Supercritical process for linear alkylbenzene sulfonate production

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This project deals with a new process for making a key ingredient of commercial, biodegradable detergents. Our investigations of the oxidation of sulfur dioxide over activated carbon during the past decade has led to the discovery that supercitical carbon dioxide is able to extract strongly adsorbed sulfur trioxide from the surface of activated carbon. This makes possible a simple, room temperature process for the production of sulfur trioxide, a key sulfonation/sulfation reagent of high value to industry. Activated carbon is an extremely active catalyst for sulfur dioxide oxidation. Thus, sulfur dioxide and oxygen (or air) pass through a bed of activated carbon forming sulfur trioxide, which is strongly adsorbed on the carbon. In a second step, sulfur trioxide is stripped from the carbon by supercritical carbon dioxide to give a condensed phase containing sulfur trioxide. We have demonstrated experimentally that contacting either the dense phase or a gas phase (produced by depressurization) with commercial linear alkylbenzene in a bubble column at under 40 C consumes all the sulfur trioxide to quantitatively produce linear alkylbenzene sulfonate, an important ingredient of commercial detergents. Our preliminary experiments indicate no side reactions so that we have a new, low temperature, environmentally benign process for detergent manufacture.