Sol-Gel Methods for the Production of Novel Catalytic Materials

Maier, Wilhelm F.; Bohnen, Frank M.; Heilmann, Jens; Klein, Stephan; Ko, Hee-Chan; Mark, Manfred J.; Thorimbert, Serge; Tilgner, Ingo-C.; Wiedorn, Michael

doi:10.1007/978-94-011-0337-4_2

Cited by 8 publications

(3 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In connection with our previous work on the use of amorphous zinc and cadmium sulfide as photocatalysts for novel chemical syntheses, we report here a new type of amorphous TiO 2 catalyst modified with platinum(IV) chloride, which belongs to the class of amorphous microporous metal oxides (AMM) developed for applications in heterogeneous catalysis , During the development of this synthesis, special emphasis was paid to the atomic or molecular isolation of the active center in the porous matrix of the bulk material.…”

Section: Introductionmentioning

confidence: 99%

Amorphous Microporous Titania Modified with Platinum(IV) ChlorideA New Type of Hybrid Photocatalyst for Visible Light Detoxification

et al. 1998

Self Cite

View full text Add to dashboard Cite

Amorphous microporous metal oxides of titanium (AMM-Ti) modified with a few percent of a platinum(IV) halide have been prepared by a sol-gel procedure and characterized by various surface analytical methods. By these methods the metal salt is homogeneously distributed in an almost exclusively amorphous powder of high specific surface area (160-200 m 2 /g) and a pore size of 0.8 nm. From the coordination number of 4.3 and a Pt-Cl distance of 2.28 Å, as calculated from extended X-ray absorption fine structure results, we conclude that the platinum salt is present as PtCl 4 . The hybrid sample (Pt(IV)/AMM-Ti) catalyzes the photodegradation of 4-chlorophenol with visible light. Apparent disappearance quantum yields decrease from 8.6 × 10 -3 at 335 nm to 4.5 × 10 -3 at 366 nm and 2.8 × 10 -3 at 400 nm; lower values of 1.6 × 10 -3 and 1.3 × 10 -3 are found at 436 and 546 nm, respectively. The quantum yield at both 366 and 436 nm decreases linearly with the square root of the incident photon flux, suggesting increasing recombination of the photogenerated charge carriers. We postulate that the photocatalytic activity of Pt(IV)/AMM-Ti originates from local excitation of the platinum(IV) chloride chromophore, affording a halogen atom and Pt(III) as intermediate species. Charge-trapping by the titania matrix generates reducing and oxidizing surface sites from which subsequent photodegradation proceeds. Good photostability of Pt(IV)/AMM-Ti is demonstrated by repeated use of the photocatalyst.

show abstract

Section: Introductionmentioning

confidence: 99%

Amorphous Microporous Titania Modified with Platinum(IV) ChlorideA New Type of Hybrid Photocatalyst for Visible Light Detoxification

et al. 1998

Self Cite

View full text Add to dashboard Cite

show abstract

“…During the initial process of hydrolysis, the correlation of pore volume and specific surface area of titanium silicates with pH and water content were studied by Yu & Wang [25]. The narrow pore size distribution were often provided by the condensation reactions for gelation at low temperatures, mild drying of the gel, and a slow temperature increase during calcinations [26].…”

Section: Sol-gel Methods For the Production Of Porous Oxidesmentioning

confidence: 99%

“…Amorphous mixed oxides pore diameter are formed between 0.6-0.7 nm by this process, and it can easily increased to the mesopore range by varying some of the important reaction conditions, such as change in the nature of the alkoxide anions or increase of acid concentrations or by use of templates [26]. By using CTAB (cetyl trimethyl ammonium bromide) as a template, a microporous as well as mesoporous Zr-Si mixed oxide are prepared [140].…”

