Large-Scale Chemical Purification via Molecular Recognition Grant uri icon

abstract

  • The purpose of this project is to develop general strategies for the removal of undesirable components from high-temperature chemical processes, using the principles of molecular recognition. Specific systems will be designed to improve the synthesis of the fungicide chlorothanonil (CTL), by selectively and economically extracting chlorinated contaminants and/or their precursors from process streams. Molecular recognition is a relatively new field of chemistry, and is not widely used in production-scale separations. In situations where "engineering" solutions are not completely successful (e.g., the desired and undesired compounds have similar physical behavior), it may allow for extraction of materials based upon their atomic-level properties (shape, electron distribution, etc.). The industrial synthesis of CTL offers the opportunity to assess the feasibility of this approach. CTL is produced on a multi-ton scale each day, for application on farmland the world over. A key step in the synthesis of CTL involves a high-temperature chlorination of isophthalonitrile ("IPN"). Under these extreme conditions, a fraction of hydrocarbon byproducts in the IPN stream are converted into polychlorinated biphenyls (PCBs), which remain present in trace amounts after physical manipulations. Production of CTL can be viewed, in a highly simplified manner, to be the result of two reactions: an amoxidation that generates IPN, and a subsequent chlorination (see above). Removal of undesired material could take place after either or both steps. For both stages of the process, artificial "host" molecules will be designed to bind the unwanted byproducts, by exploiting steric and electronic differences between the molecules present. Host binding strengths and selectivities will be assessed in solution using standard techniques such as NMR, UV -vis, and ITC. The most promising hosts will be optimized for high-temperature stability and efficacy, then immobilized on solid media for implementation in a plant setting.

date/time interval

  • July 2007 - June 2009