Green chemistry metrics: Insights from case studies in fine chemical processes

This study proposes a systematic approach to evaluating green metrics in catalytic processes for fine chemical production, within the context of the growing demand for sustainable industrial chemical processes. This approach is adaptable to a wide range of chemical processes. For each fine chemical process, three recovery scenarios were analyzed, demonstrating that process sustainability improves significantly with better material recovery. The main green metrics evaluated in this study include atom economy (AE), reaction yield (ɛ), stoichiometric factor (SF), material recovery parameter (MRP), and reaction mass efficiency (RME). Radial pentagon diagrams were used as a powerful tool for graphical evaluation of all five green metrics, helping to assess the greenness of the process. The first case examined the epoxidation of R-(+)-limonene over K–Sn–H–Y-30-dealuminated zeolite, considering the mixture of epoxides (endo + exo) as the target product. The green metrics for this process were AE = 0.89, ɛ = 0.65, 1/SF = 0.71, MRP = 1.0, and RME = 0.415. The synthesis of florol via isoprenol cyclization over Sn4Y30EIM yielded metrics such as AE = 1.0, ɛ = 0.70, 1/SF = 0.33, MRP = 1.0, and RME = 0.233. Finally, the synthesis of dihydrocarvone from limonene-1,2-epoxide using the dendritic zeolite d-ZSM-5/4d exhibited excellent green characteristics (AE = 1.0, ɛ = 0.63, 1/SF = 1.0, MRP = 1.0, and RME = 0.63), making it an outstanding catalytic material for further research on biomass valorization of monoterpene epoxides.