GB2616938A

GB2616938A - Corrosion inhibitor

Info

Publication number: GB2616938A
Application number: GB2219537.4A
Authority: GB
Inventors: Ruth Shore Emma; Robert Giles Matthew; James Francis Trenholme William; Adam Telford Matthew
Original assignee: Innospec Ltd
Current assignee: Innospec Ltd
Priority date: 2022-01-04
Filing date: 2022-12-22
Publication date: 2023-09-27
Also published as: WO2023131780A1; GB202219537D0; GB202200031D0

Abstract

The use of a compound as a corrosion inhibitor for metallic equipment, wherein the compound comprises a salt of an optionally substituted polycarboxylic acid or its anhydride, and/or the reaction product of the polycarboxylic acid or anhydride with an alcohol and/or amine, or the salt of the reaction product. A composition is defined comprising the compound and a further corrosion inhibitor additive. Also defines a method in which at least a portion of the metallic equipment is contacted by the compound, and the use of the compound and method whereby the salt is an alkali or amine. The optionally substituted polycarboxylic acid or anhydride may be a succinic acid or anhydride thereof. The substituent may be an alkyl or alkenyl group with 2-30 carbon atoms, or an alkaryl or aralkyl group. The amine salt may be tertiary, and the compound may comprise a di alkali metal salt or mono amine salt of a hydrocarbyl substituted dicarboxylic acid or anhydride thereof. The alcohol may comprise polyalkylene glycol, and the amine may be primary or secondary. The metallic equipment may be metallic oilfield equipment, pipelines, or temperature control jackets, and the surface may be in contact with corrosive or aqueous fluid.

Description

Corrosion inhibitor

Field of the Invention

The present invention relates to the use of particular compounds as corrosion inhibitors and methods related thereto. In particular, the invention relates to the use of said compounds as corrosion inhibitors for metallic equipment, such as metallic oilfield equipment, pipelines and temperature control jackets and other industrial equipment.

Background

Corrosion is a significant problem in industrial and domestic settings. The process of corrosion may involve the conversion of a metal into an oxide, hydroxide, carbonate or sulfide and it may affect any metallic surface of an industrial or domestic equipment or appliance. Corrosion may cause pitting, crevices or stress cracks within the metallic surface. In industry, corrosion is one of the major causes of plant and equipment damage and incurs high costs for the operators. Examples of industries in which corrosion is an issue include: the oil and gas industry especially in pipelines and metallic oilfield equipment desalination plants, power plants, cooling towers, heating systems such as boilers and refinery re-boilers, cooling and refrigerant systems, wastewater treatment plants, heat exchangers, and chemical manufacturing plants especially refineries and petrochemical plants Many species may be responsible for corrosion of a metal. Corrosion may especially be caused by acidic species like sulfides, basic species, oxygen and water present in the air or dissolved within a fluid in contact with the metallic surface.

For example, the equipment used in oilfields is typically exposed to various substances during the course of its lifetime. The equipment is in contact with air containing oxygen and moisture (that may be slightly acidic) and so the equipment can experience corrosion. Aqueous solutions, especially highly saline solutions known as brines, may be naturally present in the extracted oil and gas or may be intentionally injected to aid with oil recovery. The produced crude oil may contain corrosive species such as naphthenic acids or oil solubilised metallic species, but commonly it is the aqueous fluid that is produced in conjunction with the crude oil (or gas) that comprises a corrosive species (such as acidic compounds or dissolved oxygen). Acids such as carbon dioxide On the form of carbonic acid) and hydrogen sulfide may be naturally present within the subterranean formation or fluids contained therein, and/or acids such as hydrochloric acid, sulfuric acid and synthetic acids (such as urea-hydrochloric acid and urea-methanesulfonic acid adducts) may have been introduced through their use in a stimulation treatment such as matrix acidizing, acid fracturing or acid washing. These substances are corrosive to metallic oilfield equipment (such as well casings, drilling equipment, mud handling equipment, pipelines and storage tanks for treatment chemicals or the extracted fluids), especially at the elevated temperatures typically present therein. Corrosion will eventually lead to equipment failure and the uncontrolled release of oil or gas into the environment. Oilfield equipment must therefore be continuously monitored for corrosion, leading to high maintenance times and costs.

A number of corrosion inhibitors for use in oilfield equipment are known, such as imidazoline, chromium compounds, nitrites, nitrates, organic phosphates, inorganic phosphates, polyphosphates, phosphites, thiadiazoles, mercaptans, molybdates, azole, sulfonate, silicates, alkoxylated fatty amine, sulfonated fatty acids, pyridine and other heterocyclic nitrogen compounds, and quaternary ammonium compound corrosion inhibitors. However, there remains a need for alternative corrosion inhibitors, especially water soluble corrosion inhibitors that have a degree of biodegradability and that have a lower aquatic toxicity than imidazolines.

Summary

According to a first aspect of the present invention there is provided the use of a compound as a corrosion inhibitor for metallic equipment, wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

According to a second aspect of the present invention there is provided a method of preventing or reducing corrosion of metallic equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic equipment), wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

According to a third aspect of the present invention, there is provided a composition for inhibiting the corrosion of metallic equipment, the composition comprising: (a) a compound comprising (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a fourth aspect of the present invention, there is provided the use of a compound as a corrosion inhibitor, wherein the compound comprises (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.

According to a fifth aspect of the present invention, there is provided a method of preventing or reducing corrosion of a metallic surface, the method comprising contacting at least a portion of the metallic surface with a compound comprising (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.

According to a sixth aspect of the present invention, there is provided a composition for inhibiting the corrosion of a metallic surface, the composition comprising: (a) (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

Detailed Description

Unless otherwise stated, the following terms used in the specification and claims have the meanings set out below.

As used herein, the term "hydrocarbyl" substituent or group is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include: (i) hydrocarbon groups, that is, aliphatic (which may be saturated or unsaturated, linear or branched, e.g. alkyl or alkenyl or alkynyl), alicyclic (e.g. cycloalkyl, cycloalkenyl), and aromatic substituents, combinations thereof (e.g. alicyclic-and aromatic-substituted aliphatic substituents, such as aralkyl, aliphatic-and aromatic-substituted alicyclic substituents, and aliphatic-and alicyclic-substituted aromatic substituents such as alkaryl), as well as cyclic substituents wherein the ring is completed through another portion of the molecule (e.g. two substituents together form a ring); (ii) substituted hydrocarbon groups, that is, substituents containing non-hydrocarbon groups (e.g. halo (especially chloro and fluoro), hydroxy, alkoxy, keto, acyl, cyano, mercapto, alkylmercapto, amino, alkylamino, nitro, nitroso, and sulfoxy); (iii) hetero substituents, that is, substituents which, while having a predominantly hydrocarbon character, in the context of this invention, contain other than carbon in a ring or chain otherwise composed of carbon atoms. Heteroatoms include sulfur, oxygen, nitrogen, and encompass substituents as pyridyl, furyl, thienyl and imidazolyl. In general, no more than two, preferably no more than one, non-hydrocarbon substituent will be present for every ten carbon atoms in the hydrocarbyl group; typically, there will be no non-hydrocarbon substituents in the hydrocarbyl group.

By "optionally substituted" groups we mean that the particular groups are substituted or unsubstituted. Suitable substituents may include hydroxyl, oxo, alkoxy (such as Ci to C4 alkoxy), amino, halo (especially fluoro and chloro), trifluoromethyl, trifluoromethoxy, cyano, alkyl (such as Ci to Ca alkyl), alkenyl (such as C2 to C6 alkenyl), alkynyl (such as C2 to C5 alkynyl) and aryl (such as phenyl) groups.

The terms "alkyl", "alkenyl" and "alkynyl" include both straight and branched chain alkyl, alkenyl and alkynyl groups respectively.

The term "aryl" as used herein relates to an organic radical derived from an aromatic hydrocarbon by removal of one hydrogen, and includes any monocyclic, bicyclic or polycyclic carbon ring of up to 7 members in each ring, wherein at least one ring is aromatic.

The term "aralkyl" as used herein relates to alkyl radicals substituted with an aryl group, wherein the aryl group is an organic radical derived from an aromatic hydrocarbon by removal of one hydrogen, and includes any monocyclic, bicyclic or polycyclic carbon ring of up to 7 members in each ring, wherein at least one ring is aromatic. An example of an aralkyl group is a benzyl group. The term "alkaryl" as used herein refers to aryl radicals substituted with an alkyl group.

By a salt of an anhydride compound we mean to refer to a salt that is formed following hydrolysis of the anhydride group(s).

By "corrosion" we mean the deterioration of a material as a result of chemical interactions between the material and the surrounding environment, which may be caused by exposure of the material to corrosive substances.

By "inhibiting", "preventing" or "reducing" corrosion of equipment we mean inhibiting, preventing or reducing corrosion of at least a portion of said equipment (such as at least a portion of a surface of said equipment). In some embodiments, corrosion may be inhibited, prevented or reduced in the entirety of said equipment.

By "industrial equipment" we mean equipment that is used in an industrial setting and scale, for example that is used in large scale extraction, manufacturing, treatment, storage or transportation. Examples of industrial equipment will be well known to persons skilled in the art and include pipelines, oilfield equipment, desalination plants, mining equipment, power plants, cooling towers, heating systems (such as boilers and refinery re-boilers), cooling and refrigerant systems, temperature control jackets, wastewater treatment plants, electronic equipment or chemical manufacturing plants (such as refineries and petrochemical plants).

By "domestic equipment" we mean equipment that is used in a non-industrial setting and scale. An example of domestic equipment is a heating system, such as a domestic boiler.

By "oilfield equipment" we mean equipment that is used in oil and gas fields. Examples of oilfield equipment will be well known to persons skilled in the art, and includes any equipment that comes into contact with a corrosive fluid in the oil and gas industry. Typical oilfield equipment includes well casings, drilling equipment, mud handling equipment, pipelines and storage tanks for treatment chemicals or extracted fluids. The oil and gas fields may be on-shore or off-shore.

The equipment (such as the oilfield equipment) is metallic, by which we mean that it comprises a metal. Suitable metals include iron, zinc, aluminium, copper and/or steel.

As used in the specification and the appended claims, the singular forms "a", "an," and "the" include both singular and plural referents unless the context clearly dictates otherwise.

Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of other components. The term "consisting essentially of or "consists essentially of' means including the components specified but excluding other components except for components added for a purpose other than achieving the technical effect of the invention. The term "consisting of" or "consists of" means including the components specified but excluding other components.

Whenever appropriate, depending upon the context, the use of the term "comprises" or "comprising" may also be taken to include the meaning "consists essentially of' or "consisting essentially of, and also may also be taken to include the meaning "consists of" or "consisting of'.

As used herein, unless otherwise expressly specified, all numbers such as those expressing values, ranges, amounts of percentages may be read as if prefaced by the word "about", even if the term does not expressly appear.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to Scan include 1,2, 3,4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

The optional features set out herein may be used either individually or in combination with each other where appropriate and particularly in the combinations as set out in the accompanying claims. The optional features for each exemplary embodiment of the invention, as set out herein are also applicable to any other aspects or exemplary embodiments of the invention, where appropriate. In other words, the skilled person reading this specification should consider the optional features for each aspect or embodiment of the invention as interchangeable and combinable between different aspects of the invention.

