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Novel Synthesis Of Ordered Mesoporous Carbon Molecular Sieves

Posted on:2005-12-30Degree:MasterType:Thesis
Country:ChinaCandidate:Q LiFull Text:PDF
GTID:2121360125964593Subject:Chemical processes
Abstract/Summary:PDF Full Text Request
Ordered mesoporous carbon molecular sieves (OMCMs) have remarkableproperties, such as the uniformity of pore structure and pore size, high specific surfaceareas and pore volume, chemical inertness, good hydrothermal and mechanicalstability, etc., and have potential use as advanced adsorbents, catalytic supports,double-layer super capacitors and so on. Since the first OMCM, CMK-1, was reportedin 1999 using ordered mesostrcture silica MCM-48 as template, these novel materialshave attracted much attention all over the world. However, research on thepreparation of OMCMs is rare in China. In this thesis, two new preparation methodsfor the synthesis of ordered mesoporous carbon molecular sieves were explored byusing MCM-48 or as-synthesized MCM-48 as template. Resorcinol-formaldehyde(RF) and furfuryl alcohol were employed as carbon precursors. MCM-48 has three-dimensional (Ia3d) channel structure and is alwayssynthesized by hydrothermal and room temperature method. However, the synthesisconditions are always harsh. First, the synthesis of MCM-48 by above methods wasappreciated with respect to their Bragg-diffraction of X-ray (XRD) long-range orderand the results showed that MCM-48 synthesized by hydrothermal method had betterresults. Therefore, hydrothermal method for the synthesis of MCM-48 was chose. Atthe same time, the influence of some factors about the order of the products wasexamined. Then, OMCMs were prepared by first introducing an acid catalyst on calcinedMCM-48 template, followed by impregnating the template in furfuryl alcohol. Theresults were compared with the products prepared by chemical vapor deposition(CVD) method reported in literatures, which used the same template and carbonprecursor. XRD results showed that the mesoporous carbons prepared byimpregnation method had more uniform pore structure than those prepared by CVDmethod, while the former strategy is simpler than the latter. Low temperature N2adsorption tests indicated that the ordered carbon by impregnation method had a BETspecific surface area of 1514 m2/g and a pore volume of 0.964 m3/g. The transmissionelectron microscopy (TEM) results showed that the structure of the OMCMs wasdouble periodic structures and the period was 5.2 nm. Finally, a simple method for the synthesis of OMCMs using as-synthesizedMCM-48 and resorcinol-formaldehyde (RF) was researched. In contrast, calcinedMCM-48 was commonly used in previous reports. The influence of R/MCM-48 ratio,R/water ratio, carbonization temperature, and temperature program protocol wereextensively examined. The products were characterized by XRD, low temperature N2adsorption and TEM. It exhibited that the best ratio of R/MCM-48 and R/water were0.575 and 0.15 respectively. The best carbonization temperature was 800℃. Itfounded that the pore sizes of the porous carbons were predominantly 2-3 nm and thesurface area was about 1600 m2/g. These carbons exhibited small angle of XRD linesand TEM analysis revealed the order of the basic frameworks in the material. It hadsingle periodic structure of 2.4 nm. Furthermore, the mechanism and process how theRF particular was introduced inside the as-synthesized MCM-48 were discussed.
Keywords/Search Tags:mesopores, carbon molecular sieves, template, order, MCM-48
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