Self-reactivated mesostructured Ca-Al-O composite for enhanced high-temperature CO2 capture and carbonation/calcination cycles performance.

In this study, highly efficient high-temperature CO2 sorbents of calcium aluminate (Ca-Al-O) mesostructured composite were synthesized using presynthesized mesoporous alumina (MA) as a porous matrix to react with calcium nitrate through a microwave-assisted process. Upon annealing at 600 °C, a highly stable mesoporous structure composed of poorly crystalline Ca12Al14O33 phase and the CaO matrix was obtained. The Ca-Al-O mesostructured sorbents with a Ca(2+)/Al(3+) ratio of 5:1 exhibit an enhanced increasing CO2 absorption kinetics in the CO2 capture capacity from 37.2 wt % to 48.3 wt % without apparent degradation with increasing carbonation/calcination cycling up to 50 at 700 °C due to the strong self-reactivation effect of the mesoporous Ca-Al-O microstructure. Remarkable improvements in the CaO-CaCO3 conversion attained from the mesostructured Ca-Al-O composite can be explained using the concept combined with available mesoporous structure and Ca12Al14O33 phase content. However, a high Ca(2+)/Al(3+) =8:1 Ca-Al-O composite causes degradation because the pores become blocked and partial sintering induces CaO agglomeration.

CO2 sorbents with scaffold-like Ca-Al layered double hydroxides as precursors for CO2 capture at high temperatures.

A highly stable high-temperature CO2 sorbent consisting of scaffold-like Ca-rich oxides (Ca-Al-O) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing Ca-Al-NO3 layered double hydroxide (LDH) precursors through a sol-gel process with Al(O(i)P)3 and Ca(NO3)2 with Ca(2+)/Al(3+) ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca(2+)/Al(3+) ratios of 2:1. However, both LDH and Ca(OH)2 phases were produced at higher ratios. Both TEM and SEM observations indicated that the Ca-Al-NO3 LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 °C, a highly stable porous network structure of the CaO-based Ca-Al-O mixed oxide (CAMO), composed of CaO and Ca12Al14O33, was still present. The CAMO exhibited high specific surface areas (up to 191 m(2)g(-1)) and a pore size distribution of 3-6 nm, which allowed rapid diffusion of CO2 into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO2 absorption at 700 °C. Thermogravimetric analysis results indicated that a CO2 capture capacity of approximately 49 wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 °C for 5 min. Also, 94-98% of the initial CO2 capture capability was retained after 50 cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments.

Chitosonic® Acid as a Novel Cosmetic Ingredient: Evaluation of its Antimicrobial, Antioxidant and Hydration Activities.

Chitosonic® Acid, carboxymethyl hexanoyl chitosan, is a novel chitosan material that has recently been accepted by the Personal Care Products Council as a new cosmetic ingredient with the INCI (International Nomenclature of Cosmetic Ingredients) name Carboxymethyl Caprooyl Chitosan. In this study, we analyze several important cosmetic characteristics of Chitosonic® Acid. Our results demonstrate that Chitosonic® Acid is a water-soluble chitosan derivative with a high HLB value. Chitosonic® Acid can form a nano-network structure when its concentration is higher than 0.5% and can self-assemble into a nanosphere structure when its concentration is lower than 0.2%. Chitosonic® Acid has potent antimicrobial activities against gram-positive bacteria, gram-negative bacteria and fungus. Chitosonic® Acid also has moderate DPPH radical scavenging activity. Additionally, Chitosonic® Acid exhibits good hydration activity for absorbing and retaining water molecules with its hydrophilic groups. From a safety point of view, Chitosonic® Acid has no cytotoxicity to L-929 cells if its concentration is less than 0.5%. Moreover, Chitosonic® Acid has good compatibilities with various normal cosmetic ingredients. Therefore, we propose that Chitosonic® Acid has the potential to be a widely used ingredient in various types of cosmetic products.

Synthesis, characterization, and CO(2) adsorptive behavior of mesoporous AlOOH-supported layered hydroxides.

A novel CO(2) solid sorbent was prepared by synthesizing and modifying AlOOH-supported CaAl layered double hydroxides (CaAl LDHs), which were prepared by using mesoporous alumina (γ-Al(2)O(3)) and calcium chloride (CaCl(2)) in a hydrothermal urea reaction. The nanostructured CaAl LDHs with nanosized platelets (3-30 nm) formed and dispersed inside the crystalline framework of mesoporous AlOOH (boehmite). By calcination of AlOOH-supported LDHs at 700 °C, the mesoporous CaAl metal oxides exhibited ordered hexagonal mesoporous arrays or uniform nanotubes with a large surface area of 273 m(2) g(-1) , a narrow pore size distribution of 6.2 nm, and highly crystalline frameworks. The crystal structure of the calcined mesoporous CaAl metal oxides was multiphasic, consisting of CaO/Ca(OH)(2), Al(2)O(3), and CaAlO mixed oxides. The mesoporous metal oxides were used as a solid sorbent for CO(2) adsorption at high temperatures and displayed a maximum CO(2) capture capacity (≈45 wt %) of the sorbent at 650 °C. Furthermore, it was demonstrated that the mesoporous CaAl oxides showed a more rapid adsorption rate (for 1-2 min) and longer cycle life (weight change retention: 80 % for 30 cycles) of the sorbent because of the greater surface area and increased number of activated sites in the mesostructures. A simple model for the formation mechanism of mesoporous metal oxides is tentatively proposed to account for the synergetic effect of CaAl LDHs on the adsorption of CO(2) at high temperature.

Ca-rich Ca-Al-oxide, high-temperature-stable sorbents prepared from hydrotalcite precursors: synthesis, characterization, and CO2 capture capacity.

