Production of major reaction products in the initial steps of the thermal decomposition of naphthalene. Experimental shock-tube results and computer simulation

Initial steps in the thermal decomposition of naphthalene were studied behind reflected shocks in a pressurized driver single pulse shock tube over the temperature range 1350-1650 K and densities of ∼3 × 10^-5 mol/cm³. The present manuscript concentrates on the initial steps in the decomposition of naphthalene, rather than its function in producing molecules having more rings toward the formation of PAH etc. For the purpose of studying the low extent of decomposition, relatively low temperatures were used where the extent of reaction is small so as to prevent a secondary or higher generation of reactions that might obscure the initial decomposition process to take place. Five major decomposition products that were found in the post shock mixtures of naphthalene were acetylene, di-acetylene, benzene, phenyl acetylene, and acenaphthylene. Products that did not exceed 1% at their highest concentration were not considered both in the product distribution map as well as in the computer simulation. These were methane, ethylene, allene + propyne, methyl naphthalene, and indene. Indene, with somewhat higher than 1% at its maximum, could not be computer simulated with reasonable agreement. The total disappearance rate of naphthalene, in terms of a first-order rate constant is given by k_total = 7.33 × 10¹³exp (-364/RT) s^-1 where R is expressed in units of kJ/(K mol). A concise kinetics scheme containing 15 species and 19 elementary reactions accounts for the observed major decomposition products with reasonable agreement. The kinetics scheme, as well as results of the computer simulation and the sensitivity analysis are shown.