p- Xylene selectivity enhancement in methanol toluene alkylation by separation of catalysis function and shape-selective function

2017 ◽  
Vol 433 ◽  
pp. 242-249 ◽  
Author(s):  
Chuanfu Wang ◽  
Qi Zhang ◽  
Yufei Zhu ◽  
Dongke Zhang ◽  
Jingyun Chen ◽  
...  
Keyword(s):  
Toluene Alkylation ◽  
Shape Selective

scholarly journals Maximizing sinusoidal channels of HZSM-5 for high shape-selectivity to p-xylene

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Chuanfu Wang ◽  
Lei Zhang ◽  
Xin Huang ◽  
Yufei Zhu ◽  
Gang (Kevin) Li ◽  
...  
Keyword(s):  
High Activity ◽  
Chemical Industry ◽  
Chemical Separation ◽  
Shape Selectivity ◽  
Toluene Alkylation ◽  
Shape Selective ◽  
Toluene Methylation ◽  
Selective Catalysis ◽  
The Cost ◽  
Very High

Abstract The shape-selective catalysis enabled by zeolite micropore’s molecular-sized sieving is an efficient way to reduce the cost of chemical separation in the chemical industry. Although well studied since its discovery, HZSM-5′s shape-selective capability has never been fully exploited due to the co-existence of its different-sized straight channels and sinusoidal channels, which makes the shape-selective p-xylene production from toluene alkylation with the least m-xylene and o-xylene continue to be one of the few industrial challenges in the chemical industry. Rather than modifications which promote zeolite shape-selectivity at the cost of stability and reactivity loss, here inverse Al zoned HZSM-5 with sinusoidal channels predominantly opened to their external surfaces is constructed to maximize the shape-selectivity of HZSM-5 sinusoidal channels and reach > 99 % p-xylene selectivity, while keeping a very high activity and good stability ( > 220 h) in toluene methylation reactions. The strategy shows good prospects for shape-selective control of molecules with tiny differences in size.

Fabrication of a core–shell MFI@TON material and its enhanced catalytic performance for toluene alkylation

2020 ◽  
Vol 10 (5) ◽  
pp. 1281-1291 ◽  
Author(s):  
Suyao Liu ◽  
Huaike Zhang ◽  
Huimin Chen ◽  
Zhiqiang Chen ◽  
Liwei Zhang ◽  
...  
Keyword(s):  
Catalytic Performance ◽  
Acid Sites ◽  
Core Shell ◽  
Diffusion Behavior ◽  
Selective Catalyst ◽  
Toluene Alkylation ◽  
Shape Selective

Core–shell MFI@TON composites were designed and synthesized as a highly shape-selective catalyst for toluene alkylation by passivating the nonselective acid sites and tuning the diffusion behavior.

Structure and Shape-Selective Properties of MFI Type Ferrisilicates. A Comparison with Aluminosilicate Analogues

1992 ◽  
Vol 57 (4) ◽  
pp. 799-808 ◽  
Author(s):  
Blanka Wichterlová ◽  
Gert Vorbeck ◽  
Rolf Fricke ◽  
J. Richter-Mendau ◽  
Jiří Čejka
Keyword(s):  
Outer Surface ◽  
Crystal Size ◽  
Point Of View ◽  
Toluene Disproportionation ◽  
Fe Species ◽  
Toluene Alkylation ◽  
Ammonia Desorption ◽  
Shape Selective ◽  
Toluene Conversion ◽  
Zeolite Crystals

A comparison of H-forms of Fe- and Al-substituted silicates of MFI structure and of a comparable crystal size is given from the point of view of the acidity of SiOHMe groups, activity as well as para-selectivity in toluene disproportionation and toluene alkylation with ethylene. It has been found that SiOHFe groups exhibit weaker acidity than SiOHAl groups which is reflected in ammonia desorption at lower temperatures and lower toluene conversion for ferrisilicates. The ferrisilicates exhibit lower para-selectivity compared to aluminosilicates; moreover, higher coking is observed. While the aluminosilicates contain mostly aluminum in the framework sites forming SiOHAl groups, the ferrisilicates contain, beside Fe linked in SiOHFe groups, also tricoordinated Fe3+ cations or even extraframework Fe species. The latter two species can be responsible for a considerably higher coking of ferrisilicates compared to aluminosilicates. Simultaneously, such Fe species can contribute to observed lower para-selectivity of ferrisilicates in comparison with aluminosilicates, when they are located on the outer surface of zeolite crystals.

