A comparison of batch and continuous chromatography equipment for the separation of organic mixtures

Abstract

A review of general chromatography theory with particular reference to gel permeation chromatography (g.p.c.) has been made. Equipment for the preparative and production scale applications of chromatography are described. Large-scale g.p.c. fractionations of dextran, apoly-glucose have been investigated. Two methods of operation, by repetitive batch and semi-continuous chromatography have been evaluated. Both chromatographs consisted of ten columns of 5.1 cm id by 70 cm long, packed with Spbrosil X0B075. Glass columns were used for the repetitive batch chromatograph and stainless steel for the semi-continuous chromatograph. The maximum operating pressures for the semi-continuous and repetitive batch chromatographs were 1550 and 480 kNm-2, respectively. For equivalent operating pressures the maximum hourly feed rates for the semi-continuous and repetitive batch chromatography were 175 and 63 g h~' of dextran. Comparison of the operating methods was principally made on the basis of a hypothetically ideal product and on the concentration of dextran in the final product streams. Modification to the semi-continuous chromatograph enabled dextran fractionations to be performed at temperatures of up to 65°C. An increase in the dextran feedrate from 690 to 960 grams per cycle was possible when the operating temperature was increased to 62°C. A description of the concentration and temperature interactions for the gel permeation process in the semi-continuous chromatograph are discussed. A simple linear exclusion model attemptina to describe the Phenomena of gel permeation has been formulated and its application to describe the fractionation of dextran in the semi-continuous chromatograph has been made. Only partial agreement between the experimental results and computer simulations was achieved because the model could not describe the concentration dependent interactions of the gel permeation process.