WO2018001629A1

WO2018001629A1 - Synergized acetals composition and method for scavenging sulfides and mercaptans

Info

Publication number: WO2018001629A1
Application number: PCT/EP2017/061827
Authority: WO
Inventors: Antonio Pedro De Oliveira Filho; Jonathan Wylde; Alina KINA; Grahame Taylor
Original assignee: Clariant International Ltd; Clariant S. A.
Priority date: 2016-07-01
Filing date: 2017-05-17
Publication date: 2018-01-04
Also published as: AR124398A2; AR108933A1

Abstract

This invention provides a composition comprising at least one reaction product between a mono- or polyhydric alcohol and an aldehyde or ketone, and II. at least one solvent, and IV. at least one compound of formula (1) wherein R²⁰ is H or C₁ to C₃ alkyl R is H or C₁ to C₃ alkyl n is an integer from 1 to 5, the components I, II and IV being different from each other.

Description

Synergized Acetals Composition And Method For Scavenging Sulfides And Mercaptans

The invention relates to a process for scavenging hydrogen sulfide from liquids and/or gas by using acetal in combination with a synergist, a solvent and optionally an emulsion breaker. The formulations containing the inventive composition have particular applicability in scavenging hydrogen sulfide and/or mercaptans yet at the same time prevent the formation of unwanted emulsions and/or deposition of unwanted by products often associated with using chemistries and/or formulations of the prior art.

The presence of sulfhydryl compounds and particularly hydrogen sulfide pose challenges in many industries. Their presence can create a significant health, safety and environmental challenge. There are many different types of sulfhydryl compounds, but the most commonly encountered molecules include hydrogen sulfide (H2S), organo-sulfur compounds containing S-H groups (also called mercaptans), thiol carboxylic acids RC(0)SH, dithio acids RC(S)SH, and related compounds. In the oil and gas industry the H2S content of crude oil and natural gas in many areas of the world is high enough to present environmental and safety hazards. Hydrogen sulfide is a flammable, corrosive, and highly toxic gas. H2S is the most reduced form of sulfur and is produced by sulfate reducing bacteria (SRB) that are often found in anaerobic oilfield environments, or caused by thermal cracking and thermochemical sulfate reduction (TSR) by hydrocarbons. As oil is produced, it is depressurized and dissolved H2S is released and can then be transferred to, for example, oil based drilling fluid during the drilling process and this can become a hazard as the drilling fluid is recirculated from the well to the surface. During the production phase H2S gas can create a significant integrity risk where it is present at as little as 0.01 psig partial pressure as it is an acid gas and upon dissolving into produced water creates a very corrosive environment. In addition, the presence of H2S increases the risk of hydrogen embrittlement of some structural materials and requires to be removed in order for fluids to be safely processed. The odor of sulfhydryl compounds is also a challenge in, for example, metal working environments, but equally in water treatment processes, either municipal (e.g. waste water treatment) or industrial (recycling of mining water). SRB are often present in the recirculating fluid systems, and though the bacteria can usually be controlled by the use of biocidal compositions, it is easy to lose control of the biology in the system which results in the production of hazardous H2S in the system. Furthermore biocides are inefficient at removing H2S after it forms and only anecdotally scavenge, via either oxidation (e.g. sodium hypochlorite application) or due to the release of low levels of aldehyde during their breakdown (e.g. with glutaraldehyde). Sulfhydryl compounds and particularly H2S can present environmental, toxicity and integrity challenges in gaseous phases in confined spaces, as for instance in sewage treatment facilities and particularly in shipping and storage containers for moisture sensitive materials that may emit H2S which can sit in the gaseous headspace. It would be desirable to have a scavenger that could reduce the H2S concentrations in such locations. It would be particularly advantageous to have such a scavenger that is active in the absence of an aqueous phase. Furthermore it is desirable to have a scavenger that does not , produce unwanted by-products or form emulsions that can inadvertently contaminate the very systems they are treating.

A number of methods have been proposed to scavenge hydrogen sulfide and control sulfhydryl odors in hydrocarbon containing systems: WO-98/02501 describes the use of 3,3'-methylene-bis-5-methyloxazolidine bisoxazolidines prepared by the reaction of 1 , 2 or 1 , 3 amino alcohols containing 3 to 7 carbon atoms with aldehydes containing 4 or fewer carbon atoms. The relative oil and water solubility of these products can be controlled through the correct choice of starting materials. These bisoxazolidines react with sulfhydryl compounds present in oil and gas streams to neutralize and therefore scavenge them. US-5347004 teaches the use of reaction products of alkoxyalkylene amine, ammonia, and dialkylamines with aldehydes. These products are used to remove H2S from gas streams which are sparged into water solutions of the products. There are multiple patents published in the art that teach the use of triazine chemistry for the control of H2S in the oilfield environment. US-4978512 teaches a method for reducing H2S and organic sulfides from gaseous and/or liquid hydrocarbon streams by using a reaction product of a lower alkanolamine comprising 1 to about 6 carbons with a lower aldehyde comprising 1 to about 4 carbons. A preferred embodiment is the reaction product of monoethanolamine and formaldehyde which is perhaps one of the most ubiquitously used triazine chemistries in the oil and gas industry today to scavenge H2S.

