Single crystals of β1 and polycrystals of β2 of POP and SOS were obtained from acetonitrile solution. The crystallization behavior of the two polymorphs was almost the
same in POP and SOS; rapid cooling of the solution preferentially crystallized the metastable β2 form, and the most stable β1 form crystallized in a very low solute concentration at the expense of β2, via solution-mediated transformation. The single crystal of β2 revealed needle-like irregular shape, whereas well-defined slender rhombic shape was observed in β1. The solubilities of the β1 forms of POP and SOS in tetradecane solution were precisely measured in a temperature range of 10∼20°C. This study showed
that the solvent crystallization was the single way to grow the β1 crystal, since melt-cooling and melt-mediated transformation did not crystallize β1 both in POP and SOS.
Presented at 1988 AOCS Annual Meeting at Phoenix. 相似文献
Molecular properties of polymorphic forms of gondoic acid [cis-C20:1Δ11ω9 (GOA)] have been studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), optical microscopy, and
Raman scattering, in comparison to those of six principal unsaturated fatty acids: oleic acid [cis-C18:1Δ9ω9 (OA)], erucic acid [cis-C22:1Δ13ω9 (ERA)], petroselinic acid [cis-C18:1Δ6ω12 (PSA)], asclepic acid [cis-C18:1Δ11ω7 (APA)], palmitoleic acid [cis-C16:1Δ9ω7 (POA)], and elaidic acid [trans-C18:1Δ9ω9 (ELA)]. In addition, phase behavior of binary mixtures of GOA and APA and OA was examined by XRD and DSC. The polymorphic
structures of GOA are quite similar to those of APA, ERA, POA, and partly to OA. In particular, DSC and Raman scattering studies
have shown that gondoic acid exhibits conformational disordering on heating at the ω-chain, a chain segment between the double
bond and CH3 group, as a transition from all-trans (γ form) to gauche-rich (α form) conformations. A miscible mixing phase was observed in the mixture of GOA and APA, yet eutectic phases were
observed in the GOA and OA mixtures. This is a remarkable contrast because the binary mixture systems of varying combinations
of cis-unsaturated fatty acids examined so far exhibited either eutectic nature or molecular compound formation. It is expected
that specific molecular interactions between GOA and APA that originate from the equivalence of the length of the Δ-chain,
the chain segment between the cis-double bond and COOH group, and also from the presence of the γ-α order-disorder transformation would be operating to form
the miscible mixing phase. 相似文献
Photocatalytic activities for water decomposition were examined for photocatalysts using hexa- and octa-titanates and TiO2(B) with different tunnel space in the structure. Using RuO2 as promoter, M2Ti6O13 (M = Li, Na, K, Rb) showed the stoichiometric production of Hz and O2 except for Li, whereas H2Ti8O17 and TiO2(B) had very low activity producing only hydrogen as a product. The effects of promoters on Na2Ti6O13 showed that the activity increased in the order of RuO2 > RuO2 + IrO2 > IrO2 > RuO2 + Pt > MnO2. These effects along with other related ones are discussed: it emerges that the presence of the tunnels is important for the achievement of high photocatalytic activity. 相似文献
TiN supported molybdenum sulfide catalysts showed much higher activity for cleavage of C-C bonds than oxide supported molybdenum sulfide catalysts, indicating the possibility of a new generation of supports for hydroprocessing catalysts. 相似文献
In the electrochemical system with liquid-liquid interface, intense local convections by the resonance with potential pulses take place. Therefore, with laser beam scattering, temporal movement of the water-mercury interface was observed. As a result, the scattering efficiency showed non-linear oscillation.
Such non-linear response could be controlled by potential pulse height. As the potential height was increased, new scattering peaks in the oscillation emerged, which was expected of a kind of bifurcation phenomenon. From these results, phase portrait, Poincarè section, correlation dimension of the strange attractor and the largest Lyapunov exponent of the trajectories were obtained. Consequently, it was concluded that all the parameters indicate chaotic behavior of the resonance flow. 相似文献
Silica-supported alkaline earth oxides revealed excellent activity to convert acetic acid selectively into acetone in a vapor-phase fixed-bed flow system. Acetone was obtained through the cyclic formation of alkaline earth acetate followed by decomposition. Magnesium oxide should be supported on the silica surface without formation of magnesium silicate, which was inactive for the present reaction. Attempted syntheses of benzophenone and acetophenone are also described. 相似文献
Compacts of TiB2 with densities approaching 100% are difficult to obtain using pressureless sintering. The addition of SiC was very effective in improving the sinterability of TiB2. The oxygen content of the raw TiB2 powder used in this research was 1.5 wt%. X-ray photoelectron spectroscopy showed that the powder surface consisted mainly of TiO2 and B2O3. Using vacuum sintering at 1700°C under 13–0.013 Pa, TiB2 samples containing 2.5 wt% SiC achieved 96% of their theoretical density, and a density of 99% was achieved by HIPing. TEM observations revealed that SiC reacts to form an amorphous phase. TEM-EELS analysis indicated that the amorphous phase includes Si, O, and Ti, and X-ray diffraction showed the reaction to be TiO2+ SiC → SiO2+ TiC. Therefore, the improved sinterability of TiB2 resulted from the SiO2 liquid phase that was formed during sintering when the raw TiB2 powder had 1.5 wt% oxygen. 相似文献
Partially protonated alkaline mordenites showed higher activity per acid amount below 573 K than acidic zeolites for the selective
reduction of NO with C3H6 in the presence of O2, which can be related to a high concentration of NO3- species in the zeolite channels.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
The thermal decomposition of uranium peroxide hydrates, UO4·4H2O and UO4·2H2O, has been investigated by thermal analyses, X-ray diffraction study and infrared spectroscopy. As a result, it is concluded that the thermal decomposition of uranium peroxide hydrates proceeds in the following sequence: where 3 ≤ x ≤ 3.5. 相似文献