Green and Low-Cost Synthesis of Thermally Stable Cation-Exchange Resin-Supported Diazonium Salt: An Example of Weakly Basic p-Nitroaniline Diazotization

Wide applications of diazonium salts (DS) are limited due to their nature of poor thermal stability and explosive hazards. In this work, strong acid cation-exchange resin (Amberlyst-15), as an acid and anion provider, was used to synthesize the corresponding diazonium salt of weakly basic p-nitroaniline (p-NA). The thermal stability of raw materials (p-nitroaniline, Amberlyst 15) and cation-exchange resin-supported DS (CER-supported DS) was characterized by DSC and ARC, respectively. The synthesis conditions were optimized, and the exothermicity of the diazotization reaction was characterized by reaction calorimetry. Diazonium salts of p-NA were demonstrated to be obtained and chemisorbed on the cation-exchange resin surface. The optimal yield of CER-supported DS reached up to 80%. The initial decomposition temperature and decomposition energy of the CER-supported DS were about 55 °C and 183 J/g, respectively. The decomposition process of the CER-supported DS followed a single n-order reaction model, and the main decomposition product was p-nitrophenol. The merits of this synthesis method include being free of environmentally harmful inorganic acids and high-cost of tert-butyl nitrites and having good storage stability.