Montmorillonite Mordenite zeolite

Experiments were carried out using isotopically labelled methanol (97% 0) and ethanol (98% purchased from MSD Isotopes. Anhydrous isobutanol was purchased from Aldrich Chemical Co., Inc. and contained the natural abimdances of orygen isotopes, i.e. 99.8% and 0.2% O. Nafion-H was obtained fi om C. G. Processing, Inc. and Amberlyst resins were provided by Rohm and Haas. The 2SM-5 zeolite was provided by Mobil Research Development Corp. H-Mordenite, montmorillonite K-10, and silica-alumina 980 were obtained firom Norton, Aldrich, and Davison, respectively. y-AIumina was prepared from Catapal-B fi om Vista. 

For example. Date et al. (1983) recognized the following alteration zones in the Fukazawa Kuroko mine area of Hokuroku district from the centre (near the orebody) to the margin (1) sericite-chlorite zone (zone 111 in Figs. 1.20-1.22) characterized by quartz + sericite Mg-rich chlorite (2) montmorillonite zone (zone 11 in Fig. 1.20) characterized by Mg-Ca-type montmorillonite + quartz kaolinite calcite sericite Fe-rich chlorite and (3) zeolite zone (zone 1 in Fig. 1.20) characterized by clinoptilolite + mordenite + Mg-Na-type montmorillonite cristobalite calcite or analcime + Mg-Na-type montmorillonite + quartz calcite sericite Fe-rich chlorite (Fig. 1.20). 

The major aluminous clay minerals, alkali zeolites and feldspars which are most commonly associated in nature can be considered as the phases present in a simplified chemical system. Zeolites can be chemiographically aligned between natrolite (Na) and phillipsite (K) at the silica-poor, and mordenite-clinoptilolite at the silica-rich end of the compositional series. Potassium mica (illite), montmorillonite, kaolinite, gibbsite and opal or amorphous silica are the other phases which can be expected in... 

Many applications of AFM to pillared clays or zeolites have not specifically addressed the porosity characteristics, but rather the occurrence of adsorbed surface Al species in, e.g., pillared montmorillonite [41], or the crystal growth processes, adsorption on porous surfaces and the surface structure of natural zeolites [42]. Sugiyama et al. [43] succeeded to reveal the ordered pore structure of the (001) surface of mordenite after removal of impurities that clogged the pores. The authors indicated that resolution in AFM imaging of zeolites is significantly affected by the magnitude of the periodical corrugation on the crystal surface, so that if the surface contains deep pores only the pore structure, but not the atomic structure, can be resolved. 

Catalysts NaY, REY, H-mordenite were supplied in 1/16 pellets from Strem Chemicals, zeolite A (2 mm pellets) from Merck, the X-type (1/16) zeolite from Grace and the montmorillonite K 10 from Sud-Chetnie (powder). For ion exchange [10], the zeolites were suspended in a 0.5 molar aqueous solution of the appropriate salt and heated to reflux for 2 hours. The exchanged zeolite was filtered, washed salt free with distilled water and dried over night at 80 °C. Activation was carried out in the micro reactor with a stream of dry air (20 ml/min) at 550 °C for 3 hours with the zeolites and at 350 °C in the case of montmorillonite, respectively. 

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. 

Because acidified titanium oxide is the catalyst usually employed commercially for the transformation of 1 into 2 [8] there has been much investigation of this catalytic system [9]. A 1995 paper by Stefanis et al. [10] reported an investigation of the reaction of 1 in several alumina-pillared clays (PILCs montmorillonite- and beidellite-based, and their and Ca" -exchanged congeners) under Lewis acid conditions (solid is activated by heat to remove all water). The results were compared with those obtained by use of medium-pore zeolites USY, NH4+-ZSM-5, and H-mordenite. Conversion to 2 > 50% was always observed. The aim of the work was to clarify differences between site availability and acidity for the two types of solid. 

Most of the catalysts were commercial SA, a silica-alumina containing 13 wt% aliunina, from Ketjen K 10, an acidified montmorillonite, from Siid-Chemie FAU 2.5, the Linde tsrpe Y molecular sieve SK-41, from Alfa-Products FAU 15, MOR 11 and MOR49, dealuminated HY and Mordenites, were gifts from Zeocat MOR 6.5 was obtained from Norton MFI 25, a H-ZSM-5 zeolite, from Conteka. BEA 27, a beta zeolite, was synthesized according to Wadlinger et... 

The materials tested were Na- and La-montmorillonites from Lago Pellegrini (Argentina) [38]. The substituted samples were obtained by saturation of the ion-exchange capacities of the water-saturated clay samples with sodium and/or lanthanium chloride (0.5 M). Finally, the Na- and La- samples were air dried. Moreover, thermodesorption of liquids from natural zeolite-clinoptilolite and zeolite-mordenite (from Ukrainian Transcarpathian region) were made. 

Figures. Schematic representation of the structures of zeolite Y (3-D), montmorillonite clay (2-D), zeolite mordenite (1-D) and a.-cyclodextrin (0-D)...

Besides the classical Si and Al-containing zeolites, there is an ongoing search toward other Lewis acidic zeolites and other microporous materials suitable for this reaction. Taaming et al. made a comparison between beta zeolites substituted with Al, Sn, Zr, and Tl. As with the homogeneous catalysts, this comparison pointed to Sn-based catalysts as extremely selective for this reaction. The authors obtained lactic acid and lactate yields of 90% and >99% at 125 and 80°C, respectively, with an Si Sn ratio of 125 [67]. Since then, numerous reports were published including Sn-montmorillonite [68], mesoporous Sn-MCM-41 (Mobil Composition of Matter) [69,70], Sn-MFI (Mordenite Framework Inverted) [70,71], Sn-deAl-beta [72], Sn-SBA-15 (Santa Barbara Amorphous type material) [70], Sn-MWW (Zeolite Framework Type M-22)... 

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