Decomposition of solvents

In some cases, fractional freezing is more effective than distillation after chemical pretreatment, because thermal decomposition of solvents, caused by distillation, can be avoided. Fractional freezing has been employed in purifying DM SO (mp 18.5 °C), pyridine (mp —41.6°C) and HMPA (mp 7.2 °C). 

Tahraqui, A., Morris, J.H. 1995. Decomposition of solvent extraction media during nuclear reprocessing Literature review. Sep. Sci. Technol. 30 (13) 2603-2630. 

Absorbent and strippers are very seldom irothermal. In the case of absorbers, the heat of solution or reaction of the solute with the solvent tends to inciesee the lemperaiune, while partial evaporation of the solvent provides some coeling. In the case or strippers, ihe decomposition of solvent-solute compounds and the release of solute from the solvent are usually endothermic, while haai often is provided by the condense ion of stripping vapor within the lower. In both cases, heal is transferred between the gas and liquid streams... 

Ban, S., J. J. Zhang, L. Zhang, K. Tsay, D. T. Song, and X. T. Zou. 2013. Charging and discharging electrochemical supercapacitors in the presence of both parallel leakage process and electrochemical decomposition of solvent. Electrochimica Acta 90 542-549. 

Tasaki, K. Kanda, K. Kobayashi, T. Nakamura, S. Ue, M. Theoretical studies on the reductive decompositions of solvents and additives for fithiran-ion batteries near lithium anodes,... 

Electrodes are arranged in a bipolar configuration. These are low-voltage devices and breakdowns occur due to decomposition of solvent. The thermodynamic limit for an aqueous solution is around 1.2 V, while for a non-aqueous system it is 3.35 V... 

On the other hand, it is clear that the precipitate layer has a role in suppressing further reductive decomposition of solvent molecules on the basal plane. The layer most probably consists of polymerized compounds with oxyethylene units as mentioned above. In EC + DEC, the precipitate layer is fairly porous as shown in Eigure 10(a). Hence the surface was not completely passivated during the first cycle, and the precipitate layer grew even during the second cycle, which will lead to an irreversible capacity in practical batteries. In this respect, a solvent system or an additive that gives a dense layer of decomposition products are preferable in order to reduce the irreversible capacity. 

In this chapter, the authors focused on the role of solvent co-intercalation in SEI formation on graphite anode, and discussed the mechanistic aspects of SEI formation using the results obtained by STM and AFM. It was revealed that two steps are involved in SEI formation on graphite anode in EC-based solutions (i) solvent co-intercalation and its decomposition beneath the surface at around 1 V and (ii) direct decomposition of solvents on the basal plane to form a precipitate layer at lower potentials. The presence of the decomposition products (blisters) in the interlayer space prevents further solvent cointercalation. On the other hand, the precipitate layer formed on the surface has a role in suppressing further reductive decomposition of solvent molecules on the basal plane. The precipitate layer most probably consists of polymerized compounds with oxyethylene units. 

Scheme 1 The cluster-continuum model employed to investigate the reductive decomposition of solvent. Sol solvent molecules X salt anions.

The transfer of the chain to another monomer molecule is followed by the increase of next macroradical. In that case the pol5mierization reaction rate does not change. The transfer of the chain on a solvent molecule, able to create relatively persistent free radicals leads to the formation of oligomeric products terminated by large substituents, coming from the decomposition of solvent molecule. These substituents determine the properties of the resulting compounds, called telomeres. This issue will be discussed larger in the chapter devoted to the polymerization in solution. 

Lithium deposition on the negative electrode and decomposition of solvents... 

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