Preparation process of high-purity methacrylonitrile

The invention discloses a preparation process of high-purity methacrylonitrile. The preparation method of the high-purity methacrylonitrile comprises the following steps: S1, preparing a catalyst; step S2, preparing methallyl alcohol into methacrylonitrile through an ammonia oxidation process, filling the catalyst obtained in the step S1 into a reaction tube for reaction under the reaction conditions that the temperature is 417-435 DEG C, the pressure is normal, the composition ratio of isobutene to ammonia gas to air to water vapor is 5: 6: 48: 15, the unit is mL/min, heating the raw materials isoethylene, ammonia gas and air, feeding the heated raw materials and the water vapor into a reactor, and reacting for 2-4 hours; the method comprises the following steps: carrying out an ammoxidation reaction in a reactor under the action of a catalyst, cooling the reacted gas in a quench tower, removing liquid ammonia flowing out of the reaction, and cooling the reacted material to 40 DEG C or below to obtain a meth