Search

In this work, we show for the first time that high-silica zeolites (MFI, TON, MTT, and *MRE) could be synthesized from a combined strategy of both zeolite seeding and alcohol filling in the absence of organic structure-directing agents (OSDAs). High-silica ZSM-5 zeolites with Si/Al ratios ranging from 38 to 240 (TF-Al-ZSM-5) could be synthesized via this route. The key to the success of this technique was the employment of an aluminosilicate precursor with a fully 4-coordinated aluminum species as the initial source, wherein the rearrangement and condensation of the silicate species, rather than the aluminate species, occurred during zeolite crystallization. In addition, heteroatoms, such as Fe and B, could be incorporated into the zeolite frameworks. Catalytic tests for the methanol-to-propylene (MTP) reaction exhibited good catalytic performance for TF-Al-ZSM-5, which was comparable to that of the aluminosilicate ZSM-5 zeolite synthesized with OSDAs. Hence, this method offers viable opportunities for the industrial production and catalytic application of high-silica zeolites in the future.

Sustainable one-pot preparation of fully crystalline shaped zeolite catalysts is attractive for industrial applications but still challenging. Herein, for the first time, we show a one-pot preparation of fully crystalline shaped zeolite catalysts with MFI, TON, and MTT structures from a shaped precursor by crystallization via zeolite seeding and ethanol filling. As a typical example, a fully crystalline shaped ZSM-5 zeolite catalyst with a Si/Al ratio of 151 in the final product is well characterized by SEM, XRD, MAS NMR, particle strength analysis, N2 sorption, and XPS techniques, showing uniform crystals, high crystallinity, four-coordinated aluminum species, good mechanical strength, high surface area, and a core-shell structure. Very interestingly, catalytic tests in the methanol-to-propylene (MTP) reaction demonstrate that the fully crystalline shaped ZSM-5 zeolite catalyst has a much longer lifetime than that of the conventional one. Compared with the conventional preparation of shaped zeolite catalysts, this work has obvious advantages such as low-cost, environmentally friendly, simple, and fully crystalline features. These sustainable advantages plus the excellent catalytic performance should be of significant importance for the applications of these shaped zeolite catalysts in industrial processes.

Hierarchical zeolites attract people’s attention due to their enhanced mass transfer properties in catalytic reactions. The research over obtaining these zeolites in green and efficient methods is of great significance for the current post-treatments and templating strategies tend to be costly for hierarchical zeolite synthesis. In this research, nanosized mesoporous ZSM-5 (SN-ZSM-5) zeolites have been synthesized without the addition of mesoscale templates under highly concentrated conditions. The physicochemical characteristics were systematically investigated by XRD, SEM, N2 sorption, TEM, and NMR. The SEM images showed ZSM-5 crystals with sizes between 50–110 nm were obtained. N2 sorption and high-resolution TEM images gave direct evidence for the hierarchical structure of SN-ZSM-5. The forming mechanism for the hierarchical structure was proposed that the etching effect of the highly alkaline environment for the starting gels played a critical role in the formation of hierarchical structure. Catalytic tests in methanol-to-olefins (MTO) showed the SN-ZSM-5 performed a longer catalyst lifetime and higher propylene selectivity than the conventional ZSM-5 zeolites (C-ZSM-5) obtained from a traditional hydrothermal method. The features of hierarchical structure in the SN-ZSM-5 crystals and the sustainability for synthesis method could show a promising choice for wide applications of these SN-ZSM-5 zeolites in the future.

