U.S. patent application number 12/342594 was filed with the patent office on 2010-06-24 for treatment of hydrocarbons containing acids.
This patent application is currently assigned to HER MAJESTY THE QUEEN IN RIGHT OF CANADA AS REPRESENTED. Invention is credited to Jan CZARNECKI, Lianhui DING, Rahimi PARVIZ, Hong YANG.
Application Number | 20100155304 12/342594 |
Document ID | / |
Family ID | 42264494 |
Filed Date | 2010-06-24 |
United States Patent
Application |
20100155304 |
Kind Code |
A1 |
DING; Lianhui ; et
al. |
June 24, 2010 |
TREATMENT OF HYDROCARBONS CONTAINING ACIDS
Abstract
The invention relates to a method of treating a liquid
hydrocarbon (e.g. heavy oil, bitumen, etc.) containing naphthenic
acids or other corrosive acids in order to partially or fully
convert such acids into non-corrosive compounds. The method
comprises adding an alkylating agent to the hydrocarbon, bringing
the hydrocarbon into contact with an aqueous liquid containing an
alkaline compound and a phase transfer catalyst to form an
immiscible two-phase system, maintaining the contact to allow
conversion of the naphthenic acids to non-corrosive oil-soluble
esters, and separating the aqueous phase from the liquid
hydrocarbon. Naphthenic acids are highly corrosive to plant and
equipment and the method enables them to be converted to
non-corrosive compounds in an economic manner.
Inventors: |
DING; Lianhui; (Edmonton,
CA) ; YANG; Hong; (Naperville, IL) ; PARVIZ;
Rahimi; (Edmonton, CA) ; CZARNECKI; Jan;
(Edmonton, CA) |
Correspondence
Address: |
KIRBY EADES GALE BAKER
BOX 3432, STATION D
OTTAWA
ON
K1P 6N9
CA
|
Assignee: |
HER MAJESTY THE QUEEN IN RIGHT OF
CANADA AS REPRESENTED
Ottawa
CA
BY THE MINISTER OF NATURAL RESOURCES CANADA
|
Family ID: |
42264494 |
Appl. No.: |
12/342594 |
Filed: |
December 23, 2008 |
Current U.S.
Class: |
208/263 |
Current CPC
Class: |
C10G 19/02 20130101;
C10G 75/02 20130101 |
Class at
Publication: |
208/263 |
International
Class: |
C10G 17/00 20060101
C10G017/00 |
Claims
1. A method of treating a liquid hydrocarbon containing acids to
reduce corrosive properties thereof, which method comprises
bringing the hydrocarbon into contact with an aqueous liquid
containing an alkaline compound and a phase transfer catalyst in
the presence of an alkylating agent to form a two-phase system,
maintaining the contact to allow conversion of the acids to
non-corrosive oil-soluble esters, and separating the aqueous phase
from the liquid hydrocarbon.
2. The method of claim 1, wherein the hydrocarbon is naturally
occurring and said acids are naphthenic acids.
3. The method of claim 2, wherein said hydrocarbon is selected from
the group consisting of bitumen, heavy oil, whole crude, topped
crude and distillates thereof.
4. The method of claim 1, wherein the phase transfer catalyst has
the formula: [XR.sup.1R.sup.2R.sup.3R.sup.4]Y wherein: X is N or P
(and most preferably N); Y is Cl, Br, I or OH; and R.sup.1,
R.sup.2, R.sup.3 and R.sup.4 may be the same or different and each
represents an alkyl group having a carbon number in the range of 1
to 20.
5. The method of claim 1, wherein the phase transfer catalyst is a
tetraalkylammonium compound.
6. The method of claim 1, wherein the catalyst is selected from the
group consisting of tetrabutylammonium bromide and
tributylhexadecaylammonium bromide.
7. The method of claim 1, wherein the alkylating agent is an alkyl
halide.
8. The method of claim 1, wherein the alkylating agent is an
alcohol other than methanol.
9. The method of claim 1, wherein said hydrocarbon is maintained at
a temperature of 0 to 120.degree. C. during said contact.
