Solvents alternative solvents

A single repository for pollution prevention, compUance assurance, and enforcement information databases has the database umbrella architecture for solvent alternatives solvent substitution data systems Integrated Solvent Substitution Data System (ISSDS) Hazardous Solvent Substitution Data System on-line product information, material safety data sheets... 

Carbon disulphide should never be used if any alternative solvent is available, as it has a dangerously low flash-point, and its vapours form exceedingly explosive mixtures with air. Ether as a solvent for recrystallisation is much safer than carbon disulphide, but again should be avoided whenever possible, partly on account of the danger of fires, and partly because the filtered solution tends to creep up the walls of the containing vessel and there deposit solid matter by complete evaporation instead of preferential crystallisation. 

In a solid-phase extraction the analytes are first extracted from their solution matrix into a solid adsorbent. After washing to remove impurities, the analytes are removed from the adsorbent with a suitable solvent. Alternatively, the extraction can be carried out using a Soxhlet extractor. 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

For worker exposure to trichloroethylene vapor, OSHA set a maximum eight-hour time-weighted average (TWA) concentration of 100 ppm. This severely restricted certain appHcations, and many organizations converted to other chlorinated solvents. As a result, U.S. production of trichloroethylene declined about 70% from a peak in 1970 (Table 2). In 1989, OSHA lowered the permissible exposure limit (PEL) from 100 ppm eight-hour TWA to 50 ppm eight-hour TWA (33). This added further pressure for some users to consider changing to alternative solvents. 

Ethylene Oxide Recovery. An economic recovery scheme for a gas stream that contains less than 3 mol % ethylene oxide (EO) must be designed. It is necessary to achieve nearly complete removal siace any ethylene oxide recycled to the reactor would be combusted or poison the carbon dioxide removal solution. Commercial designs use a water absorber foUowed by vacuum or low pressure stripping of EO to minimize oxide hydrolysis. Several patents have proposed improvements to the basic recovery scheme (176—189). Other references describe how to improve the scmbbiag efficiency of water or propose alternative solvents (180,181). 

Hot feed Provide and maintain an automated inerting (increases system—oxygen concentration or pressure fire/explosion risk controlled with flammable. Eliminate leakage sources (ftimes/air) solvents). Use alternative solvents (nonflammable or less flammable) Reduce feed temperature and/or monitor temperature of feed and interlock with feed shutdown NFPA 69... 

Use alternate solvent with reduced static potential Use conductive materials of construction Add antistatic agent to nonpolar solvent Check conductivity prior to feeding Use static dissipating linings if applicable... 

Benzene, which has been used as a solvent successfully and extensively in the past for reactions and purification by chromatography and crystallisation is now considered a very dangerous substance so it hasto be used with extreme care. We emphasise that an alternative solvent system to benzene (e.g. toluene, toluene-petroleum ether, or a petroleum ether to name a few) should be used first. However, if no other solvent system can be found then all operations involving benzene have to be performed in an efficient fumehood and precautions must be taken to avoid inhalation and contact with skin and eyes. Whenever benzene is mentioned in the text an asterisk e.g. C Hg or benzene, is inserted to remind the user that special precaution should be adopted. 

A new regulation is passed requiring greatly reduced atmospheric emissions of organic solvents, including solvent A. The manager has several alternatives ... 

A solvent used in an exothermic reaction is nonvolatile, and moderately toxic. An alternative solvent is less toxic, but also has a much lower boiling point. There is a trade-off between toxic hazards and the potential for tempering the exotherm, but also generating pressure from boiling solvent in case of a runaway reaction. 

In many cases, it is possible to replace environmentally hazardous chemicals with more benign species without compromising the technical and economic performance of the process. Examples include alternative solvents, polymers, and refrigerants. Group contribution methods have been conunonly used in predicting physical and chemical properties of synthesized materials. Two main frameworks have... 

