Nitrile solvents

Abstract

A method of removing from a surface a solid sulfur-containing impurity composition comprising a sulfur-containing compound, the method comprising the step of dissolving sulfur-containing compound in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition comprising less than

Description

[Technical Field]

[0001] This invention relates to the use of a nitrile compound as a solvent. More particularly, this invention relates to the use of a nitrile, such as tricyanohexane, as a solvent (e.g., a dissolving additive) for impurities in industrial fluids, for example. Cross-reference

[0002] This application relates to and claims priority to U.S. Provisional Patent Application No. 63 / 083,390, filed September 25, 2020, which is hereby incorporated herein by reference. [Previous Technology]

[0003] Hydrogen sulfide (H2S) and other organic sulfide compounds are commonly associated with various oil and gas operations. For example, hydrogen sulfide exists as a small amount as an impurity in crude oil, and natural gas may contain up to 30% hydrogen sulfide. More broadly, hydrogen sulfide and other organic sulfide compounds can be present in various fluids associated with various industrial processes, such as oil and gas operations. Because hydrogen sulfide and other organic sulfide compounds are highly corrosive and toxic, it is desirable to reduce or remove sulfide compounds from industrial fluids. For example, in oil and gas operations, various methods used to reduce or remove sulfide compounds from these fluids are generally referred to as "desulfurization" methods.

[0004] Common methods for reducing or removing sulfide components involve the use of chemical scavengers, often referred to as "hydrogen sulfide scavengers" or "H2S scavengers." For example, triazine compounds are commonly used as hydrogen sulfide scavengers. These and other hydrogen sulfide scavengers can be injected directly into various fluid streams in oil and gas operations, including into water-saturated streams at the wellhead or into gas-liquid contactors at processing facilities. Hydrogen sulfide scavengers preferentially react with hydrogen sulfide to form less volatile and / or non-volatile products. Conventional hydrogen sulfide scavengers are highly effective at removing hydrogen sulfide, and millions of gallons of such scavengers are used annually in North America.

[0005] Nevertheless, the use of hydrogen sulfide scavengers is not without its drawbacks. In particular, conventional hydrogen sulfide scavengers produce unwanted byproducts. For example, triazine compounds often react with hydrogen sulfide to form solid impurities containing amorphous dithiazides, commonly referred to as dithiazide solids. While these solid impurities are sufficiently soluble under certain temperature and pressure conditions (e.g., downhole conditions), they are typically insoluble. Consequently, significant amounts of these solid impurities are observed to precipitate in many oil and gas processing systems. For example, solid impurities may precipitate in transport and downstream distribution lines and facilities. In some cases, the amount of solid impurity precipitated may be sufficient to cause blockages in processing equipment such as pipes, containers, storage and transport tanks, and even wells. The problems associated with solid impurity precipitation are well-documented and known to those skilled in the art. When precipitated solids accumulate on the internal surfaces of oil and gas equipment and / or its components, specialized cleaning procedures are required to ensure proper functioning. In some cases, the accumulation may be so severe that component replacement becomes unavoidable.

[0006] Conventional cleaning operations can be expensive, time-consuming, and challenging. Typical methods use hydrogen peroxide and / or peracetic acid to dissolve solid impurities, usually at elevated temperatures. However, these chemicals are highly corrosive and often damage the equipment they are intended to clean.

[0007] Therefore, there is a need for novel methods and chemicals for reducing the precipitation of solid impurities and / or for cleaning precipitated solid impurities. [Summary of the Invention]

[0008] In some aspects, this disclosure provides a method for removing solid impurities from a surface, such as sulfur-containing compounds optionally present as part of a sulfur-containing impurity composition, the method comprising dissolving the solid impurity with a nitrile compound to preferably form a treated sulfur-containing impurity composition comprising less than 99.5% by weight of a sulfur-containing compound based on the total weight of the treated sulfur-containing impurity composition, and optionally wherein the treated dithiazine composition further comprises 1 ppm to 90% by weight of a polymeric sulfur-containing compound. In some cases, the nitrile compound has the chemical formula CxH2x-1(CN)3, where x is 4 to 10. In some cases, the nitrile compound comprises hexanetrionitrile. In some cases, the nitrile compound has the chemical formula CxH2x(CN)2, where x is 1 to 6. In some cases, the nitrile compound has the chemical formula CxH2x+1CN, where x is 1 to 6. In some cases, the nitrile compound has a chemical structure where a, b, and c are independently 0 to 4. In some cases, the solid impurity comprises a dithiazine compound. In some cases, nitrile compounds exhibit dithiazine solubility ranging from 0.01 kg / l to 20 kg / l at 70℉. In other cases, nitrile compounds exhibit dithiazine solubility ranging from 0.5 kg / l to 50 kg / l at 125℉.

[0009] In some aspects, this disclosure provides a dissolver solution comprising: a nitrile compound; and a hydrogen sulfide scavenger. In some cases, the dissolver solution comprises 0.1 vol% to 85 vol% of the nitrile compound. In some cases, the nitrile compound has the chemical formula CxH2x-1(CN)3, wherein x is 4 to 10. In some cases, the nitrile compound has a chemical structure wherein a, b, and c are independently 0 to 4. In some cases, the nitrile compound comprises hexanetrionitrile. In some cases, the hydrogen sulfide scavenger comprises a triazine compound. In some cases, the hydrogen sulfide scavenger comprises hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine.

[0010] In some aspects, this disclosure provides a method for dissolving dithiazide, the method comprising adding a dissolving solution of any of the foregoing embodiments to a system containing dithiazide.

[0011] In some embodiments, this disclosure relates to a method for treating a solid sulfur-containing impurity composition comprising a sulfur-containing compound, the method comprising contacting the sulfur-containing compound in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition comprising less than 99.5% by weight of the sulfur-containing compound and optionally 1 ppm to 90% by weight of trithiane.

[0012] In some embodiments, this disclosure relates to a method for suppressing the formation of polymeric sulfur-containing compounds in a sulfur-containing impurity composition comprising sulfur-containing compounds, the method comprising adding a nitrile compound to the sulfur-containing impurity composition, wherein at least some of the monomeric sulfur-containing compounds in the sulfur-containing impurity composition are dissolved to form a treated sulfur-containing impurity composition comprising a reduced amount of monomeric sulfur-containing compounds; wherein the treated sulfur-containing impurity composition comprises less than 90% by weight of a polymeric sulfur-containing compound, such as trithiane. The reduced amount of monomeric sulfur-containing compound is optionally at least 10% less than the initial amount of sulfur-containing compounds present in the sulfur-containing impurity composition.

Implementation Method

[0014] Introduction

[0015] As mentioned above, it has been confirmed that conventional hydrogen sulfide scavengers generate impurities due to their reaction with hydrogen sulfide. For example, 5-(2-hydroxyethyl)dithiazine is generated when the commonly used hydrogen sulfide scavenger hexahydro-1,3,5,-tris(2-hydroxyethyl)hexahydrodithiazine is used. See, for example, Jan M. Bakke et al., Hydrolysis of 1,3,5,-Tris(2-hydroxyethyl)hexahydrodithiazine and Its Reaction with H2S, 40 Ind. Eng. Chem. Res. 6051 (2001); Grahame N. Taylor & Ron Matherly, Gas Chromatographic-Mass Spectroscopic Analysis of Chemically Derivatized Hexahydrotriazine-based Hydrogen Sulfide Scavengers: Part II, 49 Ind. Eng. Chem. Res. 6267 (2010). When formed, the impurity may temporarily take the form of a dense liquid layer. However, impurities typically precipitate from solution as amorphous solids (e.g., amorphous (monomer) dithiazides), which are highly insoluble under conventional oil and / or gas operating conditions. It has been found that, in some, but not necessarily all, monomeric dithiazides can harmfully polymerize to form additional impurities, such as trithianes, which increases the difficulty and complexity of removing total solid impurities. Consequently, solid impurities can accumulate on the internal surfaces of machinery, causing blockages, clogging, damage, and ultimately malfunctions of various components.

