Interaction of water with the zeolite HY, studied by FT i.r.

Parker, L.M.; Bibby, D.M.; Burns, Gary R.

doi:10.1016/s0144-2449(05)80235-0

Cited by 53 publications

(27 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…After equilibrating the H-USY catalyst with PhCN vapor at room temperature for a period of time, followed by heating to 100 8C and maintaining there for an hour, we introduced water vapor into the system at room temperature. An excess amount of water was ensured from the appearance of the band at 1630 cm À1 , associated with physically adsorbed water [57]. The change in the CN stretching bands is illustrated in Fig.…”

Section: Effect Of Direct Addition Of Watermentioning

confidence: 99%

Catalytically active and selective centers for production of ɛ-caprolactam through liquid phase Beckmann rearrangement over H-USY catalyst

Ngamcharussrivichai¹,

Wu²,

Tatsumi³

2005

Applied Catalysis A: General

View full text Add to dashboard Cite

Section: Effect Of Direct Addition Of Watermentioning

confidence: 99%

Catalytically active and selective centers for production of ɛ-caprolactam through liquid phase Beckmann rearrangement over H-USY catalyst

Ngamcharussrivichai¹,

Wu²,

Tatsumi³

2005

Applied Catalysis A: General

View full text Add to dashboard Cite

“…During the last decade, adsorption of water on zeolites has been extensively studied both experimentally [1][2][3][4][5][6][7][8] and theoretically [9][10][11][12][13][14][15][16][17][18][19][20] in order to understand the nature of the interaction of basic molecules with the Brøn-sted sites in the zeolites. The reaction can be studied by infrared spectroscopy because the frequencies of the vibrations of the zeolite hydroxyl group will change upon interaction with the water molecule.…”

Section: Introductionmentioning

confidence: 99%

“…The reaction can be studied by infrared spectroscopy because the frequencies of the vibrations of the zeolite hydroxyl group will change upon interaction with the water molecule. When water is adsorbed on H-ZSM-5, [1][2][3][4][5][6]21 HY, 7 H-MOR, 4 or chabazite 22 a triplet of bands appears at 2872-3000, 2403-2515, and 1700 cm Ϫ1 , known also as an ABC triplet. This triplet is accompanied by two peaks at 3700 and 3550 cm Ϫ1 .…”

Section: Introductionmentioning

confidence: 99%

Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

Mihaleva¹,

Santen

Jansen

2004

The Journal of Chemical Physics

View full text Add to dashboard Cite

The changes in the spectra of the acidic group in chabazite are studied by quantum chemical calculations. The zeolite is modeled by two clusters consisting of eight tetrahedral atoms arranged in a ring and seven tetrahedral atoms coordinated around the zeolite OH group. The potential energy and dipole surfaces were constructed from the zeolite OH stretch, in-plane and out-of-plane bending coordinates, and the intermolecular stretch coordinate that corresponds to a movement of the water molecule as a whole. Both the anharmonicities of the potential energy and dipole were taken into account by calculation of the frequencies and intensities. The matrix elements of the vibrational Hamiltonian were calculated within the discrete variable representation basis set. We have assigned the experimentally observed frequencies at ϳ2900, ϳ2400, and ϳ1700 cm Ϫ1 to the strongly perturbed zeolite OH vibrations caused by the hydrogen bonding with the water molecule. The ABC triplet is a Fermi resonance of the zeolite OH stretch mode with the overtone of the in-plane bending ͑the A band͒ and the overtone of the out-of-plane bending ͑the C band͒. In the B band the stretch is also coupled with the second overtone of the out-of-plane bending. The frequencies at ϳ3700 and ϳ3550 cm Ϫ1 we have assigned to the OH stretch frequencies of a slightly perturbed water molecule.

