This column is based on the report “Sodium Lauryl Ether Sulfate Production – Cost Analysis,” published by Intratec. It can be found at the following URL: www.intratec.us/analysis/sles-e11a.
Sodium lauryl ether sulfate (also known as SLES and sodium laureth sulfate) is a clear and viscous liquid that is among the most important anionic surfactants. On an industrial scale, SLES is mainly produced by the ethoxylation of dodecanol, followed by the sulfation of the resulting ethoxylate and neutralization to the sodium salt.
Like other fatty alcohol sulfates and fatty alcohol ether sulfates, SLES has uses that are basically related to its surface-active properties. SLES molecules include both hydrophilic and hydrophobic functional groups. In fact, the possibility of altering those properties allows chemical processors to tailor these compounds to be used in a broad range of applications that demand good activity (that is, foaming and detergency), stability over a wide pH range, water solubility, chemical compatibility and so on. With such versatility, these chemicals are widely used in cosmetic products and in industrial cleaners.
The following describes a process for SLES production from chlorosulfonic acid, lauryl ethoxylate and sodium hydroxide. Figure 1 presents a simplified flow diagram of the process.
Sulfation. Initially, the lauryl ethoxylate is batch-sulfated by cholorosulfonic acid. Both reagents are fed to a glass-lined stirred, jacketed reactor, with the acid being gradually added to the reaction. The sulfation is carried out at 25–30°C under vacuum, over about a period of 2.5 h. The gaseous HCl byproduct is led off the sulfation product, and directed to a scrubber downstream. The sulfation product is fed to the neutralization.
Neutralization. The sulfation product is fed to a neutralization vessel, where it is contacted with a 50 wt.% caustic soda solution, along with process water, for adjusting its active component. The neutralization reaction is carried out at a temperature below 45°C, generating a 70 wt.% sodium lauryl ether sulfate, which is further routed to packaging.
Scrubbing. The HCl evolved during the sulfation is fed to a scrubber, where it is absorbed into process water, generating a 33 wt.% hydrochloric acid solution byproduct.
Packing. SLES is packed in drums and then sent to warehouses for storage outside the battery limits (OSBL) of the facility.
SLES production is primarily based on the sulfation of lauryl ethoxylate, in such a way that different SLES manufacturing routes are basically related to different sulfating agents employed. Typically, chlorosulfonic acid, sulfur trioxide or oleum (SO3 • H2SO4) reagents are used for that purpose. Figure 2 presents different pathways for SLES production.
The total operating cost (raw materials, utilities, fixed costs and depreciation costs) estimated to produce SLES was about $2,130 per ton of SLES in the second quarter of 2014. The analysis was based on a plant constructed in the U.S. with the capacity to produce 15,000 metric tons per year of SLES.
Edited by Scott Jenkins
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