U.S. patent application number 16/431902 was filed with the patent office on 2019-12-05 for methods for reducing hydrogen sulfide in crude oil.
This patent application is currently assigned to Innospec Limited. The applicant listed for this patent is Innospec Limited. Invention is credited to Cenk Burgazli, Philip James Maltas.
Application Number | 20190367819 16/431902 |
Document ID | / |
Family ID | 66857939 |
Filed Date | 2019-12-05 |
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United States Patent
Application |
20190367819 |
Kind Code |
A1 |
Burgazli; Cenk ; et
al. |
December 5, 2019 |
METHODS FOR REDUCING HYDROGEN SULFIDE IN CRUDE OIL
Abstract
The invention provides a method of removing or lowering amounts
of hydrogen sulfide in a crude oil, the method comprising adding to
the crude oil an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
Inventors: |
Burgazli; Cenk; (Middletown,
DE) ; Maltas; Philip James; (Willaston, GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Innospec Limited |
Cheshire |
|
GB |
|
|
Assignee: |
; Innospec Limited
Cheshire
GB
|
Family ID: |
66857939 |
Appl. No.: |
16/431902 |
Filed: |
June 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62680695 |
Jun 5, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C10G 2300/202 20130101;
C10G 2300/207 20130101; C10G 2400/08 20130101; C10G 2300/1051
20130101; C10L 2200/043 20130101; C10L 2270/04 20130101; C10L 10/00
20130101; C10G 2300/104 20130101; C10L 1/228 20130101; C10G
2300/1055 20130101; C10L 1/2283 20130101; C10L 2290/543 20130101;
C10G 29/20 20130101 |
International
Class: |
C10G 29/20 20060101
C10G029/20; C10L 10/00 20060101 C10L010/00; C10L 1/228 20060101
C10L001/228 |
Claims
1. A method of removing or lowering amounts of hydrogen sulfide in
a crude oil, the method comprising adding to the crude oil an imine
compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
2. A method of producing a distillate fuel component boiling in the
kerosene range from a crude oil, wherein the crude oil contains an
imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and/or an amine residue thereof,
the method comprising distilling the crude oil to form the
distillate fuel component.
3. The method according to claim 1, wherein R.sup.1 represents a
methyl group or a 5C alkyl group.
4. The method according to claim 2, wherein R.sup.1 represents a
methyl group or a 5C alkyl group.
5. The method according to claim 3, wherein R.sup.1 represents a 5C
alkyl group.
6. The method according to claim 4, wherein R.sup.1 represents a 5C
alkyl group.
7. The method according to claim 1, wherein the imine compound is
tert-butylimine or tert-octylimine.
8. The method according to claim 2, wherein the imine compound is
tert-butylimine or tert-octylimine.
9. The method according to claim 3, wherein the imine compound is
tert-butylimine or tert-octylimine.
10. The method according to claim 4, wherein the imine compound is
tert-butylimine or tert-octylimine.
11. The method according to claim 7, wherein the imine compound is
tert-octylimine.
12. The method according to claim 8, wherein the imine compound is
tert-octylimine.
13. The method according to claim 9, wherein the imine compound is
tert-octylimine.
14. The method according to claim 10, wherein the imine compound is
tert-octylimine.
15. The method according to claim 1, wherein the imine compound is
prepared from tert-octyl amine and formaldehyde or
paraformaldehyde.
16. The method according to claim 2, wherein the imine compound is
prepared from tert-octyl amine and formaldehyde or
paraformaldehyde.
17. The method according to claim 3, wherein the imine compound is
prepared from tert-octyl amine and formaldehyde or
paraformaldehyde.
18. The method according to claim 4, wherein the imine compound is
prepared from tert-octyl amine and formaldehyde or
paraformaldehyde.
19. A composition comprising a crude oil and an imine compound
represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
20. The composition according to claim 19, wherein R.sup.1
represents a methyl group or a 5C alkyl group.
21. The composition according to claim 20, wherein R.sup.1
represents a 5C alkyl group.
22. The composition according to claim 19, wherein the imine
compound is tert-butylimine or tert-octylimine.
23. The composition according to claim 22, wherein the imine
compound is tert-octylimine.
24. The composition according to claim 19, wherein the imine
compound is prepared from tert-octyl amine and formaldehyde or
paraformaldehyde.
25. A distillate fuel component boiling in the kerosene range
obtainable by a method of producing a distillate fuel component
boiling in the kerosene range from a crude oil, wherein the crude
oil contains an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and/or an amine residue thereof,
the method comprising distilling the crude oil to form the
distillate fuel component.
26. The method of producing a distillate fuel component boiling in
the kerosene range according to claim 2, wherein the distillate
fuel component has improved thermal stability when compared to a
distillate fuel component produced in the same way but from a crude
oil containing an imine compound represented by the formula
R.sup.2--N.dbd.CH.sub.2, wherein R.sup.2 represents an alkyl group
having 10 or more carbon atoms, and/or an amine residue
thereof.
