USE OF TRIOXANE OBTAINED FROM A METHOD FOR SEPARATING OUT TRIOXANE FROM A TRIOXANE/FORMALDEHYDE/WATER MIXTURE FOR PRODUCING POLYOXYMETHYLENE DIALKYL ETHERS

摘要

The invention relates to the use of a raw trioxane stream IV having a trioxane proportion of greater than or equal to 90 wt%, obtained in a method for separating out trioxane from an input stream I of formaldehyde, trioxane, and water, where a) an input stream I comprising formaldehyde as a main component and trioxane and water as secondary components is provided, b) the input stream I, a backstream V, and a backstream VII comprising formaldehyde as a main component and trioxane and water as secondary components are fed into a first distillation stage and distilled at a pressure from 0.1 to 2.5 bar, wherein a bottom stream II comprising formaldehyde as a main component and water as a secondary component and a head stream III comprising trioxane as a main component and formaldehyde and water as secondary components and a side stream X comprising water, trioxane, and formaldehyde are obtained, c) the head stream III is distilled in a second distillation stage at a pressure from 0.1 to 17.5 bar, optionally after separating out low-boiling components from the head stream III in a low-boiling component separating stage, wherein the pressure in the second distillation stage is 0.1 to 15 bar higher than the pressure in the first distillation stage, and the pressure of a backstream V comprising trioxane as a main component and water and formaldehyde as secondary components, and the pressure of the raw trioxane stream IV as a bottom stream, d) the stream X and optionally a stream IX comprising water as a main component are fed into a third distillation stage and distilled at a pressure from 1 to 10 bar, wherein a bottom stream VI substantially composed of water and a backstream VII as a head stream comprising formaldehyde as a main component and water and trioxane as secondary components are obtained, for immediate use without further purification as a reactant stream for producing polyoxymethylene dialkyl ethers.