U.S. patent application number 13/604742 was filed with the patent office on 2012-12-27 for process for the extraction of high molecular weight naphthenic acids from calcium naphthenate salts.
This patent application is currently assigned to EXXONMOBIL RESEARCH AND ENGINEERING COMPANY. Invention is credited to Sharon A. FEILLER, Manuel A. FRANCISCO, Steven W. LEVINE, Clifford C. WALTERS.
Application Number | 20120330057 13/604742 |
Document ID | / |
Family ID | 42267087 |
Filed Date | 2012-12-27 |
United States Patent
Application |
20120330057 |
Kind Code |
A1 |
LEVINE; Steven W. ; et
al. |
December 27, 2012 |
PROCESS FOR THE EXTRACTION OF HIGH MOLECULAR WEIGHT NAPHTHENIC
ACIDS FROM CALCIUM NAPHTHENATE SALTS
Abstract
A method for recovering high molecular weight naphthenic
tetra-acids, particularly ARN acids from a calcium naphthenate
deposit. Calcium naphthenate deposits contain large amounts of
calcium naphthenate salts of ARN acids. The method dual solvent
extraction process in which the naphthenic tetra-acids chemically
bound as calcium naphthenate salts are converted into free acid
monomers by an aqueous acid. The resulting free acid monomers are
then dissolved into an organic solvent phase and the counterions
dissolve in the aqueous acid phase. The naphthenic tetra-acids are
then recovered from the organic solvent phase.
Inventors: |
LEVINE; Steven W.;
(Flemington, NJ) ; FRANCISCO; Manuel A.;
(Phillipsburg, NJ) ; FEILLER; Sharon A.;
(Allentown, PA) ; WALTERS; Clifford C.; (Milford,
NJ) |
Assignee: |
EXXONMOBIL RESEARCH AND ENGINEERING
COMPANY
Annandale
NJ
|
Family ID: |
42267087 |
Appl. No.: |
13/604742 |
Filed: |
September 6, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12631177 |
Dec 4, 2009 |
|
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13604742 |
|
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61193791 |
Dec 23, 2008 |
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Current U.S.
Class: |
562/498 |
Current CPC
Class: |
C07C 51/02 20130101;
C07C 63/40 20130101; C07C 51/02 20130101 |
Class at
Publication: |
562/498 |
International
Class: |
C07C 55/26 20060101
C07C055/26 |
Claims
1. A naphthenic tetra-acid recovered from a dual solvent extraction
of a calcium naphthenate deposit, the extraction process
comprising: providing a calcium naphthenate deposit including a
calcium naphthenate salt of a naphthenic tetra-acid and entrained
crude oil; providing an aqueous solvent solution including an
aqueous acid and an organic solvent in a volumetric ratio effective
to dissociate the naphthenic tetra-acid and calcium salt; adding
the calcium naphthenate deposit to the aqueous solvent solution in
an effective mass ratio of solvent solution to deposit to form a
multiphase mixture; separating the multiphase mixture into a
plurality of phases including an aqueous acid phase and an organic
solvent phase; recovering the naphthenic tetra-acid from the
organic solvent phase.
2. The tetra-acid of claim 1, wherein the naphthenic tetra-acid is
an ARN acid.
3. The tetra-acid of claim 1, wherein the naphthenic tetra-acid has
a molecular weight ranging from about 1228 to about 1236 atomic
mass units (amu).
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 12/631,177, filed on Dec. 4, 2009, which
relates to and claims priority to U.S. Provisional Patent
Application No. 61/193,791, filed on Dec. 23, 2008.
FIELD
[0002] The disclosed subject matter relates to a process for the
extraction of high molecular weight naphthenic tetra-acids from
calcium naphthenate salts.
BACKGROUND
[0003] Naphthenic acids are carboxylic acids that occur in most
crude oils as trace components and in some, biodegraded oils in
significantly greater concentrations. Total acids in crude oils is
commonly semi-quantified by titration with KOH and expressed in
terms of total acid number (TAN). Conventional TAN measurements are
not precisely a measure of total acids in a crude oil, but a
measure of the amount of KOH needed to achieve the deflection
(neutralization) point. Accordingly, TAN is an approximation of the
amount of naphthenic acids. The acidity of high TAN oils may cause
emulsion and corrosion problems in both production and refining.