[0016] In addition, conventional hydrogen sulfide scavengers are frequently used in industries other than oil and gas operations. For example, in addition to their use in oil and gas operations to remove hydrogen sulfide or other organosulfur compounds, triazine compounds can be used in fields such as mining, paper and pulp processing, hydroelectric power plants, coal-fired power plants, and municipal water supply facilities. It is to be understood that the term "hydrogen sulfide scavenger" as used in this application is neither limited to oil and gas operations nor to the intended function of the compound. That is, the hydrogen sulfide scavengers of this disclosure remain so when they are not explicitly intended for reacting with or otherwise chelating hydrogen sulfide.

[0017] This disclosure provides compositions and methods for reducing or mitigating the formation and / or accumulation of these solid impurities. Solid impurities may be, for example, sulfur-containing impurities, such as sulfur-containing compounds. In some cases, the solid impurity is part of a solid sulfur-containing impurity composition. The sulfur-containing impurity composition contains solid impurities that may be sulfur-containing compounds.

[0018] In some embodiments, this disclosure relates to the use of nitrile compounds in dissolving solid impurities (sulfur-containing impurity compositions) generated by the reaction of conventional hydrogen sulfide scavengers, such as triazine compounds, with hydrogen sulfide. The inventors have discovered that the nitrile compounds described herein exhibit high solubility for solid impurities that may form during conventional oil and gas operations. In other words, solid impurities readily dissolve (or remain dissolved without precipitating) in the nitrile compounds described herein (solutions containing the nitrile compounds described herein).

[0019] This disclosure also relates to a method for treating a (solid) sulfur-containing impurity composition comprising a sulfur-containing compound. The method comprises contacting the sulfur-containing compound in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition, which thus comprises a reduced amount of the sulfur-containing compound and optionally trithiane, preferably in small amounts.

[0020] In some aspects, this disclosure provides a solvent solution comprising a nitrile compound and a hydrogen sulfide scavenger. When these solvent solutions are used (e.g., in oil and gas operations), the hydrogen sulfide scavenger preferentially reacts with hydrogen sulfide to produce solid impurities, and the nitrile compound advantageously dissolves the solid impurities (e.g., by redissolving precipitated solid impurities and / or by keeping the solid impurities dissolved in the solution without precipitation). In other aspects, this disclosure also provides methods for using the solvent solutions and / or nitrile compounds described herein, for example for reducing and / or removing hydrogen sulfide, for dissolving dithiazides, and / or for removing solid impurities.

[0021] In some cases, this disclosure relates to a method for suppressing the formation of polymeric sulfur-containing compounds, such as trithiane, in a sulfur-containing impurity composition comprising sulfur-containing compounds. The method involves adding a nitrile compound to the sulfur-containing impurity composition to form a treated sulfur-containing impurity composition, wherein at least some of the sulfur-containing compounds in the sulfur-containing impurity composition are dissolved. The treated sulfur-containing impurity composition contains a reduced amount of monomeric sulfur-containing compounds, and the treated sulfur-containing impurity composition contains less than 50% by weight of a polymeric sulfur-containing compound, such as trithiane.

[0022] In some respects, nitrile compounds can be used (e.g., alone) to dissolve solid impurities. Some nitrile compounds are known and commercially available. However, it has been unexpectedly found that the disclosed nitrile compounds are effective for the uses and methods described herein. Conventional teachings have not indicated that the disclosed nitrile compounds are used for these purposes.

[0023] Nitrile compounds

[0024] This document describes many nitrile compounds, which the inventors have found advantageously to dissolve solid impurities that may be insoluble (e.g., poorly soluble) in conventional solvents. Therefore, nitrile compounds can be used to dissolve (e.g., redissolve or retain dissolution) the solid impurities described herein. Furthermore, nitrile compounds can be used in dissolver solutions comprising a nitrile compound and a hydrogen sulfide scavenger (e.g., reacting with hydrogen sulfide to produce solid impurities).

[0025] Nitrile compounds can be any organic compound containing one or more cyano or nitrile functional groups. The inventors have discovered that the presence of these nitrile compounds can advantageously provide increased solubility for a variety of solid impurities. For example, nitrile compounds can preferentially dissolve (e.g., redissolve or retain dissolution) solid impurities precipitated during desulfurization processes in oil and gas operations. The presence and / or accumulation of solid precipitates, such as on the inner surfaces of processing equipment, pipes, containers, storage tanks, transport tanks, or water treatment wells, can lead to blockages in machinery, requiring cleaning or replacement. By dissolving solid impurities, nitrile compounds reduce or eliminate the accumulation of solid impurities on surfaces. Furthermore, the solubility of solid impurities in nitrile compounds allows for the use of nitrile compounds (e.g., solutions containing nitrile compounds) in the cleaning of machinery. This disclosure contemplates the use of nitrile compounds to dissolve solid impurities in many such applications (some of which are mentioned above as non-limiting examples).

[0026] In some embodiments, the nitrile compound is a trinitrile compound, such as an organic compound having three cyano or nitrile functional groups on a saturated or unsaturated carbon chain. For example, in some embodiments, the nitrile compound is a trinitrile alkane, such as an organic compound having the chemical formula CxH2x-1(CN)3, where x is 4 to 10. Exemplary trinitrile compounds include butanetrinitrile (e.g., tricyanobutane), pentanetrinitrile (e.g., tricyanopentane), hexanetrinitrile (e.g., tricyanohepane), heptanetrinitrile (e.g., tricyanohepane), octanetrinitrile (e.g., tricyanooctane), nonanetrinitrile (e.g., tricyanononane), and decanetrinitrile (e.g., tricyanodecane), and combinations thereof. In some embodiments, the trinitrile compound comprises tricyanohexane, such as 1,3,6-tricyanohexane and / or 1,3,5-tricyanohexane.

[0027] In terms of chemical structure, the trinitrile compound may have a structure in which a, b, and c are independently 0 to 4. In some embodiments, the sum of a, b, and c is 3 to 10.

[0028] In some embodiments, the nitrile compound is a dinitrile compound, such as an organic compound having two cyano or nitrile functional groups on a saturated or unsaturated carbon chain. For example, in some embodiments, the nitrile compound is a dinitrile alkane, such as an organic compound having the chemical formula CxH2x(CN)2, where x is 1 to 6. Exemplary dinitrile compounds include malononitrile (e.g., dicyanomethane), butadionitrile (e.g., dicyanoethane), glutaronitrile (e.g., dicyanopropane), adiponitrile (e.g., dicyanobutane), pentane dinitrile (e.g., dicyanopentane), and hexane dinitrile (e.g., dicyanohexane).

[0029] In some embodiments, the nitrile compound is a mononitrile compound, such as an organic compound having a cyano or nitrile functional group on a saturated or unsaturated carbon chain. For example, in some embodiments, the nitrile compound is a nitrile alkane, such as an organic compound having the chemical formula CxH2x+1(CN), where x is 1 to 6. Exemplary nitrile compounds include acetonitrile (e.g., cyanomethane), propionitrile (e.g., cyanoethane), butyronitrile (e.g., cyanopropane), valeronitrile (e.g., cyanobutane), pentane nitrile (e.g., cyanopentane), and hexanilide (e.g., cyanohexane).

