Bayer Aktiengesellschaft

Stephan Kabelac

Hans-Josef Buysch

Paul Wagner

Johann Rechner

Klaus Nachtkamp

Norbert Schon

Christian Rasp

Oswald Wilmes

Georg Ronge

Heinrich Steude

Jurgen Dahmer

Dieter Schleenstein

Wilfried Litz

This present invention relates to a process for thermally cracking carbamic acid esters into the corresponding isocyanate and hydroxyl compounds in the liquid phase, wherein the reaction proceeds as a reactive rectification in the stripping zone of a column and in an inert, high-boiling solvent, which acts as a buffer to keep the reaction away from the evaporator region of the column.

Process for thermally cracking carbamic acid esters

Organic carbonates which contain at least one aromatic ester group can be obtained continuously from carbonates, which contain at least one aliphatic ester group, and a phenolic compound in the presence of a transesterification catalyst known per se in that the reaction is carried out in a bubble column reactor or in a cascade of at least two bubble column reactors in such a way that the phenolic compound is metered into the first bubble column and the carbonate containing at least one aliphatic ester group is metered into each individual bubble column, but preferably only into the last bubble column. The carbonate containing at least one aromatic ester group is taken off in the liquid state from the last bubble column. Volatile reaction products, for example eliminated alcohol or a dialkyl carbonate are taken off at the upper end of each individual bubble column, preferably at the upper end of the first bubble column.

Process for the continuous preparation of aryl carbonates

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Langenfeld, Germany

Stephan Kabelac