Solid deposits, recently identified as calcium naphthenates, can
result in substantial damage and lose of production.
[0004] Under certain conditions, the naphthenic acids present in
acidic crude oil will precipitate with Ca.sup.2+ ions that are
present in the co-produced water to form calcium naphthenate
solids. Other cations are involved to a lesser extent forming a
variety of metal naphthenates (e.g., ferrous iron and magnesium).
This solid precipitation accumulates predominantly in oil-water
separators and desalters, but naphthenates also can deposit in
subsea, topside, or surface facilities and pipelines.
[0005] A great deal of research has been pursued to characterize
the naphthenic acid responsible for the calcium deposits. It has
been recently determined that a specific family of high molecular
weight tetracarboxylic acids, termed ARN Acids, appears to be the
major constituent responsible for the calcium naphthenate deposits
(ARN is not an acronym, but is Old Norwegian for "eagle"). ARN
acids are high molecular weight molecules with four carboxylic acid
groups, each at the end of a long aliphatic chain, forming a
four-fingered molecule with polar tips. The ARN acids are a
specific family of .about.C.sub.80 tetracarboxylic acids. A
majority of the ARN acids have a molecular weight ranging from
about 1228 to about 1236 atomic mass units (amu) with one of the
main acids having a molecular weight of 1232 amu and a molecular
formula of C.sub.80H.sub.142O.sub.8. The ARN acids do not have an
aromatic or alkenes function present and quaternary carbons do not
exist. The ARN acids can have 4-8 sites of unsaturation (or 4-8
cyclopentyl rings) and are believed to be derived from archaeal
C.sub.80 lipids.
[0006] The proposed structure of the major ARN acid is
6:17,10:18,10':18',6'':17'',10'':18'',10'':18'')-hexacyclo-20-bis-16,16''-
-biphytane-1,1',1'',1'''-tetracarboxylic acid. The molecule
contains two biphytanyl diacids, each with three pentacyclic rings
joined together by a linkage at the C.sub.20 methyl groups, as
described in Lutnaes B. F., Brandal O., Sjoblom J., and Krane J.
(2006) Archaeal C.sub.80 isoprenoid tetraacids responsible for
naphthenate deposition in crude oil processing. Organic &
Biomolecular Chemistry 4, 616-620, incorporated by reference in its
entirety herein.
[0007] The structure of a representative archaeal C.sub.80
isoprenoid tetra-acid is:
##STR00001##
[0008] The four carboxylic acid groups afford the molecule
unusually high reactivity. These four carboxylic groups tend to
create polymeric salt when coordinated with divalent metal ions.
This woven polymeric-like structure yields a very sticky deposit
that hardens upon contact with air.
[0009] A method for selectively isolating carboxylic acids from
oils and calcium naphthenates using an Acid-Ion Exchange Resin
procedure has been described in Mediaas et al. (2003) The Acid IER
Method--a Method for Selective Isolation of Carboxylic Acids from
Crude Oils and Other Organic Solvents, Society of Petroleum
Engineers Paper 80404. The ion-exchange method is suitable when
dealing with cleaning up Ca-naphthenate precipitates as most of the
material is composed of ARNs. However, this method is likely not
suitable for industrial scale separation because the resins will
eventually foul with the associated hydrocarbons/aspahltenes.
Furthermore, the use of ion-exchange resins on an industrial scale
level may be cost prohibitive.
[0010] A need therefore exists for alternative and more efficient
and effective methods to isolate and extract high molecular weight
naphthenic tetra-acids from calcium naphthenate salts.
SUMMARY
[0011] The purpose and advantages of the disclosed subject matter
will be set forth in and apparent from the description that
follows, as well as will be learned by practice of the disclosed
subject matter. Additional advantages of the disclosed subject
matter will be realized and attained by the methods and systems
particularly pointed out in the written description and claims
hereof, as well as from the appended drawings.
