Method for capturing and purifying pyromellitic dianhydride

The invention discloses a method for capturing and purifying pyromellitic dianhydride. The method comprises the following steps of: directly performing heat exchange on a gas-phase product prepared from durene through gas-phase catalytic oxidation twice, introducing into a capture device, exchanging heat between air and the reaction product, making the gas-phase reaction product pass through the inside of the capture device and cooling air pass through a jacket layer of the capture device, separating out the pyromellitic dianhydride and byproducts from the gas-phase reaction product through heat exchange and cooling, and finally obtaining high-purity pyromellitic dianhydride. By the method, the pyromellitic dianhydride and the byproducts in the gas-phase reaction product prepared from the durene through a fixed bed gas-phase catalytic oxidation process are effectively separated, the high-purity pyromellitic dianhydride can be continuously and efficiently captured directly, and the method has the advantages th