US-5128049 teaches a unique application method for scavenging agents whereby a dilute solution of a scavenging agent, such as triazine, is injected into an H2S containing fluid, followed by equilibration and a second injection of dilute solution of scavenging agent to further reduce the H2S content of the treated fluid.

EP-0636675 teaches the further use of a scavenging compound comprising a substantially formaldehyde free 1 ,3,5-trimethyl-hexahydro-1 ,3,5-triazine to scavenge gas or liquid hydrocarbon streams containing H2S and/or mercaptans. The compound described is preferably prepared by the reaction of methylamine and formaldehyde. US-8512449 teaches a method for formulating an oil-soluble triazine sulfide scavenger comprising a liquid sulfide-scavenging composition comprising from about 25 to 80 % by volume of a triazine, from about 15 to 50 % by volume of a glycol ether, and from about 5 to 40 % by volume of an alcohol, with a maximum water content of about 15 % by volume, and being oil soluble. The triazine used is a reaction product of a Ci to C6 alkanolamine and a Ci to C6 aldehyde, where the Ci to C6 moiety in each instance is a straight or branched chain alkyl group. WO-2014/031537 teaches the use of an aldehyde releasing compound, preferably hydantoins, to remove sulfhydryl compounds from hydrocarbon fluids.

US-392821 1 describes the use of inorganic zinc salts (most preferably zinc carbonate) preferably dispersed into aqueous or non aqueous oil well drilling fluids with an organic dispersant such as lignin containing materials.

US-4147212 teaches the use of a water soluble zinc ammonium carbonate complex used to remove hydrogen sulfide from oils and gases by contact with aqueous solutions of the complex.

US-6599472 discloses the use of metal salt carboxylic acids that are soluble in hydrocarbon oils and are used to inactivate odor producing sulfhydryl compounds. Preferred embodiments are zinc neodecanoic acid but equally claimed are carboxylic acids of naphthenic acids, neoacids, isoacids and Guerbet acids and mixtures thereof.

WO-2014/130503 teaches the use of zinc carboxylates, preferably zinc octoate or zinc 2-ethyl hexanoic acid in combination with viscosity improver selected from the group consisting of glycol ethers having from about 4 to about 15 carbon atoms, and/or alkyl alcohols having from about 1 to about 10 carbons, and/or with additional hydrocarbons from about 7 to about 30 carbons. The resultant formulations are used to scavenge hydrogen sulfide gas. WO-2013/181056 teaches the synergistic hydrogen sulfide scavenging obtained when use of a metal salt, preferably selected from zinc chloride, zinc acetate, zinc octanoate, and zinc salts containing at least one hydrocarbyl group of at least 4 carbon atoms in combination with an oil soluble amine formaldehyde reaction product (triazine).

WO-2002/051968 teaches a process for reducing the level of hydrogen sulphide in a liquid or gas by treatment of the liquid or gas with an H2S-scavenger product derivable by the reaction of a carbonyl group-containing compound with an alcohol, thiol, amide, thioamide, urea or thiourea. The carbonyl group-containing compound is preferably formaldehyde, and preferably the product is derivable by reaction of formaldehyde with an amine-free alcohol or urea selected from ethylene glycol, propylene glycol, glycerol, diethylene glycol, triethylene glycol, ethyl alcohol, n-butanol, a sugar, a low molecular weight polyvinyl alcohol, castor oil fatty acid and urea. More especially, the scavenger product is used with an amine, especially monoethanolamine.

US-2015/0025258 discloses the use of particulate zinc oxide salts blended in a mixture of two or more carboxylic acids selected from the group consisting of acetic acid, oleic acid, isobutyric acid, lineoleic acid and neodecanoic acid, for the scavenging of hydrogen sulfide.

The object of this invention is to provide formulations which can be used for scavenging of sulfhydryl compounds in crude oil, gas production, water production, water injection and combinations thereof, preferably, but not limited to, H2S and/or mercaptans. The formulations of the invention should have particular applicability in scavenging sulfhydryl compounds and should be notable for improved

performance compared to the formulations and chemistries of the prior art.

It has been found that the composition comprising at least one reaction product between a mono- or polyhydric alcohol and an aldehyde or ketone ("acetal") combined with a synergist, optionally an emulsion breaker, and a solvent comes to overcome the very slow kinetics of scavenging H2S provided by acetals alone. The use of the inventive synergist component enables acetal to much more efficiently react with H2S. The mechanism believed to be involved in this reaction, but should not be considered to be limiting to the invention in any way, occurs due to the likelihood that the synergist component reacting preferentially with H2S releasing an intermediate reaction complex which then in turn react with a molecule of acetal generating a new molecule of synergist and the corresponding alcohol present in the acetal. After the H2S scavenging, and after all the acetal is consumed, the residual synergist then works as a corrosion inhibitor, protecting the integrity of the pipelines and equipment in which it has been applied. In a first aspect of the invention, there is provided a composition comprising

I. at least one reaction product between a mono- or polyhydric alcohol and an aldehyde or ketone, and at least one solvent, and at least one compound of formula (1)

wherein

R²⁰ is H or Ci to C₆ alkyl

R is H or Ci to Ce alkyl

n is 1 or 2.

