Formaldehyde

Formaldehyde is one of the most important raw materials for industrial chemistry and is used predominantly for the manufacture of glues and resins. Formaldehyde is usually traded in the form of an aqueous solution with a concentration of about 37 %. Formaldehyde is produced predominantly by catalytic conversion of gaseous Methanol, either at a Silver Catalyst, or a Metal Oxide Catalyst. Meissner offers both processes as well as a series of process variants. The choice of the most suitable process is based in each case on customer specific requirements, such as product qualities to be met, or prevailing infrastructural conditions. With the classic Meissner variant of the Silver Catalyst process, pure Methanol is fed to the catalyst. The generated Formaldehyde together with the unconverted Methanol is washed out of the gaseous phase in an absorption unit by means of water. The obtained raw solution has to be subjected to a distillation step in order to adjust the Methanol content to the desired value, and the separated Methanol is returned into the process. Formaldehyde solutions of about 50-55 % concentration with less than 1 % of remaining Methanol can be produced with this process. In another Meissner process variant, Methanol together with water is fed to the Silver Catalyst. The admixture of water enables an enhanced conversion of Methanol. The Formaldehyde solution of about 40-44 % concentration obtained in the absorption unit therefore contains only 3-5 % of remaining Methanol without any distillation step. This has a positive effect on capital investment as well as on operating costs. For the Meissner Metal Oxide Catalyst process, a Methanol lean mixture is fed to the catalyst. As this allows an almost complete conversion of the Methanol, Formaldehyde solutions of about 50-55 % concentration with a content of less than 1 % of remaining Methanol can be produced without any distillation. Besides of very favourable consumption figures for Methanol, this process offers the further advantage that the heat of reaction is utilized for generation of steam, which is available for external consumers. A process variant works with recycling of the tail gas, which allows a capacity increase for the same dimension of the main plant components.