Inhibited THF is problematic for semipreparative separations. Because small quantities of polymer are being collected along with larger volumes of solvent, more inhibitor, usually butylated hydroxytoluene (BHT), than sample is often collected in each fraction. Thus, one must carefully consider if the BHT will cause a problem in the subsequent analysis of the isolated fractions. If it does, uninhibited THF or other alternate solvents should be used. It must be remember that if uninhibited THF is used, the analyst must pay careful attention to the inevitable peroxide formation in the solvent/fractions. 

The synthetic sequence is usually cariied out in liquid ammonia as the solvent. Alternatively, diethyl ether or tetrahydrofuran may be used. 

As already noted (p. 1073), the platinum metals are all isolated from concentrates obtained as anode slimes or converter matte. In the classical process, after ruthenium and osmium have been removed, excess oxidants are removed by boiling, iridium is precipitated as (NH4)2lrCl6 and rhodium as [Rh(NH3)5Cl]Cl2. In alternative solvent extraction processes (p. 1147) [IrClg] " is extracted in organic amines leaving rhodium in the aqueous phase to be precipitated, again, as [Rh(NH3)5Cl]Cl2. In all cases ignition in H2... 

Obviously, there are many good reasons to study ionic liquids as alternative solvents in transition metal-catalyzed reactions. Besides the engineering advantage of their nonvolatile natures, the investigation of new biphasic reactions with an ionic catalyst phase is of special interest. The possibility of adjusting solubility properties by different cation/anion combinations permits systematic optimization of the biphasic reaction (with regard, for example, to product selectivity). Attractive options to improve selectivity in multiphase reactions derive from the preferential solubility of only one reactant in the catalyst solvent or from the in situ extraction of reaction intermediates from the catalyst layer. Moreover, the application of an ionic liquid catalyst layer permits a biphasic reaction mode in many cases where this would not be possible with water or polar organic solvents (due to incompatibility with the catalyst or problems with substrate solubility, for example). 

To overcome these limitations, there has been a great deal of investigation of novel methods, one of them focused on the search for alternative solvents [6, 7]. Table 5.3-1 gives different approaches to biphasic catalysis, with some of their respective advantages and limitations. 

The epoxy-acrylic resin referred to above is a graft copolymer prepared by the polymerisation of acrylic monomers in the presence of the epoxy resin in such a way that grafting of the acrylic onto the epoxy takes place. Water dispersibility is achieved by neutralising carboxyl groups in the acrylic polymer chain with ammonia or amine. Amino or phenolic resins are used as crosslinkers. Alternatively, solvent-borne epoxy-amino or epoxy-phenolic lacquers can be used. 

Solid samples are generally treated in one of two ways. If completely soluble, they can be dissolved directly and completely in a suitable solvent. Alternatively, if the samples contain insoluble materials that are of no interest, then they can be extracted with a selected solvent to obtain the relevant compounds in solution. The extract can be subsequently filtered or centrifuged to remove any unwanted substances that make up the sample matrix. The procedure will differ, depending on the amount of the substances present that are germane to the analysis. The preparation of samples for LC analysis from solid... 

As outlined above, immobilization in a fluorinated liquid phase demands the functionahzation of the ligand with perfluoroalkyl chains and, even then, the solubihty is strongly influenced by the nature of the complex. Ionic hquids of the alkylmethyhmidazolium type (Fig. 4) have been recently developed as alternative solvents for organometallic catalysis and have the practical advantage of using directly the commercially available chiral hgands and complexes. 

Examples of more recent work on this topic have been published, for example by Hellweg et and Bauer and Maciel using LCA for the comparison of different solvent alternatives... 

Alternative solvents were also tested. Isopropanol and methyl tertiary-butyl ether (MTBE) with water (HCl), the latter a two-phase system, the displayed reaction rates were much slower. 

For selection of alternative solvents (non-ozone depleting) for separation processes (extraction and HPLC mobile phase optimisation) references [24,25] are very useful. 

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