Location and Reducibility of Ni Ions in HEU-Type Zeolites

Pozas, C. de las; López-Cordero, Rafael; Díaz-Águila, Carlos; Cora, M.; Roque‐Malherbe, R.

doi:10.1006/jssc.1995.1016

Cited by 21 publications

(11 citation statements)

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“…4). The first process characterized the release of physically adsorbed water from an energetically heterogeneous adsorbent as a zeolite [10], to be precise, since water was released at different temperatures, these fact means that it was linked with different adsorption energies to the framework. The second peak was related to the removal of coordinated water.…”

Section: Resultsmentioning

confidence: 99%

“…Water vapor adsorption in a complex porous systems as natural zeolites occurs something like that [5,10]: initially micropore filling, where the adsorption behavior is dominated nearly completely by the interactions of the adsorbate, and the pore wall; after that, at higher pressures, external surface coverage, consisting of monolayer, and multilayer adsorption on the walls of mesopores, and open macropores, and at last capillary condensation in the mesopores. In Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Water adsorption was measured gravimetrically at atmospheric pressure in air containing water vapor at different partial pressures [10,11]. To study carbon dioxide adsorption, isotherms were collected, in an upgraded Quantachrome Autosorb-1 automatic physisorption analyzer, the adsorption isotherms of CO 2 at 0 °C were collected for samples degassed at 300 °C for a period of three h in high vacuum (10 -6 Torr).…”

Section: Characterization Methodsmentioning

confidence: 99%

“…Natural zeolites are significant materials as adsorbents [6][7][8][9][10][11][12] materials, to be precise, more than 90 wt% of a single zeolitic phase in the mineral [11,21]. In this regard, the main reason to conduct this research is the modification of a highly pure natural zeolite adsorbent to produce an adsorbent comparable to synthetic zeolite.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, an experimental solution for this difficulty is the use of carbon dioxide adsorption at 0 °C instead of nitrogen at -196 °C, in order to apply the Dubinin adsorption isotherm to describe carbon dioxide adsorption. The obtained data can be used for the determination of the micropore volume and the calculation of the isosteric heat of adsorption in order to qualify the geometry and the nature of the interaction between carbon dioxide and the zeolite framework, allowing, in sum, the characterization of the geometry and the interactions within the adsorption space [5,10].…”

Section: Introductionmentioning

confidence: 99%

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Study of the Adsorption Space of Modified Clinoptilolites

Rolando¹,

Roque-Malherbe²,

Alba³

et al. 2013

JMSE-B

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Carbon dioxide (CO 2 ) adsorption is an important adsorbent characterization method and a significant industrial process. In separation and recovery technology, the adsorption of the CO 2 is important to reduce the concentration of this gas considered as one of the greenhouse gases. Natural zeolites, particularly clinoptilolite, are widely applied as adsorbents. In this regard, in the present research, the structure, composition and morphology of modified with hexafluorosilicate (HFSi) and orthophosphoric acid (H 3 PO 4 ) clinoptilolites were investigated by characterizations and measurements made with, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDAX) and gravimetric adsorption. Additionally, the surface Chemistry of the modified clinoptilolites was analyzed by applying diffuse reflectance fourier transform infrared spectrometry (DRIFTS). Further, the interaction of CO 2 within the adsorption space of these modified clinoptilolites and a synthetic ZSM-5 zeolite was studied with the help of adsorption measurements. After all, an appropriate theoretical methodology for the analysis of the XRD and adsorption data was applied. The calculated cell parameters of the tested are similar to those reported for a typical clinoptilolite of: a = 17.662 Ǻ, b = 17.911 Ǻ, c = 7.407 Ǻ and β = 116.40 The resolution of the TGA derivative profiles indicated the presence of two steps for water release, one of them represents the loss of majority of the water present in the micropores. This was evidenced as a broad peak centered at about 50 0 C for the CSW-HFSi-0.1, but at 100 °C for the samples CSW-HFSi-0.4. The SEM micrographs corresponding to the modified clinoptilolites, was evidenced that the CSW zeolite shows secondary particles exhibiting diameters from 3 to 40 μm, formed by primary clinoptilolite crystallites showing a crystallite size, Φ = 40 nm. The EDAX elemental analysis it can be demonstrated that the exchange process replaced about 85% of the charge compensating ions. The DRIFT spectra of the modified clinoptilolites, specifically, CSW-HFSi-0.1, show a narrow band at about: 3,740 cm -l corresponding to terminal silanol groups (Si-OH) and a band 3,600-3,650 cm -1 resulting from extra-framework Al-OH. With the precision of the measured micropore volumes related to the excellent fitting of the adsorption data by the D-R isotherm equation, it can be affirm that carbon adsorption took only place in the micropore region. The isosteric heat of adsorption calculated for the modified clinoptilolites was greater than those values reported of ZSM-5 zeolite, particle packing silica, dealuminated Y zeolite (DAY) Cd, Zn and Ni-nitroprussides and Cu-nitroprusside and a Ni-MOF. With the obtained result it can be concluded that the modified clinoptilolites with HFSi showed a quality as adsorbent comparable to commercial synthetic zeolites.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Characterization Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Study of the Adsorption Space of Modified Clinoptilolites

