Apparatus for continuous sulfonation

A cylindrical apparatus for continuous sulfonation of an organic liquid is provided with an annular feeding device for permitting the organic liquid to flow in the form of a film down a reaction wall. The annular feeding device is provided with a number of slots in a horizontal and equidistant manner in a row.

This invention relates to an apparatus for continuous sulfonation of an 
organic liquid. More particularly, this invention relates to an improved 
apparatus for continuously sulfonating the organic liquid by permitting it 
to flow in the form of a film down a reaction wall to undergo a gas-liquid 
contact reaction with sulfur trioxide. The term "sulfonation" hereinafter 
used in the specification and in the claims is defined to mean both the 
sulfonation and the sulfation. 
A surface-active agent such as alkylbenzene sulfonate, alkyl sulfate, or 
.alpha.-olefin sulfonate is produced by utilizing the sulfonation 
reaction. In the production of, for example, alkyl sulfate, the 
sulfonation is performed wherein a sulfur trioxide (having a SO.sub.3 
concentration of 2 to 8%) diluted by air or an inert gas such as nitrogen 
gas is allowed to contact a liquid raw material. Such sulfonation based on 
the use of sulfur trioxide is not limited to the above example but is 
widely utilized for the production of surface-active agent or dyes. 
The above-mentioned sulfonation, however, is a rapid exothermic reaction. 
Upon the gas-liquid contact reaction with sulfur trioxide, the film 
thickness, or the flow quantity, of the organic liquid to be sulfonated 
has to be maintained uniform. Otherwise, the resulting final product is 
too coloured. In a conventional sulfonation apparatus, however, 
difficulties were encountered in maintaining the film thickness or the 
quality of the organic liquid, for which reason the quality of the 
resulting final product failed to be satisfactory. 
As a result of having conducted detailed studies on the reason why the 
final product obtained by the conventional sulfonation apparatus was 
coloured, it has been determined that there exist various reasons or 
causes including the following. 
The conventional sulfonation apparatus is generally so constructed that an 
organic liquid is allowed to flow in the form of a thin film down two 
externally cooled, substantially concentric, circular reaction surfaces 
from a circular slit opening located on an upper part of said reaction 
surfaces, and is allowed to contact the sulfur trioxide introduced in 
parallel-flow relation to the organic liquid. A typical example thereof is 
disclosed in detail, for example, in U.S. Pat. No. 3,620,684. The organic 
liquid-feeding opening used in the above-mentioned conventional 
sulfonation apparatus is of a horizontally circular slit shape and has no 
vertical partition. By adjusting the vertical clearance of the slit, the 
film thickness or flow quantity of the organic liquid is so controlled as 
to be made uniform at all points of the reaction surface. Since, however, 
the circular slit opening has as large a diameter as, for example, 500 mm 
to 600 mm, even a small error in terms of the vertical clearance of slit 
results in a large difference in terms of film thickness between both ends 
of the slit diameter. For example, even such a small error as .+-.0.01 mm 
results in about 10% of error in terms of flow quantity. 
In order to remove the foregoing drawbacks to prevent a final product from 
being coloured, several improvements have thereafter been proposed. For 
example, U.S. Pat. No. 3,677,714 discloses the formation of a uniform film 
of organic liquid on the reaction surface by providing a porous substance 
for the organic liquid-feeding opening, while U.S. Pat. No. 3,879,172 
discloses the same formation by providing a net for the organic 
liquid-feeding opening. But, when it is desired to form, in such cases, a 
uniform film of organic liquid over an entire area of circular reaction 
surface, some pressure loss is required to exist between the pressure at 
the front of the porous substance or net and that at the back thereof. 
Accordingly, the pore size of the porous substance or the mesh size of the 
net is made small. This is apt to cause the occurrence of clogging. 
Therefore the film thickness of the organic liquid becomes likely to be 
non-uniform. With the passage of operation time, therefore, a sulfonation 
product comes to be coloured, so that a long-time operation is difficult. 
Accordingly, an object of the invention is to provide an apparatus for 
continuous sulfonation eliminating the above-mentioned drawbacks of the 
conventional sulfonation apparatus to produce a final product of high 
quality. 
Another object of the invention is to provide an apparatus for continuous 
sulfonation with a feeding device, which enables the formation of a 
uniform thin film of organic liquid. 
