Effect of Pressure on the Reaction Rate Constant at the Decomposition of Aliphatic Nitrocompounds in Supercritical Water

摘要

It was shown experimentally that the rate of aliphatic nitrocompounds (nitromethane, nitroethane and 1-nitropropane) decomposition in supercritical water (SCW) depends on pressure/density at constant temperature. The rate constant of RNO_2 decomposition in SCW decreased with increasing length of hydrocarbon radical R. The SCW density dependence of the apparent rate constant of decomposition of each of three compounds under consideration was found to correlate with the density dependence of the (H_3O)~+ concentration in dissociated SCW. The transition state theory has been applied to simulate the effect of pressure on the rate constants. The calculated values of activation volumes in the decomposition reactions of nitromethane, nitroethane and 1-nitropropane in SCW were similar that suggested the same nature of the activation complex in all three cases.