Ni-Sr/TiZr for H2 from methane via POM: Sr loading & optimization.

Achieving remarkable H2 yield with significantly high H2/CO over Ni-based catalysts through partial oxidation of methane (POM) is a realistic approach to depleting the concentration of CH4 and using H2 and CO as synthetic feedstock. This study examined Ni catalysts on titania-zirconia for methane conversion via POM at 600 °C and atmospheric pressure. The addition of strontium to the catalyst was explored to improve its performance. Catalysts were characterized by X-ray diffraction, Raman-infrared-UV-vis spectroscopy, and Temperature-programmed reduction-desorption techniques (TPR, TPD). 2.5 wt% Sr addition induced the formation of the highest concentration of extreme basic sites. Interestingly, over the unpromoted catalyst, active sites are majorly generated by hardly reducible NiO species whereas upon 2.5 wt% promoted Sr promotional addition, most of active sites are derived by easily reducible NiO species. 45% CH4 conversion and 47% H2 yield with H2/CO = 3.5 were achieved over 2.5 wt% Sr promoted 5Ni/30TiO2 + ZrO2 catalyst. These results provide insight into the role of basic sites in enhancing activity through switching indirect pathways over direct pathways for POM. Further process optimization was carried out in the range of 10 000-22 000 SV, 0.35-0.75 O2/CH4, and 600-800 °C reaction temperature over 5Ni2.5Sr/30TiO2 + ZrO2 by using central composite design under response surface methodology. The optimum activity as high as ∼88% CH4 conversion, 86-87% yield of H2, and 2.92H2/CO were predicted and experimentally validated at 800 °C reaction temperature, 0.35O2/CH4 ratio, and 10 000 space velocity.

Optimizing Hydrogen Production: Influence of Promoters in Methane Decomposition on Titania-Modified-Zirconia Supported Fe Catalyst.

This study addresses the pivotal challenge of hydrogen production through methane decomposition, offering a pathway to achieving clean energy goals. Investigating the utilization of titania-modified zirconia dual redox supports (10TiZr) in iron or doped iron-based catalysts for the CH4 decomposition reaction, our research involves a thorough characterization process. This includes analyses of the surface area porosity, X-ray diffraction, Raman-infrared spectroscopy, and temperature-programmed reduction/oxidation. The observed sustained enhancement in catalytic activity over extended durations suggests the in situ formation of catalytically active sites. The introduction of Co or Ni into the 30Fe/10TiZr catalyst leads to the generation of a higher density of reducible species. Furthermore, the Ni-promoted 30Fe/10TiZr catalyst exhibits a lower crystallinity, indicating superior dispersion. Notably, the cobalt-promoted 30Fe/10TiZr catalyst achieves over 80% CH4 conversion and H2 yield within 3 h. Additionally, the Ni-promoted 30Fe/10TiZr catalyst attains a remarkable 87% CH4 conversion and 82% H2 yield after 3 h of the continuous process.

Stability and Activity of Rhodium Promoted Nickel-Based Catalysts in Dry Reforming of Methane.

The rhodium oxide (Rh2O3) doping effect on the activity and stability of nickel catalysts supported over yttria-stabilized zirconia was examined in dry reforming of methane (DRM) by using a tubular reactor, operated at 800 °C. The catalysts were characterized by using several techniques including nitrogen physisorption, X-ray diffraction, transmission electron microscopy, H2-temperature programmed reduction, CO2-temperature programmed Desorption, and temperature gravimetric analysis (TGA). The morphology of Ni-YZr was not affected by the addition of Rh2O3. However, it facilitated the activation of the catalysts and reduced the catalyst's surface basicity. The addition of 4.0 wt.% Rh2O3 gave the optimum conversions of CH4 and CO2 of ~89% and ~92%, respectively. Furthermore, the incorporation of Rh2O3, in the range of 0.0-4.0 wt.% loading, enhanced DRM and decreased the impact of reverse water gas shift, as inferred by the thermodynamics analysis. TGA revealed that the addition of Rh2O3 diminished the carbon formation on the spent catalysts, and hence, boosted the stability, owing to the potential of rhodium for carbon oxidation through gasification reactions. The 4.0 wt.% Rh2O3 loading gave a 12.5% weight loss of carbon. The TEM images displayed filamentous carbon, confirming the TGA results.

