Sulphonic acids and sulphonates

Sulphonic acids and sulphonates containing olefines and optionally water which improve color and thermal stability and also simplify purification of the acid.

The present invention relates to alkylaryl sulphonic acids and sulphonates. 
In one aspect the invention is concerned with stabilising the sulphonic 
acid to inhibit the formation of undesirable coloration which appears in 
sulphonates upon neutralisation of sulphonic acids that have been stored. 
In another aspect the invention is concerned with retarding the thermal 
degradation of alkylaryl sulphonic acids to sulphuric acid that occurs on 
ageing. In one further aspect the invention is directed at simplifying the 
purification process that is currently needed in the production of 
alkylaryl sulphonic acids. 
Whilst the present invention is applicable to alkylaryl sulphonic acids in 
general it is especially applicable to those containing comparatively long 
chain (i.e. 18 or more carbon atoms) alkyl groups where the problems of 
purification and colour and thermal stability are that much more acute. 
Alkylaryl sulphonic acids are generally produced by first alkylating the 
chosen aryl compound with an olefin by reaction in the presence of an 
alkylation catalyst such as boron trifluoride or aluminium trichloride. 
The alkyl aryl compound is then sulphonated by reaction with sulphuric 
acid, with oleum, with gaseous trioxide or with a mixture of sulphur 
trioxide dissolved in sulphur dioxide, this latter process being 
preferred. The product of the sulphonation is the crude sulphonic acid 
mixed with the sulphonation agent and a mixture of other residues known as 
sludge. 
In the preferred process where sulphur dioxide is present the sulphonic 
acid is purified by first stripping to remove the residual sulphur 
dioxide. The material left after this stripping is then decanted with a 
hydrocarbon solvent such as hexane to cool and liberate the hexane 
insoluble byproducts known as sludge. From about 0.5% to 1.5 wt.% of 
sulphuric acid is left in the sulphonic acid and this is then removed by 
washing with aqueous hydrochloric acid solution. 
Thus, as may be seen, the process required for purifying the alkylaryl 
sulphonic acids in complex and therefore expensive. The purification 
problems vary with the length and configuration of the alkyl chain in the 
alkylarylsulphonic acids but despite the elaborate purification techniques 
described above the sulphonic acids still tend to degrade thus decreasing 
the sulphonic acid concentration with an increase in sulphuric acid 
content which is undesirable. In addition ageing of the sulphonic acids 
tends to result in discoloration upon neutralisation to form sulphonates 
at ambient temperature and particularly at the elevated temperatures 
sometimes required for storage and/or transportation of the sulphonates. 
Various methods have been proposed for retarding the development of colour 
and/or the thermal degradation of alkylaryl sulphonic acids. For example 
U.S. Pat. No. 3,681,443 states that .alpha.-B unsaturated carboxylic acids 
or their anhydrides may be added to sulphonic acids. This patent is 
primarily concerned with alkylaryl sulphonic acids where the alkyl chain 
is comparatively short (around twelve carbon atoms) and we have not found 
these techniques effective with higher molecular weight materials. In our 
own Patent Application No. 5100/75 we show that the problems of colour 
formation in alkylaryl sulphonic acids may be reduced by incorporating an 
ether in the sulphonic acid. 
We have now found that the problems of undesirable development of colour in 
sulphonic acids may be significantly reduced at ambient and elevated 
temperatures by incorporating an olefin in the sulphonic acid and 
furthermore that the purification process may not be needed if the olefin 
is incorporated into the crude sulphonic acid obtained from the 
sulphonation process. We have in addition found that the stability of the 
sulphonic acid is further improved, particularly the thermal stability if 
water is present in the sulphonic acid as well as the olefin. Addition of 
water to sulphonic acids is known from U.K. Pat. No. 804389 but we have 
found that for the desired improvement in thermal stability both olefin 
and water should be present. containing at least 1% by weight of an olefin 
based on the weight of the sulphonic acid. 
In a second aspect the present invention further provides an alkylaryl 
sulphonic acid containing at least 1% by weight of an olefin and at least 
1% by weight of water based on the weight of the sulphonic acid. 
