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High temperature (800 °C) pre-calcination of CeO2 support decreases the surface defects and improves the mobility of surface lattice oxygen. As a result, the supported Pt clusters have higher oxygen coverage and superior HC oxidation activity.

In the base catalyzed ethanol condensation reactions, the calcined MgO–Al2O3 derived hydrotalcites used broadly as catalytic material and the calcination temperature plays a big role in determining the catalytic activity. The characteristics of the hydrotalcite material treated between catalytically relevant temperatures 450 and 800 °C have been studied with respect to the physical, chemical, and structural properties and compared with catalytic activity testing. With the increasing calcination temperature, the total measured catalytic basicity dropped linearly with the calcination temperature and the total measured acidity stayed the same for all the calcination temperatures except 800 °C. However, the catalyst activity testing does not show any direct correlation between the measured catalytic basicity and the catalyst activity to the ethanol condensation reaction to form 1-butanol. The highest ethanol conversion of 44 % with 1-butanol selectivity of 50 % was achieved for the 600 °C calcined hydrotalcite material.

We report a hierarchically structured catalyst with steam reforming and hydrodeoxygenation functionalities being deposited in the micropores and macropores, respectively. The catalyst is highly efficient to upgrade the pyrolysis vapors of pine forest product residual, resulting in a dramatically decreased acid content and increased hydrocarbon yield without external H2 supply.

Carbon-supported metal catalysts (Cu/C, Fe/C, Pd/C, Pt/C, PdFe/C, and Ru/C) were characterized and evaluated for vapor-phase hydrodeoxygenation (HDO) of guaiacol (GUA), aiming at the identification/elucidation of active catalysts for high-yield production of completely hydrodeoxygenated products (e.g., benzene). Phenol was found to be the major intermediate on all catalysts. Saturation of the aromatic ring is the major pathway over the precious metal catalysts, forming cyclohexanone and cyclohexanol, followed by ring opening to form gaseous products. Base metal catalysts exhibit lower activity than the precious metal catalysts, but selectively form benzene along with small amounts of toluene, trimethylbenzene (TMB), and cresol without forming ring-saturated or ring-opening products. Compared with Fe/C and Pd/C, PdFe/C catalysts exhibit a substantially enhanced activity while maintaining the high selectivity to HDO products without ring saturation or ring opening. The enhanced activity of PdFe/C is attributed to the modification of Fe nanoparticles by Pd as evidenced by STEM, EDS, EXAFS, TPR, and theoretical calculations.

With efficient energy recovery, calcium-oxide-based absorbents that operate at elevated temperatures have an advantage over absorbents that operate at lower temperatures for CO2 capture from coal power plants. The major limitation of these absorbents is that the carbonation and decarbonation reactions of CaO and CaCO3 are far from complete or reversible. Rapid loss of CO2 capacity over many carbonation/decarbonation cycles is always observed because of severe absorbent sintering. We have found that this sintering effect can be effectively mitigated by properly mixing calcium oxide precursors with small rod-like MgAl2O4 spinel nanoparticles. A new class of CaO-based absorbents with much improved high-temperature durability was developed by wet physical mixing of calcium acetate with nano MgAl2O4 spinel particles followed by high-temperature calcination. CaO−MgAl2O4 (32 wt % spinel content) material provides 34 wt % CO2 capacity after 65 carbonation−decarbonation cycles (650 and 850 °C, respectively), corre...

The preparation and the pretreatment of Pd/ZnO catalysts were studied for methanol steam reforming. The presence of nitric acid in Pd nitrate precursor significantly altered the porosities and crystalline structures of the ZnO support. The dissolution of ZnO and extent of mixing between the Zn 2+ and Pd 2+ cations during catalyst preparation may have an impact on the PdZn alloy formation and its catalytic properties. The pretreatment of Pd/ZnO, which is critical to the PdZn alloy formation, depends not only on the reduction temperature but also on the reaction conditions under which hydrogen is formed.

Dye-sensitized solar cells (DSSC) utilizing titania (TiO2) nanomaterials in conjunction with a light-absorbing dye have been extensively explored for the last few decades. Earlier efforts to surpass the 10% overall light conversion efficiency of these devices emphasized the synthesis of dyes with enhanced light-absorbing capabilities, but slow progress in the increase in efficiency has directed attention to the exploration into the modification of the TiO2 nanostructure. Up to this point, the most efficient electrodes in DSSC devices have consisted of 10 micron-thick mesoporous TiO2 film with an interconnected network of 15-20nm particles. This type of structure has shown to impart a large enough surface area for efficient light absorption and charge formation, but the random distribution of nanometer-sized particles is thought to be the limiting factor for enhanced electron transport, hindering further progress in achieving higher efficiencies. Our research utilizes TiO2 nanorods in an attempt to explore and compare the electron transport pathways associated with 1) a random distribution of nanoparticles and 2) a straightforward arrangement of nanorods within the TiO2 nanostructure. It is assumed that a more ordered structure of nanorods would minimize inefficient electron percolation pathways and improve ion diffusion at the TiO2-dye-electrolyte interface by eliminating the randomization of the particle network, by increasing contact points for good electrical connection, and by decreasing small necking points that have shown to develop between adjacently-bound particles in the current TiO2 nanoparticle structure after sintering. The current-voltage (I-V) behavior of three solar cell electrode structures consisting of (1) TiO2 nanoparticle film, (2) TiO2 nanoparticle-nanorod film, and (3) TiO2 nanorod film were compared and analyzed to determine whether the nanorod structure provided a more efficient pathway for effective electron conduction. SEM analysis was also done to examine the structural alignment and morphology of each TiO2 electrode.

CO2 capture from pre-combustion syngas in the temperature range of 250-400°C is highly desirable from an energy efficiency perspective. Thermodynamically, MgO is a promising material for CO2 capture, but the gas-solid reaction to produce MgCO3 is kinetically slow due to high lattice energy. We report here fast CO2 absorption over a solid MgO-molten nitrate/nitrite aggregate through phase transfer catalysis, in which the molten phase serves as both a catalyst and reaction medium. Reaction with CO2 at the gas-solid-liquid triple phase boundary results in formation of MgCO3 with significant reaction rate and a high conversion of MgO. This methodology is also applicable to other alkaline earth oxides, inspiring the design of absorbents which require activation of the bulk material.

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