A flow reactor study of neopentane oxidation at 8 atmospheres: Experimentsand modeling

An existing detailed chemical kinetic reaction mechanism for neopentane oxi dation [1] is applied to new experimental measurements taken in a flow reac tor [2] operating at a pressure of 8 atm. The reactor temperature ranged fr om 620 K to 810 K and flow rates of the reactant gases neopentane, oxygen, and nitrogen were 0.285, 7.6, and 137.1 standard liter per minute (SLM), re spectively, producing an equivalence ratio of 0.3. Initial simulations iden tified some deficiencies in the existing model and the paper presents modif ications which included upgrading the thermodynamic parameters of alkyl rad ical and alkylperoxy radical species, adding an alternative isomerization r eaction of hydroperoxy-neopentyl-peroxy, and a multistep reaction sequence for 2-methylpropan-2-yl radical with molecular oxygen. These changes improv ed the calculation for the overall reactivity and the concentration profile s of the following primary products: formaldehyde, acetone, isobutene; 3,3- dimethyloxetane, methacrolein, carbon monoxide, carbon dioxide, and water. Experiments indicate that neopentane shows negative temperature coefficient behavior similar to other alkanes, though it is not as pronounced as that shown by n-pentane for example. Modeling results indicate that this behavio r is caused by the beta-scission of the neopentyl radical and the chain pro pagation reactions of the hydroperoxyl-neopentyl radical. (C) 1999 by The C ombustion Institute.