The apparatus for continuously sulfonating an organic liquid by the use of 
a gaseous sulfonating agent in accordance with the object of the invention 
is constructed such that, for the purpose of permitting the organic liquid 
to be sulfonated to flow in the form of a thin film down a vertically 
extending, cylindrical reaction surface, an annular feeding device having 
a number of slots horizontally equidistantly arranged in a row is provided 
at an upper end of the cylindrical reaction wall. As for this annular 
feeding device, the vertical clearance a of opening of such slot, the 
interval b between adjacent two of the slots and the horizontal width c of 
opening of each slot are so selectively determined that the percentage of 
slot area exposed by the formula: 
##EQU1## 
ranges from 40% to 90%. 
This invention can be more fully understood from the following detailed 
description when taken in conjunction with the accompanying drawings, in 
which: 
FIG. 1 is a vertical sectional view of an example of an apparatus for 
continuous sulfonation according to the invention; 
FIG. 2 is a perspective view of an annular feeding device for feeding 
organic liquid according to the invention; and 
FIG. 3 is a vertical sectional view taken along line X-X' of FIG. 2.

The above-mentioned annular feeding device for feeding organic liquid is 
provided at the upper end of a cylindrical reaction wall. Slightly below 
the annular feeding device is opened an annular nozzle for feeding sulfur 
trioxide in parallel-flow relation to a downflow film of the organic 
liquid. 
In the annular feeding device of the invention, the vertical clearance a of 
opening of each slot is preferably in the range of 0.2 mm to 1.0 mm. Where 
the a is smaller than 0.2 mm, the slot becomes likely to be subject to 
clogging and the manufacturing precision is not sufficiently increased. In 
contrast, where the a exceeds 1.0 mm, the pressure loss is decreased to 
make the flow quantity nonuniform, thereby to undesirably influence the 
sulfonation reaction. 
The interval b between adjacent two of the slots is preferably in the range 
of 1 mm to 5 mm. Where the b exceeds 5 mm, the cylindrical reaction 
surface comes to have the portions which fail to be covered with the 
organic liquid, so that the resulting final product is coloured. In 
contrast, where the b is smaller than 1 mm, difficulties are encountered 
in manufacturing the apparatus although no undesirable effect acts on the 
formation of a uniform thin film of the organic liquid. 
Preferably, the slot is of a rectangular shape. But this invention is not 
limited thereto and includes a slot both upper angles of whose rectangular 
shape are round, a semicircular slot, etc. Those skilled in the art would 
be able to easily apply this invention to these slots. 
The percentage of area of the slots provided, as above described, in the 
annular feeding device in a row and in a horizontal and equidistant manner 
is in the range of 40 to 90%, or preferably 50 to 90%. This percentage of 
slot area is expressed as follows. 
##EQU2## 
where a represents the vertical clearance of opening of the slot, b the 
interval between adjacent two of the slots, and c the horizontal width of 
the slot. 
Where the percentage of slot area is less than 40%, it is difficult to form 
a uniform thin film of organic liquid on the cylindrical reaction surface. 
On the contrary, where the percentage of slot area exceeds 90%, small 
errors in terms of the vertical clearance of the slot remarkably influence 
the quantity of flow and the pressure loss becomes extremely small. As a 
result, a uniform thin film of organic liquid is not obtained. In order to 
form a stable uniform film of organic liquid by using the annular feeding 
device of the invention, pressure loss is always needed. 
The quality of material of which the annular feeding device of the 
invention is formed has to be inactive against the organic liquid to be 
sulfonated and preferably includes stainless steel, bronze, plastic 
material, etc. 
The apparatus for continuous sulfonation according to the invention can be 
widely used for sulfonation of the organic liquid by sulfur trioxide, and 
is more preferably used for sulfonation of alkylbenzene having an alkyl 
group having eight to 15 carbon atoms, olefinic hydrocarbons having 10 to 
24 carbon atoms such as .alpha.-olefin, inner-olefin or vinylidene type 
olefin, aliphatic alcohol having nine to 16 carbon atoms, alkylphenol 
having alkyl group having six to 14 carbon atoms added with 1 to 10 mols 
of ethylene oxide, aliphatic alcohol having nine to 19 carbon atoms added 
with 1 to 10 mols of ethylene oxide, or lower (C.sub.1 to C.sub.4) alcohol 
ester of fatty acid having eight to 20 carbon atoms. Besides, aromatic 
hydrocarbon such as benzene, toluene or xylene can also be used as the 
organic liquid to be sulfonated. 
The above-mentioned organic liquids to be sulfonated are fed to the 
apparatus for continuous sulfonation at the rate of 50 to 500 kg/m.hr (the 
weight of the organic liquid flowing per hour and per meter of the 
circumferential length of the cylindrical reaction surface). In the 
apparatus for continuous sulfonation, the molar ratio of SO.sub.3 as a 
sulfonating agent to the organic liquid to be sulfonated is preferably in 
the range of 0.90 to 1.30. The SO.sub.3 to be fed is usually diluted by 
air or an inert gas such as nitrogen gas so as to account for 1 to 12% by 
volume of a total amount of the resulting gas, and the flow rate of the 
SO.sub.3 gas when it contacts the organic liquid is preferably in the 
range of 20 to 100 m/sec. 