The sulphonic acids of the present invention are suitable for reaction with 
bases to form sulphonates thus in a further aspect the present invention 
provides alkylaryl sulphonates containing at least 1% by weight of an 
olefin based on the weight of sulphonic acid from which the sulphonate is 
derived. 
In yet another aspect the present invention provides an alkylaryl 
sulphonate containing at least 1% by weight of an olefin and at least 1% 
of water based on the weight of the sulphonic acid from which the 
sulphonate is derived. 
We have found that the colour stability of the alkylaryl sulphonic acid can 
be improved by incorporating the olefin at any stage of the sulphonation 
process although we prefer it be incorporated after sulphonation since 
incorporation before or during sulphonation tends to reduce the yield of 
sulphonic acid. We find that the thermal stability can be improved by 
incorporating the water at any stage after sulphonation providing the 
final sulphonic acid also contains the olefin. 
Thus the present invention provides a process for improving the colour 
stability of an alkylaryl sulphonic acid comprising incorporating at least 
1% by weight of an olefin into the sulphonic acid or during the 
sulphonation process, the weight of olefin being based on the weight of 
the resulting sulphonic acid. Within this process if it is desired to also 
increase the thermal stability of the sulphonic acid at least 1% by weight 
of water based on the weight of the sulphonic acid, may also be included 
any time from after sulphonation to shortly after the completion of 
purification. In our preferred process the olefin and the water are added 
together sometime after sulphonation. 
We have further found that when sulphonation is effected with sulphur 
trioxide dissolved in sulphur dioxide the need for purifying the alkylaryl 
sulphonic acid so produced can be obviated if after sulphonation the 
sulphur dioxide is removed whilst an olefin is present. Thus, in one 
further aspect the present invention provides a process for stabilising an 
alkylaryl sulphonic acid which has been prepared by sulphonating an 
alkylaryl hydrocarbon with sulphur trioxide dissolved in sulphur dioxide 
and wherein the sulphur dioxide is removed after sulphonation 
characterised by removing at least part of the sulphur dioxide whilst the 
product of sulphonation contains at least 1% by weight of an olefin based 
on the weight of sulphonic acid. 
Sulphonates are produced by neutralisation of the sulphonic acids and thus 
the present invention further provides a process for the production of 
sulphonates comprising neutralising sulphonic acids with base in the 
presence of at least 1% by weight of the sulphonic acid of an olefine. 
In addition the invention provides a process for the production of 
sulphonate comprising neutralising sulphonic acids with base said 
sulphonic acid containing at least 1% of its weight of an olefin and at 
least 1% of its weight of water. 
The techniques of our invention are generally applicable to alkylaryl 
sulphonic acids including acids derived from mono- or poly- nuclear 
aromatic compounds. The invention is however primarily concerned with 
sulphonic acids derived from mono-nuclear aromatic compounds; the aromatic 
nucleus may contain the single alkyl group as in the alkyl benzenes or two 
alkyl groups such as in the alkyl toluenes or three alkyl groups such as 
for example in the alkyl xylenes. Thus the sulphonic acid may be of the 
formula: 
##STR1## 
where R.sup.1 and R.sup.2 may be hydrogen or hydrocarbyl groups and R is 
an alkyl group which preferably contains from 7 to 30 carbon atoms. 
Although the techniques of our invention are applicable to sulphonic acid 
in which R is a comparatively short chain alkyl group such as from C.sub.7 
to C.sub.15 they prove especially useful with the sulphonic acids in which 
R is longer chain such as from C.sub.20 to C30 which require special 
purification techniques. We find the techniques of our invention to be 
particularly suited to the production of sulphonic acids based on alkyl 
aryl compounds in which the alkyl group contains from 20 to 30 carbon 
atoms. 
Any suitable olefin may be used in the technique of our invention, but we 
prefer to use a liquid olefin and the choice naturally is a question of 
economics. 
