scholarly journals Effect of Stannic Species Modification on the Acidity of Silicalite-1 and Its Enhancement in Transforming Ethylenediamine to Heterocyclic Amines

Catalysts ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 211
Author(s):  
Yongxin Zhang ◽  
Long Lin ◽  
Xiaoming Zheng ◽  
Chunyan Liu ◽  
Quanren Zhu ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Precipitation Method ◽  
Catalyst Characterization ◽  
Lewis Acid Sites ◽  
Modified Zeolite ◽  
Weight Percentage ◽  
Ft Ir

In this study, a series of SnO2 modified zeolite catalysts (Snx-S-1; x is the weight percentage of Sn) were prepared with SnCl2 and a defective Silicalite-1 (S-1) zeolite via facile deposition–precipitation method. It was found that the stannic species modified all-silica zeolite catalysts were active for the intermolecular condensation of ethylenediamine (EDA) to 1, 2-Diazabicyclo [2, 2, 2] octane (TEDA) and piperazine (PIP). The best catalyst Sn6-S-1 (6 wt.% Sn loading) showed 86% EDA conversion and 93% total selectivity to TEDA and PIP. By contrast, the defective S-1 zeolite parent showed only approximately 9% EDA conversion under the same conditions. With the help of catalyst characterization techniques including hydroxyl vibration and pyridine adsorption FT-IR spectroscopy (transmission mode), the enhancement of the catalytic activity of the SnO2 modified zeolite catalysts (Snx-S-1) was mainly attributed to the formation of mild Lewis acid sites in the siliceous zeolite. Both the hydroxyl nests of the defective S-1 zeolite and the dispersed SnO2 clusters should be the important factors for the formation of mild Lewis acid sites on the modified zeolite. Based on the catalytic performance of the modified zeolite in the conversion of EDA to PIP and TEDA, it is inferred that the mildly acidified defective S-1 zeolite by the SnO2 deposition modification might become a very active and durable catalyst for reactions involving strongly alkaline reactants and products.

scholarly journals Effect of the calcination temperature of cerium–zirconium mixed oxides on the structure and catalytic performance of WO3/CeZrO2 monolithic catalyst for selective catalytic reduction of NOx with NH3

RSC Advances ◽  
2017 ◽  
Vol 7 (39) ◽  
pp. 24177-24187 ◽  
Author(s):  
Haidi Xu ◽  
Mengmeng Sun ◽  
Shuang Liu ◽  
Yuanshan Li ◽  
Jianli Wang ◽  
...  
Keyword(s):  
Low Temperature ◽  
Selective Catalytic Reduction ◽  
Lewis Acid ◽  
Mixed Oxides ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Reduction Of Nox ◽  
Calcined Temperature

The calcined temperature of the carrier obviously affected SCR activity of catalysts, WO3/Ce0.68Zr0.32O2-500 showed the best low-temperature NH3-SCR activity due to its more Lewis acid sites and stronger redox property.

scholarly journals MOFs vs. zeolites: carbonyl activation with M(iv) catalytic sites

2017 ◽  
Vol 7 (23) ◽  
pp. 5482-5494 ◽  
Author(s):  
Francisco G. Cirujano
Keyword(s):  
Lewis Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Comparative Review ◽  
Catalytic Sites

Comparative review of the catalytic performance of isolated tetravalent metals as Lewis acid sites in zeolite and MOF materials.

Brønsted and Lewis Acid Sites in Dealuminated ZSM-12 and β Zeolites Characterized by NH3-STPD, FT-IR, and MAS NMR Spectroscopy

2000 ◽  
Vol 104 (17) ◽  
pp. 4122-4129 ◽  
Author(s):  
Wenmin Zhang ◽  
Panagiotis G. Smirniotis ◽  
M. Gangoda ◽  
Rathindra N. Bose
Keyword(s):  
Nmr Spectroscopy ◽  
Lewis Acid ◽  
Acid Sites ◽  
Mas Nmr ◽  
Lewis Acid Sites ◽  
Ft Ir ◽  
Brønsted And Lewis Acid

scholarly journals Kinetics and Mechanism of Acetalisation of Furfural to Furfural Diethyl Acetal with Ni–Al Layered Double Hydroxides Containing Lewis Acid Sites

2018 ◽  
Vol 43 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Yali Du ◽  
Yalin Feng ◽  
Chunlei Zou ◽  
Xu Wu ◽  
Wei Huang
Keyword(s):  
Lewis Acid ◽  
Catalytic Mechanism ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Diethyl Acetal ◽  
Lewis Acid Sites ◽  
Hydrolysis Method ◽  
Catalytic Behaviour ◽  
Double Hydroxide ◽  
Double Hydroxides

The nitrate form of Ni–Al layered double hydroxide (denoted as Ni–Al–NO3-LDH) and the corresponding carbonate form (denoted as Ni–Al–CO3-LDH) were tunably fabricated by the hexamethylenetetramine hydrolysis method. A catalytic behaviour investigation proved Ni–Al–CO3-LDH to be an ineffective catalyst, while for Ni–Al–NO3-LDH excellent catalytic activity and reusability were obtained, in the acetalisation of furfural to furfural diethyl acetal. Characterisation and analysis revealed that the appearance of Lewis acid sites in Ni–Al–NO3-LDH was responsible for its excellent catalytic performance. The acquired kinetic parameters confirmed that this reaction was a first-order process and the apparent activation energy was 36.28 kJ mol−1, which is in reasonable agreement with the theoretical result of 38.57 kJ mol−1. Additionally, apart from the typical Brønsted acid catalytic mechanism, a possible Lewis acid catalytic mechanism was probed theoretically.

