The intrazeolite chemistry of the two germylene complexes Cl2(THF)GeM(CO)5(M = Mo, W) was studied with x-ray absorption spectroscopy (Ge, Mo, W edge EXAFS) and in-situ FTIR/TPD-MS techniques. The slightly decarbonylated GeMo complex interacts with the framework of NaY zeolite at room temperature and retains the Ge-Mo bond up to about 100° C. In proton-loaded HY zeolite, framework interactions increase at elevated temperature, and the attached complex retains the Ge-Mo bond up to about 120° C. The Ge-Mo bond is cleaved at higher temperatures. MoC1x and Mo-Mo species are formed in NaY and HY zeolite, respectively, while GeClx fragments are anchored to the zeolite framework.

The complex Cl2 (THF)GeW(CO) 5 retains all five CO ligands up to about 100° C in both NaY and the proton form. Detectable anchoring occurs at room temperature in NaY and at about 80° C in the proton form. WC1x species are formed upon cleavage of the Ge-W bond at higher temperatures.

The incorporation of molybdenum into the faujasite pore system via reaction of MoCl5 with H-Y zeolite results in dealumination of the zeolite framework and formation of MoO3 species. These species are readily sulfided by H2S, but MoS2 clusters are not produced. A sulfur-bridged dimeric molybdenum cluster, of proposed composition HO-Mo-(S)3-Mo-OH, is formed, which can strongly chemisorb CO. Sulfidation of niobium in this manner is not readily accomplished.

Zeolite NaY was exchanged with three levels of Cu2+ and Ni2+ ions which were subsequently reduced in ethylene glycol (polyol process) at 195° C. This process effectively reduced the transition metal ions to zerovalent forms and the degree of reduction was dependent on the amount of exchange and the location of transition metal ions. Polyol process was found to be more efficient in reducing these ions located in zeolite cages than commonly used molecular hydrogen. Comparison of reduction behavior of Cu2+ and Ni2+ ions indicated that better metal dispersion in NaY can be achieved for Ni2+ than Cu2+ by the polyol process.

The decomposition of zeolites is a novel route for the synthesis of aluminosilicate-based ceramic materials. Zeolites offer a number of advantages as ceramic precursors which allow the formation of dense ceramics at lower temperatures than by conventional methods. Using various cation-exchanged zeolites, ceramics and ceramic composites containing anorthite (CaAl2Si2O8). mullite (Al6Si2O11) cordierite (Mg2Al4Si5O18). celsian (BaAl2Si2O8), and ß-spodumene (LiAlSi2O6) have been formed. Using Extended X-ray Absorption Fine Structure (EXAFS), we have studied the reconstructive transformation of strontium-exchanged zeolite A to Sr-anorthite and have shown that the primary coordination of strontium remains intact during conversion.

This paper reports the engineering of an ideal zeolite-derived cordierite precursor and addresses the various technological issues that are encountered in the zeolite-to-ceramic process. Mg-exchanged zeolite B (SiO2/Al2O3=2.5) collapses to an amorphous powder at temperatures between 600 and 800°C. The resulting powder can be processed by various standard ceramic methods to give high-quality cordierite parts. The sintering behavior of MgB is described and compared with MgX, another zeolite that is conveniently synthesized with a 2.5 SiO2/Al2O3 ratio. Properties of MgB-derived cordierite are also described.

The application of zeolite molecular sieves as Magnetic Resonance Imaging (MRI) contrast agents is presented. Recent progress is described for X, Y and A type zeolites modified with paramagnetic species.

The preparation of a composite ceramic membrane consisting of large silicalite (MFI-type) crystals and a gas tight lead-boron silicate glaze is reported on. A one single crystal containing membrane model was prepared to establish the zeolite stability after each preparative step.

Aluminophosphate (AlPO4–5, AlPO4–11, AlPO4–17, AlPO4–20) and silicoaluminophosphate (SAPO-5, SAPO- 11, SAPO-17, SAPO-20) molecular sieves of varying pore sizes (3–8 Å) were synthesized and their water adsorption and desorption properties were studied. Water sorption isotherms of AlPO4 molecular sieves were characterized by unusual isotherm shapes, that is, little or no initial adsorption followed by extreme adsorption leading to volume filling by hydrogen bonding and cooperative interaction in micropores, apparently due to the nonpolar nature of pore surfaces coupled with weak (reversible upon evacuation) chemisorption of water, and hysteresis loops extending to very low pressures. Although micropore filling in AlPO2's and isostructural SAPO's was completed almost at the same relative pressure (p/po), SAPO's exhibited less extreme adsorption isotherms as a result of their slightly more polar nature of pore surfaces compared to AlPO4's. Neither AlPO4apos;s nor SAPO's exhibited Brunauer Type I isotherms with water, contrary to a general expectation of the hydrophilic microporous solids.