[0012] To achieve these and other advantages and in accordance with
one aspect of the disclosed subject matter, as embodied and broadly
described, a method is provided for recovering high molecular
weight naphthenic tetra-acids, particularly ARN acids, from a
calcium naphthenate deposit. The naphthenic tetra-acid recovered
from such a method also is disclosed herein. Calcium naphthenate
deposits contain large amounts of calcium naphthenate salts of ARN
acids. The disclosed subject matter outlines a process to isolate
the ARN tetra-acids from the calcium naphthenate deposits that have
been recovered during upstream production of crude oils. The method
includes a dual solvent extraction process in which the naphthenic
tetra-acids chemically bound as calcium naphthenate salts are
converted into free acid monomers by an aqueous acid. The resulting
free acid monomers are then dissolved into an organic solvent phase
and the counterions dissolve in the aqueous acid phase. The
naphthenic tetra-acids are then recovered from the organic solvent
phase.
[0013] The method includes the steps of providing calcium
naphthenate deposits, the deposits including calcium naphthenate
salts of naphthenic tetra-acids and entrained crude oil, and
providing an aqueous solvent solution comprising an aqueous acid
and an organic solvent, the aqueous acid and the organic solvent
present in a volumetric ratio effective to dissociate the
naphthenic tetra-acids and calcium salt and allow the tetra-acids
to dissolve in the organic solvent. Preferably, the calcium
naphthenate deposit is finely ground to a powder. The method
further includes adding the calcium naphthenate deposit to the
aqueous solvent solution in an effective mass ratio of aqueous
solvent solution to calcium naphthenate deposit to form a
multiphase mixture; separating the multiphase mixture into a
plurality of phases including an aqueous acids phase and an organic
solvent phase; and recovering the naphthenic tetra-acids from the
organic solvent phase. Preferably, recovering the naphthenic
tetra-acids from the organic solvent phase includes evaporation of
the organic solvent. In accordance with one embodiment, the
multiphase mixture can be filtered to remove solids.
[0014] In accordance with a preferred embodiment, following the
initial separation of the aqueous acid phase and the organic
solvent phase and prior to the recovery step, the aqueous acid
phase is washed with an effective amount of additional organic
solvent to dissolve any additional tetra-acids that are present in
the aqueous phase into the organic solvent. The aqueous phase and
the organic solvent phase are then separated and the organic
solvent phase is combined with the organic solvent phase from the
previous separation.
[0015] In addition, in order to remove any water present in the
organic phase prior to the recovery step, the combined organic
solvent layers or phases can be dried using a chemical drying
agent, which can then be removed by filtration.
[0016] In accordance with a preferred embodiment, the aqueous acid
is hydrochloric acid and the organic solvent is methylene chloride.
In accordance with one embodiment, the drying agent is anhydrous
sodium sulfate.
[0017] In accordance with one embodiment, the aqueous solvent
solution includes a volumetric solution of 1:1 of the aqueous acid
to the organic solvent. Preferably, the effective mass ratio of
aqueous solvent solution to calcium naphthenate deposit is at least
40:1.
[0018] In accordance with another embodiment, the calcium
naphthenate deposits occur from the production of a crude oil,
wherein the crude oil is a high-neutralization number (HNN) crude
oil.
[0019] According to another aspect, the disclosed subject matter
includes multi-step, dual solvent extraction process in which the
naphthenic tetra-acids chemically bound as calcium naphthenate
salts are converted into free acid monomers by an aqueous acid. The
resulting free acid monomers are then dissolved into an organic
solvent phase and the counterions dissolve in the aqueous acid
phase. The naphthenic tetra-acids are then recovered from the
organic solvent phase.
[0020] These and other features of the disclosed subject matter
will become apparent from the following detailed description of
preferred embodiments which, taken in conjunction with the
accompanying drawings, illustrate by way of example the principles
of the disclosed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The disclosed subject matter will now be described in
conjunction with the accompanying drawings in which:
[0022] FIG. 1 is a schematic flow diagram depicting one embodiment
of the disclosed subject matter;
[0023] FIG. 2 is a graph illustrating an infrared spectroscopy scan
of naphthenic tetra-acids recovered from calcium naphthenate
deposits in accordance with the disclosed subject matter; and
[0024] FIG. 3 is a graph illustrating an infrared spectroscopy scan
of the carboxylic acid region for the concentrated naphthenic
tetra-acids extracted, the entrained crude and the aqueous acid
phase from the extraction.
