Nanocrystalline tetragonal Li 2 ZrO 3 was prepared by a novel soft-chemistry route, resulting in powders with good properties for CO 2 capture at high temperatures. The CO 2 capture and regeneration properties of the material were investigated by a tapered element oscillating microbalance (TEOM) in a wide range of temperatures and partial pressures of CO 2 . The nanocrystalline tetragonal Li 2 ZrO 3 has superior CO 2 capture and regeneration properties compared to monoclinic Li 2 ZrO 3 prepared by solid-state synthesis. Moreover, the regeneration could be performed at a lower temperature, and a high stability of the CO 2 capture/regeneration capacity was observed. The nanocrystalline tetragonal Li 2 ZrO 3 opens new opportunities for the application of solid acceptors in CO 2 capture in both post-and precombustion processes in power generation.

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A novel method for producing nanosized Na2ZrO3 with well-controlled crystal phase has been developed, resulting in excellent kinetics for CO2 capture at high temperatures. The novel preparation method involves a soft-chemical route starting with the generation of a complex from zirconoxy nitrate and sodium citrate, followed by a strong exothermic reaction between nitrate and citrate during calcination in a controlled atmosphere. The in situ produced carbon during the calcination serves as a dispersant of the oxide, and subsequent carbon burnoff promotes the formation of nanocrystalline Na2ZrO3 with an open pore structure. The calcination temperature and atmosphere are very crucial for controlling the crystal phase of Na2ZrO3. The resulting sodium zirconate samples are characterized by XRD, N2 adsorption, Hg porosimetry, and SEM. A two-step calcination at 1073 K results mainly in the monoclinic phase, whereas one-step calcination at 1073 K or higher enhances the formation of the thermodynamically stable phase, namely hexagonal Na2ZrO3. A kinetic study of CO2 capture in a tapered element oscillating microbalance (TEOM) reactor has shown that the monoclinic Na2ZrO3 is much more active than its hexagonal counterpart. The ability to work at CO2 partial pressures as low as 0.025 bar, together with the excellent stability in multicycle capture/regeneration makes nanocrystalline Na2ZrO3 a very promising CO2 acceptor for different applications.

A series of Co-Ni catalysts, prepared from hydrotalcite (HT)-like materials by co-precipitation, has been studied for the hydrogen production by ethanol steam reforming. The total metal loading was fixed at 40% and the Co-Ni composition was varied (40-0, 30-10, 20-20, 10-30 and 0-40). The catalysts were characterized using X-ray diffraction, N 2 physisorption, H 2 chemisorption, temperature-programmed reduction, scanning transmission electron microscope and energy dispersive spectroscopy. The results demonstrated that the particle size and reducibility of the Co-Ni catalysts are influenced by the degree of formation of a HT-like structure, increasing with Co content. All the catalysts were active and stable at 575°C during the course of ethanol steam reforming with a molar ratio of H 2 O:ethanol = 3:1. The activity decreased in the order 30Co-10Ni [ 40Co * 20Ni-20Co * 10Co-30Ni [ 40Ni. The 40Ni catalyst displayed the strongest resistance to deactivation, while all the Co-containing catalysts exhibited much higher activity than the 40Ni catalyst. The hydrogen selectivities were high and similar among the catalysts, the highest yield of hydrogen was found over the 30Co-10Ni catalyst. In general, the best catalytic performance is obtained with the 30Co-10Ni catalyst, in which Co and Ni are intimately mixed and dispersed in the HT-derived support, as indicated by the STEM micrograph and complementary mapping of Co, Ni, Al, Mg and O.

A soft-chemistry route has been used for preparation of pure and promoted nanocrystalline lithium zirconate with different stoichiometries. The objective of this investigation has been to study the effect of different compositions on the acceptor and optimize the working properties of lithium zirconate. Special attention has been given to study the effect of different Li 2 O-ZrO 2 stoichiometries on the CO 2 capture rates. In addition, the partial substitution of Li 2 O with K 2 O as a promoter has been addressed. It has been found that both the capture rate and capacity of lithium zirconate depend considerably on the Li 2 O to ZrO 2 ratio. Enhanced capture rates are observed when a deficiency of Li 2 O is introduced. It is believed that the excess ZrO 2 might act as a dispersant and introduce more reactive boundaries. Moreover, the addition of K 2 O results also in improved capture rates due to the presence of molten carbonates, but lower capacities and poorer stability due to particle coarsening. The present of free ZrO 2 seems also beneficial for the stability of K 2 O-doped acceptors. Therefore, controlling the K:Li:Zr ratio has been found to be crucial for tailoring the properties of lithium zirconate. An optimized composition can result in an acceptor with enhanced capture rates, stability, and higher degree of utilization.