Process for preparing butyl isocyanate

The invention discloses a Method for preparation of butylisocyanate, using n-butylamine as raw materal, dimethylbenzene as dissolvant, reacting with excess carbonyl chloride, getting the product which the purity is higher than 99% after two steps photo aerification reaction of low-temperature, high-temperature and distillation. Adopting two steps photo aerification reaction of low-temperature, high-temperature can reduce occurrence of secondary reaction effectly. In n-butylamine terms, the total yield of this invention is more than 95%.