The Introduction of MCM-48

MCM-48 is a Mobil Composition of Matter No.48 of abbreviations, transliteration is the No. 48 Mobil synthetics. It is Mobil (Mobil) Chemical developed a mesoporous molecular sieve, is the world’s most studied one of mesoporous materials.Mesoporous molecular sieves of MCM-48 type were prepared by conventional hydrothermal and novel room temperature syntheses. Scanning electron microscopy (SEM) studies have shown that nonagglomerated uniform spheres of size ca. 0.5 μm were obtained by the room temperature method. Internal pore structure was studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution nitrogen and argon adsorption. Pore size distributions were calculated from low-temperature nitrogen and argon adsorption isotherms by the nonlocal density functional theory (NLDFT) method. A novel approach to calculating the pore wall thickness of MCM-48 from XRD and gas adsorption isotherms was employed. The approach utilizes intrinsic symmetry of MCM-48 pore structure, cubic Ia3d space group, revealed by XRD and combines the results of the pore size distribution analysis with general geometrical relations between structural parameters of the gyroid minimal surface. The pore wall thickness of MCM-48 calculated from both nitrogen and argon adsorption data was found to be ca. 8−10 Å, in good agreement with the estimates obtained from TEM.

MCM-48 are often directly use abbreviations. M41S series of mesoporous molecular sieves with 2 ~ 10nm around the regular channel, about 1000cm ~ 2 / g of high surface area and easy introduction of hetero-atom amorphous pore walls and other unique advantages, is widely used in macromolecular catalysis, separation and life sciences environmental protection and other hot areas. One cubic phase MCM-48 has two sets of mutually connected three-dimensional cross-channel, can significantly enhance the mass transfer process and ease the reaction catalyst coking, and some shape-selective macromolecular reaction effect. Therefore, this choice of MCM-48 as a synthetic target, mainly on the Si-MCM-48 and Si-MCM-48 membrane synthesis conditions, ie use template, silicon source, base sources, crystallization time and crystallization temperature on the impact of product structure, and on this basis, the optimum conditions used in pure silicon system, the introduction of different sources of aluminum and titanium source precursor was prepared by heteroatom mesoporous Al-MCM-48, Ti-MCM-48, mainly characterized by XRD, SEM and UV-Vis products examined were characterized by means of the phase structure, surface morphology and the heteroatom in the zeolite framework in the distribution. Heteroatom in the preparation of mesoporous molecular sieve process, focused on the synthesis of the alkalinity of the mother liquor from the phase structure of the product, and found that the introduction of different aluminum source precursors, the synthetic mother liquor by precise modulation of alkalinity, sodium aluminum system increases with the alkalinity in order to be lamellar phase MCM-50, cubic MCM-48 and MCM-41 hexagonal structure of different products, and aluminum sulfate and aluminum isopropoxide in the system increases with the alkalinity of the product the order in contrast, the mother liquor by controlling the alkalinity of a silica-alumina ratio of 20 to get the Al-MCM-48 product. With isopropyl alcohol solution of titanium tetrachloride as the titanium source precursor prepared Ti-MCM-48, we found a similar phase transition rules, and silicon-titanium ratio decreases with the mother liquor alkalinity control tend to weaken the impact of product structure, This shows that the system introduced in the synthesis of organic alcohol weakened the alkalinity of the product structure, control, and n-butanol after the introduction of this effect is more obvious. Mother liquor alkalinity is also available through the control of titanium silicon ratio of 50 Ti-MCM-48 product. Last examined the synthesis of Al-MCM-48 in the alkylation of benzene with propylene, cumene transalkylation and cracking two acid-catalyzed reactions such as catalytic properties, with the styrene oxidation reaction as a probe to study the Ti -MCM-48 catalytic oxidation performance. The results show that high heteroatom content of MCM-48 were introduced in the acid and redox center has good catalytic activity, but also help generate a larger macromolecular product or a product of the transition state.

  

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