In a process to make dithiodiglycol by oxidation of -mercaptoethanol with
sulfur, an improved product is recovered when a 1-10 mol % excess of -mercaptoethanol
is used and hydrogen sulfide is removed by vacuum or nitrogen sparge. A typical
product contains 88.1 mol % (92.0 wt %) dithiodiglycol, 2.3 mol % (2.9 wt %) trithiodiglycol
and 9.6 mol % (5.1 wt %) unreacted -mercaptoethanol. Reaction of this product
with 35 to 50 wt % solution hydrogen peroxide reduces residual -mercaptoethanol
to less than 0.02 wt % mercaptan. Residual water of about 3.6 wt % after hydrogen
peroxide treatment is reduced to less than 1 wt % by vacuum stripping and/or nitrogen
sparge or with a wiped film evaporator.