SSZ-39 zeolite with AEI framework structure is a good catalyst candidate for the methanol-to-olefins (MTO) reaction. However, the diffusion limitation and coke formation often results in fast deactivation of the SSZ-39 zeolite catalyst. One solution for this challenge is to introduce mesoporosity in the SSZ-39 zeolite. Herein, we report the synthesis of mesoporous SSZ-39 zeolite using an organosilane surfactant, N,N-dimethyl-N-(3-(trimethoxysilyl)propyl)octan-1-aminium chloride, as a mesopore template and N,N-dimethyl-cis-2,6-dimethylpiperidinium as a micropore template. The obtained zeolites were characterized by X-ray diffraction, N2 sorption, scanning electron microscopy, temperature programmed desorption of ammonia, and magic angle spinning nuclear magnetic resonance of 27Al. The results show that the mesoporous SSZ-39 zeolite has high crystallinity, meso/microporosity, high surface area, cuboid morphology, and abundant acidic sites. More importantly, this mesoporous SSZ-39 zeolite exhibits enhanced catalyst lifetime in the MTO reaction due to the presence of mesoporosity for fast mass transfer, compared with a conventional SSZ-39 zeolite without mesoporosity.

For the first time, SSZ-39 zeolite has been directly prepared using conventional colloidal silica and sodium aluminate instead of using FAU zeolite as the raw material in the alkaline media. The adjustment of the Si/Al ratios in the starting materials to the suitable values is a key factor to prepare the aluminosilicate SSZ-39 zeolite. Various characterizations (for instance, X-ray diffraction, scanning electron microscopy, nitrogen sorption, solid 27Al NMR, and NH3-temperature-programmed desorption) display that the aluminosilicate SSZ-39 zeolite owns high crystallinity, uniform cuboid morphology, large surface area, four-coordinated aluminum species, and strong acidic sites. Inductively coupled plasma analysis shows that the SiO2/Al2O3 ratios of the SSZ-39 products are ranged from 12.8 to 16.8. Considering the special framework of the SSZ-39 zeolite, the yield of this synthesis is not higher than 21.3%. Moreover, the catalytic performance of Cu-SSZ-39 catalyst synthesized from this route is excellent in the selective catalytic reduction of NO x with NH3 (NH3-SCR).

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity., This work is supported by National Key Research and Development Program of China (2017YFB0702803), National Natural Science Foundation of China (21703203, 21673205, 21835002 and 21875140), Shanghai Pujiang Program (17PJ1406400), and the Young Elite Scientist Sponsorship Program by CAST (2017QNRC001). This work is partially supported by CħEM, SPST, ShanghaiTech (Grant 02161943), the Spanish Government‐MICINN through “Severo Ochoa” (SEV 2012‐0267) and RTI2018‐101033‐B‐I00, and the European Union through ERC‐AdG‐2014‐671093 (SynCatMatch). This work was also supported by INCOE program of BASF SE.

Aluminosilicate SSZ-39 zeolite has been successfully prepared by transformation from ZSM-5 and beta zeolite in the presence of N,N-diethyl-cis-2,6-dimethylpiperidinium hydroxide (DMPOH) under hydrothermal conditions. Catalytic tests in the selective catalytic reduction of NOx with NH3 (NH3-SCR) show that the copper-exchanged products synthesized from the interzeolite transformation exhibit excellent catalytic performance.

Access to nanosized zeolites is a topical subject due to the advantageous mass transfer in zeolite catalyzed reactions. Herein we report a low-cost and generalized methodology to decrease zeolite crystal sizes by accelerating the nucleation rate when reducing the solvent amount in the synthesis. As anticipated, nanosized zeolites like MFI (100–200 nm, Si/Al ratios from 100 to ∞ in the starting gels) and BEA (50–200 nm, Si/Al ratio of 13) have been successfully synthesized with a H2O/SiO2 ratio of 2.0–3.0. The lower consumption of water as the solvent in the synthesis leads to non-centrifugation for nanosized zeolites, giving higher yields of the zeolite product. Experimental data confirm lower apparent activation energy for nucleation at higher gel concentrations in the synthesis of ZSM-5 zeolites. Catalytic examination of the conversion of methanol to olefins (MTO) demonstrates that the thus-obtained nanosized ZSM-5 zeolite (NS-ZSM-5) exhibits a much longer catalyst lifetime than conventional ZSM-5 (C-ZSM-5) and even nanosized ZSM-5 crystals (NC-ZSM-5) obtained from a hydrothermal route.

