Valentin Valtchev

Layer-by-layer preparation of zeolite coatings of nanosized crystals

In this contribution a new approach for preparation of zeolite films is described. Layer-by-layer self-assembly technique was employed for the preparation of zeolite coatings on negatively charged polystyrene beads. The procedure consists of two basic steps. In the first the beads were surface modified in order to facilitate adsorption of zeolite nanocrystals. A monolayer of crystals are then adsorbed on the bead surface. The number of deposition cycles control the thickness of zeolite coatings. Following this approach zeolite coatings of LTA, FAU, BEA and MFI type zeolites were prepared. Zeolite/polystyrene composites and the corresponding hollow zeolite spheres were characterized by SEM, TEM, X-ray diffraction, FTIR and thermogravimetric analyses.

Investigation of the ion-exchanged forms of the microporous titanosilicate K2TiSi3O9·H2O

The microporous titanosilicate K2TiSi3O9·H2O was subjected to ion exchange by the other alkaline cations and NH+4. The material can be totally exchanged by NH+4 and to different extents with the alkaline cations. The substitution of potassium leads to changes in the physicochemical properties of the material, like the thermal stability and water adsorption capacity as well as the unit cell parameters. The framework of the material is very flexible and needs stabilization provided by the cation–water complexes situated in the intracrystalline volume. Rietveld refinement showed that the two cationic positions, M1 and M2, are not equally exchangeable by the different cations. Small highly hydrated cations occupy preferentially the eight-membered ring channel, while the large cations occupy the seven-sided window.

Inductive effect of template containing UTD-1 seeds on the synthesis of zeolite SSZ-24

Abstract The addition of as-synthesized UTD-1 seeds to an SSZ-24 synthesis mixture accelerates the zeolite nucleation and leads to the formation of pure and well-crystallized SSZ-24. Computer modeling showed that the (001) cleavage plane in the UTD-1 framework fits perfectly to the (110) in the SSZ-24 structure. Subunits extracted from the (001) plane and stabilized by the bis-(pentamethylcyclopentadienyl) cobalt(III) complex may be viable precursors for zeolite SSZ-24.

Bioinspired porous materials

Publisher Summary This chapter focuses on the synthesis of bioinspired porous solids. The biological concept gives inspiration for creating a new generation of synthetic materials and devices with advanced structures and functions. Besides the astonishing ability of self-organization and complex functionality, biological specimens are attractive with their shapes and patterns that are unapproachable by the synthetic materials. The process of petrification is able to replicate the intimate organization of the biological structure. However, the petrification is a long and difficult to completely reproduce under laboratory conditions process. Hence, methods applicable to laboratory timescale and conditions will have to be developed in order to obtain molecular-scale replicas of biological templates. The incorporation of zeolites in morphological constructions issued from natural templates is the unique way to obtain a hierarchical porous structure exhibiting distinct micropores. Chemical compositions of bioinspired porous solids also vary in a very wide range as the oxides are largely presented. Among them, silica is probably the most broadly explored. Following the silica, probably the SiC and SiSiC ceramics issued from wood templates were the most widely studied. Noble metals, for instance Au, Pt, Pd, have been employed in the preparation of meso- and macroporous constructs. Finally, carbon and polymer replicas of biotemplates were obtained. Combinations of the above substances were also employed in the replication of biotemplates. Although, there is a long way to the use of inorganic porous material prepared via utilization of sacrificial natural templates, the interest in such materials is extremely high.