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GB2185995A - Removal of hydrogen sulphide from oil - Google Patents
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GB2185995A - Removal of hydrogen sulphide from oil - Google Patents

Removal of hydrogen sulphide from oil Download PDF

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Publication number
GB2185995A
GB2185995A GB08701374A GB8701374A GB2185995A GB 2185995 A GB2185995 A GB 2185995A GB 08701374 A GB08701374 A GB 08701374A GB 8701374 A GB8701374 A GB 8701374A GB 2185995 A GB2185995 A GB 2185995A
Authority
GB
United Kingdom
Prior art keywords
hydrogen sulphide
compound
isocyanate
oil
feedstock
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
GB08701374A
Other versions
GB8701374D0 (en
Inventor
Philip Kenneth Gordon Hodgson
Julie Ann Mcshea
Edward John Tinley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BP PLC
Original Assignee
BP PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BP PLC filed Critical BP PLC
Publication of GB8701374D0 publication Critical patent/GB8701374D0/en
Publication of GB2185995A publication Critical patent/GB2185995A/en
Withdrawn legal-status Critical Current

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Classifications

    • CCHEMISTRY; METALLURGY
    • C10PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
    • C10GCRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
    • C10G29/00Refining of hydrocarbon oils, in the absence of hydrogen, with other chemicals
    • C10G29/20Organic compounds not containing metal atoms

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  • Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Solid-Sorbent Or Filter-Aiding Compositions (AREA)
  • Treating Waste Gases (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

Abstract

Hydrogen sulphide is scavenged from a feedstock comprising crude oil and hydrogen sulphide by adding a compound of general formula R<1>-N=C=X-R<2> to the feedstock. R<1> is an alkyl group containing 1 to 18 carbon atoms, a cycloalkyl or alkyl cycloalkyl group containing 3 to 18 carbon atoms, an aryl group which may be substituted e.g. an alkyl aryl group wherein the alkyl moiety contains 1 to 18 carbon atoms, or a hydrogen atom, X is a nitrogen atom or an oxygen atom, and R<2> is R<1> and X is a nitrogen atom, or zero when X is an oxygen atom. Preferred scavengers include phenyl isocyanate, toluene-2,4-di-isocyanate, octadecyl isocyanate and dicyclohexyl carbodiimide.

