Influencing Factors of Formaldehyde Emissions During Methanol Oxidation

The influencing factors of formaldehyde emission during methanol oxidation were investigated in a flow reactor in the temperature environment of engine exhaust gas. Unregulated emissions were detected by a gas chromatography(GC)with a pulsed discharge helium ionization detector(PDHID). Experimental results show that methanol incipient oxidation temperature was about 723,K under the test condition. Methanol oxidation is mainly affected by temperature,and reaction time is the secondary factor when temperature is higher than 933,K. Formaldehyde increases first and then decreases with the increase of temperature,the formation and oxidation of formaldehyde are mainly affected by temperature. The critical temperature range for formaldehyde generation and oxidation is 848—882,K under the test condition. Formaldehyde concentration reaches its maximum at the critical temperature. Below the critical temperature,formaldehyde decreases with the increase of flow velocity. Above the critical temperature, prolonging the reaction time of formaldehyde is conducive to the decrease of formaldehyde. Methanol oxidation and formaldehyde generation are inhibited under the anaerobic conditions. Formaldehyde increases with the increase of excess air ratio. Methanol and formaldehyde emissions from M 10 engine decreases obviously when insulating exhaust pipe under medium and high load conditions.