Appeal 2007-0711
Reexamination 90/006,706
the difference in retention time between two components, this requires
a large k’ which has the ancillary undesirable effect of increasing the
retention volume of the mobile phase for the components. Thus the
accepted practice in analytic chromatography and in batch mode
preparative chromatography of operating at a high k’, usually in the
range of 1<k’<10, has as a necessary consequence the usage of a large
volume of mobile phase.
Priegnitz purportedly found that (Priegnitz, col. 2, ll. 47-65):
. . . the separation of enantiomers from their racemic mixture using a
chiral stationary phase in simulated moving bed chromatography can
be performed effectively at low values of k’, thereby minimizing the
amount of mobile phase which is needed. Specifically, chiral
separations may be performed efficiently where k’ is less than 1, and
especially in the range 0.1<k’<1. Since an appreciable cost of the
separation process is associated with the mobile phase and its
recovery from the raffinate and extract streams, our process affords
substantial cost savings accruing from a lower mobile phase
inventory, lower utility costs in recovering the mobile phase, and
other ancillary costs.
It needs to be mentioned that even though certain types of
separation currently effected by simulated moving bed (SMB)
processes operate at the equivalent of a low k’ it is not obvious to
extend this knowledge to chiral separations because the mechanism of
adsorption is fundamentally different. Thus, the adsorbents used in
traditional separations such as that of the xylene isomers are zeolites
. . . that have a high ion exchange capacity.
Persons having ordinary skill in the art would have understood from
Priegnitz that the presently claimed processes are particularly and
exclusively directed to improved processes “for the separation of at least one
enantiomer from a mixture of chiral organic materials by simulated moving
bed chromatography” (Br. App., Claim 1). The Specification instructs that
prior art information relating to SMBC processes for separating one isomer
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