| The thesis is consisted of two parts. On one hand, the comprehensive research has been carried out to study the factors that affect the catalytic properties of vanadium oxides and lead oxides catalysts for transesterification between dimethyl carbonate (DMC) and phenol. Novel heterogeneous catalysts with good reusability and value for industrialization were developed. High yield and selectivity toward target products were obtained in the transesterification reaction of DMC and phenol in the presence of selected catalysts. On the other hand, a novel3,5-pyrazoledicarboxylic acid coordication compound has been synthesized. The components and the structure of the compound have also been determined. The details of the study are as follows:1. Various V2O5catalysts have been prepared with NH4VO3as the precursor under different conditions and then characterized. The factors, including different carrier, loading amount, calcination time, calcination temperature and preparation method, have been investigated. The transesterification reactions were performed for10h under atmospheric pressure with the temperature at170±10℃. The molar ratio of DMC to phenol is1:1.5. The catalyst amount is4.5%(w/wto DMC). The GC results indicate that the V2O5/TiO2catalyst with the highest catalytic activity is prepared by being calcinated at550℃for5h with the NH4VO3to TiO2molar ratio1:2. Under the optimal conditions, the conversion of phenol and the yield of diphenyl carbonate (DPC) are35.420%and13.144%, respectively. The catalytic activity of V2O5/TiO2catalyst declines rapidly with increasing of repeated uses. The catalytic activity of V2O5/TiO2catalyst could be recovered after regeneration. XRD results prove that the deactivation of the catalyst could be due to the change on the V2O5crystal state or the leaching of active species V2O5. The catalytic activities of the vanadium oxide catalysts are not improved with the increasing of BET surface areas.2. The effects of carrier, precursor and preparation method on the catalytic activities of lead oxide heterogeneous catalysts have been studied. The transesterification reactions were performed for8h under atmospheric pressure with the temperature at170±10℃.The molar ratio of DMC to phenol is1:2. The catalyst amount is0.15g. The synthesis experiment results show that the highest activity of catalyst was achieved when the catalyst was prepared via impregnation method with Pb(OAc)2as the precursor and TiO2as the carrier. Under the optimal conditions, the conversion of phenol and the yield of diphenyl carbonate (DPC) are41.252%and14.205%, respectively. It is found in XRD results that the newly formed species PbTiO3could be active toward transesterification reaction apart from PbO. The materials prepared via co-precipitation hardly show catalytic activities. The possible explanations could be that PbO is in amorphous state. Besides, the lead oxide catalysts with high BET surface areas do not necessarily have high catalytic activities.3. Metal-organic framework which is a kind of coordination compounds with fascinating coordination modes and molecular structures has been a research hotspot to researchers in recent years, due to its potential applications in catalysis, non-linear optical materials and molecule recognition, etc. In this paper, a novel single crystal,[Ni(Hpdc)(2,2’-bipy)(H2O)2]-H2O (H3pdc=3,5-pyrazoledicarboxylic acid,2,2’-bipy=2,2’-bipyridine), was prepared under hydrothermal conditions. The structure of the coordination complex was determined by X-ray single crystal diffraction and characterized by elemental analysis, IR spectrum and thermogravimetric analysis. The coordination complex crystallizes in the triclinic system, space group Pi. The metal ion is located in the centre of a distorted octahedron. Ni(II) ion is six-coordinated with three oxygen atoms and three nitrogen atoms. Four molecules building up a cell unit are connected via hydrogen bonds while no π-π interactions were observed between aromatic rings. |
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