The above sulfonation is an exothermic reaction, and sometimes the 
temperature of the reaction product immediately after the commencement of 
the reaction is raised up to nearly 100.degree. C. In order to suppress 
such temperature elevation and maintain the reaction temperature at about 
30.degree. C. to 80.degree. C., the reaction wall is provided with a 
cooling jacket to be cooled by water or cooling medium. Subsequently, the 
sulfonated organic liquid such as alkylbenzene is neutralized by, for 
example, caustic alkali or organic base, whereby a surface-active agent is 
produced. 
In FIG. 1 showing an example of the apparatus for continuous sulfonation 
according to the invention, the apparatus 1 is substantially cylindrical 
and is constructed such that two externally cooled cylindrical reaction 
walls, namely an outer reaction wall 2 and an inner reaction wall 3, are 
vertically and concentrically disposed with their respective reaction 
surfaces opposed to each other. The cylindrical reaction walls 2, 3 are 
provided with cooling jackets 4, 5 respectively, and for removing the 
reaction heat the water or cooling medium is fed from the bottoms of the 
jackets and is allowed to rise while being revolved by baffle plates 6 and 
is discharged to the exterior from cooling water discharge pipes 7, 8 
respectively. 
The organic liquid to be sulfonated such as .alpha.-olefin having 10 to 24 
carbon atoms is introduced from an inner raw material feed pipe 9 and 
outer raw material feed pipes 10, 10'. The organic liquid introduced from 
the inner raw material feed pipe 9 flows in the form of a thin film down 
the reaction surface of the inner reaction wall 3 from an inner annular 
feeding device 12 through a circular chamber 11. Similarly, the organic 
liquid introduced from the outer raw material feed pipes 10, 10' flows in 
the form of a thin film down the reaction surface of the outer reaction 
wall 2 from an outer annular feeding device 14 through a circular chamber 
13. 
The sulfur trioxide as a gaseous sulfonating agent is fed from a SO.sub.3 
gas feeding pipe 15 and is introduced into a reaction zone 17 from an 
annular SO.sub.3 -feeding nozzle 16 inserted between the two reaction 
walls 2, 3. Preferably the opening position of the annular SO.sub.3 
-feeding nozzle 16 is situated slightly below the annular feeding devices 
12, 14. The SO.sub.3 gas introduced into the reaction zone 17 acts on a 
thin film of organic liquid from immediately below the nozzle 16 to 
sulfonate it. While the organic liquid is flowing down the reaction 
surfaces, said sulfonation is completed. The sulfonated organic liquid is 
taken out from a product take-out pipe (not shown) provided below the 
reaction zone 17. 
FIG. 2 is a perspective view of an annular feeding device according to the 
invention. FIG. 3 is a longitudinal sectional view taken along the line 
X-X' of FIG. 2. As shown, an annular feeding device 20 has a number of 
slots 21 provided in a row in a horizontal and equidistant manner. 
Preferably, the thickness D of an annular wall 23 of the annular feeding 
device 20 is in the range of about 3 mm to 15 mm. As seen from FIG. 3, the 
slots 21 are provided through the annular wall 23. Where the annular 
feeding device 20 is the above-mentioned inner feeding device, an organic 
liquid to be sulfonated is fed to the inside of this device and is passed 
through the slots 21 to flow in the form of a thin film down the outer 
surface 24 of the device and further flow down the reaction surface of the 
inner reaction wall 3 so provided that its surface is in alignment with 
the outer surface 24. Where the annular feeding device 20 is the 
above-mentioned outer feeding device, the organic liquid is fed to the 
outside of this device and is passed through the slots 21 to flow down the 
inner surface 25. 
In FIG. 3, a represents the vertical clearance of the opening of each slot, 
b the interval between adjacent two of the slots, and c the horizontal 
width of the opening of each slot. 
The annular feeding device 20 according to the invention is prepared by 
subjecting one end of the annular wall 23 to precision fabrication into a 
comb-like configuration and connection an annular member 26 with said one 
end thus formed. Upon horizontally installing the annular feeding device 
on the apparatus for continuous sulfonation, said contact-bonding may be 
effected, for example, by bolts. In the case of the inner annular feeding 
device, a circular plate can also be used for the annular member 26. The 
annular feeding devices are used in the same number as that of the 
reaction walls, and generally two annular feeding devices are used per 
apparatus for continuous sulfonation. 
