甲烷在钯基催化剂上脱氢的分子模拟

Molecular simulation of methane dehydrogenation on Pd-based catalysts

关键词:  甲烷脱氢  密度泛函理论  钯基催化剂  二聚体催化剂

Key words:  methane dehydrogenation  density functional theory  Pd-based catalyst  dimer catalyst

摘要:

为探明甲烷在钯基二聚体催化剂上脱氢反应过程的微观机理,对甲烷燃烧催化剂的设计与使用提供指导。在M06L/6-311++G(d,p)+SDD//M06L/6-311G(d,p)+LANL2DZ基组水平上,采用密度泛函理论(DFT)对甲烷在钯基二聚体催化剂(Pd₂、PdPt和PdNi)上的脱氢过程进行了研究。对比了甲烷在催化剂Pd₂、PdPt和PdNi上反应的能垒(E_b)、活化能(E_a)及反应速率常数(k),结果表明:CH₂→CH是甲烷在二聚体Pd₂反应的速率控制步骤(RDS),而CH₃→CH₂是催化剂PdPt和PdNi反应的RDS；钯基二聚体催化剂对甲烷脱氢的催化活性顺序为PdPt＞Pd₂＞PdNi；抗积炭性能顺序为PdNi＞Pd₂＞PdPt。PdPt适用于要求催化效率较高的项目,而抗积炭性能较好的PdNi催化剂可用于大型工业催化。 

Abstract:

The study of the mechanism of methane dehydrogenation on Pd-based dimer catalyst can provide a guidance for the design and selection of catalyst on methane combustion. The processes of methane dehydrogenation on three Pd-based dimer catalysts (Pd₂, PdPt and PdNi) are investigated using the density functional theory (DFT) calculation under the M06L/6-311++G(d,p)+SDD//M06L/6-311G(d,p)+LANL2DZ level. The energy barrier (E_b), activation energy (E_a), and reaction rate constant (k) of methane dehydrogenation on Pd₂, PdPt and PdNi are compared. The results indicate that CH₂→CH is the rate-determining step (RDS) for methane dehydrogenation on dimer Pd₂, while CH₃→CH₂ is the RDS on PdPt and PdNi; the catalytic activity for methane dehydrogenation on Pd-based dimer catalyst follows the order of PdPt > Pd₂ > PdNi; the anti-carbon performance follows the order of PdNi > Pd₂ > PdPt. PdPt is suitable for those cases requiring higher catalytic efficiency, while PdNi catalyst is suitable for large-scale industrial production due to the good anti-carbon property.