Nitrile solvents

Abstract

A method for removing a solid sulfur-containing impurity composition comprising sulfur-containing compounds from a surface, the method comprising the step of dissolving the sulfur-containing compounds in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition, wherein the treated sulfur-containing impurity composition comprises less than 99.5 wt % of the sulfur-containing compounds based on the total weight of the treated sulfur-containing impurity composition.

Description

[0001] Cross-references

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

[0003] field

[0004] The present disclosure generally relates to the use of nitrile compounds as solvents. The present disclosure particularly relates to the use of nitriles, such as tricyanohexane, as solvents (eg, dissolving additives) for impurities in, for example, industrial fluids.

[0005] background

[0006] Hydrogen sulfide (H2S) and other organic sulfide compounds are commonly associated with various oil and gas operations. For example, hydrogen sulfide is present in crude oil as an impurity in small amounts, and natural gas may contain up to 30% hydrogen sulfide. Broadly speaking, hydrogen sulfide and other organic sulfide compounds may 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 for reducing or removing sulfide compounds from these fluids are generally referred to as "desulphurization" methods.

[0007] A common method of reducing or removing sulfide components uses 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 at the wellhead into a water-saturated stream, or into a gas liquid contactor at a processing facility. Hydrogen sulfide scavengers preferentially react with hydrogen sulfide to form less volatile and / or non-volatile products. Conventional hydrogen sulfide scavengers are very effective in removing hydrogen sulfide, and millions of gallons of such scavengers are used each year in North America.

[0008] Nevertheless, the use of hydrogen sulfide scavengers is not without disadvantages. In particular, conventional hydrogen sulfide scavengers produce unwanted products. For example, triazine compounds usually react with hydrogen sulfide to form solid impurities containing amorphous dithiazine, commonly referred to as dithiazine solids. Although these solid impurities are fully soluble under certain temperature and pressure conditions (such as downhole conditions), solid impurities are insoluble under typical conditions. Therefore, a large amount of precipitation of these solid impurities is observed in many oil and gas processing systems. For example, solid impurities may precipitate in transportation and downstream distribution pipelines and facilities. In some cases, the amount of precipitation of solid impurities may be sufficient to form blockages in processing equipment, such as pipelines, containers, storage and transportation tanks, and even wells. The problems associated with the precipitation of solid impurities are well documented and are known to those skilled in the art. When the precipitated solids accumulate on the inner surface of oil and gas equipment and / or its components, a special cleaning procedure is required to ensure normal operation. In some cases, the accumulation may be so serious that the replacement of components is inevitable.

[0009] 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.

[0010] Therefore, there is a need for new methods and chemicals for mitigating the precipitation of solid impurities and / or for cleaning the precipitated solid impurities.

[0011] Overview

[0012] In some aspects, the present disclosure provides a method for removing solid impurities, such as sulfur-containing compounds optionally present as part of a sulfur-containing impurity composition, from a surface, 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 wt % of the sulfur-containing compound based on the total weight of the treated sulfur-containing impurity composition, and optionally wherein the treated dithiazine composition further comprises from 1 ppm to 90 wt % of a polymeric sulfur-containing compound. In some cases, the nitrile compound has the formula C x H 2x-1 (CN)3, wherein x is 4 to 10. In some cases, the nitrile compound comprises hexanetrinitrile. In some cases, the nitrile compound has the chemical formula C x H 2x (CN)2, wherein x is 1 to 6. In some cases, the nitrile compound has the formula C x H 2x+1 CN, wherein x is 1 to 6. In some cases, the nitrile compound has the chemical structure:

[0013]

[0014] Wherein a, b and c are independently 0 to 4. In some cases, the solid impurities include dithiazine compounds. In some cases, the nitrile compound exhibits a dithiazine solubility of 0.01 kg / l to 20 kg / l at 70°F. In some cases, the nitrile compound exhibits a dithiazine solubility of 0.5 kg / l to 50 kg / l at 125°F.

[0015] In some aspects, the present disclosure provides a dissolver solution comprising: a nitrile compound; and a hydrogen sulfide scavenger. In some cases, the dissolver solution comprises the nitrile compound in an amount of 0.1% to 85% by volume. In some cases, the nitrile compound has a chemical formula C x H 2x-1 (CN)3, wherein x is 4 to 10. In some cases, the nitrile compound has the chemical structure:

[0016]

[0017] wherein a, b and c are independently 0 to 4. In some cases, the nitrile compound comprises hexanetrinitrile. 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.

[0018] In some aspects, the present disclosure provides a method of dissolving dithiazine, the method comprising adding the dissolver solution of any of the preceding embodiments to a system containing dithiazine.

[0019] In some embodiments, the present 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 wt % of the sulfur-containing compound and optionally 1 ppm to 90 wt % of trithiane.

[0020] In some embodiments, the present disclosure relates to a method of inhibiting 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 polymeric sulfur-containing compounds, such as trithiane. The reduced amount of monomeric sulfur-containing compounds is optionally at least 10% less than the initial amount of sulfur-containing compounds present in the sulfur-containing impurity composition.

[0021] Details

[0022] introduction

[0023] As described above, it has been confirmed that conventional hydrogen sulfide scavengers produce impurities due to reaction with hydrogen sulfide. For example, 5-(2-hydroxyethyl)dithiazine is produced when the commonly used hydrogen sulfide scavenger hexahydro-1,3,5,-tris(hydroxyethyl)dithiazine is used. See, for example, Jan M.Bakke et al., Hydrolysis of 1,3,5,-Tris(2-hydroxyethyl)hexahydrodithiazine and Its Reaction with H2S, 40IND.ENG.CHEM.RES.6051(2001); Grahame N.Taylor & Ron Matherly, Gas Chromatographic-Mass Spectroscopic Analysisof Chemically Derivatized Hexahydrotriazine-based Hydrogen Sulfide Scavengers: Part II, 49IND.ENG.CHEM.RES.6267(2010). When formed, the impurities may be in the form of a dense liquid layer for a short time. However, typically, the impurities precipitate from solution as amorphous solids (e.g., amorphous (monomer) dithiazine), which are highly insoluble under the conditions of conventional oil and / or gas operations. It has been found that in some, but not necessarily all, cases, dithiazine in monomeric form may detrimentally polymerize to form additional impurities, such as trithiane, which increases the difficulty and complexity of total solid impurity removal. As a result, solid impurities may accumulate on the internal surfaces of machinery to cause clogging, obstruction, damage, and ultimately failure of various components.

