Formaldehyde flammability limits

Fire Hazards - Flash Point (deg. F) 203 OC Flammable limits in Air (%) 3 - 6.3 Fire Extinguishing Agents Water, foam, dry chemical, or carbon dioxide Fire Extinguishing Agems Not to be Used Not pertinent Special Hazards of Combustion Products Sulfur dioxide, formaldehyde, and methyl mercaptan may form Behavior in Fire Not pertinent Ignition Temperature (deg. F) 572 Electrical Hazard Not pertinent Burning Rate 2.0 mm/min. 

The synthesis of formaldehyde from selective oxidation of methanol over a thin layer of electrolytic silver catalyst is a well-known industrial process that occurs in the temperature range of 850-923 K at atmospheric pressure. Since the total reaction is highly exothermic and fast, requiring very short contact time (0.01 s or less), the use of a silicon MSR was demonstrated to improve conversion up to 75% and 90% selectivity at safe conditions within the flammability limits [29]. 

As an aside, we might ask why both of the commercial formaldehyde processes operate with feeds where the ratio of air to methanol is far removed from the stoichiometric ratio. The answer is safety, specifically the need to avoid the possibility of an explosion. In both processes, the feed compositions are outside the flammability limits of methanol/air mixtures, so that an explosion is not possible, even if an ignition source is present. In the silver catalyst process, the methanol/air ratio is above the upper flammability limit. In the iron molybdate process, the methanol/air ratio is below the lower flammability limit. 

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