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16, 24, 30, 22 and 26 W/mol for H,, N,, O,, CH,, and CO,, respectiuely. Ideal selectivities for H,/N,, CO,/CH,, and O,/N, were as high as 30, 10, and 3.5, respectively. Binary permeation measurements for the gas pairs CO,/CH,, O,/N,, and CO,/N, reuealed trends similar to those of single gas permeation and the properties are attributed to the membrane microstructure.

The synthesis and structure of a new zeolite, CIT-5 (California Institute of Technology Number Five), is described, which possesses one-dimensional pores comprised of 14 T-atoms (tetrahedrally coordinated silicon or aluminium atoms).Zeolites with pores comprised of larger than 12 T-atoms (extralarge pores) are much in demand 1-4 and have been so for many years. [4][5][6][7] The reason for this is the desire to perform catalysis/ adsorption on molecules > 8 Å in size.The first molecular sieve with extra-large pores was VPI-5 that is an aluminophosphate material with 18-ring pores. 8 Subsequently, other phosphate-based extra-large pore materials have been reported, e.g. cloverite. 2 All of the phosphate-based molecular sieves lack the desired properties of combined high acidity and thermal/hydrothermal stability and thus limit the practical potential. Recently, the first extra-large pore zeolite, UTD-1, was reported and shown to possess good acidity and thermal/hydrothermal stability. 9,10 Additionally, there have been numerous disclosures of ordered, aluminosilicate mesoporous materials with pore sizes of 20-100 Å. 11,12 Because the inorganic portions of the mesoporous materials are not crystalline, they lack the acidity and thermal/hydrothermal stability of high-silica zeolites. 13 Here, we report a new extra-large pore zeolite denoted CIT-5. CIT-5 is synthesized under hydrothermal conditions. A reaction mixture of composition 0.2 ROH : 0.1 LiOH : 0.02 Al 2 O 3 : 1 SiO 2 : 40 H 2 O is heated to 175 °C at autogenous pressure for ca. 12 d in order to produce CIT-5. In the absence of aluminium, pure-silica CIT-5 can be prepared in 5 d. The organic structuredirecting agent (SDA), R, is N(16)-methylsparteinium I and is prepared as previously reported. 14 In the absence of lithium, I can form pure-silica or borosilicate SSZ-24. 13,14 Thus, the key to the successful preparation of CIT-5 is both the SDA I and the inclusion of lithium. Further synthetic details are forthcoming. 15 Indexation 16 of the synchrotron powder X-ray diffraction (SPXRD) data from the pure-silica sample of CIT-5 revealed the presence of a small amount of an impurity phase together with the predominant CIT-5 phase. The CIT-5 material indexed in the orthorhombic crystal class with refined lattice constants a = 13.694(2), b = 5.0213(5), and c = 25.4970(3) Å (U = 1753.2 Å 3 ). The lattice constants for the impurity hexagonal phase were found to be a = 13.63 and c = 8.30 Å. The unit cell parameters and scanning electron micrographs helpd to identify the impurity phase as SSZ-24 (International Zeolite Association Code AFI). 17 Systematic absences for the orthorhombic CIT-5 phase indicate body-centering consistent with six possible space groups.The starting model for Rietveld refinement of CIT-5 was obtained by an iterative process of model building, distanceleast squares (DLS) 18 refinement of the atomic positions for the model, and comparison of the simulated powder X-ray pattern (CERIUS 19 ) to the experimental pattern. The model with the closest ma...

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