Simulation Of M-xylene And Ethylbenzene Co-Oxidation Process

Purified isophthalic acid(PIA).a widely used organic chemical intermediate,is mainly produced by liquid phase oxidation of meta-xylene(MX).Due to the high cost of separating the raw material MX,production of PIA in China is limited.Compared with the traditional pure MX oxidation process,the co-oxidation of MX and ethylbenzene(EB)is a more promising technology to produce PIA.The raw material of co-oxidation is the raffinate obtained from PX absorption units,after removing o-xylene(OX)by a rectification operation,a mixture of MX and EB is obtained for co-oxidation,and their oxidation product,isophthalic acid(IA)and benzoic acid(BA),was separated on the basis of solubility difference.The advantage of this technology is that its raw material is widely available,and the separation cost is so cheap that it has great market competitiveness.In this paper,the whole process design and simulation of co-oxidation technology was carried out,which provided theoretical guidance for the industrialization of this technology.The specific contents included the following aspects:(1)The distillation process simulation of the raw material separation unit was carried out,and the three-tower process was proposed,including delighting distillation column,OX rectification column,OX purification tower.Their technology parameters were optimized and the key tower equipment was designed.Energy optimization utilization scheme was proposed,such as making oxidation reaction heat be the heat source of distillation,and adopted the differential pressure heat coupling operation mode.The energy consumption was minimized after heat integration,and the separation cost was reduced observably.(2)The kinetics of MX-EB co-oxidation was regressed to obtain a hyperbolic kinetic equation,and reactor simulation was carried out by Aspen Custom Modeler The accelerated effect of EB on MX oxidation was studied,and simulation results showed that the introduction of EB would increase MX conversion and IA yield,while decreasing reaction pressure and the concentration of 3-CBA.On this basis,the effects of various process conditions on the reaction results were investigated,and the technical proposal of separating IA by crystallization and filtration unit operation was studied.(3)The mother liquor separation and recovery process was proposed.The effects of various process parameters involved in mother liquor evaporation,NPA extraction and benzoic acid refining on the recovery of useful materials such as IA,solvent,catalyst and benzoic acid were investigated,and the key tower equipment was calculated based on this.(4)The whole oxidation process for producing PIA was modeled and calculated through Aspen Plus,and the process material and energy balance data was obtained.The simulation results showed that the key technical indicators could meet the expected design requirements...