Ring Channels Research Articles

Two Carboxylate-Cyanurates with Strong Optical Anisotropy and Large Band Gaps.

The first metal carboxylate-cyanurates, namely, K(H3C3N3O3)(HCO2) (I) and Ba2(H2C3N3O3)(CH3CO2)3(H2O) (II), which contain π-conjugated carboxylate and cyanurate groups, have been synthesized by hydrothermal methods. They crystallize in centrosymmetric space groups of P1̅ and P21/n, respectively. Compound I exhibits a novel three-dimensional (3D) structure based on a [K(H3C3N3O3)]+ cationic framework with 12-membered ring (12-MR) channels, and the (HCO2)- anions are located within the 12-MR channels. The [K(H3C3N3O3)]+ cationic framework is composed of K+ ions interconnected by H3C3N3O3 ligands. Compound II features a 3D network formed by [Ba2(CH3CO2)3]+ cationic double chains bridged by (H2C3N3O3)- anions. The [Ba2(CH3CO2)3]+ cationic double chain is composed of (CH3CO2)- anions and Ba2+ ions. Optical property measurements show that both compounds exhibit short ultraviolet cutoff edges (I, 208 nm; II, 218 nm) and wide band gaps (I, 5.43 eV; II, 5.20 eV). Importantly, K(H3C3N3O3)(HCO2) (I) features a large birefringence of 0.285@532 nm due to the parallel alignment of π-conjugated H3C3N3O3 and (HCO2)- groups, indicating that K(H3C3N3O3)(HCO2) (I) is a promising short-wave ultraviolet birefringent material. Detailed theoretical calculations elucidate that their excellent optical properties originate from the synergetic effect of both types of π-conjugated groups.

Investigation of multi loop linear magnetic circuits of electromagnetic flow converters with ring channels

Mathematical models of single and multiloop magnetic circuits of electromagnetic flow transducers with an annular channel are designed taking into account the parameters of the magnetic circuit. The possibility of compensating the difference in magnetic resistances of coaxially located concentric ferromagnetic cores and the difference in their circumference by selecting the thickness of the cores is shown. It has been installed that the magnetic flux in ferromagnetic cores is distributed along the angular coordinate. The magnetic induction in the annular channel is unevenly distributed along the radial coordinates. It was found that with an increase in the value of the attenuation coefficient of the magnetic field in the magnetic circuit, the degree of magnetic induction in the annular channel increases along the angular coordinate, while it remains constant along the radial coordinate.

Two-dimensional microporous GAM-6 formed by the interzeolite conversion of CoAPO-5.

The interzeolite conversion of CoAPO-5 with piperidine assistance yielded a new microporous zeotype, GAM-6. Characterization and structural elucidation revealed that GAM-6 has a 3-ring local structure and two-dimensional 10-ring pore channels, and shows reasonable microporosity and solid acidity.

Improved catalytic performance in gas-phase dimethyl ether carbonylation over facile NH4F etched ferrierite.

Gas-phase dimethyl ether (DME) carbonylation to methyl acetate (MA) initiates a promising route for producing ethanol from syngas. Ferrierite (FER, ZSM-35) has received considerable attention as it displays excellent stability in the carbonylation reaction and its modification strategy is to improve its catalytic activity on the premise of maintaining its stability as much as possible. However, conventional post-treatment methods such as dealumination and desilication usually selectively remove framework Al or Si atoms, ultimately altering the intrinsic composition, crystallinity, and acidity of zeolites inevitably. In this study, we successfully prepared a series of hierarchical ZSM-35 materials through post-treatment with NH4F etching, which dissolved framework Al and Si at similar rates and preferentially attacked the defective sites. Interestingly, the produced pore systems effectively penetrated the [100] plane, offering elevated access to both the 8-membered ring (8-MR) and 10-membered ring (10-MR) channels. The physicochemical and acid properties of the pristine and NH4F etched ZSM-35 samples were comprehensively characterized using various techniques, including XRD, XRF, FESEM, HRTEM, Nitrogen adsorption-desorption, NH3-TPD, Py-IR, 27Al MAS NMR, and 29Si MAS NMR. Under moderate treatment conditions, the intrinsic microporous structure, acid properties, and crystallinity of zeolite were retained, leading to superior catalytic activity and stability with respect to the pristine sample. Nonetheless, severe NH4F etching disrupted the crystalline framework and created additional defective sites, bringing about faster deposition of coke precursors on the interior Brønsted acid sites (BAS) and decreased catalytic performance. This technique provides a novel and efficient method to slightly enhance the micropore and mesopore volume of industrially pertinent zeolites through a straightforward post-treatment, thus elevating the catalytic performance of these zeolites.

