Carbon spheres prepared from zeolite Beta beads

Porous carbon beads were prepared from macroporous anion-exchange resin beads preliminary converted into resin-zeolite Beta composite or pure zeolite Beta spheres. Two synthesis procedures were used depending on the initial template employed. In a series of experiments, the resin from the resin-zeolite Beta composite was directly carbonized into carbon. In another series of experiments, the resin was removed by oxidation at 600 °C leaving behind self-bonded zeolite Beta beads, which were filled with carbon by chemical vapor deposition (CVD) of propylene. As a final step for both procedures, the zeolite was dissolved in hydrofluoric acid. All the carbons prepared inherited the macroscopic spherical shape of the template spheres as well as the morphology of the primary particles building up the beads. The synthesis procedure and the carbonization temperature or the temperature for CVD of carbon employed influenced the ordering and the pore structure of the produced carbons. The carbons prepared by direct carbonization showed relatively low surface areas, less than 1000 m² g⁻¹, and no zeolite structural regularity. The samples obtained via CVD maintained the zeolite ordering with a periodicity of 11.7 Å and had surface areas of over 2000 m² g⁻¹.     

Fabrication of interpenetrating polymer network to enhance the biological activity of synthetic hydrogels

A three dimensional porous hydrogel with suitable biological and mechanical properties are required for bone tissue engineering. Hydrogels of poly(lactic-ethylene oxide fumarate) (PLEOF), crosslinked with poly(ethylene glycol)-diacrylate (PEG-da) have desirable mechanical properties, however, their application for bone regeneration is limited due to the lack of cell motif sites within their structure. The aim of this study was to incorporate a naturally derived polymer such as gelatin into PLEOF hydrogels to promote their biological properties. Interpenetrating polymer network (IPN) was used as an efficient technique to acquire uniform mixture of these two polymers. Additionally gas foaming agents were used to create pores with average diameter of 250 μm in these IPN hydrogels. The concentrations of PEG-da and gelatin were optimized to tune the mechanical strength and degradation properties of these hydrogels. A compression modulus of 500 kPa was achieved for hydrogel fabricated with 400 mg/ml PLEOF, 200 mg/ml PEG-da and 150 mg/ml gelatin. The addition of gelatin to PLEOF elevated the compression modulus by two-fold and decreased the energy loss by 40%. The result of protein analysis demonstrated that IPN substantially enhanced the retention of physically crosslinked gelatin in the 3D structure of hydrogel. More than 50% of gelatin was retained in IPN hydrogel after two weeks of incubation in simulated physiological environment. Preserving gelatin in the hydrogel structure provides cell motif sites for a longer period of time, which is desirable for uniform cell proliferation. In vitro studies showed that primary human osteoblast cells adhered and proliferated in PLEOF-gelatin hydrogel. These results demonstrated the potential of using this IPN hydrogel for bone tissue engineering.     

The Synthesis of Discrete Colloidal Crystals of Zeolite Beta and their Application in the Preparation of Thin Microporous Films

Stable colloidal suspensions containing discrete crystals of zeolite Beta with particle sizes less than 150 nm were synthesized within a wide composition range. Crystallization of colloidal zeolite Beta was facilitated by low water and sodium contents and by high TEAOH contents. Solid samples obtained after drying were characterized using XRD and FT-IR. Thin (ca. 130 nm) films of zeolite Beta were grown on a Ta-substrate using colloidal crystals of zeolite Beta as seeds.     

Corrosion‐Resistant Parallel Fixed‐Bed Reactors for High‐Throughput Screening of New Deacon Reaction Catalysts

Two ten‐channel fixed‐bed reactor systems were developed for high‐throughput screening of new Deacon catalysts. The sequential ten‐channel reactor allows the determination of the activity of up to ten catalysts per day. With a ten‐channel ageing reactor the long‐time stability of catalytic activity can be tested in parallel. Both systems are robust, quite resistant against corrosion, and use the identical reaction tubes which enable the direct transfer of a catalyst from one to the other system. A mass‐spectrometric pulse method has been developed and applied successfully for the analysis of the corrosive product gas mixture of the Deacon reaction.     

Busting the efficiency of SAPO-34 catalysts for the methanol-to-olefin conversion by post-synthesis methods

As an effective non-petroleum based process for producing light olefins, the methanol-to-olefin(MTO) route has become an indispensable alternative to the industrial production of light olefins. The silicoaluminophosphate SAPO-34 zeolite(CHA-type structure) has proven to be an efficient industrial catalyst for the production of ethylene and propylene by the MTO reaction. However, the inherent structure and related diffusion limitations of SAPO-34 limit the mass transport and thus cause rapid deactivation of the catalyst. Fabrication of hierarchical SAPO-34 zeolite is one of the most effective strategies to address the intrinsic diffusion limitation. As simple, inexpensive, and efficient approach, the post-synthetic route has attracted considerable attention and widely used to introduce secondary meso-/macropores into the microporous SAPO-34 material. Significant effort has been dedicated to the development of post-synthesis strategies to prepare hierarchical SAPO-34 zeolite, thereby enhancing its catalytic performance in the MTO process. This mini-review addresses the post-synthesis preparation of hierarchical SAPO-34 catalysts and their MTO performance. Furthermore, some current problems and prospects of the post-synthesis route to hierarchical SAPO-34 catalysts are also revised. We expect this minireview to inspire the more efficient preparation of hierarchical SAPO-34 catalysts for the MTO process.     

