Patent ID: 8884073

Claim:
A process of making low molecular weight polytrimethylene ether glycol comprising the steps of: (a) polycondensing an initial mixture comprising 1,3-propanediol and sulfuric acid at a temperature of at least about 150° C. to obtain a first reaction mixture; (b) adding to the first reaction mixture (i) alumina, (ii) silica based filter aid, and optionally (iii) activated carbon black at temperature greater than about 120° C. and less than about 200° C. to form a second reaction mixture; (c) distilling the second reaction mixture at a pressure of about 1 to about 40 torr and a temperature of about 120° C. to about 200° C. to obtain a third reaction mixture and a distillate containing 1,3-propanediol; and (d) filtering the third reaction mixture at a temperature of about 70° C. to about 100° C. to obtain polytrimethylene glycol of number average molecular weight from about 200 to about 500 which contains less than about 0.5 weight % 1,3-propanediol and has an acid number of less than 0.05 mg KOH/g and a turbidity of less than about 1 NTU.