A large amount of zeolite structures are still not synthetically available or not available in the form of aluminosilicate currently. Despite significant progress in the development of predictive concepts for zeolite synthesis, accessing some of these new materials is still challenging. One example is the IWR structure as well. Despite successful synthesis of Ge-based IWR zeolites, direct synthesis of aluminosilicate IWR zeolite is still not successful. In this report we show how a suitable organic structure directing agent (OSDA), through modeling of an OSDA/zeolite cage interaction, could access directly the aluminum-containing IWR structure (denoted as COE-6), which might allow access to new classes of materials and thus open opportunities in valuable chemical applications. The experimental results reveal that the COE-6 zeolites with a SiO2/Al2O3 ratio as low as 30 could be obtained. Very interestingly, the COE-6 zeolite has much higher hydrothermal and thermal stabilities than those of the conventional Ge-Al-IWR zeolite. In methanol-to-propylene (MTP) reaction, the COE-6 zeolite exhibits excellent selectivity for propylene, offering a potential catalyst for MTP reaction in the future.

Large crystalline particles of ZSM-5 zeolites (S-ZSM-5) have been successfully synthesized by adjusting crystallization time and Si/Al ratios in the starting solid mixtures in the absence of water solvent. Catalytic tests in the methanol-to-olefins (MTO) reaction show that these S-ZSM-5 zeolites obtained from the solvent-free route exhibit superior catalytic properties including excellent propylene selectivity and extraordinarily long life in the MTO reaction. Particularly, when the crystallization time is 30 h and the Si/Al ratio in the starting solid mixture is adjusted at 150 under the solvent-free conditions, the S-ZSM-5-30h-150 catalyst with the large particle sizes (10–20 μm) gives propylene selectivity as high as 50.0% and catalyst life as long as 9 h, which are much better than those (propylene selectivity at 38.9% and catalyst life of 3 h) of the conventional ZSM-5 zeolite with smaller crystals (ca. 5 μm) synthesized from the hydrothermal route. High-resolution TEM images of these S-ZSM-5 zeolite...

A high-silica zeolite with a TON structure designated as ZJM-4 was successfully synthesized in the absence of any organic templates and zeolite seeds. Many factors such as the SiO2/K2O ratio, Si/Al ratio, SiO2/H2O in the starting aluminosilicate gels, crystallization temperature, and crystallization time strongly influence the formation of the ZJM-4 zeolite. Interestingly, this synthesis shows very efficient silica utilization in the starting gels (>80 %). Catalytic tests on the isomerization of m-xylene to p-xylene show that the ZJM-4 catalyst has high selectivity to p-xylene (ca. 80 %), which could be potentially important for industrial applications for the ZJM-4 zeolite as a candidate catalyst in the future.

As a commerical catalyst of high silica CHA zeolite for NH3-SCR reaction, controllable Al sites in CHA framework for improving catalytic performance are rarely reported. In this work, two organic templates (TMAda+ and DMCHA+) were employed to prepare aluminosilicate CHA zeolite with similar Si/Al ratios, donated as CHA-T and CHA-D. Detailed characterizations demonstrate that two completely distinguishable crystallization pathways can be identified as the preferential formation of smaller D6R units for CHA-D with DMCHA+ and larger 8MRs for CHA-T with TMAda+, resulting in spatially closer Al sites in CHA-D than CHA-T. As an interpretation, CHA-D with more paired Al atoms in 6MR generating more hydrothermally stable Cu2+-2Z sites contributes to higher activity than CHA-T at 400−550 °C. These results suggest that the crystallization pathways directed by rational choice of organic templates might be responsible for the controllable Al sites in the framework, which is important for designing efficient NH3-SCR catalysts.