Regulating the acid sites and framework aluminum siting in MCM–22 zeolite to enhance its performance in alkylation of benzene with methanol

2022 ◽  
pp. 111677
Author(s):  
Yilin Wang ◽  
Shufang Xu ◽  
Xuan He ◽  
Fan Yang ◽  
Xuedong Zhu
Keyword(s):  
Acid Sites ◽  
Alkylation Of Benzene

scholarly journals Controlled direct synthesis of single- to multiple-layer MWW zeolite

2020 ◽  
Author(s):  
Jie-Qiong Chen ◽  
Yu-Zhao Li ◽  
Qing-Qing Hao ◽  
Huiyong Chen ◽  
Zhao-Tie Liu ◽  
...  
Keyword(s):  
Large Scale ◽  
Direct Synthesis ◽  
Single Layer ◽  
Strong Acid ◽  
Acid Sites ◽  
Synthesis Conditions ◽  
Alkylation Of Benzene ◽  
Controlled Structure ◽  
Strong Acid Sites ◽  
Mww Zeolite

ABSTRACT The minimized diffusion limitation and completely exposed strong acid sites of the ultrathin zeolites make it an industrially important catalyst especially for converting bulky molecules. However, the structure-controlled and large-scale synthesis of the material is still a challenge. In this work, the direct synthesis of the single-layer MWW zeolite was demonstrated by using hexamethyleneimine and amphiphilic organosilane as structure-directing agents. Characterization results confirmed the formation of the single-layer MWW zeolite with high crystallinity and excellent thermal/hydrothermal stability. The formation mechanism was rigorously revealed as the balanced rates between the nucleation/growth of the MWW nanocrystals and the incorporation of the organosilane into the MWW unit cell, which is further supported by the formation of MWW nanosheets with tunable thickness via simply changing synthesis conditions. The commercially available reagents, well-controlled structure and the high catalytic stability for the alkylation of benzene with 1-dodecene make it an industrially important catalyst.

Synthesis, Physicochemical Properties and Catalytic Performance of a Modified ZSM-5 Molecular Sieve

2011 ◽  
Vol 197-198 ◽  
pp. 1042-1046
Author(s):  
Wei Qiao Liu ◽  
Gong Li ◽  
Hui Juan Tong ◽  
Wei Ning Lei ◽  
Tong Ming Shang ◽  
...  
Keyword(s):  
Molecular Sieve ◽  
Catalytic Performance ◽  
Mesoporous Molecular Sieve ◽  
Acid Sites ◽  
X Ray Diffraction ◽  
Alkyl Benzene ◽  
Carbon Template ◽  
Conventional Process ◽  
Alkylation Of Benzene ◽  
Adsorption Desorption

A modified ZSM-5 molecular sieve was prepared by the combination of recrystallization and carbon template methods. The samples were characterized by X-ray diffraction, N2 adsorption-desorption, NH3-TPD, TEM and SEM. The results show that the modified ZSM-5 molecular sieve has double pore distribution. The diameters of the two kinds of channels are 0.51~0.56 nm and 1.4~1.6 nm, respectively. In addition, the modified HZSM-5 (H-type ZSM-5) sample mainly has moderate strength of acid sites. Finally, the alkylation of benzene with 1-dodecene olefin was used to evaluate the catalytic performance of the as-synthesized modified ZSM-5 on macromolecules. The conversions of 1-dodecene on the modified ZSM-5, ZSM-5 prepared by conventional process and aluminum-containing SBA-15 mesoporous molecular sieve are 96%, 39% and 83%, respectively. And the selectivities of long chain alkyl benzene on those are 97%, 68% and 91%, respectively. The catalytic properties of the modified ZSM-5 on macromolecules are superior to those of ZSM-5 prepared by conventional process and aluminum-containing SBA-15 mesoporous molecular sieve.

scholarly journals Achieving acid sites accessibility and pore compatibility in MWW nanosheets for alkylation of benzene with 1-dodecene

2021 ◽  
Author(s):  
Baoyu Liu ◽  
Zhantu Liao ◽  
Jianwen Zhang ◽  
Yeqing Huang
Keyword(s):  
Shape Selectivity ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Alkylation Of Benzene ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

Regularly spaced MWW nanosheets combined with single-unit-cell thickness and optimized Al species distribution are highly effective for the alkylation between benzene with 1-dodecene, high conversion of 1-dodecene (ca. 85 %) and selectivity of 2-LAB (ca. 80 %) can be obtained. Detailed studies of this MWW nanaosheets system reveal that ultra-thin MWW nanosheets with ordered arrangement can expose more accessible Brønsted acid sites (ca. ~89 %), and specially place framework Al species on the T2 sites (ca. ~13 %), in which the alkylation mainly occurred under the catalysis of accessible Brønsted acid sites. Besides, the desired 2-LAB is produced on the unique 12-MR hemicavities with solid binding energy and perfect steric configuration. As a proof-of-concept study, we integrate the highly exposed Brønsted acid sites and unrivalled shape-selectivity in the regularly spaced MWW nanosheets system with well characterized acid sites accessibility and pore adaptability, leading to the excellent catalytic performance.

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.

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.

Probe Reactions Catalyzed by Surface Acid Sites of HTS-1

2010 ◽  
Vol 31 (1) ◽  
pp. 72-77
Author(s):  
Xuanyan LIU ◽  
Dulin YIN ◽  
Huayuan ZHU ◽  
Gang SHEN
Keyword(s):  
Acid Sites

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.

scholarly journals The C-terminal domain of feline and bovine SAMHD1 proteins has a crucial role in lentiviral restriction

2020 ◽  
Vol 295 (13) ◽  
pp. 4252-4264 ◽  
Author(s):  
Chu Wang ◽  
Kaikai Zhang ◽  
Lina Meng ◽  
Xin Zhang ◽  
Yanan Song ◽  
...  
Keyword(s):  
Proteasomal Degradation ◽  
Acid Sites ◽  
Accessory Protein ◽  
Restriction Profile ◽  
Biological Functions ◽  
Terminal Domain ◽  
Functional Regions ◽  
Viral Restriction ◽  
Primate Lentiviruses

SAM and HD domain-containing protein 1 (SAMHD1) is a host factor that restricts reverse transcription of lentiviruses such as HIV in myeloid cells and resting T cells through its dNTP triphosphohydrolase (dNTPase) activity. Lentiviruses counteract this restriction by expressing the accessory protein Vpx or Vpr, which targets SAMHD1 for proteasomal degradation. SAMHD1 is conserved among mammals, and the feline and bovine SAMHD1 proteins (fSAM and bSAM) restrict lentiviruses by reducing cellular dNTP concentrations. However, the functional regions of fSAM and bSAM that are required for their biological functions are not well-characterized. Here, to establish alternative models to investigate SAMHD1 in vivo, we studied the restriction profile of fSAM and bSAM against different primate lentiviruses. We found that both fSAM and bSAM strongly restrict primate lentiviruses and that Vpx induces the proteasomal degradation of both fSAM and bSAM. Further investigation identified one and five amino acid sites in the C-terminal domain (CTD) of fSAM and bSAM, respectively, that are required for Vpx-mediated degradation. We also found that the CTD of bSAM is directly involved in mediating bSAM's antiviral activity by regulating dNTPase activity, whereas the CTD of fSAM is not. Our results suggest that the CTDs of fSAM and bSAM have important roles in their antiviral functions. These findings advance our understanding of the mechanism of fSAM- and bSAM-mediated viral restriction and might inform strategies for improving HIV animal models.

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