Synthesis Of Nanosized Zeolites And Structure Analysis Of Zeolites

Zeolites molecular sieve is a kind of inorganic microporous materials which iswidely used. To narrow the particle size of zeolites crystals to nanoscale, itsproperties will change. Micrometer-sized crystallites of zeolites are currently used oncatalytic and adsorption applications. Even their external surface are negligiblecompared to the large surface area developed in the internal micropores, The extent ofchemical reactions occurring at their external surface is therefore usually insignicantin comparison with the reactions occurring inside micropores, where their catalyticperformance is regulated by the multiple facets of shape selectivity.In separation processes by selective adsorption on zeolites, the kinetics of ad-and de-sorption steps are related to the particle size and therefore related research ofdifferent sizes even the nanosized zeolites have become the current hot issues. So Theanalysis of material performance and application research of small size zeolites arehave crucial significance. However, the structure resolution of small size molecularsieve materials has great difficulty with the restrictions on the size of crystal. Themethods commonly used are high resolution transmission electronmicroscopy(HRTEM), electron diffraction analysis, Powder X-ray diffraction（PXRD）and so on. Conbining the methods above to resolve the structure problem isthe most common on the international reports recently. But,in general, The progress tosolve these problem often need a long time. In order to solve this problem, this papertries to explores on the structure analytical methodology.First, we use the oxalate which is very cheap and accessible to control thepartical size of nanometer Beta zeolite. We use the method of HRTEM to identify andanalyze the samples after the synthesis of the Beta zeolite with nanometer size.In addition, based on the latest development of three-dimensional (3D) electron diffraction method to improved and developed by the use of data collection andpost-processing programs, We successfully obtained the structure information of LTAzeolite.Finally, we explore the application of Monte Carlo structure analysis method inspace for the first time, Which use the X-ray powder diffraction to simulation data,access to the crystalline structure of the LTA zeolite molecular sieve directly, Thisprogress can verify the Monte Carlo structure analysis method in X-ray powderdiffraction feasibility in the application of zeolite molecular sieve materials.Analysis the method of HRTEM transmission electron microscopic need a lot oftime to operate the instrument to complete the analysis of samples. In order to obtainhigh quality HRTEM images, we need the hash experimental condition extremely.But this method is still the most favorable technical means in determining thestructure of the crystal with defects.Compared with the traditional HRTEM structure analysis method,3D electrondiffraction technology has advantages like a fast data collection, easy to solve thestructure, and so on. Although electron diffraction under the influence of diffractiondynamic effects, the data can only be used to determine the skeleton structure, itcannot be used in the structure refinement. But with the combination of traditionaltechnology such as powder X-ray diffraction will be the most important technicalmeans of structure analysis to abtain the initial structure model.For data collection, high quality kinematical and complete Powder X-raydiffraction （PXRD） data can be obtained easily and fast. Powder X-ray diffractionpatterns contain information from bulk samples, which may include contributionsfrom more than one phase if the sample is not pure. For structure refinement, X-raypowder diffraction is a better alternative than electron diffraction, because it is moreaccurate and complete. Powder X-ray diffraction of Monte Carlo structure analysistested under the premise of the data of unit cell and the space group symmetry incrystallography has been known is more easy to operate to contrast HRTEM analysismethod of electron crystallography. At present, in the commonly used method ofpowder X-ray diffraction structure analysis in international are direct method, heavy atom method and Charge-flipping method. Monte Carlo method will become thepowder X-ray diffraction new options in the study of structure analysis of zeolites.