27. The distillate fuel component boiling in the kerosene range
according to claim 25, wherein the distillate fuel component has
improved thermal stability when compared to a distillate fuel
component produced in the same way but from a crude oil containing
an imine compound represented by the formula
R.sup.2--N.dbd.CH.sub.2, wherein R.sup.2 represents an alkyl group
having 10 or more carbon atoms, and/or an amine residue
thereof.
28. An aviation turbine fuel composition comprising a distillate
fuel component boiling in the kerosene range obtainable by a method
of producing a distillate fuel component boiling in the kerosene
range from a crude oil, wherein the crude oil contains an imine
compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and/or an amine residue thereof,
the method comprising distilling the crude oil to form the
distillate fuel component.
29. The aviation turbine fuel composition according to claim 28,
wherein the aviation turbine fuel has improved thermal stability as
measured by ASTM D3241 when compared to an aviation turbine fuel
produced in the same way but from a crude oil containing an imine
compound represented by the formula R.sup.2--N.dbd.CH.sub.2,
wherein R.sup.2 represents an alkyl group having 10 or more carbon
atoms, and/or an amine residue thereof.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to and benefit of U.S.
Provisional Application No. 62/680,695, entitled METHODS FOR
REDUCING HYDROGEN SULFIDE IN CRUDE OIL, filed on Jun. 5, 2018,
which is incorporated by reference herein in its entirety and for
all purposes.
TECHNICAL FIELD OF THE INVENTION
[0002] The invention relates to a method of removing or lowering
amounts of hydrogen sulfide in a crude oil. The invention also
relates to a method of forming a distillate fuel component boiling
in the kerosene range from a crude oil. The invention also relates
to a composition comprising a crude oil and an imine compound and
to a distillate fuel component boiling in the kerosene range.
BACKGROUND TO THE INVENTION
[0003] It is commonly known that crude oil typically contains
hydrogen sulfide and other sulfur based species that can liberate
hydrogen sulfide (i.e. hydrogen sulfide precursors). Hydrogen
sulfide is toxic and corrosive and so it is desirable to remove it
from crude oil, or at least reduce the levels of hydrogen sulfide
present in crude oil.
[0004] Various methods of removing or reducing the amount of
hydrogen sulfide (and optionally other other sulfur based species
when present) in crude oil are known. One of the most common
methods is to use hydrogen sulfide scavengers, which react with
hydrogen sulfide and remove it or reduce its amount, for example
when present in crude oils.
[0005] Hydrogen sulfide scavengers may be used at various stages of
the crude oil production and/or processing operations. For example,
the hydrogen sulfide scavenger may be added to the crude oil whilst
downhole, during production, during above ground processing, during
transportation or storage, i.e. at any point prior to entering the
refinery for processing. Hydrogen sulfide scavengers may also be
used at the refinery for example, on receipt of the oil, during
storage or during the refining process.
[0006] Thus, it is well known to treat crude oil with hydrogen
sulfide scavengers to remove or reduce the levels of hydrogen
sulfide in the oil. Examples of commonly used organic hydrogen
sulfide scavengers include non amine scavengers such as aldehydes
and protected aldehydes like acetals, and nitrogen based scavengers
such as amines, triazines and imine compounds.
[0007] When the imine compound reacts with hydrogen sulfide and/or
sulfur based species, the reaction produces a nitrogen containing
compound, for example an amine residue of the imine and a hydrogen
sulfide aldehyde adduct.
[0008] U.S. Pat. No. 5,169,411 discloses the use of certain
hindered monoimines as hydrogen sulfide scavengers in the sulfur
containing complex media of crude oils, petroleum residua and
fuels.
[0009] Whilst hydrogen sulfide scavengers are known, it would be
desirable to provide further hydrogen sulfide scavengers, for
example which are more effective at removing or reducing amounts of
hydrogen sulfide in crude oil than current hydrogen sulfide
scavengers. In particular it would be desirable to provide imine
based hydrogen sulfide scavengers which react more quickly than
known scavengers and/or can consistently achieve low levels of
hydrogen sulfide at low treat rates.
[0010] At a refinery, the crude oil (for example containing
hydrogen sulfide scavenger(s)) is typically treated by a desalting
process and then distilled at atmospheric pressure to produce
several distillation cuts or fractions including gaseous
hydrocarbons, gasoline, naptha, kerosene, light gas oil and heavy
gas oil. After this atmospheric first distillation, a high
proportion (typically 40 to 60 wt %) remains as a crude oil residue
(also known as an atmospheric residue), which residue is then
typically distilled in a vacuum distillation unit. After the vacuum
distillation, a further crude oil residue remains (also known as a
vacuum residue). The distillation fractions and residues may be
further processed in the refinery.
[0011] The distillation fractions may be further processed or used
as straight run distillates alone or with other blending components
to produce fuels meeting appropriate fuel specifications. For
example, after further processing, the distillate fuel component
boiling in the kerosene range may be suitable for use as a
component of an aviation turbine fuel.