As used herein, the term "and/or," when used in a list of two or more items, means that any one of the listed items can be employed by itself or any combination of two or more of the listed items can be employed. For example, if a list is described as comprising group A, B, and/or C, the list can comprise A alone; B alone; C alone; A and B in combination; A and C in combination, B and C in combination; or A, B, and C in combination.

According to a first aspect of the present invention there may be provided the use of a compound as a corrosion inhibitor for metallic equipment, wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof According to a first aspect of the present invention there may be provided the use of a compound as a corrosion inhibitor for metallic equipment, wherein the compound comprises (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

According to a second aspect of the present invention there is provided a method of preventing or reducing corrosion of metallic equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic equipment), wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

According to a second aspect of the present invention there may be provided a method of preventing or reducing corrosion of metallic equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic equipment), wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof According to a second aspect of the present invention there may be provided a method of preventing or reducing corrosion of metallic equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic equipment), wherein the compound comprises (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

The inventors have found that compounds as defined herein are surprisingly effective as corrosion inhibitors, especially for metallic oilfield equipment, pipelines, temperature control

B

jackets and chemical manufacturing plants, including refineries and petrochemical plants. For example, the compounds as defined herein may be surprisingly effective as corrosion inhibitors, especially for metallic pipelines and temperature control jackets.

Preferred features of the first and second aspects of the present invention will now be described.

Any feature may apply to any other aspect as appropriate.

Where reference is made to an or the anhydride thereof, this is intended to mean an anhydride of any of the polycarboxylic acid(s) listed in the text preceding this phrase. For example, the phrase "octenyl succinic acid, decenyl succinic acid or an anhydride thereof' means to include octenyl succinic acid, octenyl succinic anhydride, decenyl succinic acid and decenyl succinic anhydride.

The optionally substituted polycarboxylic acid or the anhydride thereof may comprise an optionally substituted tricarboxylic acid or tetracarboxylic acid or an anhydride thereof. Examples of suitable tricarboxylic acids include citric acid and trimesic acid. An example of a suitable tetracarboxylic acid is pyromellitic acid.

The optionally substituted polycarboxylic acid or the anhydride thereof may comprise an optionally substituted dicarboxylic acid or an anhydride thereof Examples of suitable dicarboxylic acids include 3,3'-thiodipropanoic acid, iminodiacetic acid, itaconic acid, tartaric acid, maleic acid, oxalic acid, malonic acid, succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, phthalic acid and sebacic acid. The optionally substituted dicarboxylic acid may be selected from oxalic acid, malonic acid, succinic acid, glutamic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, phthalic acid and sebacic acid, preferably from succinic acid and phthalic acid. Preferably, the optionally substituted dicarboxylic acid or the anhydride thereof comprises an optionally substituted succinic acid or an optionally substituted succinic anhydride.

The optionally substituted dicarboxylic acid or the anhydride thereof may be selected from octadecenyl succinic acid, decyl succinic acid, dodecyl succinic acid and phthalic acid or an anhydride thereof.

The optionally substituted polycarboxylic acid or the anhydride thereof is suitably substituted with a hydrocarbyl group. The optionally substituted polycarboxylic acid or the anhydride thereof is suitably substituted with an alkyl, alkenyl, alkynyl, alkaryl or aralkyl group, preferably an alkyl, alkenyl, alkaryl or aralkyl group, more preferably an alkyl or alkenyl group.

The alkyl or alkenyl group suitably has from 2 to 30 carbon atoms, such as from 4 to 22 carbon atoms, for example from 6 to 18 carbon atoms.

Preferably, the optionally substituted polycarboxylic acid or the anhydride thereof is substituted with an alkenyl group. The alkenyl group suitably has from 2 to 30 carbon atoms, such as from 4 to 22 carbon atoms, for example from 6 to 18 or from 8 to 12 carbon atoms. The alkenyl group may suitably be decenyl, octenyl (such as 2-octen-1-y1) or dodecenyl, preferably 2-octen-1-ylor dodecenyl. For example, the optionally substituted polycarboxylic acid or the anhydride thereof may comprise decenyl succinic acid, 2-octen-1-y1 succinic acid or dodecenyl succinic acid, preferably 2-octen-1-ylsuccinic acid or dodecenyl succinic acid.

In some embodiments the alkyl or alkenyl group is a polyisobutenyl group, preferably having a number average molecular weight of from 100 to 5000, preferably from 200 to 2000, suitably from 220 to 1300, for example from 240 to 900.

Suitably the optionally substituted polycarboxylic acid or the anhydride thereof comprises a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof. Preferably the optionally substituted polycarboxylic acid or the anhydride thereof comprises an alkyl or alkenyl substituted succinic acid or an anhydride thereof Most preferably, the optionally substituted polycarboxylic acid or the anhydride thereof comprises 2-octen-1-ylsuccinic acid, dodecenyl succinic acid or an anhydride thereof. Suitably, the optionally substituted polycarboxylic acid or the anhydride thereof comprises 2-octen-1-ylsuccinic anhydride or dodecenyl succinic anhydride.

The salt of the optionally substituted polycarboxylic acid or the anhydride thereof or the salt of the reaction product suitably comprises an alkali metal salt and/or an amine salt. References herein to salts thus refer to salts of the optionally substituted polycarboxylic acid or an anhydride thereof 0) and/or to salts of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine 00.

Suitable alkali metal salts include sodium salts and potassium salts. Sodium salts are preferred.

Alkali metal salts are suitably prepared by neutralising the optionally substituted polycarboxylic acid or the anhydride thereof with an alkali metal hydroxide.

Suitable amine salts are salts formed by any suitable amine. Suitable amines used to form the salt include ammonia, primary, secondary and tertiary amines, and quaternary ammonium compounds.

In some embodiments the amine used to form the salt is ammonia.

In some embodiments the amine used to form the salt is a quaternary ammonium compound.

In some preferred embodiments the amine used to form the salt is an aralkylamino, alkarylamino, alkylamino and/or hydroxyalkyl amino compound.

In some preferred embodiments the amine used to form the salt is an alkylamino and/or hydroxyalkyl amino compound. The amine is suitably substituted with one to three alkyl or hydroxyalkyl groups having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. The amine may be an alkylamine, a hydroxyalkylamine, a dialkylamine, a hydroxyalkyl alkyl amine, a dihydroxyalkylamine, a trialkylamine, a dialkylhydroxyalkylamine, a dihydroxyalkylalkylamine or a trihydroxyalkylamine. There are many different compounds of this type and these will be known to the person skilled in the art. In some embodiments the amine used to form the salt is a cyclic amine.

In some embodiments the amine salt comprises a primary amine salt. Suitable primary amines used to form a primary amine salt include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, 2-aminobutanol, ethanolamine, cyclohexylamine, aminopropanediol, isopropanolamine, mixed isopropanolamines, tromethamine, 1-phenylethylamine and benzyl amine.

In some embodiments the amine salt comprises a secondary amine salt.

Suitable secondary amine compounds used to form a secondary amine salt include dimethylamine, N,N-methylethylamine, N,N-methylpropylamine, N,N-methylbutylamine, diethylamine, N,N-ethylpropylamine, N,N-ethylbutylamine, dipropylamine, N,Npropylbutylamine, dibutylamine, N,N-butylmethylamine, N,N-butylethylamine, N,Nbutylpropylamine, N,N-methylmethanolamine, N,N-methylethanolamine, diethanolamine, N,Nmethylpropanolamine, dipropanolamine, N,N-methylbutanolamine, dibutanolamine, N,Nethylmethanolamine, N,N-ethylethanolamine, N,N-ethylpropanolamine, N,N-ethylbutanolamine, N,N-propylmethanolamine, N,N-propylethanolamine, N,N-propylpropanolamine, N,N- propylbutanolamine, N,N-butylmethanolamine, N,N-butylethanolamine, N,N-butylpropanolamine, N,N-butylbutanolamine, 2-(2-aminoethoxy)ethanol, aminoethyl propanediol, aminomethyl propanediol, aminoethyl propanol, diisopropylamine, diisopropanolamine, morpholine, hexamethylenetetramine (hexamine), N-methylbenzylamine, N-ethylbenzylamine, n-propylbenzylamine, dibenzylamine, hydroxyethylbenzylamine, polyethylene polyamines such as: diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and mixtures and isomers thereof.

Preferably the amine salt comprises a tertiary amine salt.

Suitable tertiary amine compounds used to form a tertiary amine salt include trimethylamine, N,N-dimethylethylamine, N,N-dimethylpropylamine, N,N-dimethylbutylamine, triethylamine, N,N-diethylmethylamine, N,N-diethylpropylamine, N,N-diethylbutylamine, tripropylamine, N,N5 dipropylmethylamine, N,N-dipropylethylamine, N,N-dipropylbutylamine, tributylamine, N,N- dibutylmethylamine, N,N-dibutylethylamine, N,N-dibutylpropylamine, N,N-dimethylmethanolamine, methyldimethanolamine, N,N-dimethylethanolamine, methyldiethanolamine, N,N-dimethylpropanolamine, methyldipropanolamine, N,N-dimethylbutanolamine, methyldibutanolamine, N,N-diethylmethanolamine, ethyldimethanolamine, N,N-diethylethanolamine, ethyldiethanolamine, N,N-diethylpropanolamine, ethyldipropanolamine, N,N-diethylbutanolamine, ethyldibutanolamine, N,N-dipropylmethanolamine, propyldimethanolamine, N,N-dipropylethanolamine, propyldiethanolamine, N,N-dipropylpropanolamine, propyldipropanolamine, N,N-dipropylbutanolamine, propyldibutanolamine, N,N-dibutylmethanolamine, butyldimethanolamine, N,N-dibutylethanolamine, butyldiethanolamine, N,N-dibutylpropanolamine, butyldipropanolamine, N,N-dibutylbutanolamine, butyldibutanolamine, trimethanolamine, triethanolamine, tripropanolamine, tributanolamine, diethylhexylamine, dimethyltolylamine, bis-hydroxyethyl tromethamine, dimethylamino methylpropanol, dimethyl isopropanolamine, dimethyl MEA, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), hydroxyethyl methyl tolyl amine, N,N-dimethylbenzylamine, N,N-diethylbenzylamine, N,Ndipropylbenzylamine, N,N-dihydroxyethylbenzylamine, triisopropanolamine, N,N-dimethyl-1,3-diaminopropane, N,N-diethyl-1,3-diaminopropane, N,N-dimethylethylenediamine, N,Ndiethylethylenediamine, N,N-dibutylethylenediamine, and mixtures and isomers thereof Preferably the amine used to form the salt comprises at least one hydroxyalkyl substituent.

Suitable amines of this type include but are not limited to triethanolamine, trimethanolamine, N,N-dimethylaminopropanol, N,N-dimethylaminoethanol, N,N-diethylaminopropanol, isopropanolamine, N,N-diethylaminoethanol, N,N-diethylaminobutanol, and N,N,N'-trimethyl-N'-hydroxyethyl-bisaminoethylether; N,N-bis(3-dimethylaminopropyI)-N-isopropanolamine; N-(3- dimethylaminopropyI)-N,N-diisopropanolamine; 2-(2-dimethylaminoethoxy)ethanol and N,N,N'-trimethylaminoethylethanolamine.

