Zeolite L LTL

An IR spectrum of zeolite L (LTL) was pubUshed as early as 1971 by Ward in his review article on infrared studies with zeoHtes [383] which dealt predominantly with faujasite-type materials (vide supra). He observed in deammoniated samples of NH4-L sharp bands at 3740 and 3630 cm and a broad band centered around 3200 cm. After evacuation at 813 K, only the 3740 cm band remained. Similarly, Weeks and Bolton [467] foimd on deammoniation of NH4,K-L, besides the absorbance at 3740 cm, a single weak band at 3630 cm . Major changes occurred in the framework region. 

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Figure 5 Stereopair of zeolite L (LTL) structure viewed along [001]...

However, due to their poor solubUity in aqueous media as compared to alkali metals their use has been limited. Synthesis periods for low-silica materials range from several hours to several days. Several low-sUica zeolites, including zeolite A (LTA), faujasite (FAU), zeolite L (LTL), and zeohte P (GIS), have found use industrially. 

In spite of the variety of methods now available for the synthesis of alkali metal clusters in zeolites, the range of zeolites in which clusters have been identified remains small. On the basis of diffuse reflectance spectra, Liu and Thomas [36] reported the presence of K + in potassium zeolite L (LTL), and NaJ and Na + in both sodium mordenite (MOR) and the clay laponite, after irradiation with far-UV light. Ikemoto et al. [37] used microoptical spectroscopy to examine the adsorption of potassium in potassium mordenite. With regard to frameworks other than aluminosilicates, Na has been reported in aluminogermanate and gallosilicate sodalites (SOD) [38,39] and in gallosilicate zeolite Y (FAU) [36]. 

Fig. 7. a Representation of a quantum wire array based on the one-dimensional channels of zeolite L (LTL). b Randomly oriented Kf clusters thought to mediate charge transport along the channels in K/K-L... 

Zeolites exhibit various pore systems. Zeolitel L (LTL) has parallel one-dimensional channels, Mordenite (MOR) has two different one-dimensional parallel chan-... 

Commercially significant zeolites include the synthetic zeolites type A (LTA), X (FAU), Y (FAU), L (LTL), mordenite (MOR), ZSM-5 (MFI), beta ( BEA/BEC), MCM-22 (MTW), zeolites E (EDI) andW (MER) and the natural zeolites mordenite (MOR), chabazite (CHA), erionite (ERl) and clinoptiloUte (HEU). Details of the structures of some of these are given in this section. Tables in each section lists the type material (the common name for the material for which the three letter code was established), the chemical formula representative of the unit cell contents for the type material, the space group and lattice parameters, the pore structure and known mineral and synthetic forms. 

Via confined space synthesis with porous carbon as inert support material, synthesis of nanosized zeohte crystals of several topologies is possible and their recovery via controlled pyrolysis of the carbon becomes feasible [155]. In the 45-nm carbon black pores nanocrystals of ZSM-5 (MFI) of about the same size were obtained. The method is of general utiUty, as it seems possible to make nanosized zeohtes of Beta zeolite X and Y and L (LTL), which can be easily washed, ion exchanged and finally isolated via calcination [156]. 

The aluminophosphate analog of zeolite Linde-type L (LTL) consists of 1-D 12-membered ring channels with cylindrical pore openings of 0.71 nm (35). 

The zeolite Linde-L (LTL framework) was first synthesized by [65B1] and was noted to be a large pore zeolite. This has been confirmed by a structme analysis [69B1]. It has 12-ring channels and is isostructural with perlialite as shown later [90A1]. 

Linde Type L (zeolite L) [69B1], gallosilicate L [85W1, 86N1], LZ-212 [85B2], [Al-P-0]-LTL [02V1]... 

The zeolites of Linde type L (LTL) were shown to exhibit the shape-selectivity effect due to a specific confinement of n-hexane as a 6-ring pseudocycle inside the zeolite structure (Maxwell in Ref. [2]). Chevron researchers published the results on hexane aromatization on Pt/Cs-B-BEA zeolite and developed the AROMAX process [28]. The reaction proceeds at 460 80°C with a rather high selectivity close to 80%, but the catalyst is sulfiir-sensitive and the commercial application can hardly be envisioned. 

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