High-Flux Continuous-Flow Synthesis of C.I. Pigment Yellow 12 from Clear Alkaline Solutions of the Coupling Component
writer：Zhiping Shi, Xudong Wang, Defei Yin, Wei Li, Dongzhi Liu, Xueqin Zhou
keywords：C.I. Pigment Yellow 12, continuous process, azo-coupling reaction, process intensification
source：期刊
specific source：Organic Process Research & Development
Issue time：2021年
In this study, a continuous-flow azo-coupling reaction for the synthesis of C.I. Pigment Yellow 12 (PY12), a common commercial azo pigment, was developed using an impinging mixer at high fluxes. The coupling component was pumped into the mixer as a clear alkaline aqueous solution to overcome the blocking issue from unexpected big particles during a long-time running. It was revealed that the local pH at the azo-coupling reaction center could be precisely regulated with negligible variation over time by the addition of sodium acetate. Fast heat transfer resulted in no accumulation of heat in the mixer together with the following delay loop reactor. The acetoacetaniline solution temperature, reactant flux, and post-treatment temperature were optimized. The flux can reach 40 L/h. PY12 with a hue similar to that of commercial batch products could be achieved with a yield above 98%. Furthermore, the PY12 samples exhibited transparency and tinting strength higher than those of the commercial batch products. In comparison with the batch process, the continuous-flow process presented in this work displays advantages of decreased energy consumption, a reduced amount of wastewater, as well as chemical oxygen demand of wastewater, showing great potential for industrial production.