[0030] In some embodiments, the nitrile compound comprises a mixture of the above-described compounds. For example, a combination of one or more trinitrile, dinitrile, and / or mononitrile compounds may be used. It is envisioned that in some cases, the nitrile compound may be used without a hydrogen sulfide scavenger (e.g., the solvent solution may contain only the nitrile compound), for example, to dissolve solid impurities in a variety of applications, including but not limited to oil and gas operations, mining, paper and pulp processing, hydroelectric power plants, coal-fired power plants, and municipal water supply facilities.

[0031] When incorporated into the dissolver solution, the content of nitrile compounds present in the dissolver solution is not particularly limited and can vary widely. In one embodiment, the dissolver solution comprises 0.1 vol% to 20 vol% of a nitrile compound, such as 0.1 vol% to 18.5 vol%, 0.1 vol% to 17 vol%, 0.1 vol% to 15.5 vol%, 0.1 vol% to 12 vol%, 0.2 vol% to 20 vol%, 0.2 vol% to 18.5 vol%, 0.2 vol% to 17 vol%, 0.2 vol% to 15.5 vol%, 0.2 vol% to 12 vol%, 0.5 vol% to 20 vol%, 0.5 vol% to 18.5 vol%, 0.5 vol% to 17 vol%, 0.5 vol% to 15.5 vol%, 0.5 vol% to 12 vol%, 0.8 vol% to 20 vol%, 0.8 vol% to 18.5 vol%, 0.8 vol% to 17 vol%, 0.8 vol% to 15.5 vol%, or 0.8 vol% to 12 vol%. With regard to the lower limit, the dissolver solution may contain more than 0.1 vol% of nitrile compound, for example, more than 0.2 vol%, more than 0.5 vol%, or more than 0.8 vol%. With regard to the upper limit, the dissolver solution may contain less than 20 vol% of nitrile compound, for example, less than 18.5 vol%, less than 17 vol%, less than 15.5 vol%, or less than 12 vol%.

[0032] In some cases, the content of nitrile compounds present in the dissolver solution may be relatively high. In one embodiment, for example, the dissolver solution contains 15 vol% to 85 vol% of nitrile compounds, such as 15 vol% to 80 vol%, 15 vol% to 75 vol%, 15 vol% to 70 vol%, 15 vol% to 65 vol%, 20 vol% to 85 vol%, 20 vol% to 80 vol%, 20 vol% to 75 vol%, 20 vol% to 70 vol%, 20 vol% to 65 vol%, 25 vol% to 85 vol%, 25 vol% to 80 vol%, 25 vol% to 75 vol%, 25 vol% to 70 vol%, 25 vol% to 65 vol%, 30 vol% to 85 vol%, 30 vol% to 80 vol%, 30 vol% to 75 vol%, 30 vol% to 70 vol%, or 30 vol% to 65 vol%. With regard to the lower limit, the dissolver solution may contain more than 15% by volume of nitrile compound, for example, more than 20% by volume, more than 25% by volume, or more than 30% by volume. With regard to the upper limit, the dissolver solution may contain less than 85% by volume of nitrile compound, for example, less than 80% by volume, less than 75% by volume, less than 70% by volume, or less than 65% by volume.

[0033] Hydrogen sulfide scavenger

[0034] The dissolving solution described herein contains, in addition to nitrile compounds, a hydrogen sulfide scavenger. Hydrogen sulfide scavengers can vary widely, and many are known.

[0035] The hydrogen sulfide scavenger can be any organic or inorganic compound that selectively reacts with or otherwise chelates and / or removes hydrogen sulfide (or other organic sulfide components) from the fluid stream. Preferably, the hydrogen sulfide scavenger converts the sulfide components into a more inert form through an irreversible reaction.

[0036] In some embodiments, the hydrogen sulfide scavenger may comprise an inorganic compound. For example, the hydrogen sulfide scavenger may comprise a metal compound, such as a copper-containing compound (e.g., copper carbonate), an iron-containing compound (e.g., iron oxide), or a zinc-containing compound (e.g., zinc carbonate or zinc oxide), which may react to form insoluble copper sulfide. As another example, the hydrogen sulfide scavenger may comprise hydrogen peroxide, which may react to form free sulfur.

[0037] In some embodiments, the hydrogen sulfide scavenger may comprise an organic compound. For example, the hydrogen sulfide scavenger may comprise a nitrogen-containing compound, such as a nitrogen-containing heterocycle. In some embodiments, the hydrogen sulfide scavenger comprises a triazine (e.g., a triazine derivative). In other words, the hydrogen sulfide scavenger may be a triazine compound. Exemplary triazine compounds include triazine (e.g., s-triazine), hexahydro-triazine (e.g., hexahydro-s-triazine), hexahydro-1,3,5-tri(methyl)-s-triazine, hexahydro-1,3,5-tri(ethyl)-s-triazine, hexahydro-1,3,5-tri(propyl)-s-triazine, hexahydro-1,3,5-tri(butyl)-s-triazine, hexahydro-1,3,5-tri(butyl)-s-triazine, hexahydro-1,3,5-tri(hydroxymethyl)-s-triazine, hexahydro-1,3,5-tri(hydroxyethyl)-s-triazine, hexahydro-1,3,5-tri(hydroxypropyl)-s-triazine, hexahydro-1,3,5-tri(hydroxybutyl)-s-triazine, hexahydro-1,3,5-tri(hydroxypentyl)-s-triazine, and combinations thereof.

[0038] In terms of chemical structure, the hydrogen sulfide scavenger may have the structure: , wherein R1, R2, and R3 are independently hydrogen, C1-C5 alkyl, C2-C5 alkenyl, or C1-C5 alcohol groups. In some embodiments, for example, R1, R2, and R3 are each a C1-C5 alcohol group, such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, and / or hydroxypentyl.

[0039] Commercially available hydrogen sulfide removers include PureMark products from Foremark, GasTreat products from Nalco, MEA Traizine products from Hexion, and Sulfix from Baker Hughes.

[0040] The content of hydrogen sulfide scavenger present in the dissolver solution is not particularly limited and can vary widely. In one embodiment, the dissolver solution contains 15 vol% to 85 vol% of hydrogen sulfide scavenger, for example 15 vol% to 80 vol%, 15 vol% to 75 vol%, 15 vol% to 70 vol%, 15 vol% to 65 vol%, 20 vol% to 85 vol%, 20 vol% to 80 vol%, 20 vol% to 75 vol%, 20 vol% to 70 vol%, 20 vol% to 65 vol%, 25 vol% to 85 vol%, 25 vol% to 80 vol%, 25 vol% to 75 vol%, 25 vol% to 70 vol%, 25 vol% to 65 vol%, 30 vol% to 85 vol%, 30 vol% to 80 vol%, 30 vol% to 75 vol%, 30 vol% to 70 vol%, or 30 vol% to 65 vol%. With regard to the lower limit, the dissolver solution may contain more than 15% by volume of hydrogen sulfide scavenger, such as more than 20% by volume, more than 25% by volume, or more than 30% by volume. With regard to the upper limit, the dissolver solution may contain less than 85% by volume of hydrogen sulfide scavenger, such as less than 80% by volume, less than 75% by volume, less than 70% by volume, or less than 65% by volume.

[0041] Additional components

[0042] The dissolver solution described herein may contain other (optional) components besides nitrile compounds and hydrogen sulfide scavengers. These additional components may provide further functionality to the dissolver solution. For example, additional components may stabilize the dissolver solution or facilitate its use.

[0043] In some embodiments, the nitrile compound and the hydrogen sulfide scavenger are dispersed (e.g., dissolved) in a solvent. In some embodiments, the nitrile compound is used in the absence of a hydrogen sulfide scavenger, but is dispersed (e.g., dissolved) in a solvent. Without being constrained by any mechanism or theory, the dissolver solution described herein may contain any solvent. In some cases, the solvent is an aqueous solvent, such as water. In some cases, the solvent is an organic solvent, such as pentane, hexane, methanol, ethanol, propanol (e.g., n-propanol or isopropanol), acetone, benzene, toluene, xylene. There is no particular limitation on the amount of solvent present in the dissolver solution. In some cases, the solvent constitutes the remainder of the dissolver solution. For example, the dissolver solution may contain a volume percentage of the nitrile compound and hydrogen sulfide compound (and any additional components), with the remainder being solvent.