The particular olefin that should be used will depend upon the nature of 
the sulphonic acid and the preferred olefine may be found by 
experimentation to determine which olefine is most effective at reduction 
of sludge and sulphuric acid together with improved colour stability in 
the particular acid. We have found, for example, that an olefine of 
molecular weight from 294 to 336 is most suitable for use with a C.sub.24 
alkyl benzene sulphonic acid. We prefer to use a mono-olefine since 
di-olefines are more expensive and although they impart some improvement 
to the sulphonic acid and sulphonates we find them less effective than 
mono-olefines. 
We have found however that propylene oligomers especially trimers, 
tetramers and octamers are particularly suitable more so since they tend 
to be readily available. Since for many applications sulphonic acids are 
used as solutions in oil it is preferred that the olefin be oil soluble 
and thus olefins containing from 9 to 30 carbon atoms are especially 
suitable, those containing from 12 to 24 carbon atoms being most 
preferred. The quantity of olefin that is used depends upon the degree of 
stability required, the nature of the sulphonic and the time during the 
process in which it is added. Again for economic reasons we prefer to use 
as little as possible although we find at least 1% by weight should be 
used preferably from 2% to 10% by weight more preferably from 3% to 6% by 
weight. As mentioned sulphonic acids are often supplied as concentrates in 
an oil and in certain instances the olefin may replace part or all of the 
oil and in this instance more than 10% will be present. 
No special blending techniques are required and the olefin may be 
incorporated to improve the colour stability of the sulphonic acid it may 
be included at any time during or immediately after the production of the 
sulphonic acid. However, we have found that if the olefin is present 
during removal of the sulphur dioxide when the alkylaryl compound has been 
sulphonated with a solution of sulphur trioxide in sulphur dioxide then 
the amount of sludge that remains after removal of the sulphur dioxide is 
considerably reduced as is the amount of sulphuric acid. We have found in 
certain instances that the reduction in sludge and sulphuric acid even in 
the production of sulphonic acids based on the longer chain alkylates is 
sufficient that it may not be necessary to remove sludge by decanting with 
a hydrocarbon solvent or to wash with aqueous hydrochloric acid solution 
to remove sulphuric acid. As can be seen this would lead to a considerable 
simplification of the process for manufacturing sulphonic acids. We also 
find that within normal operating limits the temperature at which the 
olefine is mixed with the sulphonic acid is not critical. 
Where the olefin is added prior to or during removal of the sulphur dioxide 
the olefin must not of course be removed with the sulphur dioxide. Thus, 
in this instance the olefin should not boil under the conditions that are 
applied during removal of the sulphur dioxide. 
As with the olefin it is not necessary to use any particular conditions to 
incorporate the water into the sulphonic acid. Thus when water is used it 
may be introduced together with the olefin or the two introduced 
separately. As with the olefin the amount of water that is used depends on 
the degree of stability required, the nature of the sulphonic acid and the 
time during the process in which it is added. We find however that where 
improved thermal stability is required at least 1% by weight of water 
should be used and preferably no more than 5% since more than 5% can 
amount to an undesirable dilution of the acid and can lead to processing 
and storage problems. 
Sulphonic acids are generally neutralised to give sulphonates that are used 
as detergents where they are generally used as their salts with alkali 
metals, generally sodium, or with quarternay nitrogenous cations. 
Sulphonates with the longer alkyl chain lengths may be used as emulsifiers 
in the formation of oil in water emulsions as for example in lubricating 
oils for metal working; here again the sulphonates are usually the sodium 
or ammonium salts including ethoxylated ammonium salts. Sulphonic acids 
are also used in the production of highly basic sulphonates of the type 
that are used as detergent additives in lubricating oils. In this instance 
the sulphonates are normally highly basic calcium, magnesium or barium 
salts. The sulphonic acids are generally supplied as solutions in oils, 
which may be concentrates and the nature of the oil is not important 
although we prefer to use the well-known paraffinic mineral oils. The 
concentrates preferably contain from 50% to 95% by weight usually 65% to 
90% by weight of the sulphonic acid. 
The present invention is illustrated but in no way limited by referece to 
the following Examples some of which are by way of comparison. In these 
Examples the colour was determined by forming the sodium salt by 
neutralising a 7% active ingredient solution of the acid with an excess of 
a solution of 40% sodium hydroxide and heating to 130.degree. C. to boil 
off the water formed. The colour of this freshly formed sodium sulphonate 
was then measured by the ASTM test D-1500-64 as reapproved in 1973. 