10. The method of claim 1, wherein said hydrocarbon is maintained
at a temperature of 40 to 90.degree. C. during said contact.
11. The method of claim 1, wherein said contact is maintained under
atmospheric pressure.
12. The method of claim 1, wherein said contact is maintained for a
period of time in a range of 10 to 240 minutes.
13. The method of claim 1, wherein said contact is maintained for a
period of time in a range of 30 to 120 minutes.
14. The method of claim 1, wherein the hydrocarbon and aqueous
liquid are agitated during said contact.
15. The method of claim 1, wherein the alkaline compound is
selected from the group consisting of NaOH, KOH, Ca(OH).sub.2,
ammonium hydroxide and mixtures thereof.
16. The method of claim 1, wherein the alkaline compound is used at
a concentration up to 1.0 M.
17. The method of claim 1, wherein the alkaline compound is used at
a concentration in a range of 0.001 to 1.0 M.
18. The method of claim 1, wherein the catalyst is used in an
amount in a range of 0.05 to 10 wt. % of the aqueous phase.
19. The method of claim 1, wherein a molar ratio of the alkylating
agent to the acids is 1-10:1.
20. The method of claim 1, wherein said alkaline liquid is used in
an amount of 1 to 20 volume % of the total amount of said
hydrocarbon and aqueous liquid.
Description
BACKGROUND OF THE INVENTION
[0001] (1) Field of the Invention
[0002] This invention relates to the treatment of hydrocarbons,
such as crude oil, bitumen, distillates, organic solvents, etc.,
containing corrosive acids. More particularly, although not
exclusively, the invention relates to the treatment of hydrocarbons
derived from natural sources containing naphthenic acids.
[0003] (2) Description of the Related Art
[0004] Naphthenic acids (NAs) occur naturally in crude oils,
especially heavy crude oils and bitumens. The amount of acid in a
hydrocarbon of this kind is usually represented by the Total Acid
Number (TAN). The presence of naphthenic acids in such hydrocarbons
is disadvantageous because they cause severe corrosion problems in
refinery equipment, transfer pipelines, and the like. Moreover,
naphthenic acids act as surfactants and disadvantageously stabilize
emulsions when the hydrocarbons are contacted with water, e.g.
during desalting operations. Removing naphthenic acids or
significantly reducing their concentration is therefore important
for heavy oil upgrading and other procedures carried out on
hydrocarbons. The most common industrial practices for such
treatment rely either on dilution of the hydrocarbons with low
naphthenic acid feeds, thereby reducing the average TAN value of
the mixture, or on a caustic washing process to convert the acids
to salts and thereby neutralizing and removing the acids. Each of
these methods has some disadvantages. For example, although the
process of blending a high TAN crude oil with a low TAN crude oil
can reduce the concentration of naphthenic acids in the blend to an
acceptable level, the acidic compounds are still present, and the
low TAN crude oil component is reduced in value as its level of TAN
is actually increased. Furthermore, the quality of crude oil is
deteriorating in general nowadays, so it will be more difficult in
the future to find enough low TAN crude oil to use as blending
components. On the other hand, while caustic treatments can
substantially remove naphthenic acids, the procedure generates
substantial amounts of waste water and results in the formation of
emulsions that are difficult and expensive to treat.
[0005] There have been proposals for dealing with naphthenic acids
in these and other ways. These generally fall into six categories,
as summarized in the following.
[0006] (1) Catalytic Hydrogenation.
[0007] In catalytic hydrogenation, the naphthenic acids are removed
by conversion to CO.sub.2 and H.sub.2O by the hydrogenation of
heavy oils under high temperature and pressure in the presence of a
hydrogenation catalyst. However, capital costs are high because of
the required high pressures and temperatures, and hydrogen is
expensive. In order to attain the required reaction temperature,
the heavy oils have to be heated in a furnace or by heat-exchangers
and the naphthenic acids in the oils will cause corrosion of such
equipment.
[0008] (2) Catalytic or Thermal Decarboxylation.
