Note: Descriptions are shown in the official language in which they were submitted.
~3~ 7
BACKGROUND OF THE INVENTION
The present invention relates generally to the
sulfonation of alkylated aromatic hydrocarbons, such as
alkyl benzene, and more particularly to the sulfonation of
such hydrocarbons using sulfur trioxide as a sulfonating
agent.
In a typical sulfonating operation in which alkyl
benzene is the alkylated aromatic hydrocarbon undergoing
sulfonation, the alkyl benzene is reacted with a sulfonating
agent, such as sulfur trioxide gas in an air carrier, to
form a sulfonic acid which is then neutralized with an
alkali metal hydroxide, such as sodium hydroxide, to form a
sulfonate. During the sulfonation operation, side reactions
may occur which form sulfuric acid (H2SO4), and during the
subsequent neutralization step, the sulfuric acid is converted
to an alkali metal sulfate (e.g., Na2SO4). The neutralized
product, typically consisting essentially of sodium sulfonate,
is used primarily for detergent. The sodium sulfate in the
end product is undesirable for detergent purposes.
It is also desirable to maintain the color of the
end product as good as possible. On a Klett color scale (5%
solution, 40 mm path), the lower the Klett number, the
better the color; and a Klett number of 50 or below indicates
increasingly excellent color.
In the sulfonation of unalkylated aromatic hydrocarbons,
such as toluene, benzene, xylene and the like, there are
formed undesirable side reaction products called sulfones.
The sulfone content resulting from the sulfonation of
unalkylated aromatic hydrocarbons may be reduced by adding a
low molecular weight carboxylic acid such as acetic acid,
" ~
~3~
propionic acid, butyric acid, valeric acid, cuproic or
caprylic acid (see Gilbert et al. U.S. Patent No. 2,704,295).
Sulfone formation is generally not a problem in the sulfonation
of alkylated aromatic hydrocarbons, such as alkyl benzene.
However, Norwood et al. U.S. Patent 2,831,020 discloses the
-
sulfonation of aromatic hydrocarbons, including alkyl
benzene among others, with SO3 gas dissolved in liquid SO2
and the addition thereto of 0.25-1% of an organic carboxylic
acid (e.g., acetic, malonic, azelaic or benzoic acids) to
reduce the sulfone content. Norwood et al. also states that
the formation of sulfones reduces the efficiency of the
process by wasting reagent.
In Benson et al. U.S. Patent No. 3,681,443 there
is disclosed a process for the sulfonation of alkyl benzene
with SO3 gas, or SO3 dissolved in liquid SO2, to form
sulfonic acid to which is added 0.25-2.5% of an alpha, beta-
unsaturated carboxylic acid (e.g., fumaric, maleic, citraconic
or mesaconic acids), with the carboxylic acid being added to
the sulfonic acid after the latter has been formed. According
to Benson et al., the objectives of adding these carboxylic
acids to the sulfonic acid are to retard color degradation
of the sulfonic acid and to retard acid or pH drift of the
sulfonic acid.
As part of the disclosure, Benson et al. refers to
Norwood et al. '020, discussed above, and acknowledges that
Norwood et al. teaches the use of certain carboxylic acids
for inhibiting the formation of sulfones in the sulfonation
of alkylated aromatic hydrocarbons using sulfur trioxide
(SO3) dissolved in li~uid sulfur dioxide (SO2). However,
Benson et al. goes on to say that the carboxylic acids,
--2--
2~
disclosed in Norwood et al. as useful in preventing the
formation of sulfones, are unsatisfactory and ineffective to
achieve the objectives of ~enson et al., namely re-tarding
color degradation and acid drift in the sulfonic acid after
the latter has been formed. Sulfones are relatively colorless
and do not affect the color of the sulfonic acid to any
substantial degree.
SUM~ARY OF_THE INVENTION
In a sulfonation process in accordance with the
present invention, an alkylated aromatic hydrocarbon is
sulfonated with SO3 gas, the color of the sulfonic acid is
improved, and the sulfuric acid content of the product
resulting from the sulfonation reaction is reduced (thereby
reducing the sodium sulfate content in the final sodium
sulfonate product). These two improvements are accomplished
by adding to the alkylated aromatic hydrocarbon a low
molecular weight, anhydrous carboxylic acid such as acetic
acid, benzoic acid or propionic acid. These are among the
very acids which Benson et al. stated would not prevent
color degradation when added to the sulfonic acid after the
latter was formed.