DETAILED DESCRIPTION
[0025] Reference will now be made in detail to the various aspects
of the disclosed subject matter. The method and corresponding steps
of the disclosed subject matter will be described in conjunction
with the figures and examples provided herein.
[0026] A method for recovering high molecular weight naphthenic
tetra-acids, particularly ARN acids, from a calcium naphthenate
deposit is provided. Calcium naphthenate deposits contain large
amounts of calcium naphthenate salts of tetra-acids. A process is
disclosed to isolate the tetra-acids from the calcium naphthenate
deposits, which have been recovered during upstream production of
crude oils. The method includes a multi-step, dual solvent
extraction process in which the naphthenic tetra-acids chemically
bound as calcium naphthenate salts are converted into free acid
monomers by an aqueous acid. The resulting free acid monomers are
then dissolved into an organic solvent phase and the counterions
dissolve in the aqueous acid phase. The naphthenic tetra-acids are
then recovered from the organic solvent phase.
[0027] Generally, the method includes the steps of providing
calcium naphthenate deposits, the deposits including calcium
naphthenate salts of naphthenic tetra-acids and entrained crude oil
and providing an aqueous solvent solution comprising an aqueous
acid and an organic solvent, the aqueous acid and the organic
solvent present in a volumetric ratio effective to dissociate the
naphthenic tetra-acid and calcium salt and allow the tetra-acid to
dissolve in the organic solvent. The method further includes adding
the calcium naphthenate deposit to the aqueous solvent solution in
an effective mass ratio of aqueous solvent solution to calcium
naphthenate deposit to form a multiphase mixture; separating the
multiphase mixture into a plurality of phases including an aqueous
acids phase and an organic solvent phase; and recovering the
naphthenic tetra-acids from the organic solvent phase. Preferably,
recovering the naphthenic tetra-acids from the organic solvent
phase includes evaporation of the organic solvent. In accordance
with one embodiment, the multiphase mixture can be filtered to
remove solids.
[0028] The extraction process described herein can be conducted as
a batch, continuous or semi-continuous system. Preferably, the
system should be conducted to maximize intimate contacts between
the naphthenates salts-naphthenic acids and the solvent system.
Suitable mixing devices would be those typically used for
solid-liquid blending, such as mixing tanks, baffle mixers, mixing
valves and the like.
[0029] For purpose of illustration and not limitation the method is
depicted schematically in FIG. 1. The method described herein
includes a semi-continuous or continuous process embodiment of the
disclosed process. The process includes providing calcium
naphthenate deposits 10, the deposits comprised of calcium
naphthenate salts of naphthenic tetra-acids and entrained crude
oil. Preferably, the deposits are finely ground into a powder. The
method further includes providing an aqueous solvent solution
comprising an aqueous acid 20 and an organic solvent 30. The
aqueous acid 20 and the organic solvent 30 are fed to an
extraction-mixing device 35, for example, a mixing tank. The
aqueous acid and the organic solvent are present in a volumetric
ratio in an amount that is effective to dissociate the naphthenic
tetra-acid and calcium salt and allow the tetra-acid to dissolve in
the organic solvent. Typically, the extraction is conducted using a
volume ratio of the aqueous acid solvent to the organic solvent in
the range of 1 to 500 parts by volume of aqueous acid solvent per
part by volume of organic solvent. However it shall be understood
by those skilled in the art that any suitable ratio can be used
which is effective is dissociating the tetra-acids and calcium
salts and allowing the tetra-acids to dissolve in the organic
solvent.
[0030] In one embodiment, the solvents 20, 30 are initially fed to
the mixing device, the device is continuously stirred and after a
predetermined time, the deposits 10 are added to the solvent
solution as the multiphase mixture continues to be stirred. In an
alternative embodiment, the calcium naphthenate deposit 10 is added
simultaneously with the solvents 20, 30 to the mixing device
35.
[0031] Generally, the extraction is conducted using a weight ratio
of total aqueous solvent solution to calcium naphthenate deposits
in the range of about from 1 to 500 parts by weight of total
solvent solution per part by weight of calcium naphthenate
deposits. Typically, the extraction is conducted at temperatures
that are solvent specific where the lower temperature is limited by
the melting point of the solvent.
