The gas‐phase reaction of O3 with H2CO

Abstract

AbstractExplosions occur when O3 and H2CO are mixed in a fresh vessel, even in the presence of several hundred torr of N2 or O2. However, in an aged vessel the reaction is well behaved. The reaction between O3 and H2CO was studied at room temperature in an aged vessel in the presence of about 400 torr of either N2 or O2. The initial rate of O3 decay in the presence of N2 is about 103 times faster than in the presence of O2, and very small amounts of O2 quickly reduce the initial rate of O3 decay in the N2 case. A chain mechanism is postulated to account for the results in which chain initiation can occur both by thermal decomposition of O3, followed by reaction of O(3P) with H2CO to produce HO and HCO, as well as by equation image which may occur both homogeneously and heterogeneously. The rate coefficient k1 ≃ 2.1 × 10−24 cm3/molec · sec represents an upper limit (to within a factor of 2 uncertainty) to the direct gas‐phase reaction between O3 and H2CO.