Rolando¹,

Roque-Malherbe²,

Alba³

et al. 2013

JMSE-B

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Characterisation of Zeolitic Materials with a HEU-Type Structure Modified by Transition Metal Elements: Definition of Acid Sites in Nickel-Loaded Crystals in the Light of Experimental and Quantum-Chemical Results

et al. 2001

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Nickel-loaded HEU-type zeolite crystals have been obtained by well-known synthetic procedures and characterised by X-ray fluorescence (XRF), scanning-electron microscopy/ energy-dispersive spectroscopy (SEM-EDS), FT-IR, diffuse reflectance UV/ Vis spectroscopy (DR(UV/Vis)S) and X-ray photoelectron spectroscopy (XPS) measurements as non-homoionic and non-stoichiometric substances containing exchangeable hydrated Ni2+ ions in the micropores and nickel hydroxide phases supported on the surface. Thermogravimetric analysis/differential gravimetry (TGA/DTG) and differential thermal analysis (DTA) demonstrated that full dehydration below approximately 400 degrees C follows a clearly endothermic process, whereas at higher temperatures the zeolite is amorphised and finally partially recrystallised to Ni(Al,Si) oxides, detected by powder X-ray powder diffraction (XRD). The solid acidity of NiHEU, initially determined by temperature-programmed desorption (TPD) of ammonia to be 8.93 mgg(-1) NH3, is attributed to the weak acid sites (fundamentally Lewis sites) resolved at approximately 183 degrees C, and to the strong acid sites (essentially Brønsted sites) resolved at approximately 461 degrees C in the TPD pattern. A more sophisticated study based on in situ/ex situ FT-IR with in situ/ex situ 27Al MAS NMR and pyridine (Py) as a probe molecule, revealed that the Lewis acid sites can be attributed primarily to Ni2+ ions, whereas the Brønsted ones can probably be associated with the surface-supported nickel hydroxide phases. The spectroscopic measurements in conjunction with powder XRD and 29Si MAS NMR data strongly suggest that distorted Al tetrahedra are formed during the dehydration process and Py chemisorption/complexation (NiHEU-Py), whereas the crystal structure is remarkably well preserved in the rehydrated material (NiHEU-Py/R). The structural, electronic, energetic and spectroscopic properties of all possible nickel(II) aqua and dihydroxy complexes absorbed in the zeolite micropores or supported on the zeolite surface were studied theoretically by density functional theory (DFT). The computed proton affinity, found to be in the range 182.0-210.0 kcalmol(-1), increases with increasing coordination number of the aqua and dihydroxy nickel(II) complexes.

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8.1.6.9 Heulandite and stilbite groups of tectosilicates

Burzo

2013

Tectosilicates

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Location and Reducibility of Ni Ions in HEU-Type Zeolites

Cited by 21 publications

References 0 publications

Study of the Adsorption Space of Modified Clinoptilolites

Study of the Adsorption Space of Modified Clinoptilolites

Characterisation of Zeolitic Materials with a HEU-Type Structure Modified by Transition Metal Elements: Definition of Acid Sites in Nickel-Loaded Crystals in the Light of Experimental and Quantum-Chemical Results

8.1.6.9 Heulandite and stilbite groups of tectosilicates

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