[0044] In some embodiments, the dissolver solution further comprises additional components such as acids, dispersants, thickeners, lubricants, scale inhibitors, friction reducers, crosslinking agents, surfactants, pH adjusters, iron control agents, demulsifiers, or combinations thereof. In some embodiments, nitrile compounds are used in the absence of hydrogen sulfide scavengers, but in mixture with any of these additional components.

[0045] In some embodiments, the dissolver solution further comprises a surfactant. In some embodiments, the nitrile compound is used in the absence of a hydrogen sulfide scavenger, but is mixed with a surfactant. The surfactant reduces the surface tension of the entire composition and improves the dispersion and solubility of solid impurities. Examples of suitable surfactants include sorbitol fatty acid ester ethoxylates (e.g., Tween 40), alkylphenol alcohol ethoxylates (e.g., NP-9, NP-4), nonionic polymeric surfactants (e.g., CRODA Hypermer A70), cationic surfactants (ethoxylated tallow alkylmonium ethosulfate, Crodaquat TES), and sorbitol monooleate (e.g., SPAN 80).

[0046] Solid impurities

[0047] As described above, the reaction of hydrogen sulfide scavengers, such as triazine compounds, with hydrogen sulfide produces solid impurities. The accumulation of these solid impurities on the internal surfaces of machinery can lead to blockages, clogging, damage, and ultimately malfunctions of various components in oil and gas operations. Various solid impurities can be formed in various processes using hydrogen sulfide scavengers, such as in oil and gas operations, and it has been advantageously found that the nitrile compounds described herein (alone and / or as components of the dissolver solution) dissolve these solid impurities.

[0048] In some embodiments, the solid impurity is a reaction product of a hydrogen sulfide scavenger with hydrogen sulfide and / or other sulfide components. In some specific embodiments, the solid impurity is a product of a triazine compound and hydrogen sulfide. In some cases, the solid impurity comprises an organic compound having a six-membered ring containing three nitrogen and / or sulfur heteroatoms. For example, the solid impurity may comprise a thiadiazine compound, a dithiazine compound, or a combination thereof. In terms of chemical structure, the solid impurity may have the following structure: , where R is hydrogen, a C1-C5 alkyl, a C2-C5 alkenyl, or a C1-C5 alcohol group. In some embodiments, for example, R is a C1-C5 alcohol group, such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, and / or hydroxypentyl.

[0049] In some embodiments, the hydrogen sulfide scavenger is an azide-based compound having the structure previously discussed, the solid impurity having the above-described structure, and the R functional group being equivalent to the R1, R2, and / or R3 functional groups of the azide-based compound. For example, the hydrogen sulfide scavenger may comprise hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine, and the solid impurity may comprise 5-hydroxyethyl-1,3,5-dithiazine.

[0050] In some cases, solid impurities may contain amorphous dithiazides. For example, solid impurities may contain amorphous products and / or derivatives of dithiazide compounds produced by the reaction of a hydrogen sulfide scavenger with hydrogen sulfide and / or other sulfide components. The chemical structures of amorphous dithiazides and their formation mechanisms are described in Grahame N. Taylor & Ron Matherly, Structural Elucidation of the Solid Byproduct from the Use of 1,3,5,-Tris(2-hydroxyethyl)hexahydro-s-triazine Based Hydrogen Sulfide Scavengers50 Ind. Eng. Chem. Res. 735 (2011), which is incorporated herein by reference.

[0051] In some embodiments, the solid impurity comprises an inorganic sulfur compound. In some cases, for example, the solid impurity comprises metal sulfides such as iron sulfide (e.g., pyrite), lead sulfide (e.g., galena), zinc sulfide (e.g., sphalerite), silver sulfide (e.g., argentite), mercuric sulfide (e.g., cinnabar), molybdenum sulfide (e.g., molybdenite), nickel sulfide (e.g., pyrite), arsenic sulfide (e.g., realgar), antimony sulfide (e.g., stibnite), iron-copper sulfides (e.g., chalcopyrite), or combinations thereof. In some cases, the solid impurity comprises sulfates such as calcium sulfate (e.g., gypsum, hemihydrate, anhydrous gypsum), strontium sulfate (e.g., celestite), lead sulfate (e.g., lead sulfate), barium sulfate (e.g., barite), or combinations thereof.

[0052] In some embodiments, the solid impurity contains elemental sulfur.

[0053] Solid impurities, such as dithiazide compounds, are generally insoluble in oils and gaseous fluids. Therefore, solid impurities precipitate from the solution as solids and may subsequently accumulate on machinery. However, the inventors have discovered that nitrile compounds (and solvent solutions containing nitrile compounds) exhibit high solubility for solid impurities. That is, nitrile compounds can redissolve precipitated solid impurities and / or retain solid impurities as solutes (e.g., by reducing or eliminating precipitation). The tendency of solid impurities (e.g., dithiazide compounds) to dissolve in nitrile compounds can be quantified by solubility, which indicates the maximum amount of solid impurities (e.g., dithiazide compounds) that dissolve in nitrile compounds at a given temperature.

[0054] As mentioned above, the nitrile compounds mentioned above have an unexpected ability to dissolve solid impurities. In other words, the solubility of solid impurities (such as dithiazide compounds) in nitrile compounds is surprisingly high. For example, the solubility at 70℉ can be from 0.01 kg / l to 20 kg / l, such as 0.01 kg / l to 18 kg / l, 0.01 kg / l to 16 kg / l, 0.01 kg / l to 14 kg / l, 0.01 kg / l to 12 kg / l, 0.02 kg / l to 20 kg / l, 0.02 kg / l to 18 kg / l, 0.02 kg / l to 16 kg / l, 0.02 kg / l to 14 kg / l, 0.02 kg / l to 12 kg / l, 0.04 kg / l to 20 kg / l, 0.04 kg / l to 18 kg / l, 0.04 kg / l to 16 kg / l, 0.04 kg / l to 14 kg / l, 0.04 kg / l to 12 kg / l, 0.06 kg / l to 20 kg / l, 0.06 kg / l to 18 kg / l. kg / l, 0.06 kg / l to 16 kg / l, 0.06 kg / l to 14 kg / l, 0.06 kg / l to 12 kg / l, 0.08 kg / l to 20 kg / l, 0.08 kg / l to 18 kg / l, 0.08 kg / l to 16 kg / l, 0.08 kg / l to 14 kg / l, or 0.08 kg / l to 12 kg / l. With respect to the lower limit, the solubility of solid impurities (e.g., dithiazide compounds) in nitrile compounds at 70℉ can be greater than 0.01 kg / l, for example greater than 0.02 kg / l, greater than 0.04 kg / l, greater than 0.06 kg / l, or greater than 0.08 kg / l. In terms of upper limits, the solubility of solid impurities (e.g., dithiazide compounds) in nitrile compounds at 70℉ can be less than 20 kg / l, for example less than 18 kg / l, less than 16 kg / l, less than 14 kg / l or less than 12 kg / l.