In accordance with the present invention, these
carboxylic acids are added to the alkylated aromatic hydrocarbon
(e.g., alkyl ben~ene~ prior to the reaction thereof with the
sulfur trioxide gas. The sulfur trioxide gas is the sole
sulfonating agent used in the reaction.
; In addition to improving the color and reducing
the amount of sulfuric acid formed, the addition of acetic
acid, for example, to the alkylated hydrocarbon increases
the active content (e.g., above 96.5%) and reduces the free
--3--
~L~3~Z~7
oil content (e.g., below 1.5~) of the sulfonation product.
The acetic acid addition prevents color degradation
not only during the initial sulfonation reaction but also
during the digestion period which normally follows the
initial reaction period. This permits operating at a higher
digestion temperature without degrading the color (e.g.,
125-130F versus 115F maximum without acetic acid).
Operating at a higher diges-tion temperature in turn drives
the reaction further toward completion, thus depleting the
free oil content.
Typical sulfonation processing and operating conditions
and procedures and a typical apparatus for sulfonating
alkylated aromatic hydrocarbons useful in connection with
an embodiment of the present invention are described in
the copending application of the present applicant,
No. 277,481 filed May 3, 1977.
In brief, in the sulfonation process of said
application no. 277,481, the alkylated aromatic hydrocarbon
is atomized and, in its atomized condition, reacted with
the SO3 in a venturi-type reactor or venturi section.
The resulting reaction mixture is quenched~ in a quenching
section immediately downstream of the venturij with a
cooling liquid comprising cooled, recycled sulfonic acid,
and the particles of liquid in the reaction mixture are
agglomerated into the cooling liquid by flowing the
particles between parallel streams of the cooling liquid.
At least part of the liquid, into which the liquid particles
have been agglomerated, is cooled and recycled as the cooling
,.~,
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liquid, and the other part is withdrawn from the recycle
loop and digested and neutralized.
Other features and advantages are inherent in the
structure claimed and disclosed or will become apparent to
those skilled in the art from the following detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
Flg. 1 is a fragmentary sectional view of an
apparatus for sulfonating an alkylated aromatic hydrocarbon
in accordance with an embodiment of the present invention;
and
Fig. 2 is a flow diagram illustrating an embodiment
of a method in accordance with the present invention.
DETAILED DESCRIPTION
The organic reactants to which the present invention
is applicable are alkylated aromatic hydrocarbons with a
side chain having 11 to 25 carbon atoms, 11 to 15 carbon
atoms in the side chain being preferred. Examples of such
hydrocarbons are alkyl benzene or alkyl toluene.
The sulfonating agent in accordance with the
present invention is sulfur trioxide gas (SO3) in an air
carrier, as more fully described in the abo~e-noted earlier
n~ ~ ~7 ?, ~/~
application er~
The neutralizing agent for neutralizing the
sulfonic acid formed from the reaction of the SO3 gas with
the alkylated aromatic hydrocarbons is an alkali metal
hydroxide, such as sodium hydroxide, potassium hydroxide or -
ammonium hydroxide.
Examples of low molecular weight, anhydrous
carboxylic acids which are useful in accordance with the
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present invention for improving the color and reducing the
sulfuric acid content of the sulfonic acid are acetic acid
(the preferred material in most cases), benzoic acid,
propionic acid, malonic acid, azelaic acid, butyric acid,
valeric acid, cuproic acid and caprylic acid. Acetic acid
is effective on both linear and branched chain alkyl benzene.
Propionic acid is slightly more effective on linear then on
branched chain.
When acetic acid is neutralized, it forms, e.g.,
sodium acetate which is an acceptable ingredient sometimes
intentionally added to cosmetic and detergent grade sulfonates
as a buffering agent to prevent pH drift. Thus, the addition
of acetic acid further upstream, to the organic reactant,
does not introduce to the neutralized sulfonate end-product
an unwanted ingredient.
The carboxylic acid should be added in an amount
in the range 0.03-0.3% of the weight of the alkylated
aromatic hydrocarbon (alkyl benzene) to which the carboxylic
acid is added. Above 0.3% there is no significant improve-
ment compared to 0.3%, although there is also no harm tousing amounts above 0.3%. A preferred range is 0.1-0~2%
when used with alkyl benzene.