In a second aspect of the invention, there is provided the use of the composition of the first aspect as a sulfhydryl scavenger for application in oilfield operations and process systems.

In a third aspect of the invention, there is provided a process for scavenging sulfhydryl compounds in oilfield operations and process systems, the process comprising adding to a system susceptible to production of sulfhydryl compounds the composition of the first aspect. In a fourth aspect of the invention there is provided the use of a compound of formula (1)

wherein

R²⁰ is H or Ci to Ce alkyl

R is H or Ci to Ce alkyl

n is 1 or 2, as a synergist for the reaction between

a) the reaction product of a mono- or polyhydric alcohol with an aldehyde or ketone, and

b) a sulfhydryl compound.

In a preferred embodiment of the invention, at least one demulsifier is present in any aspect of the invention. The components I, II and IV are different from each other.

Group 1

The group 1 compound is the reaction product of an alcohol and an aldehyde or ketone. Especially preferred are aldehydes. In a preferred embodiment, the reaction product is a hemi-acetal.

An aldehyde or ketone starting material may contain one or more carbonyl groups, especially one or two carbonyl groups, and comprises aliphatic, alicyclic and/or aromatic moieties, usually aliphatic, alicyclic and/or aromatic hydrocarbon moieties or hydrogen. More especially the compound is aliphatic or cycloaliphatic or contains both aliphatic and cycloaliphatic moieties. Aliphatic or cycloaliphatic groups or moieties may be saturated or unsaturated, but are usually saturated. Preferably there is used an aldehyde or ketone containing 1 to 10 carbon atoms, for example 1 to 7 carbon atoms. Preferably, the carbonyl compound is an aldehyde, more especially a mono- or di-aldehyde, commonly and most preferred formaldehyde. It should be understood that the term "formaldehyde" includes paraformaldehyde, formalin and other chemical forms from which the basic structure HCHO can be derived. Other suitable aldehydes include, for example, glyoxal, acetaldehyde, propionaldehyde, butyraldehyde and glutaraldehyde. Suitable ketones include, for example, acetone, methyl ethyl ketone, methyl isopropyl ketone, and hexanones and heptanones having a total of 6 or 7 carbon atoms respectively. The expression "acetal" as used herein shall refer to the reaction product of any alcohol and any aldehyde or ketone. It means the reaction products of formaldehyde, i.e. formals, as well.

Mixtures of two or more carbonyl compounds, for example two or more of the aldehydes mentioned above, e.g. formaldehyde and one or more other aldehydes, may be used if desired.

An alcohol starting material contains one or more hydroxy groups. The alcohol comprises aliphatic, alicyclic and/or aromatic moieties, preferably aliphatic, alicyclic and/or aromatic hydrocarbon moieties, and more especially the compound is aliphatic or cycloaliphatic, or contains both aliphatic and cycloaliphatic moieties. Aliphatic or cycloaliphatic groups or moieties may be saturated or unsaturated, but are usually saturated. More especially the compound is aliphatic. Preferably the alcohol contains, for example, 1 to 6 hydroxy groups and is, for example, ethylene glycol, propylene glycol, glycerol, ethyl alcohol, methanol, n-butanol, a sugar molecule, or a polyvinyl alcohol of low molecular weight such that the reaction product with the carbonyl starting material remains a liquid. The most preferred alcohols are glycerol and ethylene glycol.

In a particularly preferred embodiment the reaction product is a hemi-acetal. Preferred hemi-acetal compounds that can be used as the scavenger are described by the structures below:

wherein

Ri is H or Ci to Cs alkyl, and

R₂ is CH2OH.

HO^^O (CH₂)_p O R₂ (2a) wherein

p ia a number from 2 to 10, and

wherein

R₃ is H, Chb, (CH₂)nCH₃, (CHR^nCHs, CH2OH

n is 1 to 10, and

R₄ is H, Chh, (CH₂)nCH3, (CHR4)nCH₃, CH2OH. (4)

O— (CH₂) wherein

m is 1 to 10, preferably between 1 and 2

The most preferred structures are the ones that derive from either glycerol or ethylene glycol. These are the formulae (3) and (4), or formula (2) wherein Ri is H

In another specific preferred embodiment the hemi-acetal can have the structure below

wherein

R5 is H, CH3, (CH2)zCH3, with the proviso that not all of R5 are hydrogen, z is 1 to 10, and

x is 1 to 5.