[0055] In some embodiments, the solubility of a solid impurity (e.g., a dithiazide compound) in a nitrile compound at 125℉ is 0.5 kg / l to 50 kg / l, for example 0.5 kg / l to 45 kg / l, 0.5 kg / l to 40 kg / l, 0.5 kg / l to 35 kg / l, 0.6 kg / l to 50 kg / l, 0.6 kg / l to 45 kg / l, 0.6 kg / l to 40 kg / l, 0.6 kg / l to 35 kg / l, 0.8 kg / l to 50 kg / l, 0.8 kg / l to 45 kg / l, 0.8 kg / l to 40 kg / l, 0.8 kg / l to 35 kg / l, 1 kg / l to 50 kg / l, 1 kg / l to 45 kg / l, 1 kg / l to 40 kg / l, or 1 kg / l to 35 kg / l. With regard to the lower limit, the solubility of solid impurities (e.g., dithiazide compounds) in nitrile compounds at 125℉ can be greater than 0.5 kg / l, for example greater than 0.6 kg / l, greater than 0.8 kg / l, or greater than 1 kg / l. With regard to the upper limit, the solubility of solid impurities (e.g., dithiazide compounds) in nitrile compounds at 125℉ can be less than 50 kg / l, for example less than 45 kg / l, less than 40 kg / l, or less than 35 kg / l.

[0056] Sulfur-containing impurities

[0057] When a solid sulfur-containing compound in a sulfur-containing impurity composition comes into contact with a nitrile (and optionally undergoes other treatments, such as temperature), a treated sulfur-containing impurity composition is formed.

[0058] The sulfur-containing impurity composition may contain (monomer) sulfur-containing compounds, such as dithiazides. For example, the sulfur-containing impurity composition may contain more than 25% by weight of sulfur-containing compounds based on the total weight of the sulfur-containing impurity composition, such as more than 35% by weight, more than 50% by weight, more than 75% by weight, more than 85% by weight, more than 90% by weight, more than 95% by weight, or more than 99% by weight. In terms of range, the sulfur-containing impurity composition may contain 25% by weight to 100% by weight of sulfur-containing compounds, such as 50% by weight to 100% by weight, 25% by weight to 75% by weight, 35% by weight to 65% by weight, 75% by weight to 100% by weight, 85% by weight to 99.5% by weight, or 90% by weight to 99% by weight. In terms of upper limit, the sulfur-containing impurity composition may contain less than 100% by weight of sulfur-containing compounds, such as less than 95% by weight, less than 90% by weight, less than 75% by weight, less than 50% by weight, or less than 35% by weight.

[0059] The treated sulfur-containing impurity composition may contain a reduced amount of sulfur-containing compounds, such as monomeric dithiazides (reduced compared to the initial sulfur-containing impurity composition). For example, the treated sulfur-containing impurity composition may contain less than 99.5% sulfur-containing compounds based on the total weight of the treated sulfur-containing impurity composition, such as less than 99% by weight, less than 95% by weight, less than 92% by weight, less than 90% by weight, less than 75% by weight, less than 60% by weight, less than 50% by weight, less than 40% by weight, less than 35% by weight, less than 25% by weight, less than 15% by weight, less than 10% by weight, less than 5% by weight, or less than 1% by weight. In terms of range, the treated sulfur-containing impurity composition may contain 0% by weight to 95% by weight of sulfur-containing compounds, such as 0% by weight to 75% by weight, 0% by weight to 50% by weight, 1% by weight to 35% by weight, 5% by weight to 25% by weight, or 10% by weight to 20% by weight. As for the lower limit, the sulfur-containing impurity composition may contain more than 0% by weight of sulfur-containing compounds, such as more than 1% by weight, more than 5% by weight, more than 10% by weight, more than 25% by weight, or more than 50% by weight.

[0060] In some cases, the amount of reduced monomeric sulfur compounds is at least 10% less than the initial amount of sulfur compounds present in the untreated sulfur-containing impurity composition, for example, 15%, 25%, 35%, 50%, at least 75%, or at least 90% less.

[0061] In some embodiments, the monomeric sulfur-containing impurities may polymerize to form polymeric sulfur-containing impurities. In some cases, treatment with a nitrile compound disclosed herein may advantageously delay or prevent such polymerization. As a result of the treatment, the formation (polymerization) of thiazine-containing polymers / compounds, such as trithiazane impurities, from the monomeric dithiazine is also delayed or eliminated. Thus, the treated sulfur-containing impurity composition contains only small amounts of polymeric sulfur-containing compounds, such as thiazine-containing polymers / compounds.

[0062] For example, the treated sulfur-containing impurity composition may contain less than 100% of a polymeric sulfur-containing compound, such as trithiane, for example less than 95%, less than 90 wt%, less than 80 wt%, less than 75 wt%, less than 65 wt%, less than 60 wt%, less than 50 wt%, less than 40 wt%, less than 30 wt%, less than 25 wt%, or less than 10 wt%. In terms of range, the treated sulfur-containing impurity composition may contain 1 ppb to 90 wt% of a polymeric sulfur-containing compound, for example 1 ppm to 90 wt%, 1 wt% to 90 wt%, 10 wt% to 80 wt%, 20 wt% to 75 wt%, 35 wt% to 75 wt%, 40 wt% to 70 wt%, or 45 wt% to 70 wt%. In terms of upper limits, sulfur-containing impurity components may contain more than 1 ppb of polymeric sulfur-containing compounds, such as more than 10 ppm, more than 1% by weight, more than 10% by weight, more than 15% by weight, more than 25% by weight, more than 35% by weight, more than 45% by weight, more than 50% by weight, more than 60% by weight, more than 65% by weight, or more than 75% by weight.

[0063] Dissolve solid impurities

[0064] Given the relatively high solubility of solid impurities (or multiple impurities) in nitrile compounds, the nitrile compounds (and dissolver solutions containing nitrile compounds) described herein can be advantageously used to dissolve (e.g., redissolve or maintain dissolution) solid impurities. Therefore, several embodiments of this disclosure provide methods utilizing dissolver solutions and / or nitrile compounds.

[0065] In some embodiments, nitrile compounds and / or solvent solutions are used to reduce or remove sulfide impurities, such as hydrogen sulfide or organosulfur compounds. In these embodiments, the solvent solution described herein is added to a system containing sulfide impurities. The system containing sulfide impurities may be an element or machinery of an oil and gas operation, such as an element of a desulfurization process. The mechanism for adding the solvent solution to the system is not particularly limited. In some embodiments, the solvent solution is added to the system by direct injection. For example, the solvent solution may be sprayed (e.g., using an atomizing sleeve) or otherwise injected into the fluid stream (e.g., oil, gas, or fluid mixture) of the system containing sulfide impurities. In some embodiments, the solvent solution is added to the system via a contactor, such as a contactor tower. For example, the fluid stream (e.g., oil, gas, or fluid mixture) of the system containing sulfide impurities may be bubbled or otherwise fed through a contactor tower containing the solvent solution. In these embodiments, the hydrogen sulfide scavenger preferentially reacts with the sulfide impurities, and the nitrile compound dissolves (e.g., redissolves and / or retains dissolution) the products of the reaction.

[0066] This disclosure also relates to treating sulfur-containing compositions that may contain solid impurities (as part of a sulfur-containing impurity composition), comprising the step of contacting the solid impurities (in the sulfur-containing impurity composition) with a nitrile compound to form a treated sulfur-containing composition having the composition as described herein.

[0067] In some embodiments, the nitrile compound and / or the dissolver solution is used to dissolve solid impurities, such as dithiazine compounds. In these embodiments, the dissolver solution described herein is added to a system containing impurities. The system containing (sulfide) impurities can be components or machinery in oil and gas operations, such as components of a desulfurization process. Impurities, such as dithiazine, may in some cases be products of the desulfurization process. To remove solids, such as dithiazine, the dissolver solution is introduced into the system containing impurities. The mechanism for adding the dissolver solution to the system is not particularly limited. In this embodiment, the dissolver solution can be used to clean or remove precipitated dithiazine compounds while continuously removing sulfide impurities.

