Masashi Shibata

Photostability enhancement of anionic natural dye by intercalation into hydrotalcite.

The aim of this study is the improvement of the photostability of several natural anionic dyes, carmine (CM), carthamus yellow (CY), and annatto dye (ANA), by complexation with hydrotalcite. The composite of the dyes and hydrotalcite is prepared by the coprecipitation method. CM is successfully intercalated in the hydrotalcite layer when the amount of introduced CM is large. The photostability of CM in CM/HT composites is superior to the CM adsorbed on silica surface. The effect of the stability enhancement is larger when the amount of introduced CM exceeds 0.23 g/g-host, or when the layer charge density of the hydrotalcite is larger. CY is also stabilized by complexation with hydrotalcite, whereas ANA is not stabilized by complexation with hydrotalcite. The photostability of an anionic natural dye can be improved by intercalation into the hydrotalcite layer, if the dye has a hydrophilic nature and a rather planar structure. The intercalated dye is stabilized by the protection from the attack of the atmospheric oxygen. In addition, contribution of the electrostatic interaction between the positively charged hydrotalcite layer and the intercalated anionic dye is also proposed.

Relationship between the hardness of an oil–wax gel and the surface structure of the wax crystals

Abstract The hardness of an oil–wax gel consisting of a solid paraffin wax (C32) and an oil varies with the oil properties. To clarify the mechanism of this hardness variation, a relationship between the gel hardness and the surface structure of the wax crystals has been studied. The hardness of the gel was affected by the oil polarity; a higher polarity oil produced a harder gel. It was found that in a higher polarity oil gel, the surface of the wax crystals were rougher and contained many steps. These steps on the crystal surface were probably induced by the disordering of the lamellar structure on a nanometer scale (small angle X-ray scattering (SAXS) measurement). Actually, when two kinds of paraffin waxes (C32 and C30) were admixed to purposely disorder the lamellar structure, the wax crystals possessed many steps even in a lower polarity oil and the obtained gel was harder compared with the single paraffin gels.

Stability against color fading of azo dyes encapsulated in Ca-aluminosilicate mesoporous substrates

Abstract Light-fastness properties of composites involving mesoporous calcium-modified aluminosilicate substrates (MCM-41 structure) and dye (Lithol Rubine B) were examined. High surface area Al-MCM-41 materials synthesized in the presence of Ca 2+ ions proved efficient hosts for Lithol Rubine B, yielding mesophase–dye composites with the highest light-fastness qualities, when compared to Ca-exchanged Al-MCM-41 aluminosilicates, to non composite pigment or to smectite–dye composites. The marked resistance of the new composites to fading was attributed to an optimized Ca–dye interaction favored by a controlled heating the Ca(OH) 2 -loaded mesoporous precursors, yielding tiny CaO particles, highly dispersed and retained onto the large internal surface of the substrate.

Synthesis of MFI titanosilicates from methylamine—TPABr media

A new synthesis route for MFI-type titanosilicates (TS-1) using methylamine along with tetrapropylammonium bromide (TPABr), silica or silicon tetrachloride and titanium tetrachloride, thus avoiding the use of costly TPAOH and Ti-alkoxide, has been investigated. The presence of titanium ions in the reaction gel slowed down the crystallization of MFI zeolites, while addition of hydrogen fluoride as a co-mineralizer into the gel dramatically improved the crystallization kinetics. Ti was readily incorporated into the zeolite framework, as confirmed by IR, XRD (unit cell expansion), and UV-vis spectroscopy. Reduced initial amounts of methylamine in the gel led to an increase of the apparent crystallization rate of the zeolite and to a remarkable decrease of the amount of framework Ti, suggesting that high concentration of methylamine is needed for the Ti incorporation into the growing MFI crystallites.

Rapid synthesis of MFI titanosilicates using in situ seeding method

Abstract A new synthesis method for a rapid crystallization of metallosilicates called the in situ seeding method was applied to the MFI titanosilicate (TS-1) synthesis. This method, which involves the preheating of the silicate gel and the consequent generation in situ of MFI silicate (silicalite-1) seeds before the addition of Ti source, dramatically accelerated the crystallization of TS-1 in methylamine medium. Ti ions were readily incorporated into 1he zeolite framework as confirmed by IR and the unit cell expansion measured by XRD. In comparison, the classical seeding method achieved under identical conditions yielded Ti-free silicalite-1 crystals. The optimal crystallimty of the preheated silicate gel for the in situ seeding method was evaluated to ca. 5%; a lower amount of silicalite-1 seeds led to a slower crystallization of TS-1, while crystallinity over 5% resulted in the continuation of the seed growth, leading eventually to crystalline silicalite-1.

Exploration of non conventional routes to synthesize MFI type titano- and (boro-titano)- zeolites

A wide series of non conventional, simple, rapid and inexpensive synthesis routes to prepare well crystallized (Ti)- and (Ti,B)-MFI zeolites from short chain alkylamine media have been explored. A new procedure involving an in situ seeding phenomenon was successfully used to considerably accelerate the crystallization. Ti is readily incorporated into the MFI framework, either alone or along with boron, as confirmed by XRD, IR, UV-vis and NMR techniques. Both ions show a homogeneous distribution throughout the zeolite crystallites grown in the presence of methylamine. B-Ti concentration gradients could appear when methylamine is admixed with fluoride ions used as co-mineralizing species.

Alkali-free synthesis of MFI type boro-titanosilicates using methylamine

A new synthesis route leading to a rapid crystallization of boro-titano MFI type zeolites from methylamine media has been explored. The principal advantage of this synthesis method is that the use of costly ingredients such as TPAOH and Ti- and Si-alkoxides can be avoided. Ti and B are readily incorporated into the MFI framework as confirmed by spot EDX analysis, IR, 11B-NMR and XPS. Preheating the borosilicate gel before mixing with titanium tetrachloride improves the (B,Ti)-MPI crystallization rate and prevents the formation of extraframework titanium dioxides.

Synthesis of alkali-free MFI borosilicates from methylamine-SiCl4 media

Abstract New synthesis routes leading to a rapid crystallization of alkali-free MFI type borosilicates from TPA-methylamine media have been thoroughly explored. When fumed silica was used as Si source, pure MFI borosilicate crystals were obtained rapidly. They stay hydrothermally stable for 20 days at 185°C. The evaluation of framework boron by 11 B-NMR along the growth process suggests a liquid phase transportation type mechanism. Crystallization using SiCl 4 as Si source is much slower, the hydrolysis of the chloride in methylamine being the rate limiting step for the nucleation to start. Appropriate amounts of boron species markedly increase the crystallization, probably by forming readily intermediate Bue5f8Oue5f8Si oligomeric associations in the reaction gel. This latter partly undergoes a solid state restructuring and, along with the remaining soluble Siue5f8B oligomers, yield crystalline MFI borosilicates.