Propylene carbonate purification

While water has been used as a solvent more than any other media, nonaqueous solvents [e.g., acetonitrile, propylene carbonate, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), or methanol] have also frequently been used. Mixed solvents may also be considered for certain applications. Double-distilled water is adequate for most work in aqueous media. Triple-distilled water is often required when trace (stripping) analysis is concerned. Organic solvents often require drying or purification procedures. These and other solvent-related considerations have been reviewed by Mann (3). 

Although a number of solvents have been used by different workers, only a few enjoy continued favor. In Table 7.11 the physical properties of more than 50 solvents are listed (not all of them are aptotic). In the following paragraphs some of the properties and purification methods for four solvents are discussed acetonitrile, propylene carbonate (PC), dimethylformamide (DMF), and dimethyl sulfoxide (Me2SO). These are the most widely used solvents and prob-... 

J. F. Coetzee (ed.) Recommended Methods for the Purification of Solvents and Tests for Impurities, Pergamon Press, Oxford, 1982. (Acetonitrile, Sulfolane, Propylene carbonate. Dimethyl sulfoxide, V,7V-Dimethylformamide, Hexamethylphosphoric tiiamide. Pyridine, 1,2-Diaminoethane, N-Methylacetamide, and V-Methylpropionamide). 

Li metal served as a reference electrode and a IM-LiClO propylene carbonate solution was used as an electrolyte. Purification of the chemicals used and cell design and assembly were as previously reported (2). 

Phenol, formaldehyde in form of a 37% aqueous solution (formalin), and sodium hydroxide were purchased from Sigma Aldrich, Steinheim, Germany. Kraft lignin was supplied in the form of a dried black powder by Mead Westvaco Corporation, Charleston, South Carolina, USA. The salts potassium carbonate, zinc borate, and propylene carbonate were also purchased from Sigma Aldrich, Steinheim, Germany. All chemicals were analytical grade and used as such for the preparation of the resins without further purification. 

The standard composition of an electrolyte in LlBs is a mixture of cycUc carbonates (such as ethylene carbonate (EC) and propylene carbonate (PC)) and chain carbonates (such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC abbreviated as MEC below), and diethyl carbonate (DEC)), to which about 1 mol/L of a lithium salt (such as lithium hexafluorophosphate (LiPF )) is added. Ube Industries, Ltd. discovered that if small amounts of impurities exist in the electrolyte, decomposition current generated from the impurities begins to flow, which leads to the formation of undesirable thick SET This spurred the development of a pioneering high-grade purification process for the base electrolyte in 1997 [16]. High purity is a key feature of functional electrolytes developed by Ube Industries, Ltd. and enables production of transparent and chemically stable electrolytes, in contrast to the conventional electrolytes which were less stable and brown owing to its low purity (Fig. 3.1). 

Calleja, G., et al.. Multicomponent adsorption equilibrium of ethylene, propane, propylene and carbon dioxide on 13X-zeolite, Gas Sep. Purif, 8(4), 247-256 (1994). 

Common contaminants in commercial PC include propylene oxide, carbon dioxide, propanediols, allyl alcohol, ethylene carbonate, and water. Purification may be accomplished by percolation through 5 A molecular sieves (activated by treatment at 350 °C for 14 h under argon), followed by distillation under vacuum and storage under molecular sieves. 

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