Montmorillonite Acid-treated

The synthesis of dimeric fatty acids is based on the reaction between a fatty acid with one double bond (oleic acid) and a fatty acid with two double bonds (linoleic acid) or three double bonds (linolenic acid), at higher temperatures in the presence of solid acidic catalysts (for example montmorillonite acidic treated clays). Dimerised fatty acids (C36) and trimerised fatty acids (C54) are formed. The dimer acid is separated from the trimeric acid by high vacuum distillation. By using fatty dimeric acids and dimeric alcohols in the synthesis of polyesters and of polyester polyurethanes, products are obtained with an exceptional resistance to hydrolysis, noncrystalline polymers with a very flexible structure and an excellent resistance to heat and oxygen (Chapter 12.5). Utilisation of hydrophobic dicarboxylic acids, such as sebacic acid and azelaic acid in polyesterification reactions leads to hydrolysis resistant polyurethanes. 

Bouanani et also reported the use of miniemulsion polymerization for the encapsulation of acid-treated montmorillonite within a fluorinated cyclo-siloxane [l,3,5-tris(trifluoropropylmethyl)cyclotrisiloxane]. Figure 1.12 shows the X-ray diffractograms of the pristine montmorillonite, acid-treated montmorillonite and nanocomposite before and after polymerization. The diffraction peak for the pristine montmorillonite was observed at 13.5 A, which was shifted to 18.01 A° after acid treatment. The authors opined that the observed larger basal plane spacing may be a result of interlamellar water layers due to the acid treatment and thus reflects the change in interlayer cations and their... 

Yet more improvements in the synthesis of chlorocyclophosphazenes have appeared. Yields in the PC15-NH4C1 reaction are increased by the use of heavy-metal salts as catalysts,93 but similar results may also be achieved by the use of acid-treated montmorillonite clay.94 The use of surfactants can also improve yields of cyclic products.95... 

The industrially important acetoxylation consists of the aerobic oxidation of ethylene into vinyl acetate in the presence of acetic acid and acetate. The catalytic cycle can be closed in the same way as with the homogeneous Wacker acetaldehyde catalyst, at least in the older liquid-phase processes (320). Current gas-phase processes invariably use promoted supported palladium particles. Related fundamental work describes the use of palladium with additional activators on a wide variety of supports, such as silica, alumina, aluminosilicates, or activated carbon (321-324). In the presence of promotors, the catalysts are stable for several years (320), but they deactivate when the palladium particles sinter and gradually lose their metal surface area. To compensate for the loss of acetate, it is continuously added to the feed. The commercially used catalysts are Pd/Cd on acid-treated bentonite (montmorillonite) and Pd/Au on silica (320). 

Clays or acid-treated clays are also effective supports for Lewis acids such as ZnCl2 or FeCl3 [23]. Montmorillonite-supported zinc chloride, known as Clayzic, has been extensively studied as a catalyst for e.g. Friedel-Crafts alkylations [24, 25] (see Fig. 2.2). 

Adams, J. M. 1987. Synthetic organic chemistry using pillared, cation-exchanged and acid-treated montmorillonite catalysts a review. Appl. Clay Sci, 2 309-342. 

In the literature, different commercial montmorillonites are used, especially for catalytic purposes (KSF or K10 montmorillonites). They are usually acid-treated clays, montmorillonite content of which is rather low. Our x-ray diffraction studies show 44% Ca-montmorillonite content of K10 montmorillonite, and 53% Na-montmorillonite content of KSF montmorillonite the CEC of KSF montmorillonite was found to be 30 meq/100 g by the ammonium acetate method (Richards 1957). A similar value has been given by Abollino et al. (2003). So, in a strict clay science sense, they cannot be considered as montmorillonite. Naturally, this causes no problems in organic chemistry when the main objective is the catalysis of a given reaction. 

For KSF montmorillonite, the number of silanol and aluminol sites was found to be less by an order of magnitude. It is in accordance with the ratios of specific surface areas (10 m2/g for KSF montmorillonite, and 93.5 m2/g for montmorillonite [Istenmezeje]). This is an interesting observation because KSF montmorillonite is an acid-treated substance. Thus, it seems that acidic treatment causes the decrease of the layer charges (the CEC decreases montmorillonite content of Ca-, Cu-, and Zn-montmorillonites is 91%, and that of KSF montmorillonite is 53%). The acidic treatment, however, does not change the nature of silanol and aluminol sites, the stability constants of the edge charge reactions remains the same, and the number of edge sites is proportional to the specific surface area. 

Recently, silica-based synthetic materials have been used in bleaching. The natural bleaching earth, fuller s earth, a hydrated aluminum silicate, mostly has been replaced by acid activated clays, which are sulfuric- or hydrochloric-acid-treated bentonites or montmorillonites. Manufacmrers continuously improve the quality and develop new bleaching earths to meet the market s needs. Higher activity and filterability are the main focuses of such development. 