[0032] Suitable mixing devices 35 which can be used include, for
example, mixing tanks, baffle mixers, mixing valves and the like.
The length of time that the solvent solution and deposits are mixed
generally ranges from 1 minute to 1 day, depending upon the mixing
conditions. It shall be understood that optimum mixing or contact
times will vary with the efficiency of the particular mixing device
used and can be determined by routine procedures. If any solids are
present in the mixing tank, the solids are removed as bottoms
product 40 from the mixing device. When all of the calcium
naphthenates are dissolved in the acid, the solids can include acid
insoluble inorganic salts, oxides, and metals.
[0033] The aqueous acid and organic extraction solvents are
immiscible and, accordingly, can be separated from each other by
allowing the mixture to settle into two phases and then separating
the two phases by any suitable procedure. The aqueous solvent
mixture and dissociated and dissolved deposits 50 can be fed from
the mixing device 35 to the phase separation vessel 55, for example
a settling tank. The total mixture is then allowed to separate. The
separation can be achieved using gravity settling, electrostatic
field separation, centrifugation or a combination thereof. The
bottoms organic solvent 70, which contains the dissolved
tetra-acids is discharged to the final separator 75 and the upper
aqueous acid 60 is fed to another separation vessel 65. If any
residual sediment is present in the separation vessel 65, the
sediment can be removed using conventional filtration techniques
and processes.
[0034] In separation vessel 65, additional organic solvent 80 is
added to upper aqueous acid. The organic solvent is preferably
identical to the first organic solvent 30 used in the initial
mixing device 35. The dual solvent mixture comprising aqueous acid
and organic solvent are allowed to separate and the bottoms organic
solvent phase 100 is fed to the final separator 75. The upper
aqueous acid 90 is discharged from separation vessel 65 as is or
can be subjected to further processing, including, but not limited
to recycling.
[0035] Although only two separation vessels are depicted in FIG. 1,
it shall be understood that any number of additional separation
vessels can be used for additional washing of the aqueous acid
layer with organic solvent to dissolve further any acids present in
the aqueous layer into the organic solvent. The organic solvent
phases from any additional separation steps that may be included
are all collected and fed to the final vessel 75.
[0036] If any water is present, the organic solvent layers can be
dried using a suitable chemical drying agent 110. The chemical
drying agent is allowed to contact the organic solvent layer for a
predetermined time and temperature. The chemical drying agent is
then removed, typically by filtration. Suitable chemical drying
agents to remove water in the extracted organic phase include, but
are not limited to anhydrous sodium sulfate, gypsum (calcium
sulfate), calcium chloride, or silica gel.
[0037] Following the drying step, the naphthenic tetra-acids
products are then recovered from the organic solvent phase. The
organic solvent is typically removed by distillation and/or
evaporation techniques using conventional devices and processes,
including but not limited to rotary evaporation, atmospheric
evaporation, centrifugal evaporation, hot plate evaporation under
nitrogen-purge, or RapidVap vacuum evaporation systems.
[0038] In accordance with the disclosed subject matter, the final
material isolated via dual solvent extraction process is the high
molecular weight naphthenic tetra-acids, particularly the ARN
tetra-acids. The material isolated 120 comprises the naphthenic
tetra-acids in addition to a relatively small amount of entrained
crude oil. The addition of the isolated naphthenic tetra-acids 120
to crude oil is effective in reducing or preventing fouling in a
refinery component, as described in copending U.S. Provisional
Patent Application No. 61/193,621 filed on Dec. 11, 2008.
[0039] In accordance with yet another embodiment, the entrained
crude within the calcium naphthenate deposits can be quantified
using a second extraction process on the solid calcium naphthenate
deposits. The process (not illustrated) for quantifying the
entrained crude includes grinding the deposits to a powder, adding
the powdered solids to a Soxhelt thimble and extracting with
toluene for approximately 20 hours. The extracts from the toluene,
which are the entrained crude, are extracted to dryness and
weighed.
[0040] In accordance with one embodiment, the aqueous acid includes
any compound which can covert the naphthenic acids chemically bound
as naphthenate to free acid monomers which dissolve into the
organic solvent, leaving the counter ions in the aqueous acid
phase. Suitable aqueous acids include, but are not limited to,
hydrochloric, sulfuric, nitric, acetic, or phosphoric acid. In a
preferred embodiment, the aqueous acid includes hydrochloric
acid.
