More octahedral Cu+ and surface acid sites in uniformly porous Cu-Al2O3 for enhanced Fenton catalytic performances

2021 ◽  
Vol 406 ◽  
pp. 124739
Author(s):  
Lingfei Li ◽  
Chun Hu ◽  
Lili Zhang ◽  
Baoyou Shi
Keyword(s):  
Acid Sites ◽  
Catalytic Performances

scholarly journals Seed-assisted synthesis of TS-1 crystals containing Al with high catalytic performances in cyclohexanone ammoximation

RSC Advances ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 2386-2394 ◽  
Author(s):  
Yan Xue ◽  
Guangling Zuo ◽  
Yiqiang Wen ◽  
Huijuan Wei ◽  
Meng Liu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Acid Sites ◽  
Cyclohexanone Ammoximation ◽  
Catalytic Performances

Using aluminosilicate zeolites seeds, Al atoms are introduced into the TS-1 crystals, resulting in high Lbvalue and more acid sites, which improve the catalytic activity in cyclohexanone ammoximation.

scholarly journals Acid Activated Palygorskite: An Efficient Solid Acid Catalyst for Acetylation Reactions - A Comparative Study

2018 ◽  
Vol 34 (6) ◽  
pp. 3106-3111
Author(s):  
Dhanya Balan A. P ◽  
Pushpaletha P
Keyword(s):  
Solid Acid ◽  
Solid Acid Catalyst ◽  
Secondary Alcohol ◽  
Acid Catalyst ◽  
Acid Sites ◽  
Acid Activation ◽  
Catalytic Activities ◽  
Modification Technique ◽  
Octahedral Cations ◽  
Catalytic Performances

Mild and efficient solid acid catalysts were prepared from natural palygorskite collected from Karnataka and Hyderabad and compared their catalytic activities using the acetylation reaction. Modification technique used for the preparation of the catalysts are acid-activation. During acid-activation exchangeable cations are replaced by H+ ions and a part of octahedral cations are dissolving and thus creating new acid sites in the crystal. The catalytic performances of these catalysts were investigated by using the acetylation reaction. Acetylation reaction was done by using different primary and secondary alcohol. Physicochemical properties were characterized by XRD, SEM, NH3-TPD measurements.

scholarly journals In Situ Synthesis of Sn-Beta Zeolite Nanocrystals for Glucose to Hydroxymethylfurfural (HMF)

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1249
Author(s):  
Kachaporn Saenluang ◽  
Anawat Thivasasith ◽  
Pannida Dugkhuntod ◽  
Peerapol Pornsetmetakul ◽  
Saros Salakhum ◽  
...  
Keyword(s):  
Biomass Conversion ◽  
Hydrothermal Process ◽  
Acid Sites ◽  
Beta Zeolite ◽  
Structure Directing Agent ◽  
Zeolite Type ◽  
Acid Function ◽  
Diquaternary Ammonium ◽  
Catalytic Performances

The Sn substituted Beta nanocrystals have been successfully synthesized by in-situ hydrothermal process with the aid of cyclic diquaternary ammonium (CDM) as the structure-directing agent (SDA). This catalyst exhibits a bifunctional catalytic capability for the conversion of glucose to hydroxymethylfurfural (HMF). The incorporated Sn acting as Lewis acid sites can catalyze the isomerization of glucose to fructose. Subsequently, the Brønsted acid function can convert fructose to HMF via dehydration. The effects of Sn amount, zeolite type, reaction time, reaction temperature, and solvent on the catalytic performances of glucose to HMF, were also investigated in the detail. Interestingly, the conversion of glucose and the HMF yield over 0.4 wt% Sn-Beta zeolite nanocrystals using dioxane/water as a solvent at 120 °C for 24 h are 98.4% and 42.0%, respectively. This example illustrates the benefit of the in-situ synthesized Sn-Beta zeolite nanocrystals in the potential application in the field of biomass conversion.

scholarly journals Modulating Inherent Lewis Acidity at the Intergrowth Interface of Mortise-Tenon Zeolite Catalyst

2021 ◽  
Author(s):  
Huiqiu Wang ◽  
Boyuan Shen ◽  
Xiao Chen ◽  
Hao Xiong ◽  
Hongmei Wang ◽  
...  
Keyword(s):  
Single Crystal ◽  
Lattice Mismatch ◽  
Methanol Conversion ◽  
Scanning Transmission Electron Microscope ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Lewis Acidity ◽  
Light Olefins ◽  
Local Structures ◽  
Catalytic Performances

