Abstract:
The invention describes a method for separating trioxane from a supply flow I of formaldehyde, trioxane, and water, wherein a) a supply flow I containing formaldehyde as the main component and trioxane and water as the secondary components, is provided, b) the supply flow, a return flow V, and a return flow VII containing formaldehyde as the main component and water and trioxane as the secondary components, are fed into a first distillation step and are distilled at a pressure of 0.1 to 2.5 bars, wherein a flow II containing formaldehyde as the main component and water as the secondary component, and a flow III containing trioxane as the main component and water and formaldehyde as the secondary components, and a flow X containing water, trioxane and formaldehyde, are obtained, c) the flow III, optionally after separating low boilers from the flow III in a low boiler separating step, is distilled in a second distillation step at a pressure of 0.2 to 17.5 bars, wherein the pressure in the second distillation step is higher than the pressure in the first distillation step by 0.1 to 15 bars, wherein a flow IV, substantially consisting of trioxane, and the return flow V containing trioxane as the main component and water and formaldehyde as the secondary components, are obtained, d) the flow IV is purified in at least one further trioxane distillation step at a head pressure of 0.5 to 2 bars, wherein purified trioxane is obtained as the lateral removal flow is obtained in the reinforcement part of the column, d) the flow X, and optionally a flow IX containing water as the main component, are fed into a third distillation step and distilled at a pressure of 1 to 10 bars, wherein a flow VI substantially consisting of water, and a return flow VII containing formaldehyde as the main component and water and trioxane as the secondary component, are obtained.
Abstract:
The present invention relates to a method for producing low-halogen polybiphenylsulfone polymers, the polybiphenylsulfone polymers that can be obtained in this way, polybiphenylsulfone polymers having a content of polymer-bound halogen of less than 400 ppm, thermoplastic molding compounds containing said polybiphenylsulfone polymers, and the use thereof for producing molded bodies, fibers, films, membranes, or foams.
Abstract:
Disclosed is a method for producing polyoxymethylene homopolymers or copolymers (7) by homopolymerizing or copolymerizing trioxane, starting from methanol (1) that is oxidized in a first reactor of a first production system (A) such that an aqueous formaldehyde-containing stream (2) is obtained that is fed to a second production system (B) in which pure trioxane (6) is obtained. In said method, low-boiling fractions (5) are separated by distillation, and the pure trioxane (6) is fed to a third production system (C) in which the pure trioxane (6) is homopolymerized or copolymerized to obtain polyoxymethylene homopolymers or copolymers (7). The disclosed method is characterized in that the stream of low-boiling fractions (5) is recycled from the column (K 2) separating low-boiling fractions into the inlet of the first reactor in the first production system (A).
Abstract:
The invention describes a method for separating trioxane from a supply flow I of formaldehyde, trioxane, and water, wherein a) a supply flow I containing formaldehyde as the main component and trioxane and water as the secondary components, is provided, b) the supply flow, a return flow V, and a return flow VII containing formaldehyde as the main component and water and trioxane as the secondary components, are fed into a first distillation step and are distilled at a pressure of 0.1 to 2.5 bars, wherein a flow II containing formaldehyde as the main component and water as the secondary component, and a flow III containing trioxane as the main component and water and formaldehyde as the secondary components, and a flow X containing water, trioxane and formaldehyde, are obtained, c) the flow III, optionally after separating low boilers from the flow III in a low boiler separating step, is distilled in a second distillation step at a pressure of 0.2 to 17.5 bars, wherein the pressure in the second distillation step is higher than the pressure in the first distillation step by 0.1 to 15 bars, wherein a flow IV, substantially consisting of trioxane, and the return flow V containing trioxane as the main component and water and formaldehyde as the secondary components, are obtained, d) the flow IV is purified in at least one further trioxane distillation step at a head pressure of 0.5 to 2 bars, wherein purified trioxane is obtained as the lateral removal flow is obtained in the reinforcement part of the column, d) the flow X, and optionally a flow IX containing water as the main component, are fed into a third distillation step and distilled at a pressure of 1 to 10 bars, wherein a flow VI substantially consisting of water, and a return flow VII containing formaldehyde as the main component and water and trioxane as the secondary component, are obtained.
Abstract:
Disclosed is a method for producing crude trioxane (1) at a concentration ranging from 50 to 70 percent by weight of trioxane by trimerizing formaldehyde from an aqueous formaldehyde solution (2) in the presence of an acid catalyst (3) and concentrating, by distillation, the trioxane of the reaction mixture from the trimerization process. Said method is characterized in that the trimerization process of the formaldehyde and the concentration of the trioxane of the reaction mixture from the trimerization process are carried out in a single column (K) which is separated into a bottom column zone (A) and a top column zone (B) by means of a horizontal baffle plate (T), the bottom column zone (A) and the top column zone (B) being connected using an external steam pipe and an external liquid pipe. Furthermore, a reactive distillation process in which the formaldehyde is trimerized to obtain trioxane and the trioxane in the reaction mixture is concentrated to the solubility limit of the formaldehyde is carried out in the bottom column zone (A) at a pressure ranging from 1 to 5 bar. Additionally, a distillation process in which the trioxane is concentrated to crude trioxane having a concentration ranging from 50 to 75 percent by weight is carried out in the top column zone (B) at a pressure ranging from 200 to 900 mbar.