Adaptive modulation methods for combating Doppler shift on correlated double ring channel using FBMC

Adaptive modulation methods for combating Doppler shift on correlated double ring channel using FBMC

Experimental and numerical investigation of bistability in rotating permanent magnet-generated electrolyte flow in a ring-shaped container

Here, the stability of a transversely magnetized rotating permanent magnet-generated flow in a concentric cylindrical ring channel is studied. Numerical calculations show that the steady-state solution becomes asymmetric through a pitchfork bifurcation at a Reynolds number (Re) of 60. The two new antisymmetric steady-state solutions become cyclic at Re = 90. Nonlinearities develop at larger Re values and the limit cycle solutions are destabilized at Re = 250, enabling random transition events between the two pitchfork branches. Such transitions have been observed in all kinds of natural phenomena, spanning from neuroscientific to astrophysical systems, which are often too complex to be directly computed. Our presented system is physical yet simple enough to be used to conduct a parametric study with full three-dimensional direct numerical simulations. It raises the possibility of numerically and experimentally analyzing transitions in more detail. Experimental measurements indicated the existence of long-lived states and suitability for the proposed system for future studies of such phenomenon. However, the experimental results did not conclusively observe bistability.

Charge-separation driven mechanism via acylium ion intermediate migration during catalytic carbonylation in mordenite zeolite

By employing ab initio molecular dynamic simulations, solid-state NMR spectroscopy, and two-dimensional correlation analysis of rapid scan Fourier transform infrared spectroscopy data, a new pathway is proposed for the formation of methyl acetate (MA) via the acylium ion (i.e.,CH3 − C ≡ O+) in 12-membered ring (MR) channel of mordenite by an integrated reaction/diffusion kinetics model, and this route is kinetically and thermodynamically more favorable than the traditional viewpoint in 8MR channel. From perspective of the complete catalytic cycle, the separation of these two reaction zones, i.e., the C-C bond coupling in 8MR channel and MA formation in 12MR channel, effectively avoids aggregation of highly active acetyl species or ketene, thereby reducing undesired carbon deposit production. The synergistic effect of different channels appears to account for the high carbonylation activity in mordenite that has thus far not been fully explained, and this paradigm may rationalize the observed catalytic activity of other reactions.

Tailored alkyl-imidazolium templating synthesis of extra-large-pore germanosilicate zeolite ITT as Baeyer-Villiger oxidation catalyst

Extra-large-pore germanosilicate zeolite ITT was prepared with several structure-tailored alkyl-substituted imidazolium templates. The effect of alkyl chain length and substitution number of template on zeolite topology structure was studied with the variation of synthesis Si/Ge ratio. 1-hexyl-3-methyl-imidazaolium (1H3M) exhibited superior templating effect on the formation of ITT structure within the widest range of synthesis Si/Ge molar ratio of about 2–6. 1H→13C CP/MAS NMR, TGA and molecular simulation results revealed that two 1H3M was occluded in the 18-ring channels per unit cell, presenting the lowest interaction energy with framework. With the combination of XRD, SEM, EDS, ICP, 29Si, 19F MAS NMR, FTIR, N2 physisorption results, it was found that the increase of synthesis Si/Ge ratio improved framework Si/Ge ratio within d4r unit to a certain degree, and in the meantime resulted in the decrease of zeolite crystallinity with the formation of some amorphous phase. ITT showed better Lewis-acid catalytic activity and lactone selectivity for B–V oxidation of 2-adamantanone than BEC, the best germanosilicate zeolite ever reported. The excellent catalytic performance was ascribed to the presence of 18-ring channels in ITT, which facilitated the diffusion of bulky ketone substrate and lactone product. The structure stability of ITT during the reaction was evaluated with the use of either aqueous H2O2 or non-aqueous tert-butyl hydroperoxide (TBHP) as oxidant.

