Solvent Recycling Technologies

The first approach to reducing eluent consumption presented above was the optimization of chromatographic processes to reduce the amount of solvent used to 

The final approach to the reduction of eluent consumption is the optimal recycling of solvents. Indeed, preparative and industrial chromatography can be designed as a unit operation that includes solvent recycling dry feed mixture is injected while dry separated compounds are recovered. Many techniques can be applied depending on the situation in isocratic (that is with a constant mobile phase composition) or gradient conditions, and with organic and/or supercritical eluents. 

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The Terra-Kleen solvent extraction technology is an on-site, batch-process system that uses a proprietary solvent to remove hazardous organic constituents from soils. The treatment system uses a solvent regeneration system that concentrates the extracted contaminants and then recycles the extraction solvent. The treated soil can often be returned to the site. The concentrated contaminants are usually transported off-site for disposal. 

Despite the moderate yields to AA achieved by the various technologies developed, the One-Step AA process has not yet been implemented at a commercial level, because of the high corrosivity of acetic acid and the high energy demand for solvent recycle and product workup. Moreover, the per-pass conversion and selectivity is generally lower than the two-step process from cyclohexane. Finally, traces of acetic acid are left in the product even after repeated crystallization steps, which lower the quality of the product and limit its use in polyamide synthesis. 

In bulk and solution processes, the polymer product may often need removal of unreacted monomer and solvent. Several technologies are available that use high vacuum and temperature to strip the unreacted monomer and solvent from the resin. In most cases, the unreacted material can be condensed and recycled back to the process for further use or optionally burned as fuel. 

Met-Mex Penoles, by introducing solvent extraction technology, was able to achieve flexible operations for treating lead concentrates, a reduction in secondary materials recycling and economic benefits because of additional zinc recovery as well as a new agricultural product. 

The purported benefits of gas-phase technology include the reduction in overall waste streams, including no waste water, lower solid waste, and reduced overall emissions. Solvent recycling is no longer necessary, and costly polsuner product isolation and drying steps are not required. Products are typically isolated from the reactor as powder or crumb. Production costs have the potential to be significantly lower than either solution or emulsion technologies. 

Vane, L, and Rodriguez, F. Selective Dissolution Multi-Solvent, Low Pressure Solution Process for Resource Recovery from Mixed Post-Consumer Plastics" Proceedings of the Society of Plastic Engineers Regional Technical Conference -Recycling Technology of the 90 s. Chicago, IL. 1990. 

Recycle/reuse involves the use of pollutant-laden streams within the process. Typically, separation technologies are key elements in a recycle/reuse system to recover valuable materials such as solvents, metals, inorganic species, and water. 

BP Chemicals studied the use of chloroaluminates as acidic catalysts and solvents for aromatic hydrocarbon allcylation [41]. At present, the existing AICI3 technology (based on red oil catalyst) is still used industrially, but continues to suffer from poor catalyst separation and recycling [42]. The aim of the work was to evaluate the AlCl3-based ionic liquids, with the emphasis placed on the development of a clean... 

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