Publication Details
Abstract
Formaldehyde is an industrial chemical of outstanding importance and is widely used in the manufacture of amino resins and other chemical derivatives. Industrial formaldehyde production is based primarily on the catalytic conversion of methanol in the gas phase, where two reactions occur simultaneously: the strongly exothermic oxidation of methanol to formaldehyde and the endothermic dehydrogenation of methanol, together constituting an autothermal reaction system. In industrial operation, formaldehyde synthesis via the excess air route is performed in multitubular catalytic reactors packed with iron–molybdenum-based metal oxide catalysts. Operation under these conditions allows high methanol conversion to be obtained at near-atmospheric pressure. Because the oxidation reaction is strongly exothermic, effective removal of the released heat is required in order to maintain stable reactor operation.
Heat is removed by circulating a heat-transfer medium on the shell side of the reactor, with molten salt systems and organic heat-transfer fluids, such as Dowtherm-based media, being commonly employed to control temperature profiles and suppress hot-spot formation.
After catalytic conversion, the formaldehyde-containing process gas is rapidly cooled and directed to absorption units, where formaldehyde is absorbed in water or urea solution to produce aqueous formaldehyde or urea–formaldehyde concentrate. Careful control of absorption conditions and reactant ratios is required to ensure product stability, solubility, and suitability for downstream fertilizer applications. The need for integrated and industrially calibrated reactor models for reliable comparison of cooling strategies is highlighted.