Formaldehyde

The main industrial route for producing formaldehyde is the catalyzed air oxidation of methanol.

A silver-gauze catalyst is still used in some older processes that operate at a relatively higher temperature (about 500°C). New processes use an iron-molybdenum oxide catalyst. Chromium or cobalt oxides are sometimes used to dope the catalyst. The oxidation reaction is exothermic and occurs at approximately 400–425°C and atmospheric pressure.

Excess air is used to keep the methanol air ratio below the explosion limits. Figure 1.1 shows the Haldor Topsoe iron-molybdenum oxide catalyzed process.

Figure 1.1. The Haldor Topsoe and Nippon Kasei process for producing formaldehyde: (1) blower, (2) heat exchanger, (3) reactor, (4) steam boiler, (5) absorber, (6,7) coolers, (8) incinerator, (9) heat recovery, (10) methanol evaporator, (11) boiler feed water.