Preparation of hydrophobic Ti-beta catalyst derived from Al-rich zeolite beta synthesized without using organic structure-directing agent and its enhanced catalytic performance for phenol oxidation

Crystalline microporous titanosilicates with multi-dimensional 12-ring channels are potentially useful as catalysts for the oxidation of phenol with H2O2. Among them, titanosilicate version of zeolite beta (Ti-beta), which has three-dimensional, 12-ring micropores, is one of the most promising catalytic materials. The Ti-beta catalysts are preferably with Al-free and Na-free chemical compositions, and they can be conventionally crystallized via direct hydrothermal synthesis with the aid of a dipiperidinium-type organic structure-directing agent (OSDA) or via the so-called fluoride method using tetraethylammonium in a fluoride-containing medium. Another route involves a post-synthesis treatment such as the isomorphous substitution of Ti for Al starting from Al-rich zeolite beta. One of the Al-rich beta was synthesized in the absence of OSDA. We succeeded in converting it to Ti-beta, denoted as (Ti)-beta_OSDAF, for the first time via deep dealumination along with framework stabilization followed by Ti-incorporation using TiCl4. The (Ti)-beta_OSDAF was much more effective catalyst for the phenol oxidation with H2O2 than the directly crystallized Ti-beta materials prepared in the conventional techniques. The high efficiency of phenol oxidation was ascribed to an appropriate balance between hydrophilicity and hydrophobicity realized by increasing hydrophobicity of titanosilicate catalysts. The bulk hydrophobicity reflects that of the vicinity of active Ti sites. The enhanced affinity of hydrophobic moiety of phenol molecules with the hydrophobic surface around the vicinity of active Ti sites should facilitate the diffusion of phenol molecules to the active sites inside the micropores. The hydrophobicity of Ti-beta samples prepared by the various techniques in this work differed substantially, depending on the amount of silanol groups within the zeolitic framework. Positive effect of EtOH as an additive in the reaction mixture on enhancing the shape-selectivity of the (Ti)-beta_OSDAF catalyst was obvious, probably due to the increase in steric restriction by the EtOH molecules inside the pores of the catalyst. Moreover, the phenylsilylation of (Ti)-beta_OSDAF catalyst drastically increased its hydrophobicity, which was found to be effective for enhancing para-selectivity and turnover number.

PO41 Presentation Time: 4:45 PM: Initial Experience with the New Commercial Aarhus MR Compatible Hybrid Interstitial Brachytherapy Applicator in Indian Setting

<h3>Purpose -</h3> We have been using CT based intracavitary applicator in our clinic for cervical cancer. The advent of new hybrid applicator and short sequence cube MRI sequence opened up opportunity to do advanced MRI based brachytherapy in our clinic. We present the initial clinical experience of Aarhus ring and tandem MR compatible hybrid interstitial applicator with both straight and oblique needles and no ring channel (Varian may need to add TM) which was recently approved for use in a patient with bulky cervical cancer. <h3>Material and methods -</h3> A 45 years old lady, with initial diagnosis of carcinoma cervix, stage 1B3, completed External beam radiotherapy to a total dose of 45Gy in 25 Fractions, with a good clinical response, was taken up for further treatment with brachytherapy to a total dose of 28 Gy in 4 fractions. Brachytherapy was split into two applications one week apart and two treatment fractions delivered with each application, with 8 hours gap between each fraction.We used 60 degree Aarhus applicator set with Intrauterine tandem of 40 mm length and outer ring diameter of 32 mm. The Ring includes 19 guide holes for plastic interstitial needles arranged in 2 circles, 9 in inner circle for oblique needles and 10 in outer circle for straight needles.After external radiation patient underwent MRI pelvis with only T2 weighted axial and Cube sequences, which showed residual disease limited to cervix on the right side. The depth of needle insertion into the cervix was measured on MRI to be 3cms. Procedure performed under short general anaesthesia and 4 straight plastic needles through the ring were inserted with two on either side along with 4 cm central Tandem. CT and MR performed for both applications and fused. GTV-primary and HR CTV delineated on MRI, while OARs were delineated on CT. A dose of 7 Gy per fraction prescribed to HR CTV. An optimised plan was generated on eclipse treatment planning system with repeat CT planning for remaining fractions. <h3>Results -</h3> Treatment delivery went uneventful with very minimal blood loss. Average Dose per fraction received by 90 % of volume (D90) of HR CTV was 7.617 Gy and D98 of GTV primary was 10.35 Gy, delivering a total EQD2 of 89 Gy to HR CTV and at the same time delivering 115 Gy to the GTVp. OAR doses were well constrained with Bladder 2cc receiving 79.25 Gy, Rectum 2cc constrained to 53.48 Gy, sigmoid 2cc to 58.99 Gy and small bowel to 51.98 Gy. <h3>Conclusions -</h3> We successfully implemented MRI based planning with new Aarhus applicator in our clinic. Procedure was uneventful with excellent dosimetry. We will continue to use it in our clinic for patients with locally advanced cancer.

