Abstract:The performance of zeolite catalysts depends not only on the strength and number of Brønsted acid (or exchange) sites but also on synergistic effects derived from their proximity, in particular, and their distribution, in general. Little is known on the genesis of acid sites and site distributions in hydrothermal zeolite synthesis. By an extensive study of five crystallization systems yielding ZSM-5 (MFI) and SSZ-13 (CHA), with a focus on interzeolite conversion (IZC) methods, several synthesis factors and mec… Show more
“…127 A good argument in favour of non-selective heterogeneous nucleation can be found from our kinetic study of FAU-to-MFI and FAU-to-CHA (Si/Al P ¼ 40). 47 In this work, it was demonstrated that nucleation occurred swily around one hour of FAU-to-MFI vs. 16 hours for amorphous (non-IZC) counterparts. The same time is required for FAU-to-CHA in equimolar compositions, which is a more structuralsimilar transformation.…”
Section: Role Of Al In Nucleationmentioning
confidence: 73%
“…Some interesting studies are those reporting (changes in) element yields throughout the crystallization process. 47,65,93,107 Nishitoba et al present exemplary temporal results in their LTLto-CHA and FAU-to-CHA IZC (Si/Al P ¼ 3.0; Si/Al B ¼ 15, Fig. 6).…”
Section: Role Of Al During Growthmentioning
confidence: 95%
“…11, purple). 47 A gel-containing phase was encountered in both the IZC and the non-IZC syntheses before successfully achieving MFI (Si/Al ¼ 40, alkali-free) crystals, seemingly indicating that a (slower) gel-mediated mechanism is necessary to assemble MFI with a relatively high content of Al in alkali-free mixtures. The later ndings on Al-averse systems (alkalifree MFI) add additional arguments to the theory that different mechanisms prevail at different Al contents, 123 and support growth theories in IZC mixtures based on charge-balancing.…”
Section: Role Of Al During Growthmentioning
confidence: 99%
“…106 Very recently, some interesting high Si IZC studies have investigated the full course of crystallization, also encompassing the crucial dissolution step. 47,65,107,108 In 2019, our group published work on FAU-to-CHA (Si/Al P ¼ 40) using simply commercial US-Y (CBV780; Zeolyst) and N,N,N-trimethyl-1adamantammonium hydroxide (TMAda-OH) at alkali-free molar batch compositions. 65 Most recently, the investigation was broadened to study FAU-to-MFI under the same conditions, using tetrapropylammonium (TPA) as OSDA.…”
Section: Role Of Al In (Zeolite) Dissolutionmentioning
confidence: 99%
“…From the combined ndings of these four kinetically studied IZC systems, a kinetic growth model for IZC is proposed with some generic features. 47 In the latter it was motivated that IZC synthesis mixtures prosper particularly well in assembly conditions with preferential Al uptake (Al-loving), rather than in Al-averse ones (rather scarce). Aer longer synthesis times, the peculiar Al-averse system (FAUto-MFI, Si/Al P ¼ 40; OH/Si ¼ 0.35; no Na) reaches a maximum (100%) crystallinity and yield (48 h) (Fig.…”
“…127 A good argument in favour of non-selective heterogeneous nucleation can be found from our kinetic study of FAU-to-MFI and FAU-to-CHA (Si/Al P ¼ 40). 47 In this work, it was demonstrated that nucleation occurred swily around one hour of FAU-to-MFI vs. 16 hours for amorphous (non-IZC) counterparts. The same time is required for FAU-to-CHA in equimolar compositions, which is a more structuralsimilar transformation.…”
Section: Role Of Al In Nucleationmentioning
confidence: 73%
“…Some interesting studies are those reporting (changes in) element yields throughout the crystallization process. 47,65,93,107 Nishitoba et al present exemplary temporal results in their LTLto-CHA and FAU-to-CHA IZC (Si/Al P ¼ 3.0; Si/Al B ¼ 15, Fig. 6).…”
Section: Role Of Al During Growthmentioning
confidence: 95%
“…11, purple). 47 A gel-containing phase was encountered in both the IZC and the non-IZC syntheses before successfully achieving MFI (Si/Al ¼ 40, alkali-free) crystals, seemingly indicating that a (slower) gel-mediated mechanism is necessary to assemble MFI with a relatively high content of Al in alkali-free mixtures. The later ndings on Al-averse systems (alkalifree MFI) add additional arguments to the theory that different mechanisms prevail at different Al contents, 123 and support growth theories in IZC mixtures based on charge-balancing.…”
Section: Role Of Al During Growthmentioning
confidence: 99%
“…106 Very recently, some interesting high Si IZC studies have investigated the full course of crystallization, also encompassing the crucial dissolution step. 47,65,107,108 In 2019, our group published work on FAU-to-CHA (Si/Al P ¼ 40) using simply commercial US-Y (CBV780; Zeolyst) and N,N,N-trimethyl-1adamantammonium hydroxide (TMAda-OH) at alkali-free molar batch compositions. 65 Most recently, the investigation was broadened to study FAU-to-MFI under the same conditions, using tetrapropylammonium (TPA) as OSDA.…”
Section: Role Of Al In (Zeolite) Dissolutionmentioning
confidence: 99%
“…From the combined ndings of these four kinetically studied IZC systems, a kinetic growth model for IZC is proposed with some generic features. 47 In the latter it was motivated that IZC synthesis mixtures prosper particularly well in assembly conditions with preferential Al uptake (Al-loving), rather than in Al-averse ones (rather scarce). Aer longer synthesis times, the peculiar Al-averse system (FAUto-MFI, Si/Al P ¼ 40; OH/Si ¼ 0.35; no Na) reaches a maximum (100%) crystallinity and yield (48 h) (Fig.…”
The inter‐zeolite conversion is a method to convert one meta‐stable zeolite to a thermodynamically stable zeolite. Despite the enormous interest, this method is yet to be popularized or standardized in the zeolite community. Intending to provide more insights into hydrothermal conversions from one zeolite to another, this work developed a novel one‐pot and flexible synthetic protocol to efficiently obtain the meta‐stable *BEA topology and its derived MTW topology by varying the hydrothermal crystallization time. This inter‐zeolite conversion process led to changes in the zeolite framework and modified physicochemical properties during the process. Such a transformation was feasible by forming hierarchical zeolite phases sharing a similar “mtw”‐based common building units, possibly driving such conversion. The structure‐reactivity relationship of four different zeolite materials, synthesized from this one‐pot inter‐zeolite conversion method, was established concerning their performance in the methanol‐to‐hydrocarbon (MTH) process, which has been well supported by operando UV‐vis diffuse reflectance spectroscopic study coupled with online mass spectrometry and solid‐state NMR spectroscopy. As a result, the pathway to synthesize various target zeolites from an identical initial synthesis gel with desired physicochemical properties has been scrutinized.
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