Synthesis gas (mix of H2 and CO) is an industrially important feedstock used for ammonia, methanol, liquid fuel, and other synthesis. Dry reforming of hydrocarbons is an attractive approach for conversion to synthesis gas due to their relative abundance and consumption of two greenhouse gasses (CO2 and methane). Current industrial syngas processes produce high hydrogen content, which restricts the maturation of newer technologies such as higher alcohol and direct dimethyl ether synthesis.[1] Industrial steam reforming catalyst is Ni-based due to its high activity toward C-C and C-H bond cleavage. However, dry reforming has a higher tendency toward coking than steam reforming, so a coke-resistant support is desirable. The inherent redox properties and oxygen storage capacity of ceria can be enhanced with transition metal dopants such as Ti and Zr. In our study, a series of Ti-doped ceria supports (Ce1-xTixO2-δ, x: 0.1-0.5) were synthesized with the sol-gel method and 0.5-10 wt.% Ni was added to the support via the impregnation method. Structures, morphologies, compositions, reducibility of Ni supported on Ti-doped ceria were examined with XRD, SEM, ICP, and H2-TPR with respect to the Ti dopant concentrations and Ni loadings. Reactivity data were collected with a three-channel on-line Agilent 7890B GC. Experimental results for dry reforming of methane indicated conversions close to thermodynamic equilibrium values throughout the temperature range of 25-800 °C. Methane conversion increases from 16% at 500 °C to 90% at 800 °C. Dry reforming of mixed C1-C3 hydrocarbons containing 5, 8 and 25% of propane, ethane, and methane respectively, showed similar CO2 conversion with a lower methane conversion at temperatures below 750 °C. Evidence of ethane and propane thermal decomposition to methane suggests a possible reason for decreased apparent methane conversion. Conversions of ethane and propane were observed at temperatures as low as 450 °C, which are 10 and 24%, respectively, and close to complete propane and ethane conversions were observed at 675 and 725 °C, respectively. Ni/Ti-doped ceria showed good stability during a 90-hour reforming study of mixed hydrocarbons at 700 °C. Only a slow decrease in CO2 and methane conversions and slow decrease in H2 and CO yields were detected, while propane and ethane conversions remained close to 100%. Our results demonstrated that Ni/Ti-doped ceria exhibits excellent catalytic behavior for dry reforming of hydrocarbons.

Dry reforming of C1-C3 hydrocarbons over Ni particles on Ti-doped ceria

ACS Spring Meeting 2021

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