[0012] Fuels are required to meet many fuel specification
properties such as boiling range, corrosion requirements, lubricity
and thermal stability. Of particular importance for the aviation
turbine fuel is the thermal stability requirement for example, as
listed in ASTM D1655 Standard Specification for Aviation Turbine
Fuels for the fuel as measured by ASTM D3241 Test Method for
Thermal Oxidation Stability of Aviation Turbine Fuels.
[0013] Starting in 2015 there were several occurrences of thermal
stability failures in aviation turbine fuels. The failures were
with fuels that were previously qualified by ASTM D3241 as meeting
the ASTM D1655 specification thermal stability requirement but upon
storage were failing to meet this thermal stability requirement. No
other specification parameter tested was found to be outside
acceptable limits. The subject fuels were analysed and found to
contain trace amounts of atypical amines, specifically amines that
were not found in crude oil. The source of these amines have so far
not been identified.
[0014] The inventors believe the above mentioned thermal stability
issues may result from the presence of the atypical amines in the
aviation turbine fuel and that the presence of the atypical amines
results from the use of hydrogen sulfide scavengers, where the
amines were either directly used as a hydrogen sulfide scavenger to
capture hydrogen sulfide or are by products of hydrogen sulfide
scavengers. The inventors believe that these amines distil in the
kerosene fraction and find their way into aviation turbine fuel,
thus adversely impacting aviation turbine fuel thermal
stability.
[0015] It would be desirable to overcome the thermal stability
issues associated with aviation turbine fuels. It would also be
desirable to provide improved methods of removing or reducing
levels of hydrogen sulfide in crude oil, and particularly improved
methods of removing or reducing levels of hydrogen sulfide in crude
oil which do not adversely affect the thermal stability of aviation
turbine fuels produced from said crude oils.
SUMMARY OF THE INVENTION
[0016] According to a first aspect of the present invention, there
is provided a method of removing or lowering amounts of hydrogen
sulfide in a crude oil, the method comprising adding to the crude
oil an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
[0017] According to a second aspect of the present invention, there
is provided a method of producing a distillate fuel component
boiling in the kerosene range from a crude oil, wherein the crude
oil contains an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and/or an amine residue thereof,
the method comprising distilling the crude oil to form the
distillate fuel component.
[0018] According to a third aspect of the present invention, there
is provided a composition comprising a crude oil and an imine
compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
[0019] According to a fourth aspect of the present invention, there
is provided a distillate fuel component boiling in the kerosene
range obtainable by (or obtained by) a method according to the
second aspect of the present invention.
[0020] According to a fifth aspect of the present invention, there
is provided the use of a distillate fuel component boiling in the
kerosene range according to the fourth aspect of the present
invention in an aviation turbine fuel composition.
[0021] According to a sixth aspect of the present invention, there
is provided an aviation turbine fuel composition comprising a
distillate fuel component boiling in the kerosene range according
to the fourth aspect of the present invention.
[0022] According to a seventh aspect of the present invention,
there is provided a method of removing or lowering amounts of
hydrogen sulfide present during distillation of a crude oil to form
a distillate fuel component boiling in the kerosene range, the
method comprising adding to the crude oil an imine compound
represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and distilling the crude oil
(including the imine compound) to form the distillate fuel
component.
[0023] According to an eighth aspect of the present invention,
there is provided the use of an imine compound represented by the
formula R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, to remove or lower the amount of
hydrogen sulfide in a crude oil.
[0024] According to a ninth aspect of the present invention, there
is provided the use of an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, in the preparation of a distillate
fuel component boiling in the kerosene range.
DETAILED DESCRIPTION OF THE INVENTION
[0025] Unless otherwise stated, the following terms used in the
specification and claims have the meanings set out below.
[0026] As used herein, the term "crude oil" means unrefined oil.
Crude oil is typically composed of a complex mixture of organic
(predominantly hydrocarbon) and inorganic compounds.
[0027] As used herein the term "aviation turbine fuel" means any
type of fuel suitable for use in aircraft powered by gas-turbine
engines. Aviation turbine fuel may also be commonly known as
aviation kerosene, aviation turbine kerosene, aviation jet fuel or
jet fuel. Aviation turbine fuel typically comprises a petroleum
distillate boiling in the kerosene range and is produced to a
national or international aviation specification such as ASTM
D1655.
[0028] As used herein, the term "alkyl" includes both straight and
branched chain alkyl groups. The term "alkyl" does not include aryl
groups. References to individual alkyl groups such as "propyl" are
specific for the straight chain version only and references to
individual branched chain alkyl groups such as "isopropyl" are
specific for the branched chain version only. For example,
"(1-5C)alkyl" includes (1-2C)alkyl, propyl, isopropyl and
tert-butyl.
[0029] 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.
[0030] 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 may also be taken to include the meaning "consists of" or
"consisting of".
[0031] 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.
