| 摘要 |
<p>1. A process for the isolation of trioxane by treatment of a dilute aqueous formaldehyde-containing solution with an extracting agent, which comprises the solution which is obtained being subjected (1) after completion of the reaction of the formaldehyde to give trioxane, or (2) during this reaction, to the following process steps : (a) treatment and, by this means, extraction of the aqueous trioxane solution with an extracting agent in amounts of 1-10 kg/kg of trioxane solution, where the extracting agent (a1 ) is during the treatment in the supercritical state in a temperature range between the critical temperature and 200 degrees C and in a pressure range between the critical pressure and 1000 bar, and thus forms a supercritical solution, or (a2 ) is during the treatment in the subcritical state in the form of a liquid gas in the temperature range between the critical temperature and 0 degree C and in the pressure range between 5 and 500 bar above the vapor pressure of the liquid gas, and forms a subcritical solution, and the solutions (a1 ) and (a2 ) contain trioxane and extracting agent together with water and formaldehyde which have been carried over, (b) separation from the extracting agent of the substances which are dissolved in the extracting agent in one or more stages by (b1 ) reducing the pressure and/or the temperature (b2 ) raising the temperature in such a manner that the pressure and temperature are always still above the relevant critical values, or (b3 ) lowering the temperature and/or the pressure into the subcritical range, where the solutions are separated into the extracting agent and into a mixture of concentrated tioxane, formaldehyde and water, which are drawn off separately from the separator during the separation step.</p> |
