Incorporation of one or dual Brønsted acidic sites within the mesopores of MCM-41: synthesis and catalytic activity in acetalization reaction

Author(s):  
Mahdiyeh-Sadat Hosseini ◽  
Majid Masteri-Farahani
2010 ◽  
Vol 76 (1) ◽  
pp. 39-49 ◽  
Author(s):  
ZhiQi Jia ◽  
YongXiang Zhao

A novel ‘plugs’-containing Al-SBA-15 material (denoted as PAS) was directly synthesized through simultaneous introducing toluene and aluminum precursor into the reaction mixture of traditional SBA-15. Such material not only featured a unique two-step desorption isotherm as conventional plugged SBA-15 synthesized using excessive siliceous precursor, and higher pore wall thickness than that of other analogous materials, but also possessed weak and medium acidic sites, which implied the PAS would offer unusual advantages such as multifunctionality to process a large variety of feed-stocks in acid-involved reaction (e.g. polymerization of tetrahydrofuran) in industrial point of view. In addition, catalytic activity of the PAS was investigated by the tetrahydrofuran (THF) polymerization reaction in the presence of acetic anhydride and compared with Al-doped MCM-41 prepared via conventional direct hydrothermal synthesis. The PAS exhibited good performance on polymerization of THF. Such result could be related to the large pore size and moderate acidic sites.


2019 ◽  
Vol 9 (3) ◽  
pp. 811-821 ◽  
Author(s):  
Zhao-Meng Wang ◽  
Li-Juan Liu ◽  
Bo Xiang ◽  
Yue Wang ◽  
Ya-Jing Lyu ◽  
...  

The catalytic activity decreases as –(SiO)3Mo(OH)(O) > –(SiO)2Mo(O)2 > –(O)4–MoO.


Author(s):  
Mohsen Nikoorazm ◽  
Maryam Khanmoradi ◽  
Masoumeh Sayadian

Introduction:: MCM-41 was synthesized using the sol-gel method. Then two new transition metal complexes of Nickel (II) and Vanadium (IV), were synthesized by immobilization of adenine (6-aminopurine) into MCM-41 mesoporous. The compounds have been characterized by XRD, TGA, SEM, AAS and FT-IR spectral studies. Using these catalysts provided an efficient and enantioselective procedure for oxidation of sulfides to sulfoxides and oxidative coupling of thiols to their corresponding disulfides using hydrogen peroxide at room temperature. Materials and Methods:: To a solution of sulfide or thiol (1 mmol) and H2O2 (5 mmol), a determined amount of the catalyst was added. The reaction mixture was stirred at room temperature for the specific time under solvent free conditions. The progress of the reaction was monitored by TLC using n-hexane: acetone (8:2). Afterwards, the catalyst was removed from the reaction mixture by centrifugation and, then, washed with dichloromethane in order to give the pure products. Results:: All the products were obtained in excellent yields and short reaction times indicating the high activity of the synthesized catalysts. Besides, the catalysts can be recovered and reused for several runs without significant loss in their catalytic activity. Conclusion:: These catalytic systems furnish the products very quickly with excellent yields and VO-6AP-MCM-41 shows high catalytic activity compared to Ni-6AP-MCM-41.


1996 ◽  
Vol 38 (1-2) ◽  
pp. 33-37 ◽  
Author(s):  
Xiu S. Zhao ◽  
Gao Q. Lu ◽  
Graeme J. Millar ◽  
Xin S. Li

2009 ◽  
Vol 79-82 ◽  
pp. 131-134
Author(s):  
Peng Sun ◽  
Yan Kong ◽  
Jun Du ◽  
Xin Jie Xu ◽  
Jun Wang ◽  
...  

A serious of spherical Co-MCM-41s with different cobalt content was synthesized and characterized by XRD, SEM, N2 isotherms and ICP techniques. The influences of synthesis conditions on the structure were also studied. The use of ascorbic acid as reductant had significant influence on the morphology and the catalytic activity of Co-MCM-41. The prepared samples exhibited higher catalytic activity in the direct hydroxylation of benzene by H2O2 than those with common morphology.


Catalysts ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 829 ◽  
Author(s):  
Zhang ◽  
Yuan ◽  
Miao ◽  
Li ◽  
Shan ◽  
...  

The side-chain alkylation of toluene with methanol was investigated over some Fe-modified Cs ion-exchanged X zeolite (CsX) catalysts prepared via the impregnation method using different iron sources. The absorption/activation behaviors of the reactants on the surface of the catalysts were studied by in situ Fourier-transform infrared (FT-IR) spectroscopy and temperature programmed desorption (TPD) mass measurements. Modification of CsX with a small amount of FeCl3 could result in a considerable decrease in catalytic activity, due mainly to the remarkable decrease in the density of acidic and basic sites of the catalysts. Interestingly, the Fe(NO3)3-modified CsX with an optimum Fe loading of 0.15 wt.% shows improved catalytic activity and high yield compared to the side-chain alkylation products. Modification of CsX with Fe(NO3)3 could also result in a decrease in basic sites of the catalyst. However, such a change does not bring an obvious negative effect on the adsorption/activation of toluene, while it could effectively inhibit the generation of the undesired bidentate formate. Furthermore, the introduced FeOx species (derived from the decomposition of Fe(NO3)3) may also act as new Lewis acidic sites to participate in the activation of methanol and to stabilize the formed active intermediates (i.e., unidentate formate). Therefore, modification of CsX with a suitable amount of Fe(NO3)3 may adjust its adsorption/activation ability for reagents by changing the acid–base properties of the catalyst, which can finally enhance the catalytic performance for the side-chain alkylation of toluene with methanol.


ChemCatChem ◽  
2018 ◽  
Vol 10 (23) ◽  
pp. 5434-5440 ◽  
Author(s):  
Dedong He ◽  
Yaliu Zhang ◽  
Shuang Yang ◽  
Yi Mei ◽  
Yongming Luo
Keyword(s):  

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