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Molybdenum carbide (Mo2C), an interstitial transition metal carbide, has been used in a myriad of industrial applications due to its refractory nature, extreme hardness and strength, and high electrical and thermal conductivity. It also possesses catalytic activity for many chemical processes such as hydrodeoxygenation, reforming, water–gas shift, and the Fischer–Tropsch reaction. Among the current synthesis methods available to produce β-Mo2C, temperature-programmed reduction yields materials with the highest specific surface areas. The objective of the present work is to perform a detailed investigation of the carburization process and to determine the key intermediate phases that are formed during reduction. To achieve this objective, we performed the carburization process under pulse conditions wherein a small amount of CH4 in each pulse was reacted with a packed bed of MoO2. Our XRD and TEM results demonstrate that the solid-phase transformation from MoO2 to β-Mo2C follows a “plum-pudding” mechanism where Mo metal crystallites are constantly formed as the key intermediate phase throughout the matrix.

This paper describes an application of a NiMo-ceria-zirconia (NiMo-CZ) catalyst as a micro-reforming layer for solid oxide fuel cells running on isooctane (i.e., a gasoline surrogate). The catalyst layer was applied on top of a conventional anode supported single cell with a configuration of Ni-yttria-stabilized zirconia (YSZ) anode, YSZ/Ce0.8Sm0.2O1.9 bi-layer electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-δ cathode. Our findings show that the application of the novel catalyst layer was an effective way to reform the mixture of isooctane and air into H2 and CO, which facilitated the electrochemical oxidation of complex hydrocarbons at the anode. At 750 °C, the single cell with the micro-reforming layer exhibited a low polarization resistance of 1.36 Ω cm2 and a maximum power density of 405 mW cm−2 in the direct feeding condition of an isooctane/air mixture. At the current density of 500 mA cm−2, the cell voltage presented a fairly low degradation rate of 3.0 mV h−1 during a 12 h stability test. The excellent electrochemical performance suggests the high catalytic activity of the NiMo-CZ catalyst layer for reforming isooctane and suppressing degradation of the single cell in the direct feeding of isooctane/air.

The present investigation is focused on improving the performance of molybdenum dioxide (MoO2) by doping with Ti for the partial oxidation (POX) of n-dodecane. Ti-doped MoO2 nanoparticles were synthesized via solvothermal cracking of polycrystalline MoO3 microparticles prepared by ultrasonic spray pyrolysis in the presence of a Ti precursor. Partial oxidation of n-dodecane was conducted at 850 °C with an O2/C ratio of 0.5. The 6 at% Ti-doped MoO2 was fully converted into orthorhombic carbide phase (β-Mo2C) during the reaction. This carbide sample showed high catalytic activity and stability with conversion and H2 yield of 94.4% and 86.3% after 24 h on stream, respectively. On the other hand, un-doped MoO2 was partially converted into the carbide phase during the reaction, which led to mixed oxide and carbide phases. This mixed phase showed poor catalytic activity and rapid deactivation after only 6 h of operation. Our ammonia temperature programmed desorption (TPD) and pyridine diffuse reflectance infrared Fourier transform (DRIFT) tests suggest that the addition of Ti to MoO2 improves both the density and strength of Lewis acid sites, and hence improves hydrocarbon activation. This increased surface carbon activation would enhance the carburization process of the Ti-doped MoO2 catalyst and retain the carbide phase under the POX condition.

