Solvents life cycle analysis

Handbook of Green Chemistry and Technology, J. H. Clark and D. J. Macquarrie, Eds., Blackwell Publishing 2002, 540 pp., ISBN 0-632-05715-7. This collection of 22 review essays covers all the important areas of green chemistry, including environmental impact and life-cycle analysis, waste minimization, catalysts and their industrial applications, new synthesis methods, dean energy, and novel solvent systems. The chapters are well referenced and contain pertinent examples and case studies. 

ILs are also attractive candidates for replacing volatile organic compounds (VOCs) as solvents, because they have practically no vapor pressure [165]. However, the environmental impact of ILs and VOCs should be compared on the basis of life-cycle analysis, and for that we are still missing many data on the toxicity and environmental effects of I Ls [ 166,167]. Another point is that the current prices of I Ls are much higher than those of VOCs. Handy et al. recently demonstrated a handy synthesis of mim-type ILs starting from fructose, which could eventually lead to truly eco-friendly IL solvents [168]. 

Perfluorinated molecules are prepared from their hydrocarbon analogues by electrochemical fluorination or by fluorination using cobalt trifluoride. Functional perfluorinated molecules are then used to prepare the tagged catalysts and reagents (Figure 7.4). Therefore, in terms of life cycle analysis, fluorous solvents are not as green as a solvent that does not need to be prepared, e.g. water, or a solvent that requires little substrate modification, e.g. a renewable VOC. However, the ability of FBSs to perform efficient separations often reduces the overall amount of solvent that is required in a process and therefore they are considered green alternative solvents. 

Manufacturing processes for sustainability can be optimized in the context of life cycle analysis (Shoimard and Hiew 2000). It involves definition of the process boundaries and quantifiable sustainability impacts in the form of established metrics, incorporated into process design and optimization. It has been applied to determining waste treatment options, abatement of pollution, and designing the optimal recipe of solvents. Impact indices, such as ozone depletion potential to human toxicity and eco-toxicity, developed by the EPA, can be used. This method has been applied in a methyl ethyl ketone production plant to determine the effect of recycling on the enviromnent (Shonnard and Hiew 2000). 

Capello, C., Hellweg, S., Badertscher, B., Hungerbuhler, K. (2005) Life-Cycle Inventory of Waste Solvent Distillation Statistical Analysis of Empirical Data. Environmental Science and Technology, 39, 5885-5892. 

The first step of the possible methodology is to identify the physical chemical properties the solvent mnst possess for a given application. A detailed engineering analysis of the application will yield many performance constraints. Constraints are also obtained considering the solvent s entire life cycle. 

Capello, C., S. Helleweg, B. Badertscher, and K. Hungerbiihler. 2005. Life cycle inventory of waste solvent distillation Statistical analysis of empirical data. Environ. Sci. Technol. 39 5885-5892. 

One further approach to incorporating the principles of green chemistry into solvent selection with process redesign (beyond tables of which solvents are or are not acceptable) is to evaluate the chemical characteristics of the desired solvent (or the solvent it is replacing) within the life-cycle of the entire chemical process (21). In this analysis disposal economics and safety concerns become critical considerations. Once these factors are summed, including a similar evaluation of the solvent in question, the true environmental cost of the process is found. Based upon the results of the analysis, new information is gained toward selection of the appropriate solvent or chemical procress. 

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