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Replacing homogeneous catalytic processes by heterogeneous routes based on the utilization of solid catalysts is of great interest from an environmental point of view. Owing to their genuine pore structure, zeolites such as mordenites (MOR) have emerged as game-changing materials to enable the heterogenization of catalytic processes including methanol carbonylation. Cu-exchange zeolites take the edge over pristine zeolites, leading to enhanced catalytic performance in terms of greater activity, selectivity, and stability. Herein, the overall catalytic activity and stability can be modulated upon controlling the environment and location of copper active sites in zeolites. In this study, Cu-exchanged mordenites were strategically synthesized to investigate the role of Cu location inside of MOR cavities under working conditions by means of in situ/operando infrared (IR) spectroscopic studies. The results obtained revealed that a major proportion of Cu in the MR-8 cavities notably enhances the activity and stability of the catalyst. This study provides crucial insights for fine-tuning zeolite catalysts to achieve the heterogenization of homogeneous carbonylation processes. [Display omitted] • Strategically prepared Cu-exchanged mordenite provides new insights for fine-tuning catalysts. • Controlling active site location in zeolites enhances stability and catalytic performance. • Cu in MR-8 cavities of mordenites enhances catalytic activity in methanol carbonylation. [ABSTRACT FROM AUTHOR]

Interzeolite transformation is a rapidly developing method of zeolite synthesis, which allows a precise design of the active site structure. We report on the application of MOR to MFI interzeolite transformation (IZT) for the preparation of MFI zeolite with variable content of paired sites and the elucidation of their role in the MTH reaction. IZT procedure involved hydrothermal treatment of the reaction mixture containing mordenite zeolite as a source of silica and alumina, alkali, TPAOH, TPABr and water. Tuning of paired sites was achieved by variation of the content of water and alkali in the reaction mixture and the application of seeding. The results demonstrate that IZT procedure allows to tune paired sites content within 10–65 % without affecting other characteristics of MFI products, such as Si/Al ratio, crystal size, texture, acid sites type, content and strength, as well as the amount of EFAL species and the distribution of aluminum between channels and intersections of the MFI structure. The evaluation of MOR-to-MFI zeolites with different paired sites content in the MTH reaction pointed to significant effect of paired sites on the stability of catalytic activity with time on stream and on the propylene/ethylene selectivity. [Display omitted] • Interzeolite transformation (IZT) of MOR zeolite into MFI has been fundamentally studied. • IZT allows regulation of paired Al sites content in the MFI zeolite in a wide range. • Paired Al sites enhance catalyst stability in the MTH reaction. [ABSTRACT FROM AUTHOR]

Highly active hierarchical mordenite zeolite with micro/mesoporosity (TM- n) for selective synthesis of cyclic acetals via acetylation reaction is reported. The hierarchical zeolite is synthesized using soft-templating approach with variations in octadecyltrimethoxysilane (OTMS/Al 2 O 3 ratio, n = 0.2, 0.3 and 0.4) in precursor hydrogels. The results reveal that OTMS not only creates secondary mesoporosity in zeolite framework (larger mesopore volume, external surface area, average pore diameter), but also influences the crystallization process, altering the crystal morphology, crystallinity and Si/Al ratios. Among TM- n zeolites prepared, TM-0.3 hierarchical mordenite has the optimum OTMS amount incorporated while further increasing the OTMS amount leads to the formation of ANA/GIS intergrowth. Thanks to the accessible hierarchical porosity, reduced acidity and morphological effects, the TM-0.3 hierarchical mordenite exhibits excellent catalytic performance (84.1% conversion, TOF = 0.087 s−1, 61.5% dioxolane selectivity) in acetylation of glycerol and benzaldehyde (160 °C, 20 min) better than pristine mordenite. The catalyst is reusable for five runs with minimal loss of activity (TOF = 0.087 → 0.084 s−1), making it a promising catalyst for chemical productions involving bulky molecules. In addition, comparative catalytic tests with classical homogeneous and heterogeneous catalysts, including H 2 SO 4 , HCl, CH 3 COOH, H–Y, H-LTL, Na-X, Na-A, were performed. [Display omitted] • Hierarchical mordenite is crystallized using new organosilane via soft templating method. • Octadecyltrimethoxysilane (OTMS) serves as a mesoporogen. • OTMS governs crystallization process, affecting morphology, crystallinity and Si/Al ratio. • Hierarchical modernite catalyst is very active in acetalization of benzaldehyde and glycerol. • 84.1% conversion with 61.5% selective to dioxolane is recorded at 160 °C for 20 min. [ABSTRACT FROM AUTHOR]

