Kinetics Research And Simulation Of The Reactor On Reaction Of CO And Methyl Nitrite Catalytic To Dimethyl Oxalate

Gas phase coupling of CO into dimethyl oxalate(DMO)is a key technology in the process route for ethylene glycol production from coal-based syngas.The technique is the synthesis of DMO on supported palladium catalysts by the catalytic coupling of gas-phase CO with methyl nitrite(MN).The coupling reaction is a strong exothermic reaction,which easily cause the runaway temperature phenomenon in the carbonylation reactor,and constrain the development of large-scale carbonylation reactors.The study taken experimental methods and numerical simulation method.Coupling reaction laboratory test.and amplification experiments are studied systematically,which can provide some basic theoretical guidance for the industrial application of DMO.The main research contents are as follows:Firstly,the catalytic activity of the catalyst is strong and the force between the active component and the support is weak.The conversion of MN was 84%and the selectivity of DMO was 97%.The coupling reaction characteristics of CO coupling to DMO over the catalyst were investigated.In the temperature range of 383.15～393.15 K,with the increase of temperature,the coupling reaction rate increases,the side reaction enhances and the DMO selectivity decreases.In the space velocity range of 2000～3300 h-1,the space velocity has little effect on the coupling reaction.Kinetic experiments were carried out in a tubular fixed bed reactor.The experimental data are fitted and optimized by Runge Kutta method and simplex method.The power function kinetic equations at CO/MN=1.50～2.50,373.15～398.15 K and 0.10～0.20 MPa were obtained.Secondly,thermodynamic analysis of the coupling reaction system was carried out by Benson’s group contribution method and modified Rihani-Doraiswamy method.At 393.15 K,the DMO reaction enthalpy is-198.81 kJ/mol,the DMC reaction enthalpy is-54.68 kJ/mol.The relationship between the isobaric heat capacities of DMO and DMC and temperature is obtained.The 3000 t/a tubular carbonylation reactor and radial carbonylation reactor were designed.Based on the coupling reaction kinetics,mass transfer,momentum transfer and heat transfer principles,a three-dimensional quasi homogeneous model of carbonylation reactor was established.Thirdly,the tubular carbonylation reactor and radial carbonylation reactor under typical conditions were simulated by finite element calculations.The flow field distribution in carbonylation reactor was studied.The hot spot temperature area,main reaction area,pressure drop and flow direction of carbonylation reactor were determined.In the tubular carbonylation reactor:the hot spot temperature is 410.19 K,which is located in the middle and lower part of the reactor,away from the entrance of the heat transfer medium;the upper part of the reactor is the main reaction area;the gradient of pressure drop is distributed uniformly along the reaction tube;the main part of the reaction gas flows along the axial direction of the reaction tube,but there is a weak radial flow in the reaction tube;due to the complex flow state of the heat transfer medium in the shell side of the reactor,the temperature distribution in the reactor is uneven.In the radial carbonylation reactor,the hot spot temperature is 409.54 K,which is located in the inner side of the upper bed near the center of the radial bed.The reaction rate inside the catalyst bed is faster.The pressure loss of reaction gas decreases along the radial direction,and there is no obvious pressure change along the axial direction.The boundary layer separation occurs when the reaction gas flows through the wall of the heat pipe,which makes the reaction fluid converge in the radial direction.Finally,by analyzing the simulation data of carbonylation reactor and investigating the influence of feed gas temperature and feed gas composition on the reactor,it is concluded that the uniform distribution degree of bed temperature in radial carbonylation reactor is better than that in tubular carbonylation reactor under typical conditions.The pressure drop of radial carbonylation reactor(250 Pa)is much lower than that of tubular carbonylation reactor(44751 Pa).It is confirmed that the feed gas temperature has more significant effect on the hot spot temperature and MN conversion in the reactor.