Chabazite CHA

Pore structure Three-dimensional eight-ring 

Synthetic forms AlPO-34, CoAPO-44, CoAPO-47, DAF-5, GaPO-34, Unde D, Unde R, LZ-218, MeAPO-47, MeAPSO-47, (Ni(deta)2)-UT-6, Phi, SAPO-34, SAPO-47, UiO-21, ZK-14, ZYT-6 

---

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. 

Other framework structures based on zeolites have also been synthesized which contain atoms other than aluminium and silicon, such as boron, gallium, germanium, and phosphorus, which are tetrahedrally coordinated by oxygen. Such compounds are known as zeotypes. Pure aluminium phosphate, commonly called ALPO, and its derivatives, can take the same structural forms as some of the zeolites such as sodalite (SOD), faujasite (FAU), and chabazite (CHA) (e.g., ALPO-20 is isostructural... 

The cage or window effect was proposed by Gorring (48) to explain the nonlinear effect of chain length observed in hydrocracking of various n alkanes over T zeolite, chabazite (CHA) and erionite (ERI). Thus, when a nC22 alkane is cracked over erionite, there are two maxima in the size distribution of the product molecules at carbon numbers of 4 and 11 and a minimum at carbon number of 8. The diffiisivities of n-alkanes also change in a similar periodic manner by over two orders of magnitude between the minimum at C8 and the maxima. This shows that for diffusion, and hence for shape selective effects, not only the size but also the structure of the reactant and product molecules need to be considered. 

Chabazite CHA 3.8 X 3.8 3 CoAPO-44 CoAPOA SAPO-34 LZ-218 Linde D Linde R MeAPO-47 MeAPSO-47 Willhendersonite ZK-14 ZYT-6... 

Sodhun-forms of zeohtes X, Y, ERI, and MOR were obtained by courtesy of Chemical Works, Wolfen, Germany LTA-zeohte was provided by Bayer AG, Germany, and MFI samples by Danube Petroleum Refinery, Hungary. Natural zeohtes were of sedimentary origin clinoptilohte (C,HEU) from Horseshoe Dam, Arizona, USA chabazite (CHA) from Beaver Divide, Wyoming, USA phil%site (PHI) fi om Shoshone, California, USA. 

Faujasite structure and stoichiometry. Zeolites were discovered in 1751 by the Swedish mining engineer, Cronstedt.33 There are many naturally occurring forms,34 like chabazite (CHA),35 as well as synthetic ones, like MCM-41.36... 

Optimised structure (from periodic ab initio calculations) of hydrogen adsorbed in Cu(l)-chabazite (CHA). Adapted from Figure 5 in Solans-Monfort et al. (2004). 

Li et al. [54] increased the length of their tubular SAPO-34 membranes by a factor of 5 by controlling thoroughly the synthesis conditions. Sato et al. [55] have developed industrial size (40 cm long) chabazite (CHA)-type zeolite membranes by controlling the synthesis conditions and used them in pervaporation showing that continuous research is devoted in this field to be able to compete with polymeric membranes. 

Hasegawa Y, Hotta H, Sato K, Nagase T, Mizukami F. Preparation of novel chabazite (CHA)-type zeolite layer on porous a-AljOj tube using template-free solution. 7 Membr 5 2010 347(1-2) 193-196. 

Fig. 8. Three types of cages in the framework of A1P04-52 a chabazite (cha), gmelinite (gme) and AIPO4-52 cage (aft).

An important group of catalysts for NOx reduction through anunonia SCR is represented by copper exchanged zeolites [1-9]. Many different zeolites have been investigated, for example, Cu-ZSM-5 [10-13], Cu-faujasite [14], Cu-Beta [15,16], and Cu-Y [17]. Recently, copper zeolites with chabazite (CHA) structure have received great attention due to their high thermal stability and hydro carbon resistance [18]. Both Cu-SAPO-34 [19] and Cu-SSZ-13 [18] have a CHA structure... 

---