The distribution of acid sites in Mordenite (MOR) is crucial for its carbonylation performance. In this paper, MOR was subjected to acid treatment to selectively remove acid sites in 12 member-ring (MR) with the assistance of tetraethylammonium bromide (TEABr) used during synthesis process. The impact of acid treatment on structure, morphology, framework atoms and acidity were systematically studied. The characterization results indicated that the structure of the samples was only slightly impacted while the mesopore volume slightly increased. Due to the excessive removal of acid sites, the sample treated by nitric acid (0.1 mol/L) exhibited lower carbonylation activity whether with or without the protection of templates. However, the acid sites in the 12 MR were selectively removed in the citric acid treatment process by two different ways: the etching effect of H+ and the complexation of citric ions. The protection effect of templates for the acid sites in 8 MR was remarkable. Therefore, selective removal of acid sites in 12 MR was successful realized with assistance of template, leading to considerable improvements in activity for DME carbonylation reaction. [Display omitted] • Acid sites in 12 MR were selectively removed by acid treatment. • Templates could protect acid sites in 8 MR. • Samples treated with citric acid showed better activity for carbonylation reaction. [ABSTRACT FROM AUTHOR]

Zeolite mordenite (MOR, Si/Al = 10) was used as catalyst for the reaction between CO and dimethyl ether (DME) to give methyl acetate. Since the reaction is catalysed by Brønsted acid sites, Inelastic Neutron Scattering (INS) is an appropriate technique to identify the intermediates. Although the accepted mechanism goes through an adsorbed methoxy, its characteristic peak at 963 cm−1 was only detected in the reaction MOR + DME, in the absence of CO. When CO is present, the peak at 963 cm−1 is substituted by other peaks that give valuable information of the reaction intermediates, indicating that either methoxy intermediates are not formed or are quickly replaced by the acetyl intermediate, [SiO(COCH 3)Al], strongly stabilised in the micropore pockets of mordenite. Upon reaction of MOR + CO + DME, a characteristic peak at 1050 cm−1, although being present in liquid methyl acetate, could not be assigned to adsorbed methyl acetate since it loses intensity as the reaction proceeds (upon heating), and was assigned to a strong interaction between CO and DME adsorbed in one or two Brønsted sites, leading to some intermediate that shares this vibrational feature with methyl acetate in liquid phase. Finally, a peak at 1275 cm−1 in the spectrum of MOR + CO + DME upon heating is assigned to the formation of methyl acetate when the sample is heated, corresponding to C–O stretching of methyl acetate. This is further confirmed by the absence of this peak before heating. Overall, INS technique has allowed an accurate determination and interpretation of peaks involved in the carbonylation of DME in mordenite. [Display omitted] • Intermediates of reaction between CO and dimethyl ether (DME) to give methyl acetate, catalysed by Brønsted acid sites in mordenite (Si/Al = 10) have been identified using Inelastic Neutron Scattering (INS). • Peak analysis lead to establish three fingerprints as: • 963 cm−1 (due to adsorbed methoxy) was only detected in the reaction MOR + DME, in the absence of CO, and it is absent when CO is present. • 1050 cm−1 (characteristic of reaction of MOR + CO + DME) assigned to a strong interaction between CO and DME adsorbed in Brønsted sites. • 1275 cm−1 (in MOR + CO + DME + heat), corresponding to C–O stretching of methyl acetate, absent before heating. [ABSTRACT FROM AUTHOR]

