Synthesis and characterization of porous layered solid acid /
Four types of zirconium phosphonates with interesting texture have been synthesized and characterized, including zirconium biphenylenebis(phosphonates), zirconium terphenylenebis(phosphonates), zirconium phosphate biphenylenebis-(phosphonates) and zirconium phenylphosphonates. These compounds have...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Subjects: | |
| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=764789991&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Four types of zirconium phosphonates with interesting texture have been synthesized and characterized, including zirconium biphenylenebis(phosphonates), zirconium terphenylenebis(phosphonates), zirconium phosphate biphenylenebis-(phosphonates) and zirconium phenylphosphonates. These compounds have been characterized by thermogravimetric analysis, X-ray powder diffraction (XRD), surface area analysis, elemental analysis, ³¹P solid state NMR, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When HF and 100% excess Zr were used in the synthesis, the resulting zirconium biphenylenebis-(phosphonates) (Zr-P₂-Ph₂) compounds have microporosity (10 - 20 []) and high surface areas (~400 m²/g). The micropore diameters range from 13 to 18 [], depending on the solvents and the amount of HF used. Zirconium 4,4''-terphenylenebis(phosphonates) (Zr-P₂-Ph₃) also have mostly microporous properties (11 - 17 []) if 100% excess Zr was used. SEM and TEM studies revealed that these samples have a stacked layer pattern, instead of a "house of cards" arrangement. A novel model is therefore proposed to explain the porosity and surface area data of these compounds. A number of porous sulfonated zirconium phosphonates, namely, sulfonated zirconium phenylphosphonate, sulfonated zirconium biphenylenebis(phosphonate) and sulfonated zirconium terphenylenebis(phosphonate), have been successfully synthesized. The use of SO₃ as the sulfonation agent instead of fuming H₂SO₄ virtually eliminates the possibility of water contact with the sulfonated samples. The surface acidity of these materials has been characterized in great detail by solid state MAS NMR studies of probe molecules. The results suggest that the acidity of several sulfonated samples is close to 100% H₂SO₄. The syntheses of structurally stable Al-pillared montmorillonites (Al-mont), Zr-pillared montmorillonites (Zr-mont), phosphated Al-mont, phosphated Zr-mont, sulfated Al-mont and sulfated Zr-mont have been successfully achieved. XRD and surface area analysis (SA) have been used mainly for structural characterization. The modified clays exhibit good thermal stability and surface area values of ~300 m²/g, and some samples retain their d-spacings after modification if prepared carefully. The acidity strength of the modified pillared samples has been investigated by solid state MAS NMR spectroscopy with acetone-2-¹³C adsorption. The phosphated Al-pillared montmorillonites have slightly weaker acidity after modification, but the phosphated Zr-pillared montmorillonites have much stronger acidity. Some of the acid sites in one sample even exhibit superacidity. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xviii, 213 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 193-207). |