(103b) Dry Methane Reforming for Syngas Production

Carbon dioxide (CO₂) capture and utilization (CCU) technologies is one of the routes to mitigate warming problem caused by the use of fossil energy sources. One of the directions in CO₂ utilization focus on dry methane reforming (DMR) reaction to produce syngas (mixture of CO and H₂) and then synthesize hydrocarbons, methanol, ammonia, etc. DMR catalysts are based on Nickel (Ni) can be much less expensive compared to highly expensive noble metals but suffers major deactivation due to carbon deposition [1]. Therefore, an efficient economic and stable catalyst is crucial in order to implement industrially this environmentally friendly reaction to produce syngas [2]. In the present work, the advantages of nanowire materials are introduced into catalyst design for improved coke resistance compared to other catalysts supported on nanoparticle morphologies.

Materials and Methods

Porous potassium titanates and titania nanowire supports were provided by Advance Energy Materials LLC. and were synthesized using solvo-plasma oxidation technique [3]. The nanowires were decorated with Ni and Ni based materials through impregnation. Once the catalyst were dried and calcined were submitted to catalytic testing. The catalytic testing was performed in a packed bed reactor as shown in Figure 1. In a typical experiment, 0.2gms of catalyst are placed over quartz wool in a quartz tube. The reactor is heated using a tubular furnace and the outlet is connected to an Agilent GC-7820A with TCD/FID detector. The material is reduced under the reaction temperature for 2 hours in a 10% hydrogen flow. After reduction, the gas flow is changed to a 10% of CH4 and 5% CO₂ to promote the coking process. Reaction activity is monitored over time.

Results and Discussion

When catalysts prepared with nanowire and commercial materials are compared, the commercial based materials displayed a clear deactivation while the nanowire based sample maintained its initial activity. CO₂ on the nanowire surface can interact with carbon deposits on Ni catalyst clusters via reverse Boudouard reaction and remove the carbon deposit into carbon monoxide. Typically, high carbon species mobility on nickel surface leads to carbon precipitation at the hidden metal-support interface thereby enhancing the interactions between CO₂ on nanowires with the deposited carbon on nickel clusters. Consistent results are obtained using different nanowire supported catalysts with different loadings.

Significance

This work focuses in understanding the role of nanowire based supports in the design of coke resistant catalysts for the DMR reaction. The use of nanowire supports helped with stabilization and activity of DMR catalysts. Fundamental understanding of the reasons for improved coke resistance observed with nanowires supported catalysts could be further used to design catalysts for other applications.

References

1. Bian, Z.; Kawi, S., Highly carbon-resistant Ni–Co/SiO₂ catalysts derived from phyllosilicates for dry reforming of methane. Journal of CO₂ Utilization 2017, 18, 345-352.
2. Bian, Z. F.; Das, S.; Wai, M. H.; Hongmanorom, P.; Kawi, S., A Review on Bimetallic Nickel-Based Catalysts for CO₂ Reforming of Methane. ChemPhysChem 2017, 18 (22), 3117-3134.
3. Kumar, J-H. Kim, J.B. Jasinski, E.L. Clark, and M.K. Sunkara, “Alkali assisted, atmospheric plasma production titania nanowire powders and arrays”, Crystal Growth and Design, 11 (7), 2913 (2011)