Replacing conventional solvents

More than 4.5 million metric t of solvents is used in the United States annually, and it has been suggested by industry experts that ethyl lactate could replace conventional solvents in more than 80% of these applications (34). Vertec Biosolvents Inc. is currently using ethyl lactate in soy oil-solvent blends. Applications targeted by Vertec Biosolvents include conventional solvents that are under environmental scrutiny such as methylene chloride, methyl ethyl ketone, and N-methyl pyrrolidone (36). Table 3 lists the selling prices of some common solvents. 

Another environmentally benign solvent is supercritical water, which has a great potential to replace conventional solvents, although it requires rather harsh experimental conditions tc = 374 °C and Pc = 218 atm see Table 3-4) [224, 225]. At the critical point of SC-H2O, its volume is three times larger than that at ambient temperature, its relative permittivity is only 5.3 (compared to e, = 78.4 at 25 °C), and its intermolecular hydrogen-bond network is partially broken. Under supercritical conditions, water consists of small clusters, oHgomers, and even monomeric gas-like water molecules [226,... 

A further useful application of SC-CO2 as a reaction medium is the free-radical side-chain bromination of alkylaromatics, replacing conventional solvents such as tetra-chloromethane or chlorofluorohydrocarbons having no abstractable hydrogen atoms [920]. For example, bromination of ethylbenzene in SC-CO2 at 40 °C and 22.9 MPa yields 95 cmol/mol (1-bromoethyl)benzene, with practically the same regioselectivity as obtained in conventional tetrachloromethane as the solvent. Even the classical Wohl-Ziegler bromination of benzylic or allylic substrates using A-bromosuccinimide (NBS) can be conducted in SC-CO2 [920]. Irradiation of a solution of toluene, NBS, and AIBN (as initiator) in SC-CO2 at 40 °C and 17.0 MPa for 4 hours gave (bromomethyl)-... 

A fluid is supercritical when it is compressed beyond its critical pressure (Pc) and heated beyond its critical temperature (r, ). Supercritical fluid technology has emerged as an important technique for supercritical fluid extraction (SFE). In many of the industrial applications, it has replaced conventional solvent-based or steam extraction processes, mainly due to the quality and the purity of the final product and environmental benefits. 

The use of supercritical fluids represents a way to replace conventional solvents. Recall that a supercritical fluid is an unusual state of matter that has properties of both a gas and a liquid, (Section 11.4) Water and carbon dioxide are the two most popular choices as su-... 

The use of supercritical fluids represents a way to replace conventional solvents. Recall that a supercritical fluid is an unusual state of matter that has properties of both a gas and a liquid, qqo (Section 11.4) Water and carbon dioxide are the two most popular choices as supercritical fluid solvents. One recently developed industrial process, for example, replaces chlorofluorocarbon solvents with liquid or supercritical CO2 in the production of polytetrafluoroethylene ([CF2CF2] , sold as Teflon ). Though CO2 is a greenhouse gas, no new CO2 need be manufactured for use as a supercritical fluid solvent. 

The first objective of our project is the application of vernonia oil as a reactive diluent for high solids alkyd, epoxy, and epoxy-ester coating formulations by replacing conventional solvents, which produce volatile organic compound (VOC) emission, with vernonia oil. 

The main uses of petroleum naphtha fall into the general areas of solvents (diluents) for paints, etc, dry-cleaning solvents, solvents for cutback asphalt, solvents in mbber industry, and solvents for industrial extraction processes. Turpentine, the older, more conventional solvent for paints, has been almost completely replaced by the cheaper and more abundant petroleum naphtha. 

Another approach to high soHds alkyd coatings is the partial replacement of solvent in a conventional long-oil alkyd with a reactive diluent. Eor example, dicyclopentenyloxyethyl methacrylate [70191-60-9J, mixed amides from the condensation of acrylamide (qv) (2-propeneamide)... 

Cleaning Supercritical fluids such as CO9 are being used to clean and degrease quartz rods used to produce optical fibers, produc ts used in the fabrication of printed circuit boards, oily chips from machining operations, and precision bearings in militaiy applications, and so on. Here, CO9 replaces convention chlorocarbon or chlorofluorocarbon solvents. 

Ambient-temperature ionic liquids have received much attention in both academia and industry, due to their potential as replacements for volatile organic compounds (VOCs) [1-3]. These studies have utilized the ionic liquids as direct replacements for conventional solvents and as a method to immobilize transition metal catalysts in biphasic processes. 

By replacing conventional 3.5 or 5 jtm columns with sub-2-micron columns, gradient time can be reduced dramatically. The flow rate must be increased for optimal conditions as well but solvent consumption will be less than the amount used by the original method. To use the full power of these columns, an LC instrument must be thoroughly optimized toward lowest extra-column dispersion. The smaller the column (small ID and short length), the more sensitive the performance is to dispersion. With smaller internal diameter columns, the injection volumes and internal diameters of the capillaries should be reduced. 

In view of the environmental concerns, SCCO2 represents a more environmentally friendly alternative to the traditional solvents. The general lack of reactivity could be essential to the future success of SCCO2 in replacing more conventional solvents. Even though SCCO2 has been touted as a modern remedy of many commercial problems, the use of CO2 as a solvent is complicated... 

Much of the current interest in using analytical-scale SFE systems comes from the need to replace conventional liquid solvent extraction methods with sample preparation methods that are faster, more efficient, have better potential for automation, and also reduce the need for large volumes of potentially hazardous liquid solvents. The need for alternative extraction methods is emphasized by current efforts to reduce the use of methylene chloride as an extraction fluid for environmental sample preparation [158]. The potential for applying SFE to a wide variety of environmental and biological samples for both qualitative and quantitative analyses is widely described in reviews [159-161] and the references therein. Analytical-scale SFE is most often applied to relatively small samples (e.g., several grams or less). 

Marsh, K.N. et al.. Room temperature ionic liquids as replacements for conventional solvents—A review, Kor. ]. Chem. Eng., 19, 357, 2002. 

The study of species in which ethylene is coordinated to transition metal centres holds great interest in areas of catalytic and polymerization chemistry (7). The bonding of the ethylene ligand to the metal centre in such species has been compared to that of the dihydrogen complexes described above (14,15,22). Photolysis of chromium hexacarbonyl, Cr(CO)6, in conventional solvents in the presence of dissolved ethylene gas is known to lead initially to a highly labile species in which one CO ligand is replaced by ethylene. Further photolysis leads to a more stable compound which contains two ethylene ligands trans to each other across the metal centre (25), equation 3. The conventional synthesis is experimentally difficult the two photochemical... 

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