We report successful alkylation reactions in near-critical water in the absence of added acid catalysts. Water has a strong tendency to ionize as the temperature is increased, allowing water in the near-critical region (250-350 °C) to act as an effective acid catalyst. By simultaneously employing near-critical water as the reaction solvent and catalyst, the need for environmentally hazardous organic solvents and acid catalysts is eliminated. The high hydronium ion content of near-critical water proved to be sufficient to synthesize a variety of substituted phenols with tertiary, secondary, and even primary alcohols. The reaction products for each of these reactions are reported.

For any valid study of reaction kinetics the phase equilibria involved must be known. We present an apparatus designed to measure both phase equilibria and kinetics for reactions in near-critical water. Liquid−liquid mutual solubilities are reported for the benzene−water and toluene−water systems from 200 to 275 °C at the three-phase pressures and 172 bar. These data were found to be in good agreement with data reported in the literature. Additionally, the near-critical water reaction apparatus was used to verify one-phase regions for the phenol−water and p-cresol−water systems from 250 to 300 °C at 172 bar.

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Quantitative kinetics for the alkylation reactions of phenol and p-cresol with tert-butyl

A chromatographic technique was used to measure experimental capacity factors for the n-alkanes from C9H20 to C36H74 in CO2 from 308.2 to 348.2 K and from 100 to 240 bar. Infinite dilution activity coefficients, γ i ∞, were calculated for the solid n-alkanes (C24H50 to C36H74) utilizing regular solution theory to characterize the stationary phase. This allowed the estimation of solubilities from capacity factors for the solid n-alkanes in CO2.