The fasil process (named from "

formaldehyde Formaldehyde ( , ) (systematic name methanal) is an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...

silver") is an industrial method for producing formaldehyde from

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

, utilizing a silver catalyst. It is one of the two primary large-scale formaldehyde production methods, alongside the metal oxide process. The name fasil is a registered trademark owned by Dynea AS. Dynea started to produce formaldehyde in Norway in 1947 and has developed the process since then. More than 40 fasil formaldehyde plants have been installed worldwide.

Process description

Methanol, air and water is the primary feedstock for formaldehyde production. The feedstock is mixed in a vaporizer, and passed over a silver catalyst bed in an adiabatic reactor. Due to the methanol/oxygen ratio, the reaction gas mixture is above the upper flammability limit (UFL) for methanol/air mixtures and therefore inherently safe. The formaldehyde produced is separated from unreacted methanol and byproducts through absorption in water, using a selective absorber. In the fasil process, formaldehyde is synthesized through the

catalytic oxidation Catalytic oxidation are processes that rely on catalysts to introduce oxygen into organic and inorganic compounds. Many applications, including the focus of this article, involve oxidation by oxygen. Such processes are conducted on a large scale ...

of methanol. The primary reactions are partial oxidation of methanol (1), and methanol dehydrogenation (2). :(1) :(2) This exothermic chemical reaction is facilitated by the silver catalyst at high temperatures, typically around 600-650 °C. The excess energy from the exothermic reaction is used to generate steam by burning the

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

-rich tail gas in a boiler or thermal oxidizer. The reactor used in this process is a fixed-bed heterogeneous catalytic reactor, where the process gas is quickly cooled down in a waste heat boiler to reduce byproducts from gas phase reactions.{{cite journal , last1=Lervold , first1=Stine , last2=Lødeng , first2=Rune , last3=Yang , first3=Jia , last4=Skjelstad , first4=Johan , last5=Bingen , first5=Kristin , last6=Venvik , first6=Hilde J. , title=Partial oxidation of methanol to formaldehyde in an annular reactor , journal=Chemical Engineering Journal , date=1 November 2021 , volume=423 , pages=130141 , doi=10.1016/j.cej.2021.130141, bibcode=2021ChEnJ.42330141L , hdl=11250/2981955 , hdl-access=free The silver catalyst in the reactor is periodically replaced, a process that can be completed within a day. The used silver is regenerated through an electrolytic process and is fully recycled. The process gas cooling relies solely on water and steam, reducing fire risks. Additionally, all oxygen is converted in the reactor. Oxygen is therefore not present in the absorber, improving safety and the quality of the formaldehyde produced.

References

Chemical processes Catalysis Formaldehyde