The thermal stability of the sulphonic acids was determined by storing the 
acids at certain temperatures for certain lengths of time and measuring 
the decrease in sulphonic acid content over that period of time. The acid 
content is measured by dissolving one gram of the acid in 10 cc's of 91% 
isopropyl alcohol adding 90 cc's of water and 4 to 5 drops of phenol 
phthaline and titrating with N/10 potassium hydroxide until just pink. 
This solution is then acidified with N/2 hydrochloric acid until the clear 
colour returned. 25 cc's of a solution of the hydrochloride of 
paratoluidene (8 grams in 100 cc's) are then added and the mixture 
extracted three times with carbon tetrachloride. The remaining solution of 
the acid is mixed with 100 cc's of 91% isopropyl alcohol and 9 to 10 drops 
of meta cresol and titrated with N/10 potassium hydroxide until the 
solution just turns grey. 
The acid index (milligrams) is 
EQU C .times. V.sub.1 .times. 56.1/1000 .times. m .times. 1000 
where 
m is original weight of the acid 
C is normality of the potassium hydroxide 
V.sub.1 is total original volume of potassium hydroxide 
the % of sulphonic acid present is: 
EQU C .times. V.sub.2 .times. M.sub.w /1000 .times. m .times. 100 
where 
V.sub.2 is volume of second charge of potassium hydroxide 
C is normality of second charge of potassium hydroxide 
M.sub.w is molecular weight of the sulphonic acid 
the % of sulphuric acid present is: 
EQU C .times. (V.sub.1 -V.sub.2) .times. 49/1000 .times. m .times. 100 
In these Examples the weight of olefin is based on the total weight of acid 
and any diluent oil that is present.

EXAMPLE 1 
The sulphonic acid of C.sub.24 alkyl benzene was prepared by standard 
alkylation of benzene and then sulphonation of the alkylate with a 
solution of sulphur trioxide in sulphur dioxide under standard conditions. 
The sulphonic acid was purified by stripping to remove sulphur dioxide, 
decantation with hexane to remove sludge and washing with aqueous 
hydrochloric acid solution to remove sulphuric acid. 
The sulphonic acid was diluted as necessary with a paraffinic mineral oil 
of viscosity about 90 S.S.U. at 100.degree. F. to give a composition 
containing 90% by weight of sulphonic acid as active ingredient. This 
composition together with the composition to which had been added various 
amounts of a C.sub.24 olefin were stored for 4 days at 120.degree. C. and 
the colour of each sample measured after 4 days with the following 
results: 
______________________________________ 
Color after 
Initial Color 
after 4 Days at 120.degree. C 
______________________________________ 
Acid alone 3.0 4.5 
Acid + 1 wt.% olefin 
3.0 4.5 
Acid + 2 wt.% olefin 
3.0 4.5 
Acid + 3 wt.% olefin 
3.0 3.5 
Acid + 5 wt.% olefin 
3.0 3.0 
Acid + 10 wt.% olefin 
3.0 3.0 
just under 
Acid + 20 wt.% olefin 
3.0 3.0 
______________________________________ 
EXAMPLE 2 
The techniques of Example 1 were repeated with the exception that the 
sulphonic acid was diluted with the oil used in Example 1 to give a 
composition containing 70% by weight of sulphonic acid as active 
ingredient. The results were as follows: 
______________________________________ 
Color after 
Initial Color 
4 Days at 120.degree. C 
______________________________________ 
Acid alone 3.0 7.5 
Acid + wt. % olefin 
3.0 4.0 
Acid + wt. % olefin 
3.0 just under 
4.0 
______________________________________ 
EXAMPLE 3 
The sulphonic acid of C.sub.12 orthoxylene was prepared under similar 
conditions to those used to prepare the sulphonic acid of Example 1. This 
sulphonic acid is more susceptible to degradation and colour formation 
than that used in Example 1 as is shown by storing a 90% active ingredient 
composition for 6 days at 80.degree. C. which gave the following results: 