The use of the present apparatus using the above-mentioned annular feeding 
device always permits the formation of a uniform thin film of organic 
liquid on the reaction surface, so that the resulting product is 
non-coloured and little accompanied by the formation of by-products, and 
thus a high quality of sulfonated product is obtained. Unlike the 
conventional apparatus using a feeding device such as a net, the present 
apparatus has the slots free from clogging of minute dusts or impurities 
contained in the organic liquid and therefore can be subject to a long, 
stable continuous operation. 
The present apparatus for continuous sulfonation is mainly suitable to the 
production of a surface-active agent and is further suitable to the 
sulfonation for production of ordinary dyes or medicines. 
The uniformity of the thin film of organic liquid formed on the reaction 
surface was measured by the following experiments: 
The uniformity of thin films of organic liquid formed on the reaction 
surfaces by using the present apparatus provided with the annular feeding 
devices and the conventional apparatus provided with a slit opening, 
respectively, were determined by measurement of flow quantity. Measurement 
was made at a respective one of eight positions of the inner reaction 
surface (76 mm in diameter) corresponding to those of the outer surface of 
the inner annular feeding device which were respectively vertically 
downwardly spaced 5 cm from the eight positions obtained by dividing said 
outer surface of the device into eight equal parts. The error of the flow 
quantity from which the uniformity of the resulting thin film is 
determined is calculated by the following equation. 
##EQU3## 
The organic liquid used was .alpha.-olefin having 16 to 18 carbon atoms 
(having an average molecular weight of 235). The configuration of the 
annular feeding devices used and the results of measurement are presented 
in Table 1 below. 
Table 1 
__________________________________________________________________________ 
Annular feeding 
Apparatus for continuous sulfonation 
Prior 
device provided with annular feeding devices 
art 
__________________________________________________________________________ 
a (mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.3 
b (mm) 3 3 3 3 3 3 3 (slit) 
Percent of 
slot area (%) 
35 40 50 67 80 90 95 100 
Pressure drop 
.DELTA.p(mm H.sub.2 O) 
48 46 44 32 22 19 17 37 
Errors of flow 
quantity at 
respective 
measuring posi- 
tions 
Measuring 
1 +1.5 
+0.5 
+0.2 
0 -0.7 
-0.5 
+2.1 
+25.5 
position 
" 2 +2.6 
+0.7 
+0.1 
-0.1 
0 -0.3 
-0.6 
-5.2 
" 3 -3.2 
-2.5 
0 +1.7 
+1.5 
0 -2.5 
-2.5 
" 4 -2.9 
-1.7 
-2.1 
+1.0 
-0.9 
+2.5 
-2.6 
+10.3 
" 5 +3.8 
+2.6 
+1.5 
-1.6 
-0.1 
+2.1 
-2.4 
-20.2 
" 6 -3.5 
- 1.5 
0 -0.5 
0 -1.8 
+0.8 
-3.5 
" 7 -1.3 
+2.1 
-1.0 
0 -0.2 
-1.9 
+2.3 
+3.4 
" 8 +3.0 
-0.2 
+1.3 
-0.5 
+0.4 
-0.1 
+2.9 
-7.8 
__________________________________________________________________________ 
As seen from Table 1, the conventional apparatus provided with a slit 
opening indicated a large variation in the flow quantity on the reaction 
surface, whereas the present apparatus provided with the annular feeding 
devices each having a slot area of 40 to 90% indicated a very uniform 
quantity of flow, whereby an excellent quality of sulfonated product was 
obtained. 
EXAMPLE 1 
By the use of the present apparatus for continuous sulfonation provided 
with the annular feeding devices, the .alpha.-olefin having 16 to 18 
carbon atoms (having an average molecular weight of 235) was sulfonated by 
SO.sub.3 gas. For comparison, a similar test was carried out by using the 
conventional apparatus provided with a slit-like opening. Both tests were 
performed under the condition wherein the length of reaction wall was 2 m; 
the amount of .alpha.-olefin fed was 250 kg/m.hr.; the molar ratio of 
SO.sub.3 to .alpha.-olefin was 1.14; the temperature of cooling water of 
water-cooling jacket was 20.degree. C.; and the temperature of sulfonation 
reaction was 55.degree. C. to 60.degree. C. The results from the 
above-sulfonated products are presented in Table 2. 