[0009] This method has drawbacks similar to those of catalytic
hydrogenation. In fact, the reaction temperatures required are
higher than those required for the hydrogenation reactions.
Decarboxylation catalysts also often have poor stability.
[0010] (3) Neutralization With Alkaline Aqueous Solutions.
[0011] As well as the problems discussed above (e.g. the formation
of stable emulsions), the naphthenic acids are converted to salts
(naphthenates) and transferred to the aqueous phase. The oil yield
decreases in consequence and the naphthenates in the aqueous phase
must be treated further (recovered or converted), which is
difficult and costly. An example of such a process is disclosed in
PCT patent publication WO 01/79386 published on Oct. 25, 2001 to
Mark Greaney. This publication discloses a process of reducing
naphthenic acid content of crude oils in the presence of an aqueous
base and a phase transfer agent at elevated temperature and
pressure to produce water-soluble naphthenate salts. Other such
processes are disclosed in U.S. Pat. No. 6,627,069 issued to Mark
Alan Greaney on Sep. 30, 2003 and PCT patent publication WO
00/75262 published on Dec. 14, 2000 to Collins et al.
[0012] (4) Extraction With Tetraalkylammonium Salts, Amines or
Other Extractants.
[0013] This method has the same drawbacks as the neutralization
method because the naphthenic acids are converted to other
compounds and removed.
[0014] (5) Esterification With Alcohols in the Presence of
Catalysts.
[0015] This method requires homogenous or heterogeneous catalysts.
The separation of homogeneous catalysts from the products is
generally very difficult, and remaining catalyst may lead to many
other unwanted side reactions. Also, by this method, the conversion
of naphthenic acids is very low if the water produced by the
esterification reaction cannot be removed from the reaction system
(the presence of water so-produced inhibits the conversion).
[0016] (6) Other Processes
[0017] U.S. Pat. No. 5,683,626 which issued to Sartori et al. on
Nov. 4, 1997, for example, discloses a process in which crude oil
is contacted with a neutralizing amount of tetraalkylammonium
hydroxide to produce naphthenic esters. However, the oil has to be
heated to a temperature in the range of 50 to 350.degree. C. for
many hours.
[0018] Due to the corrosion potential of naphthenic acids, it is
desirable to remove the acids at the location where the
hydrocarbons are initially obtained, but this is often difficult
with at least some of the above methods because it is uneconomic to
provide suitable equipment in the inaccessible or remote locations
where crude oils bitumens are often found.
[0019] Despite the various known approaches to the problem, there
is therefore still a need for an improved method of dealing with
naphthenic acids present in hydrocarbons such as heavy oils and
bitumen.
BRIEF SUMMARY OF THE INVENTION
[0020] According to one exemplary embodiment of the present
invention, there is provided a method of treating a liquid
hydrocarbon containing acids, which comprises bringing the
hydrocarbon into contact with an aqueous liquid containing an
alkaline compound and a phase transfer catalyst in the presence of
an alkylating agent to form a two-phase system, maintaining the
contact to allow conversion of the acids to non-corrosive
oil-soluble esters, and separating the aqueous phase from the
liquid hydrocarbon. The alkylating agent is preferably added to the
hydrocarbon before or simultaneously with the contact with the
aqueous liquid.
[0021] The acids in the hydrocarbons are generally those referred
to as naphthenic acids when the hydrocarbons are naturally
occurring (i.e. originally derived from naturally-formed geological
reservoirs and often referred to as "fossil fuels"). However, the
process may be used for removing organic acids of other kinds from
water-immiscible hydrocarbons in general, including man-made or
recycled hydrocarbons such organic solvents. Most preferably, the
method is applied to naphthenic acid-containing bitumen, heavy oil,
whole crude or topped crude, and distillates from the bitumen or
crude or from secondary processes. Bitumen may contain other
components, such as fines and asphaltenes, and may then be
difficult to treat efficiently. To overcome this problem, bitumen
may first be diluted with a solvent or light fraction (e.g.
naphtha) to reduce its viscosity.
