Numerical Simulation Of Free Radical Reactions Mechanism Of N-pentane Thermal Cracking

Ethylene is an important basic raw material for the production of three synthetic materials and organic chemical products.The demand for ethylene increased year by year because of the rapid development of petrochemical industry that leads to the shortage of raw material.Raw material optimization problems have become increasingly prominent.The evaluation can be performed with the use of a small experimental device which is not suitable for diversified development trend of raw materials.With the development of computer techology and sofeware,numerical simulation has become an important scientific research methods except of experimental research.The pyrolysis kinetics model has a great influnce on the accuracy of numerical simulation.Hydrocarbon steam thermal cracking is the main process of ethylene production.Due to the characteristics of free radicals reaction of thermal cracking,so far,the progress of experimental study on free radical mechanism of single hydrocarbon molecules is very slow.In this paper,a new method useing molecular simulation technique and one-dimensional mathematical model was propsed to study free radical mechanism of single hydrocarbon molecule thermal cracking.The mechanism of n-pentane thermal cracking was studied with this new method.According to the research results,a total of 25 radical reactions may occur in the themal cracking of n-pentane.14 radical reactions were decided to be the main ones according to the calculation of one-dimission model.The 14 main reactions are composed of three chain of circular reaction which caused by hydrogen,methyl and ethyl radical taking hydrogen atom from n-pentane.Ethyl radical is the main hydrogen atom abstraction radical because of the shortest length of chain propagation occurred between ethyl radicl and n-pentane with production of C2H6 and C3H6.Methyl is secondary hydrogen atom abstraction radical because of less reaction steps with production of CH4 and C2H4.Hydrogen is the weakest hydrogen atom abstraction radical with production of H2 and 2-C5H10 because hydrogen radical is generated from decomposition of 1-C3H7· and generation of 3-C5H11·from hydrogen abstraction reaction of CH3·.According to the study of free redial mechasim of n-pentane thermal cracking,the study of free radical mechanism of hydrocarbon thermal cracking can be speeded up with the new theoretical method propsed in this paper.Accuracy requirement of dynamic model to the numerical simulation can be solved on the premise of saving manpower and financial resources.