Magnesium oxide as a catalyst

Malinowski, S.; Szczepańska, S.; Słoczyński, J.

doi:10.1016/0021-9517(67)90008-5

Cited by 19 publications

(10 citation statements)

References 3 publications

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“…Interaction of {Pt[Mo(CO) 3 (C 5 H 5 )] 2 (PhCN) 2 } with MgO: Evidence from Infrared Spectra. The spectrum in the υ OH region representing the MgO support is characterized by strong bands at 3765 and 3748 cm -1 that are assigned to surface hydroxyl groups of MgO , (Figure A, spectrum 2). After slurring of {Pt[Mo(CO) 3 (C 5 H 5 )] 2 (PhCN) 2 } with MgO in pentane followed by solvent removal by evacuation at 25 °C, a number of new bands appeared in the spectrum (Figure A, spectrum 1).…”

Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Model MgO-Supported Catalysts with Pt−Mo Interactions

et al. 1996

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MgO-supported platinum and platinum-molybdenum catalysts were prepared from organometallic precursors and characterized structurally to determine how the nature of the bimetallic precursors and the treatment conditions affected the interaction between the two metals. Samples were prepared from [PtCl 2 (PhCN) 2 ], [PtCl 2 (PhCN) 2 ] + [Mo(CO) 6 ], and {Pt[Mo(CO) 3 (C 5 H 5 )] 2 (PhCN) 2 } and characterized by infrared and extended X-ray absorption fine structure (EXAFS) spectroscopies, transmission electron microscopy, and chemisorption of H 2 , CO, and O 2 . The samples were treated in H 2 at 400°C prior to most of the characterizations. Incorporation of Mo reduced the chemisorption of CO and of H 2 . EXAFS spectra measured at the Pt L III edge and at the Mo K edge showed substantial Pt-Mo contributions with a Pt-Mo coordination number of about 2 and an average distance of 2.63 Å for the sample prepared from {Pt[Mo(CO) 3 (C 5 H 5 )] 2 (PhCN) 2 }. In contrast, no significant Pt-Mo contribution was observed for the sample prepared from [PtCl 2 (PhCN) 2 ] + [Mo(CO) 6 ]. Electron micrographs and EXAFS results show that interaction between Pt and Mo ions in the former sample helped to maintain the platinum in a highly dispersed form, with supported platinum clusters being smaller than about 10 Å.

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Section: Resultsmentioning

confidence: 99%

Synthesis and Characterization of Model MgO-Supported Catalysts with Pt−Mo Interactions

et al. 1996

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“…6 The structural change of the surface molybdate on MgO could be induced by a change of the surface pH. However, it has been shown that the surface pH of MgO remains >8 after firing Mg-(OH) 2 at 600 °C, 23 and under this net pH the molybdate should still be isolated tetrahedral. 22,24 Moreover, while the net surface pH of the MgO/OH changes from >11 to >8, this effect cannot be totally separated from the underlying structural change of the Mg(OH) 2 to MgO.…”

Section: Discussionmentioning

confidence: 99%

Surface Structure of Highly Dispersed MoO₃ on MgO Using in Situ Mo L₃-Edge XANES

Bare

1998

Langmuir

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The evolution of the dispersed surface molybdate phase on high-surface-area magnesium oxide is studied as a function of weight loading of MoO3 and calcination temperature using in situ Mo L3-edge X-ray absorption near edge spectroscopy, in situ laser Raman spectroscopy, and thermogravimetry−mass spectroscopy. Under ambient, hydrated conditions, the magnesium support is present as magnesium hydroxide, rather than MgO, and the molybdate species is present on the surface as an isolated tetrahedral species for weight loadings of 5−20 wt % MoO3. Under these hydrated conditions the form of the molybdate species is controlled by the net surface pH at the point of zero charge and is the same as that observed in aqueous solution. As the catalyst is calcined in air, the molybdate species transforms from a tetrahedral species, MoO4, to an octahedral one, MoO6. This transformation occurs at the same temperature, ∼450 °C, as that at which the support changes from hydroxide to oxide. This transformation temperature is independent of the MoO3 loading. It is suggested that it is this support-induced structural change that drives the change in the form of the surface molybdate species and not the desorption of adsorbed water.

