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This thesis presents research results from two projects involving molecular sieves. These investigations concern their synthesis, characterization and use as heterogeneous catalysis. In part I, the shape selectivity in the methanol-to-olefins (MTO) reaction is studied, and a new molecular sieve structure – MTO reaction selectivity relationship is developed. 17 zeolites and 13 phosphate-based molecular sieves having 14 selected cage-type/small-pore topologies (CHA, AFX, SFW, LEV, ERI, DDR, AEI, RTH, ITE, SAV, LTA, RHO, KFI, and UFI) are synthesized. The MTO reaction is performed using these catalysts at the same reaction conditions. The reaction results lead to the conclusion that the molecular sieve cage topology is the most important structural factor that primarily determines the olefin product distribution. For example, AEI and CHA are synthesized with four different elemental compositions (zeolite, SAPO, CoAPO, MgAPO). Regardless of differences in elemental compositions, very similar product distribution patterns are observed in each of the isostructural groups of molecular sieves. Additionally, other isostructural pairs of SAPOs and zeolites show similar product distributions. The reaction results from 14 topologies are grouped into four categories. Category I consists of CHA, AFX, SFW, and other GME-related topologies. Catalysts having these topologies show ethylene-to-propylene ratios close to one. Category II is a group of ERI and LEV which generate more ethylene than propylene. Category III is a group of DDR, AEI, RTH, ITE, and SAV which shows propylene selectivities higher than those of ethylene. Category IV is a group of LTA, RHO, KFI, and UFI which possess LTA-cages. These types of catalysts give high butylene selectivities. The concept of cage-defining ring and its size is introduced as a reliable geometric indicator on the basis of a hypothetical ellipsoid cage model. The cage-defining ring size can be easily calculated f

Zeolites are thriving as functional and stable materials in catalysis, sorption and even specialty applications. Besides their dominant presence in petrochem., their potential in the conversion of renewables and gaseous feedstock is huge (SCR, MTO, methane-​partial oxidn.)​, and often a single framework excels at a specific task. Although novel structures are being reported frequently, for some structurally-​relevant topologies, no effective synthetic aluminosilicate recipes are known. Natural or synthetic gmelinite (GME topol.) for example, is nearly always encountered with stacking faults (intergrowths) blocking the main channel and thus limiting porosity for application in catalysis. The search for fault-​free synthetic GME has been going on for ± 40 years, because the framework is a 3-​dimensional large pore zeolite, with a promising 12x8x8 channel system for relevant hydrocarbon chemistries, e.g. hexane isomerization or reactions where mol. traffic control is vital (compare to LTL)​. Interestingly, the framework can be entirely constructed by linking d6r composite building units. Here, we present a new route for making GME zeolites, labeled CIT-​9, based on the use of a simple org. structure directing agent (OSDA)​, with a remarkable cis-​trans isomeric specificity. Only cis-​N,​N,​3,​5-​tetramethylpiperidinium hydroxide leads to CIT-​9, while the trans form leads to SSZ-​39 of the AEI topol. AEI is an interesting cage-​contg. zeolite with 8MR small-​pore windows, and a documented excellent activity in SCR (Cu ions) and MTO (H+)​. The selectivity of synthesis also depends on the diln. of the synthesis suspension and thus the concn. of OSDA (selectivity to GME vs AEI in Figure 1) . The origin of both cis/trans and cage vs-​channel selectivity is investigated and confirmed from mol. modeling. Finally, in the light of catalysis, the novel GME is studied with rotation electron diffraction and variable temp. XRD, to monitor its faulting and thermal stability. In sho

The synthesis of the germanosilicate CIT-13, a molecular sieve that is the first to have a two-dimensional (2D) pore system possessing pores that are bounded by 14- and 10-rings, is accomplished using a family of monoquaternary, benzyl-imidazolium organic structure-directing agents (OSDAs) in aqueous media containing fluoride. CIT-13 is prepared using either hydrogen fluoride (HF) or ammonium fluoride (NH4F). The structure refinement suggests that most of the Ge atoms are located in the d4r(double-4-rings) units, and that there are framework disorders in the arrangement of those d4r units. Other characterizations of CIT-13 such as Si-29 MAS NMR spectra, Ar-adsorption isotherms, and so forth are presented and compared to those of IM-12 (UTL), a previously reported germanosilicate with 14- and 12-ring pores.