Synthesis of high quality sorbitan monostearate
Sorbitan monostearate (Span 60) is synthesized from sorbitol and stearic acid by two-step method (etherification followed by esterification), and the influences of main factors on the product color and three quality indexes (acid value, hydroxyl value and sa-ponification value) are investigated. It is found that the kind of catalyst of etherification is an important factor to gain qualified product with a light color, the saponification value of the products decrease with decreasing of the molar ratio of stearic acid to sorbitol,and the hydroxyl value of products reduces as the improvement of the dehydration in etherification. The suitable reaction conditions are obtained, i. e. , for etherification, reaction temperature is 165℃, reaction time is 70 min and w(H3PO4+KH2PO1 )=0. 60% ; for esterification, reaction temperature is 195-200℃,w(Na2CO3) = 0. 70% -0. 80%, and reaction time is 180 min. Analytical results show that the three quality indexes of all samples from laboratory and pilot plant tests are eligible, the color of product is ivory and the mass fractions of monoester and diester are higher than that of the domestic similar products.