c-Oriented columnar MFI films made by secondary growth of randomly oriented seed monolayers, deposited using sonication-assisted covalent attachment, exhibit n-hexane/2,2-dimethylbutane separation factor of up to 10 4 , n-/i-butane separation factor of up to 50, and p-/o-xylene separation factor of up to 2. A MFI film from a-oriented seed layer shows lower separation factors for the linear vs. branched isomers but higher separation factor for p-/o-xylene.
In situ X-ray absorption spectroscopy (XAS) in catalysis research has traditionally been conducted by making one measurement at a time on a single sample. In an industrial research environment this is especially limiting as sample throughput (productivity) and turnaround time (direct project relevance) are critical issues in the use of XAS in a fast-moving technology delivery project. In order to address these issues we have developed and implemented a four-channel ionization chamber combined with two different in situ cells that allows XAS data to be collected simultaneously from four samples, or four regions, in transmission geometry without any sample or detector movement. In the development of this new capability it was realized that there are other benefits from this simultaneous detection in addition to increased productivity. Namely, (i) the use of EXAFS to determine the structure of a catalyst in situ axially at four different positions down a catalyst bed; (ii) the ability to collect up to four XAFS spectra simultaneously and thereby avoid any scan-to-scan uncertainties, and (iii) the added confidence in the ability to discriminate small differences in similarly prepared catalysts which is typical in the development of a commercial catalyst. Specific illustrations of each of these applications are shown. The methodology is simple to implement and could be used on any XAFS beamline with a horizontal fan of radiation, such as at a typical bending magnet or wiggler source beamline.
The title compound is tetragonal, P-421c, a = 13.275(3) Å, c = 5.500(2) Å, Z = 4. The structure refinement converged to R1 = 0.0442. On the basis of the Xray diffraction refinement the formula is Bi2PbMnP2O12. The crystal is an inverse twin. Electron diffraction revealed that the X-ray diffraction lattice parameters are from a subcell. The true unit cell is 2a, 2b, 3c. Single-crystal electron diffraction data lead to an apparent wave vector q = 1/2a + 1/2b + 1/3c, compatible with the Bravais lattice 4/mmmP(½ ½ γ ). However, this choice leads to forbidden reflections due to the presence of a 21 axis. An assumption that the crystal consists of a modulated, twinned orthorhombic structure with space group Ccc2 based on the cell (2a) 2 , (2b) 2 , c leads to a modulation vector q = a + γ (c). The (3+1) dimensional Bravais lattice becomes mmmC(10γ) and the super space group is Ccc2(10γ). The refinement of the single crystal x-diffraction data based on Ccc2 consisting of two 90° twin domains led, as expected, to the identical result as the refinement in P-421c. The crystal structure was determined from the X-ray diffraction intensities based on the subcell and represents an averaged structure. The PO4 radical can be present in two orientations. Pb occupies only ½ of the crystallographic 8e positions. The Pb atoms bond through oxygen atoms from PO4 to form a ring, creating channels parallel to c. Manganese and oxygen are present within the channels but the average structure prevents the determination of their location with certainty. Four samples Se, SSe40, SSe30 and SSe20 were prepared as bulk in the amorphous phase and then to the polycrystalline phase by annealing at 373 K for 5, 20, and 120 minutes. The trend of the amorphous and polycrystalline diffraction patterns was similar, which indicates that the basic structural units in both states are also similar. The results showed that the changes in the structural parameters for samples SSe40 and SSe30 are different from that of sample SSe20 these discrepancies are being discussed in terms of: the peak shifts in both the amorphous and crystalline state, the percentage of sulfur compositional variations, stress and crystallite size and finally in terms of the probable site occupancy of the sulfur atoms in the selenium structure. 1) From the results, we noticed that for the four samples the crystallite size is increased by the annealing time and the microstrain is decreased. 2) The crystallite size for SSe40 and SSe30 is always less than that of pure selenium. 3) In case of SSe20 the situation is different. 4) The discrepancies in these findings were due to the site occupancy of sulfur atom in the structural units of selenium. A novel layered tin(IV) phosphate, Sn(HPO4)·(NH3).(H2O)0.6, is synthesized under mild hydrothermal conditions. The crystal structure is solved for powder X-ray diffraction data. The unit cell is trigonal, a = 4.9751(2) Å, c = 22.5983(8) Å, space group R-3, Z = 3. The interlayer water and ammonia molecules are located in a disordered way in the same...
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