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“…The Mg/Al ratio affects the number of basic sites, according to the research of Nakatuska et al [36], and basic sites increase with the Mg/Al ratio. MgO content contributes with two types of basic sites, O2and OH -, on the surface, whereas Al2O3 does not contribute to strong basic sites on the surface [37]. The BET specific surface area, N2 adsorption and desorption isotherms, and pore size distribution were analysed at 77K, and data is shown in Fig.…”

Section: Removal Processmentioning

confidence: 99%

CO2 mineralisation of brines with regenerative hydrotalcites in a cyclical process

Zhang

Šiller

2021

Chemical Engineering Journal

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CO2 mineralisation is a process that can store the CO2 as a solid mineral permanently, to mitigate carbon emissions. Brines rich in alkaline earth metals present an attractive opportunity to trap CO2 in the form of insoluble carbonates. Moreover, this can be accomplished, as shown in this work, using flue gas concentrations of CO2 and at nearambient temperatures, eliminating the need for energy-intensive CO2 capture step and heating of dilute aqueous solutions. The conventional alkaline substances to neutralise the solution, such as sodium hydroxide or amines, are costly, and the processes required to regenerate them (e.g. distillation or electrolysis) are energy intensive, which hinders the feasibility of this CO2 sequestration approach. We herein developed a process to remove chloride anions from alkaline brines by ion exchange, using lamellar structured materials, namely hydrotalcites (HT).These HT, which are layered double hydroxides prepared by co-precipitation method, release hydroxyl groups in exchange for chloride, sufficiently raising the pH of brines to enable the precipitation of carbonates during CO2 mineralisation. Several calcined-HT were synthesized using different ratios of magnesium and aluminium content, and various reaction temperatures and solid-to-liquid ratios were investigated for chloride removal. Moreover, the HT materials are recyclable for multiple usage by taking advantage of the HT's 'memory effect' property.Gaseous CO2 and Na2CO3 solution were tested as the recharging agents, to replace the chloride anions from the spent HT interlayers and intercalate with HCO3or CO3 2-, followed by a calcination process to produce the reusable calcined-HT. Several reaction cycles were conducted to evaluate the reusable property. It was found that the chloride removal efficiency remains over 70% after five cycles, and calcium utilisation efficiency of the brine carbonation process can surpass 90%. This unique cyclical closed-loop HT process thus presents a more cost-and energy-effective approach to brine carbonation than previous studies. In addition, the produced carbonates are of sufficient quality for a variety of applications that can further reduce the process cost of this type of CO2 sequestration.

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Magnesium oxide as a catalyst

Cited by 19 publications

References 3 publications

Synthesis and Characterization of Model MgO-Supported Catalysts with Pt−Mo Interactions

Synthesis and Characterization of Model MgO-Supported Catalysts with Pt−Mo Interactions

Surface Structure of Highly Dispersed MoO₃ on MgO Using in Situ Mo L₃-Edge XANES

CO2 mineralisation of brines with regenerative hydrotalcites in a cyclical process

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Magnesium oxide as a catalyst

Cited by 19 publications

References 3 publications

Synthesis and Characterization of Model MgO-Supported Catalysts with Pt−Mo Interactions

Synthesis and Characterization of Model MgO-Supported Catalysts with Pt−Mo Interactions

Surface Structure of Highly Dispersed MoO3 on MgO Using in Situ Mo L3-Edge XANES

CO2 mineralisation of brines with regenerative hydrotalcites in a cyclical process

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Surface Structure of Highly Dispersed MoO₃ on MgO Using in Situ Mo L₃-Edge XANES