[0022] The method may be applied to hydrocarbons having any TAN
value above zero. Usually, the TAN value in crude oils is greater
than 0.5. In sidestreams considered to be corrosive, the TAN value
is often greater than 1.5. Clearly, only hydrocarbons considered to
be corrosive (in their present form or after subsequent treatment)
need to be subjected to the method of the exemplary
embodiments.
[0023] The alkylating agent is preferably an alkyl halide
(preferably a bromide or a chloride) or an alcohol. The alkylating
agent should preferably have some degree of oil solubility so that
it can be continuously transferred to the oil phase as the agent is
consumed by the esterification reaction. If the oil solubility is
low, the rate of reaction may be slow. Therefore, when using
choosing water soluble alklyating agents, e.g. lower alcohols,
those having a low carbon number (e.g. methanol) should preferably
be avoided.
[0024] The molar ratio of the alkylating agent to the acid (e.g. as
calculated from the TAN) is preferably in a range of 1-10:1.
[0025] The alkaline compound used in the method is preferably a
base selected from NaOH, KOH, Ca(OH).sub.2, ammonium hydroxide, and
mixtures thereof, but other bases could possibly be employed. The
concentration of the alkaline compound in the aqueous solution is
preferably 0.001-1.0 M.
[0026] The phase transfer catalyst is preferably a compound having
the formula:
[XR.sup.1R.sup.2R.sup.3R.sup.4]Y
[0027] wherein: X is N or P (and most preferably N); [0028] Y is
Cl, Br, I or OH (most preferably Br); and [0029] R.sup.1, R.sup.2,
R.sup.3 and R.sup.4 may be the same or different and each
represents an alkyl group having a carbon number in the range of 1
to 20.
[0030] Examples of suitable phase transfer catalysts of this kind
include cetyltrimethyl ammoninum bromide (CTAB), didodecyltrimethyl
ammonium bromide, tetrabutylammonium bromide, tetrapentylammonium
bromide and tributylhexadecaylammonium bromide.
[0031] Phase transfer catalysts of this kind may be readily
obtained from commercial sources, such as for example PTC Organics
Inc. of New Jersey, USA, or Sigma-Aldrich of St. Louis, Mo.,
USA.
[0032] The catalyst is preferably used in an effective amount
normally in the range of 0.05 to 10 wt. % of the aqueous phase.
[0033] The reactants are preferably stirred during the reaction to
achieve a good mixing of the hydrocarbon and aqueous phases. This
may be carried out by bringing the phases together in a stirred
tank or similar agitated vessel. The stirring speed may determine
the mass transfer, so the higher the speed is, the better. The
method may be continuous or carried out in batches of any
convenient size. Since emulsions are not generally formed to any
substantial extent, the aqueous phase may be separated from the oil
phase after the reaction is complete simply by allowing the mixture
to stand until two discrete layers are formed, and then decanting
or drawing off one layer from the other. If necessary or desirable,
a centrifuge may be used for the separation.
[0034] The method is generally carried out at mild temperature,
e.g. below 120.degree. C. and more preferably below 100.degree. C.
A preferred temperature range is 30 to 100.degree. C., and more
preferably 40 to 90.degree. C. However, the reaction may be carried
out at ambient temperatures (such as 5.degree. C. to 35.degree. C.)
or at room temperatures (such as 15 to 25.degree. C.) so that no
heating equipment may be required.
[0035] As the reaction takes place in liquid phases, pressure is
not usually relevant and the method may be carried out at
atmospheric pressure.
[0036] The time required for the reaction is preferably 10-240
minutes, and more preferably 30-120 minutes. Longer periods of time
may be employed, but are generally not required.
[0037] As the method requires a simple operation under mild
conditions, and may be carried out in simple apparatus (stirred
tanks, and the like), it may be used to remove naphthenic acids
from hydrocarbons in remote locations where the hydrocarbons are
first collected. This minimizes or eliminates corrosion in
down-stream plant and equipment.
