沥青质分子支链及桥链断裂行为的模拟计算

Simulated Calculation on the Cracking Behavior of Branch Chain and Bridge Chain of Asphaltene Molecule

用分子模拟方法对含有支链的大陆型沥青质分子和群岛型沥青质分子的断裂位置及断键规律进行研究,并对支链断裂反应进行了热力学计算。结果表明:对于大陆型沥青质分子,其支链断裂的位置均在β位,支链小于3个碳原子时,C—C键较难断裂,支链越长越容易断裂;从热力学上看,大陆型沥青质分子支链断裂的转化率较高,断键反应没有障碍,反应的深度由动力学条件来控制;对于群岛型沥青质分子,其断键位置在稠环芳烃数较多片断的β位容易断裂,当链段小于3个碳原子时,C—C桥键很难断裂,桥链越长断裂的活化能越低,越容易断裂。对于C—S桥键,其断裂的活化能比C—C桥键的低,断裂相对容易。

The cracking positions and bond breaking laws of continental and archipelagic asphaltenes molecules with branch chains were studied using the molecular simulation method,and the thermodynamics of branch chain cracking was calculated.The results indicate that for continental asphaltene molecules,the branch chain cracking position is atβsite;when the branch chain is less than three carbon atoms,the C—C bond is difficult to break;the longer the branch chain,the easier it is to break.In terms of thermodynamics,the conversion rate of branch chain cracking for continental asphaltene molecules is high,there is no obstacle to bond breaking reactions,and the depth of reaction is controlled by kinetic conditions.For archipelagic asphaltene molecules,the bond breaking position is atβsite with a number of polycyclic aromatic hydrocarbons,so they are easy to break.When the chain segment is less than three carbon atoms,the C—C bridge bond is difficult to crack.The longer the bridge chain,the lower the activation energy of bond breaking,and the easier it is to break.For C—S bridge bond,the activation energy of bond breaking is lower than that of C—C bridge bond,so the cracking is easier.