Referring initially to Fig. l, indicated generally
at 7 is a reactor including a venturi indicated generally at
8 and comprisin~, in downstream sequence, an upstream end 9,
an approach zone 11 having side walls converging in a
downstream direction, a throat 12, a recovery zone 13 having
side walls diverging in a downstream direction and a down-
stream end 10. A first conduit 16 communicates with venturi
approach zone 11 and is axially aligned therewith. Conduit
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16 includes an inlet 17 extending to one side of conduit 16,
and ports 18, 19 for inserting temperature and pressure
measuring devices.
A second conduit indicated generally at 20 includes
an upstream portion 21 communicating with downstream end 10
of venturi 8 and axially aligned with the venturi immediately
downstream thereof.
Located concentrically within first conduit 16 is
a third conduit 22 terminating at fluid injection means 23
located within venturi approach zone 11. Third conduit 22
includes an inlet 24 at the upstream end thereof.
Located concentrically within the upstream portion
21 of second conduit 20 is a fourth conduit 26 terminating
at liquid outlet means 27 adjacent downstream end 10 of
venturi 8. Outlet means 27 may extend into venturi recovery
zone 13. Located at the opposite end of fourth conduit 26
is a liquid inlet 28.
Referring now to both Figs. 1 and 2, second
conduit 20 has an outlet 29 communicating with one end of a
line 30 having another end leading into a liquid cyclone
separator 31. Communicating with the top of cyclone sepa- -
rator 31 is a vent line 32, and communicating with the
bottom of cyclone separator 31 is an outlet line 33 com-
municating with a pump 3~ from which extends a line 35
leading to a heat exchanger 36 from which extends a line 37
leading to inlet 28 in faurth conduit 26.
~lso extending from pump outlet line 35 is another
line 38 from which extends a branch line 39 leading back to
cyclone separator 31.
First conduit 16, through which the gaseous
~33L%~
sulfonating agent is introduced into the venturi, preferably
has a straight length of approximately 10 pipe diameters
upstream of venturi 8. This is desirable to smooth out the
flow and distribution of the gas, following movement of the
gas around a curve or elbow or corner such as at inlet 17.
Injection means 23, through which liquid organic
reactant is injected into the gas stream at venturi approach
zone 11, usually comprises a plurality of small holes around
the periphery of a tube perfectly centered within venturi
approach zone 11 (although only one hole is shown in Fig.
1) .
In a -typical operation utilizing the reactor 7,
gaseous sulfonating agent (sulfur trioxide gas plus air) is
introduced through inlet 17 into first conduit 16. Si-
multaneously, the alkylated aromatic hydrocarbon or liquid
reactant is introduced through inlet 24 into third conduit
22. The anhydrous, low molecular weight carboxylic acid is
added to the liquid hydrocarbon upstream of inlet 24.
The gaseous sulfonating agent flows downstream
through conduit 16 into venturi approach zone 11, and the
liquid organic reactant is injected into the stream of
gaseous sulfonating agent in venturi approach zone 11
through injecting means 23.
Upon injection of the organic reactant into the
gaseous sulfonating agent at approach zone 11, the organic
reactant is atomized by the high speed gas into a fine mist
which absorbs and reacts with the sulfur trioxide in the
gaseous sulfonating agent. The reaction mixture thus formed
continues to move through and out of the venturi 8 in a
downstream direction.
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Atomization may also be accomplished by injecting
the liquid organic reactant as a film at the periphery of
the venturi (e.y., through a peripheral slit in the approach
zone) and providing a gas velocity sufficiently high (e.g.,
350 feet per second or higher) to assure atomization.
After leaving venturi 8, the reaction mixture is
flowed along a confined pathr downstream of the venturi,
defined by conduit 20. The reaction mixture is quenched, to
cool the mixture, no later than immediately after the
mixture leaves venturi 8. The reaction mixture, at the
start of the quenching step, is in the form of fine par-
ticles of liquid (including particles of sulfonic acid) in a
gaseous carrying medium. In other words, the reaction
mixture liquid is present as a discontinuous phase. Quenching
is accomplished by contacting the reaction mixture with a
moving volume or mass of cooled, recycled liquid reaction
product comprising sulfonic acid and introduced into the
reactor through fourth conduit 26 via outlet means 27 at the
terminal end of conduit 26. In other words, the quenching
liquid is provided as a continuous phase at outlet means 27.