Catalytic Performance of Brønsted and Lewis Acid Sites in Phenylglyoxal Conversion on Flame-Derived Silica-Zirconia

ChemCatChem ◽  
2014 ◽  
Vol 6 (10) ◽  
pp. 2970-2975 ◽  
Author(s):  
Zichun Wang ◽  
Yijiao Jiang ◽  
Michael Hunger ◽  
Alfons Baiker ◽  
Jun Huang
Keyword(s):  
Lewis Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Brønsted And Lewis Acid

FT-IR Analysis of Pillared Clay Pore Structure via Adsorbed Bipyridine Surface Probe Species

1996 ◽  
Vol 50 (10) ◽  
pp. 1319-1324 ◽  
Author(s):  
Stephen A. Bagshaw ◽  
Ralph P. Cooney
Keyword(s):  
Lewis Acid ◽  
Spectroscopic Method ◽  
Acid Sites ◽  
Pillared Clay ◽  
Lewis Acid Sites ◽  
Surface Probe ◽  
Ft Ir ◽  
First Time ◽  
Ft Ir Spectroscopy

Adsorption interactions of the bidentate molecules 2,2'-bipyridine and 4,4'-bipyridine with the surfaces of different alumina-pillar interlayered clays have been investigated by FT-IR spectroscopy. These interactions were examined in an attempt to establish a spectroscopic method for the determination of interpillar distances in the galleries of pillared clays. 2,2'-Bipyridine adsorbs in a bidentate C2 v, interaction to single Lewis acid sites on the surfaces of individual pillars and not to adjacent pillars, indicating that the distances between binding sites on adjacent pillars are too great to be successfully probed by this molecule. 4,4'-Bipyridine maintains the D2 h symmetry of the free molecule through interaction with Lewis acid sites on two adjacent pillars simultaneously via both ends of the molecule, thereby exhibiting possible utility as a probe of the interpillar distance. Surface-adsorbed monoprotonated 2,2'-bipyridinium cations are formed through interaction with Brönsted acid sites on the pillared clay surfaces. The IR spectrum of the surface-adsorbed protonated species suggests C2/i transoid symmetry and is presented for the first time.

scholarly journals Phosphoric Acid Modification of Hβ Zeolite for Guaiacol Hydrodeoxygenation

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 962
Author(s):  
Xun Wang ◽  
Yongkang Lv ◽  
Shanhui Zhu ◽  
Xuefeng Wang ◽  
Cunbao Deng
Keyword(s):  
Phosphoric Acid ◽  
Lewis Acid ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Acid Property ◽  
Bronsted Acid ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Brönsted Acid Sites

Regulating the acid property of zeolite is an effective strategy to improve dehydration of intermediate alcohol, which is the rate-determining step in hydrodeoxygenation of lignin-based phenolic compounds. Herein, a commercial Hβ (SiO2/Al2O3 = 25) was modified by phosphoric acid, and evaluated in the catalytic performance of guaiacol to cyclohexane, combined with Ni/SiO2 prepared by the ammonia evaporation hydrothermal (AEH) method. Incorporating a small amount of phosphorus had little impact on the morphology, texture properties of Hβ, but led to dramatic variations in acid property, including the amount of acid sites and the ratio of Brønsted acid sites to Lewis acid sites, as confirmed by NH3-TPD, Py-IR, FT-IR and 27Al MAS NMR. Phosphorus modification on Hβ could effectively balance competitive adsorption of guaiacol on Lewis acid sites and intermediate alcohol dehydration on Brønsted acid sites, and then enhanced the catalytic performance of guaiacol hydrodeoxygenation to cyclohexane. By comparison, Hβ containing 2 wt.% phosphorus reached the highest activity and cyclohexane selectivity.

scholarly journals Brønsted/Lewis acid sites synergistically promote the initial C–C bond formation in the MTO reaction

2018 ◽  
Vol 9 (31) ◽  
pp. 6470-6479 ◽  
Author(s):  
Yueying Chu ◽  
Xianfeng Yi ◽  
Chengbin Li ◽  
Xianyong Sun ◽  
Anmin Zheng
Keyword(s):  
Lewis Acid ◽  
Acid Site ◽  
Bond Formation ◽  
Lewis Acid Site ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Lewis Acid Sites ◽  
Mto Reaction ◽  
Brønsted Acid Site ◽  
Initiation Step

The Lewis acid site combined with a Brønsted acid site in zeolite catalysts facilitates first C–C bond formation in the initiation step of the MTO reaction.

The fixation of CO2 by epoxides over nickel-pyrazolate-based metal–organic frameworks

2020 ◽  
Vol 44 (42) ◽  
pp. 18319-18325
Author(s):  
Zheng Wang ◽  
Qianjie Xie ◽  
Yajun Wang ◽  
Yu Shu ◽  
Cong Li ◽  
...  
Keyword(s):  
Comparative Study ◽  
Lewis Acid ◽  
Metal Organic Frameworks ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Cyclic Carbonates ◽  
Lewis Acid Sites ◽  
Metal Organic

Ni-based MOFs with Lewis acid sites was developed for CO2 fixation with epoxides into cyclic carbonates, and a comparative study shows that the density and accessibility of the Lewis acid sites in the MOFs greatly influence the catalytic performance.

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