The purpose of this research work is to prepare and assess the catalytic performance of platinum (Pt) dealuminated mordenite for the of n-hexane, n-pentane and light naphtha isomerization. The Pt dealuminated mordenite was prepared by dealumination of commercial mordenite catalyst by refluxing using hydrochloric acid at 100 °C in various time durations (0.50, 1.0, and 3.0 h). The commercial as well as dealuminated mordenite catalysts were examined by X-ray diffraction analysis, X-ray fluorescence, N 2 adsorption-desorption, Fourier-transform infrared spectroscopy, temperature-programmed desorption (NH 3 -TPD), scanning electron microscopy, and transmission electron microscopy with high resolutions XRD and BET surface area analysis. These afore mentioned studies confirm that the dealumination process exhibit an increasing the external surface area and improved the total acidity with retaining the structure of mordenite. The catalytic performance was investigated for the of n-hexane, n-pentane and light naphtha isomerization by varying factors such as, temperature, reaction pressure, hydrogen flow, hourly mass feed flow rate and catalyst mass. Among the catalysts, the dealuminated catalyst with SiO 2 /Al 2 O 3 ratio of 40% exhibited highest conversion Pt–Cl–Al 2 O 3 operate set the lowest temperature on and selectivity. The density functional theory (DFT) calculation implies that the activation free energy for isomerization of n-hexane varies with the position of interacting C–H bond with mordenite (Pt/Mordenite) cluster. Besides, the activation energy for the n-pentane isomerization is lesser than the n-hexane isomerization. Image 1 • The commercial mordenite zeolite was dealuminated (Si/Al = 28, 32, 40, and 50) successfully by acid leaching method. • N 2 sorption study, SEM and TEM confirms the enhanced textural properties and suitable morphology of mordenite (40) support. • Higher conversion and selectivity was seen over Pt/mordenite (40) catalyst for the isomerization of n-alkanes at 200 °C. • The DFT results showed that free energy activation of mordenite cluster varies with the position of interacting C–H bond. [ABSTRACT FROM AUTHOR]

The hierarchical Mordenite zeolites are synthesized by simple seed-assisted and OSDA-free method. The crystallinity, mesoporosity and the concentration of acid sites increase significantly with hydrothermal time. Formation and growth of the zeolite crystal are observed from electron microscopy. Based on the XRD and FESEM studies, the zeolite growth mechanism is postulated to be via seed surface crystallization. With the hydrothermal time, Si(0Al) species converts to Si(1Al) and Si(2Al), as observed from 29Si and 27Al SS-NMR. The maximum levulinic acid (LA) yields of 61, 56, 52 and 43% are obtained from bamboo sawdust, cellulose, glucose and fructose, respectively, over the hierarchical H-MOR catalyst. The humins are formed from the 5-Hydroxymethylfurfural with 2,5-dioxo-6-hydroxy-hexanal as an intermediate. Even though the yield of humins is lower in the biphasic system, the yield of LA (47%) is also lowered moderately. Lastly, the reaction mechanism is postulated for the conversion of biomass to LA and humins. Image 1 • Hierarchical Mordenite is synthesized using seed-assistant method. • Si(0Al) species converts to Si(1Al) and Si(2Al) at longer hydrothermal times, as observed from 29Si and 27Al SS-NMR. • The LA yields of 61, 56, 52 and 43% are obtained from bamboo sawdust, cellulose, glucose and fructose respectively. • Humins formation is from the 5-Hydroxymethylfurfural via aldol condensation with 2,5-dioxo-6-hydroxy-hexanal intermediate. • Humins from cellulose, glucose or fructose possesses a similar molecular, morphological structure and thermal behavior. [ABSTRACT FROM AUTHOR]

