The Synthesis And Characterization Of Novel Extra-large Pore Zeolites

Zeolite materials are an important class of crystalline inorganic microporous solids formed by TO4 tetrahedra (T infers Si, P, Al, Ge, Ga, etc) with a well defined regular pore system. The most interesting features of zeolites lie in their variable chemical compositions of the pore wall, as well as the tunable pore diameters and pore geometies. These excellent characters endow zeolites with wide applications in the fields such as adsorption, seperation, catalysis, microelectronics, medical diagnosis and, generally speaking, in any field where the host guest chemistry defines the final behavior of the system. According to the number of the pore ring, zeolites are classified as small, medium, large, and extralarge pore structure with the pore window delimited by 8,10,12 and more than 12 T-atoms, respectively. Extra-large pore zeolites are drawing more and more attention because they can process bigger molecule as desire in the fields mentioned above.Zeolite synthesis usually is taken within autoclave under hydro/solvothermal conditions, and more recently ionothermal method provides an alternative synthetic approach. These processes are often governed by a large number of parameters which determine the phases formed and the crystallization kinetics. Although considerable efforts were made to rationalize the zeolites synthesis, the relationship between synthesis variables and the zeolitic structure formed is not clearly understood, because of the metastable nature of zeolites and the complexity of the involved synthesis mechanisms. The application of combinatorial or high-throughput (HT) techniques to materials science can help chemists to increase the number of variables of a given process that can be studied in a reasonable time period as well as to increase the number of samples produced and characterized. Since 1998 Akporiaye et al. introduces HT technique into zeolite synthesis. The HT hydrothermal synthesis method has demonstrated its advantage in optimizing the zeolite synthetic conditions as well as in discovering the new types of zeolite.This thesis mainly focuses on the silicate based zeolite synthesis, using the High Throughput hydrothermal synthesis techniques, exploring a wide space of synthesis to obtain the extra-large pore zeolites with novel composition, novel structure and/or single crystal form. The results are listed below:1. In this thesis, we summarize almost all aspect of extra-large pore zeolites from synthesis, structure, stability and hypothetical structures, furthermore, suggest a numbers of principles to synthesis extra-large pore zeolite.2. Based on the principles suggested, we successfully synthesized novel germanosilicate zeolite ITQ-44 using novel synthesized monoquaternary ammonium within concentrate gel conditions. ITQ-44 possesses the 18×12×12 ring extra-large pore system. Interestingly, this structure already predicted by Treacy et al. using symmetry constrained bond-searching method years ago. With the help of the hypothetical structure, we are able to extract the final structure information from the powder X-ray differactions data within a significant reduced time period. In addition, ITQ-44 is a very open zeolite with lowest framework density (FD: 10.9 T-atom/?3) among the fully connected silicate zeolite to date. Notebly, ITQ-44 is the first zeolite with both Double 4 Rings (D4Rs) and Double 3 Rings (D3Rs).3. We found another extra large pore zeolite ITQ-43 within a similar synthesis condition with the ITQ-44. The structure solution is progressing. However, due to the lower symmetry of the structure, the differection peaks are extremely overlapping that prevent the identification. However, we still can extract some information that the material should be an extra large pore zeolite. The Ar adsorption gives us two clear two peaks centred at 7.181 ? and 11.496 ?. We did notice that, this is first time to report a zeolite Ar adsorption has two clear peaks attribute to two kinds of size distinguishable channel, and peak of 11.496 ? are biggest among all the zeolites including chiral mesoporous zeolite ITQ-37(10.2?)! So combining X-ray diffraction and Ar adsorption pore distribution analysis we can conclude that ITQ-43 is an extra-large pore zeolite.4. In this thesis, we also aim at understanding the extra-large pore formation rules. So we synthesized a series continues growing monoquaternatry ammounium and apply each of them into the High Throughput synthesis conditions considered the factor such as Si/Ge, Al,(B)/(Si+Ge), F-/(Si+Ge), H2O/(Si+Ge) etc. By the systemically variation of parameters with the help of controlled continually size growth of OSDA molecules, we can draw number of interesting conclusions about extra large pore zeolite synthesis:Similar conclusion to Camblor's that, concentrated gel favors the formation of low FD product.Germanium can direct the formation of small cages such as D4R, and even D3R.Continuous growth of Structure Directing Agent can break the"Default Structue"into"Extra-Large Pore Structures".There is a kind of competition between the introduction of F ion and Al framework substitutions; some zeolites fover the Al incorporation whereas some zeolites hate it, some zeolites can accept relative large amount of Al without changing the structure. While it is not so abvious to varing the phase selectivity by introduce the small amount of B into the zeolite.5. In the thesis, we synthesized two diquaternaty phosphonium cations. The application of them results in the formation of single crystal of ITQ-40. ITQ-40 is extremely rare interrupt framework zeolite which has 16×16×15 ring 3D extra-large pore system. Similar to ITQ-44, the framework of ITQ-40 also contains both D4Rs and D3Rs. Compare to powder X-ray differection structure, single crystal structure is more reliable and information riched. For example, there is an electronic density area within D3R. This electronic density peak most probably can attribute to F- ion. If so, this case are the first case that F- ion locate at the center of D3R!...