Ab Initio Study of Organometallic Phthalocyanine Catalysts for the Conversion of
Methane to Methanol Chase Ferrone and Pabitra Choudhury
Chemical Engineering Department, New Mexico Tech, Socorro, NM 87801 USA
Abstract Methane’s low energy density and contribution to the greenhouse gas effect has emphasized the importance of converting methane to methanol. In this work, organometallic, single transition metal active site heterogeneous phthalocyanine catalysts have been designed to activate methane in a single step process. Copper and cobalt phthalocyanines, supported by TiN and BN substrates, have been studied using ab initio density functional theory (DFT) implemented in the Vienna ab initio software package (VASP). Titanium nitride (TiN) has potential as a substrate due to its metallic-like behavior and favorable optical properties. On the other hand, boron nitride (BN) substrate has graphene-like structure, which has been proved effective in methane catalysis. Results show an inverse relationship between the rate of C-H bond breakage and the metal-oxo species intermediate formation energy. A correlation between rate and formation energy has been further explored in active site metal charge state as a potential descriptor even in the presence of nonidealities, such as substrate vacancies and doping will also be discussed. A copper phthalocyanine supported by titanium nitride (TiNCuPc) catalyst is the best candidate for methane to methanol conversion. The TiNCuPc catalytic system had a favorable methane activation energy barrier at 0.24 eV using Dimer method transition state theory. Catalyst regeneration of TiNCuPc was greatly improved from previous works while still maintaining a desirable energy barrier.
Acknowledgments: Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for support (or partial support) of this research. The work is supported by ACS-PRF Grant No [58740-UR6]. This work used the Extreme Science and Engineering Discovery Environment (XSEDE) TACC at the stampede2 through allocation [TGDMR140131]. This work utilized resources from the University of Colorado Boulder Research Computing Group, which is supported by the National Science Foundation (awards ACI-1532235 and ACI- 1532236), the University of Colorado Boulder, and Colorado. PCC Cluster, NM Consortium, NM.
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