Synthesis And Characterization Of Novel Microporous Titanosilicate Materials

Recently, the rapid development of inorganic microporous materials in the areassuch as catalysis, host/guest assembly, etc. emphasizes the strategic status ofsynthesis and preparation chemistry of microprous materials. Since Flanigen andco-workers reported the preparation of AlPOs molecular sieves in 1982, there hasbeen much interest focused on preparation of microporous materials powder, singlecrystals, membrane and synthesis of novel open-framework materials. Thesematerials have not only potential applications in catalysis, ion-exchange, absorption,molecular recognization, ionic conductor, magnetic field, but also have greatsignificance in crystallography and the study of biomineralization. This work focuson synthesizing microporous materials with new structure and compositions andexploring new catalyst with potential applications. The synthesis and property of titanosilicates have attracted considerableattention owing to their excellent property of oxygen catalysis. Therefore, the goal ofour work is to synthesize new microporous titanosilicates. A new titanosilicate with a high Si/Al molar ratio (named JLU-3, JilinUniversity No.3), has been synthesized hydrothermally by using Triethylamine astemplate in the SiO2-NaOH-TiO2 system. Fasters such as the initial OH-/SiO2,TiO2/SiO2, and H2O/SiO2 molar ratios, template, crystallization temperature andtime which dominate the hydrothermal synthesis of product are discussed. Thesample has been characterized by XRD, IR, UV-Vis, TG-DTA, ICP, CHN, N2adsorption measurements. Its catalysis was studied via a model reaction. A new titanosilicate JLU-3 was obtained under autogenous pressure at 513K for3 days. The molar ratio of initial mixture was 486.0NaOH:3.0TiO2:1.0SiO2:2.2TEA:83.0H2O. The product was washed with distilledwater and dried over night at 323K to give the white powder. Pattern XRD ofindicates JLU-3 sample is a microporous material. IR spectrum of the JLU-3 showsstrong band at 960cm-1 assignable to vibration of Ti-O band in agreement with theliteratures. The UV-Vis spectra exhibit that the band at 220nm is associated with thevibration of the four-coordination Ti-O group, and the band at 270nm is attributed tovibration of the six-coordination Ti-O group. The investigations of TG and DTAshow that JLU-3 is thermally stable up to 1073K. A JLU-3sample exhibits very lowcatalytic activity in phenol hydroxylation, with the conversion of 1.0%. These resultssuggest that the Ti4+ species in this sample is six-coordinated, in good agreementwith the UV-Vis results.