Cleaner production technology of intermediate DAS in red pigment C.I.177: four-phase heterogeneous catalytic Ullmann condensation

Abstract

The pursuit of cleaner production of pigments is an urgent need. Therefore, in this work, a cleaner production method of 4,4′-diamino-1,1′-bianthraquinone-3,3′-disulfonic acid (DAS), a key intermediate of C.I. Pigment Red 177, was explored. This study employed potent acid cation exchange resin in place of sulfuric acid, significantly diminishing the solvent quantity. Utilizing the semidissolved bromamine acid sodium salt as a ‘reactant storage,’ it gradually disintegrated and engaged in the reaction, creating a ‘resin–copper–bromamine acid sodium salt–solution’ with a four-phase heterogeneous catalytic system, leading to more efficient DAS production. Given a reaction temperature of 60°C, a duration of 90 min, and dosages of resin and copper powder at 20 g/L and 15 g/L, the output can achieve 93.21%. Concurrently, solid acid offers the advantage of being reusable and straightforward to separate. Following its removal, products can be directly acquired via multieffect evaporation, thereby preventing the generation of high-salt wastewater that typically accompanies the salting-out process. Furthermore, the temperature of the reaction is 15°C cooler compared to the classical approach, enabling the utilization of inferior natural thermal sources like solar power. Employing this cutting-edge technique lessens the release of high-salt wastewater from the origin and simplifies its treatment, promising significant advantages in product yield, ecological conservation, resource conservation, and energy consumption.