Activity In Dry Reforming Of Methane Research Articles

Influence of preparation method on activity and stability of Ni catalysts supported on Gd doped ceria in dry reforming of methane

Nickel catalysts supported on Gd doped ceria (NGDC), with various Ni content, were prepared through different preparation routes and evaluated for dry reforming of methane (DRM). Their detailed characterization revealed that method of preparation plays an important role in Ni dispersion, with catalysts prepared through co-precipitation showing high Ni dispersion. The co-precipitated 12NGDC-cp catalyst with 12wt% NiO was found to be superior in terms of high CO2 and CH4 conversions compared to catalysts prepared through citrate gel or impregnation methods Even H2 and CO yields are high on this catalyst, while it shows excellent durability with stable activity even after 100h on-stream. Thermogravimetric analysis of spent catalyst showed presence of coke, with transmission electron microscopic studies pointing to the presence of Ni crystallites at the mouth of the carbon whiskers. These Ni crystallites appear to be still active for DRM reaction. Among the spent catalysts, the carbon formation was high on catalysts that have bigger Ni crystallites, with the catalysts prepared through impregnation and citrate gel methods having higher coke. Investigations also reveal that the conversion of active (amorphous) carbon into stable (graphitic) carbon depends on the Ni crystallite size, temperature and duration of the reaction. These studies demonstrate that Gd doped ceria is a good support for Ni, to obtain high DRM activity and very good on-stream stability provided the catalysts are prepared through an appropriate method.

Modulating morphology and textural properties of ZrO2 for supported Ni catalysts toward dry reforming of methane

This work presents a facile and efficient approach to modulate morphology and textural properties of ZrO2 through ammonium fluoride‐urea assisted hydrothermal (FUAH) method with diverse parameters including molar ratio of NH4F to zirconium (nf/z), molar ratio of urea to zirconium (nu/z), hydrothermal temperature (Thydroth), and hydrothermal time (thydroth), which serve as support for supported Ni catalysts toward dry reforming of methane (DRM) to produce synthesis gas. The plausible mechanism for forming ZrO2 supports with different morphologies under diverse hydrothermal conditions was proposed. Various characterization techniques were employed to investigate the effect of preparation parameters on the morphology and textural properties of the as‐synthesized ZrO2 supports, as well as to reveal the structure‐performance relationship of the Ni/ZrO2 catalysts prepared by L‐arginine assisted incipient wetness impregnation method toward DRM reaction. The developed supported Ni catalyst on hierarchically structured ZrO2 with pinecone shape prepared by FUAH method (Ni/ZrO2‐FUAH) demonstrates higher activity and stability for DRM than that on ZrO2 prepared by traditional hydrothermal method (Ni/ZrO2‐H). The higher activity of Ni/ZrO2‐FUAH than Ni/ZrO2‐H can be ascribed to the higher Ni dispersion, smaller Ni crystalline size, and enhanced reducibility of NiO, significantly affected by morphology of support, as well as the higher coke‐resistance catalytic stability can be ascribed to smaller Ni particle size and stronger Ni‐support interaction, strongly dependent on morphology and textural properties of ZrO2 supports that affected by FUAH process parameters. The outstanding catalytic performance of the developed Ni/ZrO2‐FUAH catalyst allows it to be a promising candidate for synthesis gas production through DRM reaction. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2900–2915, 2017

Low-temperature dry reforming of methane to produce syngas in an electric field over La-doped Ni/ZrO2 catalysts

Dry reforming of methane (DRM) was conducted over various transition metal supported ZrO2 catalysts in an electric field. Catalyst of 1wt%Ni/10mol%La-ZrO2 showed high DRM activity even at 423K of external temperature, at which no DRM proceeds in the conventional catalytic systems. By virtue of the low reaction temperature, low amounts of carbon deposition were confirmed even in conditions of high CH4 conversion in the electric field. The imposed electric power was correlated to with the catalytic activities in the electric field. Syngas is producible at low temperature with high energy efficiency.

Redox dynamics of Ni catalysts in CO2 reforming of methane

The influence of redox dynamics of a Ni/MgAl oxide catalyst for dry reforming of methane (DRM) at high temperature was studied to correlate structural stability with catalytic activity and coking propensity. Structural aging of the catalyst was simulated by repeated temperature-programmed reduction/oxidation (TPR/TPO) cycles. Despite a very high Ni loading of 55.4wt.%, small Ni nanoparticles of 11nm were obtained from a hydrotalcite-like precursor with a homogeneous distribution. Redox cycling gradually changed the interaction of the active Ni phase with the oxide support resulting in a crystalline Ni/MgAl2O4-type catalyst. After cycling the average particle size increased from 11 to 21nm – while still a large fraction of small particles was present – bringing about a decrease in Ni surface area of 72%. Interestingly, the redox dynamics and its strong structural and chemical consequences were found to have only a moderate influence on the activity in DRM at 900°C, but lead to a stable attenuation of carbon formation due to a lower fraction of graphitic carbon after DRM in a fixed-bed reactor. Supplementary DRM experiments in a thermobalance revealed that coke formation as a continuous process until a carbon limit is reached and confirmed a higher coking rate for the cycled catalyst.

Bi- and trimetallic Ni catalysts over Al2O3 and Al2O3-MOx (M = Ce or Mg) oxides for methane dry reforming: Au and Pt additive effects

The effects of Au and Pt addition (in very low concentrations, 0.2wt%) on the catalytic performances of 4wt% Ni catalysts supported over Al2O3 and Al2O3-10wt%MOx (M=Ce or Mg) oxides were studied in the dry reforming of methane (DRM). The properties of the catalysts, before and after long-run tests, were investigated employing N2 adsorption–desorption isotherms, XRD, H2-TPR, XPS, TEM, EDX microanalysis and O2-TPO. It was shown that addition of a small amount of Au and Pt (0.2wt%) to Ni catalyst leads to formation of a synergistic interaction, which induces easy reduction of NiO species and decrease of particle size. It was also found that the small amount of Au and Pt addition plays an important role on catalytic performance of bi-/trimetallic catalysts and carbon poisoning. The improvement of catalytic activity and stability obtained for the trimetallic NiAuPt/Al2O3 catalyst was attributed to the formation of high active Ni-Au-Pt nanoparticles, synergistically interacting, where growth of small amount of bamboo-like carbon nanotubes occurs. Conversely, abundant amorphous carbon and both, amorphous and carbon nanotubes, were detected in the bimetallic, NiAu and NiPt, and monometallic Ni alumina supported catalysts.The effect of Al2O3 doping with MgO or CeO2 also significantly improves the catalytic performance of monometallic Ni catalyst and the nature and amount of carbon deposits as well. However, the support effect was weakened in both Mg and Ce doped trimetallic catalysts due to the dominant role of Ni-Au-Pt interaction responsible of the enhanced activity for DRM.