______________________________________ 
Color after 
Initial Color 
6 Days at 80.degree. C. 
______________________________________ 
Acid alone 2.5 3.0 
When the acid was blended with olefin the results were as follows: 
Acid + 1 wt.% olefin 
2.5 3.0 
Acid + 2 wt.% olefin 
2.5 3.0 (just under) 
Acid + 3 wt.% olefin 
2.5 2.5 
Acid + 5 wt.% olefin 
2.5 2.5 
Acid + 10 wt.% olefin 
2.5 2.5 (just under) 
just under 
Acid + 20 wt.% olefin 
2.5 2.5 (just under) 
______________________________________ 
EXAMPLE 4 
Tests were carried out with the acid of Example 3 diluted to 70% active 
ingredient with the oil of Example 1 and storing at 100.degree. C. for 4 
days with the following results: 
______________________________________ 
Color after 
Initial Color 
4 Days at 100.degree. C 
______________________________________ 
Acid alone 2.5 4.5 
Acid + 1 wt. % olefin 
2.5 4.0 (just under) 
Acid + 3 wt. % olefin 
2.5 3.5 
Acid + 5 wt. % olefin 
2.5 3.5 (just under) 
______________________________________ 
EXAMPLE 5 
The techniques of Example 2 were repeated using the diluent oil of Example 
1 (A), a diluent oil of viscosity 100 S.S.U. at 100.degree. F. (B) and 
also using the olefin itself as diluent. 
The various formulations were stored for 4 days at 120.degree. C. with the 
following results: 
______________________________________ 
Diluent Color 
Parts A Parts B Parts Olefin 
Initial 
After 4 Days 
______________________________________ 
1 100 -- 0 3.0 7.5 
2 95 -- 5 3.0 4.0 
3 90 -- 10 3.0 3.5 
4 75 -- 25 3.0 3.0 
5 50 -- 50 3.0 3.0 
6 0 -- 100 3.0 3.0 
7 -- 100 0 3.0 8.0 
8 -- 95 5 3.0 5.0 
9 -- 90 10 3.0 3.5 
10 -- 75 25 3.0 3.0 
11 -- 50 50 3.0 3.0 
______________________________________ 
Formulations 1, 2, 3, 6, 7, 8 and 9 were stored for one further day at 
120.degree. C. to give the following colour readings: 
______________________________________ 
Formulation Color 
______________________________________ 
1 8.0 
2 6.5 
3 6.0 
6 3.0 
7 8.0 
8 6.5 
9 6.0 
______________________________________ 
Formulation 6 had a colour of 4.5 after standing for 13 days at 120.degree. 
C. 
EXAMPLE 6 
The colour stability of the acid of Example 1 was tested using different 
olefins at varying concentrations an determining the colour after storage 
for 4 days at 120.degree. C. The results were as follows: 
______________________________________ 
Color after 4 Days at 120.degree. C. 
Olefin Used 
Quantity of Olefin % 
0 1 3 5 
______________________________________ 
C.sub.9 4.5 4.5 3.0 2.5 
C.sub.12 4.5 4.5 3.0 3.0 
C.sub.24 4.5 4.5 3.0 3.0 
C.sub.30 4.5 4.5 3.5 3.0 
______________________________________ 
EXAMPLE 7 
The acid prepared according to the process of Example 1 was analysed for 
sludge content and sulphuric acid content immediately after removal of the 
sulphur dioxide. It was found to contain 1.5 wt.% of sludge (i.e. the 
portion insoluble in hexane) and 1.5 wt.% of sulphuric acid and washing 
with aqueous hydrochloric acid solution was necessary to obtain an 
acceptable produce (low sulphuric acid content). 
Similar analyses were made on products in which certain amounts of the 
C.sub.24 olefin used in Example 1 were added to the sulphonation product 
prior to removal of the sulphur dioxide. The amounts of olefin quoted are 
based on the starting amount of the C.sub.24 alkyl benzene. 
