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Hydrothermal Mineralization
Published in Sandeep Kumar, Florin Barla, Sub- and Supercritical Hydrothermal Technology, 2019
Mixed ceria-zirconia oxides synthesis by hydrothermal mineralization can be conducted either under sub- or supercritical water conditions. The formation of metal oxides under hydrothermal conditions occurs in two steps [20]: Hydrolysis:M(NO3)xaq+xH2O→M(OH)xs+xHNO3Dehydration:M(OH)xs→MOx/2+x2H2O
Biomass Pyrolysis and Pyrolysis Oils
Published in Ozcan Konur, Biodiesel Fuels, 2021
Rioch et al. (2005) study biohydrogen production from pyrolysis oils in a paper with 323 citations. They focus on the use of noble metal-based catalysts for the steam reforming of a few model compounds and that of an actual pyrolysis oil. They perform the steam reforming of the model compounds in a temperature range of 650–950°C over Pt, Pd, and Rh supported on alumina and a ceria-zirconia sample. The model compounds used were acetic acid, phenol, acetone, and ethanol. They find that the nature of the support played a significant role in the activity of these catalysts. The use of ceria-zirconia, a redox mixed oxide, led to higher H2 yields as compared to the case of the alumina-supported catalysts. The supported Rh and Pt catalysts were the most active for the steam reforming of these compounds, while Pd-based catalysts performed poorly. They also study the activity of the promising Pt and Rh catalysts for the steam reforming of a pyrolysis oil obtained from beech wood fast pyrolysis. Temperatures close to, or higher than, 800°C were required to achieve significant conversions to COx and H2 (e.g. H2 yields around 70%). The ceria-zirconia materials showed a higher activity than the corresponding alumina samples. A Pt/ceria-zirconia sample used for over 9 h showed essentially constant activity, while extensive carbonaceous deposits were observed on the quartz reactor walls early on. No benefit was observed by adding a small amount of O2 to the steam/pyrolysis oil feed (‘autothermal reforming’), probably partly due to the already high concentration of oxygen in the pyrolysis oil composition.
Tri-reforming of surrogate biogas over Ni/Mg/ceria–zirconia/alumina pellet catalysts
Published in Chemical Engineering Communications, 2018
Xianhui Zhao, Huong T. Ngo, Devin M. Walker, David Weber, Debtanu Maiti, Ummuhan Cimenler, Amanda D. Petrov, Babu Joseph, John N. Kuhn
Ni/Mg/Ce0.6Zr0.4O2/Al2O3 pellets were synthesized using cylindrical alumina pellets (3.18 mm diameter, about 4.12 mm length, stock number 43855, Alfa Aesar) as the carrier. The ceria-zirconia solution was made by weighing 4.78 g of Ce(NO3)3 · 6H2O (99.5% pure; Alfa Aesar), 1.83 g of ZrO(NO3)2 · xH2O (99.9% pure; Alfa Aesar), and about 3.91 g of deionized (DI) water. This homogeneous solution was then added to alumina pellets (16.8 g) dropwise. After the metal nitrate solution was absorbed by alumina pellets, the pellets were dried in a furnace at 120°C for 2 h using a ramp rate of 10°C min−1 and then calcined at 800°C for 4 h at 10°C min−1. After cooling down, Ni (8.3% by mass relative to Ce0.6Zr0.4O2) and Mg (8.3% by mass relative to Ce0.6Zr0.4O2) were loaded on the pellets. The 1.39 g of Ni(NO3)2 · 6H2O (99.9985% pure; Alfa Aesar) and 1.92 g of Mg(NO3)2 · H2O (99.999% pure; Alfa Aesar) were dissolved in about 1.66 g of deionized water to form homogeneous solution, which was then added dropwise to the pellets. The pellets were dried at 120°C for 2 h at 10°C min−1 and finally calcined at 500°C for 4 h at 10°C min−1. The mass ratio of Ni:Mg:Ce0.6Zr0.4O2:Al2O3 was 1:1:10:60.