Nb-doped variants of high surface aluminium fluoride: a very strong bi-acidic solid catalyst

2019 ◽  
Vol 48 (20) ◽  
pp. 6834-6845 ◽  
Author(s):  
Clara Patricia Marshall ◽  
Gudrun Scholz ◽  
Thomas Braun ◽  
Erhard Kemnitz
Keyword(s):  
Lewis Acid ◽  
Aluminium Hydroxide ◽  
High Surface ◽  
Acid Sites ◽  
Solid Catalyst ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Aluminium Fluoride ◽  
Strong Lewis Acid

Novel aluminium Nb-doped fluoride catalysts were synthesized using an aluminium hydroxide precursor to afford solids where very strong Lewis acid sites coexist with Brønsted acid sites.

Synergy between Brønsted acid sites and Lewis acid sites

2008 ◽  
pp. 4631 ◽  
Author(s):  
Selvedin Telalović ◽  
Jeck Fei Ng ◽  
Rajamanickam Maheswari ◽  
Anand Ramanathan ◽  
Gaik Khuan Chuah ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

One-pot transformation of furfural into γ-valerolactone catalyzed by hierarchical Hf-Al-USY zeolite with balanced Lewis and Brønsted acid sites

2021 ◽  
Author(s):  
Bo Tang ◽  
Shuang Li ◽  
Wei-Chao Song ◽  
Yan Li ◽  
En-Cui Yang
Keyword(s):  
Lewis Acid ◽  
Value Added ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Lewis Acid Sites ◽  
One Pot ◽  
Usy Zeolite ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Brønsted And Lewis Acid

Upgrading of furfural to high value-added chemicals are currently an attractive and challenging route in biorefineries. Herein, hierarchically structured bifunctional Hf-Al-USY zeolite with balanced Brønsted and Lewis acid sites has...

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.

Effective co-sensitization using D–π–A dyes with a pyridyl group adsorbing at Brønsted acid sites and Lewis acid sites on a TiO2 surface for dye-sensitized solar cells

RSC Advances ◽  
2015 ◽  
Vol 5 (4) ◽  
pp. 2531-2535 ◽  
Author(s):  
Yousuke Ooyama ◽  
Koji Uenaka ◽  
Takafumi Sato ◽  
Naoyuki Shibayama ◽  
Joji Ohshita
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Pyridyl Group ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

Effective and convenient co-sensitization method for DSSC have been newly developed by employing two kinds of D–π–A dyes with pyridyl group capable of adsorbing at the Brønsted acid sites and the Lewis acid sites on TiO2 surface.

scholarly journals Design and control of Lewis acid sites in Sn-substituted microporous architectures

2016 ◽  
Vol 4 (15) ◽  
pp. 5706-5712 ◽  
Author(s):  
Khaled M. H. Mohammed ◽  
Arunabhiram Chutia ◽  
June Callison ◽  
Peter P. Wells ◽  
Emma K. Gibson ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Active Sites ◽  
Heterogeneous Catalysts ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Lewis Acid Sites ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Brönsted Acid Sites ◽  
And Control

Modulation of tetrahedral Sn(iv) active sites in framework architectures influences the generation of Lewis and Brønsted acid sites in heterogeneous catalysts.

Highly-efficient Ru/Al–SBA-15 catalysts with strong Lewis acid sites for the water-assisted hydrogenation of p-phthalic acid

2020 ◽  
Vol 10 (8) ◽  
pp. 2443-2451
Author(s):  
Cong Mao ◽  
Jingwei Zheng ◽  
Babasaheb M. Matsagar ◽  
Ranjith Kumar Kankala ◽  
Tansir Ahamad ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Phthalic Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Highly Efficient ◽  
Strong Lewis Acid ◽  
Exceptional Stability ◽  
Isomer Selectivity

A Ru/Al–SBA-15 catalyst with excess Lewis acid sites displayed excellent efficiency (100%), high cis-isomer selectivity (84%), and exceptional stability towards hydrogenation of p-phthalic acid in water.

