Process for separating a ketose from an aldose by selective adsorption

A process for continuously separating, in liquid phase, fructose from a liquid feed mixture of sugars containing fructose and glucose, fructose being selectively adsorbed by contact with solid adsorbent particles of crystalline aluminosilicate or zeolite, utilizing a simulated countercurrent flow system, wherein liquid streams are allowed to flow through three serially closed loop interconnected zones including a desorption zone, a purification zone and a adsorption zone, each zone being divided into a plurality of serially interconnected beds, each bed being packed with a mass of said solid adsorbent particles, comprising the steps of introducing said liquid feed mixture into the first bed of said adsorption zone, introducing water as a desorbent into the first bed of said desorption zone, withdrawing a portion of a desorption effluent comprising the extract and the desorbent from the bed of said desorption zone for obtaining a product of fructose, withdrawing a portion of a raffinate effluent comprising less adsorbed sugars and the desorbent from a point such that a zone remains between the raffinate outlet stream and the desorbent inlet stream and immediately upstream with respect to the fluid flow to the desorption zone, and all of the points of introducing and withdrawing said liquid streams into and from said beds are simultaneously shifted one bed at a time at predetermined intervals of time, in a downstream direction in the same aliquot portion of the total cycle, and circulating said liquid streams flowing in said three zones without any interruption of flow between said desorption zone and said purification zone.