Method
[0032] In a first aspect, the present invention provides a method
of removing or lowering amounts of hydrogen sulfide in a crude oil,
the method comprising adding to the crude oil an imine compound
represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
[0033] In the method of the first aspect, the crude oil (prior to
addition of the imine compound) may, for example, contain up to
5000 mg of hydrogen sulfide per L (litre) of crude oil, for example
up to 1000 mg of hydrogen sulfide per L (litre) of crude oil, or
for example up to 500 mg/L. Typically, crude oils may contain up to
200 mg, or up 150 mg, of hydrogen sulfide per L of crude oil. For
example, the crude oil may contain 1 to 150 mg, such as 1 to 100
mg, of hydrogen sulfide per L of crude oil. Typically, the crude
oil may contain 10 to 50 mg of hydrogen sulfide per L of crude oil.
Such amounts refer to the amount of hydrogen sulfide in the crude
oil in the liquid phase.
[0034] It is common for levels of hydrogen sulfide to be measured
in the gas phase such as in the head space of a tank. Such
measurements in the gas phase are commonly quoted as parts per
million (ppm). There is no direct correlation between the amount of
hydrogen sulfide present in the gas phase (as measured in ppm) and
the amount of hydrogen sulfide present in the crude oil liquid
phase (as measured in mg of hydrogen sulfide per L of (liquid)
crude oil). The ratio of these two measures, or partition
coefficients, is affected by many factors, such as the temperature
of the crude oil, the viscosity of the crude oil etc. As a very
rough guide, 1 mg of hydrogen sulfide in 1 L of in crude oil in the
liquid phase may typically result in a level of 1 to 500 ppm of
hydrogen sulfide in the gas phase. Thus, the method of the first
aspect may be used to treat crude oils which have hydrogen sulfide
present in the gas phase in amounts of up to 100,000 ppm or
more.
[0035] The method of the first aspect of the invention comprises
adding an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, to a crude oil. The imine compound
is added in an amount that is effective to remove or lower the
amount of hydrogen sulfide present.
[0036] The particular treat rate of imine compound (i.e. amount of
imine compound added to the crude oil) will depend on several
factors including, for example, the amount of hydrogen sulfide
present in the crude oil; the desired final level of hydrogen
sulfide to be achieved; the exact imine compound being used; the
desired reaction time to achieve the desired level of hydrogen
sulfide; the temperature, pressure, water content, or pH of the
crude oil; the mixing efficiency of the crude oil and imine
compound; and the variability in any of these parameters. For
example, one mole of imine compound may react with one mole of
hydrogen sulfide. For example, 141 mg of tert-octylimine per L of
crude oil may be required to treat 34 mg of hydrogen sulfide per L
of crude oil. Higher treat ratios may be desirable in some
circumstances, for example to achieve faster reaction times, or to
provide a safety margin ensuring very low levels of hydrogen
sulfide in the treated fuel. Lower treat ratios may be desirable in
some circumstances for example to achieve a reduction in hydrogen
sulfide levels without completely removing the hydrogen sulfide.
For example, in some circumstances 0.1 to 100 or 0.5 to 20 or 0.8
to 10 molar equivalents of imine compound may be used.
[0037] Suitably, in the method of the first aspect some or all of
the hydrogen sulfide present in the crude oil is converted to a
less corrosive, reactive and/or toxic form, for example through
chemical reaction with the imine compound.
[0038] The treat rate of imine compound may be from 1 to 20000 mg,
for example from 1 to 5000 mg, for example from 1 to 2500 mg, such
as from 1 to 1000 mg, of imine compound per L of crude oil.
Typically, the treat rate of imine compound may be from 1 to 500 mg
of imine compound per L of crude oil.
[0039] The treat rate/ratio of imine compound:hydrogen sulfide
present in the crude oil may be from 40:1 to 1:10, preferably from
10:1 to 1:2, more preferably from 6:1 to 1:1 and most preferably
from 5:1 to 2:1. Such treat rate ratios are on a weight basis. For
example, a treat rate of 40 mg imine compound per L of crude oil
when used to treat an amount of 1 mg of hydrogen sulfide per L of
crude oil would be a ratio of 40:1.
[0040] Suitably, the method of the first aspect of the invention
lowers the amount of hydrogen sulfide present in a crude oil to an
amount of less than 20 mg of hydrogen sulfide per L of crude oil,
preferably less than 15 mg of hydrogen sulfide per L of crude oil,
such as less than 10 mg or less than 5 mg of hydrogen sulfide per L
of crude oil.
[0041] By "removing hydrogen sulfide" we mean that the hydrogen
sulfide is substantially removed, for example such that 1 L of the
treated crude oil would contain less than 5 mg, such as less than 4
mg, preferably less than 3 mg, less than 2 mg or less than 1 mg, of
hydrogen sulfide.
[0042] The hydrogen sulfide may be present in the crude oil
naturally or may be liberated from sulfur based species naturally
present in the crude oil.
[0043] The imine compound may also react with other sulfur species,
such as HS.sup.- and S.sup.2- when present.
[0044] The imine compound used in the method of the first aspect of
the invention is represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, also shown as:
##STR00001##
wherein R.sup.1 represents a (1-5C)alkyl group.
[0045] References to "an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group" are intended to refer to one or
more of such imine compounds selected from this formula. Thus,
mixtures of two or more imine compounds having the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2 may be used.