[0024] In addition, conventional hydrogen sulfide scavengers are often used in industries other than oil and gas operations. For example, in addition to their use in scavenging hydrogen sulfide or other organic sulfide compounds in oil and gas operations, triazine compounds can also be used in areas such as mining, paper and pulp processing, hydroelectric power plants, coal-fired power plants, and municipal water facilities. It is to be understood that the term "hydrogen sulfide scavenger" as used in this application is not limited to oil and gas operations nor to the intended function of the compound. That is, the hydrogen sulfide scavengers of the present disclosure remain so even when they are not explicitly used for the purpose of reacting with or otherwise chelating hydrogen sulfide.

[0025] The present disclosure provides compositions and methods for reducing or alleviating the formation and / or accumulation of these solid impurities. The solid impurities may be, for example, sulfur-containing impurities, such as sulfur-containing compounds. In some cases, the solid impurities are part of a solid sulfur-containing impurity composition. The sulfur-containing impurity composition comprises solid impurities that may be sulfur-containing compounds.

[0026] In some embodiments, the present disclosure relates to the use of nitrile compounds in dissolving solid impurities (sulfur-containing impurity compositions) produced by the reaction of conventional hydrogen sulfide scavengers, such as triazine compounds and hydrogen sulfide. The inventors have found that the nitrile compounds described herein exhibit high solubility for solid impurities that may be formed in conventional oil and gas operations. In other words, solid impurities are easily dissolved (or remain dissolved without precipitation) in the nitrile compounds described herein (solutions containing the nitrile compounds described herein).

[0027] The present 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 sulfur-containing compounds and optionally trithiane, preferably a small amount.

[0028] In some aspects, the present disclosure provides a dissolver solution comprising a nitrile compound and a hydrogen sulfide scavenger. When these dissolver solutions are used (e.g., in oil and gas operations), the hydrogen sulfide scavenger preferentially reacts with hydrogen sulfide and produces solid impurities, and the nitrile compound advantageously dissolves the solid impurities (e.g., by re-dissolving precipitated solid impurities and / or by keeping the solid impurities dissolved in the solution without precipitation). In other aspects, the present disclosure also provides methods of using the dissolver solutions and / or nitrile compounds described herein, such as for reducing and / or removing hydrogen sulfide, for dissolving dithiazine, and / or for removing solid impurities.

[0029] In some cases, the present disclosure relates to a method for inhibiting the formation of polymeric sulfur-containing compounds, such as trithiane, in a sulfur-containing impurity composition comprising sulfur-containing compounds. The method adds 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 polymeric sulfur-containing compounds, such as trithiane.

[0030] In some respects, nitrile compounds can be used for (e.g., exist alone) dissolving solid impurities. Some nitrile compounds are known and available. However, it has been unexpectedly found that disclosed nitrile compounds are effective for purposes and methods as described herein. Conventional teachings have not yet indicated that disclosed nitrile compounds are used for these purposes.

[0031] Nitrile compounds

[0032] Many nitrile compounds are described herein, and the inventors have found that they advantageously dissolve solid impurities that may be insoluble in (e.g., poorly soluble in) conventional solvents. Therefore, the nitrile compounds can be used to dissolve (e.g., redissolve or remain dissolved) the solid impurities described herein. In addition, the nitrile compounds can be used in a dissolver solution comprising the nitrile compound and a hydrogen sulfide scavenger, which reacts (e.g., with hydrogen sulfide) to produce the solid impurities.

[0033] Nitrile compounds can be any organic compound comprising one or more cyano or nitrile functional groups. The inventor has found that the presence of these nitrile compounds can advantageously provide the solubility of the raising of various solid impurities. For example, nitrile compounds can preferentially dissolve (for example redissolve or keep dissolving) the solid impurities precipitated in the process of the desulfurization process of oil and gas operation. The existence and / or accumulation of solid sediment, for example on the inner surface of processing equipment, pipe, container, storage tank, transport tank or water treatment well, may cause the obstruction in machinery, then need to clean or replace. By dissolving solid impurities, nitrile compounds alleviate or eliminate the accumulation of solid impurities on the surface. In addition, the solubility of solid impurities in nitrile compounds allows to use nitrile compounds (for example comprising the solution of nitrile compounds) in the cleaning of machinery. The present disclosure contemplates using nitrile compounds to dissolve solid impurities in many such applications (some of which are mentioned above as non-limiting examples).

[0034] 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 atom chain. For example, in some embodiments, the nitrile compound is a trinitrile alkane, such as a trinitrile alkane having a chemical formula C x H 2x-1 (CN)3 organic compound, wherein x is 4 to 10. Exemplary trinitrile compounds include butane trinitrile (e.g., tricyanobutane), pentane trinitrile (e.g., tricyanopentane), hexane trinitrile (e.g., tricyanohexane), heptane trinitrile (e.g., tricyanoheptane), octane trinitrile (e.g., tricyanoctane), nonane trinitrile (e.g., tricyanononane) and decane trinitrile (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.

[0035] In terms of chemical structure, trinitrile compounds may have the structure

[0036]

[0037] wherein a, b and c are independently 0 to 4. In some embodiments, the sum of a, b and c is 3 to 10.

[0038] 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 atom chain. For example, in some embodiments, the nitrile compound is a dinitrile alkane, such as a compound having the chemical formula C x H 2x (CN)2, wherein x is 1 to 6. Exemplary dinitrile compounds include malononitrile (e.g., dicyanomethane), succinonitrile (e.g., dicyanoethane), glutaronitrile (e.g., dicyanopropane), adiponitrile (e.g., dicyanobutane), pentane dinitrile (e.g., dicyanopentane), and hexane dinitrile (e.g., dicyanohexane).

[0039] In some embodiments, the nitrile compound is a mononitrile compound, such as an organic compound having one cyano or nitrile functional group on a saturated or unsaturated carbon atom chain. For example, in some embodiments, the nitrile compound is a nitrile alkane, such as a nitrile having the chemical formula C x H 2x+1 (CN), wherein 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 capronitrile (e.g., cyanohexane).

[0040] In some embodiments, the nitrile compound comprises a mixture of the above-mentioned compounds. For example, a combination of one or more trinitriles, dinitriles and / or mononitriles can be used. It is envisioned that in some cases, the nitrile compound can be used without a hydrogen sulfide scavenger (e.g., a dissolver solution may only comprise the nitrile compound), for example, to dissolve solid impurities in various 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.