[0068] In some embodiments, nitrile compounds and / or dissolver solutions are used to remove solid impurities, such as dithiazide compounds, from a surface. In these embodiments, the nitrile compounds dissolve the solid impurities. The surface to be cleaned is not particularly limited and can be, for example, components of oil and gas operations or machinery, such as components of desulfurization processes. In some cases, the system containing impurities can be mechanical components on which impurities, such as dithiazide compounds, have precipitated and / or accumulated. In some embodiments, for example, it can be components of oil and / or gas operations, mining operations, paper and pulp processing, hydroelectric power plants, coal-fired power plants, or municipal water supply facilities. Dithiazides may, in some cases, be products of desulfurization processes. To remove solid dithiazides, nitrile compounds are introduced onto the surface. The mechanism for adding a dissolver solution to the system is not particularly limited. In this embodiment, the nitrile compound can be used alone to clean or remove precipitated dithiazide compounds.

[0069] As discussed above, solid impurities are soluble in nitrile compounds at ambient temperature. Therefore, the above method may include the use of nitrile compounds and / or solvent solutions at ambient temperature. In some embodiments, the nitrile compounds and / or solvent solutions are used at temperatures of 50℉ to 90℉, such as 50℉ to 85℉, 50℉ to 80℉, 50℉ to 75℉, 55℉ to 90℉, 55℉ to 85℉, 55℉ to 80℉, 55℉ to 75℉, 60℉ to 90℉, 60℉ to 85℉, 60℉ to 80℉, 60℉ to 75℉, 65℉ to 90℉, 65℉ to 85℉, 65℉ to 80℉, or 65℉ to 75℉. At the lower limit, the nitrile compounds and / or solvent solutions may be used at temperatures greater than 50℉, such as greater than 55℉, greater than 60℉, or greater than 65℉. In terms of upper limits, nitrile compounds and / or solvent solutions can be used at temperatures below 90℉, such as below 85℉, below 80℉, or below 75℉.

[0070] The solubility of solid impurities in nitrile compounds increases with increasing temperature. Therefore, the above method may further include heating the nitrile compound and / or the solvent solution (and optionally heating the solid impurity or the solution containing the solid impurity) to an elevated temperature. In some embodiments, the nitrile compound and / or the solvent solution is heated to a temperature of 90℉ to 400℉, for example, 90℉ to 390℉, 90℉ to 380℉, 90℉ to 375℉, 100℉ to 400℉, 100℉ to 390℉, 100℉ to 380℉, 100℉ to 375℉, 110℉ to 400℉, 110℉ to 390℉, 110℉ to 380℉, 110℉ to 375℉, 115℉ to 400℉, 115℉ to 390℉, 115℉ to 380℉, or 115℉ to 375℉. With respect to the lower limit, the nitrile compound and / or the solvent solution can be heated to a temperature greater than 90℉, such as greater than 100℉, greater than 110℉, or greater than 115℉. With respect to the upper limit, the nitrile compound and / or the solvent solution can be heated to a temperature less than 400℉, such as less than 390℉, less than 380℉, or less than 375℉.

[0071] The dissolution of solid impurities in nitrile compounds may require prolonged exposure of the solid impurities to the nitrile compounds. Therefore, the above method may further include allowing an extended period of time for the solid impurities (e.g., dithiazide compounds) to dissolve. In some embodiments, the solid impurities (e.g., dithiazide compounds) are exposed to the nitrile compounds for 0.5 hours to 48 hours, for example, 0.5 hours to 120 hours, 0.5 hours to 96 hours, 0.5 hours to 72 hours, 0.5 hours to 48 hours, 1 hour to 48 hours, 1 hour to 120 hours, 1 hour to 96 hours, 1 hour to 72 hours, 1 hour to 48 hours, 1.5 hours to 48 hours, 1.5 hours to 120 hours, 1.5 hours to 96 hours, 1.5 hours to 72 hours, 1.5 hours to 48 hours, 2 hours to 48 hours, 2 hours to 120 hours, 2 hours to 96 hours, 2 hours to 72 hours, or 2 hours to 48 hours. With regard to the lower limit, the solid impurity may be exposed to the nitrile compound for at least 0.5 hours, such as at least 1 hour, at least 1.5 hours, or at least 2 hours. With regard to the upper limit, the solid impurity may be exposed to the nitrile compound for less than 48 hours, such as less than 120 hours, less than 96 hours, less than 72 hours, or less than 48 hours.

[0072] Trithiazide inhibition

[0073] In some cases, the dissolution of dithiazides can be used to delay the formation of impurities formed by dithiazides (dithiazide monomers). Some examples of impurities formed by dithiazide monomers are thianes, such as trithianes.

[0074] In some embodiments, this disclosure relates to a method for suppressing the formation (polymerization) of sulfur-containing compounds, such as (polymerization) thiazide polymers / compounds, for example trithiaane, in a sulfur-containing impurity composition containing a sulfur-containing compound, such as dithiazide. The polymerized sulfur-containing compound may be a polymer containing (monomer) dithiazide or formed from (monomer) dithiazide. The method includes the step of adding a nitrile compound, such as hexanetrionitrile (optionally in a dissolver solution), to the sulfur-containing impurity composition. Thereby, the nitrile compound dissolves at least some of the dithiazide in the sulfur-containing impurity composition to form a treated sulfur-containing impurity composition. In some cases, the treated sulfur-containing impurity composition contains a reduced amount of (monomer) sulfur-containing compound (dithiazide), or in some cases, contains no monomeric sulfur-containing compound. Thus, the formation (polymerization) of thiazide polymers / compounds, such as trithiaane, from monomeric dithiazide is delayed or eliminated. In other words, trithiaane is formed almost or completely because the monomeric dithiazide used to form it is almost or completely absent. The amount of trithiazide (or other (polymerized) thiazide-containing polymers / compounds) in the treated sulfur-containing impurity composition may be as discussed herein.

[0075] In some cases, the treated sulfur-containing impurity composition contains less than 100% by weight of (polymerized) thiazide-containing polymers / compounds, such as trithiazide (see the discussion above for the composition of the treated sulfur-containing impurity composition).

[0076] In some embodiments, any or some of the steps or elements disclosed herein may be considered optional. In some cases, any or some of the foregoing items in this specification may be explicitly excluded, for example, by the wording of the claim. For example, the wording of the claim may be modified to indicate that the composition does not contain or exclude castor oil.

[0077] As used herein, the boundaries of "greater than" and "less than" may also include the digits associated with them. In other words, "greater than" and "less than" can be interpreted as "greater than or equal to" and "less than or equal to". It is contemplated that this wording may subsequently be modified in the request to include "or equal to". For example, "greater than 4.0" could be interpreted as, and subsequently modified in the request to, "greater than or equal to 4.0".

[0078] Example

[0079] This disclosure can be further understood by referring to the following non-limiting embodiments.

[0080] Example 1

[0081] Run tests were conducted to evaluate the solubility of the nitrile compound in the hydrogen sulfide scavenger and thereby determine the composition of the solvent solution. A 60% (v / v) aqueous solution of hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine was used as the hydrogen sulfide scavenger. Hexanetrionitrile was used as the nitrile compound.

[0082] Five samples, 5 mL each, were prepared by adding nitrile compounds to a hydrogen sulfide scavenger. Different amounts of nitrile compounds were added to prepare samples containing 1 vol%, 2 vol%, 3 vol%, 4 vol%, and 5 vol% nitrile compounds, respectively, with the remainder being hydrogen sulfide scavenger. Each sample was shaken until visually homogeneous and allowed to settle and separate. After initial separation, the samples were shaken again to ensure maximum dissolution, and then the separation was evaluated.