Group 2

The solvent may be any solvent suitable, for dissolving or suspending the hemi- acetal components described in Group 1. In preferred embodiments, the solvent is water, alcohol, a non-alcoholic organic solvent, and/or any combination thereof. The alcohol may include any alcohol suitable as a solvent and for use with oil recovery operations. Preferred are alkyl alcohols having from 1 to 10 carbon atoms, e.g. isopropyl alcohol, methanol, ethanol, propanol, butanol. Another preferred type of alcohols is glycols, e.g. ethylene glycol, propylene glycol and butylene glycol. Another preferred type of alcohols is glycol ethers having from 4 to 15 carbon atoms. Examples of suitable glycol ethers include oligoethylene glycols, oligopropylene glycols or any combination thereof. Oligoethylene glycols and oligopropylene glycols as used herein preferably have a number average molecular weight between 200 and 1000 g/mol.

According to another preferred embodiment, the organic solvent includes aromatic compounds, either alone or in any combination with the foregoing. In an embodiment, the aromatic compounds have a molecular weight from about 70 to about 400, preferably from about 00 to about 200 g/mol. In a preferred

embodiment, aromatic hydrocarbon solvents having from 6 to 30 carbon atoms are used. Examples of suitable aromatic compounds include toluene, xylene, naphthalene, ethylbenzene, trimethylbenzene, and aromatic naphtha (AN), other suitable aromatic compounds, and any combination of the foregoing. It is to be understood that the amount of hemiacetal in the composition in relation to the solvent may vary in some embodiments depending upon factors such as temperature, time, and type of hemiacetal. For instance a higher ratio of hemiacetal to solvent may be used if a faster reaction time is desired.

Group 3

The group 3 component is optional. This group comprises emulsion breakers, or demulsifiers or non-emulsifiers. The purpose of having these compounds present is to prevent the formation of emulsions caused by the reaction products of such as iron present in oil mainly because of the corrosion of pipelines and equipment caused by FbS present. Fine solids of iron sulfide stabilize the water present in the oil generating a stable emulsion. The purpose of the demulsifier molecule is to break the oil/water emulsion by creating a preferentially water wet surface on the metal sulfide and also to modify the surface tension at the oil/water interface which is stabilized by the metal sulfides to one allowing coalescence of the emulsion.

In preferred embodiments, the emulsion breaker components refer to components or additives that may be added as part of the composition comprising the instant invention and can be described as polymeric nonionic surfactants. Without limitation, examples of suitable polymeric nonionic surfactants include

polysorbates, fatty alcohols such as cetyl alcohol and oleyl alcohol, polymers comprising ethylene oxide, polymers comprising propylene oxide, ethylene oxide- propylene oxide copoymers, alkyl polyglucosides such as decyl maltoside, alkylphenol polyethylene oxide, alkyl polyethylene oxide, dodecylbenezesulfonic acid, and ethoxylated and/or propoxylated alkyl phenol-formaldehyde resins. In a preferred embodiment, the emulsion breaker is a compound according to the formula (6)

wherein

Rio C2 to C4 alkylene

R11 Ci to C18 alkyl

k a number from 1 to 200

m a number from 1 to 100 is.

In a preferred embodiment R10 is an ethylene or a propylene group. R10 may represent mixtures of different C2 to C₄ alkylene groups, preferably ethylene and propylene groups.

In another preferred embodiment, R11 is a C₄ to C12 alkyl group, more preferably tertiary butyl group or an iso-nonyl group.

In formula (6), R10, R11 and k may be the same in each of the repeating units, or they may differ from unit to unit.

In another preferred embodiment k is a number from 2 to 20.

In another preferred embodiment m is a number from 3 to 20. In another specific preferred embodiment the emulsion breaker is dodecylbenezesulfonic acid

OH

O = S= O

In another preferred embodiment, the demulsifier is a mixture of at least one compound of formula (6) and at least one compound of formula (7). Such mixture preferably contains (6) and (7) in a weight ratio of from 5:1 to 1 :5, more preferably in a weight ratio of from 3:1 to 1 :3.

The polymeric nonionic surfactant is preferably dissolved or suspended in a solvent. Any solvent suitable for dissolving or suspending a polymeric nonionic surfactant may be used. Examples of suitable solvents include water, butylglycol, ethylene glycol, propylene glycol, butylene glycol, oligoethylene glycols, oligopropylene glycols, ethers, alcohols, toluene, xylene, aromatic naphtha, or any combination thereof. The alcohol may include any alcohol suitable for use with oil recovery and for dissolving the polymeric nonionic surfactant and is preferably selected from the group consisting of isopropyl alcohol, methanol, ethanol, propanol, butanol or any combination thereof.

Group 4

This group comprises the synergist component of the formulation. The synergist is a compound according to formula (1)

wherein

R²⁰ is H or Ci to C₆ alkyl

R represents H or a Ci to C6 alkyl group, and

n is 1 or 2.