Role of Zinc in Zn-Loaded ZSM-5 Zeolites in the Aromatization of n-Hexane

1999 ◽  
Vol 64 (1) ◽  
pp. 168-176 ◽  
Author(s):  
Edita Rojasová ◽  
Agáta Smiešková ◽  
Pavol Hudec ◽  
Zdenek Židek
Keyword(s):  
Solid State ◽  
Ion Exchange ◽  
Lewis Acid ◽  
Acid Site ◽  
Acid Sites ◽  
Partial Migration ◽  
Simultaneous Presence ◽  
Lewis Acid Sites ◽  
Strong Lewis Acid

Aromatization of n-hexane over zinc-modified ZSM-5 zeolites was investigated. It was shown that incorporation of zinc by ion exchange into cationic positions of NH4-ZSM-5 zeolite causes acid-site strength redistribution and generation of new relatively strong Lewis acid sites in zeolite increasing the selectivity of n-hexane aromatization in comparison with the parent NH4-ZSM-5 zeolite. Simultaneous presence of Lewis and Broensted acid sites in ZSM-5 zeolite does not affect the strength of Broensted acid sites in zeolite. For the activity/selectivity of aromatization of n-hexane on Zn-modified ZSM-5 zeolites, the amount of Zn and its localization in the cationic positions are decisive. The reaction of n-hexane can be also initiated by the Zn species alone in the cationic positions. ZnO species alone as an extraframework phase was found inactive in the catalyst for aromatization of n-hexane. The influence of ZnO addition on the performance of pure ammonium forms of ZSM-5 zeolites in n-hexane conversion is a result of partial migration of zinc into cationic positions of zeolite by solid-state ion exchange.

Direct synthesis of alkynylphosphonates from alkynes and phosphite esters catalyzed by Cu/Cu2O nanoparticles supported on Nb2O5

2018 ◽  
Vol 42 (16) ◽  
pp. 13957-13962 ◽  
Author(s):  
Tao Yuan ◽  
Fei Chen ◽  
Guo-ping Lu
Keyword(s):  
Lewis Acid ◽  
Synergistic Effects ◽  
Copper Catalyst ◽  
Direct Synthesis ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Strong Lewis Acid ◽  
Cu2o Nanoparticles

A new, recyclable and efficient copper catalyst for cross-couplings of alkynes and phosphite esters has been disclosed, in which the synergistic effects of Nb2O5 on the catalyst are found owing to its strong Lewis acid sites.

scholarly journals High Surface Area VOx/TiO2/SBA-15 Model Catalysts for Ammonia SCR Prepared by Atomic Layer Deposition

Catalysts ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1386
Author(s):  
Jun Shen ◽  
Christian Hess
Keyword(s):  
Atomic Layer Deposition ◽  
Lewis Acid ◽  
High Surface ◽  
High Surface Area ◽  
Atomic Layer ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
X Ray ◽  
Nox Conversion ◽  
Layer Deposition

The mode of operation of titania-supported vanadia (VOx) catalysts for NOx abatement using ammonia selective catalytic reduction (NH3-SCR) is still vigorously debated. We introduce a new high surface area VOx/TiO2/SBA-15 model catalyst system based on mesoporous silica SBA-15 making use of atomic layer deposition (ALD) for controlled synthesis of titania and vanadia multilayers. The bulk and surface structure is characterized by X-ray diffraction (XRD), UV-vis and Raman spectroscopy, as well as X-ray photoelectron spectroscopy (XPS), revealing the presence of dispersed surface VOx species on amorphous TiO2 domains on SBA-15, forming hybrid Si–O–V and Ti–O–V linkages. Temperature-dependent analysis of the ammonia SCR catalytic activity reveals NOx conversion levels of up to ~60%. In situ and operando diffuse reflection IR Fourier transform (DRIFT) spectroscopy shows N–Hstretching modes, representing adsorbed ammonia and -NH2 and -NH intermediate structures on Bronsted and Lewis acid sites. Partial Lewis acid sites with adjacent redox sites are proposed as the active sites and desorption of product molecules as the rate-determining step at low temperature. The high NOx conversion is attributed to the presence of highly dispersed VOx species and the moderate acidity of VOx supported on TiO2/SBA-15.

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