The discrimination of protonated Si sites by CP MAS was also used by Yang and Kirkpatrick (1989) in a study of the hydrothermal decomposition of albite and sodium aluminosilicate glass, and rhyolitic glass (Yang and Kirkpatrick 1990), and as a means of differentiating between the various sites in acid-treated montmorillonites (Tkac et al. 1994). CP MAS NMR has also been used to identify a Si site at -100 ppm in a microporous material derived from acid-leached metakaolinite as the unit Si(0Si)30H (Okada et al. 2000). 

AR grade acetic anhydride, dodecatugstophasphoric acid-a heteropolyacid (HPA), zirconium oxychloride, anhydrous aluminium chloride, sodium carbonate and ammonium sulphate were obtained from s.d.Fine Chem. Ltd, Mumbai. 2-MON (yarayara) was obtained from Aerofine Industries Ltd, Mumbai. Amberlyst-15 was procured from Rohm and Huss, USA., and Indion-130 from Ion Exchange (India) Ltd. These catalysts were used as such. Zeolites ZSM-5, Y and Mordenite were obtained from M/s Associated Cement Company (ACC), India. Commercially available acid treated KIO montmorillonite clay was obtained from Fluka. SWy-2 (Wyoming Na -montmorillonite) was obtained from Clay Minerals Society, Source Clay Minerals Repository, Missouri University, Columbia, USA. 

The optimum loading for a high surface area mesoporous silica is about 1.5 mmol g-1, twice as high as that for the acid-treated montmorillonite clay K10. The former catalyst is also a little more active and selective towards monoalkylation, although K10 is a less expensive support material. 

Figure 10. Activity of clay catalysts for 1-dodecene alkylation of benzene at 473 K (reaction time = 3 h 1 = starting montmorillonite 2 = acid treated montmorillonite 3 = acid treated montmorillonite calcined at 773 K per 4 h 4 = pillared montmorillonite calcined at 773 K for 4 h 5 = acid treated pillared montmorillonite calcined at 773K for 4 h 6 = KIO) [83].

Bolognini, M., Cavani, F, Cimini, M., Dal Pozzo, L., Maselli, L., Venerito, D., Pizzoli, F, and Veronesi, G. 2004. An environmentally friendly s)mthesis of 2,4-dihydroxybenzophenone by the single-step O-mono-benzoylation of 1,3-dihydroxybenzene (resorcinol) and Fries rearrangement of intermediate resorcinol monobenzoate the activity of acid-treated montmorillonite clay catalysts. C. R. Chim. 7 143-150. 

Houdry had found acid treated clay to be a superior cracking catalyst. This was fortunate since acid treated clays had been used in the U.S. for decolorizing petroleum and other products. For example, Filtrol was founded in 1922 by "three typical Californian style west coast entrepreneurs 61). The bentonite or montmorillonite clays were leached with sulfuric acid at its boiling temperature in a process called acid denning, washed, filtered, dried and then sized to meet the needs of its application. The early clays that Filtrol produced were used almost exclusively to treat lubricating oils. Later on, similar treatments were used with kaolinite and halloysite clays... 

Figure 9.5 FTIR spectra of pristine montmorillonite (MMT), mono-treated montmorillonite (MMT treated with octadecylammonium (MIO), MMT treated with aminoundecanoic acid (MOl)), co-treated montmorillonite (MMT treated with octadecylammonium and aminoundecanoic acid with dilFerent molar ratio of 1/1,1/2 (Ml 1, M12)).Reprinted from [24] with permission from Elsevier.

Suzuki and Suga reported the use of clays as solid acids to support and activate metallocene catalysts for olefin polymerization. They were able to use much less alkylaluminmn cocatalyst relative to solution polymerization conditions. The clays were slurried with AlMeg in toluene, then treated with a solution containing zirconocene dichloride, II, and AIMeg. The metallocenium cation was presumed formed via abstraction of chloride and/or methyl ligands by acidic sites on the surface of the clay, and the low basicity of the clay smface was proposed to stabilize the coordinatively unsaturated cation. Propylene was copolymerized with 250 psi ethylene at 70°C. For acid-treated KIO montmorillonite, an activity of 3300 X 10 kg polymer/(g Zr h) was obtained. Catalysts based on vermiculite, kaolin, and synthetic hectorite all showed lower but still appreciable activities. In this brief report, the Al/Zr ratio was not specified, and the clay dispersion was not reported. 

Possible activation mechanism by alkyl group abstraction for an organozirconium complex on acid-treated montmorillonite passivated with Al Bug. 

TEM micrograph (scale bar 100 nm) for a polyethylene nanocomposite containing acid-treated montmorillonite (5.4 wt%). The material was made by in situ polymerization using Zr(CH2Ph)4 supported on the Al Bug-treated clay, using a prepolymerization step. 

Woo et al. created supported MAO cocatalysts by hydrolyzing AlMcg in the presence of acid-treated clays, then used them to activate Cp2ZrCl2 (11). ° The clays were hydrated KIO montmorillonite (4.9 wt% H2O) and KIO dehydrated at 160°C. Each was treated with excess AlMe3 until methane evolution ceased. The AlMe3 reacted with all of the included... 

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