Greening Fine Chemical Production via Continuous Flow Technology: An LCA-TEA-SA Integrated Assessment of <i>p</i> -Nitrobenzoic Acid

The fine chemical industry is reevaluating its traditional manufacturing paradigms, moving toward greener, safer processes and cost-effective practices. Continuous flow technology (CFT) stands out among emerging methodologies due to its superior performance and significant commercial potential, but it still lacks comprehensive environment-economy-safety trade-off assessments and the exploration of optimal scale-up pathways. To address the gap, we developed a model by integrating green chemistry efficiency assessments, life cycle environment-economy-safety evaluations, and scale effects. The model was employed to the oxidation of p-nitrotoluene to p-nitrobenzoic acid based on commercialized-scale production. We assessed the traditional batch-wise technology (BWT) and emerging continuous flow technology to elucidate the environment-economy-safety trade-off and scale effects. The key findings include the following: (1) CFT outperformed BWT with a 16.91% reduction in 100 year global warming potential, a 13.73% decrease in capital and operating expense, and a 1.5% improvement in overall safety score under real production conditions. (2) A trade-off model identified 154–160 °C as an optimal window where CFT excelled in environment-economy-temperature safety performance. As temperature rose, CFT showed decreasing unit emissions and cost. (3) At scales above 2385 tons/year, CFT could become more cost-effective than BWT. CFT consistently outperforms BWT across all production scales in terms of both environmental performance and economic scalability. The volumetric expansion of BWT proved to be a more sustainable scale-up route than numbering-up. This study can offer insights into the transformation toward sustainable fine chemical production practices.