In a preferred embodiment, R²⁰ is H. In another preferred embodiment, R is H or Chb. In another preferred embodiment, n is 1.

In a particularly preferred embodiment, n is 1 , R²⁰ is H and R is Chb. The name of this compound is 3,3'-methylene-bis-5-methyl-oxazolidine (MBO).

Group 5

In a preferred embodiment corrosion inhibitors may be added to the target system separately and/or in association with the compounds described in group 1 , 2 and 3. The addition of these Group 5 components serves to add corrosion inhibition functionality to the overall product.

The corrosion inhibitor serves to reduce the overall corrosivity of the treatment, protecting the tubulars and production equipment from corrosion caused by oilfield fluids into which the instant invention is deployed. The corrosion inhibitor may also be formed in sites by the constituents of the instant invention together with H2S or other sulfhydryl compounds. The product generated from the reaction with H2S with MBO is a morpholine and it is recognized as a good corrosion inhibitor protecting the integrity of the whole system.

A preferred embodiment of the current invention is to use alkyl dimethyl benzyl ammonium chloride according to formula (8) as a corrosion inhibitor that also provides functionality as an interfacial tension reducer.

wherein

R9 is Cs to C18 alkyl. The composition may additionally contain biocides, for example, formaldehyde or glutaraldehyde, water dispersants, antifoams, oxygen scavengers and/or flocculants. There may also be added to the water to be treated oxygen

scavengers, flocculants such as polyacrylamide dispersants, antifoams such as acetylenic diols, silicones or polyethoxylated antifoams.

In a preferred embodiment, the inventive composition comprises 1 to 95 wt.-% of the hemiacetal described above in group 1 , preferably between 20 and 75 wt.-%.

In a preferred embodiment, the inventive composition comprises 1 to 50 wt.-% of the solvent described above in group 2, preferably between 5 and 25 wt.-%. In a preferred embodiment, the inventive composition comprises 0.1 to 0 wt.-% of at least one emulsion breaker described above in group 3, preferably between 0.5 and 2 wt.-%. In a preferred embodiment, the inventive composition comprises 1 to 20 wt.-% of the synergist described above in Group 4, preferably between 5 and 15 wt.-%.

In a preferred embodiment, the inventive composition comprises 0.1 to 5 wt.-% of the corrosion inhibitor described above in group 5, preferably between 0.2 and 2 wt.-%.

The compositions may in a preferred embodiment comprise water. The water in the composition may be formed during the manufacture of hemi-acetals, or it can be added into the composition to balance the formulation. It can be present in concentration from 1 to 50 wt.-%, preferably between 5 and 15 wt.-%. In another preferred embodiment water is present to balance up to 100 wt.-%.

Furthermore, any balance remaining after addition of components of groups 1 - 4 or groups 1 - 5 described above is preferably made up with water and/or glycol and/or alcohol based solvents. The alcohols and solvents are preferably selected from, but not limited to, methanol, ethanol, propan-1-ol, propan-2-ol, monoethylene glycol, diethylene glycol, triethylene glycol, propylene glycol and / or 2- butoxyethanol. The inventive composition is preferably applied in concentrations between 50 and 35,000 mg/L, preferably between 100 and 30,000 mg/L based on the volume of oil or gas production to a production system where sulfhydryl compounds are present. The exact concentration will preferably depend on the formulation activity itself, the type of sulfhydryl compounds required to be scavenged, static

conditions, materials of construction of the medium being treated, quality of the materials being used to make up the inventive composition, temperature of the system and salinity of the system. At this concentration range, the inventive composition can provide substantial scavenging of sulfhydryl compounds from the produced liquids in order to maintain the flowability of hydrocarbon production and the quality of the hydrocarbon produced product as it is transported to market. In a preferred embodiment the above mentioned concentrations refer to the

concentration of the reaction product between a mono- or polyhydric alcohol and an aldehyde or ketone.

The present invention also includes a process for applications using the compositions above for application to be deployed in scavenging of sulfhydryl compounds present in the drilling and the production cycle, particularly as a component of well work-over, well intervention, production enhancement and flow assurance packages.

The injection fluid containing the composition of the instant invention may additionally contain other ingredients known to those familiar with the art. Such other ingredients include acids, dispersants, viscosifiers, lubricity agents, scale inhibitors, friction reducers, crosslinker, surfactants, scavenger, pH adjuster, iron control agents, breakers; this is especially true if any produced water (or recycled water) is in contact with the compositions of the instant invention. Employing the embodiments of the instant invention improves the scavenging of sulfhydryl compounds while not causing formation of complex and difficult to treat emulsions. Furthermore the embodiments of the instant invention will not corrode the oilfield equipment that it comes into contact with, nor will it allow the deposition of unwanted solids, such as metal sulfide scales, so often found with applications of the prior art. Other applications of the embodiments of the instantaneous invention include treating water for downhole injection for pressure support, treatment of drilling and work-over operations, wettability alteration and well cleanout. Within this specification, percentages are weight percentages unless specified otherwise. EXAMPLES

Example 1 (comp.) - Preparation of MEG-hemi-acetal with active ingredient of

40 % formaldehyde.

