Spectroscopic Characterization and Catalytic Activity of Zeolite X Containing Occluded Alkali Species

Doskocil, Eric J.; Davis, Robert J.

doi:10.1006/jcat.1999.2676

Cited by 54 publications

(36 citation statements)

References 44 publications

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“…Peaks A, B, and C can be assigned to stretching modes of C─O bonds with intermediate strength as those involved in carbonates in ionic compounds. It has been well known for several decades that CO 2 can be adsorbed at ambient pressure on the surface of basic metal oxides and a variety of zeolites that contain transition, alkali, or alkaline earth metals (20)(21)(22)(23)(24)(25)(26)(27). The adsorption results in the formation of unidentate and bidentate carbonates (see Fig.…”

Section: Resultsmentioning

confidence: 99%

Silicon carbonate phase formed from carbon dioxide and silica under pressure

Santoro

Gorelli

Haines

et al. 2011

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

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The discovery of nonmolecular carbon dioxide under high-pressure conditions shows that there are remarkable analogies between this important substance and other group IV oxides. A natural and long-standing question is whether compounds between CO 2 and SiO 2 are possible. Under ambient conditions, CO 2 and SiO 2 are thermodynamically stable and do not react with each other. We show that reactions occur at high pressures indicating that silica can behave in a manner similar to ionic metal oxides that form carbonates at room pressure. A silicon carbonate phase was synthesized by reacting silicalite, a microporous SiO 2 zeolite, and molecular CO 2 that fills the pores, in diamond anvil cells at 18-26 GPa and 600-980 K; the compound was then temperature quenched. The material was characterized by Raman and IR spectroscopy, and synchrotron X-ray diffraction. The experiments reveal unique oxide chemistry at high pressures and the potential for synthesis of a class of previously uncharacterized materials. There are also potential implications for CO 2 segregation in planetary interiors and for CO 2 storage.high-pressure chemistry | material science | optical spectroscopy C arbon dioxide and silicon dioxide are two archetypal, group IV oxides of paramount importance for fundamental and applied chemistry and planetary sciences. CO 2 is the dominant component of the atmosphere of Earth-like planets, exists in icy forms in outer planets and asteroids, plays an important role in volcanic and seismic processes, is used as a supercritical solvent for chemical reactions, and its anthropogenic production is a major environmental issue. SiO 2 is also one of the most abundant components of terrestrial planets, and an important technological material. The chemical relationship between CO 2 and SiO 2 , in particular their reactivity, is thus of interest. Although the two systems are both group IV oxides, they are remarkably different under ambient conditions, because CO 2 is molecular and is held together by C═O double bonds, whereas SiO 2 forms network structures involving single Si─O bonds. These bonding patterns radically change under pressure. Two nonmolecular CO 2 crystalline phases and a glassy form have been discovered above 30 GPa that bear similarities to SiO 2 (1-14). The crystalline phases contain carbon in fourfold coordination by oxygen (1-10, 13, 14), and mixtures of CO 4 and CO 3 units have been found in a glassy form that has been named carbonia (13).A possible approach to favor the chemical reaction between CO 2 and SiO 2 is to select a microporous silica polymorph, such as silicalite. At ambient conditions, silicalite is characterized by a framework of four-, five-, six-, and ten-membered rings of SiO 4 tetrahedra with 5.5-Å pores (15) (Fig. 1, Left Inset). Recently, it has been found that the pores can be completely filled by simple molecules such as CO 2 and Ar under pressure, which prevents pressure-induced amorphization (PIA) and stabilizes the crystalline framework up to at least 25 GPa at room temperature (1...