Insights into the role of Nup62 and Nup93 in assembling cytoplasmic ring and central transport channel of the nuclear pore complex.

The nuclear pore complex (NPC) is a highly modular assembly of 34 distinct nucleoporins (Nups) to form a versatile transport channel between the nucleus and the cytoplasm. Among them, Nup62 is known as an essential component for nuclear transport, Nup93 for proper nuclear envelope assembly. These Nups constitute various NPC subcomplexes such as the central transport channel (CTC), the cytoplasmic ring (CR), and the inner ring (IR). However, how they play their roles in NPC assembly and transport activity is not clear. Here we delineated the interacting regions and conducted biochemical reconstitution and structural characterization of the mammalian CR complex to reveal its intrinsic dynamic behavior and a distinct "4"-shaped architecture resembling the CTC complex. Our in vitro reconstitution data demonstrate that the Nup62 coiled-coil domain is critical to form both Nup62322-525 •Nup88517-742 and Nup62322-525•Nup88517-742•Nup214693-926 heterotrimers and both can bind to Nup931-150. We therefore propose that Nup93 acts as a "sensor" to bind to Nup62 shared heterotrimers including the Nup62•Nup54 heterotrimer of the CTC, which was not shown previously to be an interacting partner. Altogether, our biochemical study suggests that Nup62 via its coiled-coil domain is central to form compositionally distinct yet structurally similar heterotrimers and Nup93 binds these diverse heterotrimers nonselectively.

Highly sensitive sensing of a magnetic field and temperature based on two open ring channels SPR-PCF.

A surface plasmon resonance (SPR) sensor comprising photonic crystal fiber (PCF) is designed for magnetic field and temperature dual-parameter sensing. In order to make the SPR detection of magnetic field and temperature effectively, the two open ring channels of the proposed sensor are coated with gold and silver layers and filled with magnetic fluid (MF) and Polydimethylsiloxane (PDMS), respectively. The sensor is analyzed by the finite element method and its mode characteristics, structure parameters and sensing performance are investigated. The analysis reveals when the magnetic field is a range of 40-310 Oe and the temperature is a range of 0-60 °C, the maximum magnetic field sensitivity is 308.3 pm/Oe and temperature sensitivity is 6520 pm/°C. Furthermore, temperature and magnetic field do not crosstalk with each other's SPR peak. Its refractive index sensing performance is also investigated, the maximum sensitivity and FOM of the left channel sensing are 16820 nm/RIU and 1605 RIU-1, that of the right channel sensing are 13320 nm/RIU and 2277 RIU-1. Because of its high sensitivity and special sensing performance, the proposed sensor will have potential application in solving the problems of cross-sensitivity and demodulation due to nonlinear changes in sensitivity of dual-parameter sensing.

