FT-IR study of the brønsted acidity of phosphated and sulphated silica catalysts

Lion, M.; Maache, M.; Lavalley, Jean‐Claude; Ramis, Gianguido; Busca, Guido; Rossi, Pier Francesco; Lorenzelli, V.

doi:10.1016/0022-2860(90)80303-2

Cited by 15 publications

(5 citation statements)

References 10 publications

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“…The IR spectrum of the activated MIL-91(Al) solid shows a sharp band present at 3688 cm –1 , which is characteristic of the bridging Al–OH–Al groups. The absence of a signal around 3670 cm –1 (Figure a) indicates that the P–OH groups are not free . The very broad band below 2300 cm –1 emphasizes that the piperazine N atoms interact with the acidic proton of the P–OH groups via the formation of either a P–OH···N hydrogen bond or a zwitterionic structure PO – ···NH + (Figure S9 in the SI).…”

Section: Resultsmentioning

confidence: 99%

“…The absence of a signal around 3670 cm −1 (Figure 6a) indicates that the P−OH groups are not free. 44 The very broad band below 2300 cm −1 emphasizes that the piperazine N atoms interact with the acidic proton of the P−OH groups via the formation of either a P−OH···N hydrogen bond or a zwitterionic structure PO − ···NH + ( Figure S9 in the SI). 22 Upon CO 2 adsorption, a new Al−OH band appears at 3705 cm −1 (Figure 6a).…”

Section: Resultsmentioning

confidence: 99%

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Structural Origin of Unusual CO₂Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

et al. 2015

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The adsorption of CO 2 , CH 4 , and N 2 at 303 K by MIL-91(Al), one of the few porous phosphonate-based-MOFs, has been investigated by combining advanced experimental and computational tools. Whereas CH 4 and N 2 adsorption isotherms exhibit type I behavior, the reversible CO 2 isotherm displays an unusual inflection point at low pressure. In situ X-ray powder diffraction and infrared spectroscopy showed structural changes of this small-pore MOF upon CO 2 adsorption. Grand canonical Monte Carlo simulations delivered a detailed picture of the adsorption mechanisms at the microscopic level. The so-predicted arrangements of the confined CO 2 molecules were supported by analysis of the in situ diffraction and infrared experiments. It was shown that while adsorbed CH 4 and N 2 are located mainly in the center of the pores, CO 2 molecules interact with the hydrogen-bonded POH−N acid−base pairs. This results in a relatively high adsorption enthalpy for CO 2 of ca. −40 kJ mol −1 , which suggests that this material might be of interest for CO 2 capture at low pressure (postcombustion).

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Structural Origin of Unusual CO₂Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

et al. 2015

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“…Among a large number of solid acids, catalysts with surface acidity stronger than H o = À8.2 include the binary oxides [1,2]. The use of anions, such as SO 2À 4 , PO 3À 4 , WO 2À 4 , CO 2À 3 , Cl À , F À and OH À , have been found to enhance the acidity and certain other physico-chemical properties of the different solids, including thermal stability and mesoporosity [3,4]. Ramis et al [5] observed a very strong increase of the Brö nsted acid strength of titania when doped by sulfate and tungstate ions.…”

Section: H 2 So 4 and H 3 Pomentioning

confidence: 99%

“…Before formation of the gel, two main steps may be distinguished: (i) hydrolysis of the organometallic compound (TEOS) and (ii) polycondensation of ethoxy ("SiAOEt) and silanol ("SiAOH) groups to form siloxanes ("SiAOASi"). In the sol-gel method, numerous hydrolysis catalysts have been employed, for example, HCl, HNO 3 …”

Section: Introductionmentioning

confidence: 99%

Sol–gel silica modified with phosphate and sulfate ions

Manríquez¹,

López²,

Gómez³

et al. 2004

Journal of Non-Crystalline Solids

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“…It has also been reported that sulfated SiO2 as solid acid catalyst is one of the modified silica gel products by reacting silica gel with sulfuric acid. The utilization of SO4 2anion display an increase in acidic properties of silica as well as physical properties [27,28].…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Mesoporous Silica Xerogel from Geothermal Sludge using Sulfuric Acid as Gelation Agent

Widiyandari

Pardoyo

Sartika

et al. 2021

IJE

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A large amount of sludge is produced by the geothermal brine at the Dieng Geothermal power plant, exceeding 165 tons per month. This sludge is generally not utilized, except for use in landfills. The precipitate (sludge) is primarily composed of silica. The aim of this research is to synthesis mesoporous silica (SiO2) xerogel from geothermal sludge (GS) and to investigate the effects of pH as an effort to elevate the economic value of sludge through alkaline extraction followed by acidification. SiO2 xerogel was prepared by extracting the GS to become sodium silicate (Na2SiO3) assisted by a base NaOH and precipitated using H2SO4 as a gelation agent. The FTIR analysis of the SiO2 xerogel showed a group of silanol (Si-OH) and siloxane (Si-O-Si). The XRD analysis indicated that SiO2 xerogel was amorphous. Furthermore, it was observed from nitrogen absorption-desorption using BET (Breneur-Emmet-Teller) method test that decreased pH tends to the specific surface area increase, and the pore size becomes decrease. The largest specific surface area observed at SiO2 xerogel prepared at pH of 5.5 reached 400.10 m 2 /g with a pore size of 4.5 nm. The pore sized for all cases was in the range of 4 ~12 nm, indicating that the SiO2 xerogels were mesoporous. Pore size of the as-prepared silica affected the thermal stability property of the sample.

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FT-IR study of the brønsted acidity of phosphated and sulphated silica catalysts

Cited by 15 publications

References 10 publications

Structural Origin of Unusual CO₂Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

Structural Origin of Unusual CO₂Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

Sol–gel silica modified with phosphate and sulfate ions

Synthesis of Mesoporous Silica Xerogel from Geothermal Sludge using Sulfuric Acid as Gelation Agent

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FT-IR study of the brønsted acidity of phosphated and sulphated silica catalysts

Cited by 15 publications

References 10 publications

Structural Origin of Unusual CO2Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

Structural Origin of Unusual CO2Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

Sol–gel silica modified with phosphate and sulfate ions

Synthesis of Mesoporous Silica Xerogel from Geothermal Sludge using Sulfuric Acid as Gelation Agent

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Product

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Structural Origin of Unusual CO₂Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF

Structural Origin of Unusual CO₂Adsorption Behavior of a Small-Pore Aluminum Bisphosphonate MOF