Abstract The tunability of local structures determines various catalytic performances of zeolite catalysts. The acid sites in zeolite catalysts are important local structures to control the products in methanol conversion. However, it remained still a great challenge to precisely design the acid sites, since there is a lack of controllable methods to generate and identify the acid sites with a high resolution. Here, we use the lattice mismatch of zeolite intergrowth to enrich the inherent Lewis acid sites (LASs) at the interface of a mortise-tenon ZSM-5 catalyst (ZSM-5-MT) showing a 90° intergrowth structure. ZSM-5-MT is formed by two perpendicular blocks that can be atomically resolved by the integrated differential phase contrast scanning transmission electron microscope (iDPC-STEM). It can be revealed by various methods that more framework-associated Al (AlFR) LASs are generated in ZSM-5-MT than single-crystal ZSM-5 catalyst. Combining with the iDPC-STEM results, we demonstrate that the partial missing of O atoms at interfaces results in the formation of inherent LASs in ZSM-5-MT. According to the catalytic performances, LAS-enriched ZSM-5-MT shows a higher selectivity of light olefins than the single-crystal ZSM-5 catalyst in methanol conversion. These results provide an efficient strategy to design the Lewis acidity in zeolites for tailored catalytic functions via interface engineering.

Promoting effect of dual modification of H-ZSM-5 catalyst by alkali treating and Mg doping on catalytic performances for alkylation of benzene with ethanol to ethylbenzene

RSC Advances ◽  
2014 ◽  
Vol 4 (91) ◽  
pp. 50123-50129 ◽  
Author(s):  
Wen Ding ◽  
Yuyang Cui ◽  
Jianjun Li ◽  
Yiquan Yang ◽  
Weiping Fang
Keyword(s):  
Lewis Acid ◽  
Strong Interaction ◽  
Alkali Treatment ◽  
Acid Sites ◽  
Hydroxyl Group ◽  
Lewis Acid Sites ◽  
Promoting Effect ◽  
Mg Doping ◽  
Alkylation Of Benzene ◽  
Catalytic Performances

After partial dealumination and desilicification caused by Mg doping and alkali treatment, Mg substituted hydroxyl group in the structure of HZSM-5. The increase in the number of Lewis acid sites led to a strong interaction of Mg (OH)+ with EFAL.

Catalytic Performances of Silicon Dioxide Supported Titania as Catalyst in Transesterification between Diethyl Oxalate and Phenol

2011 ◽  
Vol 396-398 ◽  
pp. 724-729 ◽  
Author(s):  
Li Bian ◽  
Guang Lin Zhang
Keyword(s):  
Silicon Dioxide ◽  
Amorphous Structure ◽  
Acid Sites ◽  
Diethyl Oxalate ◽  
Impregnation Method ◽  
X Ray Diffraction ◽  
Characterization Methods ◽  
Adsorbed Pyridine ◽  
The Relationship ◽  
Catalytic Performances

A series of silicon dioxide supported titania by the impregnation method for transesterification of diethyl oxalate (DEO) and phenol was carried out under the facile catalytic condition in the liquid phase at 453 k in the atmospheric pressure. Within different TiO2loadings ranging from 1% to 20%, 10% TiO2/SiO2performed best, giving 49.5% conversion of DEO and the total 100% selectivity to ethyl phenyl oxalate (EPO) and diethyl oxalate (DPO). To further study the relationship between catalytic performances and the catalysts structure, several characterization methods, analysis of X-ray diffraction (XRD), Raman spectroscopy measurement and FTIR of adsorbed pyridine studies were utilized. The results of XRD and Raman, showed amorphous structure of TiO2on SiO2below the 10% loading and crystalline form of TiO2phase on SiO2above the 10% loading. In addition, FTIR of adsorbed pyridine studies illuminated the Lewis-type acid sites were responsible for transesterification between DEO and phenol.