Catalytic reduction by the reverse water gas shift (RWGS) reaction is an efficient way to utilize carbon dioxide and reduce its environmental impact as a greenhouse gas. In this research, an active CuFe/Al 2 O 3 nano powder was developed as a high temperature reforming catalyst for the RWGS reaction. The powder was synthesized by a wet-impregnation method and the copper alloy was uniformly dispersed on the γ-Al 2 O 3 support. At a gas space velocity of 60,000 h −1 , the conversion of carbon dioxide was 42% at 700 °C, which is very close to the equilibrium conversion of 44%. The results indicated excellent reforming activity of the CuFe/Al 2 O 3 catalyst for the high temperature RWGS reaction. In addition, the catalyst was applied in the form of a reforming layer over a conventional Ni-based electrode of a solid oxide electrolysis cell (SOEC) for an integrated SOEC-RWGS system. Hydrogen produced from steam electrolysis over the Ni-based cathode can be efficiently utilized to reduce the carbon dioxide by the RWGS reaction over the CuFe/Al 2 O 3 -based reforming layer. In this bilayer design, the reforming layer maintained the high surface area necessary for achieving good reforming activity, while the electrode layer possessed a high degree of sintering to enhance its electrochemical function. A high conversion of carbon dioxide (37% at 700 °C) was obtained in our bilayer SOEC-RWGS system. This promising result suggests the feasibility of the integrated SOEC-RWGS system for an efficient co-electrolysis device.

A Ni-based nanoparticle catalyst was synthesized over a silica support via wet impregnation using either ethylene glycol or water. X-ray diffraction and transmission electron microscopy analysis showed that the particle size of the Ni catalyst prepared using ethylene glycol as the solvent tended to be smaller than that obtained when water was used. The resulting catalysts were tested for performance toward partial oxidation (POX) of isooctane at high weight hourly space velocities (WHSV). The results were compared with those from a Rh-based catalyst, which is commonly used for the same reaction. At a WHSV of 13.8 h −1 , a Ni/SiO 2 catalyst with an average Ni particle size of 6.8 nm exhibits higher catalytic activity and stability with an improved resistance to carbon formation than a Ni/SiO 2 catalyst with an average Ni particle size of 16.6 nm. The catalyst with the smaller Ni particles outperformed the supported Rh catalyst for the POX of isooctane. To further improve the Ni dispersion and enhance its ability to run at even higher WHSVs with milliseconds of residence time, ceria was used as a promoter. The ceria-promoted Ni catalyst was also prepared by the wet impregnation method using ethylene glycol as the solvent. The addition of ceria corresponded with a further reduction in the size of the Ni nanoparticles and improved Ni dispersion. Using the Ni-Ce/SiO 2 catalyst the WHSV could be increased up to 20.0 h −1 while still maintaining its good catalytic activity. At this high WHSV of 20.0 h -1 , the Ni/SiO 2 catalyst without the ceria promoter and the Rh catalyst showed severe deactivation due to the formation of surface carbon deposits.

A Ca/Na-aluminosilicate was synthesized from kaolin and limestone via the hydrothermal reaction and was used for CO2 capture from a gas stream. Synthesis was performed at several combinations of temperature, pressure, kaolinite to limestone mass ratio, and the reaction time. The products were characterized by determining the crystalinity, surface morphology, surface area, and the pore size distribution. When the reaction temperature and pressure are increased, the sodium hydroxide concentration has a significant effect on the formation of novel Ca/Na-aluminosilicate phases. X-ray diffraction shows that a mixture of Gehlenite Ca2Al(Al1.22Si0.78O6.78)OH0.22 (43 wt %) and Stilbite Na5.76Ca4.96(Al15.68Si56.32O144) (57 wt%) is produced in 36 M NaOH at 200 °C and 15 bar. The adsorption capacity of the above product for CO2 from a gas stream increased with temperature, reaching a CO2 uptake of 294.7 mg/g at an equilibrium pressure of 45 bar and a temperature of 150 °C. Thermodynamic studies show spontaneous and endothermic adsorption behavior with a ΔHads of 4.64 kJ/mol, ΔSads of 25.25 J/mol.K, and ΔGads of −6.09 kJ/mol obtained at 150 °C. The CO2 adsorption/cycling process were repeated and it was found that the capacity of the novel adsorbent decreases in the second cycle and remains constant after that. This suggests chemisorption process took place on the fresh adsorbent and physical adsorption occurred at higher cycles.