Synthesis, Characterization And Properties Of New Functional Mesoporous Materials

The conventional zeolite moleculars sieves have strong acidity and unique crystal structures. However, the pore sizes of these zeolite materials are normally less than 2 nm, consequently restricting their potential applications for acid-catalyzed processes, such as petroleum refining, fine chemicals synthesis, etc. The introduction of mesoporous molecular sieves with MCM-41 and SBA-15 structures has developed new possibilities for adsorption and catalytic reactions of large molecules. These novelty nano-materials were firstly reported in 1990s, with large and tunable pore diameters, large BET surface areas and uniform porosity. Based on such excellent properties, they have shown superior catalytic performance than those conventional zeolite moleculars sieves.since 1992, the mesoporous materials were first systhesised, the attempt of supporting high catalytic materials into the pores or the framework of the mesoporous materials has not suspended. Some worldwide famous professors are all pay attentain to this field. It is well known that the heteropolyacid (HPA) with Keggin structure especially 12-tungstophosphoric acid (HPW) have been widely applied in catalysis due to its strong acidity, facile preparation and acceptable stability. However, the catalytic activities of the HPA are greatly limited due to their very low specific surface areas. Therefore, some researchers have carried on the investigation of HPA supported on the mesoporous materials. Nevertheless, the success is limited for their widely use owing to: (1) some pore are blocked by heteropolyacid clusters and the surface area of the modified mesoporous materials is reduced significantly; (2) leaching of heteropolyacids from modified samples into polar solvents leads to the decrease of catalytic activities and inability for recycle in liquid phase reactions. So,the encapsulation of heteropoly compounds of Keggin structure into the pores of a molecular sieve may provide an active, stable catalyst. However, the anchoring of HPA into walls of mesoporous occurs by means of the interaction of the HPA acidic protons with the silanol groups and results in the formation of only very weak bonds between HPA and walls. As a consequence, leaching of heteropoly acid was always observed when the HPA/mesoporous silica system was applied in polar solvent media.In the following study we utilised modification of the silica gel surface with aminoalkoxysilanes in order to incorporate functional groups inside the channels of the mesoporous molecular sieve which would be able to react with heteropoly acid and form strong bonds. Aminosilane molecules, initially connected to the silica surface via the amine groups, turn to display an amineupward position It seems probable that the exposed basic amine groups might react with heteropoly acids to form the salt will be linked strongly to the modified surface. This causes a strong enough immobilization of HPW at the solid surface to prevent its leaching in polar reactant solutions while retaining its high acidity and catalytic activity in different catalytic reactions. It follow from this that HPW-SBA-NH is more stable than HPW-SBA-15 in the reaction system involving polar solvent. catalyst can be readily separated from the reaction system for reuse, which suggests the potential industrial application.On the other hand, porous carbon materials have attracted much attention due to their many important applications, for example, as adsorbents, catalyst supports, and electrode materials. More recently, a new class of carbon molecular sieves was synthesized using mesostructured silica (or aluminosilicate) materials as inorganic templates. To date, cubic, disordered, hexagonal, foamlike and nanopipe type mesostructured carbon materials have been synthesized. Some of these carbon materials have been successfully used as electrodes for electric double-layer capacitors and fuel cells. Moreover, their good pore connectivity and large pore size (2-30 nm) make these mesoporous carbons attractive catalyst supports. The general synthetic process is as follows: (1) preparation of a mesostructured silica/ surfactant nanocomposite, which often takes 2-3 days;(2) the removal of the surfactant by calcination or solvent extraction; (3) the generation of catalytic sites inside the wall of the mesostructured silica for subsequent polymerization (in some synthesis); (4) incorporation of polymer precursor, such as phenol, furfuryl alcohol, or sucrose into the pores of the mesoporous silica material; (5) polymerization to obtain a carbon precursor; (6) carbonization; and finally, (7) the removal of the silica template using HF or NaOH solution. This long and complicated multistep template synthetic procedure hampers the broad application of these mesostructured carbons, despite their many important characteristics, and a short and simple synthetic procedure is required if such materials are to achieve widespread use. An order mesoporous carbon molecular sieve was directly manufactured through the carbonization of P123/TMB/FA/TEOS composites followed by silica removed. P123, TMB and FA (furfuryl alcohol) was using as the structure-directing agent, swelling agent and carbon precursors. The mesoporous carbon sieve was verified to perform a large-scale highly ordered 2D hexagonal array of mesopores structure, similar to those typically 2D hexagonal mesoporous silica materials, such as SBA-15, by employing Powder X-ray diffraction (XRD) patterns, nitrogen adsorption/desorption measurement and transmission electron microscopy (TEM).