Synergetic effects of Cu-Zn bimetallic ions exchanged in NaX on acid sites of M(x)X zeolites (M = Cu2+ and/or Zn2+, x = level of exchange). An in situ FTIR study using pyridine adsorption/desorption

2019 ◽  
Vol 107 (3) ◽  
pp. 304
Author(s):  
Habib Hammoudi ◽  
Souhila Bendenia ◽  
Isabelle Batonneau-Gener ◽  
Jean-dominique Comparot ◽  
Kheira Marouf-Khelifa ◽  
...  
Keyword(s):  
Synergetic Effect ◽  
Nitrogen Adsorption ◽  
Acid Sites ◽  
Lewis Acidity ◽  
Pyridine Adsorption ◽  
In Situ Ftir ◽  
Desorption Temperature ◽  
X Zeolites ◽  
Adsorption Desorption

X zeolites were prepared by ion-exchange with Cu2+ and/or Zn2+ cations, at different concentrations of the exchange solution, and characterized by thermal analysis and nitrogen adsorption. The acidity of the samples was investigated by pyridine adsorption–desorption followed by in situ Fourier transform infrared (FTIR) spectroscopy. Desorption was carried out at 150, 250 and 350 °C. The objective is to estimate the nature and concentration of acid sites. A comparison between the binary (Cu(x)X, Zn(x)X) and ternary (CuZn(x)X) exchanges was also established (x = level of exchange) through the Cu(43)X, Zn(48)X and CuZn(50)X samples. Lewis acidity decreases overall with desorption temperature and the level of exchange. As the latter increases, there is a conversion of some Lewis sites into those of Brønsted during thermal treatment. In return, the concentration of Brønsted sites increases with the degree of exchange. The Brønsted acidity of CuZn(50)X at 350 °C is more important than the sum of those of Cu(43)X and Zn(48)X with respectively values of 73, 32 and 15 μmol g−1. Besides, the concentration of Brønsted sites for CuZn(50)X increases with desorption temperature. These features indicate the presence of a synergetic effect amplifying the strength of these sites when Cu2+ and Zn2+ cations compete for the occupancy of sites distributed in zeolite cavities.

Designing of In Situ FTIR Cell and its Application

2014 ◽  
Vol 900 ◽  
pp. 390-393
Author(s):  
Ming Jian Luo ◽  
Bing Hu ◽  
Xin Yue Liu
Keyword(s):  
Acid Sites ◽  
Acid Strength ◽  
Ftir Spectra ◽  
Pyridine Adsorption ◽  
In Situ Ftir ◽  
Acid Amount ◽  
Ftir Study ◽  
Easy Operation ◽  
Mcm 41

An easy-operation in-situ FTIR cell is designed and used for the investigation of dehydroxylation and pyridine adsorption FTIR study. The dehydroxylation FTIR spectra of MCM-41 indicate that the isolated, geminal, and oxygen perturbed silanol vibrated at about 3745, 3735 and 3520 cm-1, respectively. Py-FTIR spectra indicate that MCM-41 has none Lewis and Brönsted acid sites while the acid amount and acid strength of AlMCM-41 increase with the decrease of Si/Al.

In-situ FTIR to unravel the bifunctional nature of aromatics hydrogenation synergy on zeolite / metal catalysts

2022 ◽  
Author(s):  
Nuno Batalha ◽  
Jean-Dominique Comparot ◽  
Anthony Le Valant ◽  
Ludovic Pinard
Keyword(s):  
Catalytic Performance ◽  
Acid Sites ◽  
Metal Catalysts ◽  
In Situ Ftir

Acid sites, in particular Brønsted sites, are often reported to enhance the catalytic performance of metal catalysts, like platinum, in hydrogenation. The significant boost in catalytic performance suggests a bifunctional...