In a stirred and heated reactor 490 g of monoethyleneglycol, 100 g of ethanol (100 %) and 5 g of sodium hydroxide solution at 50 wt.-% were charged. This mixture was homogenized for 10 minutes and 430 g of paraformaldehyde

(93 wt.-%) was added over a period of approximately 30 minutes. The reaction mixture was warmed while stirring for 2 hours at a temperature between 80 to 85 °C. After the reaction time, the mixture was cooled to 30 °C, a sample was taken and the total amount of hemiacetal and formaldehyde was determined by using two different methods of analysis: ¹H NMR, to determine the amount of free formaldehyde, by measuring the area below the shift at 9.8 ppm, which is proportional to the total amount of free formaldehyde, and was found to be 0.02 wt.-% of free formaldehyde. The second method of analysis was done by reacting the product with HCI first, then reacting the formaldehyde released in this reaction with 2,4-dinitrophenylhydrazine (DNPH) and finally, after derivation, it was analyzed by using HPLC/UV. The second method of analysis was to determine the total amount of hemiacetal and formaldehyde in the final product, that was higher than 90 wt.-%, and

40 wt.-%, respectively.

Example 2 - Preparation of standard hemi-acetal synergized with 3,3'-methylene- bis-5-methyloxazolidine and active ingredient of 40 % formaldehyde. In a stirred and heated reactor 490 g of monoethyleneglycol, 100 g of ethanol (100 wt.-% ) and 5 g of sodium hydroxide solution at 50 wt.-% were charged. This mixture was homogenized for 10 minutes and 430 g of paraformaldehyde

(93 wt.-%) was added over a period of approximately 30 minutes. The reaction mixture was warmed while stirring for 2 hours to 80 to 85 °C. After the reaction time, the mixture was cooled to 30 °C and, 20 g of 3,3'-methylene-bis-5- methyloxazolidine was added into the mixture. Finally, the mixture was stirred, for another 30 minutes, to be homogenized, then a sample was taken and analyzed regarding the hemiacetal and formaldehyde as described above in Example 1. In the final product a total amount of hemiacetal and formaldehyde higher than 90 wt.-% and 40 wt.-%, respectively were found.

Example 3 (comp.) - Preparation of glycerol hemi-acetal with active ingredient of

40 % as total formaldehyde.

In a stirred and heated reactor 410 g of glycerin, 60 g of monoethyleneglycol, 79 g of ethanol (100 wt.-%) and 5 g of sodium hydroxide solution at 50 wt.-% were charged. This mixture was homogenized for 10 minutes and 430 g of

paraformaldehyde (93 wt.-%) was added over a period of approximately

30 minutes. The reaction mixture was warmed while stirring for 2 hours to 80 to 85 °C. After the reaction time the mixture was cooled to 30 °C, 10 g of emulsion breaker were added and mixed for 15 minutes to be homogenized, then a sample was taken and analyzed regarding the hemiacetal and formaldehyde as described above in Example 1. In the final product a total amount of hemiacetal and formaldehyde higher than 90 wt.-% and 40 wt.-%, respectively were found.

Example 4 - Preparation of the glycerol hemi-acetal synergized with

3,3'-methylene-bis-5-methyloxazolidine and active ingredient of 40 % as formaldehyde.

paraformaldehyde (93 wt.-%) was added over a period of approximately

30 minutes. The reaction mixture was warmed while stirring for 2 hours to 80 to 85 °C, After the reaction time the mixture was cooled to 30 °C. While stirring 20 g of 3,3'-methylenebis-(5-methyloxazolidine) and 10 g of emulsion breaker were added. The mixture was kept under stirring for 15 minutes to be homogenized, then a sample was taken and analyzed regarding the hemiacetal and

formaldehyde as described above in Comparison 1. In the final product a total amount of hemiacetal and formaldehyde higher than 90 wt.-% and 40 wt.-%, respectively were found.

Scavenger performance tests - Parr Reactor

In order to demonstrate the efficiency of the instant invention in removing sulfhydryl compounds compared to Group 1 compounds alone, testing was performed focusing on removal of H2S from an oil/water mixture. In a 500 mL autoclave, 350 mL of synthetic solution (see below), was de-aerated for 1 hour with N2, then saturated with a sour gas mixture of 0,2 wt.-% H2S and 99,8 wt.-% CO2. This gas was purged into the solution with a flow rate of

