How does aniline react with HNO3 in the absence of sulfuric acid?
In the absence of sulfuric acid, aniline does react with nitric acid to form anilinium nitrate. It is observed as an intermediate product during the production of diazobenzene nitrate (benzenediazonium nitrate). But the species is too unstable for mass production and cannot be stored for long hours. Here is the description:


  
  
  20 g of aniline are placed in a beaker, well cooled, and “boiled-out”
  nitric acid, previously diluted with half its volume of water,
  carefully added till the mixture sets to a thick crystalline paste –
  aniline nitrate.[...]


Caution: The synthesis is not to be carried out due to high explosive nature of diazobenzene nitrate. Explode in dry state.