A stream o~ cooled liquid reaction product contacts
the reaction mixture at downstream end 10 of venturi 8 or
slightly upstream thereof. The quenching liquid then flows
through conduit 20 along a path coinciding with the flow
path of the reaction mixture coming from the venturi, with
the quenching liquid assuming the form of a film along the
outside walls of fourth conduit 26 and a film along the
inside walls o~ second conduit 20. The quenching liquid for
the latter film may be introduced through a peripheral slit
40 in venturi recovery zone 13 supplied by a branch line 41
~3~2~
communicating with recycle line 37.
By flowing the quenching liquid as a film along a
path parallel to and adjacent that of the reaction mixture,
there is provided repeated contact between the fine par-
ticles of reaction product and the film of cooled liquid
reaction product thereby causing the fine particles to
agglomerate. A factor in the continuous contacting of the
fine particles of liquid reaction product with the film of
cooled liquid reaction product is the presence, in conduit
20, of gas eddies which repeatedly impinge the fine particles
a~ainst the recycled quenching liquid flowing down the walls
of conduits 20 and 26.
The mixture of liquid and spent gas leaves second
conduit 20 through outlet 29 and flows through line 30 into
cyclone separator 31 where the gas is separated from the
liquid, the gas being withdrawn through vent line 32 and the
liquid (consisting essentially of reaction product, i.e.,
sulfonic acid) being removed through line 33.
The effluent gas removed through vent line 32 has
a lower sulfur dioxide content ~SO2 gas) when low molecular
weight carboxylic acid is added to the liquid hydrocarbon in
accordance with the present invention (e.g., 100-150 parts
per million (ppm) versus 200-300 ppm without such an addition).
Reduced SO2 content in the effluent gas indicates a reduction
in certain reactions which accompany poorer color. The
addition of the low molecular weight carboxylic acid retards
these reactions which form color bodies.
Part of the liquid removed from the bottom of
cyclone separator 31 through line 33 is pumped by pump 34
through line 35 to heat exchanger 36 from which cooled
-- 10 --
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liquid reaction product is recycled through line 37 back
to fourth conduit 26, as quenching liquid. Another part
of the liquid removed Erom the bottom of cyclone separator
31 is pumped through a line 38 to additional processing
stages including digestion and neutralization. A portion
of the liquid reaction product moving through line 38 is
recycled through branch line 39 back to cyclone separator
31 to wash the walls of cyclone separator 31 and prevent
the buildup thereon of over-reacted material.
Only part of the reaction usually occurs in venturi
8. Additional reaction takes place in conduit 20, the
recycle loop (30, 31, 33-37) illustrated in Fig. 2 and
downstream thereof.
A more detailed discussion of the processing and
operating conditions and procedures and apparatus described
above is contained in Canadian application no. 277,481
referred to above.
Following is a summary of examples of typical
operating conditions for the venturi and quenching sections.
Ven-tur-i Sect-ion
Liquid organic reactant injection through multiple
holes.
Actual gas velocity at liquid injection point --
100 feet/second.
Actual gas velocity at venturi throat -- 400-550
feet/second.
Temperature at venturi throat -- 120-160F.
Pressure drop through venturi - 4-7 psig.
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Quenching Section
Actual gas velocity at upstream end -- 110 feet/second
minimum.
~ctual gas velocity at downstream end -- 130 feet/second
mlnimum.
Liquid to gas ratio, by weight -- 30/1.
by volume -- 1/25.
Recycle ratio [(a) recycled liquid to (b) organic reactant
feed plus sulfur trioxide feed] -- 35/1.
Estimated film thickness -- 0.12-0.2".
Pressure drop -- 3-4 psig.
Calculated Reynolds No. of liquid film -- 100-200.
Follo~ing is an example of the processing conditions
in a sulfonation process in accordance with the present
in~ention (except for the addition of the carboxylic
acid, examples of which are described subsequently).
Organic Reactant - Linear dodecyl benzene
Organic Reactant Flow Rate - 600#~hr.
SO3 Flow Rate - 216#/hr.
SO3 Concentration - 6.5 vol. %
Air Flow Rate - 250 SCFM
Venturi Diameter at Throat - 1"
Reaction Path Length - 8"
Gas Pressure at Upstream End of Venturi - 10-13 PSIG
Pressure at Venturi Throat - 6 PSIG
Approximate Gas Velocity at Venturi Throat -
550 Ft./Sec.
Approximate Gas Velocity at Organic Reactant
Injection Point - 160 Ft./Sec.
Ratio of Recycle Quench to Reactants - 40 to 1
Quenching Liquid Temperature - 115F.