Definitions
[0038] The term "naphthenic acids" as used herein refers
generically to the acids found in naturally-occurring hydrocarbons
such as crude oil, bitumen, etc. These acids are usually an
unspecific mixture of several cyclopentyl and cyclohexyl carboxylic
acids with molecular weight of 120 to well over 700 atomic units.
The main fraction are often carboxylic acids with a carbon backbone
of 9 to 20 carbons.
[0039] The term "TAN" is an acronym for Total Acid Number and the
"TAN value" of a hydrocarbon is the amount of potassium hydroxide
in milligrams that is needed to neutralize the acids in one gram of
the hydrocarbon.
[0040] The term "phase transfer catalyst" or "PTC" refers to a
catalyst which facilitates the migration of a reactant in a
heterogeneous system from one phase into another phase where
reaction can take place. Ionic reactants are often soluble in an
aqueous phase but insoluble in an organic phase unless a phase
transfer catalyst is present. Phase transfer catalysts for anion
reactants are often quaternary ammonium salts, but other species
may be effective. Further information about phase transfer
catalysts may be obtained from Mieczyslaw Makozal and Michal
Frdorynski, "Phase Transfer Catalysis", CATALYSIS REVIEWS, Vol. 45,
Nos. 3 and 4, pp. 321-367, 2003 (the disclosures of which is
specifically incorporated herein by this reference).
[0041] The term "alkylating agent" means a reactant that is capable
of reacting with naphthenic acids to convert them to corresponding
esters. Alkyl radicals generally contain only carbon and hyrdrogen,
and may be saturated or unsaturated. Substituted alkyl radicals may
be employed in the present invention provided that any additional
elements or radicals present do not adversely affect the
esterification reaction nor make the resulting ester
oil-insoluble.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0042] The present invention is described in further detail with
reference to the accompanying drawings, in which:
[0043] FIG. 1 is a schematic view of an interfacial region between
an oil phase and a water phase illustrating the kind of reactions
that may take place in the exemplary embodiments of the
invention.
DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
[0044] An exemplary embodiment of the present invention makes use
of a phase transfer catalyst (PTC) that allows compounds to
transfer rapidly from one phase to another as reactions occur, e.g.
during the esterification of naphthenic acids originally present in
the hydrocarbon with an alkylating agent such as an alkyl halide or
an alcohol. The use of such catalysts has the advantage that the
desired reactions may be brought about at relatively low
temperatures (e.g. below 100.degree. C., and often at ambient
temperature such as, for example, 15 to 30.degree. C.), and that
products of the reaction (naphthenic esters) remain in the oil
phase but are non-corrosive. If necessary, the esters may be
removed from the hydrocarbon during further refining, e.g. by
distillation. The catalyst remains in the aqueous phase and can be
reused. A trace amount of the catalyst may transfer to the oil
phase during the method but, if so, it can easily be removed in
subsequent processing (e.g. by washing the oil phase with water)
without causing any corrosion or environmental problems. If
desired, the catalyst may eventually be recovered from the aqueous
phase.
[0045] FIG. 1 of the accompanying drawings illustrates one
preferred embodiment of the present invention. The drawing shows an
oil-and-water system 10 consisting of an oil phase layer 14 and an
aqueous phase layer 16. The aqueous phase layer 16 has an interface
layer 12 in immediate contact with the oil phase layer 14. In
practice, the interface layer 12 is a very thin boundary layer
forming part of the aqueous phase layer. This is the region where
diffusion of species between the two phases may take place at a
rapid rate. The oil phase may be, for example, heavy crude oil, and
the aqueous phase may be a continuous layer or a droplet of an
aqueous liquid brought into contact with the oil phase. Naphthenic
acid (represented in the drawing as RCOOH, although in practice it
will be a mixture of many kinds of acids) is present in the oil
phase layer 14 as shown. The naphthenic acid reacts with an alkali
(in this case, sodium hydroxide, NaOH) present in the aqueous phase
layer 16 to form naphthenic anions (RCOO.sup.-) which, because of
their ionic charge, diffuse rapidly to the aqueous phase at the
interface 12. The aqueous phase also contains a phase transfer
catalyst, in this case an alkyl quaternary ammonium bromide
represented as R'.sub.4NBr (the four groups R' may be the same or
different, and may be the same as or different from R in the
representation of the naphthenic acid. Presently preferred
catalysts are [(C.sub.4H.sub.9).sub.4N]Br and
[(C.sub.4H.sub.9).sub.3--N--C.sub.16H.sub.33]Br). The bromide
dissociates to form a quate cation that reacts with the naphthenic
anion to form RCOO--NR'.sub.4 which is highly soluble in the oil
phase layer and quickly migrates there. In turn, the oil phase has
been provided with an at least partially oil-soluble alkylating
agent, here shown as C.sub.4H.sub.9Br, that reacts with the
RCOO--NR'.sub.4 to form a naphthenic ester RCOOC.sub.4H.sub.9 that
is soluble in the oil phase layer and dissipates into that layer.