[0046] Examples of suitable imine compounds for use in the method
of the first aspect of the present invention are as follows:
##STR00002##
[0047] Mixtures of imine compounds having the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2 may also be used.
[0048] Suitably, in the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, R.sup.1 represents a
methyl group or a 5C alkyl group, more particularly R.sup.1
represents a 5C alkyl group. For example, the imine compound that
is used in the method of the first aspect of the invention may be
tert-butylimine or tert-octylimine or mixtures thereof. More
particularly the imine compound that is used in the method of the
first aspect of the invention may be tert-octylimine.
[0049] Suitably, the imine compound used in the method of the first
aspect of the invention may be an imine compound prepared from
tert-butyl amine and formaldehyde or paraformaldehyde.
[0050] Suitably, the imine compound used in the method of the first
aspect of the invention may be an imine compound prepared from
tert-octyl amine and formaldehyde or paraformaldehyde. Preparation
of imines from amines and aldehydes is well known to those skilled
in the art.
[0051] When the aforementioned imine compounds are used to remove
or reduce levels of hydrogen sulfide in a crude oil, the imine
compound reacts with the hydrogen sulfide, i.e. the imine compound
acts as a hydrogen sulfide scavenger. The imine compounds may also
react with other sulfur based species such as HS.sup.- and S.sup.2-
when present (which species can liberate hydrogen sulfide). The
scavenger does not remove sulfur from the crude oil, but it changes
the hydrogen sulfide into a different form of sulfur compound
(which form is more readily tolerated). The reaction of the imine
compound with hydrogen sulfide produces at least an amine compound,
i.e. an amine residue of the imine compound. For example, when the
imine compound is tert-octylimine, the amine produced by reaction
with hydrogen sulfide is tert-octylamine. When the imine compound
is tert-butylimine, the amine produced by reaction with hydrogen
sulfide is tert-butylamine.
[0052] Suitably, the method of the first aspect of the invention is
for removing or lowering amounts of hydrogen sulfide in a crude
oil. It has advantageously been found that when an imine compound
as defined herein is used in this method, both the imine compound
and the amine residue (i.e. the amine that is produced by the
reaction of the imine compound with hydrogen sulfide and/or a
sulfur based species) are removed during the distillation of the
crude oil at temperatures below the boiling range of the kerosene
cut. This means that little or none of the imine and/or amine
residue thereof enters the kerosene cut. In other words, the method
treats the crude oil so that the hydrogen sulfide scavenger and
residues thereof do not carry over into the kerosene distillate.
The inventors believe that this provides a kerosene distillate that
may be used as a component of aviation turbine fuel, in which
little or no atypical amines are present such that aviation turbine
fuels including this distillate as a component thereof do not
exhibit undesirable thermal instability as discussed above. Thus,
the method of the first aspect of the invention overcomes the
thermal stability issues associated with aviation turbine
fuels.
[0053] It is also believed that the particular imine compounds used
in the method of the first aspect of the present invention are
especially effective at removing or lowering amounts of hydrogen
sulfide (and optionally other sulfur based species when present)
from crude oil.
[0054] A second aspect of the invention provides a method of
forming a distillate fuel component boiling in the kerosene range
from a crude oil, wherein the crude oil contains an imine compound
represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and/or an amine residue thereof,
the method comprising distilling the crude oil to form the
distillate fuel component.
[0055] By the "distillate fuel component boiling in the kerosene
range" we mean a distillate with a boiling range that is suitable
for use as an aviation turbine fuel component. Typically, such a
component may boil in the range of 150 to 300.degree. C., for
example in the range of 190 to 270.degree. C.
[0056] Suitable and preferred aspects of the second aspect of the
invention, for example in relation to the imine compound and amine
residue thereof, are as set out above in relation to the first
aspect.
[0057] In the second aspect of the invention, the crude oil
contains the imine compound and/or amine residue thereof. The imine
compound will typically have been added to the crude oil prior to
distillation, as discussed herein. For example, the imine compound
may have been added to the crude oil whilst it is being removed
(for example pumped) from the ground and/or transported and/or
stored and/or processed prior to distillation.
[0058] The imine compound will have been added to the crude oil in
an amount that is effective to remove or reduce levels of hydrogen
sulfide therein. Such treat rates are as described in relation to
the first aspect.
[0059] The amine residue that may be contained in the crude oil
will be present as a product of the reaction between the imine
compound and the hydrogen sulfide (and optionally other sulfur
containing species when present) contained in the crude oil, as
discussed herein. The amine residue may be present at between 0 mol
% and 100 mol % of the amount of imine compound originally added.
Typically the amine residue may be present in an amount of 1 to
2500 mg, such as 1 to 1000 mg, of amine per L of crude oil. More
typically, the amine residue may be present in an amount of 1 to
500 mg of amine per L of crude oil.