The Application of Mesoporous ZSM-5 Zeolite in the ULSD Catalysts

2020 ◽  
Vol 4 (4) ◽  
pp. 1-3
Author(s):  
Liu L
Keyword(s):  
Catalytic Performance ◽  
Nitrogen Compounds ◽  
In Situ Ftir ◽  
X Ray Diffraction ◽  
N2 Adsorption ◽  
X Ray ◽  
Acidic Sites ◽  
Adsorption Desorption ◽  
Al2o3 Catalyst

The mesoporous ZSM-5 zeolite containing MoCoP/Al2O3 catalyst (C12-ZSM5) with the mixture of Al2O3 and mesoporous ZSM- 5 zeolite as carrier was synthesized. The catalytic performance of C12-ZSM5 catalyst was evaluated by the hydrodesulfurization (HDS) of different diesel feedstock. The carriers and catalysts were characterized by N2 adsorption-desorption, pyridine-FTIR, X-ray diffraction (XRD) and CO in-situ FTIR (CO-FTIR) techniques. Results showed that mesoporous ZSM-5 can improve the acidity of the catalyst and increase the number of MoCoS active phases. The C12-ZSM5 catalyst had low HDS and HDN activity, because the acidic sites of mesoporous ZSM-5 were easily occupied by nitrogen compounds. The HDS activity of C12-ZSM5 catalyst was fully exploited by using graded packing technology, the sulfur content of product oil was 5.9 ng/μL. The relative HDS activity of C12-ZSM5 catalyst is 1.47 times that of FHUDS-8 catalyst.

In situ determination of Brønsted/Lewis acidity on cation-exchanged clay mineral surfaces by ATR-IR

Clay Minerals ◽  
1996 ◽  
Vol 31 (4) ◽  
pp. 513-522 ◽  
Author(s):  
J. Billingham ◽  
C. Breen ◽  
J. Yarwood
Keyword(s):  
Acid Sites ◽  
Lewis Acidity ◽  
Attenuated Total Reflectance ◽  
Mineral Surfaces ◽  
Lewis Acid Sites ◽  
Absorption Bands ◽  
Total Reflectance ◽  
Liquid Benzene

AbstractAttenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy has been used to determine the nature of acid sites present in Na+-, Ni2+- and Al3+-exchanged montmorillonite using the diagnostic base, pyridine. The pyridine additions were performed in situ at 25°C in the presence of liquid benzene or deuterated 1,4-dioxan to ascertain whether the acidity profile was influenced by the presence of either the non-polar or oxygenated solvent. Pyridine treated Ni2+-montmorillonite exhibited absorption bands characteristic of Lewis bound base in both benzene and deuterated 1,4-dioxan indicating that the Lewis acid sites were present at low temperature and were accessible in both solvents. The presence of a strong 1537 cm−1 band in pyridine-saturated Al3+-montmorillonite confirmed that this clay acted as a Brønsted acid in benzene. However, this diagnostic band was significantly reduced in the presence of deuterated 1,4-dioxan.

Preparation and Characterization of Cobalt Modified Rectorite

2013 ◽  
Vol 773 ◽  
pp. 263-266 ◽  
Author(s):  
Xiao Rong Zhao ◽  
Li Hua Zhu ◽  
He Qing Tang
Keyword(s):  
Nitrogen Adsorption ◽  
Interlayer Spacing ◽  
X Ray Diffraction ◽  
Step Method ◽  
Bet Specific Surface Area ◽  
Pore Properties ◽  
Adsorption Desorption ◽  
Resultant Material

Cobalt modified rectorite (Co@R) was prepared from sodium saturated rectorite (Na-R) with a two-step method of microwave-assisted ion-exchange and in-situ hydrolysis. The morphology, composite structure and pore properties of Co@R were observed with scanning electron microscopy (SEM), small angle X-ray Diffraction (XRD) and nitrogen adsorption-desorption isotherm. The adsorption ability and catalytic behavior of Co@R were studied with methyl blue (MB) as probe contaminant. The interstratified layered Na-R was stripped fully and the resultant material remained the layered structure with a slit-shaped pore between the layers of lamellar particles. The interlayer spacingd001of rectorite was increased successfully from 2.23 nm up to 2.72 nm. The Co@R has a BJH pore volume of 0.091 cm3g-1resulting from the macropores and BET specific surface area of 28.5 m2g-1. A set of test has shown that Co@R possesses the potential to become a good adsorbent and catalyst for activating peroxymonosulfate (PMS), removing organic pollutants efficiently.

scholarly journals In Situ Recrystallization of Mesoporous Carbon–Silica Composite for the Synthesis of Hierarchically Porous Zeolites