The salt of the optionally substituted polyc,arboxylic acid or the anhydride thereof may be a partial salt or a full salt of the acid/anhydride. By "partial salt" we mean that the compound comprises at least one free carboxylic acid group and by "full salt" we mean that all acid groups in the compound are in the form of a salt. For example, the compound may comprise a mono salt or di salt of a dicarboxylic acid or an anhydride thereof.

In some embodiments the compound comprises a di alkali metal salt of a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof Preferably the compound comprises a disodium or dipotassium salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof More preferably the compound comprises a disodium salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof, such as 2-octen-1-ylsuccinic acid, dodecenyl succinic acid or an anhydride thereof.

In some embodiments the compound comprises a mono amine salt of a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof Suitably the compound comprises a mono tertiary or quaternary amine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof. In some embodiments the compound comprises a mono quaternary amine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof. Preferably the compound comprises a mono tertiary amine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof More preferably the compound comprises a mono triethanolamine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof, such as 2-octen-1-ylsuccinic acid, dodecenyl succinic acid or an anhydride thereof.

In some embodiments the compound comprises a bis amine salt of a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof. Suitably the compound comprises a bis tertiary or quaternary amine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof. In some embodiments the compound comprises a bis quaternary amine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof. Preferably the compound comprises a bis tertiary amine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof. More preferably the compound comprises a bis triethanolamine salt of an alkyl or alkenyl substituted succinic acid or an anhydride thereof, such as 2-octen-1-y1 succinic acid, dodecenyl succinic acid or an anhydride thereof.

In some embodiments of the first, second and third aspects of the present invention, the compound may comprise the reaction product of reactants consisting essentially, or consisting of, an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

The compound may comprise the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol, or a salt of the reaction product.

The alcohol may comprise from 1 to 40 carbon atoms, such as from 6 to 30 carbon atoms, for example from 6 to 20 carbon atoms.

The alcohol may comprise a monohydric alcohol or a polyhydric alcohol. A suitable polyhydric alcohol may have from 2 to 4 hydroxy groups.

The alcohol may be optionally substituted, for example optionally substituted by one or more substituent selected from an alkyl, alkenyl, aralkyl and alkaryl group.

Suitable alcohols substituted by an aralkyl group for use to form the reaction product include 1-or 2-phenyl ethanol, 3-or 4-pyridinyl methanol, napthalene methanol, benzyl alcohol (optionally wherein the benzyl group is substituted, for example by an alkyl group), and furfuryl alcohol.

Preferably, the alcohol substituted by an aralkyl group comprises furfuryl alcohol or benzyl alcohol.

Suitable monohydric alcohols for use to form the reaction product include methanol, ethanol, propanol, isopropanol, benzyl alcohol, tetradecanol, butanol, 2-butanol, isobutanol, octanol, 2-ethylhexanol, hexanol, cyclohexanol, cyclooctanol, 2-propylheptanol, 2-ethyl-l-butanol and isopropanol.

Suitable monohydric alcohols for use to form the reaction product include methanol, ethanol, propanol, isopropanol, benzyl alcohol, tetradecanol, butanol, 2-butanol, isobutanol, octanol, 2-ethylhexanol, hexanol, cyclohexanol, cyclooctanol, 2-propylheptanol, 2-ethyl-1-butanol, furfuryl alcohol and isopropanol.

The polyhydric alcohol may have 2 hydroxy groups. Suitably the polyhydric alcohol comprises an alkylene glycol or a polyalkylene glycol. Preferably the polyhydric alcohol comprises a polyalkylene glycol.

The alkylene glycol may be selected from ethylene glycol, propylene glycol, 1,3-butanediol 1,4-butanediol, 1,6-hexanediol, or 2-ethyl-1,3-hexanediol. The alkylene glycol is suitably selected from ethylene glycol, propylene glycol, 1,3-butanediol or 1,4-butanediol.

The polyalkylene glycol is suitably selected from polyethylene glycol, polypropylene glycol or polybutylene glycol, or copolymers thereof Suitable copolymers of polyalkylene glycols include copolymers of ethylene glycol and propylene glycol and copolymers of ethylene glycol and butylene glycol. The polyalkylene glycol is suitably polyethylene glycol or polypropylene glycol.

Preferably the polyalkylene glycol is polyethylene glycol.

The polyhydric alcohol may have a number average molecular weight of from 60 to 6000, such as from 80 to 3000, such as from 100 to 2000, preferably from 120 to 1500, more preferably from 150 to 1200, more preferably from 170 to 1000, even more preferably from 190 to 850.

The skilled person would be familiar with standard techniques to measure number average molecular weight, such as by Vapor pressure osmometry, End-group titration, Proton NMR, Boiling point elevation, Freezing depression (cryoscopy), and GPC (Gel Permeation Chromatography).

In some embodiments the number average molecular weight of the polyhydric alcohol is from 60 to 370, suitably from 110 to 320, for example from 190 to 210.

In some embodiments the number average molecular weight of the polyhydric alcohol is from to 650, suitably from 300 to 550, for example from 400 to 450, In some embodiments the number average molecular weight of the polyhydric alcohol is from 400 to 950, suitably from 500 to 840, for example from 570 to 630.

In some embodiments the number average molecular weight of the polyhydric alcohol is from 700 to 1300, suitably from 800 to 1200, for example from 900 to 1100.

In some embodiments the polyalkylene glycol comprises polyethylene glycol having a number average molecular weight of from 60 to 370, preferably from 190 to 210, or from 400 to 950, preferably from 570 to 630.

In some embodiments the polyalkylene glycol may be a polyethylene glycol having a number average molecular weight of 200.

In some embodiments the polyalkylene glycol may be a polyethylene glycol having a number average molecular weight of 600.

In some embodiments the polyalkylene glycol may be a polyethylene glycol having a number average molecular weight of 1000.

In some embodiments the polyalkylene glycol may be a polypropylene glycol having a number average molecular weight of 200 to 650, preferably from 400 to 450, for example 425.

The polyhydric alcohol used to form the reaction product may have more than 2 hydroxy groups, such as 3, 4, 5 or 6 (for example 3 or 4) hydroxy groups. For example the polyhydric alcohol may be glycerol, pentaerythritol, trimethylolpropane, sorbitol or mannitol.

The alcohol may comprise a hydroxyalkyl amino compound. The amine is suitably substituted with one to three hydroxyalkyl groups having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. The amine may be a hydroxyalkylamine, a hydroxyalkyl alkyl amine, a dihydroxyalkylamine, a dialkylhydroxyalkylamine, a dihydroxyalkylalkylamine or a trihydroxyalkylamine. Suitable amines of this type include but are not limited to N,N-methylmethanolamine, N,N-methylethanolamine, diethanolamine, N,N-methylpropanolamine, dipropanolamine, N,N-methylbutanolamine, dibutanolamine, N,N-ethylmethanolamine, N,N- ethylethanolamine, N,N-ethylpropanolamine, N,N-ethylbutanolamine, N,N- propylmethanolamine, N,N-propylethanolamine, N,N-propylpropanolamine, N,N- propylbutanolamine, N,N-butylmethanolamine, N,N-butylethanolamine, N,N-butylpropanolamine, N,N-butylbutanolamine, 2-(2-aminoethoxy)ethanol, aminoethyl propanediol, aminomethyl propanediol, aminoethyl propanol, diisopropanolamine, triethanolamine, trimethanolamine, N,N-dimethylaminopropanol, N,N-dimethylaminoethanol, N,N-diethylaminopropanol, isopropanolamine, N,N-diethylaminoethanol, N,N- diethylaminobutanol, and N,N,N1-trimethyl-N'-hydroxyethyl-bisaminoethylether; N,N-bis(3- dimethylaminopropy1)-N-isopropanolamine; N-(3-dimethylaminopropyI)-N,N- diisopropanolamine; 2-(2-dimethylaminoethoxy)ethanol, N,N,N'-trimethylaminoethylethanolamine, and N-butyldiethanolamine.

In some embodiments, the alcohol is selected from n-propanol, 1-hexanol, 1-octanol, 2-ethylhexanol, dodecanol, benzyl alcohol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, diethanolamine, triethanolamine, N-butyldiethanolamine, polyethylene glycol having a number average molecular weight of 200, 600 or 1000, or polypropylene glycol having a number average molecular weight of 425.

In some embodiments, the alcohol is selected from n-propanol, 1-hexanol, 1-octanol, 2-ethylhexanol, dodecanol, benzyl alcohol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, diethanolamine, triethanolamine, N-butyldiethanolamine, furfuryl alcohol, polyethylene glycol having a number average molecular weight of 200, 600 or 1000, or polypropylene glycol having a number average molecular weight of 425.

Preferably the acid/anhydride and the alcohol are reacted in a molar ratio of from 10:1 to 110, preferably from 5:1 to 1:5, more preferably from 21:1 to 1:2.1, for example from 1.5:1 to 11.5.

Typically, the reaction product of reactants comprising the acid/anhydride and the alcohol comprises a mono ester formed by 1 acid/anhydride moiety reacting with 1 moiety of the alcohol, and/or a bis ester formed by 2 acid/anhydride moieties reacting with 1 polyhydric alcohol equivalent. Persons skilled in the art will appreciate that such reaction products typically comprise a mixture of reaction products, i.e. a mixture of mono and bis esters. For example, when a reaction is intended to form a mono-ester product, the product so formed may additionally comprise a bis ester product and vice versa. The reaction product may comprise any mixture of isomers such as regioisomers. The reaction product may further comprise unreacted reactants and/or reaction by-products.

In some embodiments the acid/anhydride and the alcohol are reacted in a molar ratio of from 1.5:1 to 1:1.5, such as from 1.3:1 to 1:1.3, for example 1:1.1 to 1.1:1, for example 1:1.

In some embodiments the acid/anhydride and the alcohol are reacted in a molar ratio of from 1.5:1 to 2.5:1, such as from 1.7:1 to 2.3:1, for example 2:1. Preferably the alcohol comprises a polyhydric alcohol.

The salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol is suitably an alkali metal salt, preferably a sodium or potassium salt, more preferably a sodium salt.

The salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol is suitably a tertiary amine salt, preferably wherein the tertiary amine comprises at least one hydroxyalkyl substituent, more preferably wherein the tertiary amine comprises triethanolamine.

In some embodiments the compound comprises a salt (such as a sodium salt) of the reaction product of reactants comprising an optionally substituted anhydride of octadecenyl succinic acid, decyl succinic acid, dodecyl succinic acid and phthalic acid and an alcohol selected from hexanol, PPG 425, PEG 200, benzyl alcohol, dodecanol, PEG 600 and furfuryl alcohol.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and an alcohol selected from n-propanol, 1-hexanol, 1-octanol, 2-ethylhexanol, dodecanol, benzyl alcohol, 1,6- hexanediol, 2-ethyl-1,3-hexanediol, diethanolamine, triethanolamine, furfuryl alcohol, and N- butyldiethanolamine wherein the acid/anhydride and the alcohol are reacted in a molar ratio of from 1.5:1 to 11.5. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and an alcohol selected from n-propanol, 1-hexanol, 1-octanol, 2-ethylhexanol, dodecanol, benzyl alcohol, 1,6-hexanediol, 2-ethyl-1,3-hexanediol, diethanolamine, triethanolamine, furfuryl alcohol, and N-butyldiethanolamine wherein the acid/anhydride and the alcohol are reacted in a molar ratio of 1:1.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a polyalkylene glycol, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of from 1.5:1 to 1:1.5. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 60 to 370, such as from 190 to 210, for example 200, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 1:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride therof and a polyalkylene glycol having a number average molecular weight of from 200 to 650, such as from 400 to 450, for example 425, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 1:1.

Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 400 to 950, such as from 570 to 630, for example 600, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 1:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 700 to 1300, such as from 900 to 1100, for example 1000, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 1:1.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a polyethylene glycol, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of from 1.5:1 to 1:1.5. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyethylene glycol having a number average molecular weight of 200, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of 1:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyethylene glycol having a number average molecular weight of 600, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of 1:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyethylene glycol having a number average molecular weight of 1000, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of 1:1.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarbox0ic acid or an anhydride thereof and a polypropylene glycol, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of from 1.5:1 to 1:1.5. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polypropylene glycol having a number average molecular weight of 425, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of 1:1.

In some embodiments the compound comprises the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a polyalkylene glycol, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of from 1.5:1 to 2.5:1. Preferably the compound comprises the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 60 to 370, such as from 190 to 210, for example 200, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 2:1.

Preferably the compound comprises the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 400 to 950, such as from 570 to 630, for example 600, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 2:1.

In some embodiments the compound comprises the reaction product of reactants comprising a hydrocarbyl substituted dicarbmilic acid or an anhydride thereof and a polyethylene glycol, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of from 1.5:1 to 2.5:1. Preferably the compound comprises the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyethylene glycol having a number average molecular weight of 600, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of 2:1.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboWic acid or an anhydride thereof and a polyalkylene glycol, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of from 1.5:1 to 2.5:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 60 to 370, such as from 190 to 210, for example 200, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 2:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyalkylene glycol having a number average molecular weight of from 400 to 950, such as from 570 to 630, for example 600, wherein the acid/anhydride and the polyalkylene glycol are reacted in a molar ratio of 2:1.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a polyethylene glycol, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of from 1.5:1 to 2.5:1. Preferably the compound comprises a sodium or potassium (preferably sodium) salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and a polyethylene glycol having a number average molecular weight of 200, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of 2:1.

The compound may comprise the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an amine, or a salt of the reaction product.

Any suitable amine may be used to form the reaction product. Suitably the amine for use to form the reaction product comprises a primary or secondary amine.

In some preferred embodiments the amine for use to form the reaction product is an alkylamino and/or hydroxyalkyl amino compound. The amine is suitably substituted with one or two alkyl or hydroxyalkyl groups having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. The amine may be an alkylamine, a hydroxyalkylamine, a dialkylamine, a hydroxyalkyl alkyl amine, or a dihydroxyalkylamine. There are many different compounds of this type and these will be known to the person skilled in the art. In some embodiments the amine is a cyclic amine.

In some embodiments the amine for use to form the reaction product comprises a primary amine. Suitable primary amines include methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, 2-aminobutanol, ethanolamine, cyclohexylamine, aminopropanediol, isopropanolamine, mixed isopropanolamines, tromethamine, 3-dimethylaminopropylamine and benzyl amine. The primary amine may be selected from methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, 2-aminobutanol, ethanolamine, cyclohexylamine, aminopropanediol, isopropanolamine, mixed isopropanolamines, tromethamine and benzyl amine.

Preferably the amine for use to form the reaction product comprises a secondary amine.

Suitable secondary amine compounds for use to form the reaction product include dimethylamine, N,N-methylethylamine, N,N-methylpropylamine, N,N-methylbutylamine, 5 diethylamine, N,N-ethylpropylamine, N,N-ethylbutylamine, dipropylamine, N,N- propylbutylamine, dibutylamine, N,N-butylmethylamine, N,N-butylethylamine, N,N-butylpropylamine, N,N-methylmethanolamine, N,N-methylethanolamine, diethanolamine, N,Nmethylpropanolamine, dipropanolamine, N,N-methylbutanolamine, dibutanolamine, N,Nethylmethanolamine, N,N-ethylethanolamine, N,N-ethylpropanolamine, N,N-ethylbutanolamine, N,N-propylmethanolamine, N,N-propylethanolamine, N,N-propylpropanolamine, N,N- propylbutanolamine, N,N-butylmethanolamine, N,N-butylethanolamine, N,N-butylpropanolamine, N,N-butylbutanolamine, 2-(2-aminoethoxy)ethanol, aminoethyl propanediol, aminomethyl propanediol, aminoethyl propanol, diisopropylamine, diisopropanolamine, morpholine, N-methylbenzylamine, N-ethylbenzylamine, n-propylbenzylamine, dibenzylamine, hydroxyethylbenzylamine, polyethylene polyamines such as: diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA) and mixtures and isomers thereof.

In some embodiments, the amine is selected from propylamine, octylamine, 3-dimethylaminopropylamine, and benzyl amine.

Suitably the amine for use to form the reaction product is substituted with at least one hydroxyalkyl group. Persons skilled in the art would understand that the reaction product of reactants comprising an amine substituted with at least one hydroxyalkyl group and an acid/anhydride may comprise a mixture of primarily amide reaction products with a minor amount of the ester reaction product. Preferably the amine for use to form the reaction product comprises a dihydroxyalkylamine such as diethanolamine.

Preferably the acid/anhydride and the amine are reacted in a molar ratio of from 10:1 to 1:10, preferably from 5:1 to 1:5, more preferably from 2:1 to 1:2, for example from 1.5:1 to 1:1.5.

In some embodiments the acid/anhydride and the amine are reacted in a molar ratio of from 1.5:1 to 1:1.5, such as from 1.3:1 to 1:1.3, for example 1:1 The salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an amine is suitably an alkali metal salt, preferably a sodium or potassium salt, more preferably a sodium salt.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a primary amine, wherein the acid/anhydride and the primary amine are reacted in a molar ratio of from 1.5:1 to 1:1.5. Preferably the compound comprises a sodium salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or an anhydride thereof and an amine selected from propylamine, octylamine, 3-dimethylaminopropylamine, and benzyl amine, wherein the acid/anhydride and the amine are reacted in a molar ratio of 1:1.

In some embodiments the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarbox0ic acid or an anhydride thereof and a dihydroxyalkylamine, wherein the acid/anhydride and the dihydroxyalkylamine are reacted in a molar ratio of from 1.5:1 to 1:1.5. Preferably the compound comprises a sodium salt of the reaction product of reactants comprising an alkyl or alkenyl substituted succinic acid or n anhydride thereof and diethanolamine, wherein the acid/anhydride and the diethanolamine are reacted in a molar ratio of 1:1.

The compound suitably comprises a compound of formula (I): (I) wherein X is a linking group; R1 is ant, o(R3o)nR4, or NR5R6; and R2 is OH, ant, o(R3o)nR4, or NR5R6; wherein each W is independently a cation; each R3 is independently an optionally substituted alkylene group; each R4 is independently hydrogen or an optionally substituted hydrocarbyl group; each R5 is independently hydrogen or an optionally substituted hydrocarbyl group; each R6 is independently an optionally substituted hydrocarbyl group; each n is independently 0 or a positive integer, provided that n is not 0 when R4 is hydrogen.

X in formula (I) is preferably an optionally substituted hydrocatylene group. Preferably X is an optionally substituted alkylene group. Preferably X is a substituted alkylene group.

Suitably X is an alkyl or alkenyl substituted alkylene group.

Preferably X is an alkenyl substituted alkylene group.

Preferably X is an alkenyl substituted alkylene group wherein the alkylene group has from 1 to 10, preferably from 1 to 6, suitably from 1 to 4, preferably 2 or 3, and most preferably 2 carbon atoms in the alkylene chain.

In some preferred embodiments X is CH2CHR or CHRCH2 wherein R is an alkyl, alkenyl or alkynyl group. R may be an alkyl or alkenyl group. such as an alkyl or alkenyl group having from 6 to 18, for example from 8 to 12 carbon atoms. Preferably R is an alkenyl group, for example having from 6 to 18, for example from 8 to 12 carbon atoms.

The compound may comprise a compound of formula (IA) or (IB): (IA) (I B) wherein each of R1, R2 and R is as defined herein.

M+ is suitably an alkali metal cation or an ammonium cation. Suitable alkali metal cations include sodium and potassium. Sodium is preferred.

The ammonium cation may have the formula IR7R8R9R10.N, wherein each of R7, Ra, R9 and R1° is independently hydrogen, an alkyl group, an aralkyl group, an alkaryl group or a hydroxyalkyl group. Each of R7, R8, R9 and R1° may be the same or different. Suitably each of R7, R8, R9 and R1° is independently selected from hydrogen and an alkyl or hydroxyalkyl group having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. Each of R7, IR8, R9 and R1° may be independently selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl and isomers thereof Suitably R1° is hydrogen and each of R7, R8 and R9 is independently an alkyl group or a hydroxyalkyl group having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. Preferably R19 is hydrogen and each of R7, R8 and R9 is a hydroxyalkyl group having from Ito 6 carbon atoms, for example from 1 to 4 carbon atoms, such as hydroxyethyl.

R3 is an optionally substituted alkylene group. R3 may be straight chained or branched.

Preferably R3 is an optionally substituted alkylene group having from 1 to 50 carbon atoms, preferably from 1 to 40 carbon atoms, preferably from 1 to 30 carbon atoms, more preferably from 1 to 20 carbon atoms, suitably from 1 to 10 carbon atoms, for example from 2 to 6 or from 2 to 4 carbon atoms.

Preferably R3 is an unsubstituted alkylene group.

Preferably R3 is an unsubsfituted alkylene group having from 1 to 50 carbon atoms, preferably from 1 to 20, more preferably from 1 to 10, suitably from 2 to 6, for example from 2 to 4 carbon atoms.

Suitably R3 may be an ethylene, propylene, butylene, pentylene, or hexylene group. When R3 has more than 2 carbon atoms any isomer may be present. Preferably R3 is an ethylene or a propylene group, most preferably an ethylene group.

In some embodiments in which n is 1, R3 may be a group of formula (CH2)x wherein x is from 2 to 12, preferably from 2 to 6.

R3 may comprise a mixture of isomers. For example when R3 is propylene, the polyhydric alcohol may include moieties -CH2CH(CH3)-and -CH(CH3)CH2-in any order within the chain.

R3 may comprise a mixture of different groups for example ethylene, propylene or butylene units.

Block copolymer units are preferred in such embodiments.

R3 is preferably an ethylene, propylene or butylene group. R3 may be an n-propylene or nbutylene group or an isopropylene or isobutylene group. For example R3 may be -CH2CH2-, -CH2CH(CH3)-, -CH2C(CH3)2, -CI-1(CH3)CH(0H3)-or -CH2CH(CH2CH3)-.

Preferably R3 is ethylene or propylene. More preferably R3 is -CH2CH2-or -CH(CH3)CH2-. Most preferably R3 is -CH2CH2-.

Suitably n is from 0 to 30, preferably from 0 to 20, such as from 1 to 16. n is not 0 when R4 is hydrogen.

In some embodiments n is at least 1. Preferably n is from 2 to 30, preferably from 2 to 20, more preferably from 4 to 20, preferably from 4 to 14.

R4 is hydrogen or an optionally substituted hydrocarbyl group.

