(40b) Fabrication of b-Oriented TS-1 Film Over Silicon Wafer Under Steam-Assisted Crystallization
The film of molecular sieve on substrates is greatly fascinated for making microstructured catalytic reactors. In micro channel, ordered growth of molecular sieve could keep the inner surface smooth, the catalyst particles distribution even and fluids pass fluent, however, this is a significant challenge. Although many efforts have been made in achieving well-ordered molecular sieve films on substrates or in microchannels, most of them required complicated surface modification and synthesis procedures. We proposed a facile steam-assisted crystallization (SAC) method for synthesizing highly oriented Titanium Silicalite (TS-1) films. A solution was prepared by mixing tetraethoxysilane (TEOS), tetrabutoxytitanium (TBOT), tetrapropylammonium hydroxide (TPAOH) and distilled water. The solution was kept stirring for one hour at 277K, maintained at 358K for 5h to accelerate hydrolysis and eliminate the ethyl alcohol, and aged at room temperature under stirring for 24h to form a TS-1 precursor solution. A silicon wafer (100) cleaned in acetone under ultrasonication for 5 min, followed by rinsing with anhydrous alcohol and distilled water was placed on a PTFE holder, and then the TS-1 precursor solution was dripped on the wafer horizontally placed in PTFE-lined autoclave to crystallize at 413K for 24h and 448K for 36h by adding 0-2ml distilled water to a 60mL autoclave. The TS-1 film on wafer was rinsed with distilled water, and dried at 333K for 12h, subsequently, 1K/min temperature programmable increase to 823K under air and maintained 6h for removing template TPAOH. The surface and cross-section morphologies of the molecular sieve film were observed by field-emission scanning electron microscopy (FE-SEM, Hitachi S4800, 5kV). The orientation of crystals was analyzed by X-ray diffraction (XRD, Bruker D8 Focus) with Cu Ká radiation at 40kV and 40mA. Fourier transform infrared (FT-IR) spectrum of the film were recorded by a liquid nitrogen cooled MCT detector with p-polarized light incidence at 40° relative to the surface by using a Bruker accessory in an IFS-66v/S spectrometer (Bruker) at vacuum of 1-2 mbar. The spectra show a characteristic adsorption band at about 960 cm-1. The established procedure for synthesizing highly b-oriented continuous TS-1 film on silicon wafer avoided the formation of the dry gel coating and reduced the decomposition of template in crystallization. Some attempts of utilizing this method to construct a microreactor are underway.
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