Roles of water for chemical reactions in high-temperature water

Hot compressed water (HCW, here water above 200 °C) possesses very interesting properties This series of articles gives an overview of the state of the art as regards the understanding of reactions in HCW In the first part the macroscopic and microscopic properties of HCW will be described, followed by a summary of synthesis reactions published The impact of the unique properties shall be discussed in part II, with the thermal degradation of tert-butylbenzene and the oxidation of methanol being used as examples The studies reported will show that the microscopic properties are of more importance to understanding reactions in HCW than assumed in the past

Hot compressed water as reaction medium and reactant properties and synthesis reactions

Hot compressed water (HCW, here water above 200 °C) owns interesting properties The impact of the unique properties is discussed exemplary for the thermal degradation of tert-butylbenzene and the oxidation of methanol Both reactions have been conducted not only in HCW but also in other high-pressure media and from the comparison the impact of the special properties of HCW can be settled In addition the degradation of glycerol, a model substance for carbohydrates and biomass in HCW was studied This reaction shows a strong dependence on the properties of HCW The examples picture an increased specific impact of HCW with rising polarity of the reactants and intermediates The studies also points to higher importance of microscopic properties for understanding reactions in HCW than assumed in the past

Hot compressed water as reaction medium and reactant. 2. Degradation reactions

The task of this work was to gain a better understanding of the hydrolysis of esters in sub- and supercritical water (SCW). Therefore, the kinetics of the hydrolysis of ethyl acetate as a model reaction was studied in the pressure and temperature range of 23–30 MPa and 250–400°C, respectively. The corresponding reaction mechanisms in sub- and supercritical water were discussed.

Hydrolysis of esters in subcritical and supercritical water

The selective removal of nitrogen-containing compounds from oil and oil fractions is of interest because of the potential deleterious impact of such compounds on products and processes. Problems caused by nitrogen-containing compounds include gum formation, acid catalyst inhibition and deactivation, acid–base pair-related corrosion, and metal complexation. A brief overview of the classes of nitrogen compounds found in oil is provided. The review of processes to remove nitrogen from oil emphasizes studies that investigated denitrogenation of industrial feedstocks, such as refinery fractions, heavy oils, and bitumens. The main topics covered are hydrotreating, liquid–liquid phase partitioning, solvent deasphalting, adsorption, chemical conversion followed by separation, and microbial conversion. Chemical conversion processes include oxidative denitrogenation, N-alkylation, complexation with metal salts, and conversion in high-temperature water. There are many processes for denitrogenation by separation of t...

David M. Tiffany

Papers

Reactivity of some organic compounds with supercritical water