A Semi-Continuous Chromatographic Process for the Separation of Carbohydrates

Abstract

A review is given of general chromatographic theory, the factors affecting the performance of chromatographic columns and aspects of scale-up of the chromatographic process. The chemi-adsorption separation mechanism employed in this research study for the separation of glucose and fructose is outlined. A review of various industrial processes for manufacturing high fructose syrups is also included so as to serve as a basis for comparison. The design and construction of a sequential continuous chromatographic separation unit (SCCR4), for liquid-solid chromatography applications, is described. Counter-current operation was simulated by sequencing a system of inlet and outlet port functions around ten, 2.54 cm internal diameter x 70 cm long, glass columns. Operation of the unit for continuous separation of glucose and fructose by chemi-adsorption chromatography is reported, using 150 - 300um diameter calcium charged ion exchange resin (Zerolit SRC14) as packing, and distilled water as the mobile phase. The effects of feed and purge flowrates, mobile phase temperatures and feed concentration have been investigated. A feed of 50% w/v of glucose and fructose solution has been successfully separated, at a rate of 3 cm min-71, into a glucose-rich and a fructose-rich product of purity 86.4% w/w and 88.7% w/w respectively. ‘This throughput, on an equal cross-sectional area basis, is approximately 21/2 times that achieved by an equivalent batch process operated by the Boehringer Mannheim Company. A temperature dependence of the equilibrium distribution coefficient (Kp) of fructose, established from small-scale batch column work, provides an explanation for the higher contamination of the glucose-rich product observed in SCCR4 runs conducted at elevated mobile phase temperatures. A theoretical treatment, based on an equilibrium stage concept, of the counter-current liquid-solid chromatographic process has been attempted. A batch column study was conducted to acquire the necessary equilibrium data and plate heights for the computer simulation work. Results achieved from the theoretical study indicated partial agreement with the experimental findings.