[0041] When incorporated into the dissolver solution, the amount of nitrile compound present in the dissolver solution is not particularly limited and can vary widely. In one embodiment, the dissolver solution comprises from 0.1% to 20% by volume of the nitrile compound, e.g., from 0.1% to 18.5% by volume, from 0.1% to 17% by volume, from 0.1% to 15.5% by volume, from 0.1% to 12% by volume, from 0.2% to 20% by volume, from 0.2% to 18.5% by volume, from 0.2% to 17% by volume, from 0.2 .... % to 18.5 volume %, 0.5 volume % to 17 volume %, 0.5 volume % to 15.5 volume %, 0.5 volume % to 12 volume %, 0.8 volume % to 20 volume %, 0.8 volume % to 18.5 volume %, 0.8 volume % to 17 volume %, 0.8 volume % to 15.5 volume %, or 0.8 volume % to 12 volume %.With regard to the lower limit, the dissolver solution can include the nitrile compound greater than 0.1 volume %, for example, greater than 0.2 volume %, greater than 0.5 volume % or greater than 0.8 volume %.With regard to the upper limit, the dissolver solution can include the nitrile compound less than 20 volume %, for example, less than 18.5 volume %, less than 17 volume %, less than 15.5 volume % or less than 12 volume %.

[0042] In some cases, the content of the nitrile compound present in the dissolver solution can be relatively high.In one embodiment, for example, the dissolver solution comprises the nitrile compound of 15 volume % to 85 volume %, for example 15 volume % to 80 volume %, 15 volume % to 75 volume %, 15 volume % to 70 volume %, 15 volume % to 65 volume %, 20 volume % to 85 volume %, 20 volume % to 80 volume %, 20 volume % to 75 volume %, 20 volume % to 70 volume %, 20 volume % to 65 volume %, 25 volume % to 85 volume %, 25 volume % to 80 volume %, 25 volume % to 75 volume %, 25 volume % to 70 volume %, 25 volume % to 65 volume %, 30 volume % to 85 volume %, 30 volume % to 80 volume %, 30 volume % to 75 volume %, 30 volume % to 70 volume %, or 30 volume % to 65 volume %. In terms of lower limits, the dissolver solution may comprise greater than 15% by volume of the nitrile compound, for example greater than 20% by volume, greater than 25% by volume or greater than 30% by volume. In terms of upper limits, the dissolver solution may comprise less than 85% by volume of the 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.

[0043] Hydrogen sulfide scavenger

[0044] The dissolver solutions described herein contain, in addition to the nitrile compound, a hydrogen sulfide scavenger. The hydrogen sulfide scavenger can vary widely and many hydrogen sulfide scavengers are known.

[0045] The hydrogen sulfide scavenger can be any organic or inorganic compound that selectively reacts with hydrogen sulfide (or other organic sulfide components) in a fluid stream or otherwise chelates and / or removes hydrogen sulfide (or other organic sulfide components) in a fluid stream. Preferably, the hydrogen sulfide scavenger converts the sulfide component into a more inert form by an irreversible reaction.

[0046] In some embodiments, the hydrogen sulfide scavenger may include an inorganic compound. For example, the hydrogen sulfide scavenger may include 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 include hydrogen peroxide, which may react to form free sulfur.

[0047] In some embodiments, the hydrogen sulfide scavenger may include an organic compound. For example, the hydrogen sulfide scavenger may include a nitrogen-containing compound, such as a nitrogen-containing heterocycle. In some embodiments, the hydrogen sulfide scavenger includes a triazine (e.g., a triazine derivative). In other words, the hydrogen sulfide scavenger may be a triazine compound. Exemplary triazine compounds include triazines (e.g., s-triazine), hexahydro-triazines (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.

[0048] In terms of chemical structure, hydrogen sulfide scavengers may have the structure:

[0049]

[0050] Wherein R1, R2 and R3 are independently hydrogen, C1-C5 alkyl, C2-C5 alkenyl or C1-C5 alcohol group.In some embodiments, for example, R1, R2 and R3 are each C1-C5 alcohol group, such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl and / or hydroxypentyl.

[0051] Commercially available hydrogen sulfide scavengers include PureMark products from Foremark, GasTreat products from Nalco, MEA Traizine products from Hexion, and Sulfix from Baker Hughes.

[0052] The amount of hydrogen sulfide scavenger present in the dissolver solution is not particularly limited and may vary widely. In one embodiment, the dissolver solution comprises 15% to 85% by volume of the hydrogen sulfide scavenger, e.g., 15% to 80% by volume, 15% to 75% by volume, 15% to 70% by volume, 15% to 65% by volume, 20% to 85% by volume, 20% to 80% by volume, 20% to 75% by volume, 20% to 70% by volume, 20% to 65% by volume, 25% to 85% by volume, 25% to 80% by volume, 25% to 75% by volume, 25% to 70% by volume, 25% to 65% by volume, 30% to 85% by volume, 30% to 80% by volume, 30% to 75% by volume, 30% to 70% by volume, or 30% to 65% by volume. In terms of lower limits, the dissolver solution may contain greater than 15% by volume of hydrogen sulfide scavenger, such as greater than 20% by volume, greater than 25% by volume, or greater than 30% by volume. In terms of upper limits, 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.

[0053] Additional components

[0054] The dissolver solution described herein may contain other (optional) components in addition to the nitrile compound and the hydrogen sulfide scavenger. These additional components may provide further functionality to the dissolver solution. For example, the additional components may stabilize the dissolver solution or may facilitate its use.

[0055] In some embodiments, nitrile compound and hydrogen sulfide scavenger are dispersed (e.g., dissolved) in a solvent. In some embodiments, nitrile compound is used in the absence of hydrogen sulfide scavenger, but is dispersed (e.g., dissolved) in a solvent. Without being subject to any mechanism or theory, the dissolver solution described herein may include 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 restriction 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 include a certain volume percentage of nitrile compound and hydrogen sulfide compound (and any additional components), and the rest is solvent.

[0056] In some embodiments, the dissolver solution further comprises additional components, such as an acid, a dispersant, a viscosity enhancer, a lubricant, a scale inhibitor, a friction reducer, a cross-linking agent, a surfactant, a pH adjuster, an iron control agent, a demulsifier, or a combination thereof. In some embodiments, the nitrile compound is used in the absence of a hydrogen sulfide scavenger, but is mixed with any of these additional components.

