Preparation of Salicylic Nitrile through Direct Catalytic Dehydration ofSalicylamide with Immobilized Phosphoric Acid as Catalyst

Salicylic nitrile was prepared through direct catalytic dehydration of salicylamide under high temperature using immobilized phosphoric acid as catalyst. The catalytic performances of different catalysts were evaluated according to the analytic results of GC-MS, and the feasibility about the preparation of salicylic nitrile by direct catalytic dehydration of salicylamide was investigated according to the composition of product determinated by GC analysis (area nomalization). Experimental results indicated the comprehensive property of silica gel supported phosphoric acid was the best one among all of the catalysts utilized in this study. When the temperature of catalyst bed was 480 ± 10º and silica gel supported phosphoric acid was utilized as catalyst, the conversion ratio of salicylamide was 88.79%, the selectivity to salicylic nitrile was 97.97% and the yields of salicylic nitrile could up to 86.99%. Meanwhile, the experimental results showed the increase of temperature of catalyst bed could result in the increase of the conversation of salicylamide, but much more by-product could be formed when the temperature of catalyst bed was too high.