[0060] The method of the second aspect of the invention is
advantageous as it allows the formation of a distillate fuel
component boiling in the kerosene range that is substantially free
of the imine compound and amine residue thereof. This is believed
to provide a distillate fuel component boiling in the kerosene
range that may be used as a component of aviation turbine fuel, in
which little or no atypical amines are present such that aviation
turbine fuels including this distillate fuel component do not
exhibit undesirable thermal instability as discussed above. Thus,
the method of the second aspect of the invention overcomes the
observed thermal stability issues associated with atypical amines
being present in aviation turbine fuels.
[0061] The methods of the invention may comprise any further
suitable steps, such as mixing (for example by stirring) the crude
oil and the imine compound together and optionally heating.
[0062] The present invention further provides a method of producing
a distillate fuel component boiling in the kerosene range from a
crude oil, wherein the crude oil contains an imine compound
selected from tert-butylimine and/or tert-octylimine (preferably
the imine compound is tert-octylimine), and/or an amine residue
thereof selected from tert-butylamine and/or tert-octylamine
(preferably the amine residue is tert-octylamine), the method
comprising distilling the crude oil to form the distillate fuel
component.
Composition
[0063] A third aspect of the present invention provides a
composition comprising a crude oil and an imine compound
represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group.
[0064] As discussed above in relation to the first and second
aspects, examples of suitable imine compounds for including in the
composition of the third aspect of the present invention are as
follows:
##STR00003##
[0065] Mixtures of imine compounds having the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2 may also be used.
[0066] Suitably, in the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, R.sup.1 represents a
methyl group or a 5C alkyl group, more particularly R.sup.1
represents a 5C alkyl group. For example, the imine compound that
is included in the composition of the third aspect of the invention
may be tert-butylimine or tert-octylimine or mixtures thereof. More
particularly, the imine compound may be tert-octylimine.
[0067] Suitably, the imine compound that is included in the
composition of the third aspect of the invention may be an imine
compound prepared from tert-butyl amine and formaldehyde or
paraformaldehyde.
[0068] Suitably, the imine compound that is included in the
composition of the third aspect of the invention may be an imine
compound prepared from tert-octyl amine and formaldehyde or
paraformaldehyde.
[0069] Immediately after addition of the imine compound, the
composition of the third aspect comprises the imine compound in an
amount that is effective to remove or lower the amount of hydrogen
sulfide present. Such treat rates are as described in relation to
the first aspect.
[0070] It will be appreciated that on reaction with hydrogen
sulfide, the imine compound will form an amine residue as discussed
herein. Thus, the composition of the third aspect may additionally
comprise an amine residue of the imine compound.
[0071] Suitably, the composition of the third aspect may comprise a
crude oil and from 1 to 20000 mg, for example from 1 to 5000 mg,
such as from 1 to 1000 mg, preferably from 1 to 500 mg of an imine
compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and from 5000 to 1 mg, such as from
1000 to 1 mg, preferably from 500 to 1 mg of an amine residue
thereof, per L of crude oil.
[0072] The particular imine compound(s) included in the composition
of the third aspect of the present invention are especially
effective at removing or lowering amounts of hydrogen sulfide (and
optionally other sulfur based species when present) from crude oil,
for example compared to other known hydrogen sulfide
scavengers.
[0073] The composition of the third aspect of the invention is also
considered to be advantageous because the particular imine
compounds included in the composition are removed during the
distillation of the crude oil at temperatures below the boiling
range of the kerosene cut. This means that little or none of the
imine and/or amine residue thereof enters the kerosene cut. The
inventors believe that this provides a kerosene distillate that may
be used as a component of aviation turbine fuel, in which little or
no atypical amines are present such that aviation turbine fuels
including this component do not exhibit undesirable thermal
instability as discussed above. Thus, the composition of the third
aspect of the invention overcomes the observed thermal stability
issues associated with atypical amines being present in aviation
turbine fuels.
[0074] The composition of the third aspect of the invention may
comprise further additional components. Such additional components
are typical crude oil additives arising from for example drilling,
fracturing, completion, production, storage and transport. Such
additives are known to those skilled in the art.
Distillate Fuels
[0075] A fourth aspect of the present invention provides a
distillate fuel component boiling in the kerosene range obtainable
by (or obtained by) a method according to the second aspect of the
present invention.
[0076] Suitably, the distillate fuel component of the fourth aspect
of the invention is substantially free of imine compound(s)
represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group and amine residues thereof. Thus,
the distillate fuel component of the fourth aspect of the present
invention is particularly suitable for use as a component of an
aviation turbine fuel composition, as discussed herein.
[0077] A fifth aspect of the present invention provides the use of
a distillate fuel component boiling in the kerosene range according
to the fourth aspect of the present invention in an aviation
turbine fuel composition.
[0078] A sixth aspect of the present invention provides an aviation
turbine fuel composition comprising a distillate fuel component
boiling in the kerosene range according to the fourth aspect of the
present invention.
[0079] The present invention further provides a method of producing
a distillate fuel component boiling in the kerosene range according
to the second aspect of the invention, wherein the distillate fuel
component has improved thermal stability when compared to a
distillate fuel component produced in the same way but from a crude
oil containing an imine compound represented by the formula
R.sup.2--N.dbd.CH.sub.2, wherein R.sup.2 represents an alkyl group
having 10 or more carbon atoms, and/or an amine residue
thereof.
