On-line monitoring of the hydrolysis of acetonitrile in near-critical water using Raman spectroscopy

The hydrolysis of CH3CN in near-critical water, without added catalyst, has been successfully monitored with on line Raman spectroscopy, up to 350 degreesC at 300 bar. Using a unique miniature high pressure and high temperature (HTHP) spectroscopic cell, in situ quantitative measurements with Raman spectroscopy have allowed the pseudo-first-order rate constant and the activation energy for the reaction to be calculated. The effects of temperature, pressure, density, dielectric constant, ionic product of water and initial CH3CN concentration on the reaction rate have also been investigated. The reaction involves the formation of CH3CONH2 as an intermediate, and gives CH3COOH as the final product. No other products have been detected in the effluent. Water plays the role of solvent, reactant and acid catalyst at the same time, whereas the reaction also shows an autocatalytic effect, due to CH3COOH which accumulates in the system as the reaction progresses. (C) 2004 Elsevier B.V. All rights reserved.