Crystallization of zeolite Beta in the presence of an anionic surfactant AESA.

Organic molecules are widely used as structure directing agents, mesopore generating agents or zeolite growth modifiers in the synthesis of various zeolites. However, the organic molecules used in zeolite synthesis are mostly positively charged cationic molecules, since the cationic group can balance the negative charge in the zeolite structure. Here we attempt for the first time to apply an anionic surfactant fatty alcohol polyoxyethylene ether ammonium sulfate (AESA) in the crystallization of zeolite Beta. It is found that both the crystallization process and the characteristics of the product were affected by the addition of AESA into the synthesis. Compared with that without AESA, it shows that the induction period was significantly prolonged for the synthesis of zeolite Beta with AESA, and the crystallinity and the completeness of the crystal were improved. The yield of the product was increased when AESA was used in the synthesis. The framework Si/Al ratio was increased when AESA was added into the synthesis gel, which could be due to the fact that the anionic surfactant AESA facilitated the formation of Si-O-Si bonds and hindered the combination of the negatively charged aluminum species to silicon species to form Si-O-Al bonds, thus increasing the incorporation of Si and reducing the incorporation of Al into the framework. Moreover, we demonstrate an ability to enrich chiral polymorph-A in zeolite Beta by using AESA in the crystallization, with the proportion of polymorph-A in the as synthesized zeolite Beta reaching 77.9%. It is reported that AESA did not remain in the structure of zeolite Beta when the crystallization was completed, which implies that AESA plays a role of zeolite growth modifiers during the crystallization. The results of this study suggest that anionic surfactants can be used in zeolite synthesis to optimize the crystallization process and achieve zeolites with the desired properties.

Macroscopic rods from assembled colloidal particles of hydrothermally carbonized glucose and their use as templates for silicon carbide and tricopper silicide.

Self-aggregated colloids can be used for the preparation of materials, and we studied long rod-like aggregates formed on the evaporation of water from dispersed particles of colloidal hydrochar. The monodispersed hydrochar particles (100-200 nm) were synthesized by the hydrothermal carbonization of glucose and purified through dialysis. During the synthesis they formed colloidal dispersions which were electrostatically stable at intermediate to high pH and at low ion strengths. On the evaporation of water, macroscopically large rods formed from the dispersions at intermediate pH conditions. The rods formed at the solid-water interface orthogonally oriented with respect to the drying direction. Pyrolysis rendered the rods highly porous without qualitatively affecting their shape. A Cu-Si alloy was reactively infiltrated into the in-situ pyrolyzed hydrochars and composites of tricopper silicide (Cu3Si)-silicon carbide (SiC)/carbon formed. During this process, the Si atoms reacted with the C atoms, which in turned caused the alloy to wet and further react with the carbon. The shape of the underlying carbon template was maintained during the reactions, and the formed composite preparation was subsequently calcined into a Cu3Si-SiC-based replica of the rod-like assemblies of carbon-based colloidal particles. Transmission and scanning electron microscopy, and X-ray diffraction were used to study the shape, composition, and structure of the formed solids. Further studies of materials prepared with reactive infiltration of alloys into self-aggregated and carbon-based solids can be justified from a perspective of colloidal science, as well as the explorative use of hydrochar prepared from real biomass, exploration of the compositional space in relation to the reactive infiltration, and applications of the materials in catalysis.

Core-Shell and Hollow Particles of Carbon and SiC Prepared from Hydrochar.

The applications of silicon carbide (SiC) include lightweight materials with thermal shock resistance. In this study, core-shell C-SiC particles were synthesized by compacting and rapidly heating a hydrochar from glucose by using strong pulsed currents and infiltration of silicon vapor. Hollow particles of SiC formed on removing the carbon template. In contrast to related studies, we detected not only the pure 3C polytype (ß-SiC) but also significant amounts of the 2H or the 6H polytypes (α-SiC) in the SiC.

CO Adsorption Performance of CuCl/Activated Carbon by Simultaneous Reduction⁻Dispersion of Mixed Cu(II) Salts.

CO is a toxic gas discharged as a byproduct in tail gases from different industrial flue gases, which needs to be taken care of urgently. In this study, a CuCl/AC adsorbent was made by a facile route of physically mixing CuCl2 and Cu(HCOO)2 powder with activated carbon (AC), followed by heating at 533 K under vacuum. The samples were characterized by X-ray powder diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), N2 adsorption/desorption, and scanning electron microscopy (SEM). It was shown that Cu(II) can be completely reduced to Cu(I), and the monolayer dispersion threshold of CuCl on AC support is 4 mmol·g-1 AC. The adsorption isotherms of CO, CO2, CH4, and N2 on CuCl/AC adsorbents were measured by the volumetric method, and the CO/CO2, CO/CH4, and CO/N2 selectivities of the adsorbents were predicted using ideal adsorbed solution theory (IAST). The obtained adsorbent displayed a high CO adsorption capacity, high CO/N2, CO/CH4, and CO/CO2 selectivities, excellent ad/desorption cycle performance, rapid adsorption rate, and appropriate isosteric heat of adsorption, which made it a promising adsorbent for CO separation and purification.

Iron oxide nanoparticles embedded in activated carbons prepared from hydrothermally treated waste biomass.

Particles of iron oxide (Fe3O4 ; 20­40 nm) were embedded within activated carbons during the activation of hydrothermally carbonized (HTC) biomasses in a flow of CO2. Four different HTC biomass samples (horse manure, grass cuttings, beer production waste, and biosludge) were used as precursors for the activated carbons. Nanoparticles of iron oxide formed from iron catalyst included in the HTC biomasses. After systematic optimization, the activated carbons had specific surface areas of about 800 m2g1. The pore size distributions of the activated carbons depended strongly on the degree of carbonization of the precursors. Activated carbons prepared from highly carbonized precursors had mainly micropores, whereas those prepared from less carbonized precursors contained mainly mesopores. Given the strong magnetism of the activated carbon­nano-Fe3O4 composites, they could be particularly useful for water purification.

Cobalt selenium oxohalides: catalysts for water oxidation.

Two new oxohalides Co4Se3O9Cl2 and Co3Se4O10Cl2 have been synthesized by solid state reactions. They crystallize in the orthorhombic space group Pnma and the monoclinic space group C2/m respectively. The crystal structure of the two compounds are made up of similar building blocks; Co4Se3O9Cl2 is made up of [CoO4Cl2], [CoO5Cl] and [SeO3] polyhedra and Co3Se4O10Cl2 is made up of [CoO4Cl2] and [SeO3] polyhedra. As several Co-containing compounds have proved to be good catalysts for water oxidation, the activities of the two new compounds were compared with the previously found oxohalide Co5Se4O12Cl2 in reference to CoO and CoCl2. The one electron oxidant Ru(bpy)3(3+) was used as oxidizing species in a phosphate buffer and it was found that the activities of the oxohalide species were in between CoO and CoCl2. The roles of Cl(-) and PO4(3-) ions are discussed.