[0080] The present invention further provides a distillate fuel
component boiling in the kerosene range according to the fourth
aspect of the invention, wherein the distillate fuel component has
improved thermal stability when compared to a distillate fuel
component produced in the same way but from a crude oil containing
an imine compound represented by the formula
R.sup.2--N.dbd.CH.sub.2, wherein R.sup.2 represents an alkyl group
having 10 or more carbon atoms, and/or an amine residue
thereof.
[0081] The present invention further provides an aviation turbine
fuel composition according to the sixth aspect of the invention,
wherein the aviation turbine fuel has improved thermal stability as
measured by ASTM D3241 when compared to an aviation turbine fuel
produced in the same way but from a crude oil containing an imine
compound represented by the formula R.sup.2--N.dbd.CH.sub.2,
wherein R.sup.2 represents an alkyl group having 10 or more carbon
atoms, and/or an amine residue thereof.
[0082] A seventh aspect of the present invention provides a method
of removing or lowering amounts of hydrogen sulfide present during
distillation of a crude oil to form a distillate fuel component
boiling in the kerosene range, the method comprising adding to the
crude oil an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, and distilling the crude oil to
form the distillate fuel component.
[0083] An eighth aspect of the present invention provides the use
of an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, to remove or lower the amount of
hydrogen sulfide in a crude oil.
[0084] A ninth aspect of the present invention provides the use of
an imine compound represented by the formula
R.sup.1--C(CH.sub.3).sub.2--N.dbd.CH.sub.2, wherein R.sup.1
represents a (1-5C)alkyl group, in the preparation of a distillate
fuel component boiling in the kerosene range.
[0085] For example, R.sup.1 may represent a methyl group or a 5C
alkyl group, more particularly R.sup.1 may represent a 5C alkyl
group.
[0086] The preferred features of the fourth, fifth, sixth, seventh,
eighth and ninth aspects are as defined in relation to the first,
second and third aspects.
BRIEF DESCRIPTION OF DRAWINGS
[0087] 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:
[0088] FIG. 1 shows the amine content found in distillation
fractions treated with Scavenger C in Example 1, with % w/w of the
Scavenger C on the y axis and the distillation fraction (in
.degree. C.) on the x axis;
[0089] FIG. 2 shows the amine content found in distillation
fractions treated with tert-octylamine in Example 1, with % w/w of
the tert-octylamine on the y axis and the distillation fraction (in
.degree. C.) on the x axis;
[0090] FIG. 3 shows the amine content found in distillation
fractions treated with Scavenger A in Example 1, with % w/w of the
Scavenger A on the y axis and the distillation fraction (in
.degree. C.) on the x axis;
[0091] FIG. 4 shows the amine content found in distillation
fractions treated with Primene 81R Amine in Example 1, with % w/w
of the Primene 81R on the y axis and the distillation fraction (in
.degree. C.) on the x axis;
[0092] FIG. 5 shows hydrogen sulfide scavenging efficiency for
Scavenger C according to Example 2, with the concentration of
hydrogen sulfide remaining (in mg/L) on the y axis and time (in
minutes) on the x axis; and
[0093] FIG. 6 shows hydrogen sulfide scavenging efficiency for
Scavenger C according to Example 3, with the concentration of
hydrogen sulfide remaining (in mg/L) on the y axis and time (in
minutes) on the x axis.
EXAMPLES
[0094] The invention will now be described with reference to the
following non-limiting examples.
[0095] Scavenger A is a terminal imine formed by the reaction of
Primene 81R Amine and formaldehyde (or paraformaldehyde) and is a
known commercial hydrogen sulfide scavenger. Primene 81R is a
primary aliphatic amine in which the amino nitrogen is linked to a
tertiary carbon and the total number of carbon atoms is in the
C12-C14 range. Thus Scavenger A is a compound of the formula
R.sup.2--N.dbd.CH.sub.2, wherein R.sup.2 represents an alkyl group
having 12-14 carbon atoms.
Preparative Example Scavenger A (Comparative)
[0096] Primene 81R amine (10 g, 50.3 mmol) was dissolved in toluene
(50 ml). Paraformaldehyde (1.81 g, 60.3 mmol) was added and the
mixture heated to reflux for 1 hour with a Dean Stark trap in place
to capture the water produced. After cooling to room temperature,
the organic phase was concentrated in vacuo to afford Scavenger A
(9.52 g, 45.1 mmol, 90%) as a yellow oil.
Preparative Example Scavenger C (Inventive; Tert-Octylimine)
[0097] Paraformaldehyde (0.94 g, 31.1 mmol) was added to in EtOAc
(20 ml) to form a suspension. tert-Octylamine (4.03 g, 31.1 mmol)
was added and the mixture stirred at room temperature for 1 hour,
then at 60.degree. C. for 1 hour. After cooling to room
temperature, the aqueous phase was separated and the organic phase
dried over MgSO.sub.4 and concentrated in vacuo to afford
tert-octylimine, Scavenger C (3.43 g, 24.3 mmol, 78%) as a
colourless oil.