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Gas Velocity in Agglomeration Section -
130 Ft./Sec.
Digestion Time Following Recycle Loop - 30 minutes
As noted above, in accordance with the present
invention, an anhydrous, low molecular weight carboxylic
acid is added to the alkylated aromatic hydrocarbon prior to
the reaction thereof with the sulfur trioxide gas, and
examples comparing (a) the present invention, utilizing said
carboxylic acid addition, and (b) a process otherwise the
same except for the absence of said carboxylic acid addition
are listed in the following table.
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7.
TABLE I
Example No. 1 2 3
Mol ratio of SO3 1.06 1.04 1.04
to linear alkyl
benzene
Acetic acid -- 0.1% 0.25%
addition
(alkyl benzene
weight basis)
Free oil, 1.8% 1.0% 0.7%
petroleum ether
; extract procedure
(active ingredient
basis)
_
; Na2S 4 2.5% 2.0% 1~5%
Klett color 35-40 30 30
(5% solution,
; 40 mm. path)
From the table it will be noted that there is an
improvement in color, up to 25%, when comparing a process
with a carboxylic acid addition in accordance with the
present invention (Examples 2-3) with a process in which
there was no such addition. In addition, in a process in
accordance with the present invention, there is a reduction
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in sodium sulfate content, in the sodium sulfonate product,
of up to 40%, this being a reflection of a reduction of the
sulfuric acid produced as a side reaction product in the
sulfonation reaction of the alkyl benzene. Moreover, the
sodium sulfate content is reduced by 20% and 40% respectively
in Examples 2 and 3 while the mol ratio of SO3 to alkyl
benzene was reduced less than 2%. The free oil contents in
Examples 2 and 3 are reduced to 55% and 38% respectively of
that in Example 1.
Additional Examples 4-6 are reflected in the
following table. Standard operating conditions were employed
using a sulfonating process of the type described above and
illustrated in Fig. 2. The organic reactant employed was an
alkyl benzene having a molecular weight of 238. Examples 5
and 6 employed acetic acid while Example 4 did not. Example
5 reflects a liquid detergent formulation while Example 6
reflects a powder deter~ent formulation.
TABLE II
Example_No. 4 5 6_
Mol ratio of SO3 l.G5-1.06 1.02-1.03 1.04-1.06
to alkyl benzene
SO3 concentrate 7-8% 7-8% 7-8%
(volume %)
.
Temperature of 110-115F 100-110F 115-130F
recycle liquid
,, .
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Acetic acid -- 0.1% 0.1-0.4%
addition (alkyl
benzene weight
basis
Active ingredient 95.5-96.0% 97.0-97.5% 96.8-97.2%
wt. % (Hyamine
titration
procedure)
Free oil, 1.8-2.0% 1.0-1.3% 0.5-0.7%
petroleum ether
extract procedure
(active
ingredient basis)
Sulfuric acid 2.0-2.2% 1.3-1.5% 1~5-2.2%
(before
neutraliæation)
wt. %
Water, wt. % 0.1-0.2% 0.1-0.2% 0.1-0.2%
_
Klett color (5% 40-50 20-30 35-50
solution, 40 mm
path)
-
30Comparing Examples 4 and 5, it is seen that adding
aeetie aeid (Example 5) inereases the active ingredient
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~3~
content even wlth a reduced mol ratio of SO3, decreases the
free oil content, decreases the sulfuric acid content and
improves the color. Comparing Examples 4 and 6, it is seen
that, at recycle liquid (digestion) temperatures above
115F, with an acetic acid addition there is no color degradation
while improvements in active ingredient and free oil content
are substantial.
Thus, an acetic acid addition in accordance with
the present invention permits greater flexibility in the
operating conditions of the sulfonating process. It allows
a higher digestion temperature without adversely affecting
color, or it allows a lower mol ratio of SO3 to hydrocarbon
reactant without decreasing the amount of active ingredient
formed or increasing the amount of free oil; and it forms a
product of improved color, with less sulfuric acid, less
free oil and more active ingredient with less SO3 required
to perform the reaction.
The foregoing examples of the process have been
described in connection with a jet reactor (Fig. 1) for
performing the sulfonation operation, but the present
invention is not limited to jet reactors and may also be
useful with other types of reactors (e.g., film reactors) as
are conventional in the sul~onation of organic reactants
with SO3.
The foregoing detailed description has been given
for clearness of understand only, and no unnecessary limitations
should be understood therefrom, as modifications will be
obvious to those skilled in the art.
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