[0041] For purpose of illustration and not limitation, the organic
solvent includes any suitable compound in which the naphthenic
tetra-acids dissolve. Suitable organic solvents include, but are
not limited to, alkyl halides, light aromatic hydrocarbons, or
light hydrocarbon-light alcohol mixtures. In a preferred
embodiment, the organic solvent is methylene chloride.
[0042] Generally, the dual solvent extraction process described
herein is effective in extracting the high molecular weight
naphthenic tetra-acids at purity ranging from about 10% to about
100% with a yield on the deposits ranging from about 10% to about
100%. As illustrated in FIG. 2, for purpose of illustration and not
limitation, an infra-red scan of the extracted acid product
indicates the presence of carboxylic acids, demonstrating a
successful isolation of the ARN tetra-acids in the calcium
naphthenate deposits using the process describe herein.
[0043] In accordance with one embodiment, the extracted product
includes high molecular weight naphthenic tetra-acids, which are
molecules having four carboxylic acid groups, each at the end of a
long aliphatic chain, forming a four-fingered molecule with polar
tips. In accordance with one embodiment, the high molecular weight
naphthenic tetra-acid has an atomic molecular weight great than
1230 atomic mass units (amu).
[0044] In accordance with a preferred embodiment of the disclosed
subject matter, the high molecular weight naphthenic tetra-acids
which are extracted from the calcium naphthenate deposits are ARN
acids. ARN acids are a specific family of .about.C.sub.80-C.sub.81
tetracarboxylic acids. A majority of the ARN acids have a molecular
weight ranging from about 1228 to about 1236 atomic mass units
(amu) with one of the main acids having a molecular weight of 1232
amu. The ARN acids do not have an aromatic or alkenes function
present and quaternary carbons do not exist. The ARN acids can have
4-8 sites of unsaturation (or 4-8 cyclopentyl rings).
[0045] In accordance with one embodiment, the ARN acid extracted is
the archaeal C.sub.80 isoprenoid, whose empirical formula is
C.sub.80H.sub.142O.sub.8 and whose structure is
6:17,10:18,10':18',6'':17'',10'':18'',10'':18'')-hexacyclo-20-bis-16,16''-
-biphytane-1,1',1'',1'''-tetracarboxylic acid. This C.sub.80
isoprenoid molecule contains two biphytanyl diacids, each with
three pentacyclic rings joined together by a linkage at the
C.sub.20 methyl groups and its structure is represented by:
##STR00002##
[0046] Therefore, in accordance with the disclosed subject matter,
the high molecular weight naphthenic tetra-acids are extracted from
the calcium naphthenate deposits, the deposits including high
molecular weight naphthenic tetra-acid calcium salts. Typically,
calcium naphthenate deposits occur during the production of high
neutralization number (HNN) crude oils.
[0047] While a particular form of the disclosed subject matter has
been described, it will be apparent to those skilled in the art
that various modifications can be made without departing from the
spirit and scope of the disclosed subject matter.
EXAMPLES
[0048] The present application is further described by means of the
examples, presented below. The use of such examples is illustrative
only and in no way limits the scope and meaning of the disclosed
subject matter or of any exemplified term.
Example 1
[0049] In this example, high molecular weight naphthenic
tetra-acids were extracted from solid calcium naphthenate deposits.
The extraction process of this example is an example of a batch
application of the disclosed process.
[0050] Solid calcium naphthenate deposits were finely ground into a
powder using a mechanical grinder. An aqueous solvent solution was
prepared, the solution including 1M aqueous hydrochloric acid and
methylene chloride solvent in a 1:1 ratio by volume. The solution
was placed into a mixing device and continuously stirred. The
ground deposit was then added to the solvent solution at a 40:1
total solvent solution to solid deposit ratio, and the total
mixture of solvent and solids was stirred overnight at room
temperature. The total mixture was then filtered and the filtered
solids were dried. When all of the calcium naphthenates are
dissolved in the acid, the solids can include acid insoluble
inorganic salts, oxides, and metals. The solvent solution including
aqueous hydrochloric acid and methylene chloride were allowed to
separate into a multiphase mixture including the aqueous acid
layer, the organic solvent layer and solids. The entire mixture was
suction filtered and the filtered solids were dried and weighed.