0.6 L/min. After solution saturation by the sour gas mixture, 000 ppm of each tested H2S scavenger was injected into the system by an HPLC pump. The test solution, from Example 1 above, was homogenized using mechanical stirring at 350 RPM during the entire test. For safety reasons, at the end of the test the system was saturated again with N2, before disassembling the equipment for cleaning. Two types of synthetic solutions were used to evaluate performance of the standard and synergized hemiacetals, the first one was a synthetic oil with zero BS&W, and the second one was a mixture of synthetic oil and brine (in a 50:50 volume ratio of oil to aqueous). The performance test was carried out at 30 °C and under 1 bar, using a gas chromatograph to measure the outlet H2S content in the gas phase every two minutes. Then, a graph of the measured values of H2S content (ppm) versus time (min) was plotted. The amount of hydrogen sulfide scavenged is the area above the resultant performance curve, which is calculated by the integration of the curve. For all samples the integration of the curve was done up to 60 min after the injection of H2S scavenger. An example of a resulting curve is described in equation (1). Y = 2089.52 - 97.53X + 4.07X² - 0.07X³ + 4.14E^"4 X⁴ (1)

The output parameter of this performance test is Lsc/kghbS (Liters of H2S scavenger required to remove 1 kg of H2S from the system after 1 h of analysis). Then, this parameter was normalized to compare the results according to their active agent content. The results have been summarized in Table 1 and Table 2.

Performance test⁴ comparing hemi-acetals and hemi- acetals synergized with 3,3'-methylene-bis-5-methyloxazolidine.

¹ active agent was based on formaldehyde used per 100 g of product,

² results expressed in kg of active agent/kg of H₂S removed in 60 min,

³ consumption is an average of 3 tests,

⁴ paraffin was used in the autoclave to simulate crude oil.

As shown in the table 1 , in the inventive examples the 3,3'-methylene-bis-5- methyloxazolidine synergetically enhances the reaction between the hemiacetal and H2S. In order to simulate the oil field condition, in the examples in Table 2 brine was added into paraffin to create an emulsion. The scavenger was used in this medium to test the efficiency in hydrated crude oil. Table 2: Comparison between regular vs synergized with MBO Products kg in

Paraffin/Brine used to simulate a crude oil in emulsion.

¹ results expressed in kg of active agent/kg of H2S removed in 60 min,

² consumption is an average of 3 tests

Scavenger performance tests - Gas Breakthrough

H2S Scavengers are evaluated for their ability to remove H2S from a flowing gas stream by passing the gas laden with H2S through and column of fluid containing the scavenger chemical. Initially all of the H2S is removed from the gas stream and no H2S is detected in the effluent gas. At some point in time (the breakthrough time or TBT) the chemical can no longer entirely remove H2S from the gas stream and H2S is observed in the effluent. This parameter is a measure of the efficacy of the scavenger and the longer the break through time the better is the chemical scavenger. It is clearly important to compare two chemicals on an equal actives basis such that a meaningful comparison can be made. Glycerol hemiformal (2), synthesized from glycerol and formaldehyde, was evaluated in the gas breakthrough test at 22 % by mass of active component in the presence of the absence of 3,3'-methylenebis-5-methyloxozalidine, (7), where R is CH3, synergist. The breakthrough times are shown in Table 3

Table 3: Gas Breakthrough Data for Glycerol Hemiformal (2)

Example 13, 14 (comp.)

A comparison between the inventive and the comparative example shows that addition of a small amount of MBO will increase the H2S scavenging activity of an acetal drastically. The enhancement in scavenging efficiency exceeds the stoichiometric H2S scavenging capacity of the added MBO considerably.

Claims

Patent Claims

1. Composition comprising

I. at least one reaction product between a mono- or polyhydric alcohol and an aldehyde or ketone, and

II. at least one solvent, and

IV. at least one compound of formula (1)

wherein

R²⁰ is H or Ci to C₆ alkyl

R is H or Ci to Ce alkyl

n is 1 or 2, the components I, II and IV being different from each other.

2. The composition according to claim 1 , wherein the reaction product I. is a hemi-acetal.

3. The composition according to claim 1 and/or 2, wherein the aldehyde or ketone contains 1 to 10 carbon atoms.

4. The composition according to one or more of claims 1 - 3, wherein the alcohol contains 1 to 6 hydroxy groups.

5. The composition according to one or more of claims 1 - 4, wherein the alcohol is selected from the group consisting of monoethyleneglycol,

diethyleneglycol, triethyleneglycol and glycerol, and preferably is glycerol or ethylene glycol.

6. The composition according to one or more of claims 1 - 5, wherein the aldehyde or ketone is selected from the group consisting of formaldehyde, paraformaldehyde, glyoxal, acetaldehyde, propionaldehyde, butylaldehyde and glutaraldehyde.

7. The composition according to one or more of claims 1 - 6, wherein the aldehyde or ketone is selected from formaldehyde or paraformaldehyde.

8. The composition according to claim 1 , wherein the hemi-acetal is selected from the group consisting of the compounds of formulae (2) to (5)

R

wherein

P number from 2 to 10, and

is CH₂OH wherein

Ri is H or Ci to Cs alkyl, and

R2 is CH2OH, and

wherein

R₃ H, CHs, (CH₂)nCH₃, (CHR₄)nCH₃, CH2OH

n 1 to 10

R₄ H, CHs, (CH₂)nCH₃, (CHR₄)nCH₃, CH2OH, and

wherein

m 1 to 10, preferably 1 or 2, and

wherein

R₅ H, CHs, (CH₂)zCH₃

z 1 to 10

x 1 to 5.

