Insight into CaO addition on coking resistance of Ni surface for sorption enhanced methane steam reforming: A density functional study

Density functional study has been performed for a new anticancer agent, cis-[PtCl2(NH3)(2-picoline)] (1), AMD473, now clinically tested. The molecular structure, natural charges, orbital occupancies, vibrational frequencies and metal-ligand stretching force constants were calculated using the modified Perdew-Wang functional (mPW1PW) with the combined D95V(d,p) and LANL2DZ basis set. For comparison, analogous calculations were performed for: cis-[PtCl2(NH3)(3-picoline)] (2), cis-[PtCl2(NH3)(pyridine)] (3) and cisplatin. The interesting structural feature of 1 is almost perpendicular orientation of the 2-picoline ligand with respect to the molecular plane. In the remaining complexes, 2 and 3, the tilt of the pyridine ring is smaller. The position of the methyl group in 1 introduces steric hindrance to an axial approach of the Pt metal. The natural bond analysis (NBO) has provided detailed insight into the electronic donor-acceptor interactions within the platinum coordination sphere. The results clearly indicate that the Pt-N(py) bond is stronger than Pt-NH3 bond, and the Pt-Cl bond trans to 2-picoline is weaker than the cis Pt-Cl bond. Thus, both the trans effect of the 2-picoline ligand and a steric hindrance of Pt in 1 can be of key importance in the different mode of binding of this drug to DNA, in comparison with cisplatin.

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Nickel-Supported on La2Sn2O7and La2Zr2O7Pyrochlores for Methane Steam Reforming: Insight into the Difference between Tin and Zirconium in the B Site of the Compound

ChemCatChem ◽

10.1002/cctc.201402551 ◽

2014 ◽

Vol 6 (12) ◽

pp. 3366-3376 ◽

Cited By ~ 47

Author(s):

Youhe Ma ◽

Xiang Wang ◽

Xiaojuan You ◽

Jianjun Liu ◽

Jinshu Tian ◽

...

Keyword(s):

Steam Reforming ◽

Methane Steam Reforming ◽

Methane Steam ◽

The Difference ◽

Insight Into

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Reaction Pathway for Coke-Free Methane Steam Reforming on a Ni/CeO2 Catalyst: Active Sites and Role of Metal-Support Interactions

10.26434/chemrxiv.14686740.v1 ◽

2021 ◽

Author(s):

Agustin Salcedo ◽

Pablo Lustemberg ◽

Ning Rui ◽

Robert M. Palomino ◽

Zongyuan Liu ◽

...

Keyword(s):

High Activity ◽

Steam Reforming ◽

Active Sites ◽

Density Functional ◽

Ambient Pressure ◽

Carbon Accumulation ◽

Methane Steam Reforming ◽

Severe Problem ◽

Methane Steam ◽

Water Activation

Methane steam reforming (MSR) plays a key role in the production of syngas and hydrogen from natural gas. The increasing interest in the use of hydrogen for fuel cell applications demands the development of catalysts with high activity at reduced operating temperatures. Ni-based catalysts are promising systems because of their high activity and low cost, but coke formation generally poses a severe problem. Studies of ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) indicate that CH4/H2O gas mixtures react with Ni/CeO2(111) surfaces to form OH, CHx and CHxO at 300 K. All these species are easy to form and desorb at temperatures below 700 K when the rate of the MSR process accelerates. Density functional theory (DFT) modeling of the reaction over ceria-supported small Ni nanoparticles predicts relatively low activation barriers between 0.3–0.7 eV for the complete dehydrogenation of methane to carbon and the barrierless activation of water at interfacial Ni sites. Hydroxyls resulting from water activation allow CO formation via a COH intermediate with a barrier of about 0.9 eV, which is much lower than that through a pathway involving lattice oxygen from ceria. Neither methane nor water activation are rate-determining steps, and the OH-assisted CO formation through the COH intermediate constitutes a low-barrier pathway that prevents carbon accumulation. The interaction between Ni and the ceria support and the low metal loading are crucial for the reaction to proceed in a coke-free and efficient way. These results could pave the way for further advances in the design of stable and highly active Ni-based catalysts for hydrogen production.

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