Preparation of shaped binderless mordenite catalysts with controllable crystal sizes and their carbonylation performance

A series of shaped binderless mordenite (MOR) zeolites were prepared through hydrothermal transformation with commercial MOR zeolite as seeds and aluminosilicate as raw materials. To investigate the effect of alkalinity on the crystallization process, samples with different Na2O/SiO2 ratios from 0.041 to 0.12 were synthesized and characterized by XRD, SEM, N2 adsorption-desorption, NH3-TPD, ICP-OES and pyridine adsorption-infrared measurements. It was surprisingly found that alkalinity plays a pivotal role in the formation of the binderless MOR zeolites. At Na2O/SiO2 of 0.041, MOR zeolite could not be formed. Slightly increasing the Na2O/SiO2 to 0.043 and upwards, the binderless MOR zeolite was formed. XRD patterns and SEM images revealed that the primary MOR zeolite particle size increased from 104 nm to 266 nm with the Na2O/SiO2 ratio increasing from 0.043 to 0.10. Further increasing Na2O/SiO2 ratio to 0.12 led to the formation of 0.6–1.6 μm micro-sized crystals. NH3-TPD and pyridine-adsorbed IR results indicated that the amount and strength of Brønsted acid sites in 8-membered ring channel (8-MR) decreased with the Na2O/SiO2 ratio increasing to up to 0.10. Superior catalytic performance in dimethyl ether carbonylation was observed on the catalyst with a Na2O/SiO2 ratio of 0.043, which exhibited the shortest diffusion path and highest 8-MR Brønsted acid amounts. This work provides a practical way of preparing and optimizing shaped binderless zeolites.

Selective enrichment of Brønsted acid site in 8-membered ring channels of MOR zeolite to enhance the catalytic reactivity of dimethyl ether carbonylation

Directional adjusting of the distribution of Brønsted acid site (BAS) in zeolite to control its catalytic performance is highly attractive but remains challenging. This study aims to tailor the distribution of BAS in 8-membered ring (B8-MR) of H-Mordenite (HMOR) by adding aniline or p-phenylenediamine as additives to the sol‐gel. The results reveal that the number of B8-MR is significantly increased but with a slight change in the number of BAS in 12-membered ring channels. When using dimethyl ether (DME) carbonylation as the probe reaction, the conversion of DME to methyl acetate over the synthesized HMOR zeolite is increased by nearly 2 times. Our finding not only provides a facile strategy to regulate the acid distribution in different channels of the HMOR zeolite but also offers a promising candidate for the catalytic DME carbonylation, which is a critical intermediate step for ethanol synthesis from syngas.

Dynamic Evolution of Aluminum Coordination Environments in Mordenite Zeolite and Their Role in the Dimethyl Ether (DME) Carbonylation Reaction

Part of tetrahedral framework aluminum in a protonic mordenite (HMOR) will convert geometry to distorted tetrahedral and octahedral coordination. High-field 27 Al NMR data show that more framework Al atoms at T3 and T4 sites change geometry to nonframework structures than others. These nonframework Al species preferentially reside in the side pockets, which will decrease the accessibility of acid sites in the 8-membered ring (MR) channel, impairing the dimethyl ether (DME) carbonylation reaction. The arisen octahedrally coordinated Al species are framework-associated, which can be reverted into the zeolite framework. Herein, we find that a facile treatment with pyridine could force the octahedral coordination Al back into a tetrahedral environment, which could increase the number of available active sites and enhance the diffusion of DME, thus improving the reactivity (4 times) of the DME carbonylation reaction and prolonging the lifetime of catalysts.

Dynamic Evolution of Aluminum Coordination Environments in Mordenite Zeolite and Their Role in the Dimethyl Ether (DME) Carbonylation Reaction

AbstractPart of tetrahedral framework aluminum in a protonic mordenite (HMOR) will convert geometry to distorted tetrahedral and octahedral coordination. High‐field 27Al NMR data show that more framework Al atoms at T3 and T4 sites change geometry to nonframework structures than others. These nonframework Al species preferentially reside in the side pockets, which will decrease the accessibility of acid sites in the 8‐membered ring (MR) channel, impairing the dimethyl ether (DME) carbonylation reaction. The arisen octahedrally coordinated Al species are framework‐associated, which can be reverted into the zeolite framework. Herein, we find that a facile treatment with pyridine could force the octahedral coordination Al back into a tetrahedral environment, which could increase the number of available active sites and enhance the diffusion of DME, thus improving the reactivity (4 times) of the DME carbonylation reaction and prolonging the lifetime of catalysts.