We present the design and synthesis of Ca-rich Ca-Al-O oxides, with Ca(2+)/Al(3+) ratios of 1:1, 3:1, 5:1, and 7:1, which were prepared by hydrothermal decomposition of coprecipitated hydrotalcite-like Ca-Al-CO(3) precursors, for high-temperature CO(2) adsorption at 500-700 °C. In situ X-ray diffraction measurements indicate that the coprecipitated, Ca-rich, hydrotalcite-like powders with Ca(2+)/Al(3+) ratios of 5:1 and 7:1 contained Ca(OH)(2) and layered double hydroxide (LDH) phases. Upon annealing, LDH was first destroyed at approximately 200 °C to form an amorphous matrix, and then at 450-550 °C, the Ca(OH)(2) phase was converted into a CaO matrix with incorporated Al(3+) to form a homogeneous solid solution without a disrupted lattice structure. CaO nanocrystals were grown by thermal treatment of the weakly crystalline Ca-Al-O oxide matrix. Thermogravimetric analysis indicates that a CO(2) adsorption capacity of approximately 51 wt. % can be obtained from Ca-rich Ca-Al-O oxides prepared by calcination of 7:1 Ca-Al-CO(3) LDH phases at 600-700 °C. Furthermore, a relatively high CO(2) capture capability can be achieved, even with gas flows containing very low CO(2) concentrations (CO(2)/N(2) = 10 %). Approximately 95.6 % of the initial CO(2) adsorption capacity of the adsorbent is retained after 30 cycles of carbonation-calcination. TEM analysis indicates that carbonation-promoted CaCO(3) formation in the Ca-Al-O oxide matrix at 600 °C, but a subsequent desorption in N(2) at 700 °C, caused the formation CaO nanocrystals of approximately 10 nm. The CaO nanocrystals are widely distributed in the weakly crystalline Ca-Al-O oxide matrix and are present during the carbonation-calcination cycles. This demonstrates that Ca-Al-O sorbents that developed through the synthesis and calcination of Ca-rich Ca-Al LDH phases are suitable for long-term cyclic operation in severe temperature environments.

Characterization and structure evolution of Ca-Al-CO3 hydrotalcite film for high temperature CO2 adsorption.

In this work, monodispersed layered double hydroxide (Ca-Al LDHs) nanoparticles were synthesized by hydrothermal coprecipitation. Uniform thin films of layered double hydroxide on porous anodic aluminum oxide (AAO) substrates were formed by a direct precipitation process in a homogeneous suspension containing monodispersed Ca-Al layered double hydroxide nanoparticles. It was found that the formation of a designed hydrotalcite-like phase is strongly dependent on the [Ca(2+)]/[Al(3+)] ratios, and that a minor CaCO3 phase could possibly form simultaneously, which is attributed to the greater insolubility of CaCO3 and the incompatibility of the ionic size of Al and Ca. The optimal CO2 adsorption capacity appears in the layered Ca-OH-Al structure with the composition ratio of 3:1. Furthermore, the CO2 adsorption mechanism varies with treatment temperature. Below 400 degrees C, the CO2 adsorption is attributed to the LDH structure with a large surface area and pore volume, but above that the adsorption is due to the formation of CaCO3 and CaO. The permeation behavior and CO2 absorption can be explained by a preferable chemical and physical absorption of CO2 on the layered double hydroxide and porous structure of the membrane.

Synthesis and characterization of mesoporous Gd2O3 nanotube and its use as a drug-carrying vehicle.

Gd2O3 nanotubes were constructed for the first time by assembling highly crystalline Gd2O3 nanoparticles through the use of combined soft template and sol-gel methods. Amphiphilic block copolymer was used as structure-directing agent and gadolinium isopropoxide as inorganic precursor in non-aqueous solution. The amphiphilic copolymer molecules are known to undergo self-organization above a critical micelle concentration, forming micellular architecture that further provides a structurally ordered active site for the nucleation and growth of Gd monomers. The resulting self-assembly of the Gd2O3 nanocrystals led to the formation of Gd2O3 tubular nanostructure after pyrolytic removal of the template. Transmission electron microscopy analysis indicated a mesoporous channel array along the [110] direction of the nanotubes where the wall of nanotube is well organized by the assembly of a highly crystalline framework of Gd2O3 nanocrystals. This Gd2O3 nanotube exhibited weak superparamagnetic property and was found to be able to carry and elute a model molecule, i.e. ibuprofen (IBU), in a controllable manner via an external magnetic field. The mechanism of IBU release from the nanotubes with and without the use of magnetic stimulus was proposed.

Morphology of nanostructured platinum in mesoporous materials-effect of solvent and intrachannel surface.

An intrachannel surface of host silica was functionalized through the reaction of surface silanol groups with silanes to generate a monolayer of positively charged groups, and together with the strongly adsorbed and negatively charged PtCl6(2-), resulting in nanostructured platinum-mesoporous silica composites. The highly dispersed Pt nanoparticles and nanonetworks are fabricated from (CH3O)3Si(CH2)3N(CH3)3+Cl- functionalized mesoporous silica MCM-48 with H2PtCl6 in ethanol and water solvent, and characterized by PXRD, XAS, TEM, and N2 adsorption. The solvent of H2PtCl6 solution is found to affect the mobility of Pt precursors and the resulting morphology of nanostructured metallic Pt. The effect of the intrachannel surface properties on the incorporation and the morphology of nanostructured Pt on the deposition of Pt(NH3)4Cl2 and H2PtCl6 on Al-doped or C-coated mesoporous silica MCM-41 is also studied relative to that on pure silica MCM-41.