A Shock Tube Study on the Pyrolysis of Acetylene in the Presence of Nitrogen Oxide

The pyrolysis of acetylene in the presence of nitrogen oxide has been investigated by use of a single-pulse shock tube in the temperature range 1100–1650 K. The hydrocarbons produced in the presence of nitrogen oxide were quite the same as those obtained from the pyrolysis of acetylene by itself. The yield-temperature plots of 1-buten-3-yne showed that at temperatures below 1350 K the formation rate of 1-buten-3-yne is reduced by the addition of nitrogen oxide. The retarding effect of nitrogen oxide on the 1-buten-3-yne formation was interpreted in terms of the reactions of nitrogen oxide with 1-ethynylvinyl and 2-ethynylvinyl radicals to yield pro-pynenitrile and hydrogen cyanide, respectively. An illustrative radical chain mechanism was presented for the pyrolysis of acetylene in line with the experimental results obtained from the pyrolysis inhibited by nitrogen oxide. The radical chain is initiated by the bimolecular reaction of acetylene, viz. 2C2H2→C4H3+H, ethynyl and 2-ethynylvinyl radicals being the chain carriers, where C4H3 is 1-ethynylvinyl radical.