Barium-Promoted Yttria-Zirconia-Supported Ni Catalyst for Hydrogen Production via the Dry Reforming of Methane: Role of Barium in the Phase Stabilization of Cubic ZrO2.

Developing cost-effective nonprecious active metal-based catalysts for syngas (H2/CO) production via the dry reforming of methane (DRM) for industrial applications has remained a challenge. Herein, we utilized a facile and scalable mechanochemical method to develop Ba-promoted (1-5 wt %) zirconia and yttria-zirconia-supported Ni-based DRM catalysts. BET surface area and porosity measurements, infrared, ultraviolet-visible, and Raman spectroscopy, transmission electron microscopy, and temperature-programmed cyclic (reduction-oxidation-reduction) experiments were performed to characterize and elucidate the catalytic performance of the synthesized materials. Among different catalysts tested, the inferior catalytic performance of 5Ni/Zr was attributed to the unstable monoclinic ZrO2 support and weakly interacting NiO species whereas the 5Ni/YZr system performed better because of the stable cubic ZrO2 phase and stronger metal-support interaction. It is established that the addition of Ba to the catalysts improves the oxygen-endowing capacity and stabilization of the cubic ZrO2 and BaZrO3 phases. Among the Ba-promoted catalysts, owing to the optimal active metal particle size and excess ionic CO3 2- species, the 5Ni4Ba/YZr catalyst demonstrated a high, stable H2 yield (i.e., 79% with a 0.94 H2/CO ratio) for up to 7 h of time on stream. The 5Ni4Ba/YZr catalyst had the highest H2 formation rate, 1.14 mol g-1 h-1 and lowest apparent activation energy, 20.07 kJ/mol, among all zirconia-supported Ni catalyst systems.

Influence of Nature Support on Methane and CO2 Conversion in a Dry Reforming Reaction over Nickel-Supported Catalysts.

A promising method to reduce global warming has been methane reforming with CO2, as it combines two greenhouse gases to obtain useful products. In this study, Ni-supported catalysts were synthesized using the wet impregnation method to obtain 5%Ni/Al2O3(SA-5239), 5%Ni/Al2O3(SA-6175), 5%Ni/SiO2, 5%Ni/MCM41, and 5%Ni/SBA15. The catalysts were tested in dry reforming of methane at 700 °C, 1 atm, and a space velocity of 39,000 mL/gcat h, to study the interaction of Ni with the supports, and evaluation was based on CH4 and CO2 conversions. 5%Ni/Al2O3(SA-6175) and 5%Ni/SiO2 gave the highest conversion of CH4 (78 and 75%, respectively) and CO2 (84 and 82%, respectively). The catalysts were characterized by some techniques. Ni phases were identified by X-ray diffraction patterns. Brunauer-Emmett-Teller analysis showed different surface areas of the catalysts with the least being 4 m2/g and the highest 668 m2/g belonging to 5%Ni/Al2O3(SA-5239) and 5%Ni/SBA15, respectively. The reduction profiles revealed weak NiO-supports interaction for 5%Ni/Al2O3(SA-5239), 5%Ni/MCM41, and 5%Ni/SBA15; while strong interaction was observed in 5%Ni/Al2O3(SA-6175) and 5%Ni/SiO2. The 5%Ni/Al2O3(SA-6175) and 5%Ni/SiO2 were close with respect to performance; however, the former had a higher amount of carbon deposit, which is mostly graphitic, according to the conducted thermal analysis. Carbon deposits on 5%Ni/SiO2 were mainly atomic in nature.