正庚烷脱氢生成烯烃反应机理的模拟研究  

Simulation of the Reaction Mechanism of Dehydrogenation of n-Heptane to Produce Olefins

作　　者：于宁[1] 龙军[1] 周涵[1] 马爱增[1] 代振宇[1] 

机构地区：[1]中国石化石油化工科学研究院,北京100083

出　　处：《石油学报（石油加工）》2016年第3期437-443,共7页Acta Petrolei Sinica(Petroleum Processing Section)

基　　金：中国石油化工股份有限公司项目(R14056)资助

摘　　要：采用基于密度泛函理论的量子化学方法研究了催化重整过程中正庚烷脱氢生成烯烃的反应过程。通过对比2条不同的反应路径得出,Pt原子在脱氢反应中生成的Pt-H活性中心具有吸取单电子的能力,具有较强的脱除氢自由基的催化能力。反应过程中,正庚烷首先在0价态的Pt原子表面发生化学吸附,随后发生脱除氢自由基反应,生成庚基自由基和Pt-H活性中心,优先生成2-庚基自由基,最低反应能垒为75.89kJ/mol;庚基自由基直接与Pt-H催化剂活性中心发生化学吸附,进一步发生脱除氢自由基反应,生成庚烯与Pt-H_2,优先生成2-庚烯,最低反应能垒为17.52kJ/mol;最终,庚烯从Pt-H_2表面发生脱附,随后Pt-H_2发生脱附反应生成H2和再生的0价态的单Pt催化剂。该反应路径中最大反应能垒为75.89kJ/mol。实验证明,正庚烷脱氢生成正庚烯的反应过程中优先生成2-庚烯。The dehydrogenation of n-heptane to olefins in the process of catalytic reforming was studied by density functional theory(DFT)quantum chemical methods.Two different reaction approaches were compared.It is concluded that the Pt-H reactivity center yielded from the Pt atom during the dehydrogenation is capable of capturing single electron,which has the strong catalytic capability to capture H radical.During the reaction,n-heptane was first absorbed on the surface of the zero-valence Pt,and then the H radical is removed,yielding the heptyl radical and the Pt-H reactivity center.2-heptyl radical was produced with priority due to the minimum barrier energy of75.89kJ/mol.Heptyl radical is chemically absorbed to the Pt-H reactivity center directly,which loses H radical subsequently,resulting in the formation of heptane and Pt-H_2.2-Heptene is produced with priority due to the minimum barrier energy of 17.52kJ/mol.Heptane is desorbed on the surface of Pt-H_2,and H_2 and the regenerated zero-valence Pt are obtained by desorption of Pt-H_2.The maximum barrier energy of this reaction approach is 75.89kJ/mol.It is proved that heptane gives the priority to producing 2-heptene during the dehydrogenation.

关 键 词：正庚烷 烷烃脱氢 PT 反应机理 分子模拟 

分 类 号：TQ221.21[化学工程—有机化工]