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1640 ◽  
Author(s):  
Jun Du ◽  
Yan Wang ◽  
Yan Wang ◽  
Ruifeng Li
Keyword(s):  
Mesoporous Carbon ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Hierarchical Zeolites ◽  
Hierarchically Porous ◽  
Silica Composite ◽  
Crystallization Procedure ◽  
Cracking Reaction ◽  
Adsorption Desorption

Hierarchically porous ZSM-5 was prepared by utilizing a two-step crystallization procedure with carbon–silica composites as precursors. The hierarchically porous zeolites obtained a regular mesoporous structure with aluminum incorporated into the carbon–silica composite frameworks. The carbon–silica composite zeolites were characterized by XRD, TEM, SEM, and nitrogen adsorption/desorption. As-prepared hierarchical zeolites were used in the 1,3,5-triisopropylbenzene (TIPB) cracking reaction and exhibited significantly high TIPB conversion, while the accessibility factors were also determined.

scholarly journals Synthesis and characterization of zeolite NaX from Bangka Belitung Kaolin as alternative precursor

2018 ◽  
Vol 14 (4) ◽  
pp. 414-418 ◽  
Author(s):  
Vita Nur Iftitahiyah ◽  
Didik Prasetyoko ◽  
Hadi Nur ◽  
Hasliza Bahruji ◽  
Hartati Hartati
Keyword(s):  
Average Pore Size ◽  
Surface Acidity ◽  
Microscopic Analysis ◽  
Acid Sites ◽  
Lewis Acidity ◽  
Zeolite X ◽  
Average Pore ◽  
Zeolite Nax ◽  
Type Iv ◽  
Adsorption Desorption

The potential use of kaolin as silica and alumina precursor for the synthesis of zeolite NaX was investigated in this study. The synthesis involved three steps of reactions; the preparation of seed gel, the formation of feedstock gel using kaolin and the combination of overall gel followed by hydrothermal treatment at 105°C for 12 hours. Analysis using X-ray Diffraction (XRD) method indicated the transformation of kaolin into pure phase zeolite NaX with a small amount of kaolin was still visible. Detail microscopic analysis showed the morphology of zeolite X consisted of octahedral particles with a crystallite diameter of 20-30 µm. Analysis of surface acidity using pyridine as probe molecule indicated the zeolite X has high Brǿnsted acidity with 0.181 mmol/g of acid sites, significantly higher than Lewis acidity ~0.053 mmol/g. The N2 adsorption-desorption measurement indicated a type IV material with both microporous and mesoporous structures with an average pore size of 1.47 nm for micropore and 3.41 nm for mesoporous.

scholarly journals Synthesis of Nb/MCM-48 material using rice husk ash as silica source with different SI/NB molar ratios

2021 ◽  
Vol 45 (171) ◽  
pp. 85-95
Author(s):  
Victor De Aguilar Pedott ◽  
Iemedelais Bordin ◽  
Carolina Elisa Demaman Oro ◽  
Ricardo Jorge Macieski ◽  
Diego Ivan Petkowicz ◽  
...  
Keyword(s):  
Rice Husk ◽  
Rice Husk Ash ◽  
Nitrogen Adsorption ◽  
Structure Directing Agent ◽  
Alternative Source ◽  
Molar Ratios ◽  
Silica Source ◽  
In Situ Deposition ◽  
Adsorption Desorption

The large amount of rice produced in Brazil generates a large volume of co-products, such as, Rice Husk (RH) and Rice Husk Ash (RHA). These co-products have amounts of silicon (Si) present in their structure, which can be used to synthesize silica-based materials as zeolites and MCM-type structures. The synthesis of MCM-48 material was carried out at room temperature, using the ionic liquid [C16MI·Cl] as structure-directing agent, depositing the niobium in situ during the synthesis with different molar ratios of Si/Nb (5, 20, 50 and 80). The material obtained was subjected to characterization by X-Ray Diffraction (XRD), Nitrogen Adsorption/Desorption isotherms and Scanning Electron Microscopy (SEM). The results confirm the formation of Nb/MCM-48 materials, in which their properties are consistent with those described in the literature. The deposition of Nb on MCM-48 did not change its structural properties, such as specific surface area and pore distribution for Si/Nb higher than 5. The results obtained demonstrate the success in the synthesis of mesoporous materials Nb/MCM-48 using industrial residues of rice as an alternative source of silicon, and in situ deposition of the niobium metal on the structure.

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