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Section: Resultsmentioning

confidence: 99%

Silicon carbonate phase formed from carbon dioxide and silica under pressure

Santoro

Gorelli

Haines

et al. 2011

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

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“…10 20 The IR spectra of figure 3 show therefore that zeolites NaY and CsY12 form essentially bidentate carbonate species. Nevertheless, the IR bands on CsY12 were slightly shifted toward the positions of unidentate carbonate species, suggesting an increase of the surface oxygen basicity [20]. Bidentate carbonates species on NaY zeolite disappear after evacuation at 373 K; in contrast, a fraction of the bidentade carbonate species remains adsorbed on the CsY12 surface after outgassing at 373 K. This confirms that zeolite CsY12 contains stronger basic sites than NaY, and is consistent with an increase in the basicity of framework oxygens upon exchange of Na by a cation of lower electronegativity.…”

Section: Catalyst Characterizationmentioning

confidence: 96%

Side-chain alkylation of toluene with methanol on Cs-exchanged NaY zeolites: effect of Cs loading

et al. 2005

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The side-chain alkylation of toluene with methanol was studied on Cs-exchanged NaY zeolites containing up to 31% Cs (exchange degree, ED, up to 70%). Formation of styrene and ethylbenzene was significant only on Na(Cs)Y zeolites of ED higher than about 40%. Bimolecular side-chain alkylation reaction would require a proper surface geometric configuration of O d) -Cs + pairs that is achieved only on Cs-rich zeolites. In contrast, the side reaction forming carbon monoxide from methanol increases monotonically with increasing ED because it is essentially controlled by the basicity of the oxygen lattice.

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“…The basic properties of zeolites brought by cations allow a strong capitation of acidic molecules by enhancing the electron density of the framework oxygen [22,23]. The basic strength of these sites increases with the electropositivity of exchangeable cations [24]. More specifically, certain works have indicated that the basic strength of cationic zeolites containing the cations of Group 1A increases as following: Li + < Na + < K + < Rb + < Cs + [25,26].…”

Section: Influence Of the Structural Characteristics Of Zeolites On Tmentioning

confidence: 99%

“…In the case of several cationic zeolites, the chemical adsorption of CO 2 is accompanied by the formation of carbonates including very stable monodentate or unidentate carbonates and bidentate carbonates, at their surface, due to the interaction of CO 2 with the oxygen bridging aluminum and silicon atoms [24,35,[58][59][60][61][62]. Gallei and Stumpf [58] have described the formation of monodentate carbonate at the surface of zeolite CaY by a reaction involving three steps.…”

Section: Influence Of the Carbonates Formation On The C O 2 Adsorptionmentioning

confidence: 99%

Advances in principal factors influencing carbon dioxide adsorption on zeolites

Bonenfant

Kharoune

Niquette

et al. 2008

Science and Technology of Advanced Materials

263

179

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We report the advances in the principal structural and experimental factors that might influence the carbon dioxide (CO 2 ) adsorption on natural and synthetic zeolites. The CO 2 adsorption is principally govern by the inclusion of exchangeable cations (countercations) within the cavities of zeolites, which induce basicity and an electric field, two key parameters for CO 2 adsorption. More specifically, these two parameters vary with diverse factors including the nature, distribution and number of exchangeable cations. The structure of framework also determines CO 2 adsorption on zeolites by influencing the basicity and electric field in their cavities. In fact, the basicity and electric field usually vary inversely with the Si/Al ratio. Furthermore, the CO 2 adsorption might be limited by the size of pores within zeolites and by the carbonates formation during the CO 2 chemisorption. The polarity of molecules adsorbed on zeolites represents a very important factor that influences their interaction with the electric field. The adsorbates that have the most great quadrupole moment such as the CO 2 , might interact strongly with the electric field of zeolites and this favors their adsorption. The pressure, temperature and presence of water seem to be the most important experimental conditions that influence the adsorption of CO 2 . The CO 2 adsorption increases with the gas phase pressure and decreases with the rise of temperature. The presence of water significantly decreases adsorption capacity of cationic zeolites by decreasing strength and heterogeneity of the electric field and by favoring the formation of bicarbonates. The optimization of the zeolites structural characteristics and the experimental conditions might enhance substantially their CO 2 adsorption capacity and thereby might give rise to the excellent adsorbents that may be used to capturing the industrial emissions of CO 2 .

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Spectroscopic Characterization and Catalytic Activity of Zeolite X Containing Occluded Alkali Species

Cited by 54 publications

References 44 publications

Silicon carbonate phase formed from carbon dioxide and silica under pressure

Silicon carbonate phase formed from carbon dioxide and silica under pressure

Side-chain alkylation of toluene with methanol on Cs-exchanged NaY zeolites: effect of Cs loading

Advances in principal factors influencing carbon dioxide adsorption on zeolites

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