Table 2 
__________________________________________________________________________ 
Annular feeding 
Apparatus for continuous sulfonation 
Prior 
device provided with annular feeding devices 
art 
__________________________________________________________________________ 
a (mm) 0.4 0.4 0.4 0.4 0.4 0.4 0.3 
b (mm) 3 3 3 3 3 3 (slit) 
Percentage of 
slot area (%) 
40 50 67 80 90 95 100 
Quality of 
sulfonated pro- 
duct 
Content of 
unreacted 
2.70 
2.68 
2.71 
2.72 
2.70 
2.75 
2.9 
oil (wt %)*1 
colouring *2 
0.125 
0.115 
0.110 
0.110 
0.120 
0.150 
0.205 
Content of 
disulfonate 
8.0 8.1 7.5 7.9 8.0 8.5 10.1 
*3 
__________________________________________________________________________ 
Note: 
*1 Petroleum ether extract (active basis) (Hereinafter the same as this) 
*2 25% concentration, absorbance (or light absorption), 10mm Cell, 420 
m.mu. (Hereinafter the same as this) 
*3 Weight % of disulfonate contained in the surface-active agent 
(Hereinafter, the same as this) 
As apparent from Table 2, the surface-active agent produced by the present 
apparatus is much less coloured than that produced by the conventional 
apparatus, and is not excessively sulfonated to be of a very excellent 
quality. 
EXAMPLE 2 
By the use of the present apparatus provided with the annular feeding 
devices of Example 1 having a slot area of 67%, sulfonation was carried 
out, using a aliphatic alcohol having 12 carbon atoms (having a molecular 
weight of 204) as the organic liquid to be sulfonated, in the same manner 
as in Example 1 except for the following conditions: 
______________________________________ 
Molar ratio of SO.sub.3 
1.03 
Amount of aliphatic alcohol 
250 kg/m. hr 
fed 
Amount of diluting air 3 Nm.sup.3 /min. 
Temperature of cooling water 
25.degree. C. 
______________________________________ 
The results being presented in Table 3, together for comparison with the 
results obtained with the same conventional apparatus having a slit-like 
opening as used in Example 1. 
Table 3 
______________________________________ 
Quality of surface-active agent 
This invention 
Prior art 
______________________________________ 
Content of unreacted 
2.80 2.95 
oil (wt %) 
Colouring (10% aqueous 
0.11 0.19 
solution) 
Inorganic salt (wt %)*4 
0.45 0.56 
______________________________________ 
Table 3 shows that the present apparatus for continuous sulfonation is very 
excellent as compared with the conventional apparatus. 
EXAMPLE 3 
By the use of the present apparatus provided with the annular feeding 
devices having an a of 0.6 mm, a b of 4 mm, and a slot area of 67 %, 
sulfonation was carried out using as the organic liquid to be sulfonated 
an alcohol ethoxylate added with 3 mols of ethylene oxide (a molecular 
weight of 330) in the same manner as in Example 1 except for the following 
conditions: 
______________________________________ 
Molar ratio of SO.sub.3 
1.03 
Amount of alcohol ethoxylate 
300 kg/m.hr 
fed 
Amount of diluting air 3 Nm.sup.3 /min. 
Temperature of cooling water 
25.degree. C. 
______________________________________ 
For comparison, by the use of the conventional apparatus provided with a 
slit opening the vertical clearance a of which is 0.4 mm, a similar 
experiment was made, the results being shown in Table 4 together with the 
results obtained with the above present apparatus. 
Table 4 
______________________________________ 
Quality of surface-active agent 
This invention 
Prior art 
______________________________________ 
Content of unreacted 
2.10 2.15 
oil (wt %) *5 
Colouring 
(10% aqueous solution) 
0.010 0.020 
Inorganic salt (wt %) 
0.30 0.32 
______________________________________ 
Note: 
*5 ion-exchange resin method 
EXAMPLE 4 
Sulfonation was carried out in the same manner as in Example 2 except for 
the use of an alkylbenzene (having a molecular weight of 243) as the 
organic liquid to be sulfonated and the following conditions. The 
conventional apparatus used for comparison was the same as that used in 
Example 2. 
______________________________________ 
Molar ratio of SO.sub.3 
1.05 
Amount of alkylbenzene 300 kg/m.hr 
feed 
Amount of diluting air 3 Nm.sup.3 /min. 
Temperature of cooling water 
20.degree. C. 
______________________________________ 
The results in both cases are indicated in Table 5 below. 
Table 5 
______________________________________ 
Quality of surface-active agent 
This invention 
Prior art 
______________________________________ 
Content of unreacted petroleum 
1.30 1.35 
oil (wt %) 
Colouring 
(10% aqueous solution) 
0.010 0.015 
Inorganic salt (wt %) 
1.25 1.20 
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