(352a) Dry Reforming of Methane over Ce0.7Ti0.3O2-? supported Nickel Catalyst

Sachin U. Nandanwar,^a,b Yunkai Zou,^a Linze Du,^a Joseph H. Holles,^b Jing Zhou,^a

^aDepartment of Chemistry, University of Wyoming, Laramie, WY 82071, and Email address: jzhou2@uwyo.edu

^bDepartment of Chemical Engineering, University of Wyoming, Laramie, WY 82071, and Email address: jholles@uwyo.edu

Abstract

Dry reforming of methane (DRM) utilizes two abundantly available greenhouse gases to produce industrially important syngas (CH₄ + CO₂ → 2CO + 2H₂). Syngas is used to produce synthetic petroleum as fuels or chemicals. The conversion of methane, the primary component of natural gas, to higher value products will become increasingly important for the near future. Current global challenge for the DRM reaction is to develop thermally stable and active catalysts that can show good resistance to deactivation. In our study, Ce_1-xTi_xO_2-δ (x: 0.1, 0.2, 0.3, and 0.5) supported nickel catalysts were synthesized by sol-gel methods with controlled Ni loadings between 1 and 10 wt.%. Ceria exhibits unique redox properties and oxygen storage capacities, which can better anchor Ni as small clusters and inhibit coke formation. Introduction of metal dopant, Ti, into ceria could promote its redox properties as well as enhance its thermal stability at high temperatures. All the prepared catalysts were characterized by a combination of spectroscopy and microscopy techniques including X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS), X-ray Photoelectron Spectroscopy (XPS), BET surface area, H₂-chemisorption, and H₂-temperature-programmed reduction (H₂-TPR). Their DRM performance was investigated in a continuous gas flow reactor using gas chromatography and mass spectrometry instruments and compared with respect to reaction temperatures, Ce:Ti ratios in the oxide supports, and Ni loadings. XPS and XRD data show the formation of Ce_1-xTi_xO_2-δ solid mixed oxide supports. The 2 wt.% Ni/Ce_0.7Ti_0.3O_2-δ catalyst was identified to deliver the best catalytic activity and stability among all the ceria supports and Ni loadings. At 650°C, the 2 wt.% Ni over Ce_0.7Ti_0.3O_2-δ catalyst shows good conversions of 73% and 79% for CH₄ and CO₂, respectively. The product yields were 42% and 52% for H₂ and CO. Additionally, compared to other metals including Pd and Co, the Ni catalyst delivers a higher reactivity and a long-term stability (up to 50 h) during the DRM reaction on stream. The enhanced reactivity and stability of this catalyst can be attributed to the unique interaction between the Ni metal and Ce_0.7Ti_0.3O_2-δ support, the high BET surface area (26 m² g^-1) and metal active sites.

This research work is financially supported by Wyoming Carbon Engineering Initiative from School of Energy Resources at University of Wyoming and NSF (grant number CHE1151846).