Aromatization of C2-C6 Aliphatic Hydrocarbons on Copper-Containing ZSM-5 Zeolites

1992 ◽  
Vol 57 (12) ◽  
pp. 2553-2560
Author(s):  
Zdravka Popova ◽  
Katia Aristirova ◽  
Christo Dimitrov
Keyword(s):  
Copper Content ◽  
Acid Strength ◽  
The State ◽  
Aliphatic Hydrocarbons ◽  
Bronsted Acid ◽  
Ion Formation ◽  
Brönsted Acid ◽  
Wide Range ◽  
Carbenium Ion ◽  
Acid Centers

The aromatization of a wide range of model aliphatic and cycloaliphatic hydrocarbons (ethene, ethane, propene, n-hexane, 1-hexene, methylcyclopentane, cyclohexane, cyclohexene) on copper-containing NaZSM-5 and HZSM-5 zeolites has been investigated. It was established that the degree of aromatization is related to carbenium ion formation and depends on the acid strength and copper content of zeolite. Experiments with copper-containing samples reduced prior to use indicated the possibility to enhance the selectivity to aromatization. The change of the state of Cu2+ ions during catalytic experiments confirmed the assumption about participation of Cu0 simultaneously with the Bronsted acid centers in the dehydrogenation/hydrogenation steps.

Correlation between Brønsted Acid Strength and Local Structure in Zeolites

2009 ◽  
Vol 113 (44) ◽  
pp. 19208-19217 ◽  
Author(s):  
Naonobu Katada ◽  
Katsuki Suzuki ◽  
Takayuki Noda ◽  
German Sastre ◽  
Miki Niwa
Keyword(s):  
Local Structure ◽  
Acid Strength ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brönsted Acid

An ONIOM study of the distribution of skeletal aluminum and Brønsted acidity in ZSM-48 zeolite

2014 ◽  
Vol 13 (02) ◽  
pp. 1450019 ◽  
Author(s):  
Rui Liu ◽  
Jie Zhang ◽  
Xiuliang Sun ◽  
Chongpin Huang ◽  
Biaohua Chen
Keyword(s):  
Density Functional ◽  
Acid Sites ◽  
Acid Strength ◽  
Molar Ratio ◽  
Am1 Method ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Al Substitution ◽  
Brönsted Acid ◽  
Stretching Vibration

A density functional theory (DFT) study was performed on distribution of skeletal aluminum and Brønsted acid (B-acid) sites as well as the acid strength in ZSM-48 zeolite. The correlation between Si / Al molar ratio and the general acid strength was also investigated. The calculations were performed based on 51T and 90T cluster models by using two-layered ONIOM schemes (B3LYP/6-31G (d,p): AM1) method. The former 51T cluster is used for the calculation of single- Al substitution and the latter is for the multi- Al substitution study. The properties of Si / Al substitution energy, deprotonation energy, bridging hydroxyl stretching vibration frequency and adsorption energy for the probe molecule were calculated and used to measure Brønsted acid location and strength. As the result shows, T2 is the most readily to be replaced by Al and the Brønsted acids prefer to be formed at Al 2– O 7– Si 3 site. Al 2– O 6– Si 2 is the highest in Brønsted acid strength. Besides, the acid strength weakens with the decrease of Si / Al .

Use of pyridine as a probe for the determination, by IR spectroscopy, of the Brønsted acid strength of MIHNaY zeolites

1996 ◽  
Vol 92 (7) ◽  
pp. 1263-1266 ◽  
Author(s):  
Jean-Claude Lavalley ◽  
Rodolphe Anquetil ◽  
Jolanta Czyzniewska ◽  
Maria Ziolek
Keyword(s):  
Ir Spectroscopy ◽  
Acid Strength ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brönsted Acid

Tuning Brønsted Acid Strength by Altering Site Proximity in CHA Framework Zeolites

ACS Catalysis ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 7842-7860 ◽  
Author(s):  
Steven Nystrom ◽  
Alexander Hoffman ◽  
David Hibbitts
Keyword(s):  
Acid Strength ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brönsted Acid

Brønsted acid strength in US-Y: FTIR study of CO adsorption

1994 ◽  
Vol 90 (2) ◽  
pp. 383-386 ◽  
Author(s):  
Marina A. Makarova ◽  
Khalid M. Al-Ghefaili ◽  
John Dwyer
Keyword(s):  
Co Adsorption ◽  
Acid Strength ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Ftir Study ◽  
Brönsted Acid

scholarly journals Operando Dual Beam FTIR Study of Hydroxyl Groups and Zn Species over Defective HZSM-5 Zeolite Supported Zinc Catalysts

Catalysts ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 100 ◽  
Author(s):  
Long Lin ◽  
Xiaotong Zhang ◽  
Ning He ◽  
Jiaxu Liu ◽  
Qin Xin ◽  
...  
Keyword(s):  
Strong Acid ◽  
Acid Sites ◽  
Weak Acid ◽  
Acid Strength ◽  
Bronsted Acid ◽  
Brønsted Acid Sites ◽  
Dual Beam ◽  
Brönsted Acid ◽  
Ft Ir ◽  
Brönsted Acid Sites

A series of defective ZSM-5 zeolites (~300 nm, SiO2/Al2O3 ratio of 55, 100, 480 and 950) were systematically studied by XRD, SEM, 29Si MAS NMR, argon physisorption, NH3-TPD and FT-IR technologies. The nature, the amount and the accessibility of the acid sites of defective ZSM-5 zeolites are greatly different from reported ZSM-5 zeolites with a perfect crystal structure. The Brønsted acid sites (Si(OH)Al) with strong acid strength and the Brønsted acid sites (hydroxyl nests) with weak acid strength co-existed over defective ZSM-5 zeolites, which leads to a unique catalytic function. Zn(C2H5)2 was grafted onto defective ZSM-5 zeolites through the chemical liquid deposition (CLD) method. Interestingly, FT-IR spectroscopic studies found that Zn(C2H5)2 was preferentially grafted on the hydroxyl nests with weak acid strength rather than the Si(OH)Al groups with strong acid strength over different defective ZSM-5 zeolites. In particular, home-built operando dual beam FTIR-MS was applied to study the catalytic performance of Zn species located in different sites of defective ZSM-5 zeolites under real n-hexane transformation conditions. Results show that Zn species grafted over hydroxyl nests obtain better dehydrogenative aromatization performance than Zn species over Si(OH)Al groups. This study provides guidance for the rational design of highly efficient alkane dehydrogenative aromatization catalysts.

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