In some embodiments n is 0 and the compound of formula I may be formed from an alcohol of formula R4OH. In such embodiments R4 is suitably an optionally substituted alkyl, alkenyl, aryl, or aralkyl group, preferably having from 1 to 60, preferably from 10 to 40, carbon atoms. Preferably R4 is an optionally substituted alkyl group. In some embodiments R4 is a hydroxy In some preferred embodiments R4 is an unsubstituted alkyl group. The alkyl group may be straight chained or branched. In some embodiments R4 is an optionally substituted alkyl group having from 4 to 40, preferably from 6 to 30, more preferably from 10 to 20 carbon atoms.

In some embodiments n is 0 and R4 is an optionally substituted C6 to C36 alkyl group, preferably an optionally substituted C8 to C30 alkyl group, more preferably an optionally substituted Cm o to C20 alkyl group.

In some embodiments n is not 0 and the compound of formula (I) may suitably be formed from an alcohol of formula HO(R30)R4.

In some embodiments R4 is a residue of the formula -C(0)-X'-C(0)-R2' wherein Xis defined according to X herein and R2 is defined according to R2 herein.

The compound of formula I may therefore be represented by the formula (I'): 0 0 (r) R2 X 0(R30)n wherein each of R2, X, R3, n, X' and R2 is as defined herein.

In the formula (II R2 and R2 may be the same and/or X and X' may be the same.

When R4 is hydrogen the compound of formula (I) is suitably an ester of an alkylene glycol or a polyalkylene glycol When R4 is not hydrogen, the compound of formula (I) may be formed by reaction of the optionally substituted dicarboxylic acid with an alkylene glycol or polyalkylene glycol which is subsequently reacted to form an ether, or a compound of formula HO(R30)R4 may be reacted with the optionally substituted dicatoxylic acid.

R5 may be hydrogen, an alkyl group, a hydroxyalkyl group, a dialkylaminoalkyl group, an alkenyl group, an aryl group, or an aralkyl group. R5 maybe hydrogen or an alkyl group or a hydroxyalkyl group. Suitably R5 is selected from hydrogen and an alkyl or hydroxyalkyl group having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. R5 may be selected from hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, hydroxyheptyl, hydroxyoctyl, 3-dimethylaminopropyl, benzyl and isomers thereof Suitably R5 is an alkyl group or a hydroxyalkyl group. Preferably R5 is a hydroxyalkyl group, such as hydroxyethyl.

R6 may be an alkyl group, a hydroxyalkyl group, a dialkylaminoalkyl group, an alkenyl group, an aryl group, or an aralkyl group. R6 may be an alkyl group or a hydroxyalkyl group. Suitably R6 is selected from an alkyl or hydroxyalkyl group having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms. R6 may be selected from methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl, hydroxyheptyl, hydrwojoctyl, 3-dimethylaminopropyl, benzyl and isomers thereof.

Preferably R6 is a hydroxyalkyl group, such as hydroxyethyl.

Preferably both R5 and R6 area hydroxyalkyl group having from 1 to 6 carbon atoms, for example from 1 to 4 carbon atoms, such as hydroxyethyl. Suitably both R5 and R6 are the same.

In some embodiments R1 is 0-M+, O(R30)R4 or NR5R6 and R2 is crt or OH.

In some embodiments R1 and R2 are each 0-M+, or R1 is 0-M+ and R2 is 0-M' or OH, or R1 is 0(R30),R4 and R2 is 0-M± or OH, or R1 is NR5R6 and R2 is 0-M+ or OH.

In some embodiments R1 and R2 are each 0 NV In some embodiments R1 is ant and R2 is at or OH.

In some embodiments R1 is O(R30)R4 and R2 is ow+ or OH.

In some embodiments R1 is NR5R6 and R2 is 0-M' or OH.

In the use and method of the first and second aspects of the present invention, the metallic equipment suitably comprises iron, zinc, aluminium, copper or steel.

According to a preferred embodiment of the first aspect of the present invention there may provided the use of a compound as a corrosion inhibitor for metallic equipment, wherein the 20 compound comprises (i) an amine salt of an optionally a hydrocarbyl substituted polycarboxylic acid or an anhydride thereof; and/or (ii) a salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyalkylene glycol an alcohol and/or an amine, or a salt of the reaction product; and/or (iii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a primary or secondary amine substituted with at least one hydroxyalkyl group, or a salt of the reaction product.

According to a preferred embodiment of the second aspect of the present invention there may be provided a method of preventing or reducing corrosion of metallic equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic equipment), wherein the compound comprises (i) an amine salt of an optionally a hydrocarbyl substituted polycarboxylic acid or an anhydride thereof; and/or (ii) a salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyalkylene glycol an alcohol and/or an amine, or a salt of the reaction product; and/or (iii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a primary or secondary amine substituted with at least one hydroxyalkyl group, or a salt of the reaction product.

Suitably the metallic equipment comprises metallic industrial equipment. Examples of suitable metallic industrial equipment include pipelines, metallic oilfield equipment, desalination plants, mining equipment, power plants, cooling towers, heating systems (such as boilers and refinery re-boilers), cooling and refrigerant systems, temperature control jackets, wastewater treatment plants, electronic equipment or chemical manufacturing plants (including refineries and petrochemical plants).

Suitably, the metallic industrial equipment is selected from metallic oilfield equipment, such as pipelines, and chemical manufacturing plants (including refineries and petrochemical plants). Preferably, the metallic equipment is selected from metallic oilfield equipment.

Suitably, the metallic equipment is selected from metallic pipelines and temperature control jackets.

In some embodiments the metallic equipment comprises metallic domestic equipment.

Examples of suitable metallic domestic equipment include domestic heating systems such as boilers.

According to a preferred embodiment of the first aspect of the present invention there may provided the use of a compound as a corrosion inhibitor for metallic oilfield equipment, wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or Op the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

According to a preferred embodiment of the second aspect of the present invention there may be provided a method of preventing or reducing corrosion of metallic oilfield equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic oilfield equipment), wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.

According to a preferred embodiment of the first aspect of the present invention there may be provided the use of a compound as a corrosion inhibitor for metallic oilfield equipment, wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally a hydrocatyl substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product; and/or (iii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a primary or secondary amine, or a salt of the reaction product.

According to a preferred embodiment of the second aspect of the present invention there may be provided a method of preventing or reducing corrosion of metallic oilfield equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic oilfield equipment), wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally a hydrocarbyl substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product; and/or (iii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a primary or secondary amine, or a salt of the reaction product.

In the use or method of the first and second aspects, preferably a surface of the metallic equipment is, or will be, in contact with a corrosive fluid.

The corrosive fluid suitably comprises an aqueous fluid, such as brine. By "brine" we mean an aqueous fluid comprising a higher level of dissolved salts, commonly referred to as Total Dissolved Solids (IDS), such as NaCI, KCI, CaCl2 than tapwater. Commonly, oilfield brines may comprise a higher IDS level than seawater.

The brine may have a TDS of at least 1,000mg/I, or greater than 10,000mg/I, preferably greater than 35,000mg/I.

The corrosive fluid suitably comprises a fluid produced from an oil or gas well. The corrosive fluid typically comprises a complex mixture of naturally occurring compounds. Such a fluid may comprise crude oil, natural gas, and/or an emulsion thereof with an aqueous fluid, such as brine.

The corrosive fluid may comprise brine in an amount of at least 20% by volume, such as at least 50% by volume, for example at least 80% by volume. In some embodiments, the corrosive fluid may comprise brine in an amount of 100% by volume.

Alternatively, the corrosive fluid may comprise brine and a further component. The further component suitably comprises a hydrocarbon composition, The hydrocarbon composition comprises one or more hydrocarbons. The hydrocarbon composition may be crude oil or natural gas.

The corrosive fluid comprising the brine and the hydrocarbon composition is suitably in the form of an emulsion. Suitably, the emulsion comprises the brine and the hydrocarbon composition in a volume ratio of from 50:50 to 99:1, such as from 75:25 to 98:2, for example from 85:15 to 95:5; preferably 90:10.

By "brine" we mean an aqueous fluid having a higher salinity than tap water. For example, water comprising at least 1000 g/L of sodium.

The method of the second aspect may comprise applying the compound to at least a portion of a surface of the metallic equipment and/or adding the compound to the corrosive fluid.

The compound as defined herein may be used (in all aspects of the invention) as a corrosion inhibitor at a suitable treat rate (i.e. so as to provide an effect as a corrosion inhibitor), such as at a treat rate of from 1 to 10,000 ppm, for example from 2 to 5,000 ppm, such as from 5 to 1,500 ppm, or preferably from 50 to 1000 ppm (based on active corrosion inhibitor). The compound may be used at a treat rate of from 1 to 250 ppm, such as from 1 to 100 ppm, for example from 1 to 60 ppm, or preferably from 1 to 50 ppm.

In some embodiments, the compound as defined herein may be used as a corrosion inhibitor/ to prevent or reduce corrosion of metallic equipment at ambient temperature, for example at a temperature of from 0 to 35°C. In some preferred embodiments, the compound as defined herein may be used as a corrosion inhibitor/ to prevent or reduce corrosion of metallic equipment at a temperature greater than ambient temperature, for example at a temperature of from 40 to 220°C or from 60 to 180°C.

In some embodiments, the compound as defined herein may provide corrosion protection of at least 60%, such as at least 75%, preferably at least 90%, when measured according to the Linear Polarisation Resistance (LPR) Test as defined herein in Example 30.

In some embodiments, the compound as defined herein may provide corrosion protection of at least 60%, such as at least 75%, preferably at least 90%, when measured according to the Linear Polarisation Resistance (LPR) Test as defined herein in Example 30 wherein the treat rate of the compound is 10 ppm.

In some embodiments, the compound as defined herein may provide corrosion protection of at least 60%, such as at least 75%, preferably at least 90%, when measured according to the Linear Polarisation Resistance (LPR) Test as defined herein in Example 30 wherein the treat rate of the compound is 10 ppm and the test is conducted for a period of at least 20 hours.

In some embodiments, the compound as defined herein may be used as a corrosion inhibitor/ to prevent or reduce corrosion of metallic equipment at a temperature above 200°C, for example when used in a refinery reboiler.

In some embodiments, for example in offshore oil and gas applications, the compound as defined herein may be used as a corrosion inhibitor/ to prevent or reduce corrosion of metallic equipment at a temperature greater than the freezing point of the corrosive liquid.

The compound as defined herein may be used as a corrosion inhibitor to prevent or reduce corrosion of metallic equipment caused by a corrosive fluid that is oxidative and/or acidic, such as a corrosive fluid having a pH of less than 7, for example a pH of from 4.0 to 6.5. In some embodiments the corrosive fluid consists essentially of air or water, for example having a pH of from 6.5 to 7.5.

Wien the metallic equipment is selected from metallic oilfield equipment, the oilfield equipment may come into contact with oxidative and/or acidic species during an oilfield treatment operation or when the produced fluids are being returned to the surface or after production has ceased. The oxidative and/or acidic species may be contained within a treatment fluid, crude oil or gas produced from an oil or gas well, an aqueous fluid produced from the well or may be in the air, i.e. atmospheric corrosion.

The compound as defined herein may be used in conjunction with an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivafion agents), gel degrading agents and additives to control gas hydrate formation.

In some embodiments the use and method of the first and second aspects does not comprise metal working or cleaning.

