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In this study, Pb(Mg1/3Nb2/3)0.65Ti0.35O3 (PMNT) ceramics were prepared by a water-based gel-casting method. The gel-cast mixtures were dried through soaking in acetone with different soaking times...

Ni/α-Al2O3 catalysts containing CaZrO3 nanoparticles as a promoter were prepared by sequential impregnation for H2 production from steam-methane reforming. The effects of different loadings of CaZrO3 nanoparticles from 0 to 15 wt% on the catalytic performance of Ni/α-Al2O3 catalysts in steam-methane reforming were studied. The Ni/α-Al2O3 catalysts containing 15 wt% CaZrO3 nanoparticles provided the highest H2 yield due to facilitative steps of enormous steam adsorption-dissociation at the sites of oxygen vacancies on the surface of CaZrO3 nanoparticles. The existence of facilitative steps created additional H+ and OH− enhancing both H2 yield and the gasification of deposited carbon, respectively. The tests of steam-methane reforming at low S/C ratio of 1/3 for 97 h revealed that the catalytic performance of CaZrO3-modified Ni/α-Al2O3 catalysts was higher than that of the unmodified Ni/α-Al2O3 catalyst. Interestingly, at high S/C ratio of 3 excessive steam adsorption at the oxygen vacancies on CaZrO3 nanoparticles resulted in highly competitive adsorption between steam and methane decreasing CH4 dissociation. The results suggested that in the steam-methane reforming, optimum S/C ratios for the CaZrO3-modified Ni/α-Al2O3 catalysts were relatively lower than those for the unmodified Ni/α-Al2O3 catalyst due to excellent steam adsorption-dissociation capability for CaZrO3 nanoparticles.

Disc alumina membrane supports were formed through agar gelcasting method. The agar gelcasting was expected to be environmentally-friendly forming technique using simple equipment. Final agar amounts (0.25 – 0.75wt%) in gelcasting mixtures were varied to find the optimum condition of shaping and the desired microstructure of sintered supports. The gelcasting mixtures were prepared from non-reactive grade Al2O3 and porcelain at the ratio of 98.5:1.5 by weight. The porcelain addition allowed the membrane support to have high strength at lower sintering temperature. When the final agar amounts increased from 0.25 to 0.75wt%, the dried, gelcast supports tended to have rough surface and subsequently resulting in crack. TGA profiles confirmed that there was interaction between agar chains and kaolin particles on cooling the gelcast supports leading to different microstructures after sintering. The final agar amount of 0.5 wt% provided the highest porosity of 48.9% and the highest relative density of 61.5%. Additionally, the average pore size of 1.5 µm was obtained at the final agar amount of 0.5 wt% suitable for using as asymmetric membrane support or microfiltration membrane.

In this work, Pd metal layer was deposited on in-house prepared macro-porous disc alumina support by electroless plating. The in-house prepared support were repeatedly seeded for 4 cycles to obtain Pd nuclei before repeatedly electroless plated for 4 cycles. The 4-cycle Pd plating was to obtain the full layer of Pd metal observing from changing support surface from black to light grey. The plated membrane samples were annealed at 550 and 600oC for using in high-temperature H2 separation. The annealed samples were observed morphology by SEM and confirm the occurrence of Pd layer with EDS. The SEM images revealed incomplete Pd layer. The over 4 cycles of plating were needed to form complete Pd layer since the numerous Pd ions diffused into macro-pores alumina support instead of depositing on the surface of macro-porous support. The higher annealing temperature of 600oC led to denser layer of Pd with the presence of small cracks due to the contraction of Pd particles.

Ni catalysts supported on (CaO–ZrO 2 )-modified γ-Al 2 O 3 were prepared by sequential impregnation. The effects of varied CaO to ZrO 2 mole ratios at 0, 0.20, 0.35, 0.45, and 0.55 on the activity and stability of the modified Ni catalysts were studied. As a result of using CaO–ZrO 2 as a promoter, each catalyst contained CaO–ZrO 2 at only 5%. γ-Al 2 O 3 used as support was modified by CaO–ZrO 2 before the deposition of nickel oxide. The addition of CaO–ZrO 2 at an optimum ratio was expected to improve the stability of Ni catalysts due to the decrease of carbon formation resulting from carbon gasification. All the fresh catalysts were characterized by ICP, XRD, BET surface area, TGA in H 2 , and TPR before catalytic testing in steam methane reforming at 600 °C. The spent catalysts were examined by TEM and TGA to observe the catalysts deactivation. The identification of CaO–ZrO 2 phases indicated that CaO and ZrO 2 reacted with each other to be monoclinic solid solution ZrO 2 , CaZr 4 O 9 , CaZrO 3 , and CaO corresponding to the phase diagram of CaO–ZrO 2 . The existence of CaZrO 3 for 0.55 mol ratio of CaO/ZrO 2 enhanced activity in steam methane reforming because oxygen vacancies in CaZrO 3 greatly preferred the water adsorption creating the favorable conditions for carbon gasification and, then, water gas shift. The prominence and continued existence of these two reactions on the Ni catalysts leads to the particular increase of H 2 yield. Moreover, the increasing amount of CaZrO 3 in the Ni catalysts significantly improved carbon gasification. However, the Ni catalysts with CaZrO 3 showed whisker carbon after catalytic testing; this carbon specie has not been tolerated in steam methane reforming. Therefore, these results significantly differed from the hypothesis.