[0083] For each sample, shaking produces an emulsion, which is advantageously stable for up to 1 hour before separation is observed. Therefore, all samples are highly stable. In particular, samples containing 1 vol% and 2 vol% nitrile compounds do not completely separate at any point; instead, the small droplets of nitrile compounds aggregate only on the surface. Therefore, dissolver solutions containing approximately 1-2 vol% are found to be particularly stable and effective. Thus, some nitrile solutions / compositions can be effective at concentrations below 100 vol%, for example, less than 75 vol%, less than 50 vol%, less than 35 vol%, less than 25 vol%, less than 15 vol%, less than 10 vol%, less than 5 vol%, or less than 3 vol%.

[0084] Example 2

[0085] Run tests were conducted to evaluate the solubility of solid impurities in nitrile compounds. Hexanetrionitrile was used as the nitrile compound. Two samples of dithiazine compounds were used as solid impurities: the "laboratory sample" was generated by continuously bubbling a 40 vol% hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine solution with a mixture of hydrogen sulfide and nitrogen until separation occurred, and the "field sample" was a sample of amorphous dithiazine collected from the contactor tower of the desulfurization process.

[0086] In the first test, the solubility of the laboratory sample in the nitrile compound was evaluated. The sample was prepared by mixing solid dithiazide from the laboratory sample with the nitrile compound. The sample was heated to 70℉ and 125℉ for 24 hours. After 24 hours, undissolved solid impurities were recovered, rinsed with cold isopropanol, air-dried, and weighed. The amount of dissolved solid impurities was determined and used to calculate the solubility of the laboratory sample. The results of this test are reported in Table 1.

[0087] Table 1: Laboratory Sample Testing Example 1 Example 2 Temperature (℉) 70 125 Contact time (hours) twenty four twenty four Nitrile compounds (g) 25.03 25.01 Initial solid impurities (g) 5.13 5.16 Final solid impurities (g) 4.84 4.24 Solubility (g) 0.29 0.92 Calculate solubility (kg / l) 0.012 0.038

[0088] As shown in Table 1, the nitrile compounds dissolve the laboratory samples surprisingly effectively. In particular, the calculated solubility at 125℉ is ~0.04 kg / l.

[0089] In the second test, the solubility of the field sample in the nitrile compound was evaluated. The sample was prepared by mixing solid dithiazide from the field sample with the nitrile compound. The sample was heated to 70℉ and 125℉ for 2 hours or 24 hours. After this time, undissolved solid impurities were recovered, rinsed with cold isopropanol, air-dried, and weighed. The amount of dissolved solid impurities was determined and used to calculate the solubility of the laboratory sample. The results of this test are reported in Table 2.

[0090] Table 2: Field Sample Testing Example 3 Example 4 Example 5 Example 6 Temperature (℉) 70 70 125 125 Contact time (hours) 2 twenty four 2 2 Nitrile compounds (g) 10.02 10.01 10.7 5.08 Initial solid impurities (g) 12.28 12.45 12.65 45.82 Final solid impurities (g) 11.24 7.559 0 1.186 Solubility (g) 1.040 4.891 12.65 44.63 Calculate solubility (kg / l) 0.107 0.506 >1.30 3.92

[0091] As shown in Table 2, the nitrile compounds surprisingly dissolved the field samples effectively at 70℉. Furthermore, Examples 3 and 4 showed that after 2 hours at a lower temperature of 70℉, the solid impurities had significantly dissolved, but not completely. Interestingly, further exposure of the solid impurities to the nitrile compounds, for example, for 24 hours, showed a higher solubility than after 2 hours. This result indicates that using extended contact time can further improve the dissolution effect.

[0092] As shown in Table 2, the nitrile compounds surprisingly dissolved the field samples effectively at 125℉. Within the first two hours, all the solid impurities in Example 5 had dissolved. Therefore, the actual solubility of the solid impurities was greater than the calculated solubility because saturation was not reached (as indicated by ">" in Table 2). However, in Example 6, the solid impurities did not completely dissolve (i.e., saturation was reached), so the full solubility could be calculated. Examples 5-6 demonstrate the unexpected effectiveness of the nitrile compounds in dissolving solid dithiazine impurities.

[0093] In the comparative test, alternative solvents were tested to assess the relative solubility of the field samples. Samples were prepared by mixing solid dithiazide from the field samples with 20 mL of various solvents. The samples were heated to 70°F for 2 hours or 24 hours. After this time, undissolved solid impurities were recovered, rinsed with cold isopropanol, air-dried, and weighed. The amount of dissolved solid impurities was determined and used to calculate the solubility of the laboratory samples. The results of this test are reported in Table 3. Hexanetrionitrile (samples 3 and 4) are included for comparison.

[0094] Table 3: Comparison of field sample tests Comparative Example A Comparative Example B Comparative Example C Comparative Example D solvent methanol ethanol Isopropanol Ethylene glycol Contact time (hours) 2 twenty four 2 twenty four 2 twenty four 2 twenty four Initial solid impurities (g) 5.31 10.18 5.36 5.57 5.48 5.32 5.15 5.06 Final solid impurities (g) 0.849 2.070 1.477 1.472 4.061 4.005 6.603 3.467 Calculate solubility (kg / l) 0.2233 0.405 0.194 0.204 0.070 0.065 0 0.054 Comparative Example E Comparative Example F Comparative Example G Example 3 / Example 4 diethylene glycol Propylene glycol acetone nitrile compound Contact time (hours) 2 twenty four 2 twenty four 2 twenty four 2 twenty four Initial solid impurities (g) 5.52 5 5.02 5 5.78 10 12.28 12.45 Final solid impurities (g) 6.825 3.911 5.650 2.995 1.124 2.584 11.24 7.559 Calculate solubility (kg / l) 0 0.054 0 0.100 0.232 0.370 0.107 0.506

[0095] As shown in Table 3, the nitrile compounds exhibited comparable solubility in the field samples after 2 hours. However, after 24 hours, the nitrile compounds showed the highest solubility of 0.506 kg / l, which is significantly higher than the 0.4 kg / l shown by methanol, which was the best performing comparative solvent. Furthermore, the nitrile compounds have a significantly lower flash point than methanol. Therefore, when flammability is a concern (in refineries), nitrile compounds are advantageous for dissolving solids.

[0096] Example 3

[0097] A run test was conducted to evaluate the ability of the dissolver solution to react with sulfide impurities and dissolve the products. A dissolver solution (Example 8) was prepared by mixing 20 mL of a 60 vol% aqueous solution of hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine with 3.6 mL of a nitrile compound containing hexanetrionitrile. The resulting dissolver solution contained 15 vol% of the nitrile compound. A comparative example was prepared using 20 mL of a 60 vol% aqueous solution of hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine without the nitrile compound (Comparative Example H).

[0098] In each test, the solution was placed in a test container, and hydrogen sulfide (H2S) gas was supplied to the container. The gas valve was opened at the set flow rate, and hydrogen sulfide was bubbled through the test solution. This treatment continued until no more hydrogen sulfide was consumed—as determined by hydrogen sulfide detection in the carryover sample. At this point, the gas valve was closed, the hydrogen sulfide supply was stopped, and the breakthrough time was recorded. For the dissolver solution, no significant separation between the hydrogen sulfide scavenger and the nitrile compound was observed during or after the test. The results of this test are reported in Table 4.

[0099] Table 4: Scavenger Test Example 7 Comparative Example H Breakthrough time (min) 59.7 61.4 Sulfide removed (mol / gas) 15.28 15.72 Sulfides removed (lb / gal) 1.48 1.181 Solid formation of scavenged sulfides (mol / gas) 25.64 25.63 Solid formation of sludge (lb / gal) 1.927 1.941

[0100] As shown in Table 4, the breakthrough time for hydrogen sulfide occurred at similar times in both tests. This indicates that nitrile compounds do not interfere with the reaction or effectiveness of the hydrogen sulfide scavenger.

