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.

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.

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 Sintesis Dan Karakterisasi H-Aluminosilikat Sebagai Katalis Sintesis Biogasoline Dari Asam Oleat

2019 ◽  
Vol 4 (2) ◽  
pp. 100
Author(s):  
Deasi Adhiani Farida ◽  
Abdulloh Abdulloh ◽  
Ahmadi Jaya Permana
Keyword(s):  
Oleic Acid ◽  
Hydrothermal Method ◽  
Lewis Acid ◽  
Acid Site ◽  
Lewis Acid Site ◽  
Bronsted Acid ◽  
Bronsted Acid Site ◽  
Brønsted Acid Site ◽  
Brönsted Acid ◽  
Cracking Reaction

ABSTRACT          Aluminosilicate can be used for cracking reaction. In this study, catalyst of H-aluminosilicate has been synthesized by hydrothermal method with ratio molar Si/Al is 20. The characterizations has been performed by XRD, FTIR and acidity test. Characterization by XRD showed that catalyst of H-aluminosilicate have structure amorphous, while FTIR showed Si-O-Al bond at 457 cm-1. The acidity test showed that catalyst of H-aluminosilicate have Brønsted acid site 0.0272 mmol/g and Lewis acid site 0.0005 mmol/g. Oleic acid was cracking at 340 oC for 3 and 5 hours. The product has been analyzed by GC-MS not showed compound forming biogasoline.Keywords: H-aluminosilicate, biogasoline, oleic acid ABSTRAK          Aluminosilikat dapat digunakan sebagai katalis dalam reaksi prengkahan. Pada penelitian ini telah dilakukan sintesis katalis H-aluminosilikat melalui metode hidrotermal dengan rasio Si/Al sebesar 20. Karakterisasi yang telah dilakukan meliputi uji XRD, FTIR, dan keasaman.Hasil XRD menunjukkan katalis H-aluminosilikat berbentuk amorf, sedangkan pada FTIR menunjukkan ikatan Si-O-Al pada bilangan gelombang 457 cm-1. Uji situs asam menunjukkan katalis H-aluminosilikat memiliki jumlah asam Brønsted sebesar 0.0272 mmol/g dan jumlah sisi asam Lewis sebesar 0.0005 mmol/g. Proses perengkahan asam oleat telah dilakukan pada suhu 340oC selama 3 jam dan 5 jam. Produk cracking yang diuji dengan GC-MS tidak menunjukkan pembentukan senyawa biogasoline.Kata kunci: H-aluminosilikat, biogasoline, asam oleat

Lewis Acid Site-Promoted Single-Atomic Cu Catalyzes Electrochemical CO2 Methanation

Nano Letters ◽  
2021 ◽  
Author(s):  
Shenghua Chen ◽  
Bingqing Wang ◽  
Jiexin Zhu ◽  
Liqiang Wang ◽  
Honghui Ou ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Acid Site ◽  
Lewis Acid Site ◽  
Co2 Methanation

scholarly journals Glucose Conversion into 5-Hydroxymethylfurfural over Niobium Oxides Supported on Natural Rubber-Derived Carbon/Silica Nanocomposite

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Rujeeluk Khumho ◽  
Satit Yousatit ◽  
Chawalit Ngamcharussrivichai
Keyword(s):  
Natural Rubber ◽  
Lewis Acid ◽  
Value Added ◽  
Acid Sites ◽  
Superior Performance ◽  
Lewis Acidity ◽  
Lewis Acid Sites ◽  
Niobium Oxides ◽  
Silica Nanocomposite ◽  
Loading Amount

5-Hydroxymethylfurfural (HMF) is one of the most important lignocellulosic biomass-derived platform molecules for production of renewable fuel additives, liquid hydrocarbon fuels, and value-added chemicals. The present work developed niobium oxides (Nb2O5) supported on mesoporous carbon/silica nanocomposite (MCS), as novel solid base catalyst for synthesis of HMF via one-pot glucose conversion in a biphasic solvent. The MCS material was prepared via carbonization using natural rubber dispersed in hexagonal mesoporous silica (HMS) as a precursor. The Nb2O5 supported on MCS (Nb/MCS) catalyst with an niobium (Nb) loading amount of 10 wt.% (10-Nb/MCS) was characterized by high dispersion, and so tiny crystallites of Nb2O5, on the MCS surface, good textural properties, and the presence of Bronsted and Lewis acid sites with weak-to-medium strength. By varying the Nb loading amount, the crystallite size of Nb2O5 and molar ratio of Bronsted/Lewis acidity could be tuned. When compared to the pure silica HMS-supported Nb catalyst, the Nb/MCS material showed a superior glucose conversion and HMF yield. The highest HMF yield of 57.5% was achieved at 93.2% glucose conversion when using 10-Nb/MCS as catalyst (5 wt.% loading with respect to the mass of glucose) at 190 °C for 1 h. Furthermore, 10-Nb/MCS had excellent catalytic stability, being reused in the reaction for five consecutive cycles during which both the glucose conversion and HMF yield were insignificantly changed. Its superior performance was ascribed to the suitable ratio of Brønsted/Lewis acid sites, and the hydrophobic properties generated from the carbon moieties dispersed in the MCS nanocomposite.

On the nature of framework Brønsted and Lewis acid sites in ZSM-5

Zeolites ◽  
1997 ◽  
Vol 19 (4) ◽  
pp. 288-296 ◽  
Author(s):  
G.L. Woolery ◽  
G.H. Kuehl ◽  
H.C. Timken ◽  
A.W. Chester ◽  
J.C. Vartuli
Keyword(s):  
Lewis Acid ◽  
Acid Sites ◽  
Lewis Acid Sites ◽  
Brønsted And Lewis Acid
Sign in / Sign up

Export Citation Format

Share Document