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Reactive Chromatography

Based on our experience with the preparation of Raschig rings, we succeeded in making monolithic rods. We prepared samples with diameters of 5.3 and 12 mm and lengths of 110 and 200 mm. The sulfonated monoliths were tested in tetrahy-drofuran synthesis from 1,4-butandiol in which water is formed as a by-product of this cyclization etherification. The two products have different sorption behavior from the resin particles, which can be used to separate the products if the catalyst is operated as a chromatographic column [27]. As a reactor the rod was encapsulated in a fiber-reinforced epoxy resin casing allowing operation at pressures up to 100 bar. The casing was equipped with HPLC fittings: Fig. 8.20 shows a cross-section of this column.

This microreactor was heated to the desired reaction temperature and dioxan was pumped through the reactor. If a pulse of 1,4-butandiol is injected into the flowing dioxan, the diol forms tetrahydrofuran and water on the acidic polymer particles inside the channels of the rod. Water is adsorbed strongly: tetrahydrofuran leaves the reactor first, followed by water. Fig. 8.21 gives a calculated chromatogram based on sorption data.

The production of water-free tetrahydrofuran is possible using this method [28], but this is only a model reaction. No one will produce a bulk chemical like tetrahydrofuran in a microreactor. But products with higher value have similar reaction behavior, for example the esterification of end-terminated long-chain hydroxycar-bon acids. An inner ester forms by cyclization leading to macrocyclic compounds, which can be used in the flavor and fragrance industry.

RTF E-tape shrinks bte PTFE-hose diffusor

RTF E-tape shrinks bte PTFE-hose diffusor

HPLC-connector reinforced epoxy-resin

Fig. 8.20 Cross sectional drawing of a monolithic reactor

HPLC-connector reinforced epoxy-resin

Fig. 8.20 Cross sectional drawing of a monolithic reactor

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