According to a third aspect of the present invention, there may be provided a composition for inhibiting the corrosion of metallic equipment, the composition comprising: (a) a compound comprising (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a third aspect of the present invention, there may be provided a composition for inhibiting the corrosion of metallic equipment, the composition comprising: (a) a compound comprising (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a preferred embodiment of the third aspect of the present invention, there may be provided a composition for inhibiting the corrosion of metallic equipment, the composition comprising: (a) a compound comprising (i) an amine salt of an optionally a hydrocarbyl substituted polycarboxylic acid or an anhydride thereof; and/or (ii) a salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyalkylene glycol an alcohol and/or an amine, or a salt of the reaction product; and/or (iii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a primary or secondary amine substituted with at least one hydroxyalkyl group, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a preferred embodiment of the third aspect of the present invention, there may be provided a composition for inhibiting the corrosion of metallic oilfield equipment, the composition comprising: (a) a compound comprising (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a preferred embodiment of the third aspect of the present invention, there may be provided a composition for inhibiting the corrosion of metallic oilfield equipment, the composition comprising: (a) a compound comprising (i) an amine salt of an optionally a hydrocarbyl substituted polycarboxylic acid or an anhydride thereof; and/or (ii) a salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyalkylene glycol an alcohol and/or an amine, or a salt of the reaction product; and/or (iii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a primary or secondary amine substituted with at least one hydroxyalkyl group, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

Preferably, the additive (b) is selected from corrosion inhibitors other than compound (a), and scale inhibitors.

Suitable corrosion inhibitors other than compound (a) include amine corrosion inhibitors and quaternary ammonium corrosion inhibitors.

Any feature of any aspect of any invention or embodiment described herein may be combined with any aspect of any other invention or embodiment described herein mutatis mutandis. For example, suitable features of the metallic equipment and the compound in the third aspect are as defined for the first and second aspects.

According to a fourth aspect of the present invention, there may be provided the use of a compound as a corrosion inhibitor, wherein the compound comprises (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof.

According to a fourth aspect of the present invention, there may be provided the use of a compound as a corrosion inhibitor, wherein the compound comprises (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.

The corrosion inhibitor according to the fourth aspect may be used to prevent corrosion in equipment that comes into contact with aqueous fluids, especially brines. The corrosion inhibitor may be used to prevent corrosion in metallic equipment, especially equipment as defined in the first and second aspects of the present invention. The metallic equipment suitably comprises iron, zinc, aluminium, copper or steel. Examples of suitable metallic equipment include pipelines, metallic oilfield equipment, desalination plants, mining equipment, power plants, cooling towers, heating systems such as boilers and refinery re-boilers, cooling and refrigerant systems, temperature control jackets, wastewater treatment plants, electronic equipment or chemical manufacturing plants (including refineries and petrochemical plants).

According to a fifth aspect of the present invention, there may be provided a method of preventing or reducing corrosion of a metallic surface, the method comprising contacting at least a portion of the metallic surface with a compound comprising (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof According to a fifth aspect of the present invention, there may be provided a method of preventing or reducing corrosion of a metallic surface, the method comprising contacting at least a portion of the metallic surface with a compound comprising (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.

According to a sixth aspect of the present invention, there is provided a composition for inhibiting the corrosion of a metallic surface, the composition comprising: (a) a compound comprising (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a sixth aspect of the present invention, there may be provided a composition for inhibiting the corrosion of a metallic surface, the composition comprising: (a) a compound comprising (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

According to a sixth aspect of the present invention, there may be provided a composition for inhibiting the corrosion of a metallic surface, the composition comprising: (a) a compound comprising (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.

In some embodiments of the fifth and sixth aspects, the metallic surface may be a surface of metallic equipment, especially equipment as defined in the first and second aspects of the present invention. The metallic equipment suitably comprises iron, zinc, aluminium, copper or steel. Suitable examples of metallic equipment include pipelines, metallic oilfield equipment, desalination plants, mining equipment, power plants, cooling towers, heating systems such as boilers and refinery re-boilers, cooling and refrigerant systems, temperature control jackets, wastewater treatment plants, electronic equipment or chemical manufacturing plants (including refineries and petrochemical plants).

In some embodiments of the fourth, fifth and sixth aspects of the present invention, the compound may comprise the reaction product of reactants consisting essentially, or consisting of, an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.

Any feature of any aspect of any invention or embodiment described herein may be combined with any aspect of any other invention or embodiment described herein mutatis mutandis. For example, suitable features of the metallic equipment and the compound in the fourth, fifth and sixth aspects are as defined for the first, second and third aspects.

For example, in the fourth, fifth and sixth aspects, when the compound comprises (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof, suitable alkali metal salts of an optionally substituted polycarboxylic acid or an anhydride thereof include sodium salts and potassium salts (preferably sodium salts). Suitable amines used to form the salt of an optionally substituted polycarboxylic acid or an anhydride thereof include ammonia, primary, secondary and tertiary amines and quaternary ammonium compounds as discussed above in relation to the first, second and third aspects.

For example, in the fourth, fifth and sixth aspects, when the compound comprises (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, the optionally substituted polycarboxylic acid or anhydride thereof, the polyhydric alcohol and the secondary amine are suitably as discussed above in relation to the first, second and third aspects. Additionally, when the compound comprises a salt of (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, the salt is suitably as discussed above in relation to the first, second and third aspects.

For example, in some embodiments, in the fourth, fifth and sixth aspects, a suitable polyhydric alcohol for use to form the reaction product may have from 2 to 4 hydroxy groups and/or from 1 to 40 carbon atoms, such as from 6 to 30 carbon atoms, for example from 6 to 20 carbon atoms. Suitably the polyhydric alcohol comprises an alkylene glycol or a polyalkylene glycol (preferably a polyalkylene glycol). Suitable alkylene and polyalkylene glycols are as discussed above in relation to the first, second and third aspects.

In some embodiments, in the fourth, fifth and sixth aspects, the salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol is suitably an alkali metal salt, preferably a sodium or potassium salt, more preferably a sodium salt For example, in some embodiments, in the fourth, fifth and sixth aspects, a suitable amine for use to form the reaction product may comprise a primary or secondary amine as discussed above in relation to the first, second and third aspects. The amine may be an alkylamine, a hydroxyalkylamine, a dialkylamine, a hydroxyalkyl alkyl amine, or a dihydroxyalkylamine, as discussed above in relation to the first, second and third aspects.

In some embodiments, in the fourth, fifth and sixth aspects, the salt of the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an amine is suitably an alkali metal salt, preferably a sodium or potassium salt, more preferably a sodium salt.

The compounds (i) and (ii) of all aspects of the present invention are suitably biodegradable in the condifions used and/or have a lower aquatic toxicity than known corrosion inhibitors, such as imidazolines.

Brief Description of the Drawings

For a better understanding of the invention, and to show how exemplary embodiments of the same may be carried into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which: Figure 1 shows the results of a Linear Polarisation Resistance (LPR) Test according to Example (showing results for Examples 1, 3, 4 and 5).

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

Examples

Products of Examples 1 to 29 were characterised by IR using a Thermo Scientific Nicolet iS5 FT-IT spectrometer with an iD7 diamond ATR crystal accessory. Persons skilled in the art would recognise that the reactions of the Examples may form reaction products that comprise mixtures of reaction products, as well as unreacted reactants and/or by-products.

Example 1 -Preparation of sodium PEG200 2-octen-1-ylsuccinate 10.0g (1.0 eq) 2-octen-1-ylsuccinic anhydride (mixture of isomers) was dissolved in 100m1 toluene. 9.5 g (1 eq) PEG200" was added and refluxed at 110°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in deionised (D1) water (19.0 g, 1 eq) was added and stirred for 30 minutes. The aqueous layer was separated and deionised water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2923, 2871, 1731, 1442, 1123, 1065 cm-1 IR sodium salt -3382, 1728, 1649, 1568, 1398, 1098 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

*PEG200 is a polyethylene glycol having an average molecular weight of 200.

Example 2 -Preparation of dodecenylsuccinate PEG600 bis ester 25.0 g (1 eq) dodecenylsuccinic anhydride (mixture of isomers) and 28.2 g (0.5 eq) of PEG600" were heated to 95°C for 4 hours. The product was formed as a viscous, orange oil.

IR -2955, 2869, 1732, 1456, 1098 cm-1 The product is believed to comprise a mixture of reaction products, primarily the bis ester compound with some mono ester compound also present.

*PEG600 is a polyethylene glycol having an average molecular weight of 600.

Example 3 -Preparation of dodecenyl succinic acid mono triethanolamine salt 10.0g (leq) of dodecenylsuccinic anhydride (mixture of isomers) was refluxed in water (30 mt) for 4 hours. The reaction mixture was cooled to room temperature, then and triethanolamine (TEA) (5.6 g, 1 eq) was added and stirred for 1 hour. The reaction mixture was diluted with deionised water to a concentration of 25 wt% product in D1 water.

IR -2957, 2929, 2872, 1704, 1424, 1231 cm-1 Example 4-Preparation of sodium diethanolamine dodecenylsuccinamide 10.0 g (1 eq) dodecenylsuccinic anhydride (DDSA, mixture of isomers) was dissolved in 100m1 toluene. 4.0 g (1 eq) diethanolamine was added and refluxed at 110°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (15.2g. 1 eq) was added and stirred for 30 minutes. The aqueous layer was separated and diluted with deionised water to give a 25 wt% solution (as the sodium salt).

IR acid ester -2956, 2929, 2871, 1732, 1621, 1563, 1454, 1379, 1161, 1066 cm-1 IR sodium salt -3323, 2956, 2929, 2871, 1722, 1614, 1564, 1397, 1049 The product is believed to comprise a mixture of reaction products, primarily the diethanolamine compound with some ester compounds (due to reaction of the hydroxy group on the diethanolamine) also present.

Example 5 -Preparation of disodium 2-octen-1-ylsuccinate 10.0 g (1 eq) 2-octen-1-ylsuccinic anhydride (mixture of cis and trans isomers) was dissolved in 100mItoluene and 5mlwater and refluxed for 2 hours. The reaction mixture was cooled to room temperature and 25 wt% NaOH solution in DI water (15.2 g, 2 eq) was added and stirred for 30 minutes. The aqueous layer was separated and diluted with deionised water to give a 25 wt% solution (as the sodium salt).

IR -3344, 1568, 1447, 1407 cm-1 Example 6 -Preparation of sodium PEG600 dodecenyl succinate 4.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.22 g (1.0 eq) PEG600* and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (6.01 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2865, 1720, 1465, 1343, 1244, 1092 cm 1 IR sodium salt -2964, 2873, 1660, 1625, 1464, 1339, 1088 cm 1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

*PEG600 is a polyethylene glycol having an average molecular weight of 600.

