(208d) Environmentally Sustainable Process for Synthesis of Para Amino Phenol & Its Techno-Economic Benefits over the Conventional Process

Para Amino Phenol (PAP) is considered to be one of the most important active pharmaceutical ingredients and a prime precursor of paracetamol. Approximately 80% of the global PAP production is utilized in the production of paracetamol which is a widely prescribed analgesic and antipyretic. Another 7% serves as rubber antioxidants, while the remaining 13% finds application in dyes and other miscellaneous uses. Currently, the global production of PAP stands at approximately 180-190 Kilo Tons Per Annum (KTPA). The global market for Para Amino Phenol (PAP) was valued at 442.6 million USD in 2020 and is projected to reach 553.1 million USD by 2026, with a Compound Annual Growth Rate (CAGR) of 3.2% from 2021 to 2026. The key PAP demand centers are China and India with 49 KTPA and 38.5 KTPA respectively. China has an installed capacity of 100 KTPA PAP and is considered the market leader accounting for over 60% of the global production. Traditionally, PAP has been produced through the reduction of p-nitrophenol using iron powder. This method involves the conversion of p-nitro chlorobenzene (PNCB) to p-nitrophenol, followed by its reduction to PAP. However, this process yields a low percentage of PAP, generates significant amounts of iron sludge and wastewater with chlorinated substances, and poses serious environmental concerns. Consequently, this method has been phased out in many developed countries. An alternative approach involves the hydrogenation reduction of p-nitrophenol using a Raney-Nickel catalyst. This method offers improved yield, fewer by-products, and reduced environmental impact compared to the traditional iron powder reduction. Nonetheless, it still presents the risk of environmental pollution due to the disposal of effluents contaminated with chlorine-based compounds, primarily p-Chloro Aniline (PCA). In light of environmental sustainability, a novel synthesis process using nitrobenzene as the raw material has emerged as a favorable alternative. This method employs catalytic hydrogenation of nitrobenzene in the presence of a Platinum-Carbon catalyst. It offers a shorter, compact, and streamlined process route along with approximately 25% lower power consumption compared to the conventional PNCB route and ensures a satisfactory yield of PAP (above 83%) relative to the nitrobenzene feedstock. Additionally, it produces value-added by-products such as Aniline and Ammonium Sulphate and ensures a high-quality product equivalent to pharmaceutical grade. Importantly, this approach eliminates the release of hazardous chlorinated compounds in effluents, thereby reducing environmental risks. A minor aqueous effluent is generated in this process, containing a low concentration (approximately 5%) of Ammonium Sulphate, which can be effectively treated before disposal. The production of PAP via catalytic reduction of nitrobenzene offers cost advantages, with approximately 30% lower conversion costs and 20% reduced capital investment compared to the conventional PNCB route. This environmentally sustainable method, when implemented on a commercial scale with a capacity of 50 to 60 KTPA, yields over 80% higher Earnings Before Interest, Taxes, Depreciation, and Amortization (EBITDA) and more than 30% increased Internal Rate of Return (IRR) compared to the conventional route over a plant lifecycle of 15 to 20 years. Considering the advantages from techno-economic and environmental aspects, this emerging route can be regarded as the future direction of PAP production. Our study provides a comprehensive comparative analysis, highlighting the advantages of this emerging approach over traditional method from both techno-commercial and environmental sustainability perspectives.