Conventional hydrothermal

Ifrah, S., Kaddouri, A., Gelin, P. and Leonard, D. (2007) Conventional hydrothermal process versus microwave-assisted hydrothermal synthesis of La3 xAgxMn03 + s (x = 0, 0.2) perovskites used in methane combustion. Comptes Rendus Chimie, 10, 1216-1226. 

Table I illustrates the utility of DRUV-visible data in determining the surface structures involving Ti. Samples of TS-1 were prepared by three different methods or treatments. Samples 1 and 2 were prepared by conventional hydrothermal synthesis and sample 3 by synthesis in a fluoride medium. TS-2 was synthesized as reported (7). At least five bands could be discerned by deconvolution (Fig. 3), at 205, 228, 258, 290, and 330 nm. Band 1 at 205 nm is assigned to tetrahedral, tetrapodal Ti present in TS-1, TS-2, and Ti-beta. Band 5 at 330 nm is assigned to an...

Based on these observations, Wang and Caruso [237] have described an effective method for the fabrication of robust zeolitic membranes with three-dimensional interconnected macroporous (1.2 pm in diameter) stmctures from mesoporous silica spheres previously seeded with silicalite-1 nanoparticles subjected to a conventional hydrothermal treatment. Subsequently, the zeolite membrane modification via the layer-by-layer electrostatic assembly of polyelectrolytes and catalase on the 3D macroporous stmcture results in a biomacromolecule-functionalized macroporous zeolitic membrane bioreactor suitable for biocatalysts investigations. The enzyme-modified membranes exhibit enhanced reaction stability and also display enzyme activities (for H2O2 decomposition) three orders of magnitude higher than their nonporous planar film counterparts assembled on silica substrates. Therefore, the potential of such structures as bioreactors is enormous. 

Numerous microporous crystallines with various structure types have been successfully synthesized by using microwave irradiation in the last decade. Compared with conventional hydrothermal synthesis, microwave synthesis has many advantages, such as narrow particle-size distribution, controllable morphology, broader parent mixture composition, and short crystallization time. It can be expected that microwave synthesis will play an important role in the rapid, energy-saving, and continuous production of microporous compounds. 

P-35 - Synthesis of pure silica Beta by the conventional hydrothermal method... 

Pure silica Beta has been crystallized from alkali-free hydrogel containing tetraethyl-ammonium hydroxide and fumed silica at 413 K by the conventional hydrothermal synthesis method. Characterization has been done by XRD, IR, SEM, solid-state NMR, thermal analysis eind N2 adsorption. The results show that a highly crystalline pure silica Beta is formed. Si MAS NMR reveals that the pure silica Beta has a small number of sites originating from structural defects and almost half of sites are silanol groups. Thermal analysis shows that pure silica Beta possesses nonequivalent sites that are siloxy groups counterbalanced by TEA cations. 

Synthesis of gallosilicate zeolites [Ga]-beta, [Ga]-ZSM-5 and [Ga]-ZSM-12 was performed by dry-gel conversion (DGC) method. The crystallization of the dry gel was performed in presence of small amount of water, without which the crystallization failed. The method was convenient and as effective as conventional hydrothermal method. The samples were pure and highly crystalline, and showed characteristic of typical gallosilicate zeolites. 

A continuous microwave equipment (CME) has been developed to achieve a rapid and mass production for ZSM-5 and NaY zeolite. A precursor mixture for synthesis of ZSM-5 was prepared by mixing aluminosilicate gel with a nanoseed solution obtained under microwave irradiation, and pumped into the CME. Duration time in the CME was 5 min to accomplish the crystallization of ZSM-5 under microwave irradiation. For NaY zeolite, the precursor gel without nanoseeds was introduced into the CME and crystallization time was within 30 min. XRD and SEM results indicate that the structural properties of ZSM-5 and NaY zeolite obtained are similar to those obtained using batch-type microwave instrument and by conventional hydrothermal synthesis. 

The nonanuclear complex [La3Nig(iminodiacetate)6(OH)6(H20),2 has been prepared from Ni(N03)2 6H20, iminodiacetic acid and La(N03)3-6H20 at 100 °C in water using microwave heating or under standard reflux conditions. The complex ion was obtained in 40% yield after 30 min when using microwave heating, but under conventional hydrothermal conditions the yield was only 28.5% after 3 days. 

Comparison with Conventional Hydrothermal Synthesis Methods... 

Nanorods of SnS were prepared from hydrothermal reaction of SnCla 2H2O, hydrazine and thiourea at 180 °C for 23 h. The length of nanorods obtained by this method varied was from 1-2 pm and width was about 80 nm. Tbe as-prepared SnS nanorods were studied for hydrogen storage properties, and the maximum hydrogen absorption value was found to be 0.73 wt%. Yan et al. have studied the effect of conventional hydrothermal heating and microwave hydrothermal... 

Razak et al. [84] prepared Ba Sri cTi03 nanoparticles using a hydrothermal route and discussed the effects of the Ba Sr ratio, (Ba+Sr) Ti02 ratio, and the reaction time on the resultant particles. In addition, Deshpande and Khollam [85] synthesized BaojsSro.asTiOa nanoparticles by a microwave-hydrothermal route with faster crystallization, shorter synthesis time, and higher purity compared with the conventional hydrothermal route. 

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