______________________________________ 
Amount of Olefin 
3.5% 5% 7% 
______________________________________ 
Sludge wt. % 0.1 0.0 0.0 
H.sub.2 SO.sub.4 wt. % 
0.9 0.3 0.9 
Initial Color of 
3.5 2.5 1.5 
Sulphonic Acid 
______________________________________ 
There was no washing with aqueous hydrochloric acid solution in the 
preparation of these acids. 
EXAMPLE 8 
The techniques of Example 7 were repeated except that the acid that was 
tested was diluted to 70 wt.% active ingredient. The sludge, sulphuric 
acid and colour levels were all substantially the same as in Example 7. 
EXAMPLE 9 
The thermal stability of the acid of Example 2 was determined using various 
diluents by measuring the sulphonic acid content of the various solutions 
after storage for 4 days at 120.degree. C. 
______________________________________ 
Initial 
Sulphonic Acid 
Sulphonic Acid Content 
Diluent Content % After 4 Days at 120.degree. C. 
______________________________________ 
100 Parts A 
69.0 67.8% 
100 Parts B 
68.8 67.8% 
100 Parts Olefin 
68.8 67.8% 
50 Parts A 69.3 68.2% 
50 Parts Olefin 
______________________________________ 
EXAMPLE 10 
The thermal stability of the sulphonic acid of Example 1 diluted to 70% 
active ingredient with the paraffinic mineral oil of Example 1 and with 
the C.sub.24 olefin used in Example 1 were determined by measuring the 
sulphonic acid content of the solutions after various storage periods at 
certain temperatures. The results were as follows: 
______________________________________ 
Original Content After Content After 
Acid Content 5 Days at 120.degree. C. 
6 Months at 60.degree. C 
______________________________________ 
88.5% 84.7% 86.0% 
69.0% 67.7% 67.5% 
(in oil of Example 1) 
69.0% 67.7% 67.5% 
(in C.sub.24 olefin) 
______________________________________ 
EXAMPLE 11 
The acid of Example 1 (90% active ingredient) was blended with varying 
amounts of C.sub.24 olefin and water and the thermal stability of the acid 
determined by measuring the sulphonic acid content after storage with the 
following results: 
______________________________________ 
After After 
Initial 6 Weeks 5 Days 
% Sulphonic Acid 
at 80.degree. C. 
at 120.degree. C. 
______________________________________ 
Acid alone 86.5 84.9 84.7 
Acid + 2 wt.% olefin 
85 83.3 83.0 
Acid + 2 wt.% olefin 
83.0 82.5 81.7 
+ 2 wt.% water 
Acid + 2 wt.% olefin 
81.5 81.5 81.0 
+ 4 wt.% water 
______________________________________ 
EXAMPLE 12 
The tests of Example 11 were repeated using the 70% active ingredient acid 
of Example 2 with the following results: 
______________________________________ 
After After 
Initial 6 Weeks 5 Days 
% Sulphonic Acid 
at 80.degree. C. 
at 120.degree. C. 
______________________________________ 
Acid alone 69.0 68.5 67.7 
Acid + 2 wt.% olefin 
67.7 67.2 66.6 
+ 2 wt.% olefin 
66.6 66.6 66.4 
+ 2 wt.% water 
Acid + 2 wt.% olefin 
65.2 65.2 65.2 
+ 4 wt.% water 
______________________________________ 
EXAMPLE 13 
The effect of the addition of water on the colour stability of the 
sulphonic acid of Example 1 was assessed with the following results: 
______________________________________ 
Olefin wt. % added 
0.0 0.0 1.0 1.0 2.0 2.0 2.0 
Water wt. % added 
0.0 5.0 0.0 5.0 0.0 2.0 4.0 
Initial Color 
3 2.5 3 2.5 3 2.5 2.5 
Color after 3 Days 
4 4 4 4 3 3 2.5 
at 120.degree. C. 
Color after 5 days 
6 6 6 6 3.5 4 4 
at 120.degree. C. 
______________________________________ 
This shows that the addition of water does not remove the colour benefits 
of adding the olefine 
The addition of up to 4% of water alone was found to have virtually no 
effect on the thermal stability of the sulphonic acid. 