Section: Catalystsmentioning

confidence: 99%

Amorphous Porous Mixed Oxides: A New and Highly Versatile Class of Materials

Pandey

Mishra

2012

Intelligent Nanomaterials

View full text Add to dashboard Cite

Porous solids are a rapidly developing class of materials with an ever-increasing range of applications. Among these materials, amorphous porous mixed oxides possess the extraordinary properties of fine tuning the chemical composition, microstructure, porosity and surface properties. The tailor made composition of the mixed oxides can be fabricated from the availability of variety of precursor, additives and modifiers. Besides, their performance can be found close to that of crystalline phase. These amorphous mixed oxides can easily be synthesized using acid / base catalyzed one-pot sol-gel procedure. Sol-gel processes allow for a relatively facile tailoring of the morphology of mixed oxides to the desired application in the field of nanotechnology. Pore volume, porosity, specific surface area, and surface acidity are typical parameters that can be tailored. This chapter deals with the preparation methodology, characterization techniques, and application of amorphous porous mixed oxides.

show abstract

Preparation and utilization of molecularly imprinted silicas

1997

View full text Add to dashboard Cite

Nowadays, there is increasing interest in the use of the technique of molecular imprinting to prepare specific new solids employed essentially as separation materials ['] and, to a lesser extent, as catalytic supports.121 In most cases, these solids have been prepared by polymerization of functionalized organic monomers which were previously preorganized around a template molecule via covalent or noncovalent bonds."] Enantiomeric or diastereoisomeric separations were performed with very high separation factors of up to 31.7 in the case of alka10ids.l~~ An alternative approach based on the use of inorganic precursors is distinctly less developed, although first reports are quite old.['] Despite their lower interaction energy (mainly steric constraints), inorganic amorphous solids can be attractive due to their higher thermal and mechanical stability.The principle of molecular imprinting with the sol-gel technique is shown schematically in Figure 1. Small amounts of organic template are mixed with a silica precursor. After addition of a polymerization catalyst, a solid containing the template is obtained: this organic molecule is then removed under mild conditions in order to obtain empty pores with size and shape as close as possible to those of the template. Solids capable of selective adsorption were recently prepared by Maier et aLL6] using this technique. In a competitive adsorption experiment, an imprinted borneol silica adsorbed specifically borneol with respect to camphor or fenchyl alcohol.In this paper, we report an attempt to prepare silicas capable of adsorbing specific alcohols using the approach described above. The influence of the conditions of the solgel process on the texture of solids and on their molecular specificity are discussed. Enantiorecognition of these solids was first evaluated by using (-)-menthol as a template (Scheme 1). then the regiospecificity of o-cresol imprinted solids was investigated.Textural data concerning the different gels are summarized in Table 1, and typical nitrogen adsorption isotherms are shown in Figure 2. Whatever the conditions, no significant differences were observed (except for the fluoride-catalyzed solids) with or without template, due to the low quantity of template introduced (1 %). In the case of fluoride-catalyzed solids, the synthesis was not as reproducible as with acid-and base-catalyzed gels. Acid-or base-catalyzed solids aged for two weeks showed high specific areas (> 700 m2/g) while fluoride-catalyzed solids were less porous (400 m2/g). From the shape of the adsorption iso- (Fig. 2b) are essentially mesoporous with a large pore-size distribution. The base-catalyzed solids possessed micro-and mesopores and the relative proportion varied according to the calculation method. This was confirmed by the determination of the mean diameter by the BJH method, which gave a size of 20.8A. In the case of base-catalyzed gels, when solids were not aged (Fig. 2d) the nitrogen adsorption-desorption isotherms were similar to those obtained in the case of aged ac...

show abstract

Sol-Gel Methods for the Production of Novel Catalytic Materials

Cited by 8 publications

References 31 publications

Amorphous Microporous Titania Modified with Platinum(IV) ChlorideA New Type of Hybrid Photocatalyst for Visible Light Detoxification

Amorphous Microporous Titania Modified with Platinum(IV) ChlorideA New Type of Hybrid Photocatalyst for Visible Light Detoxification

Amorphous Porous Mixed Oxides: A New and Highly Versatile Class of Materials

Preparation and utilization of molecularly imprinted silicas

Contact Info

Product

Resources

About