The phase transfer catalyst is regenerated and moves to the aqueous
layer at the interface 12 where it is again available for reaction
with the naphthenic anion. The reaction is cyclic as the phase
transfer catalyst is continuously regenerated and reused, and may
take place very quickly. Very little catalyst is lost over time, so
catalyst costs are kept very low. The naphthenic acids are
converted without significant oil loss (because the ester remains
as an oil constituent) and without the production of an emulsion
(even though an alkali is present). Conversions up to 100% may be
achieved in favorable circumstances.
[0046] The oil phase and aqueous phase are preferably agitated
together (e.g. stirred or shaken) to promote a rapid transfer of
chemical species both within the bulk of the phases and across the
interface. Preferably, the aqueous phase is provided in an amount
in the range of 1-20 volume % of the total oil and water
mixture.
[0047] In the illustrated embodiment, bromide is used as the halide
of both the PTC and the alkylating agent. However, the halide (or
other equivalent species such as --OH) does not have to be the same
for both the catalyst and the alkylating agent.
[0048] In order to carry out the indicated process, the phase
transfer catalyst (e.g. tetralkyl ammonium halide) is dissolved in
alkaline hydroxide (e.g. NaOH or KOH) solution and then mixed with
the hydrocarbon to which an alkylating agent (alkyl halide) has
been added. The mixture is preferably stirred for a suitable time
(normally 10 to 240 minutes). After the stirring is terminated, the
aqueous and oil phases separate readily, and the aqueous phase can
be easily removed as no emulsion is formed. The alkali is
preferably used at a concentration up to 1.0M, preferably 0.5M, and
possibly up to 0.1M. The alkaline water content is generally 1 to
20 wt. %. As previously noted, the temperature of the reaction is
generally kept below 100.degree. C., and the reaction is generally
carried out under atmospheric pressure.
[0049] The method is advantageously carried out as soon as the
hydrocarbon is available, e.g. before it is transported through
pipelines to the next processing stages, e.g. desalting, heating,
distillation, etc. In this way, corrosion of the equipment used for
such transportation or subsequent processing can be significantly
reduced. The removal of naphthenic acids before any desalting is
particularly preferred because this greatly reduces the formation
of emulsions in the desalting apparatus and makes the oil-and-water
separation much easier. This not only increases the amount of oil
recovery, but also reduces energy costs. Moreover, since the
naphthenic acids are converted to esters that remain in the treated
oil phase, there is nothing to remove from the aqueous phase and no
further treatment of conversion products is required.
[0050] Further exemplary embodiments of the invention are described
in the Examples below. These Examples are provided for the purpose
of illustration only.
EXAMPLES
[0051] In the following Examples, all chemicals were purchased from
Sigma Aldrich.RTM. and used without alteration. The properties of
the HVGO used are listed in Table 1. All experiments were conducted
following the procedure below: [0052] 1. Bromobutane and heavy
vacuum gas oil (HVGO) were added in a flask. The mixture was heated
to 80.degree. C. in an oil bath under stirring. [0053] 2. PTC
(tetrabutylammonium bromide) was completely dissolved in NaOH
aqueous solution, and added to the flask prepared in 1. [0054] 3.