One-pot Synthesis of Hierarchical Mesoporous ZSM-5 from the Assembly of Nanocrystals Using Urea as Additive

NANO ◽  
2020 ◽  
Vol 15 (02) ◽  
pp. 2050026
Author(s):  
Yuanyuan Ma ◽  
Zhifang Li ◽  
Nan Zhao ◽  
Fuzhong Han ◽  
Qiubin Kan
Keyword(s):  
Crystalline Phase ◽  
High Surface ◽  
High Surface Area ◽  
Acid Sites ◽  
Butyl Alcohol ◽  
One Pot ◽  
Tert Butyl Alcohol ◽  
Hierarchical Architectures ◽  
Adsorption Desorption ◽  
Catalytic Performances

A hierarchical mesoporous ZSM-5 catalyst with aggregated nanocrystals structure was one-pot hydrothermally synthesized by using urea as the additive. The crystalline phase, morphology and hierarchical architectures were characterized by the XRD, SEM, TEM and N2 adsorption/desorption analyses. The nano-aggregates showed MFI crystalline phase and were composed of connected nanoparticles. The samples had the high surface area and the pore volume from intercrystalline among the nanoparticles due to spontaneously stacking of nanocrystals. The pyridine-adsorbed FTIR and the catalytic performances in the alkylation of phenol and tert-butyl alcohol were applied to evaluate the accessibility of acid sites and the catalytic activities for the hierarchical mesoporous ZSM-5 samples. The samples possessed high accessibility of acid sites which resulted from their large amount of mesopores, and its catalytic activity was improved dramatically. The phenol conversion could reach up to 95.6%, and the corresponding selectivity of 4-TBP and 2,4-DTBP was 44% and 51.5%, respectively.

scholarly journals A Facile Strategy to Prepare Shaped ZSM-5 Catalyst with Enhanced para-Xylene Selectivity and Stability for Toluene Methylation

2017 ◽  
Author(s):  
Yiren Wang ◽  
Yang Chang ◽  
Min Liu ◽  
Anfeng Zhang ◽  
Chunshan Song ◽  
...  
Keyword(s):  
Physical Adsorption ◽  
Catalytic Performance ◽  
Acid Sites ◽  
The Novel ◽  
In Situ Xrd ◽  
Para Xylene ◽  
Toluene Methylation ◽  
Temperature Programmed ◽  
Catalytic Performances

This work describes the catalytic performances of attapulgite/ZSM-5 extrudate in comparison to conventional alumina-bound ZSM-5 extrudate in toluene methylation. The novel attapulgite/ZSM-5 extrudate is prepared by using natural clay attapulgite as binder which introduces mobile alkaline species and macropores to the extrudate. In contrast to alumina-bound extrudate, this novel extrudate shows significantly higher para-selectivity and stability. By using characterization techniques, including in-situ XRD, SEM, NH3 temperature programmed desorption (TPD), thermogravimetric analysis and n-hexane/cyclohexane physical adsorption, the catalytic performance improvement of attapulgite/ZSM-5 extrudate is correlated with the neutralization of Brønsted acid sites by mobile alkaline species during calcination and reaction process. Moreover, a higher para-selectivity was obtained over attapulgite-bound modified ZSM-5 extrudate. The strategy of extruding ZSM-5 catalysts with attapulgite as binder is facile and universal. Such method paves a new way for preparation of shaped toluene methylation catalyst with enhanced para-selectivity and stability.

An analytical microscopic study of metals in fluidized catalytic cracking catalyst

1986 ◽  
Vol 44 ◽  
pp. 854-855
Author(s):  
Clifford S. Rainey
Keyword(s):  
Electron Microscopy ◽  
Spatial Distribution ◽  
Catalytic Cracking ◽  
Catalyst Deactivation ◽  
Coke Formation ◽  
Acid Sites ◽  
Y Zeolite ◽  
Fcc Catalyst ◽  
Fluidized Catalytic Cracking ◽  
High Regeneration

The spatial distribution of V and Ni deposited within fluidized catalytic cracking (FCC) catalyst is studied because these metals contribute to catalyst deactivation. Y zeolite in FCC microspheres are high SiO2 aluminosilicates with molecular-sized channels that contain a mixture of lanthanoids. They must withstand high regeneration temperatures and retain acid sites needed for cracking of hydrocarbons, a process essential for efficient gasoline production. Zeolite in combination with V to form vanadates, or less diffusion in the channels due to coke formation, may deactivate catalyst. Other factors such as metal "skins", microsphere sintering, and attrition may also be involved. SEM of FCC fracture surfaces, AEM of Y zeolite, and electron microscopy of this work are developed to better understand and minimize catalyst deactivation.

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