Productive Process Of PMDA By Air Phase Oxidation And Its Collecting Methods By Condensing Mode

Pyromellitic acid dianhydride,also named 1,2,4,5-benzene tetracarboxylic acid dianhydride(abbreviated to PMDA),is the important material of organic synthesize industry and the essential raw material of developing the new chemical material and high odditional fine chemistry Nowadays the method of producuction of PMDA by air phase oxidation is widely used in many factories at home and abroad. In the method of air phase oxidation the mixed gas that boiling 1,2,4,5-tetramethyl benzene is combined with air is carried into oxidation reactor and reacts and then product gas is cooled.PMDA of product gas is collected by the desublimated method.By the creation of PMDA some subreactions happan and yield some partial oxidated and over oxidated byproducts.How to make gaseous PMDA be colleted effectively and be separated from mixed gas and enhance the purity of PMDA will become key process in the prouction of PMDA by air phase oxidation.The production process of PMDA in some company is reviewed covering through the operation conditions to different reactant and resultant unit.And catalytic bed volume and flow form of reaction are also described.To solve the problems that PMDA adhered to the surfaces of recipients and plug up the pipes the new condensing mode collecting PMDA process was proposed:considering high vaper heats of the condensates adding a cooling agent to the product gas mixture to cool the gas mixture and separate component in a solid state and subsquently separating components in a solid state with the cyclone equipment. And from the point of view of security explosive limit and flash point of condensing matter are analyzed and from feasibility some normal paraffin hydrocarbon is fit to become condensing matters,And three desublimation heat-exchanged equipments are designed.A intergrated desubliraating PMDA process by condensing matter is carried out.And the process is simulated by Aspen software and three parts of results are consisted as follows:1 . If the first coolant whose AvapH(160°C) is equal to 4903cal*mol-l is used therate of desublimated PMDA is above 98.42%;if PMDA that is separated from the second cyclone is added reacted gas and recycled that rate will be above 99.98%;if 100 ton of PMDA is collected 114.7077 ton of that coolant will be engaged;if 100 ton of PMDA annually is yielded 0.0229 ton of that coolant is complementary.2 . If the second coolant whose AvapH(160°C) is equal to 3534 cal#mol-l is usedand 100 ton of PMDA is collected 127.32 ton of that coolant is engaged.3 . If the third coolant whose AvapH(160°C) is equal to 6389 cal#mol-l is used and100 ton of PMDA is collected 97.81 ton of that coolant is engaged. In theory simulated results show engaging condsening matters the cost is small and the desublation of PMDA is speedly and the purity of production is high.And also producting and collecting process is continuous and annual yield obtains enhanced and energe consumption is reduced.Finnaly a sensitivity analysis war carried out for designed process .Through Aspen software analysising the optimal result was obtained.