正庚烷催化裂解机理模拟研究

Simulation Study on Mechanism of N-Heptane Catalytic Cracking

模拟计算了HZSM-5催化剂催化正庚烷裂解生成低碳烯烃的2种反应路径(C_(2)—H和C_(2)—C_(3)键断裂),使用密度泛函理论(DFT)方法计算不同反应过程的过渡态,并对得到的结果进行IRC扫描,验证其准确性。通过比较这2种不同反应路径,发现与C_(2)—H相比,C_(2)—C_(3)键断裂需要的活化能更低,催化裂化反应最可能优先发生质子化反应生成碳正离子过渡态,而不是脱氢反应,计算结果为催化剂设计提供了有力的理论依据。

Two reaction pathways(C_(2)—H and C_(2)—C_(3) bond broken)for the catalytic cracking of n-heptane to generate low-carbon olefins by HZSM-5 catalyst were simulated and calculated,the transition states of different reaction pathways were calculated and verified by density functional theory(DFT)method,and then by comparing the two different reaction pathways,it was found that the activation energy required for C_(2)—C_(3) bond breaking was lower than that of C_(2)—H,and it was concluded that the catalytic cracking reaction was most likely to have a protonation reaction to form carbonium,rather than a dehydrogenation reaction.The result provides a strong theoretical basis for the future design of catalysts.