This is very difficult to answer as it depends on what type of halogenoalkane you're looking at. If it's symmetrical then you use Sodium Hydroxide and this will reduce the halogenoalkane giving water and the alkene. If it's not symmetrical it's the same Sodium Hydroxide but you have a possibility of two answers depending on where the Hydrogen is removed. To answer the question this is neither reflux nor is it distillation, it is elimination.