[0101] After the above tests were completed, each sample was poured into a vial and allowed to stand at 70℉ for 24 hours. After 24 hours, Comparative Example A had become completely opaque, and solids were visible in the slurry. After 24 hours, Example 7 had only become slightly cloudy, and no solids were visible. This indicates that the presence of nitrile compounds minimizes and / or delays the formation of solid impurities.

[0102] Implementation Plan

[0103] As used below, any reference to a series of implementation schemes is to be understood as referring to each of these implementation schemes separately (e.g., "implementation schemes 1-4" is understood as "implementation schemes 1, 2, 3 or 4").

[0104] Embodiment 1 is a method for removing solid impurities from a surface, such as sulfur-containing compounds optionally present as part of a sulfur-containing impurity composition, the method comprising dissolving the solid impurities with a nitrile compound to preferably form a treated sulfur-containing impurity composition comprising less than 99.5% by weight of a sulfur-containing compound based on the total weight of the treated sulfur-containing impurity composition, and optionally wherein the treated dithiazine composition further comprises 1 ppm to 90% by weight of a polymeric sulfur-containing compound.

[0105] Embodiment 2 is a method of any of the preceding embodiments, wherein the nitrile compound has the chemical formula CxH2x-1(CN)3, where x is 4 to 10.

[0106] Embodiment 3 is a method of any of the foregoing embodiments, wherein the nitrile compound comprises hexanetrionitrile.

[0107] Embodiment 4 is a method of any of the foregoing embodiments, wherein the nitrile compound has the chemical formula CxH2x(CN)2, where x is 1 to 6.

[0108] Embodiment 5 is a method of any of the preceding embodiments, wherein the nitrile compound has the chemical formula CxH2x+1CN, where x is 1 to 6.

[0109] Embodiment 6 is a method of any of the preceding embodiments, wherein the nitrile compound has a chemical structure: , wherein a, b and c are independently 0 to 4.

[0110] Embodiment 7 is a method of any of the foregoing embodiments, wherein the solid impurity comprises a dithiazide compound.

[0111] Embodiment 8 is a method of any of the preceding embodiments, wherein the nitrile compound exhibits a dithiazide solubility of 0.01 kg / l to 20 kg / l at 70℉.

[0112] Embodiment 9 is a method of any of the preceding embodiments, wherein the nitrile compound exhibits a dithiazide solubility of 0.5 kg / l to 50 kg / l at 125℉.

[0113] Embodiment 10 is a solvent solution comprising: a nitrile compound; and a hydrogen sulfide scavenger.

[0114] Embodiment 11 is a dissolver solution of any of the preceding embodiments, wherein the dissolver solution contains 0.1 vol% to 85 vol% of a nitrile compound.

[0115] Embodiment 12 is a dissolver solution of any of the preceding embodiments, wherein the nitrile compound has the chemical formula CxH2x-1(CN)3, where x is 4 to 10.

[0116] Embodiment 13 is a dissolver solution of any of the preceding embodiments, wherein the nitrile compound has a chemical structure: , wherein a, b and c are independently 0 to 4.

[0117] Embodiment 14 is a dissolver solution of any of the preceding embodiments, wherein the nitrile compound comprises hexanetrionitrile.

[0118] Embodiment 15 is a dissolving solution of any of the preceding embodiments, wherein the hydrogen sulfide scavenger comprises a triazine compound.

[0119] Embodiment 16 is a dissolving solution of any of the preceding embodiments, wherein the hydrogen sulfide scavenger comprises hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine.

[0120] Embodiment 17 is a method for dissolving dithiazide, the method comprising adding a dissolving solution of any of the preceding embodiments to a system containing dithiazide.

[0121] Embodiment 18 is a method for treating a solid sulfur-containing impurity composition containing a sulfur-containing compound, the method comprising contacting the sulfur-containing compound in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition containing less than 99.5% by weight of the sulfur-containing compound.

[0122] Embodiment 19 is the method of Embodiment 18, wherein the treated sulfur-containing impurity composition comprises 1 ppm to 90% by weight of trithiane.

[0123] Embodiment 20 is a method for suppressing the formation of polymeric sulfur-containing compounds in a sulfur-containing impurity composition containing sulfur-containing compounds, the method comprising adding a nitrile compound to the sulfur-containing impurity composition, wherein at least some of the monomeric sulfur-containing compounds in the sulfur-containing impurity composition are dissolved to form a treated sulfur-containing impurity composition containing a reduced amount of monomeric sulfur-containing compounds; wherein the treated sulfur-containing impurity composition contains less than 90% by weight of polymeric sulfur-containing compounds.

[0124] Embodiment 21 is the method of Embodiment 20, wherein the amount of reduced monomeric sulfur compound is at least 10% less than the initial amount of sulfur compound present in the sulfur-containing impurity composition.

[0125] Embodiment 22 is the method of Embodiment 20 or 21, wherein the polymeric sulfur-containing compound comprises trithiane. [Simplified Explanation of the Diagram]

[0013] None.

Claims

1. A method for removing a solid sulfur-containing impurity composition comprising a sulfur-containing compound, preferably dithiazine, from a surface, the method comprising dissolving the sulfur-containing compound in the sulfur-containing impurity composition with a nitrile compound, preferably hexanetrionitrile, to form a treated sulfur-containing impurity composition comprising less than 99.5% by weight of the sulfur-containing compound based on the total weight of the treated sulfur-containing impurity composition.

2. The method of claim 1, wherein the treated dithiazine composition further comprises 1 ppm to 90% by weight of a polymeric sulfur-containing compound.

3. The method of claim 1, wherein the nitrile compound has the chemical formula CxH2x-1(CN)3, wherein x is 4 to 10.

4. The method of claim 1, wherein the nitrile compound exhibits dithiazide solubility of 0.01 kg / l to 20 kg / l at 70℉ or 0.5 kg / l to 50 kg / l at 125℉.

5. A dissolving solution comprising: a nitrile compound; and a hydrogen sulfide scavenger.

6. The dissolver solution as claimed in claim 5, wherein the dissolver solution contains 0.1 vol% to 85 vol% of a nitrile compound.

7. The dissolving solution as claimed in claim 5, wherein the nitrile compound has the chemical formula CxH2x-1(CN)3, wherein x is 4 to 10.

8. The dissolver solution as claimed in claim 5, wherein the nitrile compound comprises hexanetrionitrile.

9. The dissolving solution as claimed in claim 5, wherein the hydrogen sulfide scavenger comprises a triazine compound, preferably hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine.

10. A method for dissolving dithiazide, the method comprising: adding the dissolving solution of claim 5 to a system containing dithiazide.

11. A method for treating a solid sulfur-containing impurity composition comprising a sulfur-containing compound, the method comprising contacting the sulfur-containing compound in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition comprising less than 99.5% by weight of the sulfur-containing compound.

12. The method of claim 11, wherein the treated sulfur-containing impurity composition comprises 1 ppm to 90% by weight of trithiane.

13. A method for suppressing the formation of polymeric sulfur-containing compounds in a sulfur-containing impurity composition comprising sulfur-containing compounds, the method comprising: adding a nitrile compound to the sulfur-containing impurity composition, wherein at least some of the monomeric sulfur-containing compounds in the sulfur-containing impurity composition are dissolved to form a treated sulfur-containing impurity composition comprising a reduced amount of the monomeric sulfur-containing compounds; wherein the treated sulfur-containing impurity composition comprises less than 90% by weight of the polymeric sulfur-containing compound.

14. The method of claim 13, wherein the reduced amount of monomeric sulfur compound is at least 10% less than the initial amount of sulfur compound present in the sulfur-containing impurity composition.

15. The method of claim 13, wherein the polymeric sulfur-containing compound comprises trithiane.