Production of levulose from sucrose

The production of levulose from sucrose was originally outlined to determine the optimum conditions for producing levulose using the Dubrunfout method for separating the levulose from the mother liquor by precipitating it as calcium levulate. This investigation was to include the study of the effect of invert sugar concentrations, the effect of mol ratio of Ca(OH)₂ to levulose and temperature, on the workability of the calcium levulate precipitate obtained and the yield of levulose resulting. A study to determine the possibility of using ion exchange material for the purification of the levulose solution was also planned.

In all tests, the sucrose was inverted by acidifying the syrup with sufficient H₂SO₄ to obtain a pH of 1.0-1.5 and heating to 70°C for 90 minutes. An inversion of 92-97 percent resulted.

The mol ratio of Ca(OH)₂ to levulose for precipitation was varied from 1:1 to 3:1 and it was found that the 3:1 ratio resulted in the best yield, a 59.6 percent yield being obtained. It was found that a 55-58 percent invert sugar solution resulted in an unworkable mass when the levulose was precipitated as calcium levulate, but a 28-29 percent solution could be centrifuged satisfactorily.

Using a 28-29 percent invert sugar solution and a 3:1 mol ratio of Ca(OH)₂ to levulose for precipitation, the effect of the precipitating temperature on the yield of levulose was determined. It was found that the precipitating temperature varied inversely with yield, with the best yield of 59.6 percent resulting at 0°C and no yield being obtained at 30°C.

Attempts to purify the levulose solution resulted in a nine-fold loss in capacity of the exchange material in one use and regeneration, when H₂SO₄ was used as the regenerant. When HC1 was used as regenerant for the material a recovery of some of the capacity resulted. The recovery of capacity was four times the capacity exhibited in the last where H₂SO₄ was used, but only 13 percent of its original capacity.

The assumptions made in conducting this investigation were held to a minimum, but it was necessary to make several assumptions when making analytical tests.