulfur and allowed to sit static overnight to demonstrate elemental sulfur dissolution and estimate the solution's dissolution capacity. The results show that the sulfur can be dissolved in the method of the invention. Subsequent experiments will be tested in a mixed oil and water environment, and then the various component ratios will be optimized.

(14) TABLE-US-00002 Complete Sample g mL Dissolution # sulfur dissolver (yes or no) Description 1 0.100 4.000 yes clear-no yellow solids 2 0.200 4.000 yes clear-no yellow solids 3 0.500 4.000 yes clear-no yellow solids 4 0.570 4.000 yes clear-no yellow solids 5 0.670 4.000 no yellow solids remain 6 0.800 4.000 no yellow solids remain 7 1.000 4.000 no yellow solids remain 8 2.000 4.000 no yellow solids remain Estimated Dissolution Capacity 142.5 g elemental sulfur/L experimental solution

Phase 2: (Prophetic) Identification of Reactions

(15) Phase 2 of our research is aimed at identifying and quantifying liquid products after reaction of elemental sulfur and BME. While reactions 1 and 2 (below) are the expected reversible reactions, there are other possible competitive reaction pathways which also result in H.sub.2S off-gas, e.g., dehydrogenation. Thus, a more thorough understanding and identifying the products in the liquid may allow for optimization of the application of BME or other thiols as a reactive sulfur solvent.

(16) ##STR00001##

(17) Once the stoichiometry is verified and products are determined, it will be possible to ‘fine tune’ the system for uptake rate, ultimate capacity and overall economics.

(18) BME (as a 50 wt % aqueous solution) will be contacted with varying amounts of very pure elemental sulfur at ambient temperature (˜20° C.) in order to identify and quantify species released during the process of sulfur uptake using various analytical techniques, such as GC, GC-MS, GC/PSPD, LC, HPLC, and the like.

(19) Our preliminary testing indicated that the reaction may require a catalyst (amine catalyst) and that the catalyzed reaction is quite fast (on the minute timescale). Requirement of catalyst can be verified by performing tests with and without catalyst including varying levels and identity of catalyst. The same can be done with surfactants. Rates can be measured empirically by observing the time required for observable reaction to stop (no solid elemental sulfur or no gas evolution). If no reaction is observed, then the analysis will proceed after 24 hours.

Phase 3: (Prophetic) In Situ Conditions

(20) Phase 3 research will proceed using the best mercaptans, catalysts, surfactants and/or molar ratios identified in Phase 2 and will serve to confirm that the reactions still proceed as expected under down hole or produced fluid conditions. These will likely include efforts to study the effects of H.sub.2S overpressure, other production chemicals (CI, etc. for compatibility info), temperature dependence, various dilutions, high ionic strengths to verify that the chemistry would work in brine, verification of water miscibility, and labelling studies to determine the oil and water partitioning coefficients of the reagents and reaction products.

(21) The above exemplary use of the methods is intended to be illustrative only, and not unduly limit the scope of the appended claims. Those of skill in the art should appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain identical or similar result without departing from the spirit and scope of the disclosure herein. In no way should the following be read to limit, or to define, the scope of the appended claims.

(22) The following references are incorporated by reference in their entirety for all purposes.

(23) U.S. Pat. No. 3,708,421 Process to remove mercaptan sulfur from sour oils.

(24) U.S. Pat. No. 4,283,270 Process for removing sulfur from petroleum oils

(25) U.S. Pat. No. 5,199,978 Process for removing elemental sulfur from fluids

(26) US20080308463 Oxidative desulfurization process

(27) US20130149788 Assay for quantifying elemental sulfur levels in a sample

(28) US20190101519 Quantifying organic and inorganic sulfur components

(29) U.S. Pat. No. 6,808,919 Biodesulfurization of hydrocarbons

(30) ASTM D2622, ASTM D4292-16e1, ASTM D5453-93, ASTM D5623, ASTM D129-18.