show abstract

“…Second, Al can be removed or added to the aluminosilicate framework of many zeolites, which recrystallize (epitactically?) into a new continuous framework with the same structural connectivity (82)(83)(84)(85)(86)(87)(88)(89)(90)(91)(92)(93). Processes for extraction of Al include: (i) ion exchange with ammonium, heating to expel ammonia, autocatalytic removal of Al, and epitactic reorganization into a more silicic crystal; (ii) chelation with EDTA; (iii) ionic exchange replacement of Na by ions of higher potential and autocatalytic Al removal͞epitaxial recrystallization (e.g., the as-synthesized Na-Type Linde Type A zeolite framework loses Al at room temperature upon ion exchange with a 1 M CaCl 2 solution).…”

mentioning

confidence: 99%

Atmospheric weathering and silica-coated feldspar: Analogy with zeolite molecular sieves, granite weathering, soil formation, ornamental slabs, and ceramics

Smith

1998

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Feldspar surfaces respond to chemical, biological, and mechanical weathering. The simplest termination is hydroxyl (OH), which interacts with any adsorption layer. Acid leaching of alkalis and aluminum generated a silica-rich, nanometers-thick skin on certain feldspars. Natural K, Nafeldspars develop fragile surfaces as etch pits expand into micrometer honeycombs, possibly colonized by lichens. Most crystals have various irregular coats. Based on surfacecatalytic processes in molecular sieve zeolites, I proposed that some natural feldspars lose weakly bonded Al-OH (aluminol) to yield surfaces terminated by strongly bonded Si-OH (silanol). This might explain why some old feldspar-bearing rocks weather slower than predicted from brief laboratory dissolution. Lack of an Al-OH infrared frequency from a feldspar surface is consistent with such a silanol-dominated surface. Raman spectra of altered patches on acid-leached albite correspond with amorphous silica rather than hydroxylated silica-feldspar, but natural feldspar may respond differently. The crystal structure of H-exchanged feldspar provides atomic positions for computer modeling of complex ideas for silica-terminated feldspar surfaces. Natural weathering also depends on swings of temperature and hydration, plus transport of particles, molecules, and ionic complexes by rain and wind. Soil formation might be enhanced by crushing granitic outcrops to generate new Al-rich surfaces favorable for chemical and biological weathering. Ornamental slabs used by architects and monumental masons might last longer by minimizing mechanical abrasion during sawing and polishing and by silicifying the surface. Silica-terminated feldspar might be a promising ceramic surface.Chemical and physical changes in minerals underlie many aspects of human welfare. Agriculture depends on the interaction of soils with water, ionic and molecular species, and biological organisms. The weathering of feldspar minerals (1-4) from bedrock into clays is important for the production of food. Many laboratory experiments have measured the dissolution rate of feldspar minerals by water containing a wide range of ionic and molecular species, including organic acids relevant to biological weathering. Data are available for the range of feldspar chemistry from strongly acid to alkaline conditions (2, 3). Electron and chemical microscopy of feldspar surfaces is revealing a wealth of information on chemical and physical changes, including pitting, honeycombing, and selective dissolution (5). Only scattered data are available for the rate of weathering of feldspars in natural watersheds, but they indicate that natural atmospheric weathering of many rocks is slower than for short term laboratory experiments of crushed samples (2, 3). Casual examination of granite slabs in cemeteries and city buildings indicates that the alkali feldspars are weathering slowly unless mechanical spalling is occurring.

show abstract

Interaction of water with the zeolite HY, studied by FT i.r.

Cited by 53 publications

References 9 publications

Catalytically active and selective centers for production of ɛ-caprolactam through liquid phase Beckmann rearrangement over H-USY catalyst

Catalytically active and selective centers for production of ɛ-caprolactam through liquid phase Beckmann rearrangement over H-USY catalyst

Quantum chemical calculation of infrared spectra of acidic groups in chabazite in the presence of water

Atmospheric weathering and silica-coated feldspar: Analogy with zeolite molecular sieves, granite weathering, soil formation, ornamental slabs, and ceramics

Contact Info

Product

Resources

About