EXAMPLE 14 
The effect of the addition of water on the colour stability of the 
sulphonic acid of Example 2 was assessed with the following results: 
______________________________________ 
Olefin wt. % added 
0.0 2.0 2.0 2.0 
Water wt. % added 
0.0 0.0 2.0 4.0 
Initial Color 
3.5 3 3 2.5 
Color after 3 Days 
6.5 3 3 3 
at 120.degree. C. 
Color after 5 Days 
8.0 3.5 4.5 4 
at 120.degree. C. 
______________________________________ 
The addition of up to 5% water to the acids of Example 1 and Example 2 was 
found to have substantially no effect on product viscosity. 
EXAMPLE 15 
The effect of the molecular weight of the olefine on the development of 
sludge and sulphuric acid was assessed by adding different olefines to the 
freshly formed sulphonic acid of Example 1. 2 series of experiment were 
carried out, in the first the amount of olefine used was such as to give a 
mole amount of the olefine equivalent to using 3 wt.% of the C.sub.24 
olefine based on the weight of C.sub.24 alkyl benzene used in the 
production of the sulphonic acid. In the second series the amount of 
olefine used corresponded to 6 wt.% of the C.sub.24 olefine based on the 
weight of the C.sub.24 alkyl benzene used in the production of the 
sulphonic acid. 
The C.sub.9 and C.sub.12 olefines were commercially available materials 
sold as C.sub.9 and C.sub.12 average cuts whilst the C.sub.15 and C.sub.27 
average materials were narrow cuts obtained from distillation of a 
C.sub.24 average olefine. 
The sludge content of the acids of the two series of experiments is shown 
in the graph of FIG. 1 of the accompanying drawings as the weight percent 
of sludge based on the weight of the alkyl benzene used in the production 
of the sulphonic acid. 
The sulphuric acid content of the acids of the two series of experiments is 
shown in the graph of FIG. 2 of the accompanying drawings as the weight 
percent of sulphuric acid based on the weight of the sulphonic acid. 
EXAMPLE 16 
For the sake of comparison maleic anhydride and a C.sub.24 olefine were 
added to a 90% active ingredient and a 70% active ingredient C.sub.24 
alkyl benzene sulphonic acid prepared substantially according to Example 1 
and the colour stability measured by determining the difference in colour 
rating of sulphonate formed upon neutralisation of the freshly formed acid 
and that formed by neutralisation after storage for 4 days at 120.degree. 
C. with the following results 
______________________________________ 
2 wt % Maleic 
2 wt % C.sub.24 
No Additive 
Anhydride olefine 
______________________________________ 
90% active 
ingredient 
2 2 0.5 
70% active 
ingredient 
4 4 1 
______________________________________ 
Thus showing that the presence of maleic anhydride had substantially no 
effect on colour stability. 
EXAMPLE 17 
For the sake of comparison the techniques of Example 7 in which the olefine 
is added prior to removal of sulphur dioxide and there is no washing with 
aqueous hydrochloric acid was repeated using maleic anhydride as the 
additive. The difference in the colour rating of the sulphonate by 
immediate neutralisation of the acid and neutralisation after standing for 
4 days at 120.degree. C. were as follows: 
______________________________________ 
No 2 wt % 4 wt % 
Additives 
Maleic Anhydride 
Maleic Anhydride 
______________________________________ 
Color Change 
2 3 3 
______________________________________ 
Hereagain showing that the presence of the maleic anhydride does not 
improve but if anything worsens colour formation. 
EXAMPLE 18 
Also for comparison the techniques of Example 7 were repeated with the 
addition of maleic anhydride immediately after sulphonation and measuring 
the sludge and sulphuric acid content of the sulphonic acid. This was 
compared with a similar technique in which the C.sub.24 olefine was used 
and the results were as follows: 
______________________________________ 
2 wt % 4 wt % 
Maleic Maleic 3 wt % 
No Additive Anhydride Anhydride C.sub.24 Olefine 
______________________________________ 
Sludge 1.3 3.0 3.7 0.2 
Sulphuric 
1.2 1.8 1.8 0.4 
Acid 
______________________________________