processes for the removal of trioxane from a mixture of formaldehyde, trioxane and water, and for the preparation of trioxane from an aqueous formaldehyde solution, and the use of trioxane

摘要

"PROCESSES FOR REMOVING TRIOXANE FROM A FORMALDEID, TRIOXANE AND WATER MIXTURE, AND FOR PREPARING TRIOXANE FROM A WATER FORMALDEID SOLUTION, AND USING TRIOXANE". The invention relates to a method for separating trioxane from a mixture containing formaldehyde, trioxane and water. According to said method: the mixture (1) is distilled in a first distillation stage (7) at a pressure between 0.1 and 2 bar to obtain a formaldehyde containing stream (8) and a predominantly containing stream (9) trioxane, in addition to water and formaldehyde; stream (9) is mixed with a recycle stream (19) containing predominantly trioxane in addition to water and formaldehyde to form a stream (10) containing predominantly trioxane in addition to water and formaldehyde, stream (10) and then distilled in a second distillation stage (14) at a pressure between 0.2 and 10 bar, optionally after separation of low boiling products from the stream (9) or (10) into an additional distillation stage (11). ). The pressure in the second distillation stage (14) is at least 0.1 bar higher than the pressure in the first distillation stage (7). Said distillation produces a stream (15) consisting of trioxane and a stream (16) containing predominantly trioxane, in addition to water and formaldehyde. The stream (16) is then distilled in a third distillation stage (17) at a pressure between 0.1 and 4 bar to obtain a stream (18) containing predominantly water, in addition to formaldehyde and the recycle stream (19) containing predominantly trioxane, in addition to water and formaldehyde. The resulting stream (18) is optionally distilled at a fourth distillation stage (20) to obtain a predominantly water-containing stream (21) and a predominantly formaldehyde-containing stream (32).