C(NH2)3]2Zn(CO3)2: A Guanidinium-Templated Ultraviolet Nonlinear Optical Material.

A novel guanidinium-templated ultraviolet (UV) nonlinear optical zinc carbonate crystal, [C(NH2)3]2Zn(CO3)2 (GZCO), has been synthesized in a closed system at low temperatures. GZCO crystallizing in the tetragonal noncentrosymmetric nonpolar space group, P41212 exhibits a three-dimensional anionic framework constructed by interconnected [Zn6C6O32] 12-membered ring channels with inorganic CO3 triangles and ZnO4 tetrahedra. Notably, the anhydrous GZCO shows a very high thermal stability among guanidine-based hybrid NLO materials benefiting from the confinement effect of the organic cations within inorganic channels. The UV-visible transmittance spectrum reveals that GZCO has a short UV cutoff edge of 210 nm, corresponding to the large band gap of 5.9 eV. GZCO exhibits a mild second-harmonic generation efficiency of 0.5 × KH2PO4 with type-I phase-matching behavior.

The Effect of Cation Exchange on the Pore Geometry of Zeolite L

Zeolites with the LTL framework topology are attractive materials for use in optoelectronics, gas adsorption and as chemical reactors. This is due to their unique, one-dimensional (1D) channel systems which are large enough to act as hosts for organic dye molecules and other guest materials. Here, we use high-resolution X-ray diffraction to show the effect of cation exchange on the pore geometry of LTL-type zeolites. The nature of the exchanging cation is shown to influence the free access diameter, volume and water content of the 12-ring (12R) channel systems. As such, cation exchange can be used to tune the molecular sieving and adsorption properties of LTL-type zeolites. This offers new possibilities for these materials in technologically relevant applications.

Aluminosilicate Zeolite EMM-28 Containing Supercavities Determined by Continuous Rotation Electron Diffraction.

A new aluminosilicate zeolite, denoted EMM-28, has been successfully synthesized on a large scale using 1,1-(3,3-(1,3-phenylene)bis(propane-3,1-diyl))bis(1-methylpyrrolidinium) hydroxide as an organic structure directing agent (OSDA), which was scaled up to an ∼20 g scale with a yield of 77%. It crystallizes as thin plates (40–100 nm in thickness), and the corresponding powder X-ray diffraction (PXRD) pattern shows significant peak broadening which makes it insufficient for structure determination. Continuous rotation electron diffraction (cRED) data collected from 13 crystals were successfully used to solve and refine the structure of EMM-28. This illustrates that cRED data are capable of performing structure determination despite limited PXRD data quality. EMM-28 has a unique framework structure containing supercavities, >21 Å in size, connected by one-dimensional 10-ring channels. High-resolution transmission electron microscopy (HRTEM) confirmed the structure model. The structure of EMM-28 is related to several known zeolite structures with large cavities.

Dimethyl ether conversion to hydrocarbons on the closely interconnected FER@ZSM-5 nanostructures

A superior catalyst activity and stability for dimethyl ether (DME) conversion to gasoline-range hydrocarbons (DTG) on a novel hierarchically-structured hybridized FER@ZSM-5 were verified in terms of the strong interactions of ZSM-5 on the plate-like FER nanostructures, which were prepared by alcohol additive with two organic structure-directing agent (OSDA). The highly active nanostructured FER@ZSM-5 with a propanol additive showed the closely interconnected and highly dispersed ZSM-5 aggregates on the larger plate-like FER surfaces, which were mainly responsible for the suppressed heavy coke depositions with the help of the closely interconnected ZSM-5 and FER interfaces with abundant acidic sites on 8-membered ring (8-MR) channels. The well-dispersed ZSM-5 nanoparticles on Brønsted acid sites of FER surfaces showed coke-resistant natures for DTG reaction due to the synergy effects of the strong acidic sites of the smaller ZSM-5 particles and larger Brønsted acid sites on the plate-like FER structures. • Superior activity and stability for DTG on the hybrid FER@ZSM-5 composite were verified. • FER@ZSM-5(Propanol) with closely interconnected nanostructures showed higher stability. • Less coke deposition was observed due to closely interconnected ZSM-5 and FER interfaces.