Abstract Mordenite (MOR) and faujasite (FAU) were formed as a membrane layer on tubular mullite and disk-shaped α-alumina supports for pervaporation (PV) dehydration of ethanol (EtOH). Structural analyses were carried out using XRD, SEM and EDAX. EtOH/water PV process was utilized to assess the membranes performances. The experiments show the fairly high separation factor representing the defect-free membrane layer and legible nonzeolitic pores on the top-layer. The effects of synthesis parameters including ceramic support, repetition of coating, seeding method, crystallization time (14 and 18 h) and temperature (160, 170 and 180 °C), and Si/Al ratio of the precursor gel formulation (12 and 16) on the membranes structures and their PV performances were investigated. Furthermore, the effective operational conditions (feed concentration (50, 70 and 90 wt% EtOH) and temperature (25 and 45 °C), and vacuum on permeate side (80 and 130 mmHg)) on PV performance of the membranes were studied. According to a combined performance parameter, pervaporation separation index (PSI), the MOR layer on α-alumina (MOR_D-II) can be reported as the best membrane for EtOH/water PV process. Permeation flux (43.43%), separation factor (30.39%) and PSI (62.35%) decrease with increasing EtOH concentration in feed (50–90 wt%). However, increasing feed temperature increases permeation flux and decreases separation factor, whereas applying higher vacuum in the permeate side leads to the opposite trend. Highlights • Secondary growth was used for seed deposition on mullite and α-alumina supports. • PV EtOH dehydration of the synthesized MOR and FAU membranes was determined. • Defect-free zeolite layer with negligible nonzeolitic pore was successfully formed. • Repetition of coating improved the selectivity of the final membranes. • Structural and operational analyses were done considering several parameters. [ABSTRACT FROM AUTHOR]

Abstract Detection of radiological iodine gas after nuclear accidents or in nuclear fuel reprocessing is necessary for the safety of human life and the environment. The development of sensors for the detection of iodine benefits from the incorporation of nanoporous materials with high selectivity for I 2 from common competing gases in air. Silver mordenite zeolite (Ag-MOR) is widely-used material for capture of gaseous iodine (I 2). Herein, thin film zeolite coatings were applied to Pt interdigitated electrodes (IEDs) to fabricate iodine gas sensors with direct electrical readout responses. Correlations between occluded ion, exposure to iodine gas, resultant AgI nanoparticle polymorphs and location in zeolite with resultant impedance spectroscopy (IS) properties are described. Furthermore, IS is leveraged to elucidate the changes in charge conduction pathways as determined by the cation-zeolite film incorporated in the sensor. Silver mordenite reveals a significant change in impedance upon exposure to gaseous I 2 at 70 °C, and the magnitude and direction of the response is dependent on whether the Ag+-mordenite is reduced (Ag0) before I 2 exposure. An equivalent circuit model is developed to describe the movement of charge along the surface and through the pores of the mordenite grains. Relative changes in the impedance of these conduction pathways are related to the chemical changes from Ag+ or Ag0 to resultant AgI polymorph phase. Together, these results inform design of a compact Ag-mordenite sensor for direct electrical detection of gaseous I 2. Graphical abstract Image 1 Highlights • Impedance spectroscopy for direct detection of I 2. • Sensor development based on the high selectivity adsorption of iodine gas species by Ag-MOR. • Correlations between Ag+, I 2 , formed AgI nanoparticles with resultant impedance spectroscopy. • Charge conduction pathways determined for the sensor's Ag-zeolite film. [ABSTRACT FROM AUTHOR]

Abstract In this study, the mordenite (MOR) zeolite is synthesized using a seed-assisted and template-free method and tested for glucose dehydration to 5-hydroxymethylfurfural (5-HMF). The synthesized zeolites are characterized by using X-Ray diffraction (XRD), N 2 -sorption, Field Emission Scanning Electron Microscopy (FESEM), Pyridine-FTIR, 27Al NMR and Thermogravimetric analysis. The mesoporosity has been introduced in the zeolite by the aging and/or with higher SiO 2 /Al 2 O 3 ratio. Colloidal silica (CS) as a precursor in combination with aging resulted in a unidirectional growth of the crystals, as evidenced by FESEM images and XRD. The MOR synthesized with CS as silica precursor under 12 h aging showed the best activity giving a 5-HMF yield of 66% (selectivity 87%) with a glucose conversion of 76% at 180 °C for 1 h. Mesoporosity and the optimum number of Lewis and Brønsted acid sites of the MOR played a key role in obtaining the best activity. Graphical abstract Image 1 Highlights • Highly crystalline H-MOR is successfully synthesized by OSDA-free and seed-assisted method. • Mesoporosity is induced to the samples by ageing and/or using high SiO 2 /Al 2 O 3 molar ratio. • Unidirectional growth of zeolite crystals (in the form of nano-cylinders) is observed. • The highest selectivity to 5-HMF (87%) is with the H-MOR from colloidal silica and ageing. • Optimum Lewis and Brønsted acid sites and mesoporosity are the key for the best activity. [ABSTRACT FROM AUTHOR]

