(148d) A Novel Configuration for Gradient Operation in Smb System

Most Simulated Moving Bed (SMB) processes known today are operated under isocratic conditions, i.e., with a single eluent. On the other hand, preparative bio-separation is more commonly done with gradient elution chromatography. Schemes that incorporate different solvent compositions in the input streams have been proposed to simulate gradient elution operation in SMB system, but the proper operation condition for good separation was rather restricted and difficult to determine. One of the reasons for gradient operation in elusion chromatography, such as those involve salt gradient, was to accelerate the regenerate of used column. For such cases, there are two possibilities to implement a salt gradient operation in SMB system. The first is to expend the standard four-zone SMB system into a six-zone, with extra input and output streams for high salt eluent. However, this would require the use of more columns and would reduce the overall productivity. A novel scheme is here fore proposed, which takes the advantage of the dynamic nature of SMB operation by introducing salt to the eluent stream at appropriate time in the original four-zone design. We will demonstrate this configuration is both convenient and effective in maximizing the productivity and the reduction of eluent consumption, with data from literature cases.