SHORT NOTE Solid Supported Evaporation

096/2012
R-210/215, R-220 SE, R-250
Solid Supported Evaporation
SHORT NOTE
Recently, new insight about batchwise and semi-continuous solid supported evaporation (SSE) was reported [1, 2]. Solutions of
pharmaceutical active products and intermediates were dried and the solute trapped inside porous polymer beads. Here, we
highlight the novel technology and the beneficial use of laboratory and industrial Rotavapor instruments for SSE processes.
Introduction
Solid Supported Evaporation (SSE) is a novel, facile
method to isolate and store chemical products. In SSE the
solute is absorbed inside a porous material – usually
polypropylene (PP) beads. Therefore, the solvent is
evaporated to dryness employing a Rotavapor and
applying vacuum and heat.
intensification, e.g how to avoid inter-clogging of beads [1,
2]. As a rule of thumb, clogging is avoided as long as the
solute is soluble in the quantity of solvent swamped inside
the pores of the beads. In batchwise SSE processes,
crystallization on the outer shell of the beads, a reason for
clogging, is minimized by a slow evaporation process [1].
While the evaporated solvent is collected in the receiving
vessel, the dry solute, e.g. a pharmaceutical intermediate,
is trapped inside the beads that remain in the evaporation
vessel (Figure 1).
Compared to conventional evaporation to dryness, the
trapped compound is protected from overheating by the
beads. Hence, the beads act as a heat sink [2]. Applying
optimized SSE conditions yields a high bead loading and
freely flowing beads [1]. Important: sticking of dry
compound to the vessel walls or dusts of fine powder is
avoided by SSE.
The loaded beads are easy to handle, transport, and store.
When needed, the compound is released from the beads
by dissolution [1, 2]. In case of a solvent swap the trapped
compound is dissolved in a different solvent than the
starting solvent (Fig. 1). In theory, the solvents as well as
the beads could be recycled.
Figure 2. Schematic of the semi-continuous SSE process according to
Bäbler et al [2].
The principle of the batchwise SSE was extended to a
greater scale (kilo scale) by a semi-continuous process
(Fig. 2). This process arrangement allows collecting
reaction products and intermediates by SSE resulting from
continuously operating mini- and pilot-plants without
process interruption [2].
In semi-continuous SSE the solution is continuously
pumped to the evaporation vessel filled with polymer
beads. Feeding and SSE are continued as long as the
beads are able to absorb solute. In contrast to the
batchwise process, in semi-continuous SSE, a high solvent
evaporation rate is advantageous in order to avoid sticking
of the particles to the evaporation flask.
Conclusion
Evaporation to dryness by SSE is an attractive method
avoiding thermal degradation of thermo-labile solutes and
to obtain a freely flowing product. SSE could be an
alternative choice to crystallization for product isolation on
lab scale and pilot scale.
We think that drying by SSE is an attractive concept to be
considered in the constant improvement of early production
processes in the pharmaceutical industry and the fine
chemicals industry.
References
[1] M.L. Kebede et al, I&EC Reserach, 51, 41, 13445-13453,
Figure 1. Batchwise solid supported evaporation (SSE) and work-up.
Batchwise and semi-continuous SSE
2012.
[2] M.U. Bäbler et al, I&EC Reserach, 51, 45, 14814-14823,
2012.
In SSE it is aimed to absorb as much solute as possible on
freely flowing polymer beads. Recently, Bäbler et al
reported simple rules for the process optimisation and
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