Example 1: Distillation Profile of Nitrogen-Containing Oil
Additives
[0098] A mixture of diesel (100 ml), aviation turbine fuel (100 ml)
and gasoline (50 ml) was placed in a 500 ml round bottom flask. A
stirrer bar was added followed by an additive to be tested (0.3
ml). Distillation equipment, comprising a thermometer, water-cooled
condensing tube and receiver vessel were then attached to the round
bottom flask. The system was purged with nitrogen and heat was
applied to the round bottom flask while the contents were stirred.
Separate fuel distillation fractions were then collected based on
the temperature reading of the thermometer. Fractions collected
corresponded to the following temperature ranges 0-100.degree. C.,
100-120.degree. C., 120-140.degree. C., 140-160.degree. C.,
160-180.degree. C., 180-200.degree. C. The non-distilled residue
was collected and classed as the >200.degree. C. fraction. Each
fraction was then tested to determine the amine/nitrogen content.
Results are shown in FIGS. 1 to 4.
[0099] The Additives tested were: Scavenger C, tert-octylamine,
Scavenger A, and Primene 81R Amine.
[0100] FIGS. 1 and 2 show that Scavenger C and tert-octylamine (the
potential nitrogen-containing constituents present when treating
oil-products with Scavenger C) are found solely in the low
temperature (i.e. <200.degree. C.) distillation fractions.
Consequently, only a small amount of these materials would be
expected within higher temperature cuts. In contrast, Scavenger A
and Primene 81 R Amine (the potential nitrogen-containing
constituents present when treating oil-products with Scavenger A)
were found in all distillation fractions (see FIGS. 3 and 4).
Amines from Scavenger A and Primene 81 R Amine would therefore be
considerably more likely to be present within higher temperature
cuts, including those corresponding to aviation turbine fuel.
Example 2: Hydrogen Sulfide Scavenging Efficiency
[0101] Caromax 20 (20 ml) was placed into a reaction vessel
containing a stirrer bar and the system sealed. A stock solution of
Caromax 20/H.sub.2S (4 ml, about 525 mg/L H.sub.2S) was added to
the reaction vessel and the mixture heated to 75.degree. C. with
stirring. Once the temperature had stabilised the time=0 liquid
H.sub.2S content was determined (in mg H.sub.2S/L). Hydrogen
sulfide Scavenger C (415 mg/L) was then injected into the system
and the liquid H.sub.2S content determined at the following time
points after injection; 1, 5, 10, 20 and 30 minutes. The results
are shown in FIG. 5.
[0102] FIG. 5 shows that Scavenger C reduces the amount of hydrogen
sulfide in the system.
Example 3: Hydrogen Sulfide Scavenging Efficiency
[0103] Crude oil (20 ml) was placed into a reaction vessel
containing a stirrer bar and the system sealed. A stock solution of
Caromax 20/H2S (1.3 ml, about 525 mg/L H2S) was added to the
reaction vessel and the mixture heated to 49.degree. C. with
stirring. Once the temperature had stabilised the time=0 liquid H2S
content was determined (in mg H2S/L). Hydrogen sulfide Scavenger C
(525 mg/L) was then injected into the system and the liquid H2S
content determined at the following time points after injection; 1,
5, 10, 20 and 30 minutes. The results are shown in FIG. 6.
[0104] FIG. 6 shows that Scavenger C reduces the amount of hydrogen
sulfide in the system.
Example 4: Hydrogen Sulfide Scavenging Efficiency
[0105] A series of tests were performed to study the effectiveness
of Scavenger C. In these tests, 2 ml of a stock solution containing
0.6 mg/ml of Na.sub.2S in MeOH was added to 8 ml of Caromax and the
vessel sealed. Hydrogen sulfide was generated in situ by injecting
0.07 ml of 0.5M HCl (2 molar equivalents). Thus, the solution
contained approximately 50 mg/L of hydrogen sulfide. Scavenger C
was then injected in an amount as shown in Table 1. The mixture was
heated to 75.degree. C. for 30 minutes and then allowed to cool.
The presence of hydrogen sulfide remaining was assessed using a
colourimetric test which tests positive if >1 mg/L of hydrogen
sulfide is present. Thus, a positive test indicates a failure to
reduce the hydrogen sulfide concentration to <1 mg/L.
[0106] Multiple tests were performed over an extended period of
time (several weeks) using different batches of Scavenger C and the
results are summarised in Table 1.
TABLE-US-00001 TABLE 1 Amount of Total Scavenger C added number of
Molar Equivalents tests Passes Fails % pass 0.5 31 24 7 77 1.0 40
40 0 100 2.0 36 36 0 100 5.0 8 8 0 100 10.0 2 2 0 100 15.0 2 2 0
100
[0107] The results show that at treat rates at or above 1 mole of
Scavenger C per mole of hydrogen sulfide, all tests resulted in
hydrogen sulfide levels <1 mg/L.
* * * * *