In situ hydrothermal synthesis

Gavalas et al. [7] prepared ZSM-5 membranes onto porous a-alumina disks by in-situ hydrothermal synthesis at 175°C. The zeolite layers were formed on the bottom face of disks placed horizontally near the air-liquid interface of clear synthesis solutions. The films grown at the optimized conditions were about 10 pm thick and consisted of well-intergrown crystals of about 2 pm in size Pure gas permeation measurements of the best preparations yielded hydrogen isobutane and butane isobutane ratios of 151 and 18 at room temperature and of 54 and 31 at 185°C, respectively. 

Shan Z, van Kooten WEJ, Oudshoom OL, Jansen JC, van Bekkum H, van den Bleek CM, and Calls HPA. Optimization of the preparation of binderless ZSM-5 coatings on stainless steel monoliths by in situ hydrothermal synthesis. Micropor Mesopor Mater 2000 34 81-91. 

Silicalite-1 membranes, supported on porous alumina ceramic discs, have been prepared by two different routes. In the first the zeolite membrane has been formed by in situ hydrothermal synthesis. Secondly a layer has been formed by controlled filtration of zeolite colloids. To optimise membrane stability, conditions have been established in which penetration of zeolite into the support sublayer occurs. The pore structure of these membranes has been characterised by a combination of SEM and Hg-porosimetry. The permeabilities of several gases have been measured together with gas mbeture separation behaviour. 

Shi F, et al. Roselike microstructures formed by direct in situ hydrothermal synthesis from superhydrophilicity to superhydrophobicity. Chem Mater 2005 17(24) 6177-80. 

Membrane Preparation by In Situ Hydrothermal Synthesis Without Seeding... 

Wang, D., Guo, Z., Chen,Y, Hao,J., Liu,W, 2007a. In situ hydrothermal synthesis of nanola-meUate CaTi03 with controllable structures and wettability. Inorg. Chem. 46, 7707. 

The presence of triethylenetetramine in the hydrothermal synthesis of open-framework zinc phosphates results in a number of frameworks with one- to three-dimensional structures. The structures include one-dimensional ladders, two-dimensional layer structures, and one structure where the tetramine is bound to the zinc center. The structural type was highly sensitive to the relative concentration of the amine and phosphoric acid.411 Piperazine and 2-methylpiperazine can be used as templating molecules in solvothermal syntheses of zinc phosphates. The crystallization processes of the zinc compounds were investigated by real time in situ measurements of synchrotron X-ray powder diffraction patterns.412... 

Porous materials can also be coated with zeolite films by direct synthesis. For example, microcellular SiOC ceramic foams in the form of monoliths were coated on their cell walls with thin films of silicalite-1 and ZSM-5 using a concentrated precursor solution for in situ hydrothermal growth (Fig. 9).[62] The zeolite-coated monoliths show a bimodal pore system and are thermally stable to at least 600 °C. A related strategy is based on the conversion of macroporous Vycor borosilicate glass beads, having pores of about 100 nm, to MFI-type zeolite-containing beads retaining the same macroscopic shape.[63] This conversion was achieved by hydrothermal treatment with an aluminium source and a template such as TPABr. 

Table V presents a number of compounds that utilize two linker molecules (Rg. 31) to promote extended topologies, one of which in each being the oxalate anion. A component of the rational of this approach is to make use of small and somewhat predictable linker molecules (the oxalate) to direct local geometry, and then pair this entity with a separate linker molecule. For example, many Ln-oxalates display honeycomb layers like that seen in AOXNDH (Fig. 6) and the challenge is to then connect the layers (146). Also note, however, that many of these materials that contain oxalate linkers do so somewhat serendipitously. Of the stmctures listed in Table V, ACOXEV, EBAMUQ, JOVDON, JOVDUT, XUPBUF, and XUPCAM were all synthesized without oxalate precursors and instead display in situ oxalate formation and subsequent complexation. In situ ligand synthesis will be visited again in Section V.F (see sulfonates) and is not uncommon in hydrothermal Ln systems.

ADA/DEN] Adair, J. H., Denkewicz, R. P., Arriagada, F. J., Osseo-Asare, K., Precipitation and in situ transformation in the hydrothermal synthesis of crystalline zirconium dioxide, Ceram. Trans., 1, (1987), 135-145. Cited on page 409. 

Several reports related to CdS nanocrystals incorporated in PS matrix have been reported in the literature [200-202]. Zhao et al. described preparation of small nanoparticles of CdS by a hydrothermal procedure in an aqueous solution that yields transparent CdS/PS nanocomposite films [200]. CdS/PS nanocomposites were also prepared successfully using in-situ thermolysis synthesis of a cadmium thiolate precursor dispersed in the polymer [201, 202]. The preparation of CdS/PS via a thermolysis method has several interesting advantages with respect to the common methods of precipitation for example, the CdS precursor is easy to prepare and is stable under normal conditions. The thermal and structural properties of CdS/PS nanocomposites also were broadly investigated [201,202]. 

The template synthetic method is based on the in situ hydrothermal crystallization of clay mineral layers (from a gel) using selected water-soluble polymers as templates [61]. Template synthesis is essentially limited to water-soluble polymers, and the synthetic clay mineral formed under the conditions described by the authors is a poorly ordered fluorohectorite. On the other hand, the method is potentially capable of promoting the dispersion of silicate layers in a one-step process. 

Ye Q, Li YH, Song YM, Huang XF, Xiong RG, Xue Z (2005) A second-order nonlinear optical matmial prepared through in situ hydrothermal ligand synthesis. Inorg Chem 44 3618-3625... 

In situ Synthesis of Micro- and Mesoporous Al-MFI / MCM-41 like Phases with High Hydrothermal Stability. 

Over the last years the utilisation of supramolecular arrays of surfactant molecules as structure-directing templates [1] has been applied to the synthesis of numerous mesostructured aluminophosphates [2-11]. In most cases the preparations were carried out in aqueous systems under hydrothermal conditions, but tetraethylene glycol and/or unbranched primary alcohols were also used [2,4]. Several discussions have been made on the reaction mechanisms that are involved in the syntheses of mesostructured materials [1,12-15] and recently a number of in-situ investigations on the formation processes of mesostructured silica phases in aqueous media have been reported these studies employed small angle X-ray diffraction [16-19] as well as 2H, 13C, 29Si, and 8lBr NMR spectroscopy and polarised light optical microscopy [17]. 

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