Preparation of Sorbitan Stearate

Sorbitan fatty acid esters called sorbitan esters are surfactants widely used as food in the production process as emulsifiers. Sorbitan esters are well-known emulsifiers suitable for use in food، pharmaceutical products as well as many other applications. One such technique involves direct esterification of sorbitol or an intramolecular condensate of sorbitol with fatty acids in the presence of acid or alkali catalysts in one step process. In two step process، sorbitol is first dehydrated to sorbitan and then esterified with acid or alkaline catalysis. In this study، two steps process due to better compatibility was selected. For the first and second steps، catalysts were tested fur phosphoric acid recognized as suitable catalyst for this reaction، effect of temperature and pressure and catalyst concentration were determined. The results show that dehydration rate is proportional to temperature and catalyst concentration، but pressure has negative effect. For the second step، alkaline catalyst was studied and esterification was affected under alkaline condition. Surface tension was studied by different amount of sorbitan ester. Produced sorbitan ester reduced surface tensionwith CMC 15mg/L and saponification number of 147.