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Patented Jan. 7, l947
mm STATES * PATENT omce
REFINING HYDRO CARBON DISTILLATES
Chester E. Adams, Highland, and Theodore B.
Tom, Hammond, Ind., assignors to Standard Oil‘
Company, Chicago, 111., a corporation
Indiana
of
‘
No Drawing. Application November 20, 1944,
Serial No. 564,410
9 Claims. (Cl. 19.6-—30)
1
This invention relates’ to the extraction of
weakly acidic substances from hydrocarbon solu
tions and more particularly it relates to the ex
traction of mercaptans from hydrocarbon oils
such as petroleum distillates, naptha, gasoline,
kerosene, etc. In the manufacture of gasoline
and other petroleum distillates known in re?nery
practice as “light oils,” it has long been a problem
to ' remove therefrom ill-smelling sulfur com
2
contains from 2 to 4 carbon atoms. In addition
to ethoxy acetic acid mentioned above, we may
employ particularly propoxy acetic acid and bu
toxy acetic acid. We may also employ the methyl
and ethyl ethers of malic, lactic and tartaric acids.
Other suitable ethers are the methyl and ethyl
ethers of hydroxy valeric acid and anisic acid.
In Carrying out our process, the hydrocarbon
distillate containing mercaptans or other weakly
pounds which are primarily mercaptans. Certain 10 acidic material is contacted preferably in a coun
tercurrent extraction tower with a strong alka
processes such as the doctor treating process have
line solution of the carboXy ether solutizer. For
been employed to convert mercaptans into other
this purpose, sodium or potassium hydroxide may
sulfur compounds such as disul?des'which are
be used, preferably the latter, in a concentration
less objectionable from the standpoint of odor.
However, this conversion does not decrease the 15 of about 2 to 6 normal free caustic above that
sulfur content of the gasoline and it has been
combined with the solutizer agent. The concen
iound that the disul?des themselves are quite obtration of solutizer employed will usually be
jectionable from the standpoint of gasoline detowithin the range of about 5 to 40 percent on the
nation characteristics.
basis of free carboxy acid in the alkali solution.
’ Numerous processes have been devised for ex- 20 Usually the carboxy ether concentration falls
- tracting the mercaptans completely, thus prowithin the range of 1.5 to 4 molar. The extrac
ducing a gasoline of higher knock rating and
tion step is preferably carried out at ordinary
higher susceptibility to knock rating improvetemperature, for example 40 to 100° F., and the
ment resulting from the addition of tetraethyl
solutizer solution containing dissolved mercap
lead. In general, these processes have employed ~35 tans or other weakly acidic substance is with
strong alkali solutions in conjunction with cerdrawn from the extractor and separately regen
tain mercaptan solubilizing agents known as
erated after which it is recycled to the extrac
solutizers.
tion step. The regeneration operation consists in
One of the objects of this invention is to pro‘removing from the caustic solutizer solution the
vide an improved solutizer for the extraction of 3c dissolved mercaptans or other, weakly acidic sub
weakly acidic substances from petroleum distilstances, and is preferably carried out by blowing
lates. Another object of the invention is to prowith air, for example at a slightly elevated tem
vide a process of removing mercaptans more eiperature, e. g., 120 to 130° F. It is desirable to
' fectively from gasoline and other petroleum disavoid subjecting the solutizer solution to a tem
tillates by means of a solution which can be read- 35 peratul‘e sufficiently high 1'10 accelerate materially
ily regenerated and recycled in the extraction
hydrolysis of the carboxy ether employed;
operation. A further object of the invention is
In the regeneration operation, part of the mer
to provide a solutizer which is inexpensive and
captans may be removed by dissociation and
at the same time highly effective and which may
evaporation and part by the oxidizing action of
be employed in combination with other solutizers. =10 the air converting them to disul?des which are
According to our invention we employ as a
solutizer in our process the alkali metal salts of
' the carboxy ethers having from 3 to 8 carbon
atoms which we have discovered to be highly efiective for the extraction of mercaptans occur- 45
no longer soluble in the solutizer solution. These
disul?des may be removed as an upper oily layer
and, if desired, a hydrocarbon solvent may 'be
employed to assist in their removal from the re
generated solutizer solution. The solutizer solu
ring in light petroleum distillates, for example,
straight-run or cracked gasoline, heavy naptha,
tion is then recycled to the continuous extraction
step of the process for the accumulation of more
etc. We have found that carboxy ethers having
from 4 to 6 carbon atoms are especially effective.
mercaptans.