Description

SPECIFICATION Removal of hydrogen sulphide This invention relates two a method for removing hydrogen sulphide from crude oil.
A petroleum reservoir is formed by a suitably shaped porous stratum of rock sealed with an impervious rock. The nature of the reservoir rock is extremely important as the oil is present in the small spaces or pores which separate individual rock grains.
Crude oil is generally found in a reservoir in association with water, which is often saline, and gas. Dependent upon the characteristics of the crude, the temperature and the pressure, the gas may exist in solution in the oil or additionally as a separate phase in the form of a gas cap. The oil and gas occupy the upper part of the reservoir and below there may be a considerablevolume of water, known asthe aquifer, which extends throughout the lower levels of the rock.
For oil to move through the pores of the reservoir rock and into a well,the pressure underwhich the oil exists in the reservoir must be greater than the pressure at the well.
The water contained in the aquifer is under pressure and is one source of drive. The dissolved gas associated with the oil is another and so is the free gas in the gas cap when this is present.
When oil is produced from a well, it is forced from the reservoir by natural pressure in the bottom ofthe well up which it rises to the surface. As the oil rises the pressure becomes less and gas associated with the oil is progressively released from solution.
After emerging from the well, it is necessary to treat the multi-phase mixture of oil, gas and possiblywater, hereinafter termed "produced well fluid", in separators to remove free or potentially free gas, mainly methane and ethane. By potentially free gas is meant gas which would be likely to come out of solution if the oil were maintained at about atmospheric pressure, for example, during transport in a tanker or in storage tanks, without treatment.
Some crude oils contain not only dissolved hydrocarbon gases, but also appreciable quantities of hydrogen sulphide. This problem is particularly associated with "watered out" reservoirs approaching the end oftheir life, although it is not confined to them.
Hydrogen sulphide is a toxic, evil-smelling and corrosive gas and is unacceptable in quantity from both safety and environmental considerations. When hydrogen sulphide is present, it is necessary to provide furthertreatmentto reducethe concentration of hydrogen sulphide in all products to an acceptably low level.
Much ofthe hydrogen sulphide associates with the gases resulting from the gas-oil separation process and this may be removed by scrubbing the gases, for example with amines. This requires expensive gas/liquid contacting, regeneration and conversion facilities. The cost of this extra treatment is considerable and in some cases, e.g., offshore fields, gas scrubbing may not be feasible since space may not be available on the field platforms for retrofitting the necessary equipment.
Even where gas scrubbing is possible, this still leaves some hydrogen sulphide associated with the oil and aqueous phases, however.
It would clearly be more convenient to treat the produced well fluid with a scavenger for hydrogen sulphide before the various phases are separated.
We have now discovered that certain compounds containing contiguous double bonds are capable of reacting with hydrogen sulphide under mixed phase conditions and forming relatively harmless thiol compounds.
Thus according to the present invention, there is provided a method for scavenging hydrogen sulphide from a feedstock comprising crude oil and hydrogen sulphide which method comprises adding a compound of general formula: R1 -N=C=X-R2 wherein R1 is an alkyl group containing 1 to 18 carbon atoms, a cycloalkyl or alkyl cycloalkyl group containing 3to 18 carbon atoms, an aryl group, an alkyl aryl groupwhereinthealkyl moiety contains 1 to 18carbon atoms or a hydrogen atom, Xis a nitrogen atom or an oxygen atom, and R2 is R1 when Xis a nitrogen atom, or zero when Xis an oxygen atom, to the feedstock and allowing the compound to react with the hydrogen sulphide contained therein.
Preferred compounds are isocyanates, most preferably aromatic isocyanates and di-isocyanates.
The feedstock may be produced well fluid as hereinbefore defined.
Although the above defined scavengers are particularly useful in treating produced well fluids since they can withstand the severe environment of the latter, they are also suitable for treating crude oil or petroleum fractions under milder conditions, for example, in pipelines, storage tanks, railcars, tankers, etc., afterthe produced wel I fl uid has been dewatered and degassed.
When water is present, the partitioning of hydrogen sulphide between the various phases depends largely upon the pH and redox potential of the aqueous phase. These will normally be such that the hydrogen sulphide is concentrated in the oil and aqueous phases, i.e., in the ranges 4to 9.5 and -0.2 to -0.3 Vwith reference to hydrogen potential, respectively.
Preferably the scavengers are oil soluble and react with the hydrogen sulphide in the oil phase. By mass transferthis also reduces the concentration of hydrogen sulphide in the gaseous and aqueous phases. The oil soluble scavengers should also be stable in the presence of water and thermally stable since fluids are often produced at elevated temperatures.
Suitable scavengers include
octadecyl isocyanate phenyl isocyanate CeH13-N = C = N Cg H13 dicyclohexyl carbodi-imide The scavenger is suitably used in amount 1 to 50, preferabiy 5 to 15, times the amount of hydrogen sulphide present, on a molar basis.
The length oftime required to scavenge the hydrogen sulphide is generally ofthe order of 1 to 15 minutes.
The invention is illustrated with reference to the following Examples.
Examples 1-5 Aflaskwas charged with 309 crude oil (from the Welton oil field in the English Midlands), and 8g water, buffered to a pH of 7 and sealed. 2 ml of 0.7% Na2S.9H2O were then injected by means of a syringe, giving a potential H2S content of 0.029.
The resulting oil/aqueous liquid/gas system was allowed two equilibratefor 15 minutes after which in Example 2-5 the scavenger was injected in solution into the flask and the latterwas shaken.
After a further 15 minutes a sample of the gas was removed to a "Gas-Tec" detection tube and the hydrogen sulphide concentration was determined. Thefollowing results were obtained: Example Scavenger Concentration of H2S (ppm) 1 Control 700 (no additive) 2 Phenylisocyanate 20 (0.1g in lgtoluene) 3 Dicyclohexylcarbodi-imide 100 (0.1g in lgtoluene) 4 Octadecylisocyanate 400 (0.1g in lgtoluene) 5 Toluene-2,4-di-isocyanate 20 (0.1g in lgtoluene)

