Trích:
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Nguyên văn bởi aqhl
Gọi substance hay material là được rồi, cái này không phải molecule đâu.
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hổng phải đâu, cũng là molecule thôi, nó thuộc về molecular sieve family.
To Pluie, cái này cũng dùng như support thôi, tui không hiểu ý bạn lắm. Thêm một chút về MCM-41 nè, thông cảm vì không có thời gian dịch ra nhé,
The recently discovered mesoporous molecular sieve MCM-41 [1] has attracted considerable interest from researchers in the fields of materials science, catalysis, adsorption and other relevant areas.
This new member of the molecular sieve family shows a regular hexagonal array of uniform pores with pore opening dimensions between 1.5 and 10 nm. As a consequence of their high thermal stability, high BET surface areas and large pore volumes, these materials could be considered to be excellent supports for metals in catalytic systems.
In addition, some papers dealing with the possibility of modifying the hydroxyl-rich surfaces by grafting alkoxides have been published recently , the surface coverage degree can be tuned by controlling the amount of metal alkoxide. Dispersing metal oxides, such as Al2O3 or ZrO2, onto the inner pore surfaces can greatly improve the thermal stability
As well as grafting or dispersing metals on the surface of mesoporous molecular sieves, metals can also be incorporated in the framework of the MCM-41. Aluminum can be introduced in the structure of these materials generating a change in charge distribution that will be compensated by different cations. In this way, new families (aluminosilicates, titanosilicates, germanosilicates, ferrisilicates, etc.) are obtained by the incorporation or substitution of cations in the structure, rendering these systems very interesting due to the presence of new active centers with redox properties or different acid strengths. The introduction of carefully selected metal ions can help tune catalyst activities and selectivities.
Therefore, mesoporous silica MCM-41 molecular sieves containing Zn and Al ions ([Zn]-MCM-41 and [Al]-MCM-41) were found to be effective in the alkylation of alkyl aromatics . Chen and Lu reported high catalytic activity for mesoporous vanadosilicate ([V]-MCM-41) in the oxidation of benzene. A MCM-41-supported palladium catalyst was used for aromatic hydrogenation , and liquid-phase hydrogenation. Additionally, Long and Yang, reported that Cu2+-, Rh2+- and Fe3+-exchanged [Al]-MCM-41 are effective catalysts for the selective catalytic reduction of nitric oxide with ethylene, propylene and NH3, respectively. The same authors were the first to report the use of Pt-supported MCM-41 mesoporous sieves for the selective catalytic reduction of NO by hydrocarbons in the presence of oxygen. High activity for NO reduction was obtained when C2H4 or C3H6 were used as the reductants. The Pt/MCM-41 catalysts displayed good stability with respect to resistance to H2O and SO2. This property has been noted previously in the NO reduction reaction with hydrocarbons.