Catalytic decomposition of methane to produce hydrogen: A review

Once a biorefinery is ready to operate, the main processed materials need to be completely evaluated in terms of many different factors, including disposal regulations, technological limitations of installation, the market, and other societal considerations. In biorefinery, glycerol is the main by-product, representing around 10% of biodiesel production. In the last few decades, the large-scale production of biodiesel and glycerol has promoted research on a wide range of strategies in an attempt to valorize this by-product, with its transformation into added value chemicals being the strategy that exhibits the most promising route. Among them, C3 compounds obtained from routes such as hydrogenation, oxidation, esterification, etc. represent an alternative to petroleum-based routes for chemicals such as acrolein, propanediols, or carboxylic acids of interest for the polymer industry. Another widely studied and developed strategy includes processes such as reforming or pyrolysis for energy, clean fuels, and materials such as activated carbon. This review covers recent advances in catalysts used in the most promising strategies considering both chemicals and energy or fuel obtention. Due to the large variety in biorefinery industries, several potential emergent valorization routes are briefly summarized.

Recent Advances in Glycerol Catalytic Valorization: A Review

The effects of Ni particle size (dNi ∼ 22–45 nm) of Ni/Ce0.8Ti0.2O2-δ on the carbon paths in the dry reforming of methane at 750 °C have been investigated by various transient and isotopic experiments. The aim was to provide new insights for improving catalyst’s coke-resistance. Various correlations have been derived between dNi and (i) the initial kinetic rates (per Ni particle) of CH4 dissociation and CO disproportionation reactions along with their respective amounts of carbon accumulation, (ii) the integral rates of CH4 conversion and CO formation and the amount of carbon deposition in the DRM, and (iii) the rate of carbon removal by lattice oxygen of support compared to that by oxygen formed via the CO2 activation route during DRM. The former rate was found larger than the latter one independent of dNi (nm). CH4 dissociation is the exclusive route of inactive carbon formation during DRM independent of dNi.

Dry reforming of methane over Ni/Ce0.8Ti0.2O2-δ: The effect of Ni particle size on the carbon pathways studied by transient and isotopic techniques

Global warming is mainly due to the massive emissions of greenhouse gases such as carbon dioxide (CO2) and methane (CH4), which should thus be limited in the future. For that, dry reforming of methane (DRM) is promising because this process uses CH4 and CO2. Ni-based catalysts have been recently developed for DRM, as a cheaper alternative to noble metal catalysts. Here, we review CO2 reforming of CH4 to syngas over nickel-based catalysts, with focus on the design and controlling factors. We discuss the microscale structure to overcome the bottlenecks of rapid carbon deposition and easy sintering. We present the four factors controlling the activity of Ni-based catalysts: 1) promoters, which improve the catalytic activity and reduce carbon deposition; 2) supports allowing to obtain highly dispersed active components and to limit metal sintering and carbon deposition at high temperatures; 3) preparation methods, which control particle size and dispersion of the active metal; and 4) bimetallic catalytic components, which improve the properties of nickel-based catalysts.

CO2 reforming of CH4 to syngas over nickel-based catalysts

Syngas production via combined dry and steam reforming of methane over Ni-Ce/ZSM-5 catalyst

Biogas dry reforming for hydrogen production over Ni-M-Al catalysts (M = Mg, Li, Ca, La, Cu, Co, Zn)

Ni supported and co-precipitated catalysts promoted by Mg were evaluated for hydrogen production by the glycerol steam reforming. The samples were prepared by incipient wetness impregnation of alumina and by the continuous co-precipitation method. The catalysts were characterized by XRD, SBET, TPR, NH3-TPD, TPO and SEM/TEM. The catalytic tests were performed in the range from 500 to 650 °C in a fixed bed tubular reactor. The gaseous products were analyzed online by gas chromatography. It was found that the partial substitution of Ni by Mg improves the dispersion of Ni, decreases the acidity of the catalysts and increases the resistance to sintering of Ni. The unreduced catalysts presented higher selectivity for H2 than the previously reduced catalysts. The catalyst unreduced impregnated with 20% Ni showed the highest selectivity in the production of hydrogen (55%), at the temperature of 650 °C. Unreduced samples prepared by co-precipitation presented smaller Ni0 crystallite size after the reaction. The catalyst reduction step is unnecessary for this reaction.

Camila O. Calgaro

Papers

Biogas dry reforming for hydrogen production over Ni-M-Al catalysts (M = Mg, Li, Ca, La, Cu, Co, Zn)

Hydrogen production by glycerol steam reforming over Ni based catalysts prepared by different methods.

Dry reforming of methane using modified sodium and protonated titanate nanotube catalysts

Decomposition of methane over Co3−xAlxO4 (x=0–2) coprecipitated catalysts: The role of Co phases in the activity and stability

Graphene and carbon nanotubes by CH4 decomposition over CoAl catalysts