The production and separation of levulose from sorghum syrup with the application of ion exchange methods

A study of the production of levulose from sorghum syrup with the application of ion exchange was made to determine the optimum conditions for the production of a levulose-rich syrup by means of the Dubrunfaut method and to determine the applicability of ion exchange methods to the purification of a levulose solution obtained through the carbonation of a suspension of calcium levulate.

A sorghum juice that had an analysis comparable to that of a typical defecated Louisiana sugar cane juice was prepare from a commercial sorghum syrup by the addition of four liters of distilled water to 750 grams of the syrup.

In all tests, the sucrose present in the prepared juice was inverted by acidifying the juice with sufficient 38.7-per-cent hydrochloric acid to obtain a pH of 1.0 to 1.2 and heating to 90°C for one hour; an inversion of 95 to 99 percent of theoretical resulted.

A molar ratio of calcium hydroxide to levulose 3:1, based on the theoretical yield, was used to precipitate the levulose as calcium levulate. The calcium levulate was suspended in two liters of distilled water and carbonated to free the levulose and precipitate the calcium as calcium carbonate.

The carbonation consisted of bubbling carbon dioxide through the calcium levulate suspension at a rate of approximately 0.5 cubic foot per hour for 48 hours. It was found that the addition of ten milliliters of 38.7-percent hydrochloric acid to the suspension of calcium levulate effected a two-fold increase in the yield.

Purification of the levulose solution was accomplished by means of an experimental ion-exchange apparatus. Passage of the levulose solution through columns containing 300 grams of zeo-karb H and de-acidite, resulted in a levulose solution of 98 to 99 percent purity.

It was determined that the capacity of the cation-exchange material, zeo-karb H, could be maintained for three cycles of treatment with 0.3013 to 0.3521 N sodium hydroxide for 24 hours at 20° to 25° and regeneration with 0.2197 and 0.3925 N hydrochloric acid for 24 hours at temperatures ranging from 20° to 25°C.

The maximum capacity of zeo-karb H for sodium ions was found to be 0.088 gram per gram of adsorbent when treated with 0.3013 N sodium hydroxide for 12 hours at temperatures ranging from 20° to 25°C/

The maximum capacity of de-acidite for chlorine ions was found to be 0.113 gram pepr gram of adsorbent when treated with 0.3437 N hydrochloric acid for 12 hours at temperatures ranging from 20° to 25°C.