Preparation method of dimethyl-biphenyl diisocyanate

The invention relates to a preparation method of dimethyl-biphenyl diisocyanate. The method comprises the steps that firstly, a catalyst polyoxometallate and a solvent are added into a reaction vessel, then raw materials ortho-tolidine, phenylsilane, an acid binding agent and a dehydrating agent are added and uniformly mixed together, finally, gaseous carbon dioxide is added, and magnetic stirringis conducted at a certain temperature for a full reaction to obtain the product. According to the method, M-Anderson-type heteropoly acid is adopted as the catalyst, the catalyst requires mild reaction conditions and is high in specific selectivity, recyclable and environmentally friendly, the cleanliness of the industrial reaction is improved, the economical efficiency of the process is improved, the manufacturing cost and the production of three wastes are reduced, the environmental protection pressure is relieved, and industrial production is facilitated. 本发明涉及一种二甲基联苯二异氰酸酯的制备方法，先将催化剂多金属氧酸盐、溶剂加入反应容器，再加入原料联邻甲苯胺以及苯硅烷