Dry Reforming Of Methane Over Substituted Lanthanum Zirconate Pyrochlore Catalysts

Author

Srikar Bhattar, Louisiana State University at Baton RougeFollow

Degree

Doctor of Philosophy (PhD)

Department

Gordon A. and Mary Cain Department of Chemical Engineering

Document Type

Dissertation

Abstract

One of the potential methods for producing syngas from two greenhouse gases (CH₄ and CO₂) is dry reforming of methane (DRM), which has received a lot of attention. DRM could lower the net emission of these gases if the energy used to power it comes from sources other than hydrocarbons. Despite being highly active, many conventional Ni based metal/support catalyst systems rapidly lose their activity due to the sintering or deposition of coke on the metal clusters' surfaces. Thus, it is crucial that the DRM catalyst must be coke resistant and thermally stable to avoid sintering.

DRM has been well studied using various catalysts over the past few decades, however, the challenges of commercialization are still prevalent. Ni-based catalysts are viable options for commercialization as Ni metal is inexpensive and widely available. For this purpose, Ni-based Lanthanum Zirconate catalysts were prepared and studied for this work. The La-Zr lattice framework provides high thermal stability required for extreme reaction conditions of DRM. Also, the intrinsic oxygen vacancies developed due to substitution of La or Zr site by lower valance atoms helps resist coke deposition.

In this research work, Ni, Ca, and Sr based Lanthanum Zirconate catalysts were synthesized, characterized by several spectroscopic, microscopic & thermal techniques, and tested for DRM. The presence of a double perovskite phase was observed in Ni-substituted pyrochlore catalysts at 6%wt loading of Ni. 6%wt loading showed better activity and stability compared to 1wt% Ni loading. Sr substitution improved oxygen vacancy ratio on the surface of the catalyst which indeed assisted in better activity and stability over 100hr reaction time compared to the unsubstituted catalyst. Also, in a study comparing Ni-substitution (LSNZ6) with the Ni-imprignation (6Ni/LSZ) of the pyrochlore oxide, it was determined that the site reactivity (TOF) of the substituted catalyst was found to be almost two times that of the impregnated catalyst. SSITKA studies revealed a shorter residence time of active carbon species (τ_c) on the surface of LSNZ6. The mechanism of DRM was studied using isotope labelled reactions and in-situ DRIFTS showed the dual site mechanism in the Ni-pyrochlore catalysts.

Date

11-15-2023

Recommended Citation

Bhattar, Srikar, "Dry Reforming Of Methane Over Substituted Lanthanum Zirconate Pyrochlore Catalysts" (2023). LSU Doctoral Dissertations. 6316.
https://repository.lsu.edu/gradschool_dissertations/6316

Committee Chair

James J. Spivey