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Abstract

Previously, starch-derived glycol and glycerol glucosides were prepared by batch-reaction processes and had excellent potential as chemical intermediates for a wide range of products. However, more efficient processes for preparation of these derivatives are needed. In this present work, a modern corotating, intermeshing, twin-screw extruder with a barrel length/screw diameter (L/D) ratio of 43: 1 was used to study the reaction of starch with ethylene glycol and glycerol in the presence of sulfuric acid catalyst at elevated temperatures. A fully continuous process was used. Variables that were investigated included temperature (140–180°C), glycol or glycerol/starch AGU mol ratio (1.5–4.0), starch feed rate (5–30 lb/h), screw speed (100–475 rpm), residence time, specific energy, and several types of commercial cornstarch and corn flour products. Rates and extents of reaction that occurred in the barrel were determined by analyzing samples that were quenched just prior to extrusion. The major glucosides were quentitated by high-performance liquid chromatography. Results of this study show that starch can be continuously, rapidly, and efficiently converted to glucosides in 90% yield at high production rates. Such processing is expected to be technically feasible for the reaction of a wide range of polyhydroxy alcohols with various starch substrates.