Abstract Optical properties of indium-exchanged mordenite (MOR) zeolite have been studied using diffuse reflectance UV-Vis and photoluminescence (PL) spectroscopy. It has been found that reduced In-MOR zeolites, containing low-valence In+ exchange cations, can exhibit efficient ultraviolet and visible-light photoluminescence emissions of similar intensities. The results of the current study along with previous results on indium-exchanged ZSM-5 zeolite confirm previously made suggestion that the ultraviolet emission is associated with isolated In+ cations, while the visible-light photoluminescence is due to radiative relaxation of In+ excited-state oligomers/clusters. The PL properties of indium-exchanged zeolites thus can be tuned by changing the distance between In+ cations which in its turn can be controlled by indium loading and Si/Al ration in a zeolite framework. Graphical abstract Image 1 Highlights • Indium-exchanged mordenite zeolite exhibits efficient UV and visible light luminescence. • The visible light emission centers are In+ excited-state oligomers/clusters. • The PL properties of In-MOR can be tuned by changing the distance between In+ cations. [ABSTRACT FROM AUTHOR]

Abstract High performance mordenite zeolite membranes were fabricated on four-channel Al 2 O 3 hollow fiber substrates for the first time by using ball-milled mordenite particles as seeds. It was found that the particle size of seed played a vital part in the growth of membrane layers. The mordenite particles with a size of approximately 300 nm via ball milling enabled the growth of zeolite to form a uniform and defect-free zeolite membrane. The as-fabricated membranes showed high performance for isopropanol (IPA)/water mixtures separation. For IPA/H 2 O (90/10 wt%) mixture dehydration at 75 °C by pervaporation, the permeation flux of 1.43 kg m−2 h−1 and the separation selectivity of >10000 were achieved. The influence of feed water content on the separation performance of mordenite membrane was studied in detail. In addition to good dehydration performance at a low feed water content, the mordenite zeolite membranes also demonstrated long time stable separation performance for high feed water content systems. Permporosimetry measurements and molecular simulations showed that, unlike NaA zeolite crystal, the adsorbate water affected the expansion/contraction of MOR zeolite crystal framework weakly. Our research shows that MOR zeolite membrane shows good potential for the industrial solvent dehydration applications. Graphical abstract Image 1 Highlights • High-quality hollow fiber supported mordenite zeolite membranes were fabricated. • The effect of seed size on the property of membranes was investigated. • MOR membranes showed good stability for isopropanol/water separation during vapor permeation. • Water adsorption affects slightly on MOR zeolite crystal unit cell size at low water loading. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a series of hierarchical MOR catalysts were synthesized by using PEG as templates. The structural and acid properties of obtained MOR catalysts were systematically investigated by XRD, N 2 adsorption-desorption, SEM, NH 3 -TPD and DME-TPD. The characterization results showed that the crystallinity of the MOR catalysts nearly doubled with the addition of PEG molecules. The specific surface area and total pore volume increased on the hierarchical MOR catalysts and showed a strong dependence on the PEG molecular weight. Compared with the reference sample, the specific surface area and total pore volume increased by 80.3 m2 g−1 and 0.017 cc. g−1 respectively when using PEG-6000 as template. The strong acid sites slightly increased and the amount of DME adsorption also increased due to the combined effect of hierarchical structure and increasing amount of strong acid sites. The mass transfer efficiency in the hierarchical MOR catalyst was largely improved after the introduction of mesopores. The catalytic activity and stability of hierarchical MOR catalysts grudally increased with the PEG molecular weight. The single-pass lifespan over the PEG-6000 sample was 1.6 times of that on the reference sample. The amount of coke deposition over the deactivated hierarchical MOR catalysts gradually increased. Nevertheless, the H/C ratio of coke deposition increased as the space limitations of mesopores to the coke depositions were less obvious compared with micropores. Graphical abstract Image 1 Highlights • Hierarchical MOR were synthesized by using PEG as templates. • Mesopores concentrated around 2.5 nm were introduced by PEG molecules. • The mass transfer efficiency was largely enhanced due to the mesopores. • The carbonylation performance and stability of MOR were both improved. [ABSTRACT FROM AUTHOR]