The above mixture was stirred at 80.degree. C. for 4 hours. [0055]
4. After reaction, the flask was quenched with cold water and the
contents transferred into a centrifuge bottle. [0056] 5. The water
was separated from oil using an IECCR-6000.RTM. centrifuge (3800
rpm for 30 min).
[0057] The oil phase was analyzed for TAN, sulfur, nitrogen, and
boiling range. The nitrogen and sulfur were analyzed according to
ASTM D4629 (syringe/inlet oxidative combustion and
chemiluminescence detection), and ASTM D4294 (energy-dispersive
X-ray fluorescence spectrometry), respectively. The boiling range
was measured with simulated distillation (SimDis) by gas
chromatography. The water was tested for pH as well as carbon and
nitrogen contents. The carbon and nitrogen contents in water phase
were analyzed by ICP. The results are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Properties of HVGO TAN 4.12 Sulfur, wt %
3.28 N, wt % 1.22 Boiling range .degree. C. 0.5 262 10 325 30 369
50 404 70 438 80 459 90 488 95 510 99 551 99.5 566
[0058] Various tests were carried out at different NaOH
concentrations as illustrated in Table 2 below.
TABLE-US-00002 TABLE 2 NaOH concentration effect Sample No. ENR-15
ENR-18 ENR-20 ENR-21 Reactant composition HVGO, g 80 80 80 80 NaOH
solution Weight, g 20 20 20 20 Concentration of NaOH, M 0.001 0.15
0.25 0.50 PTC, g 3.55 3.55 3.55 3.55 Bromobutane, g 7.54 7.54 7.54
7.54 Reaction conditions Temperature, .degree. C. 80 80 80 80 Time,
hours 4 4 4 4 Treated oil TAN 3.58 2.61 0.35 0 Naphthenic acid
removal, % 13.1 36.6 91.5 100 Ease of oil-water separation Easy
Easy Easy Easy Water phase appearence Clear Clear Clear Clear
[0059] The TAN values after various reaction time were measured and
the results are shown in Table 3 below.
TABLE-US-00003 TABLE 3 TAN after various reaction time, mgKOH/g oil
NaOH concentration, M Reaction time, min 0.15 0.25 30 1.598 0.330
60 1.638 0.355 120 1.668 0.350 Temperature: 80.degree. C. NaOH
solution: 20 g Bromobutane: 7.54 g HVGO: 80 g PTC: 3.55 g
[0060] The effects of different concentrations of the PTC were
determined and the results are shown in Table 4 below.
TABLE-US-00004 TABLE 4 Effect of PTC concentration Sample No.
ENR-34-1.0 ENR-34-0.5 ENR-34-0.2 PTC/acid molar ratio 1.0 0.5 0.2
Reactant composition HVGO, g 80 80 80 0.25M NaOH solution, g 20 20
20 PTC, g 1.89 0.95 0.38 Bromobutane, g 7.54 7.54 7.54 Reaction
conditions Temperature, .degree. C. 80 80 80 Time, hours 4 4 4 TAN
of treated oil, mgKOH/g 0.501 0.618 0.481 Ease of oil-water
separation Easy Easy Easy Water phase appearance Clear Clear
Clear
[0061] Different PTCs were used in the method and the results are
shown in Table 5 below. It can be seen that
tributylhexdecaylammonium bromide gave the better result, although
both results were acceptable.
TABLE-US-00005 TABLE 5 Effect of PTC type Tetrabutyl- ammonium
Tributylhexdecaylammonium PTC catalyts bromide bromide Reactant
composition HVGO, g 80 80 0.25M NaOH solution, g 20 20 PTC, g 3.55
3.55 Bromobutane, g 7.54 7.54 Reaction conditions Temperature,
.degree. C. 80 80 Time, hours 4 4 TAN of treated oil, 0.35 0.05
mgKOH/g Ease of oil-water separation Easy Easy Water phase
appearance Clear Clear
* * * * *