Green industrial solvents

In order to reduce the adverse impacts of chemicals the National Research Council provided a number of recommendations that would assist in linking science and technology to society s environmental goals (Division, 1996). Let us use these as a measuring stick to begin a discussion of green industrial solvents. 

One of the key components of any green industrial process has to be the selection of the solvent, since working with conventional solvents results in the emission of volatile organic compounds (VOCs), a major source of environmental pollution (see Figure 5.4). There are four principal strategies to avoid conventional organic solvents ... 

Seddon, K. R. QUILL rewrites the future of industrial solvents. Green Chem., 1999, 1, G58-G59. 

The list of green solvents is given below. This list may be found at http //www. epa.gov/greenchemistry/tools.htm. Many of the solvents on the list are commercial and industrial solvents. The list also includes many solvents that are hardly of any industrial interest, but still may be useful in laboratory situations or interesting from a theoretical point of view. 

Along with methods to evaluate different pharmaceutical processes and unit operations, several methods have also been developed to evaluate commonly used solvents in the pharmaceutical industry. Solvents still account for a majority of the mass utilization in any pharmaceutical process. Therefore, various methods have been developed which focus on measuring the greenness of solvents, locating possible alternatives and reducing the overall amount of solvent used in any given process. Some of these methods use a combination of physical property data, LCA... 

Mimaya T.A., Volkov S.V. Ionic Liquid Crystals as Universal Matrices (Solvents).- Green industrial applications of ionic liquids. NATO Science Series, II Mathematics, Physics and Chemistry. Kluwer Academic Publ., 2003. P. 439-456. 

Another very important green chemistry solvent is supercritical water (SCW) [14], Water under supercritical conditions is an extremely powerful oxidizing and cleansing agent that has been proven remarkably promising as a soil decontaminant by efficiently degrading persistent organic toxic wastes that are difficult to eliminate from polluted soils, and in the treatment of several types of industrial wastes such as textile and cellulose wastewater [2],... 

During the 1990s, two truly novel green approaches to industrial solvents began to mature. One of these involves tbe use of ionic liquids and tbe other supercritical carbon dioxide. The term ionic liquids almost suggests an oxymoron (internal inconsistency). One normally... 

R.M. Pagni, Ionic Uquids as alternatives to traditional organic and inorganic solvents , presented at NATO Advanced Research Workshop, Green Industrial Applications of Ionic Liquids, HerakUon, Crete, Greece, 2000. 

A major concern with regard to sustainability is the release of hazardous substances into the environment. Green chemistry can have a significant impact in this area. Solvents, for example, are ubiquitous in academic, industrial, and government laboratories. In the chemical process, industrial solvents are used in various process operation steps, such as... 

This compound used to be employed as an industrial solvent and was used in cutting oils. However, workers exposed to it suffered liver damage and developed jaundice, and the compound, as well as other nitrosamines, was found to be a carcinogen. A number of other nitrosamines were later found in industrial materials and as by-products of food processing and preservation. Because of their potential as carcinogens, nitrosamines are avoided in the practice of green chemistry. 

In recent years, ionic liquids have emerged as possible "green solvents", that is environmentally benign substances mainly because they have negligible vapor pressure (Liu et al., 2005). One of the primary driving forces behind research into ionic liquids is the perceived benefit of substituting traditional industrial solvents, most of which are volatile organic compounds (VOCs), with nonvolatile ionic liquids. Replacement of conventional solvents by ionic liquids would prevent the emission of VOCs, a major source of environmental pollution (Polshettiwar Varma, 2008). 

In recent years, much attention has been paid to the environmental impact of industrial processes, and this has promoted increasing efforts toward green chemistry. Solvents play a very important role in the chemical industry. Solvents can influence reaction processes through their effect on solubihties, transport properties, separations, and the reaction rate and selectivity through the solvation effect. Since most of the solvents in current use are derived direcdy or indirectly from petroleum, there are significant drivers to find replacements for conventional solvents to reduce the environmental impact [1]. 

The discussion is organized in the following order First the advantages of HRC scheme, relative to the industrial (i.e., heterogenous) process are briefly commented on second, the relevance of celMose activation and the physical state of its solution to optimization of esterification are discussed. Finally, the use of recently introduced solvent systems and synthetic schemes, designed in order to obtain new, potentially useful cellulose esters with controlled, reproducible properties is reviewed. A comment on the conformity of these methods with the concepts of green chemistry is also included. 

As a cautionary note PTC should not be considered a panacea for all of the problems associated with green chemistry. Two-phase reactions involving water are often difficult to deal with industrially, particularly if the water is contaminated with trace amounts of hazardous organic substances. In some cases it may be more practical, cost effective and environmentally prudent to avoid production of aqueous waste in favour of a recyclable less benign solvent. 

Decaffeination of Coffee and Tea This application is driven by the environmental acceptability and nontoxicity of CO2 as well as by the ability to tailor the extraction with the adjustable solvent strength. It has been practiced industrially for more than two decades. Caffeine may be extracted from green coffee beans, and the aroma is developed later by roasting. Various methods have been proposed for recovery of the caffeine, including washing with water and adsorption. 

Pyrrolidones fit well into the bio-refinery concept since they may be produced in a scheme beginning with the fermentation of a portion of the bio-refineiy s sugar product into succinate. Pyrrolidones are a class of industrially important chemicals with a variety of uses including polymer intermediates, cleaners, and green solvents which can replace hazardous chlorinated compounds. 

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