A DFT Study of Neopentane Hydrogenolysis and Isomerization on Pd(111) and Pt(111)

Using Density Functional Calculations, we researched on hydrogenolysis and isomerization of neopentane on Pd(111) and Pt(111). In general, lower activation energy is expected for Pt(111) surface, which is in agreement with the experimental activity for the two metals. From the calculated reaction barriers, α2γ2-diadsorbed intermediate poses the lowest barrier for both hydrogenolysis and isomerization reactions for Pd(111) which is 1.06 eV and 1.63 eV respectively, indicating isomerization and hydrogenolysis occur through the same intermediate and compete with each other. In contrast, on Pt(111) the α2-mono-adsorbed intermediate has the lowest activation barrier for isomerization (1.27 eV) while α2γ-di-adsorbed intermediate has the lowest activation barrier for hydrogenolysis (1.17 eV) indicating that isomerization and hydrogenolysis happen at different dehydrogenation levels on Pt(111). From the calculated barriers, we can partially rationalize the product selectivity for Pd and Pt catalysts. To conclude, neopentane isomerization and hydrogenolysis can follow the same mechanism since dehydrogenate ~4 H will greatly reduce reaction barriers. However, unlike hydrogenolysis, isomerization through α2-mono-adsorbed intermediate also play an important role in Pt(111) surface.