Claims (9)

1. A method for scavenging hydrogen sulphide from a feedstock comprising crude oil and hydrogen sulphidewhich method comprises adding a compound of general formula: R1 ~ N = C = XR2 wherein R1 is an alkyl group containing 1 to 18 carbon atoms, a cycloalkyl or alkyl cycloalkyl group containing 3to 18 carbon atoms, an aryl group, an alkyl aryl groupwhereinthealkyl moiety contains 1 to l8carbon atoms or a hydrogen atom, Xis a nitrogen atom or an oxygen atom, and R2 is R1 when Xis a nitrogen atom, or zero when Xis an oxygen atom, to thefeedstock and allowing the compound to react with the hydrogen sulphide contained therein.
2. A method according to claim 1 wherein the compound is an isocyanate.
3. A method according to claim 2 wherein the compound is an aromatic isocyanate.
4. A method according to claim 3 wherein the aromatic isocyanate is phenyl isocyanate ortoluene-2, 4-di-isocyanate.
5. A method according to any ofthe preceding claims wherein the feedstock is produced well fluid as hereinbefore defined.
6. A method according to any of claims 1 to 3 wherein the feedstockis dewatered and/or degassed crude petroleum.
7. A method according to any of the preceding claims wherein the compound is used in amount 1 to 50 times the amount of hydrogen sulphide present on a molar basis.
8. A method according to claim 7 wherein the compound is used in amount 1 to 50 times the amount of hydrogen sulphide present on a molar basis.
9. A method for scavenging hydrogen sulphide from a feedstock comprising crude oil and hydrogen sulphide according to claim 1 as hereinbefore described with reference to Examples 2 to 5.
GB08701374A 1986-01-30 1987-01-22 Removal of hydrogen sulphide from oil Withdrawn GB2185995A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB868602319A GB8602319D0 (en) 1986-01-30 1986-01-30 Removing hydrogen sulphide from crude oil

Publications (2)

Publication Number Publication Date
GB8701374D0 GB8701374D0 (en) 1987-02-25
GB2185995A true GB2185995A (en) 1987-08-05

Family

ID=10592245

Family Applications (2)

Application Number Title Priority Date Filing Date
GB868602319A Pending GB8602319D0 (en) 1986-01-30 1986-01-30 Removing hydrogen sulphide from crude oil
GB08701374A Withdrawn GB2185995A (en) 1986-01-30 1987-01-22 Removal of hydrogen sulphide from oil

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB868602319A Pending GB8602319D0 (en) 1986-01-30 1986-01-30 Removing hydrogen sulphide from crude oil

Country Status (2)

Country Link
GB (2) GB8602319D0 (en)
NO (1) NO870352L (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0411750A3 (en) * 1989-06-06 1992-03-04 Rohm And Haas Company Organic stabilizers for isothiazolones
RU2312070C2 (en) * 2005-02-03 2007-12-10 Общество с ограниченной ответственностью "Инжиниринговая компания "ИНКОМП-НЕФТЬ" Hydrogen sulfide neutralization composition
RU2404175C2 (en) * 2008-06-03 2010-11-20 Учреждение Российской Академии Наук Институт Нефтехимии И Катализа Ран Two-component hydrogen sulphide scavenger and preparation method thereof

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0411750A3 (en) * 1989-06-06 1992-03-04 Rohm And Haas Company Organic stabilizers for isothiazolones
RU2312070C2 (en) * 2005-02-03 2007-12-10 Общество с ограниченной ответственностью "Инжиниринговая компания "ИНКОМП-НЕФТЬ" Hydrogen sulfide neutralization composition
RU2404175C2 (en) * 2008-06-03 2010-11-20 Учреждение Российской Академии Наук Институт Нефтехимии И Катализа Ран Two-component hydrogen sulphide scavenger and preparation method thereof

Also Published As

Publication number Publication date
GB8602319D0 (en) 1986-03-05
NO870352D0 (en) 1987-01-28
NO870352L (en) 1987-07-31
GB8701374D0 (en) 1987-02-25

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)