Example 7 -Preparation of sodium benzyl amine dodecenyl succinamide 8.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 9.00 g (1.0 eq) benzyl amine and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (12.09, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid amide -2956, 2917, 2865, 1699, 1638, 1538, 1442, 1161 cm-1 IR sodium salt -2955, 2864, 1629, 1547, 1447, 1395, 1304 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono amide compound Example 8 -Preparation of sodium benzyl alcohol dodecenyl succinate 9.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.65 g (1.0 eq) benzyl alcohol and refluxed at 95C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (13.59, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2951, 2920, 2865, 1729, 1694, 1451, 1378, 1144 cm IR sodium salt -2951, 2899, 1707, 1642, 1551, 1447, 1382, 1170 cm 1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound Example 9 -Preparation of sodium 2-ethyl-1,3-hexanediol dodecenyl succinate 7.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.84 g (1.0 eq) 2-ethyl-1,3-hexanediol and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (10.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2980, 2925, 2869, 1729, 1703, 1447, 1369, 1161 cm-I IR sodium salt -2959, 2929, 1703, 1634, 1555, 1464, 1391, 1165 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

Example 10-Preparation of sodium 1-hexanol dodecenyl succinate 10.0 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.84 g (1.0 eq) 1-hexanol and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (15.0 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2959, 2925, 2864, 1729, 1694, 1456, 1369, 1157 cm-1 IR sodium salt -2959, 2925, 1711, 1638, 1555, 1464, 1391, 1165 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

Example 11 -Preparation of sodium PEG1000 dodecenyl succinate 3.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 11.3 g (1.0 eq) PEG1000" and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (4.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2877, 1729, 1447, 1334, 1226, 1092 cm-1 IR sodium salt -2946, 2903, 1638, 1555, 1456, 1348, 1243, 1079 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

*PEG1000 is a polyethylene glycol having an average molecular weight of 1000.

Example 12-Preparation of sodium propylamine dodecenyl succinamide 11.0 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 2.44 g (1.0 eq) propylamine and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (16.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid amide -2959, 2925, 2860, 1698, 1629, 1547, 1460, 1165 cm-1 IR sodium salt -2964, 2894, 1625, 1543, 1456, 1395, 1252 cm 1 The product is believed to comprise a mixture of reaction products, primarily the mono amide compound.

Example 13 -Preparation of sodium 3-climethylaminopropylamine dodecenyl succinamide 8.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.07 g (1.0 eq) 3-dimethylaminopropylamine and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (12.0 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid amide -2955, 2916, 2860, 1698, 1642, 1534, 1451, 1369 cm-1 IR sodium salt -2968, 2894, 1625, 1542, 1464, 1394, 1256 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono amide compound.

Example 14 -Preparation of sodium n-propanol dodecenyl succinate 6.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 1.35 g (1.0 eq) n-propanol and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (9.01 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2959, 2929, 2869, 1733, 1703, 1456, 1369, 1165 cm-1 IR sodium salt -2964, 2873, 1642, 1360, 1460, 1391, 1308, 1170 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

Example 15 -Preparation of sodium 1,6-hexanediol dodecenyl succinate 8.00 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.55 g (1.0 eq) 1,6-hexanediol and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (12.0 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2955, 2917, 2852, 1784, 1698, 1451, 1148 cm-1 IR sodium salt -2968, 2938, 1642, 1551, 1452, 1387, 1304, 1166 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

Example 16-Preparation of sodium PEG200 dodecenyl succinate bis ester 9.00 g (2.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 3.38 g (1.0 eq) PEG200* and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (13.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2947, 2912, 2860, 1724, 1452, 1369, 1239, 1092 cm 1 IR sodium salt -2964, 2882, 1642, 1547, 1456, 1395, 1269, 1066 cm 1 The product is believed to comprise a mixture of reaction products, primarily the bis ester compound with some mono ester compound also present.

*PEG200 is a polyethylene glycol having an average molecular weight of 200.

Example 17 -Preparation of sodium PPG 425 dodecenyl succinate 7.58 g (1.0 eq) dodecenyl succinic anhydride (mixture of isomers) was combined with 12.1 g (1.0 eq) PPG425* and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (11.3 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2960, 2920, 2856, 1863, 1772. 1739, 1447, 1366, 1066 cm-1 IR sodium salt -2985, 2877, 1638, 1543, 1456, 1404, 1369, 1075 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

*PPG425 is a polypropylene glycol having an average molecular weight of 425.

Example 18-Preparation of sodium 1-octanol citrate 8.00 g (1.0 eq) citric acid was combined with 5.42 g (1.0 eq) 1-octanol and refluxed at 140°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (16.66 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2937, 2920, 2851, 1789, 1711, 1395, 1166 cm -1 IR sodium salt -2925, 2851, 1725, 1633, 1569, 1460, 1395, 1200 cm 1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some di ester compound also present.

Example 19-Preparation of sodium 1-octanol iminodiacetate 6.00 g (1.0 eq) iminodiacetic acid was combined with 5.87 g (1.0 eq) 1-octanol and refluxed at 140°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (18.03 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2944, 2921, 2847, 1629, 1386, 1048 cm-1 IR sodium salt -1625, 1582, 1382, 1308, 1222, 1144 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

Example 20 -Preparation of sodium 2-ethylhexanol itaconate 6.00 g (1.0 eq) itaconic acid was combined with 6.01 g (1.0 eq) 2-ethylhexanol and refluxed at 140°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (18.45 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2955, 2921, 2856, 1733, 1690, 1625, 1442, 1148 cm-1 IR sodium salt -2969, 2873, 1635, 1551, 1460, 1386, 1334, 1174 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

Example 21 -Preparation of potassium PEG200 2-octen-1-ylsuccinate 6.009 (1.0 eq) 2-octen-1-ylsuccinic anhydride was combined with 5.71 g (1.0 eq) PEG200" and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% KOH solution in DI water (16.0 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the potassium salt).

IR potassium salt -2933, 2881, 1707, 1629, 1555, 1460, 1395, 1092 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

*PEG200 is a polyethylene glycol having an average molecular weight of 200.

Example 22-Preparation of triethanolamine PEG200 2-octen-1-ylsuccinate 6.00 g (1.0 eq) 2-octen-1-ylsuccinic anhydride was combined with 5.71 g (1.0 eq) PEG200" and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% triethanolamine solution in DI water (42.6 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the triethanolamine salt).

IR triethanolamine salt -2955, 2907, 1716, 1633, 1564, 1443, 1404, 1096 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

*PEG200 is a polyethylene glycol having an average molecular weight of 200.

Example 23-Preparation of sodium 1-octylamine maleamide 5.00 g (1.0 eq) maleic anhydride was combined with 6.59 g (1.0 eq) 1-octylamine and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (20.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid amide-2908, 2840, 1702, 1540, 1443, 1354, 1301, 1079 cm-1 IR sodium salt -2920, 2851, 1629, 1560, 1460, 1430, 1308, 1191 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono amide compound Example 24 -Preparation of sodium N-butyldiethanolamine sebacate 6.00 g (1.0 eq) sebacic acid was combined with 4.78 g (1.0 eq) N-butyldiethanolamine and refluxed at 95°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (20.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2920, 2847, 1711, 1547, 1443, 1386, 1200, 1079 cm 1 IR sodium salt -2938, 2864, 1633, 1538, 1445, 1404, 1304, 1074 cm 1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

Example 25 -Preparation of sodium octylamine phthalamide 6.00 g (1.0 eq) phthalic anhydride was combined with 5.24 g (1.0 eq) octylamine and refluxed at 120°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (16.2 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product.

IR acid amide-2917, 2849, 1726, 1702, 1459, 1201, 1160 CRI1 IR sodium salt -2925, 2852, 1625, 1551, 1378, 1317, 1083 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono amide 25 compound.

Example 26 -Preparation of sodium dodecanol phthalate 5.00 g (1.0 eq) phthalic anhydride was combined with 6.29 g (1.0 eq) dodecanol and refluxed at 120°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (13.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product.

IR acid ester -2912, 2849, 1738, 1687, 1571, 1449, 1414, 1275, 1248, 1106 cm -1 IR sodium salt -2921, 2843, 1634, 1555, 1391, 1278, 1131, 1075 cm -1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

Example 27 -Preparation of sodium 2-ethylhexanol 3,3'-thiodipropanoate 6.009 (1.0 eq) 3,3'-thiodipropanoic acid was combined with 4.389 (1.0 eq) 2-ethylhexanol and refluxed at 120°C for 2 hours. The reaction mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (13.5 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2957, 2928, 2859, 1725, 1698, 1687, 1417, 1337, 1253, 1198. 919 cm 1 IR sodium salt -2955, 2925, 2852, 1729, 1456, 1235, 1165, 1005 cm 1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound.

Example 28-Preparation of sodium furfuryl alcohol dodecenyl succinic anhydride 8.509 (1.0 eq) dodecenyl succinic anhydride was combined with 3.139 (1.0 eq) Furfuryl alcohol and refluxed at 95°C for 2 hours. The reactions mixture was cooled to room temperature and 10 wt% NaOH solution in DI water (12.8 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2955, 2916, 2855, 1742, 1703, 1410, 1161 CrI1-1 IR sodium salt -2955, 2920, 1623, 1551, 1386, 1291, 1165 cm-1 The product is believed to comprise a mixture of reaction products, primarily the mono ester 25 compound.

Example 29 -Preparation of sodium PEG200 dodecenyl succinic anhydride 25.0 g (1.0 eq) dodecenyl succinic anhydride was combined with 18.8 g (1.0 eq) PEG200 and refluxed at 120°C for 2 hours. The reactions mixture was cooled to room temperature and 33 wt% NaOH solution in DI water (11.3 g, 1 eq) was added and stirred for 30 minutes. DI water was added to give a 25 wt% solution product (as the sodium salt).

IR acid ester -2956, 2928, 2871, 1732, 1456, 1248, 1124, 1066 cm 1 IR sodium salt -2951, 2890, 1644, 1551, 1451, 1391, 1083 cm -1 The product is believed to comprise a mixture of reaction products, primarily the mono ester compound with some bis ester compound also present.

*PEG200 is a Polyethylene glycol having an average molecular weight of 200 Example 30 -Linear Polarisation Resistance (LPR) Test The LPR test is used to determine the rate of corrosion of a sample by looking at the system's corrosion resistance. It can be used to simulate an environment not containing a pure water and thus may be used to approximate for oilfield conditions. The LPR test was used to determine how well selected compounds from Examples 1 to 29 perform as corrosion inhibitors in a brine as compared to the commercially available corrosion inhibitor imidazoline.

Method A brine having the composition shown in Table 2 (referred to as brine composition 1) and a brine having the composition shown in Table 3 (referred to as brine composition 2) was made by dissolving the required amount of various analytical grade inorganic salts in deionised water.

Each cell was charged with the desired volume of brine composition 1 or 2 (1 L). Every cell had a stirring bar, reference electrode, counter electrode, and gas sparge tube. The cells were placed in a water bath set at 65°C and set to stir at a slow speed. Each cell was connected to a constant sparge of CO2 and then left for at least 1 hour to reach equilibrium.

C1018 mild steel coupons were polished with 600 grit sandpaper and washed with toluene and iso-propanol to remove any residual grease and allowed to dry. After the cells reached equilibrium, the mild steel coupons were connected to the working electrodes and inserted into each cell. The LPR run was started and baseline corrosion data was collected for approximately 4 hours.

After the baseline corrosion data was collected the corrosion inhibitors were injected, using a micropipette, a compound selected from one of Examples 1 to 29 was injected into the cells and the corrosion rate in each cell was recorded for at least a further 16 hours. The compound was injected as one addition of 40 ppm or as four additions each of 10 ppm.

A summary of the conditions for the LPR test is shown in Table 1.

