Methanation of Carbon Dioxide over Ni–Ce–Zr Oxides Prepared by One-Pot Hydrolysis of Metal Nitrates with Ammonium Carbonate

Effect of Ce/Zr Composition on Structure and Properties of Ce1-xZrxO2 Oxides and Related Ni/Ce1-xZrxO2 Catalysts for CO2 Methanation

Ce_1-xZr_xO₂ oxides (x = 0.1, 0.25, 0.5) prepared via the Pechini route were investigated using XRD analysis, N₂ physisorption, TEM, and TPR in combination with density functional theory calculations. The Ni/Ce_1-xZr_xO₂ catalysts were characterized via XRD analysis, SEM-EDX, TEM-EDX, and CO chemisorption and tested in carbon dioxide methanation. The obtained Ce_1-xZr_xO₂ materials were single-phase solid solutions. The increase in Zr content intensified crystal structure strains and favored the reducibility of the Ce_1-xZr_xO₂ oxides but strongly affected their microstructure. The catalytic activity of the Ni/Ce_1-xZr_xO₂ catalysts was found to depend on the composition of the Ce_1-xZr_xO₂ supports. The detected negative effect of Zr content on the catalytic activity was attributed to the decrease in the dispersion of the Ni⁰ nanoparticles and the length of metal-support contacts due to the worsening microstructure of Ce_1-xZr_xO₂ oxides. The improvement of the redox properties of the Ce_1-xZr_xO₂ oxide supports through cation modification can be negated by changes in their microstructure and textural characteristics.

Process Intensification of Methane Production via Catalytic Hydrogenation in the Presence of Ni-CeO2/Cr2O3 Using a Micro-Channel Reactor

A slight amount of Cr2O3 segregation in 40 wt% NiO/Ce0.5Cr0.5O2 was presented at the surface. The best catalytic performance towards the reaction was achieved at 74% of CO2 conversion and 100% CH4 selectivity at 310 °C, the reactant (H2/CO2) feed molar ratio was 4, and the WHSV was 56,500 mlN·h−1·g−1cat. The mechanistic pathway was proposed through carbonates and formates as a mediator during CO2 and H2 interaction. Activation energy was estimated at 4.85 kJ/mol, when the orders of the reaction were ranging from 0.33 to 1.07 for nth-order, and 0.40 to 0.53 for mth-order.

CO2 Hydrogenation to Synthetic Natural Gas over Ni, Fe and Co–Based CeO2–Cr2O3

CO2 methanation was studied over monometallic catalyst, i.e., Ni, Fe and Co; on CeO2-Cr2O3 support. The catalysts were prepared using one-pot hydrolysis of mixed metal nitrates and ammonium carbonate. Physicochemical properties of the pre- and post-exposure catalysts were characterized by X-Ray Powder Diffraction (XRD), Hydrogen Temperature Programmed Reduction (H2-TPR), and Field Emission Scanning Electron Microscope (FE-SEM). The screening of three dopants over CeO2-Cr2O3 for CO2 methanation was conducted in a milli-packed bed reactor. Ni-based catalyst was proven to be the most effective catalyst among all. Thus, a group of NiO/CeO2-Cr2O3 catalysts with Ni loading was investigated further. 40 % NiO/CeO2-Cr2O3 exhibited the highest CO2 conversion of 97.67% and CH4 selectivity of 100% at 290 °C. The catalytic stability of NiO/CeO2-Cr2O3 was tested towards the CO2 methanation reaction over 50 h of time-on-stream experiment, showing a good stability in term of catalytic activity.

Tar steam reforming for synthesis gas production over Ni-based on ceria/zirconia and La0.3Sr0.7Co0.7Fe0.3O3 in a packed-bed reactor

In this work, NiO level was varied from 5 to 40% whereas Ce_xZr_1-xO₂ (x = 0.5, 0.7 and 0.9) (CZO) and La_0.3Sr_0.7Co_0.7Fe_0.3O₃ (LSCF) were chosen as two different kinds of support. Regardless the type of support, the surface NiO (at 40%) was completely reduced at 600 °C, giving the amount of activated Ni at 8950 μmol/g_cat. The reducibility of the updoped LSCF was found to be much better than that of the undoped CZO, evidenced by the H₂-TPR of the both materials at 600 °C where the oxygen storage capacity (OSC) of LSCF and CZO was determined at 4273 and 307 μmol/g_cat, respectively. In contrast, the OSC of 40%Ni-CZO (where x = 0.7, 0.9) was found to be higher than that of the LSCF, implying that the addition of Ni more enhanced both electronic defect and oxygen mobility in CZO than in LSCF, according to the H₂-TPR results. Coke resistant of CZO is presumable more satisfying than that of LSCF, thus, the longer lifespan of the CZO catalyst system is expected. The catalytic performance of 40%Ni-CZO (x = 0.9) was however comparable with 40%Ni-LSCF as they accommodate the same number of active sites. The slightly better catalytic performance of the 40%Ni-CZO (x = 0.9) could be due to its smaller crystallite size (CZO = 26.83, LSCF = 35.73), rendering more access for the relative gaseous reactants. The best catalyst amongst all was 5%Ni-CZO (x = 0.9), giving 89% toluene conversion, 46% H₂ yield, 71% CO selectivity, and 25% CO₂ selectivity at optimum reaction temperature of 700 °C.

Low Temperature Methanation of CO2 on High Ni Content Ni-Ce-ZrOδ Catalysts Prepared via One-Pot Hydrothermal Synthesis

Ni-Ce-Zr-Oδ catalysts were prepared via one-pot hydrothermal synthesis. It was found that Ni can be partially incorporated into the Ce-Zr lattice, increasing surface oxygen species. The catalysts possess high surface areas even at high Ni loadings. The catalyst with Ni content of 71.5 wt.% is able to activate CO2 methanation even at a low temperature (200 °C). Its CO2 conversion and methane selectivity were reported at 80% and 100%, respectively. The catalyst was stable for 48 h during the course of CO2 methanation at 300 °C. Catalysts with the addition of medium basic sites were found to have better catalytic activity for CO2 methanation.

Developmental trends in CO2 methanation using various catalysts

Co₂ methanation-two edged sword to counter global warming and energy crisis.