There are four main production methods of trimeric anhydride: trimitylene liquid phase air oxidation method (MC method), trimitylene liquid phase nitric acid oxidation method, trimitylene gaseous phase air oxidation method and m-xylene formaldehyde liquid phase air oxidation method (MGC method), of which trimitylene liquid phase air oxidation method is the mainstream production method in the world, accounting for about 96% of the global industrial equipment. Trimethylbenzene liquid phase air oxidation method is currently widely used partial anhydride production process, the process was first developed by the Middle Ages (Mid-century) company in the United States, called MC method, is based on trimethylbenzene as raw material, acetic acid as a solvent, with air as an oxidizer, the trimethylbenzene oxidation to trimeric acid, trimeric acid and then dehydration to produce trimeric anhydride. The method has the advantages of easy availability of raw materials, low consumption of raw materials and public works, small corrosion and easy solution to the "three wastes" problem, but it also has the disadvantages of large equipment investment, difficult to recover acetic acid and difficult to remove trace bromine ions in the product. The vapour-phase air oxidation of tritylene was developed by the Japanese Catalyst Chemical Industry Co., Ltd. in the 1970s, using compounds containing vanadium, titanium and phosphorus as catalysts to oxidize tritylene to trimeric acid, which was then dehydrated to produce trimeric anhydride. There is no corrosive medium in the oxidation process, normal pressure operation, most of the equipment can be processed by ordinary carbon steel, which greatly reduces the investment of equipment. However, it also has the disadvantages of poor catalyst selectivity and low yield, so it has no industrial application. Tritylene liquid phase nitric acid oxidation method developed by Saarbergwerk company in Germany in the 1970s and achieved industrial production, is to add tritylene to dilute nitric acid solution for oxidation reaction, after separation and drying crystallization to obtain tritylene. The process is simple, easy to operate, high yield, yield up to 90%, product purity can reach 98.5%, but the method has serious corrosion to the equipment, high material requirements of the equipment, high production cost. The liquid phase air oxidation process of m-xylene formaldehyde was developed by Mitsubishi Gas Chemical Company in Japan in 1985. It is a new process of preparing aromatic aldehyde with m-xylene as raw material and then using water as solvent to oxidize trimeric anhydride with air liquid phase. The advantages of this method are low raw material cost and easy to obtain, continuous reaction process and automatic control. However, it also has the disadvantages of serious corrosion of the equipment and the use of precious metal catalysts. In the global production enterprises, only Japan's Mitsubishi Gas Chemical Company 15,000 tons/year device adopts m-dimethylbenzaldehyde liquid phase air oxidation method, and the rest of the production enterprises all use the tri-toluene liquid phase air oxidation method.