Seitaro Namba

Aluminum incorporation in mesoporous MCM-41 molecular sieves and their catalytic performance in acid-catalyzed reactions

Abstract Mesoporous aluminosilicate molecular sieves, Al-containing MCM-41, with different Si/Al ratios were synthesized by four different methods: sol–gel, hydrothermal, template cation exchange and grafting. The catalysts prepared by sol–gel, grafting and template cation exchange methods are effective for the incorporation of large amounts of aluminum into the framework of MCM-41. The catalytic activities of the resulting Al-containing MCM-41 samples were tested in the cracking of cumene and the dehydration of 2-propanol, as model acid-catalyzed reactions, and then compared with the results obtained from microporous H-ZSM-5 and HY zeolites. The Al-containing MCM-41 catalysts prepared by different methods behaved differently in acting as acidic catalysts; the catalyst (having almost same Si/Al ratio) prepared by sol–gel method showed higher cracking activity, whereas that prepared by template cation exchange method showed higher dehydration activity. Moreover, these Al-containing MCM-41 catalysts are more catalytically active than microporous HY zeolite for cumene cracking and 2-propanol dehydration reactions.

Progress in Pore-Size Control of Mesoporous MCM-41 Molecular Sieve Using Surfactant Having Different Alkyl Chain Lengths and Various Organic Auxiliary Chemicals

Pore-size control of mesoporous silica MCM-41 molecular sieve is described on the basis of the use of surfactant having different alkyl chain lengths and various organic auxiliary chemicals during the hydrothermal synthesis process. The BJH pore diameter of MCM-41 can be tuned from 1.6 to 4.2 nm using single or mixture of two surfactant(s) with alkyl chain lengths varied from C8 to C22. By the addition of different organic auxiliary chemicals: 1,3,5-trimethylbenzene, isopropylbenzene or tridecane into the synthesis medium, the BJH pore size of MCM-41 can be tailored up to 12.0 nm.

Synthesis and characterization of rhodium oxide nanoparticles in mesoporous MCM-41

Rhodium-containing MCM-41 mesoporous molecular sieves (Rh-MCM-41) were synthesized by adding RhCl3·3H2O to a mixed silicate–surfactant gel prior to hydrothermal synthesis. The obtained Rh-MCM-41 samples were characterized by XRD, N2 adsorption, TEM, 29Si solid-state NMR and XPS. It was found that rhodium oxide nanoparticles <3 nm were located in the MCM-41 mesopore channels or 6 nm rhodium oxide particles were dispersed in the MCM-41 matrices, depending on the hydrothermal synthesis temperature and the aging conditions. The unit cell and pore wall thickness of Rh-MCM-41 synthesized at 423 K were 5.71 and 2.31 nm, respectively, which were larger than those of the corresponding pure Si-MCM-41. The increase in the pore wall thickness may be due to enhancement of cross-linking of â–·Si–OH in the silicate gel by the presence of Rh ions.

MCM-41 as a highly active catalyst for Diels–Alder reaction of anthracene with p-benzoquinone

The Diels–Alder reaction of anthracene with p-benzoquinone on three types of aluminosilicate MCM-41 (Al-MCM-41) was studied. It is found that the catalytic activity of every Al-MCM-41 is very high. This activity is almost the same as that of AlCl3 and higher than that of HY zeolite, silica–alumina, and a cation exchange resin. We also found that the main active sites on Al-MCM-41 are Lewis acid sites. The selectivity of Al-MCM-41 to the single-adduct is much higher than that of AlCl3, because Al-MCM-41 has much less catalytic activity for the consecutive reaction of the single-adduct to form the double-adduct, compared with AlCl3.

Hydrodesulfurization over noble metals supported on mesoporous silicate MCM-41

Abstarct The Pt/MCM-41 catalyst showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 350 °C and this activity was higher than that of commercial CoMo/Al 2 O 3 catalyst The Pt/MCM-41 catalyst has high sulfur-tolerant property toward hydrogen sulfide formed in hydrodesulfurization of thiophene. The silanol group (Si-OH) of MCM-41 and the spillover hydrogen formed on Pt particle in Pt/MCM-41 catalyst play important roles for the hydrodesulfurization of thiophene.

Nanosized rhodium oxide particles in the MCM-41 mesoporous molecular sieve

Nanosized rhodium oxide-containing MCM-41 (Rh-MCM-41) mesoporous molecular sieves are synthesized and characterized by XRD, TEM, N2 adsorption, NMR, XPS and EXAFS.

Low-temperature PROX (preferential oxidation) on novel CeO2-supported Cu-cluster catalysts under fuel-cell operating conditions

Cu(1+)-clusters on a CeO(2) support, which were prepared by hydrothermal synthesis using cetyltrimethylammonium bromide (CTAB), were found to be highly active and selective for preferential oxidation (PROX) of CO in excess H(2) with H(2)O and CO(2) under practical fuel-cell operating conditions.

Catalytic performance of mesoporous silica SBA-15-supported noble metals for thiophene hydrodesulfurization

The Pt/AlSBA-15 catalyst showed high and stable catalytic activity for the hydrodesulfurization of thiophene at 350°C and this activity was higher than those of Pt/SBA-15 and commercial CoMo/Al2O3 catalysts. The Pt/AlSBA-15 catalyst has high sulfur-tolerant property toward hydrogen sulfide formed in hydrodesulfurization of thiophene. The Broensted acid sites of AlSBA-15 and the spillover hydrogen formed on Pt particle in Pt/AlSBA-15 catalyst play an important roles for the hydrodesulfurization of thiophene.

26-P-07-Hydrodesulfurization of benzothiophene over noble metals supported on mesoporous silica MCM-41

Publisher Summary This chapter discusses the hydrodesulfurization of benzothiophene over noble metals supported on mesoporous silica MCM-41. The Pt/MCM-41 catalyst shows high and stable catalytic activity for the hydrodesulfurization of benzothiophene at 350°C, and this activity is higher than that of commercial cobalt molybdenum/ alumina (CoMo/A1 2 O 3 ) catalyst. The Pt/MCM-41 catalyst has high sulfur-tolerant property toward hydrogen sulfide formed in the hydrodesulfurization of benzothiophene. The silanol group (Si–OH) of MCM-41 and the spillover hydrogen formed on platinum (Pt) particle in Pt/MCM-41 catalyst play important roles in the hydrodesulfurization of benzothiophene. Pt/MCM-41 might be a promising new hydrodesulfurization catalyst for bulky organic sulfur compounds in the petroleum feedstocks.

18-P-12 - Pressure swing adsorption of ethyl acetate on silica MCM-41

Publisher Summary This chapter describes pressure swing adsorption (PSA) of ethyl acetate on silica MCM-41. Fundamental studies on the removal or recovery of ethyl acetate vapor from industrial waste effluent gas by PSA on silica MCM-41 are made. From the effects of pretreatment temperatures and trimethylsilylation, it is found that ethyl acetate molecules are irreversibly adsorbed on surface hydroxyl (OH) groups on silica MCM-41 through hydrogen bonding at a low adsorption or desorption temperature of 303 K. With increasing adsorption temperature from 303 to 373 K, the amount of irreversible adsorption decreases to almost nil. Therefore, a combination of PSA and temperature swing adsorption operation is desirable for the removal or recovery of ethyl acetate vapor. The reversible adsorption capacity becomes 250 mg g-1 by the combination.