Kinetics Of Propylene Polymerization Catalyzed By Confined Geometry Metallocene

Polypropylene material is a rapidly developing thermoplastic synthetic resin.With its advantages of low density,non-toxicity,easy processing and molding,and excellent mechanical properties,it has penetrated into various areas of people's lives,including travel,household and production such as household appliances,The automobile industry,construction industry.Also contributed to polypropylene becoming country's second largest consumer product.As country's energy structure mainly includes coal,oil and natural gas,because of the continuous consumption and large-scale use of energy,country's energy structure needs to be optimized,and the demand for the polypropylene industry has accumulated.Compared with the previous oil demand,the polypropylene market and its products are now more competitive,which is not only conducive to the efficient use of energy but also conducive to the sustainable development of the ecological environment.In order to reduce the production cost of polypropylene products and improve their quality and performance,major companies seek breakthroughs through mergers,unions and reorganizations,while constantly improving their polypropylene production technology.In this paper,the metallocene catalyst system[Me₂Si(Me₄Cp)(N^tBu)]TiCl₂/MAO was used to catalyze the polymerization of propylene,and the polymerization kinetics under different reaction conditions(such as polymerization temperature,Al/Ti molar ratio and monomer concentration)were studied.By designing a constant pressure-monomer compensation method polymerization device to determine the monomer concentration,the GPC measurement result shows that the molecular weight distribution of polypropylene is very close to 2,which proves that it is consistent with the single-site polymerization mechanism.By calculating and comparing the data,we find that the polymerization reaction is a first-order deactivation reaction,and the polymerization reaction rate is a first-order reaction for both the monomer concentration and the catalyst concentration.The fourth-order Runge-Kutta method was used to estimate the kinetic parameters,and the model search algorithm was used to optimize the model parameters.The experimental results showed that the predicted value of the model was close to the experimental data,and the overall relative error for the polymer output was about 6.14%,The average error of the mass average molecular weight is4.31%,and the average relative error of the number average molecular weight is 3.82%,showing that the model has good applicability to the different polymerization conditions of the reaction system.Through this model,parameters such as polymerization rate,number average molecular weight and mass average molecular weight can be predicted,and the relationship between chain initiation,chain lengthening,chain transfer and chain termination rate and product properties can be quantitatively analyzed.I completed the model shows that the chain initiation process within 0.02?0.07 min.Compared with the chain transfer reaction,the chain extension reaction has a lower activation energy.The increase in temperature is conducive to the progress of the chain transfer reaction,generating low molecular weight polymers.The effects of different polymerization temperature,Al/Ti molar ratio and monomer concentration on the polymerization reaction system and polymer molecular weight were explored.Combined with the artificial intelligence method,the artificial neural network model is used to model the polymerization reaction,and we compare the prediction model curve with the experimental value and we judge the robustness.The average molecular weight of the polymer and the AARD%of the catalyst activity predicted by the model are 3.76%and 5.89%.We can use artificial intelligence to quickly,efficiently and accurately establish a kinetic model to speed up the industrial simulation and application of metallocene catalysts.