Abstract: The present invention relates to a process for preparing polyoxymethylene dimethyl ethers, comprising the following steps: reaction of formaldehyde and methylal (OME1) in a reactor R1 to obtain a product mixture, distillative separation of the product mixture in a distillation unit D1 into a top stream which contains OME1, OME2, formaldehyde, methanol and water, and a bottom stream which contains OME?3, mixing of the top stream drawn off from the distillation unit D1 with a methanol-containing stream, treatment of the mixture in a reactive distillation unit RD2 to form a top stream containing methylal and a water-containing bottom stream, introduction of the bottom stream drawn off from the distillation unit D1 into a distillation unit D3 and distillative separation of the polyoxymethylene dimethyl ethers.

Abstract: The present invention relates to a method for producing polyoxymethylene dimethyl ether by introducing a formaldehyde source and at least one compound of the formula (I) H3C—O—R??(I) where R is H or —(CH2O)x—CH3 with x being 0 or 1 as reactants into a reactive distillation unit and reacting them to give polyoxymethylene dimethyl ether, wherein the method produces polyoxymethylene dimethyl ether exclusively in the reactive distillation unit.