Shape-Selective Alkylation of Toluene with Methanol over Modified Nano-scale HZSM-5 Zeolite

2014 ◽  
Vol 32 (7) ◽  
pp. 1280-1286 ◽  
Author(s):  
Zhiping ZHANG ◽  
Yan ZHAO ◽  
Hongyu WU ◽  
Wei TAN ◽  
Xiangsheng WANG ◽  
...  
Keyword(s):  
Nano Scale ◽  
Shape Selective ◽  
Selective Alkylation

The Effect of Acidity of Al and Fe Silicates with MFI Structure on Benzene and Toluene Alkylation with Isopropyl Alcohol

1996 ◽  
Vol 61 (8) ◽  
pp. 1115-1130 ◽  
Author(s):  
Jiří Čejka ◽  
Naděžda Žilková ◽  
Blanka Wichterlová
Keyword(s):  
Kinetic Study ◽  
Molecular Sieves ◽  
Isopropyl Alcohol ◽  
Acid Sites ◽  
Transport Rate ◽  
Reaction Products ◽  
Oh Groups ◽  
Benzene Alkylation ◽  
Toluene Alkylation ◽  
Low Strength

Kinetic study of toluene and benzene alkylation with isopropyl alcohol on alumo- and ferrisilicates of MFI structure has shown that the alkylation activity does not follow the acidity (both the number and strength of bridging OH groups) of these molecular sieves. The rate of the overall reaction is controlled by the desorption/transport rate of bulky, strongly adsorbed cymenes and cumene. A higher concentration of n-propyltoluenes compared to n-propylbenzene, both undesired reaction products, formed via a bimolecular isomerization of isopropyl aromate with benzene or toluene, was due to the higher reactivity of isopropyltoluene with toluene in comparison with that of cumene with benzene. It is concluded that ferrisilicates of MFI structure possessing low strength acid sites appear to be promising catalysts for achieving both a high isopropyl- and para-selectivity in toluene alkylation to p-cymene.

Zeolates: A Coordination Chemistry View of Metal-Ligand Bonding in Intrazeolite MOCVD Type Precursors and Semiconductor Nanoclusters

1992 ◽  
Vol 277 ◽  
Author(s):  
Geoffrey A. Ozin ◽  
Carol L. Bowes ◽  
Mark R. Steele
Keyword(s):  
Self Assembly ◽  
Materials Science ◽  
Zeolite Y ◽  
Chemical Vapour ◽  
Internal Surface ◽  
Building Blocks ◽  
Structural Features ◽  
Organic Chemical ◽  
Wide Range ◽  
Shape Selective

ABSTRACTVarious MOCVD (metal-organic chemical vapour deposition) type precursors and their self-assembled semiconductor nanocluster products [1] have been investigated in zeolite Y hosts. From analysis of in situ observations (FTIR, UV-vis reflectance, Mössbauer, MAS-NMR) of the reaction sequences and structural features of the precursors and products (EXAFS and Rietveld refinement of powder XRD data) the zeolite is viewed as providing a macrospheroidal, multidendate coordination environment towards encapsulated guests. By thinking about the α- and β-cages of the zeolite Y host effectively as a zeolate ligand composed of interconnected aluminosilicate “crown ether-like” building blocks, the materials chemist is able to better understand and exploit the reactivity and coordination properties of the zeolite internal surface for the anchoring and self-assembly of a wide range of encapsulated guests. This approach helps with the design of synthetic strategies for creating novel guest-host inclusion compounds having possible applications in areas of materials science such as nonlinear optics, quantum electronics, and size/shape selective catalysis.

scholarly journals Shape-selective n-alkane hydroconversion at exterior zeolite surfaces

2008 ◽  
Vol 256 (1) ◽  
pp. 95-107 ◽  
Author(s):  
T MAESEN ◽  
R KRISHNA ◽  
J VANBATEN ◽  
B SMIT ◽  
S CALERO ◽  
...  
Keyword(s):  
Shape Selective
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