Process Optimization Of Methyl Nitrite Regeneration And Modeling Of A Packed Column For Regeneration

The process of methyl nitrite（MN） regeneration is an important reaction in the process of producing dimethyl oxalate and also a key step in the industrialized production of dimethyl oxalate. But it is a complex process, some by-products including nitric acid and nitrous acid can be produced except for MN. In order to improve the yield of MN and reduce the by-products, the process of regeneration need to be studied and optimized.The process of MN regeneration reaction was studied in a packed bubble column reactor. The optimum operating conditions were determined as: reaction temperature 35⁴5℃, NO/O₂ mole ratio 5⁶, quantity of methanol 40 m L, gas flow rate 450 500 m L/min, N2 volume fraction 70 80%.The MN yield can reach 90.3% under the optimum operating conditions. The effect of CO₂ on regeneration was also studied in a packed bubble column reactor at different conditions and the results showed that the presence of CO₂ had no effect on regeneration reaction.In the packed bubble column reactor, the amount of methanol is much higher than the stoichiometric amount and its concentration will decrease along with reaction time. So the separation process was needed to purify methanol. In order to make the methanol usage in line with the stoichiometric ratio, the process of MN regeneration reaction was studied in a gas phase reactor and the optimum operating conditions were determined as: reaction temperature 70℃, NO/O₂ mole ratio 5⁶, NO/methanol mole ratio 1, gas flow rate 400⁴50 mL/min, N2 volume fraction 70 75%. The MN yield can reach 84.21% under the optimum operating conditions. Compared with the packed bubble column reactor, MN regeneration in a gas phase reactor is more close to stoichiometric reaction, reducing the energy consumption of the subsequent separation process. But its disadvantage is lower MN yield and higher reaction temperature.On the basis of previous research work, a mathematic model of the MN regeneration was developed in a packed column with the reported kinetic parameters. The simulated results were compared with experimental, maximum relative deviation of MN yield was-4.39% and O₂ conversion was-8.15%, which proved that this model could be used for the design and operation of the process of MN regeneration.In order to convert the unreacted methanol and the by-product of nitric acid from MN regeneration, the process for synthesis of MN by reaction of NO, HNO₃ and CH₃ OH was stduied. The thermodynamics of the process was analyzed. Through the experiment in a packed bubble column reactor, the optimum operating conditions were determined as: methanol concentration 85%, nitric acid concentration 10%, gas velocity 100³00 mL/min, NO volume fraction 10⁴0% and reaction temperature 30⁵0℃.The NO conversion and MN yield can reach 91.7% and 71.9% under the optimum operating conditions.