John Francis Brody

Vanadyl hydrogenphosphate hydrates: VO(HPO4) · 4H2O and VO(HPO4) · 0.5H2O

Abstract Two vanadyl(IV) monohydrogenphosphate hydrates have been crystallized from aqueous media and their structures determined by single-crystal X-ray diffraction. The first, a tetrahydrate, VO(HPO4) · 4H2O, is triclinic, P 1 , with a = 6.379(2), b = 8.921(2), c = 13.462(3) A, α = 79.95(2), β = 76.33(3), γ = 71.03(3)°. Final residuals of R1 = 0.058 and R2 = 0.065 were obtained using 1250 unique data and 140 parameters. The second was found to be the hemihydrate, VO(HPO4) · 0.5H2O, with orthorhombic symmetry, Pmmn. Complete structure solution and refinement using data from a 2.7 × 105 μm3 crystal gave atomic parameters in close agreement with those recently reported in a parallel study (C. C. Torardi and J. C. Calabrese, Inorg. Chem. 23, 1308, 1984). Final residuals R1 = 0.041 and R2 = 0.042 were obtained on optimizing the 45 structural variables using 458 observed intensities. The structures of these two hydrates and that of the pyrophosphate, (VO)2P2O7, show a close correspondence. The degree of condensation of the vanadyl octahedra and phosphate tetrahedra, and the amount of water of crystallization in these materials are closely coupled and depend on the formation temperature.

Hydrothermal synthesis and characterization of vanadyl alkylphosphonates VORPO3 · H2O

Abstract A series of layered compounds of general composition VO(C n H 2 n +1 PO 3 ) · y H 2 O ( y = 1.5, 1 ⩽ n ⩽ 3; y = 1.0, 4 ⩽ n ⩽ 8) has been synthesized by hydrothermal reaction of V 2 O 3 and the corresponding alkylphosphonic acid in water at 200 °C. The compounds with n ⩽ 3 have structures similar to that of VO(HPO 4 ) · 0.5H 2 O. The compositions with4 ⩽ n ⩽ 8 also are layered, with structures apparently related to that of VO(C 6 H 5 PO 3 ) · H 2 O. The phases with n ⩾ 4 have compositions and structures identical to those of the compounds prepared via water treatment of the benzyl alcohol intercalation compounds VO(C n H 2 n +1 PO 3 ) · H 2 O · C 6 H 5 CH 2 OH, which were reported previously.

Controlling the chemistry of the micropore volume in pillared clays and micas

Pillared clays are microporous materials formed by propping apart clay layers with robust inorganic polyoxocations. The chemistry of the micropore space can be tailored by choosing suitable pillaring species, by adding various functionality to the pillar surfaces, and by incorporating small metal particles within the micropores. We have found that by using a commercially available zirconyl acetate solution as the zirconia polyoxocation precursor, zirconia-pillared micas with superior properties of crystallinity and microporosity can be produced. Catalytic tests have shown that treatment of a zirconia-pillared montmorillonite with sulfate increases the acid site strength and density of the zirconia pillars. In addition to materials with enhanced acidity, it is desirable to produce materials with little or no acidity for use as metal supports for catalysts in applications such as light alkane dehydrogenation, where support acidity leads to undesirable side reactions. Tetrasilicic fluoromica can be pillared by silsesquioxane oligimers derived from the in situ hydrolysis of an aminosiloxane reagent. After a two step calcination, the silica-pillared fluoromica produced has a high surface area and crystallinity, and the combination of the inert fluoromica layers with the non-acidic silica pillars makes this new material an interesting nonacidic support for noble metal catalysts.

Olefin isomerization over an alumina-pillared fluoromica catalyst

Abstract In the recent past, research on pillared clays has centered on materials made from smectites, such as montmorillonite and hectorite. We have extended the range of pillared clay-like materials to micas, 2:1 layered silicates with higher layer charge density, by pillaring tetrasilicic fluoromica (NaMg2.5Si4O10F2) with aluminum chlorhydrate solution. The resultant microporous alumina pillared mica can be used as an acid catalyst to effect the isomerization of 2-methylpent-2-ene. Analysis of the activity of the pillared mica as well as its selectivity as compared to γ-alumina demonstrates that the pillared mica has a high concentration of moderately strong acid sites, with a relatively narrow acid strength site distribution.

Pillared Clays and Micas

The interest in the petroleum industry in converting heavier feeds to liquid fuels has led to a search for microporous materials with pore sizes larger than those found in the faujasitic zeolites which form the basis of many petroleum processing catalysts. Materials with zeolite-like pores in the 10 A range can be synthesized by intercalating large polyoxocations between the layers of smectite clays. Subsequent calcination dehydrates the cations and converts them into oxide pillars that prop the clay layers apart, resulting in permanent microporosity in the interlayer region. Pillared clays have been studied extensively during the last decade due to their potential use in petroleum processing as cracking and hydrocracking catalysts. Previous workers have primarily utilized smectite clays such as montmorillonite and hectorite as the starting layered material for pillared clay. We now report that synthetic fluoromicas, clay-like materials of layer charge density higher than that of smectites, can also be pillared with polyoxoaluminum cations to form aluminapillared fluoromicas that are thermally stable up to 700°C.

Synthesis and sorptive properties of EMM-8: a new (silico)aluminophosphate

A new (silico)aluminophosphate, EMM-8, was synthesized using 2- or 4-(dimethylamino)-pyridine as structure directing agent, with or without fluoride. The crystal structure of EMM-8 was determined with synchrotron powder XRD data of a calcined sample, and was supported with hydrocarbon adsorption data. The framework of EMM-8 is isostructural with that of uncalcined SSZ-51 (SFO), but SSZ-51 was synthesized only in the presence of fluoride. SAPO-EMM-8 can be synthesized in the absence of fluoride.