‘
The regeneration reaction may be accelerated
Typical examples of our solutizers are carboxy 50 by employing catalysts which have the ability to
speed the oxidation of the mercaptans. For this
purpose certain alkali-soluble metal oxides may .
wise known as ethoxy acetic acid, carboxy diethyl
be employed, such as the oxides of lead, tin, etc.
ether, or, w dicarboxy glycol dimethylether, etc.
but we prefer to employ compounds of the char
The carboxy ethers of this invention include pri
dimethyl ether, carboxy methylethylether, other
. marily the alkoxy acids of which the acid radical .
acter of phenols and polyphenols in accordance
2,413,938
3
4
with the teaching of the U. S. patent of Pevere,
2,015,038 (September 17, 1935). According to this
be seen from these data that excellent extraction
of mercaptans was obtained in test 2 by the use
of 3 normal potassium ethoxy acetate in 6 nor
mal KO-H solution and that the combination be
tiveen ethoxy acetic acid and cresylic acid gave
even more effective mercaptan extraction in tests
method there is added to the solutizer solution a
small amount of a phenol or polyphenol such as
hydroquinone, catechol, pyrogallol, gallic acid,
tannic acid, etc;, using a concentration of about
0.1 to 1 percent, thereby greatly increasing the
3 and 4. Isopropoxyacetate in test 8 was even
rate of regeneration in the presence of air or oxy
more effective than the ethoxy compound in test
gen. One very signi?cant bene?t resulting from
2. In a countercurrent operation it is easily pos
the use of these phenolic catalysts is that they 10 sible to reduce the mercaptan concentration to
enable regeneration to be carried out at a lower
a point at which the treated gasoline will react
temperature, for example room temperature,
sweet to the doctor test. However, it may be
thereby reducing hydrolysis of the carboxy ether
more economical in practice to remove the major
portion of the mercaptans from the stock by solu
generated at substantially higher temperatures 15 tizer extraction and then treat the stock further
In the treatment of certain petroleum stocks,
in a separate sweetening operation with doctor,
particularly cracked gasoline containing small
hypochlorite, etc., to produce a stock which will
amounts of phenolic compounds, especially cre
pass the doctor test where that is desired.
sols, it is desirable to precede the extraction with
The copper number referred to above is deter
an alkali washing step to remove phenols, cresols, 20 mined by titrating a 100 ml. sample of naptha
etc., thus preventing an excessive amount of such
with standard ammoniacal copper solution, 1 ml.
phenolic substances accumulating in the solutizer
of which is equivalent to 1 mg. mercaptan sul
solution. In the treatment of such phenol-con
fur per 100 ml. (1 copper number). The end
taining stocks, however, there is often a distinct
point is observed when the blue color fails to be
advantage to permitting a controlled amount of 25 discharged after shaking.
such phenols, cresols, etc., accumulating in the
Having thus described our invention, what we
solutizer solution, and we have found that the
claim is:
combination of cresols and our carboxy ethers
1. The process of extracting weakly acidic SUD
provides a very effective reagent for extracting
stances from hydrocarbon distillates which com
mercaptans. We prefer to control the amount 30 prises contacting said distillates with an aqueous
solutizer which would occur, were the solution re- 1
of cresols in the range of about 1 to 3 normal
concentration. Inasmuch as the distillate ex
tracted by such a solution has been found to carry
away in solution a small amount of cresols in
the concentration which is in equilibrium with 3
that in the solutizer solution, and inasmuch as
cresols exert a valuable antioxidant effect on
the treated gasoline, particularly in the case of
solution of an alkali metal hydroxide and a solu
tizer comprising an alkali metal salt of a carboxy
ether containing from 3 to 8 carbon atoms.
