摘要:
A process for the gas-phase trimerization of formaldehyde to give trioxane using solid phosphoric acid catalysts. Particularly suitable catalysts for this process are SPA catalysts (solid phosphorous acid), for example “silicon phosphates”. The main advantage of this catalyst system is its simple and inexpensive production and ready availability and also, in particular, its improved long-term stability compared to the few previously described catalysts which are mostly based on supported heteropolyacids.
摘要:
A process for preparing trioxane by converting methanol to formaldehyde by dehydrogenation at a temperature of 300 to 1000° C., in the presence of a catalyst, wherein the catalyst is generated physically separately from the reactor and at a temperature above the dehydrogenation temperature, and trimerizing the formaldehyde prepared in this way to give trioxane. Also described is a process for preparing polyoxymethylene and polyoxymethylene copolymers from the formaldehyde.
摘要:
Process for the removal of trioxane from a liquid mixture comprising trioxane, formaldehyde, alcohol, hemiformals formed from the form-aldehyde and the alcohol, usual secondary components arising in the preparation of trioxane, and, in addition or as an alternative to the alcohol and the hemiformals, water, in which the trioxane is transferred into the gas phase by vaporization or evaporation and subsequently converted into a liquid state by condensation and obtained as condensate or converted into a solid state by desublimation and obtained as desublimate. Through the process, an increase in the concentration of the trioxane by 2.5 times or more is achieved.
摘要:
Processes for making trioxane, polyoxymethylene and polyoxymethylene copolymers from formaldehyde, made by the dehydrogenation of methanol in the presence of a catalytic active species set free from a sodium compound, at a temperature in the range of 300° C. to 1000° C., wherein a carrier gas stream which has a temperature above the dehydrogenation temperature is fed to the reactor.
摘要:
In a process for separating liquid mixtures comprising formaldehyde, trioxane, alcohol, hemiformal formed from the formaldehyde and the alcohol, usual minor components and up to 5% by weight of water, the liquid mixture is distilled batchwise or continuously at reduced pressure, atmospheric pressure or superatmospheric pressure in suitable apparatuses which are to be connected to one another in an appropriate manner, and the trioxane is produced in very high purity. The other materials of value, formaldehyde and alcohol, present in the mixture can likewise optionally be separated off and recycled or used otherwise, while the minor components are ejected.