Inherently alternative reaction routes

Inherently safer design of chemical processes involves the use of smaller quantities of hazardous materials, the use of less hazardous materials, the use of alternative reaction routes or process conditions to reduce the risk of runaway exothermic reactions, fires, explosions and/or the generation or release of toxic materials. 

Basic process chemistry using less hazardous materials and chemical reactions offers the greatest potential for improving inherent safety in the chemical industry. Alternate chemistry may use less hazardous raw material or intermediates, reduced inventories of hazardous materials, or less severe processing conditions. Identification of catalysts to enhance reaction selectivity or to allow desired reactions to be carried out at a lower temperature or pressure is often a key to development of inherently safer chemical synthesis routes. Some specific examples of innovations in process chemistry which result in inherently safer processes include ... 

Develop new less-energetic chemical reaction systems for product manufacture, including alternate catalytic and biological routes where appropriate Emphasize need to develop economically viable inherently safer systems at the research and development stages of new process development Develop new process equipment and strategies for product manufacture using lower inventories of reactive chemicals, error tolerant approaches, and process conditions further from limits of control where appropriate... 

The strategies also seek to come up with chemistries that are inherently safe. The considerations of alternative feedstocks and catalysts as well as new technologies such as biotechnology are necessary in identifying the superior synthesis route. Safety and environmental performance of the reaction byproducts are also important. 

Polyesters with higher aromatic content such as LCP are made via an alternative route. Because they are phenolic esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavourable reactivities. The usual method is reverse ester exchange or acidolysis reaction [38] where the phenolic hydroxyl groups are acylated with a lower aliphatic acid anhydride, and this ester is heated with an aromatic dicarboxylic acid, with or without catalyst. Many of these polymers are derived from hydroxyacids, and their acetates readily undergo self-condensation in the melt, stoichiometric balance being inherent to the reaction [39, 40]. 

Monsanto has developed and implemented an alternative DSIDA process that relies on the copper-catalyzed dehydrogenation of diethanolamine. The raw materials have low volatility and are less toxic. Process operation is inherently safer, because the dehydrogenation reaction is endothermic and, therefore, does not present the danger of a runaway reaction. Moreover, this zero-waste route to DSIDA produces a product stream that, after filtration of the catalyst, is of such high quality that no purification or waste cut is necessary for subsequent use in the manufacture of Roundup . The new technology represents a major breakthrough in the production of DSIDA, because it avoids the use of cyanide and formaldehyde, is safer to operate, produces higher overall yield, and has fewer process steps. 

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