[0057] 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 sorbitan fatty acid ester ethoxylates (e.g., Tween 40), alkylphenol alcohol ethoxylates (e.g., NP-9, NP-4), nonionic polymer surfactants (e.g., CRODA Hypermer A70), cationic surfactants (ethoxylated tallow alkylmonium ethosulfate, Crodaquat TES) and sorbitan monooleate (e.g., SPAN 80).

[0058] Solid impurities

[0059] As mentioned 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 may cause clogging, blocking, damage and ultimately failure of various components in oil and gas operations. In various processes using hydrogen sulfide scavengers, such as oil and gas operations, various solid impurities may be formed, and it has been advantageously found that the nitrile compounds described herein (alone and / or as a component of a dissolver solution) dissolve the solid impurities.

[0060] 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-based compound with 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:

[0061]

[0062] Wherein R is hydrogen, C1-C5 alkyl, C2-C5 alkenyl or C1-C5 alcohol group.In some embodiments, for example, R is C1-C5 alcohol group, such as hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl and / or hydroxypentyl.

[0063] In some embodiments, the hydrogen sulfide scavenger is an azido compound having the structure previously discussed, the solid impurity has the above structure, and the R functional group is equivalent to the R1, R2 and / or R3 functional group of the azido compound. For example, the hydrogen sulfide scavenger may include hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine, and the solid impurity may include 5-hydroxyethyl-1,3,5-dithiazine.

[0064] In some cases, the solid impurities include amorphous dithiazine. For example, the solid impurities may include amorphous products and / or derivatives of dithiazine compounds produced by the reaction of hydrogen sulfide scavengers with hydrogen sulfide and / or other sulfide components. The chemical structures of amorphous dithiazine 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 Scavengers 50 IND.ENG.CHEM.RES.735 (2011), which is incorporated herein by reference.

[0065] In some embodiments, the solid impurities include inorganic sulfur compounds. In some cases, for example, the solid impurities include metal sulfides, such as iron sulfide (e.g., pyrite), lead sulfide (e.g., galena), zinc sulfide (e.g., sphalerite), silver sulfide (e.g., argentite), mercury sulfide (e.g., cinnabar), molybdenum sulfide (e.g., molybdenite), nickel sulfide (e.g., pentlandite), arsenic sulfide (e.g., realgar), antimony sulfide (e.g., stibnite), iron-copper sulfide (e.g., chalcopyrite), or a combination thereof. In some cases, the solid impurities include sulfates, such as calcium sulfate (e.g., gypsum, hemihydrate, anhydrous gypsum), strontium sulfate (e.g., celestite), lead sulfate (e.g., lead alum), barium sulfate (e.g., barite), or a combination thereof.

[0066] In some embodiments, the solid impurities comprise elemental sulfur.

[0067] Solid impurities, for example dithiazine compounds are usually insoluble in oil and gaseous fluids. Therefore, solid impurities may accumulate mechanically as solid precipitation from solution. But the inventor has found that nitrile compounds (and the dissolver solution comprising nitrile compounds) show high solubility to solid impurities. That is to say, nitrile compounds can redissolve the solid impurities of precipitation and / or make solid impurities remain as solute (for example by reducing or eliminating precipitation). The tendency that solid impurities (for example dithiazine compounds) are dissolved in the nitrile compounds can be quantified by dissolution rate, and it indicates the maximum amount of solid impurities (for example dithiazine compounds) dissolved in the nitrile compounds at a given temperature.

[0068] As mentioned above, the nitrile compounds mentioned above have an unexpected ability to dissolve solid impurities. In other words, the solubility of solid impurities (e.g., dithiazine compounds) in nitrile compounds is surprisingly high. For example, the solubility at 70°F may be 0.01kg / l to 20kg / l, such as 0.01kg / l to 18kg / l, 0.01kg / l to 16kg / l, 0.01kg / l to 14kg / l, 0.01kg / l to 12kg / l, 0.02kg / l to 20kg / l, 0.02kg / l to 18kg / l, 0.02kg / l to 16kg / l, 0.02kg / l to 14kg / l, 0.02kg / l to 12kg / l, 0.04kg / l to 20kg / l, 0.04kg / l to 18kg / l, 0.04kg / l to 16kg / l, 0.04kg / l to 14kg / l, 0.04kg / l to 12kg / l, 0.06kg / l to 20kg / l, 0.06kg / l to 18kg / l, 0.06kg / l to 16kg / l, 0.06kg / l to 14kg / l, 0.06kg / l to 12kg / l, 0.08kg / l to 20kg / l, 0.08kg / l to 18kg / l, 0.08kg / l to 16kg / l, 0.08kg / l to 14kg / l, or 0.08kg / l to 12kg / l. In terms of lower limits, the solubility of solid impurities (e.g., dithiazine compounds) in nitrile compounds at 70°F may be greater than 0.01 kg / l, e.g., 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., dithiazine compounds) in nitrile compounds at 70°F may be less than 20 kg / l, e.g., less than 18 kg / l, less than 16 kg / l, less than 14 kg / l, or less than 12 kg / l.

[0069] In some embodiments, the solubility of solid impurities (e.g., dithiazine compounds) in the nitrile compound at 125°F is from 0.5 kg / l to 50 kg / l, for example, from 0.5 kg / l to 45 kg / l, from 0.5 kg / l to 40 kg / l, from 0.5 kg / l to 35 kg / l, from 0.6 kg / l to 50 kg / l, from 0.6 kg / l to 45 kg / l, from 0.6 kg / l to 40 kg / l, from 0.6 kg / l to 35 kg / l, from 0.8 kg / l to 50 kg / l, from 0.8 kg / l to 45 kg / l, from 0.8 kg / l to 40 kg / l, from 0.8 kg / l to 35 kg / l, from 1 kg / l to 50 kg / l, from 1 kg / l to 45 kg / l, from 1 kg / l to 40 kg / l, or from 1 kg / l to 35 kg / l. In terms of lower limits, the solubility of solid impurities (e.g., dithiazine compounds) in nitrile compounds at 125°F may be greater than 0.5 kg / l, e.g., greater than 0.6 kg / l, greater than 0.8 kg / l, or greater than 1 kg / l. In terms of upper limits, the solubility of solid impurities (e.g., dithiazine compounds) in nitrile compounds at 125°F may be less than 50 kg / l, e.g., less than 45 kg / l, less than 40 kg / l, or less than 35 kg / l.

