Page 6 - Microsoft Word - Sulfo and Sulfa 1.doc

Figure 6. Chlorosulfonic Acid Sulfation

O
H - O - S - Cl + CH - (CH ) - CH - OH
3
2 10
2
O
Chlorosulfonic Lauryl alcohol
acid

O
–
+
CH - (CH ) - CH - O - S - O H + HCl
2 10
3
2
O
Lauryl alcohol Hydrochloric
sulfuric acid acid

Sulfuric acid (H SO ) and oleum (SO • H SO ) are widely used as sulfonating agents.
2
4
4
2
3
Oleum is used to sulfonate alkyl benzene and sulfate fatty alcohols for heavy duty
detergents. The reaction is shown in Figure 7. It is an equilibrium process, as water is
formed in the reaction and the resultant water dilutes the oleum and/or sulfuric acid. The
sulfonation reaction stops when
the sulfuric acid concentration
drops to approximately 90%. This Figure 7. Sulfuric Acid / Oleum
"spent" acid may be separated
from alkyl benzene sulfonic acid O
to produce a product, which on H - O - S - O - H + (CH ) - CH 3
2 11
neutralization contains a relatively O
low level (6-10%) of sodium Sulfuric acid Alkyl benzene
sulfate. When fatty alcohols are
sulfated, the spent acid cannot be
separated. It must be neutralized O
with the alcohol sulfuric acid to H O - S (CH ) - CH + H O
–
+
make a product containing a high 2 11 3 2
level of sodium sulfate. Oleum is O
relatively inexpensive – about Alkyl benzene sulfonic acid Water
US$0.153 per pound of reactive
SO . Oleum sulfonation can be
3
operated as either a batch or continuous process. This process has the dual advantage of
low SO cost and low capital equipment cost. However, it has the disadvantage of being
3
an equilibrium process which leaves large quantities of un-reacted sulfuric acid. This

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