When all of the calcium naphthenates are dissolved in the acid, the
solids can include acid insoluble inorganic salts, oxides, and
metals. The hydrochloric acid phase and the methylene chloride
phase were then separately withdrawn. The aqueous hydrochloric acid
phase was washed twice with small amounts of additional methylene
chloride solvent and the washes were combined with the extract from
the initial methylene chloride phase. The combined methylene
chloride layers were then dried over anhydrous sodium sulfate
overnight and recovered by filtration. The acid concentrate product
was then recovered by evaporation of the methylene chloride solvent
and weighed.
[0051] The final material isolated was the high molecular weight
naphthenic tetra-acids concentrate. This extracted material
contains the tetra-acids obtained from the calcium salts in
addition to some entrained crude oil. As illustrated in FIG. 1, an
infra-red (IR) scan of the ARN concentrate strongly indicates the
presence of carboxylic acids, demonstrating a successful isolation
(concentration) of the tetra-acids in the upstream deposit. The raw
weight measurements from the Experiment are tabulated in Table
1.
TABLE-US-00001 TABLE 1 Weight Measurements from Example 1 Weight
(g) Experimental Starting Weight (g) 5 Upstream calcium naphthenate
deposits Residual (g) 1.2 Extracted Weight (g) 1.7 Extraction with
Methylene Chloride and 1M HCL
Example 2
[0052] In this example, the entrained crude within the sample was
quantified by conducting a second extraction on the solid
naphthenate deposits. First, 5 grams of deposits were finely ground
into a powder. The powdered solids were added to a Soxhlet
cellulose thimble and extract overnight with toluene. The extracted
solids were then dried and weighed and any residual toluene was
removed by rotary evaporation. The extracted material is the
entrained crude. The raw weight measurements from the Experiment
are tabulated in Table 2.
TABLE-US-00002 TABLE 2 Weight Measurements from Example 2 Weight
(g) Experimental Starting Weight (g) 5.00 Entrained Crude (Soxhlet)
(g) 0.8 Soxhlet ran for 24 hours with Toluene
[0053] Infra-red (IR) scans were conducted for: i) the extracted
high molecular weight naphthenic tetra-acids concentrate, ii) the
aqueous hydrochloric acid phase (From Example 1) in addition to
iii) the entrained crude. FIG. 3 illustrates the carboxylic acid
region of the IR scan. As illustrated in FIG. 3, the entrained
crude illustrates some carboxylic acid presence but confirms that
the aqueous phase is essentially free of carboxylic acids.
[0054] From the two extractions performed in Examples 1 and 2, it
is possible to calculate the compositions of both the original
deposits and the concentrated ARN extract and the yields. The
composition of the solid calcium naphthenate deposits as well as
the yields are tabulated in Table 3. In the table, S is solids, A
is ARN acids, C is calcium and other aqueous-soluble materials, and
E is entrained oil. As illustrated in Table 3, the process
described herein was able to extract the high molecular weight
naphthenic tetra-acids, particularly ARN acids, at a purity of 53
percent with an 18 percent yield on the deposits by weight.
TABLE-US-00003 TABLE 3 Calculated Compositions and Yields from Two
Extraction Experiments Solid Calcium Naphthenate Deposits,
Composition Extraction balance Solids S 24% Organics (ARN +
Entrained Oil) (A + E) 34% Aqueous (Ca) (by difference) C 42%
Soxhlet balance Entrained Oil E 16% Soxhlet Solids (S + C + A) 84%
Yields ARN yield A = (A + E) - E 18% Extraction ARN purity A/(A +
E) 53%
[0055] While the disclosed subject matter has been described with
reference to one or more particular embodiments, those skilled in
the art will recognize that many changes can be made thereto
without departing from the spirit and scope of the disclosed
subject matter. Each of these embodiments and obvious variations
thereof is contemplated as falling within the spirit and scope of
the claimed disclosed subject matter, which is set forth in the
following claims. The disclosed subject matter is therefore to be
limited only by the terms of the appended claims along with the
full scope of equivalents to which the claims are entitled.
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