Table 1

Condition Description

Temperature 60°C Gas Sparge Constant CO2 Working electrode C1018 Mild steel Reference electrode Ag/AgCI (saturated in KC1) Counter graphite electrode Corrosion inhibitor products injected at 40 ppm of the product Test period See table 4 Test fluid Synthetic brine -composition in table 2 Table 2 -Synthetic brine composition 1 Na+ (mg/L) 1685 Kt (mg/L) 1587 rvlg2+ (mg/L) 39 Ca2+ (mg/L) 138.5 Ba2+ (mWL) 8,5 Ee2-p (mg/L) L95 0-(mg/1) 2400 504 2-(mg/L) 1815 HCO3-(mg/L) 1425 Cal. TDS (mg/1) 7403 Table 3 -Synthetic brine composition 2 Ion Conc. (ng/L) *i* 138.5 1687 0 Mg (SO4) Fe2 (SO4) 0 Fe2.+ (C12) HCO3 st4' 0 The corrosion rate of the mild steel coupons was calculated using the equation shown below. CR =

Where: CR = the corrosion rate, units are given by the choice of K (see Table 4 below) Icorr = the corrosion current in amps K = a constant that defines the units for the corrosion rate (shown in Table 4) EVV = Atomic weight/ number of electrons transferred per molecule or atom of material.

d = density in grams/cm3 A = sample area in cm2 LPR was used to calculate loor, as follows.

The LPR technique uses a potentiostat to apply very small changes in potential to the metal/alloy sample -at a point around the metals equilibrium potential, known as the open circuit potential E00 -in both the anodic direction and cathodic direction. This change in potential will result in a change in current -for both cathodic and anodic reactions -the values of which can be plotted in a graph of potential versus current. By extrapolating from the linear parts of the cathodic curve and anodic curve, it is possible to find the point at which these lines intersect. By further extrapolation from this point to both the Y axis, the potential; and, the x axis, the current, it is possible to find both ECOrr and ICOrr.

The results of the LPR test using compounds of selected Examples are shown in Figure 1. A summary of these test results, together with further results, is provided in Table 5.

Table 5

Corrosion inhibitor Brine Dose2 (ppm) Time (hr) Corrosion rate (mmpy) Corrosion Composition protection (0/0) Example 1 1 0 4.1 4.15 99 20.1 0.03 Example 3 1 0 4.1 4.35 99 Mm/(amp-cm-year) mm/year (mmpy) Units Corrosion Rate Units milli-inches/year (mpy) 1.288x105 Milli-inches(amp-cm-year) 0.040A0 e Oonst Tab 20.1 0.03 Example 4 1 0 3.9 4.06 99 19.9 0.06 Example 5 1 0 4.0 4.35 89 20.0 0.46 Example 8 2 0 4.0 3.32 96 20.3 0.14 Example 9 2 0 21.3 4.08 51 35.8 2.02 Example 10 2 0 4.0 3.42 92 22.5 0.29 Example 13 2 0 3.2 3.22 46 40* 25.3 1.73 Example 15 2 0 4.0 3.16 41 40" 28.8 1.68 Example 16 2 0 4.8 3.58 99 22.5 0.05 Example 17 2 0 4.8 3.71 98 22.5 0.09 Example 21 2 0 3.9 5.45 59 40* 28.1 2.24 Example 22 2 0 3.9 4.93 68 28.2 2.44 Example 26 2 0 4.0 3.57 99 20.3 0.04 20.0 2.80 Example 28 2 0 4.0 3.75 99 22.5 0.04 Example 29 2 0 4.0 3.94 94 25 0.25 Comparative example' 1 0 4.0 4.43 37 20.0 2.80 1The comparative example is a commercial tall oil aminoethyl imidazole based corrosion inhibitor.

2The active dose of the corrosion inhibitor depends on the concentration of the product. If the dose of the product is 40 ppm and the corrosion inhibitor has a concentration of 25 wt% in the product, the active dose is 10 ppm. All 40 ppm doses were injected as one addition of 40 ppm except for those marked with " which were dosed as four additions each of 10 ppm.

Corrosion protection was calculated as: ([Corrosion rate before addition of corrosion inhibitor -corrosion rate at 20 hours] x 100)/ Corrosion rate before addition of corrosion inhibitor The above test results show that compounds according to the present invention are effective as corrosion inhibitors. Some of the compounds tested were far more effective than the imidazole-based comparative example.

Example 31

The LPR test was carried out using the corrosion inhibitor of Example 1. The LPR test was carried out using the same conditions as the LPR test of Example 30 except for the composition of the corrosive fluid, the temperature, and the dose of the corrosion inhibitor. These differences, together with the results of the test, are shown in Table 7. The brine compositions used are shown in Table 6.

Table 6

Ion Brine Composition 1 2 3 4 5 6 Na+ 4199.2649 16339.239 27766 14816 42790 47946 Mg2 756.4 2026 1353 78.32 617.25 144.86 Ca2* 360.7 1887 6755 471.1 7183 997.07 K. 91.7 433 392.82 197.85 187.52 887.75 Sr 2+ 8.26 41 651.89 179.02 1052 121.49 Ba2+ 0.1 1.5 6.08 1.16 25.95 0.42 Zn2+ 0 0 12.23 0 7.14 0 Mg2' 0 0 0 0 0 0 Fe2+ 0 0 37.74 5.64 85.98 39.33 Fe3* 0 0 0 0 0 0 HCO3- 219.6 642 220 671 329 12 C032- 0 0 0 0 0 0 S042- 3260 4000 88 240 204 1550 Cl- 8078 33019 58500 23600 80000 76000 TDS 16974 58389 101382 41514 138701 135204

Table 7

Test Corrosive fluid Temperature (°C) Dose (ppm) Time (hours) Corrosion rate Corrosion protection (%) (rnmPY) 1 Brine 60 0 2 3.6090 96 composition 1 4 0.1320 2 Brine 60 0 2 4.0170 96 composition 2 4 0.1693 4 0.8889 3 Brine composition 3 and depolarised kerosene 90:10 volume ratio 82 0 1 2.7178 99 5 0.0358 4 Brine composition 4 and depolarised kerosene 90:10 volume ratio 82 0 1 3.7846 98 5 0.0833 Brine composition 5 and depolarised kerosene 90:10 volume ratio 82 0 1 3.2004 96 5 0.1387 6 Brine composition 6 and depolarised kerosene 90:10 volume ratio 82 0 1 3.4798 95 5 0.1646 These results show that the compound of Example 1 was an effective corrosion inhibitor in a variety of brines and brine/hydrocarbon emulsions.

The present invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

Claims 1. The use of a compound as a corrosion inhibitor for metallic equipment, wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (H) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.
2. A method of preventing or reducing corrosion of metallic equipment, the method comprising contacting at least a portion of the metallic equipment with a compound (for example by introducing a compound into the metallic equipment), wherein the compound comprises (i) a salt of an optionally substituted polycarboxylic acid or an ahydride thereof; and/or OD the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product.
3. A use or method according to claim 1 or 2, wherein the optionally substituted polycarboxylic acid or the anhydride thereof comprises an optionally substituted succinic acid or an optionally substituted succinic anhydride.
4. A use or method according to any preceding claim, wherein the optionally substituted polycarboxylic acid or the anhydride thereof is substituted with an alkyl, alkenyl, alkaryl or aralkyl group.
5. A use or method according to claim 4, wherein the alkyl or alkenyl group has from 2 to 30 carbon atoms, such as from 4 to 22 carbon atoms, for example from 6 to 18 carbon atoms.
6. A use or method according to any preceding claim, wherein the salt of the optionally substituted polycarboxylic acid or the anhydride thereof or the salt of the reaction product comprises an alkali metal salt and/or an amine salt.
7. A use or method according to claim 6, wherein the amine salt comprises a tertiary amine salt.
8. A use or method according to any preceding claim, wherein the compound comprises a di alkali metal salt of a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof
9. A use of method according to any preceding claim, wherein the compound comprises a mono amine salt of a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof.
10. A use or method according to any preceding claim, wherein the alcohol comprises a polyalkylene glycol
11. A use or method according to claim 10, wherein the polyalkylene glycol comprises polyethylene glycol having a number average molecular weight of from 60 to 370 or from 400 to 950.
12. A use or method according to any preceding claim, wherein the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a polyethylene glycol, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of from 1.5:1 to 1:1.5.
13. A use or method according to any preceding claim, wherein the compound comprises the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a polyethylene glycol, wherein the acid/anhydride and the polyethylene glycol are reacted in a molar ratio of from 1.5:1 to 2.5:1.
14. A use or method according to any preceding claim, wherein the amine comprises a primary or secondary amine.
15. A use or method according any preceding claim, wherein the amine is substituted with at least one hydroxyalkyl group.
16. A use or method according to any preceding claim, wherein the compound comprises a salt of the reaction product of reactants comprising a hydrocarbyl substituted dicarboxylic acid or an anhydride thereof and a dihydroxyalkylamine, wherein the acid/anhydride and the dihydroxyalkylamine are reacted in a molar ratio of from 1.5:1 to 1:1.5.
17. A use or method according to any preceding claim, wherein the compound comprises a compound of formula I: wherein (I) X is a linking group; R1 is 0-M+, O(R30)R4, or NR5R6; and R2 is OH, 0-W, 0(R30),R4, or NR5R6; wherein each At is independently a cation; each R3 is independently an optionally substituted alkylene group; each R4 is independently hydrogen or an optionally substituted hydrocarbyl group; each R5 is independently hydrogen or an optionally substituted hydrocarbyl group; each R6 is independently an optionally substituted hydrocarbyl group; each n is independently 0 or a positive integer, provided that n is not 0 when R4 is hydrogen.
18. A use or method according to claim 17, wherein X is CH2CHR or CHRCH2 wherein R is an optionally substituted hydrocarbyl group.
19. A use or method according to any preceding claim, wherein the metallic equipment ismetallic oilfield equipment.
20. A use or method according to any preceding claim, wherein the metallic equipment is selected from metallic pipelines and temperature control jackets.
21. A use or method according to any preceding claim, wherein a surface of the metallic equipment is, or will be, in contact with a corrosive fluid.
22. A use or method according to claim 21, wherein the corrosive fluid comprises an aqueous fluid, such as brine.
23. A use or method according to claim 21 or 22, wherein the corrosive fluid comprises a fluid produced from an oil or gas well.
24. A method according to any one of claims 21 to 23, wherein the method comprises applying the compound to at least a portion of a surface of the metallic equipment and/or adding the compound to the corrosive fluid.
25. A composition for inhibiting the corrosion of metallic equipment, the composition comprising: (a) a compound comprising (i) a salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and an alcohol and/or an amine, or a salt of the reaction product; and (b) an additive selected from corrosion inhibitors other than compound (a), proppant particulates, fracturing fluids, acids, fluid loss control additives, biocides, surfactants, scale inhibitors, clay control additives, foamers (optionally accompanied with gasses such as air, natural gas, N2 or CO2 to form a foam), paraffin inhibitors, gelling agents, pH adjustment additives, buffers, cross-linkers, oxidizing agents, enzymes, oxygen scavengers, hydrogen sulfide scavengers, friction reducers, passivation agents (for example phosphate ester passivation agents), gel degrading agents and additives to control gas hydrate formation.
26. The use of a compound as a corrosion inhibitor, wherein the compound comprises (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.
27. A method of preventing or reducing corrosion of a metallic surface, the method comprising contacting at least a portion of the metallic surface with a compound comprising (i) an alkali metal or amine salt of an optionally substituted polycarboxylic acid or an anhydride thereof; and/or (ii) the reaction product of reactants comprising an optionally substituted polycarboxylic acid or an anhydride thereof and a polyhydric alcohol and/or a secondary amine, or a salt of the reaction product.