This dissertation study addresses two important topics—development of a non-phosgene route for manufacture of isocyanates & a life cycle analysis comparison between polycarbonate and Tritan.
Isocyanates are currently manufactured by the phosgenation route which involves reaction of an amine with phosgene. This process requires handling of hazardous chemicals and is not considered environmentally benign due to issues related to disposal / recycle of the hydrochloric acid formed as a byproduct. McGhee et al  have previously worked on a non-phosgene route for manufacture isocyanates from primary amine, carbon dioxide, nitrogenous base and an electrophilic dehydrating agent. However, due to the generation of large amount of salt of the dehydrating agent and the base, and due to the absence of an appropriate recycling strategy this route could not be commercialized. To reduce the salt formed, a modification to this route is presented by eliminating the use of the nitrogenous base and carrying out the reaction in excess of carbon dioxide. The effect of different solvents, dehydrating agents, varying temperature and pressures on the conversion to isocyanate and a recycling strategy for the byproducts formed has been studied. The energy requirement for this process is compared with the traditional route using ASPEN Plus. The results have been used to understand the potential roadblocks in the commercialization of the new process and the future direction of work to improve it.
The second part of the study is a life cycle analysis (LCA) comparison of polycarbonates with Tritan, which has been claimed to be an effective replacement for polycarbonates as it does not contain bisphenol-A, but still matches its physical and mechanical properties. However, the environmental impacts due the production of Tritan had not been studied yet. Hence, LCA study for polycarbonate and Tritan is performed on the basis of published literature. Effect due to different recycling strategies and different allocation techniques are studied on the overall environmental impact of these polymers. The study indicates that Tritan has lower impacts compared to polycarbonates in most of the impact categories studied. However, the extent to which Tritan performs better strongly depends on the functional unit considered.
|Advisor:||Beckman, Eric J.|
|School:||University of Pittsburgh|
|School Location:||United States -- Pennsylvania|
|Source:||DAI-B 73/03, Dissertation Abstracts International|
|Subjects:||Polymer chemistry, Chemical engineering, Sustainability|
|Keywords:||Aspen, Green design, Isocyanate, Life cycle, Non-phosgene, Polycarbonate, Polymer industry, Tritan|
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