Decomposition studies of isopropanol in a variable pressure flow reactor

Abstract

Alternatives to traditional petroleum derived transportation fuels, particularly alcohols, have been investigated increasingly over the last 5 years. Isopropanol has received little attention despite bridging the gap between smaller alcohols (methanol and ethanol) and the next generation alcohols (butyl alcohols) to be used in transportation fuels. Previous studies have shown that decomposition reactions that dehydrate are important in the high-temperature oxidation of alcohols. Here we report new data on the dehydration reaction for isopropanol (iC(3)H(7)OH -> C3H6 + H2O) in a Variable Pressure Flow Reactor at 12.5 atm pressure and temperatures from 976-1000 K. Pyrolysis experiments are performed in the presence of a radical trapper (1,3,5 trimethyl benzene or toluene) to inhibit secondary reactions of radicals with the fuel and product species. The recommended rate constant for the dehydration reaction is determined using an indirect method along with Latin Hypercube sampling to estimate uncertainties. Comparison of the rate constant data to previous works show that the reaction is considerably more rapid than the high level theoretical predictions of Bui et al. (Bui et al., J. Chem. Phys., 2002). The dehydration reaction rate for isopropanol is well described by k = 8.52 x 10(6)T(2.12) exp(-30, 667/T) with an estimated uncertainty of sigma(2)(lnA) = 0.0195.The C-C bond fission reaction is also investigated, but the insensitivity of the decomposition data to this reaction results in an uncertainty in the determined rate constants to approximately 2 orders of magnitude. Theoretical estimates lie within these experimental uncertainties.