Visualization of Formaldehyde Distribution Above Platinum Plate Catalyst by Using LIF Method

摘要

Visualization has been attempted to measure formaldehyde formation during catalytic combustion of methanol/air mixtures. The visualization of formaldehyde distribution above a platinum plate in methanol premixed gas flows was carried out by a LIF (laser-induced fluorescence) method. Formaldehyde (CH_2O) has fluorescence spectra in the 340.6-493.3-nm range when it is excited by the third harmonic wavelength of Nd.YAG laser (355 nm). In our study, formaldehyde was excited by a pulse laser shot and the fluorescence at wavelength of 412.2 nm was selected for investigation. By this laser technique, the time resolved instantaneous distribution of formaldehyde on the platinum plate was successfully observed. The results show that the distribution of formaldehyde fluorescence is affected by gas velocity, catalyst temperature, and especially excess air ratio. The results correspond well with the results of a mathematical modeling for formaldehyde formation over Pt, and it confirms that this method is useful for analyzing the mechanism of catalytic combustion.