[0070] Sulfur-containing impurity composition

[0071] When the solid sulfur-containing compound in the sulfur-containing impurity composition is contacted with the nitrile (and optionally subjected to other treatments, such as temperature), a treated sulfur-containing impurity composition is formed.

[0072] The sulfur-containing impurity composition may include (monomer) sulfur-containing compounds, such as dithiazine. For example, the sulfur-containing impurity composition may include sulfur-containing compounds greater than 25% by weight based on the total weight of the sulfur-containing impurity composition, such as greater than 35% by weight, greater than 50% by weight, greater than 75% by weight, greater than 85% by weight, greater than 90% by weight, greater than 95% by weight or greater than 99% by weight. In terms of scope, the sulfur-containing impurity composition may include sulfur-containing compounds of 25% to 100% by weight, such as 50% to 100% by weight, 25% to 75% by weight, 35% to 65% by weight, 75% to 100% by weight, 85% to 99.5% by weight or 90% to 99% by weight. In terms of upper limit, the sulfur-containing impurity composition may include sulfur-containing compounds less than 100%, 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.

[0073] The treated sulfur-containing impurity composition may include a reduced amount of sulfur-containing compounds, such as monomeric dithiazine (reduced compared to the initial sulfur-containing impurity composition). For example, the treated sulfur-containing impurity composition may include less than 99.5% of 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 include 0% to 95% by weight of sulfur-containing compounds, such as 0% to 75% by weight, 0% to 50% by weight, 1% to 35% by weight, 5% to 25% by weight, or 10% to 20% by weight. In terms of lower limits, the sulfur-containing impurity composition can include greater than 0 wt % of sulfur-containing compounds, eg, greater than 1 wt %, greater than 5 wt %, greater than 10 wt %, greater than 25 wt %, or greater than 50 wt %.

[0074] In some cases, the reduced amount of monomeric sulfur-containing compounds is at least 10% less than the initial amount of sulfur-containing compounds present in the untreated sulfur-containing impurity composition, e.g., 15% less, 25% less, 35% less, 50% less, at least 75% less, or at least 90% less.

[0075] In some embodiments, monomeric sulfur-containing impurities may polymerize to form polymeric sulfur-containing impurities. In some cases, this polymerization may be usefully delayed or prevented by treating with nitrile compounds disclosed herein. As a result of treatment, the formation of (polymerized) thiazine-containing polymers / compounds, such as trithiane impurities, by monomeric dithiazine is also delayed or eliminated. Therefore, the treated sulfur-containing impurity composition comprises only a small amount of polymeric sulfur-containing compounds, such as thiazine-containing polymers / compounds.

[0076] For example, the treated sulfur-containing impurity composition may contain less than 100% polymeric sulfur-containing compounds, such as trithiane, such as less than 95%, less than 90% by weight, less than 80% by weight, less than 75% by weight, less than 65% by weight, less than 60% by weight, less than 50% by weight, less than 40% by weight, less than 30% by weight, less than 25% by weight, or less than 10% by weight. In terms of ranges, the treated sulfur-containing impurity composition may contain from 1 ppb to 90% by weight of polymeric sulfur-containing compounds, such as from 1 ppm to 90% by weight, from 1% to 90% by weight, from 10% to 80% by weight, from 20% to 75% by weight, from 35% to 75% by weight, from 40% to 70% by weight, or from 45% to 70% by weight. In terms of upper limits, the sulfur-containing impurity composition may contain greater than 1 ppb of polymerized sulfur-containing compounds, e.g., greater than 10 ppm, greater than 1 wt%, greater than 10 wt%, greater than 15 wt%, greater than 25 wt%, greater than 35 wt%, greater than 45 wt%, greater than 50 wt%, greater than 60 wt%, greater than 65 wt%, or greater than 75 wt%.

[0077] Dissolved solid impurities

[0078] Considering the relatively high solubility of solid impurities (or multiple impurities) in nitrile compounds, the nitrile compounds described herein (and the dissolver solutions containing nitrile compounds) can be beneficially used to dissolve (e.g., redissolve or maintain dissolved) solid impurities. Therefore, several embodiments of the present disclosure provide methods utilizing dissolver solutions and / or nitrile compounds.

[0079] In some embodiments, nitrile compounds and / or dissolver solutions are used to reduce or remove sulfide impurities, such as hydrogen sulfide or organic sulfide compounds. In these embodiments, dissolver solutions as described herein are added to the system containing sulfide impurities. The system containing sulfide impurities can be a component or machinery of oil and gas operations, such as a component of a desulfurization process. The mechanism of adding dissolver solutions to the system is not particularly limited. In some embodiments, dissolver solutions are added to the system by direct injection. For example, dissolver solutions can be sprayed (for example, with an atomizing sleeve) or otherwise injected into the fluid stream (for example, oil, gas or fluid mixture) of the system containing sulfide impurities. In some embodiments, by contactors, such as contactor towers, dissolver solutions are added to the system. For example, the fluid stream (for example, oil, gas or fluid mixture) of the system containing sulfide impurities can be bubbled or otherwise fed through the contactor tower equipped with dissolver solutions. In these embodiments, hydrogen sulfide scavenger preferentially reacts with sulfide impurities, and the nitrile compound dissolves (for example, redissolves and / or keeps dissolved) the product of the reaction.

[0080] The present disclosure also relates to treating a sulfur-containing composition that may contain solid impurities (as part of the sulfur-containing impurity composition), which comprises 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 a composition as described herein.

[0081] In some embodiments, nitrile compounds and / or dissolver solutions are used to dissolve solid impurities, such as dithiazine compounds. In these embodiments, dissolver solutions as described herein are added to impure systems. The system containing (sulfide) impurities can be a component or machinery of oil and gas operations, such as a component of a desulfurization process. Impurities, such as dithiazine, may be the product of desulfurization processes in some cases. In order to remove solids, such as dithiazine, dissolver solutions are introduced into impure systems. The mechanism of adding dissolver solutions to the system is not particularly limited. In this embodiment, dissolver solutions can be used for cleaning or removing precipitated dithiazine compounds while continuously removing sulfide impurities.