2. The process of removing mercaptans from
a petroleum distillate which comprises contact
ing said distillate with an aqueous solution of an
alkali metal hydroxide and a solutizer compris
ing an alkali metal salt of a carboxy ether con
cracked stocks, it is clearly desirable to employ
taining from 3 to 8 carbon atoms.
a solutizer solution containing cresols. Other 40
3. The process of claim 2 wherein said alkali
solutizers besides cresols may be employed with
metal is potassium.
our carboxy ethers and a suitable proportion is
4. The process of extracting weakly acidic sub
a molar ratio of 0.2 to 0.8. '
stances from hydrocarbon distillates which com
The following table gives the results obtained
prises contacting said distillates with an aqueous
in the extraction of a sour naphtha containing ' solution of an alkali metal hydroxide and a solu
primarily butyl mercaptan as an example of a
tizer comprising a-n'alkali metal salt of an alkoxy
weakly acidic substance. Removal of the butyl
acid containing from 3 to 8 carbon atoms.
mercaptan is indicated by the copper number
5. The process of removing mercaptans from a
of the naptha. Extraction was carried out in
hydrocarbon distillate which comprises extract
the ratio of one volume of solutizer solution to 50 ing said distillate with an aqueous solution of an
?ve volumes of naptha in a single batch extrac
alkali metal hydroxide and a solutizer compris
tion step. The solutizer was ethoxy acetic acid,
ing a mixture of alkali metal cresylate and an
or isopropoxyacetic acid, alone or employed with
alkali metal salt of a carboxy ether containing
cresol.
from 3 to 8 carbon atoms.
Copper number of B utyl mer
naptha
captan dis
Composition of solutizer solution
Before
After
extraction extraction
6N KOH, 2N EtOCH2COOK ____________ ._
6N KOH, 3N EtOCHzCOOKl _________ _
5N NaOH, 3N EtOCHzCOONa...
_ 4N KOH, 3N i-ProOCHzCOOK
5N KOH, 2N i-ProOOHzCOOK.-
4N KOH, 2N i-ProOCHzCOOK, N cresylate__._
3N NaOH, 2N i-ProOCHzCOONa, 1.5N cresylate
_
-
tribution
coejl?énent'
‘1
100
100
7
4
67
120
100
100
2
2. 5
245
195
100
5
95
I00
100
6
6
78
78
100
100
100
100
3
3. 5
2
6
162
138
245
78
1 The once-used solutizer was used again: copper No. 100 -—> 7.
The efficiency of extraction is indicated by the
6. The process of removing mercaptans from
coe?icient, Kq which is the concentration of mara sour hydrocarbon distillate which comprises
captans in the caustic solution divided by the
extracting said distillate countercurrently with
concentration remaining in the naptha. It will 75 an aqueous solution of an alkali metal hydroxide
' 2,413,938
5
containing su?icient alkali metal salt of ethoxy
acetic acid to increase substantially the solubility
of said mercaptans in said solution.
7. The process of claim 5 wherein the concen
tration of free alkali metal hydroxide in the said
solution is about 2 to 6 normal and the concen
tration of the said ethoxy acetic acid is about 1 to
containing su?lcient alkali metal salt of propoxy
acetic acid to increase substantially the solubility
of said mercaptans in said solution.
9. The process of removing mercaptans from
a sour hydrocarbon distillate which comprises ex
tracting said distillate countercurrently with an
aqueous solution of an alkali metal hydroxide
containing su?icient alkali metal salt of butoxy
4 normal.
acetic acid to increase substantially the solubility
8. The process of removing mercaptans from a
sour hydrocarbon distillate which comprises ex~ 10 of said mercaptans in said solution.
CHESTER E. ADAMS.
tracting said distillate countercurrently with an
THEODORE B. TOM.
aqueous solution of an alkali metal hydroxide
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