The synthesis of materials with void volumes in excess of 50% is an ongoing challenge in molecular sieve science. It has been shown that a correlation exists between the minimum framework density (FD) and the smallest ring in which all tetrahedral atoms reside (MINR). Based on this evidence it appears that materials containing 3-membered rings (3MR) will be necessary in order to obtain FDs lower than those currently attainable. Several framework beryllosilicate minerals including the natural zeolite, lovdarite, contain 3MRs. Unfortunately, beryllium can form highly toxic compounds that limit its suitability for many applications. Thus, in this study we have searched for a replacement for Be and have found that zinc is a suitable substitute with respect to the formation of three-membered rings.

We report here VPI-7, a novel zincosilicate molecular sieve which contains three-membered rings. The VPI-7 framework contains rings composed of 3–, 4– and 5 T-atoms which form unidimensional 8– and intersecting 9MR channels.

While we have prepared and structurally characterized over forty solids in the octahedral-tetrahedral framework molybdenum phosphate (MoPO) system, including molecules, 1-D polymers and 3-D materials, this paper will focus on the two dimensional layered MoPO's. Both covalently and H bonded layers will be discussed. Compounds covered include Na3[Mo2O4(HPO4)(PO4)]·2H2O, (Et2NH2)2[Mo4O8(PO4)4/2], Cs2Mo4P6O26, (4-phenylpyridie)2[Mo4O8(PO4)4/2], (cation)[Mo2O2(PO4)2(H2PO4)], with several different types of organic and inorganic cations, and (4-phenylpiperidine)4[Na2.5Mo6O15(H1.4PO4)4]·4H2O. These materials might provide a platform for the preparation of new types of pillared and intercalated inorganic solids.

Upon heating Ba2+, Sr2+ and Cd2+-exchanged zeolite RHO, abrupt changes have been observed in the cubic unit cell parameters [1–3]. Calculations of the powder x-ray diffraction patterns indicate these changes result from relocation of the extra-framework cations. For Ba2+ and Sr2+-exchanged RHO, a shift from the single 8-ring (S8R) to the double 8-ring (D8R)-site is accompanied by contraction of the unit cell. However, for the Cd2+-exchanged material relocation from the S8R to the single 6-ring (S6R)-site coincides with cell expansion. Further, with relocation of Cd2+ the low temperature acentric (A) form is transformed to a centric (C) structure above 300°C. The shift of Cd2+ ion occurs over a distance of 5.7Å, the largest observed in a zeolite.

X-ray diffraction (XRD) and adsorption isotherms have long been traditional methods of characterising molecular sieves. By combining these techniques at low temperatures with variable temperature 129-Xe N.M.R. we now have a fuller understanding of the behaviour of sorbed layers inside these materials. In particular we have observed phase transformations of Xe in a polyhydroxyaluminium-pillared montmorillonite molecular sieve and have developed a model consistent with the data. In addition, using XRD, an interpillar distance of ca. 30Å was calculated. We present the first detailed low temperature studies of 129-Xe N.M.R. on these systems.

It is shown that the interpretation of 129Xe chemical shift measurements in microporous solids is not simple, and that considerable caution must be used both in the measurement and interpretation of results, especially for large pore systems. Nevertheless, useful information can be obtained on the phase diagram of xenon in pore systems, and on transport within the solid and between the solid and the gas phase.

We have imaged micron sized silicalite crystals with an atomic force microscope (AFM). High resolution images taken in the repulsive mode show a periodic pattern that locally has a symmetry and periodicity which can be mapped onto the expected image looking along the [010] direction. Extra spots, however, appear in the image in regions which should correspond to channels exposed at the surface. These extra spots are attributed to multiple tip effects which should not affect the ability to detect long range ordering. On a scale length of ˜ 3 – 5 unit cells, the ordering in images deviates from that expected for a perfect crystal. This may be due to imperfections in the ordering at crystal surfaces. One other important aspect of the surface crystallography is revealed in low resolution scans where definite steps / grooves in the exposed surface are seen. The results are discussed in terms of the potential of AFM as a probe of surface crystallography.

We show that the frequencies of certain optically active lattice vibrational modes in a large number of zeolites can be used as direct structural probes. Mode frequencies are found to depend on the cosine of the T-O-T angle and the Si/Al ratio of the framework. The relationship between mode frequency and local framework structure is discussed in terms of a complete lattice dynamics calculation for specific zeolite structures as well as a lattice dynamical model of amorphous glasses.