Molecular Dynamics Simulation Of Pyrolysis Process Of Indonesian Oil Sand Bitumen

Oil sand bitumen is an important hydrocarbon organic substance in oil sands.It is a good alternative energy source for petroleum.Due to the immature mining and refining technology,the development and utilization of oil sand bitumen is restricted.In order to firrther grasp the internal structure and pyrolysis process of oil sand bitumen,the combination of experimental data analysis and molecular dynamics simulation is used to explore the nolecular structure of oil sand bitumen,and the optimal molecular model of oil sand bitumen is established and carried out.Through the simulation of the pyrolysis process,the reaction path with the lowest energy barrier in this process is found.Based on the changes in the internal structure of oil sand bitumen during pyrolysis,the internal changes of organic matter during pyrolysis are explained at the molecular level,which provides relevant theoretical basis for the preparation and comprehensive utilization of oil sand pyrolysis oil.This article mainly conducts research from the following aspects:The TG-FTIR experiments and solid infrared experiments are carried out on oil sands.The data of gas infrared and solid semi-coke infrared changes during the pyrolysis of oil sands are collected.The analysis of the obtained data reveal that the decomposition of oil sand bitumen is in the middle temperature.In the infrared spectrum,the characteristic peaks of the aromatic ring and the fatty chain are the most obvious,followed by the characteristic peaks of the oxygen-containing flunctional group,which are found to be ruainly alcoholic hydroxyl groups,phenolic hydroxyl groups,and intermolecular hydrogen bonds through peak fitting.By further fitting the characteristic peaks of aromatic rings,it is found that the aromatic rings in oil sand bitumen are mainly five-substituted aromatic rings.The characteristic peaks of each frequency spectrum band at each temperature are divided into peaks to obtain infrared structural parameters.The structural parameters show that although the hydrogen bonds between heteroatoms and molecules are not obvious in the spectrum,they play a key role in the pyrolysis process.Infrared structural parameter analysis show that with increasing temperature,the oxygen-containing functional groups and fatty chains of oil sand bitumen gradually decomposed and fell off,the degree of aromatization is further deepened,and the aromatic ring side chain and substituents gradually fell off.By fitting the 13C nuclear magnetic data spectrum of oil sand bitumen to obtain the position and peak area size of each fitted peak,consult relevant data and perform data calculation to obtain the proportion of carbon atoms in each chemical environment,through elemental analysis The data is obtained as a molecular proportional formula,and the functional group obtained by infrared analysis is inserted to obtain a preliminary two-dimensional molecular model.Subsequently,the molecular model is adjusted continuously until the structure of the model NMR spectrum consistent with the experimental NMR is obtained.Finally,the model structure is imported irito Material Studios software,the concept of grid is introduced,and the best molecular model of oil sand bitumen is obtained through molecular dynamics simulation.Through analysis of molecular model bond length,bond level and electron density,it is found that heteroatoms have higher reactivity,and bonds are more likely to break during pyrolysis.At the same time,molecular orbital analysis determines the location where chemical reactions are more likely to occur.For the molecular fragments most likely to be formed during the pyrolysis process,the TS search plate in the Dmol3 module is used for reaction energy barrier calculation and path analysis.Compared with dibenzthiophene,thiophene and carbazole have a high reaction energy barrier and are not likely to occur.Chemical reaction;the reaction energy barriers of Pathl and Path2 in the ethylsulfane fragment are less than Path3 and Path4,indicating that the connection mode of sulfur and fatty chain is more stable than that of sulfur and aromatic ring.