9. The composition according to one or more of claims 1 - 8, wherein R20 is H.

10. The composition according to one or more of claims 1 - 9, wherein the compound of formula (1) is 3,3'-methylene-bis-5-methyl-oxazolidine.

11. The composition according to one or more of claims 1 - 10, wherein the compound of formula (1) is present in the composition in an amount from 0.01 wt.- % to 15 wt.-%, preferably between 0.5 wt.-% and 10 wt.-% and more preferably between 0.5 wt.-% and 5 wt.-%.

12. The composition according to one or more of claims 1 - 1 1 , wherein the solvent is an alcohol or water.

13. The composition according to one or more of claims 1 - 1 1 , wherein the solvent is selected from the group consisting of alkyl alcohols having from 1 to 10 carbon atoms, glycol ethers having from 4 to 15 carbon atoms, oligoethylene glycols and oligopropylene glycols having a number average molecular weight between 200 and 1000 g/mol, and aromatic compounds having a molecular weight from 70 to 400 g/mol.

14. The composition according to one or more of claims 1 - 13, wherein the solvent is present in an amount between 1 wt.-% and 50 wt.-% by weight of the composition, preferably in an amount between 5 wt.-% and 25 wt.-%.

15. The composition according to one or more of claims 1 - 14, further comprising an alkyl dimethyl benzyl ammonium chloride according to formula (8) as a corrosion inhibitor

wherein R9 is Ce to C18 alkyl.

16. The composition according to claim 15, wherein the compound of formula (8) is present in an amount between 0,01 and 5 wt.-%, preferably between 0,5 and 2 wt.-%.

17. The composition according to one or more of claims 1 - 16, comprising a demulsifier in an amount between 0.1 to 10 wt.-%, preferably between 0.5 and 2 wt.-%.

18. The composition according to claim 17, wherein the demulsifier is selected from the group consisting of polysorbates, fatty alcohols, polymers comprising ethylene oxide, polymers comprising propylene oxide, ethylene oxide-propylene oxide copolymers, alkyl polyglucosides, alkylphenol polyethylene oxide, alkyl polyethylene oxide, and ethoxylated and/or propoxylated alkyl phenol- formaldehyde resins.

19. The composition according to claim 17 or 18, wherein the demulsifier corresponds to the formula (6)

wherein

Rio is C2 to C4 alkylene,

R11 is Ci to C18 alkyl,

k is a number from 1 to 200,

m is a number from 1 to 100.

20. Composition according to claim 19, wherein R10 is C2 or C3 alkylene.

21. Composition according to claim 19 and/or 20, wherein R11 is C₄ to C12 alkyl, preferably tert.-butyl or iso-nonyl.

22. Composition according to one or more of claims 19 - 21 , wherein k is a number from 2 to 20.

23. Composition according to one or more of claims 19 - 22, wherein m is a number from 3 to 20.

24. Composition according to one or more of claims 17 and 18, wherein the demulsifier is dodecylbenezesulfonic acid

OH

25. Composition according to one or more of claims 17 - 24, wherein the demulsifier is a mixture of at least one compound of formula (6) and at least one compound of formula (7) in a weight ratio of from 5:1 to 1 :5, preferably in a weight ratio of from 3:1 to 1 :3.

26. Composition according to one or more of claims 1 - 25, comprising 1 to 95 wt.-% of the reaction product between a mono- or polyhydric alcohol and an aldehyde or ketone, preferably between 20 and 75 wt.-%.

27. Composition according to one or more of claims 1 - 26, comprising 1 to 50 wt.-% of the solvent, preferably between 5 and 25 wt.-%.

28. Composition according to one or more of claims 1 - 27, comprising 1 to 20 wt.-% of the compound of formula (1), preferably between 5 and 15 wt.-%.

29. Composition according to one or more of claims 1 - 28, additionally comprising 0.1 to 5 wt.-% of a corrosion inhibitor, preferably between 0.2 and 2 wt.-%.

30. Use of a composition according to one or more of claims 1 - 29 for scavenging hydrogen sulphide and/or mercaptans.

31. Use of a composition according to claim 30, wherein the scavenging occurs from fluids or gases produced from subterranean formations.

32. Process for the scavenging of hydrogen sulphide and/or mercaptans, comprising adding to a medium comprising such hydrogen sulphide or mercaptans a composition according to one or more of claims 1 - 29.

33. Use of a compound according to formula (1)

wherein

is H or Ci to C3 alkyl

is an integer from 1 to 5, as a synergist in the reaction between a) the reaction product of a mono- or polyhydric alcohol and an aldehyde or ketone, and

b) hydrogen sulphide and/or a mercaptan.