Page 4 - Microsoft Word - Sulfo and Sulfa 1.doc

side reactions that produce undesirable by-products. Also, precise control of the molar
ratio of SO to organic is essential because any excess SO , due to its reactive nature,
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contributes to side reactions and by-product formation. Therefore, commercial scale
sulfonation reactions require special equipment and instrumentation that allows tight
control of the mole ratio of SO to organic and rapid removal of the heat of reaction.
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Historically, the problem of SO reactivity has been solved by diluting and/or
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complexing the SO to moderate the rate of reaction. Commercially, the diluting or
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complexing agents (Figure 4) include ammonia (sulfamic acid), hydrochloric acid
(chlorosulfuric acid), water or sulfuric acid (sulfuric acid or oleum) and dry air (air/SO
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film sulfonation). Control of the ratio of SO to organic raw material is vital to achieving
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the desired product quality with use of any of the agents. Additionally, these processes
require heat removal to maintain product quality. As we examine each of these industrial
processes we will see how they have been engineered to achieve these requirements.

Figure 4. Agents to Reduce SO 3 Reactivity

X Ammonia O
NH + SO 3 HO - S - NH 2 Sulfamic Acid
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O

X Hydrochloric Acid O
HCl + SO 3 H - O - S - Cl Chlorosulfonic Acid
O

X Water O O
H O + SO 3 H-O-S-O-H + SO 3 SO H-O-S-O-H
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3
O O
Sulfuric Acid Oleum
X Dry Air
Dry Air + SO 2.5 to 8% SO in Dry Air
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Commercial Sulfonation Processes

Sulfamic acid (NH SO H) is used to sulfate alcohols and ethoxylated alcohols to form an
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ammonium neutralized salt. A typical reaction is shown in Figure 5. The reaction goes

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