Page 9 - Microsoft Word - Sulfo and Sulfa 1.doc

The profound effect of mole ratio on product quality implies that an air/SO sulfonation
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reactor must be designed to ensure the mole ratio is equally and constantly maintained at
all points in the reactor. I have coined the phrase "micro scale" mole ratio control to
describe this condition. Micro scale control means that the reactor has been designed and
calibrated so that the same mole ratio is held constant at every point at a cross section
through the linear flow axis of the reactor. All molecules of feed see exactly the same
quantity of SO . This is different than the macro mole ratio control which is the overall
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mole ratio of organic feedstock and SO fed to the reactor. Macro control is determined
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by the plant's control system. It is imperative that the equipment be capable of both
macro and micro mole ratio control because sulfonation is such a critical reaction with
respect to mole ratio control. A 1% variation in the mole ratio can spell the difference
between world class product and off-specification material.

Choosing a Sulfonation Process

The choice of sulfonation process depends on many factors. One of the most important is
the desired products and their required quality. Some processes are very versatile while
others produce only a few types of products. Each process produces slightly different
products. For example, the sulfamic acid process produces only ammonium sulfates from
alcohols or ethoxylated alcohols. Another example is the presence of a minimum of 8%
sulfate in sodium alkyl benzene sulfonates made with oleum. Some processes such as the
air/SO process are capable of sulfating or sulfonating a wide variety of feedstocks and
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producing excellent quality products from all of them.

A second factor to consider in the choice of sulfonation process is the required
production capacity. The sulfamic acid process is a batch process suitable for production
of small quantities of material. The air/SO process is a large scale continuous process
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best suited to 24 hours per day, seven days per week manufacture of tons per hour of
product. The chlorosulfuric acid and oleum processes can be run as either batch or
continuous processes.

Reagent cost may have a major impact on choosing a process. The air/SO process has
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the lowest cost per pound of SO reacted while the sulfamic acid process has the highest.
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For large scale commodity production, the air/SO process clearly has an advantage.
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However, for small scale production of a high value specialty product this advantage may
be outweighed by other considerations such as initial equipment cost and the necessity
for continuous operation.

Page 8 of 36 © 1997 The Chemithon Corporation