[0082] In some embodiments, nitrile compounds and / or dissolver solutions are used to remove solid impurities, such as dithiazine compounds, from the surface. In these embodiments, nitrile compounds dissolve solid impurities. The surface to be cleaned is not particularly limited, and can be, for example, a component or machinery of oil and gas operations, such as a component of a desulfurization process. In some cases, the impure system can be an impurity, such as a mechanical component on which dithiazine compounds have been precipitated and / or accumulated. In some embodiments, for example, it can be a component of oil and / or gas operations, mining operations, paper and pulp processing, hydroelectric power plants, coal-fired power plants, or municipal water supply facilities. Dithiazine may be the product of desulfurization process in some cases. In order to remove solid dithiazine, nitrile compounds are introduced to the surface. The mechanism of adding dissolver solutions to the system is not particularly limited. In this embodiment, nitrile compounds can be used alone to clean or remove precipitated dithiazine compounds.

[0083] As discussed above, solid impurities are soluble in nitrile compounds at ambient temperature. Therefore, the above method may be included in the use of nitrile compounds and / or dissolver solutions at ambient temperature. In some embodiments, at 50°F to 90°F, for example, 50°F to 85°F, 50°F to 80°F, 50°F to 75°F, 55°F to 90°F, 55°F to 85°F, 55°F to 80°F, 55°F to 75°F, 60°F to 90°F, 60°F to 85°F, 60°F to 80°F, 60°F to 75°F, 65°F to 90°F, 65°F to 85°F, 65°F to 80°F, or 65°F to 75°F, nitrile compounds and / or dissolver solutions are utilized. With regard to lower limits, nitrile compounds and / or dissolver solutions may be utilized at a temperature greater than 50°F, for example, greater than 55°F, greater than 60°F, or greater than 65°F. In terms of upper limits, the nitrile compound and / or the dissolver solution may be utilized at a temperature of less than 90°F, eg, less than 85°F, less than 80°F, or less than 75°F.

[0084] The solubility of solid impurities in nitrile compounds increases with temperature.Therefore, aforesaid method can further comprise heating nitrile compounds and / or dissolver solution (and optionally heating solid impurities or containing solid impurities) to the temperature raised.In some embodiments, nitrile compounds and / or dissolver solution are heated to 90°F to 400°F, for example 90°F to 390°F, 90°F to 380°F, 90°F to 375°F, 100°F to 400°F, 100°F to 390°F, 100°F to 380°F, 100°F to 375°F, 110°F to 400°F, 110°F to 390°F, 110°F to 380°F, 110°F to 375°F, 115°F to 400°F, 115°F to 390°F, 115°F to 380°F, or 115°F to 375°F. In terms of lower limits, the nitrile compound and / or the dissolver solution may be heated to a temperature greater than 90° F., e.g., greater than 100° F., greater than 110° F., or greater than 115° F. In terms of upper limits, the nitrile compound and / or the dissolver solution may be heated to a temperature less than 400° F., e.g., less than 390° F., less than 380° F., or less than 375° F.

[0085] The dissolving of solid impurities in nitrile compounds may require that solid impurities are exposed to nitrile compounds for a long time. Therefore, the above method may further comprise the time allowing solid impurities (such as dithiazine compounds) to dissolve and prolong. In some embodiments, solid impurities (such as dithiazine compounds) are exposed to nitrile compounds for 0.5 hour to 48 hours, such as 0.5 hour to 120 hours, 0.5 hour to 96 hours, 0.5 hour to 72 hours, 0.5 hour 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, 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. For lower limits, solid impurities can be exposed to nitrile compounds for at least 0.5 hours, for example at least 1 hour, at least 1.5 hours or at least 2 hours. For upper limits, solid impurities can be exposed to nitrile compounds for less than 48 hours, for example less than 120 hours, less than 96 hours, less than 72 hours or less than 48 hours.

[0086] Trithiane inhibition

[0087] In some cases, dissolution of dithiazines can be used to retard the formation of impurities formed from dithiazines (dithiazine monomers). Some examples of impurities formed from dithiazine monomers are thianes, such as trithiane.

[0088] In some embodiments, the present disclosure relates to a method for inhibiting the formation of (polymerized) sulfur-containing compounds, such as (polymerized) thiazine-containing polymers / compounds, such as trithiane, in a sulfur-containing impurity composition comprising a sulfur-containing compound, such as dithiazine. The polymerized sulfur-containing compound can be a polymer containing (monomer) dithiazine or formed by (monomer) dithiazine. The method comprises the step of adding a nitrile compound, such as hexane trinitrile (optionally in a dissolver solution) to the sulfur-containing impurity composition. Thus, the nitrile compound dissolves at least some dithiazine in the sulfur-containing impurity composition to form a treated sulfur-containing impurity composition. In some cases, the treated sulfur-containing impurity composition comprises a reduced amount of (monomer) sulfur-containing compounds (dithiazine), or in some cases does not contain monomeric sulfur-containing compounds. Therefore, the formation of (polymerized) thiazine-containing polymers / compounds, such as trithiane impurities, by monomeric dithiazine is delayed or eliminated. In other words, trithiane is almost or completely not formed because there is almost or completely no monomeric dithiazine for forming it. The amount of trithiane (or other (polymerized) thiazine-containing polymers / compounds) in the treated sulfur-containing impurity composition can be as discussed herein.

[0089] In some cases, the treated sulfur-containing impurity composition comprises less than 100 wt % (polymerized) thiazine-containing polymer / compound, such as trithiane (see discussion above regarding the composition of the treated sulfur-containing impurity composition).

[0090] In some embodiments, any or some steps or components disclosed herein may be considered optional. In some cases, any or some of the aforementioned items in this specification may be explicitly excluded, for example, by the wording of the claims. For example, the wording of the claims may be modified to indicate that the composition does not include or exclude castor oil.

[0091] As used herein, "greater than" and "less than" limits may also include the numbers associated therewith. In other words, "greater than" and "less than" may be interpreted as "greater than or equal to" and "less than or equal to". It is contemplated that the wording may be subsequently modified in a claim to include "or equal to". For example, "greater than 4.0" may be interpreted and subsequently modified in a claim to "greater than or equal to 4.0". Example

[0092] The present disclosure will be further understood with reference to the following non-limiting examples.

[0093] Example 1

[0094] The test was run to evaluate the solubility of nitrile compounds in hydrogen sulfide scavengers and thereby determine the composition of the dissolver solution. A 60 volume % aqueous solution of hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine was used as the hydrogen sulfide scavenger. Hexanetrinitrile was used as the nitrile compound.

