The Study on Synthesis Process of p-Phenylene Diamine

p-Phenylene diamine is the simplest aromatic diamines and widely used in preparing chemical products like dyes, resins, rubber antioxidants, etc. Currently in industry, p-phenylene diamine is mainly synthesized via the fine chemical route, that is, reducing p-nitroaniline by iron powder under acidic condition, with severe pollution. Moreover, the high price of p-nitroaniline is also annoying.

To obtain p-phenylene diamine more economically and more eco-friendly, we used a petrochemical route. Thus, terephthalic acid was employed as the raw material, p-phenylene diamine was prepared through esterification, ammoniation, and electrochemically-induced Huffman rearrangement (see Figure 1). In this process, the only by-products are water, sodium carbonate and alcohol. Especially, the emission of large amount of sodium chloride and waste water during the traditional Huffman rearrangement process was overcome by the electrochemical approach.

The total yield of this route amounts to over 80%.