Exfoliated Mesoporous 2D Covalent Organic Frameworks for High-Rate Electrochemical Double-Layer Capacitors

The electrochemical double-layer capacitors (EDLCs) are highly demanded electrical energy storage devices due to their high power density with thousands of cycle life compared with pseudocapacitors and batteries. Herein, a series of capacitor cells composed of exfoliated mesoporous 2D covalent organic frameworks (e-COFs) that are able to perform excellent double-layer charge storage is reported. The selected mesoporous 2D COFs possess eclipsed AA layer-stacking mode with 3.4 nm square-like open channels, favorable BET surface areas (up to 1170 m² g⁻¹), and high thermal and chemical stabilities. The COFs via the facile, scalable, and mild chemical exfoliation method are further exfoliated to produce thin-layer structure with average thickness of about 22 nm. The e-COF-based capacitor cells achieve high areal capacitance (5.46 mF cm⁻² at 1,000 mV s⁻¹), high gravimetric power (55 kW kg⁻¹), and relatively low τ₀ value (121 ms). More importantly, they perform nearly an ideal DL charge storage at high charge–discharge rate (up to 30 000 mV s⁻¹) and maintain almost 100% capacitance stability even after 10 000 cycles. This study thus provides insights into the potential utilization of COF materials for EDLCs.     

Electroactive Covalent Organic Frameworks: Design,Synthesis, and Applications

Covalent organic frameworks (COFs) are an emerging class of crystalline porous polymers with tailorable compositions, porosities, functionalities, and intrinsic chemical stability. The incorporation of electroactive moieties in the structure transforms COFs into electroactive materials with great potential for energy-related applications. Herein, the recent advances in the design and use of electroactive COFs as capacitors, batteries, conductors, fuel cells, water-splitting, and electrocatalysis are addressed. Their remarkable performance is discussed and compared with other porous materials; hence, perspectives in the development of electroactive COFs are presented.     

Ontology‐based model‐driven development of a destination management portal: Experience and lessons learned

We present a case study in model‐driven development of an e‐tourism portal that we chose to develop through generation from a domain model encoded as an ontology. We present (1) the requirements of e‐tourism portal, which dictated its high‐level design; (2) the principles behind our implementation strategy, including the use of a domain ontology as a starting model within the context of a model‐driven transformational approach; (3) the ontology development process and the code generation strategy used; and (4) the lessons learned. In particular, we compare our experiences to those reported in the model‐driven engineering (MDE) literature along 3 dimensions, ie, (1) the impact of MDE on the development process, (2) the choice of the modeling approach, and (3) the impact of code generation on design and code quality and testing. Overall, our experiences corroborated some of the theoretical claims and many of the practical experiences with MDE. Key findings include (1) model‐driven development makes maintenance, not development, more efficient; (2) it does require a higher skill level than traditional development; (3) clients and managers need to be educated into what incrementality means in a generative approach; (4) UML is neither necessary nor sufficient to handle the required representational flexibility; (5) it is difficult to build models that are good for both human consumption and code generation; and (6) it is difficult to generate code that is, simultaneously, efficient, pretty, and easy to maintain. We conclude by summarizing the findings of the paper.     

Core–Shell Zeolite Microcomposites

Core–shell zeolite composites possessing a core and a shell of different zeolite structure types have been synthesized. A characteristic feature of the obtained composites is the relatively large single‐crystal core and the very thin polycrystalline shell. The incompatibility between the core crystals and the zeolite precursor mixture yielding the shell layer has been circumvented by the adsorption of nanoseeds on the core surface, which induced the crystallization of the shell. The pretreated core crystals are subsequently subjected to a continuous growth in a zeolite precursor mixture. The feasibility of this synthetic approach has been exemplified by the preparation of core–shell β‐zeolite–silicalite‐1 composites. The synthesized composites have been characterized using X‐ray diffraction, high‐resolution transmission electron microscopy, and scanning electron microscopy. The integrity of the shell layer has been tested via N₂‐adsorption measurements on materials comprising a calcined core (β‐zeolite) and a non‐calcined tetrapropylammonium (TPA)‐containing shell, the latter being non‐permeable for the N₂ molecules. These measurements have shown that 86 % of the β‐zeolite crystals are covered with a defect‐free TPA–silicalite‐1 shell after a single hydrothermal treatment, while after three consecutive crystallization steps this value reaches 99 %. The shell integrity of the calcined composite has been studied by the adsorption of butane, toluene, and 1,3,5‐trimethylbenzene, which confirmed the superior performance of the triple‐shell composites.