Combined Experimental and Theoretical Study on Neopentanol Pyrolysis

The multi-channel, unimolecular dissociation of neopentanol at high temperatures was studied by three experimental methods and a complementary high-level theoretical analysis. In addition to bond dissociation channels leading to radical products, two roaming radical channels have been previously hypothesized. Both channels form a unique signature product; one is methanol and the other is isobutane. Two experiments pyrolyzed neopentanol diluted in argon in SiC microreactors at external wall temperatures of Twall = 1273-1600 K. One used chirped-pulse Fourier transform millimeter-wave spectroscopy and the other synchrotron-sourced vacuum ultraviolet photoionization mass spectrometry to detect reaction products. Neither technique observed isobutane. However, both methods observed methanol and determined an upper limit of 5% at 1300 K for dissociation of neopentanol through the methanol-forming roaming channel. The third experiment used shock tube laser schlieren densitometry to measure the total rate constant ktot for dissociation of neopentanol and test potential reaction mechanisms. The experimental work was complemented by a high-level theoretical study that developed a potential energy surface for neopentanol dissociation. Master equation analysis yielded pressure and temperature-dependent rate coefficients for the main reaction channels. Both the shock tube and master equation results show that the studies were performed deep in the fall-off region. Good agreement between experiment and theory was observed. The validated theoretical rate constants were represented in the PLOG format, enabling their direct use in kinetic simulations of reacting systems containing neopentanol.