Reactive Stripping

In a reactive stripping process one disadvantage of RD can be avoided. If in an RD process the pressure is chosen, the temperature is a result of this pressure. Pressure and temperature are always coupled because all of the reactants are heated until evaporation occurs, which means that the reaction temperature is determined by the pressure or vice versa. This coupling of temperature and pressure does not happen in a reactive stripping process. In such a process the reactants are feed as a liquid to the top of a column and trickle over the catalyst bed downwards. During the flow to the bottom of the column chemical reaction and separation occur. This process is useful for fine chemical production, in which the reactants may not be heated to their boiling points as is very often the case in organic synthesis [26]. Polymer/carrier Raschig rings were tested successfully for the esterification of fatty acids with long chain alcohols. The operating temperature was up to 120 °C. The Raschig rings changed in color into deep dark brown, but ion-exchange capacity measurements revealed that the capacity did not change during operation for several weeks. This observation might be explained by the fact that desulfonation occurs fast if water is present, but in the stripping process of esterification the by product water was removed by the stripping gas hydrogen. The product ester leaves the column at the bottom; water and hydrogen leave the column at the top. The use of hydrogen as stripping gas might be a rare choice, but there are two reasons: one is the high diffusion coefficient of water vapor in hydrogen and the other is that the hydrogen can be used for hydrogenation of double bonds in a bifunctional catalyst.

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