[0095] Prepare five samples, each 5 milliliters, by adding nitrile compound in the hydrogen sulfide scavenger.Add different amounts of nitrile compound to prepare the sample that comprises 1 volume %, 2 volume %, 3 volume %, 4 volume % and 5 volume % nitrile compound respectively, and surplus is the hydrogen sulfide scavenger.Shake each sample until visually even and make its sedimentation and separation.Shake sample again after initial separation to guarantee maximum dissolving, and then evaluate separation.

[0096] For each sample, shake and produce emulsion, it is advantageously stable up to 1 hour before observing separation.Therefore, all samples are highly stable.Especially, the sample comprising 1 volume % and 2 volume % nitrile compounds does not separate fully at any point; On the contrary, the small droplet of nitrile compounds only coalesces on the surface.Therefore, find that the dissolver solution comprising about 1-2 volume % is particularly stable and effective.Therefore, some nitrile solutions / compositions can be lower than 100 volume %, for example, be less than 75 volume %, be less than 50 volume %, be less than 35 volume %, be less than 25 volume %, be less than 15 volume %, be less than 10 volume %, be less than 5 volume % or be less than 3 volume % concentration and be effective.

[0097] Example 2

[0098] The test was run to evaluate the solubility of solid impurities in nitrile compounds. Hexane trinitrile 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 volume % 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.

[0099] In the first test, the solubility of the laboratory sample in the nitrile compound was evaluated. The sample was prepared by mixing the solid dithiazine from the laboratory sample with the nitrile compound. The sample was heated to 70°F and 125°F for 24 hours. After 24 hours, the 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.

[0100] Table 1: Laboratory sample tests

[0101] Example 1 Example 2 Temperature(℉) 70 125 Contact time (hours) 24 24 Nitrile compounds (g) 25.03 25.01 Initial solid impurities (g) 5.13 5.16 Final solid impurities (g) 4.84 4.24 Dissolved amount (g) 0.29 0.92 Calculate solubility (kg / l) 0.012 0.038

[0102] As shown by the data in Table 1, nitrile compounds are surprisingly effective in dissolving laboratory samples. In particular, at 125°F, the solubility is calculated to be -0.04 kg / l.

[0103] In the second test, the solubility of field samples in nitrile compounds was evaluated. The samples were prepared by mixing solid dithiazine from field samples with nitrile compounds. The samples were heated to 70°F and 125°F for either 2 hours or 24 hours. After this time, the 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 2.

[0104] Table 2: Field sample test

[0105] Example 3 Example 4 Example 5 Example 6 Temperature(℉) 70 70 125 125 Contact time (hours) 2 24 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 Dissolved amount (g) 1.040 4.891 12.65 44.63 Calculate solubility (kg / l) 0.107 0.506 >1.30 3.92

[0106] As shown in the data of Table 2, nitrile compounds are surprisingly effective in dissolving field samples at 70°F. In addition, Examples 3 and 4 show that after 2 hours at a lower temperature of 70°F, the solid impurities have been significantly dissolved, but not completely dissolved. Interestingly, further exposure of the solid impurities to the nitrile compounds, such as exposure for 24 hours, showed a higher dissolution rate than at 2 hours. This result shows that the use of extended contact time can further improve the dissolution effect.

[0107] As also shown in Table 2, nitrile compounds are surprisingly effective at dissolving field samples at 125°F. Within the first two hours, the solid impurities in Example 5 were completely dissolved. Therefore, the actual solubility of the solid impurities is greater than the calculated solubility because saturation has not been reached (as shown by the ">" in Table 2). However, in Example 6, the solid impurities were not completely dissolved (i.e., saturation was reached), so the solubility can be fully calculated. Examples 5-6 demonstrate the unexpected effectiveness of nitrile compounds in dissolving solid dithiazine impurities.

[0108] In a comparative test, alternative solvents were tested to evaluate the relative solubility of field samples. The samples were prepared by mixing solid dithiazine from field samples with 20 ml of various solvents. The samples were heated to 70°F for either 2 hours or 24 hours. After this time, the 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. Hexane trinitrile (Samples 3 and 4) was included for comparison.

[0109] Table 3: Comparative field sample test

[0110]

[0111]

[0112] As shown in the data of Table 3, nitrile compounds showed suitable on-site sample solubility after 2 hours.But, after 24 hours, nitrile compounds showed the highest solubility 0.506kg / l, and it is much higher than the 0.4kg / l that methyl alcohol shows, and methyl alcohol is the best performance in the contrast solvent.In addition, nitrile compounds has the flash-point that is obviously lower than methyl alcohol.Therefore when caring about inflammability (refinery), nitrile compounds is the advantageous product that is used to dissolve solids.

[0113] Example 3

[0114] The test was run to evaluate the ability of the dissolver solution to react with sulfide impurities and dissolve the product. By mixing 20 ml of an aqueous solution of 60% by volume hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine with 3.6 ml of a nitrile compound comprising hexane trinitrile, a dissolver solution (Example 8) was prepared. The resulting dissolver solution comprises 15% by volume of the nitrile compound. The comparative example uses 20 ml of an aqueous solution of 60% by volume hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine without a nitrile compound (Comparative Example H).

[0115] In each test, the solution was placed in a test vessel to which a hydrogen sulfide (H2S) gas supply was connected. The gas valve was opened at a set flow rate and hydrogen sulfide was pumped through the test solution. The treatment continued until hydrogen sulfide was no longer consumed - as determined by the detection of hydrogen sulfide 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 obvious separation between the hydrogen sulfide scavenger and the nitrile compound was observed during or after the test. The results of the test are reported in Table 4.

[0116] Table 4: Scavenger test

[0117]

[0118]

[0119] As shown in the data of Table 4, the breakthrough time of hydrogen sulfide occurred at similar times for both tests. This indicates that the nitrile compound does not interfere with the reaction or effectiveness of the hydrogen sulfide scavenger.

[0120] After the above tests were completed, each sample was poured into a vial and allowed to stand at 70°F for 24 hours. After 24 hours, Comparative Example A had become completely opaque, and solids were visible in the thick slurry. After 24 hours, Example 7 only became slightly turbid, and no solids were visible. This indicates that the presence of the nitrile compound minimizes and / or delays the formation of solid impurities.

[0121] Implementation

[0122] As used hereinafter, any reference to a series of embodiments is understood to be a reference to each of those embodiments individually (eg "embodiments 1-4" is understood to be "embodiment 1, 2, 3 or 4").

