NSF/EPA: Nearcritical Water for Environmentally Benign Chemical Processing

点击翻译按钮获取中文摘要

9613063 Eckert Nearcritical water (NCW) is an environmentally-benign solvent that offers tremendous opportunities for pollution prevention for a wide variety of manufacturing processes in the chemical, petrochemical, pharmaceutical, and plastics industries. In the range 250-350C, NCW has a density and dielectric constant similar to that of ambient acetone, permitting the dissolution and reaction of both organic and ionic species, as well as the swelling of polymers. Unlike supercritical water, which is used for complete oxidation (usually 400C), the more moderate temperatures permit a wider range of useful reactions. Finally, NCW has an ionization constant which is three orders of magnitude greater than water at ambient temperatures and pressures. This latter property should facilitate promotion of acid- and base- catalyzed reactions in the absence of added mineral acids and bases. This investigation proposed first to gather, evaluate critically, expand, and model the database of thermodynamic data (primarily solubilities) for organics in NCW. Next kinetic data will be obtained for a variety of important reactions which are of industrial interest. Such information will facilitate the commercialization of this technology by industry, especially by the active collaborator on this proposal, DuPont. The reactions that will be run will be: o Friedel-Crafts alkylation reactions o Friedel-Crafts acylation reactions o Oxidation of alkyl aromatics o Hydrolytic depolymerization of condensation polymers o Isomerization reactions o Hydrolysis of cellulose We already have preliminary kinetic data that demonstrate that one alkylation reaction can be run successfully without any added acid catalyst, and that an acylation reaction can be run with only traces of a catalyst in place of the 2-3 fold molar excess of AlCl 3 usually used. As a result of these investigations, new processes will be available using "green chemistry" for sustainable development. NCW will replace ma ny less desirable solvents, such as aromatic hydrocarbons and chlorinated compounds, it will avoid the use of polluting mineral acids and hazardous catalysts, it will permit the minimization of even the elimination of unwanted byproducts, it will provide better control of reactions which can be run homogeneously instead of heterogeneously, and it will facilitate closed processes by reuse of waste material. ***