[0123] Embodiment 1 is a method for removing solid impurities, such as sulfur-containing compounds optionally present as part of a sulfur-containing impurity composition, from a surface, 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 wt % of sulfur-containing compounds based on the total weight of the treated sulfur-containing impurity composition, and optionally wherein the treated dithiazine composition further comprises from 1 ppm to 90 wt % of a polymeric sulfur-containing compound.

[0124] Embodiment 2 is the method of any of the preceding embodiments, wherein the nitrile compound has the chemical formula C x H 2x-1 (CN)3, wherein x is 4 to 10.

[0125] Embodiment 3 is the method of any of the preceding embodiments, wherein the nitrile compound comprises hexanetrinitrile.

[0126] Embodiment 4 is the method of any of the preceding embodiments, wherein the nitrile compound has the chemical formula C x H 2x (CN)2, wherein x is 1 to 6.

[0127] Embodiment 5 is the method of any of the preceding embodiments, wherein the nitrile compound has the chemical formula C x H 2x+ 1CN, where x is 1 to 6.

[0128] Embodiment 6 is the method of any of the preceding embodiments, wherein the nitrile compound has the chemical structure:

[0129]

[0130] wherein a, b and c are independently 0 to 4.

[0131] Embodiment 7 is the method of any of the preceding embodiments, wherein the solid impurities comprise dithiazine compounds.

[0132] Embodiment 8 is the method of any of the preceding embodiments, wherein the nitrile compound exhibits a dithiazine solubility at 70°F of 0.01 kg / l to 20 kg / l.

[0133] Embodiment 9 is the method of any of the preceding embodiments, wherein the nitrile compound exhibits a dithiazine solubility at 125°F of 0.5 kg / l to 50 kg / l.

[0134] Embodiment 10 is a dissolver solution comprising: a nitrile compound; and a hydrogen sulfide scavenger.

[0135] Embodiment 11 is the dissolver solution of any of the preceding embodiments, wherein the dissolver solution comprises the nitrile compound in an amount of 0.1 vol% to 85 vol%.

[0136] Embodiment 12 is the dissolver solution of any of the preceding embodiments, wherein the nitrile compound has the formula C x H 2x-1 (CN)3, wherein x is 4 to 10.

[0137] Embodiment 13 is the dissolver solution of any of the preceding embodiments, wherein the nitrile compound has the chemical structure:

[0138]

[0139] wherein a, b and c are independently 0 to 4.

[0140] Embodiment 14 is the dissolver solution of any of the preceding embodiments, wherein the nitrile compound comprises hexanetrinitrile.

[0141] Embodiment 15 is the dissolver solution of any of the preceding embodiments, wherein the hydrogen sulfide scavenger comprises a triazine compound.

[0142] Embodiment 16 is the dissolver solution of any of the preceding embodiments, wherein the hydrogen sulfide scavenger comprises hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine.

[0143] Embodiment 17 is a method of dissolving dithiazine, the method comprising adding the dissolver solution of any of the preceding embodiments to a system containing dithiazine.

[0144] Embodiment 18 is a method for treating a solid sulfur-containing impurity composition comprising sulfur-containing compounds, the method comprising contacting the sulfur-containing compounds in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition comprising less than 99.5 weight percent of the sulfur-containing compounds.

[0145] Embodiment 19 is the method of embodiment 18, wherein the treated sulfur-containing impurity composition comprises from 1 ppm to 90 wt% trithiane.

[0146] Embodiment 20 is a method for inhibiting the formation of polymerized 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 weight percent polymerized sulfur-containing compounds.

[0147] Embodiment 21 is the method of embodiment 20, wherein the reduced amount of monomeric sulfur-containing compounds is at least 10% less than the initial amount of sulfur-containing compounds present in the sulfur-containing impurity composition.

[0148] Embodiment 22 is the method of embodiment 20 or 21, wherein the polymeric sulfur-containing compound comprises trithiane.

Claims

1. A method for removing a solid sulfur-containing impurity composition containing dithiazine from a surface, the method comprising dissolving dithiazine in the sulfur-containing impurity composition with a nitrile compound to form a treated sulfur-containing impurity composition comprising less than 99.5 wt % of dithiazine based on the total weight of the treated sulfur-containing impurity composition, Wherein the nitrile compound has the chemical formula C x H 2x-1 (CN)3, wherein x is 4 to 10.

2. The method according to claim 1, wherein the treated sulfur-containing impurity composition further comprises 1 ppm to 90 wt% of trithiane.

3. The method according to claim 1, wherein the nitrile compound exhibits a dithiazine solubility of 0.01 kg / l to 20 kg / l at 70°F or 0.5 kg / l to 50 kg / l at 125°F.

4. The method according to claim 1, wherein the nitrile compound comprises hexanetrinitrile.

5. A dissolver solution comprising: Nitrile compounds; and Hydrogen sulfide scavengers, Wherein the nitrile compound has the chemical formula C x H 2x-1 (CN)3, wherein x is 4 to 10.

6. The dissolver solution according to claim 5, wherein the dissolver solution comprises the nitrile compound in an amount of 0.1% to 85% by volume.

7. The dissolver solution of claim 5, wherein the nitrile compound comprises hexanetrinitrile.

8. The dissolver solution of claim 5, wherein the hydrogen sulfide scavenger comprises a triazine compound.

9. The dissolver solution of claim 8, wherein the hydrogen sulfide scavenger comprises hexahydro-1,3,5-tris(hydroxyethyl)-s-triazine.

10. A method for dissolving dithiazide, the method comprising: The dissolver solution of claim 5 is added to the system containing the dithiazine.

11. A method for treating a solid sulfur-containing impurity composition comprising dithiazine, the method comprising contacting the dithiazine 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 dithiazine, wherein the nitrile compound has the chemical formula C x H 2x-1 (CN)3, wherein x is 4 to 10.

12. The method according to claim 11, wherein the treated sulfur-containing impurity composition comprises from 1 ppm to 90 wt% trithiane.

13. A method of inhibiting the formation of polymeric sulfur-containing compounds in a sulfur-containing impurity composition containing dithiazine, 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 nitrile compound has the chemical formula C x H 2x-1 (CN)3, wherein x is 4 to 10; wherein the treated sulfur-containing impurity composition comprises less than 90% by weight of polymerized sulfur-containing compounds; and wherein the monomeric sulfur-containing compound is dithiazine and the polymeric sulfur-containing compound is trithiane.

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

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