Abstract The structural effect of Fe-, Zr- and FeZr-modified clinoptilolite-, mordenite- and chabazite-rich tuffs was examined on the As(V) sorption from aqueous solutions. Batch experiments were conducted considering the sorbent mass, contact time and pH. The most probable sites where Fe and Zr species could be located in the zeolite frameworks after the modification were described: Na+ exchangeable sites in the 10-ring and 8-ring channels of clinoptilolite, and inside the 12-ring and 8-ring channels and 8-ring side pockets of mordenite; Na+, K+ and Ca2+ sites within the D6R cages and barrel-shape cavities of chabazite. As(V) sorption capacities of Zr-modified materials (0.062 ± 0.008 mg/g) were higher than the Fe-modified ones (0.031 ± 0.007 mg/g). Isotherm results were best adjusted to the Freundlich model; FeZr-modified materials presented the highest affinity for arsenic. Estimated free energy values from the Dubinin-Radushkevich isotherm model suggested an ion exchange process. Kinetic data were well described by the pseudo-second order and intraparticle diffusion models, thus the sorption rate could have been controlled by two steps, the transfer of arsenic through the channel systems and the chemical interactions. Based on data modeling for the pH effect, zeolitic materials showed an optimal sorption in the pH range from 2 to 6; the major arsenic species involved in the sorption process were H 2 AsO 4 − and HAsO 4 2−. The mechanism for As(V) removal by the FeZr-modified zeolites was through the formation of an inner sphere complex via ion exchange. Graphical abstract Image 1 Highlights • Zeolite framework controlled the number and location of Fe and Zr binding sites. • Zr-modified zeolites showed higher As(V) capacities than Fe-modified sorbents. • FeZr-modified zeolite-rich tuffs presented the highest affinity for arsenic. • The predominant arsenic species involved in sorption process are H 2 AsO 4 −. [ABSTRACT FROM AUTHOR]

Constructing high-quality zeolite membrane by regulating solely the kinetics of zeolite nucleation and growth is desired because of its simplicity and potential industrial viability. Herein, a high-performance mordenite membrane was prepared without using organic template successfully on a macroporous tubular α-alumina support using a novel and simple intermittent hydrothermal synthesis (IHS) method. We aimed at regulating membrane synthesis kinetics by adjusting the concentration of the synthetic gel by introducing an unheated period of the oven in the middle stage of the synthesis process. In the proposed IHS method, the power supply of the oven can be switched off and on with the aid of a smart socket without manual operation, ensuring its feasibility and convenience. A thin and dense membrane layer was formed via the appropriate adjustment of presynthesis time, unheated time, and resynthesis time. The effects of each duration on the morphologies, microstructures, and pervaporation performances of the prepared mordenite membranes were investigated. Under optimized conditions, the as-synthesized mordenite membrane showed high pervaporation performance with a permeation flux and separation factor of 5.57 kg m−2 h−1 and >10000, respectively, in the dehydration of 90 wt% isopropanol/water mixture at 75 °C. This work provides a novel, simple, and feasible method for the preparation of high-performance zeolite membrane. [Display omitted] • A novel intermittent hydrothermal synthesis was first proposed to prepare high-quality zeolite membrane. • The mordenite membranes were fabricated on macroporous tubular α-alumina supports without using organic template. • The total hydrothermal synthesis time was as short as 6.5 h. • The membrane thickness was reduced, and its compactness was improved. • The membrane exhibited an excellent pervaporation performance for isopropanol dehydration. [ABSTRACT FROM AUTHOR]

Comprehensive research of water behavior in Na- and Cu-mordenites with different Na/Cu ratio was done. Several steps of dehydration process were detected and analyzed, taking into account difference in chemical composition of the samples, reaction models and corresponding kinetic equations. Activation energies for these steps were calculated. It was shown that the majority of dehydration steps for all zeolite samples studied might be associated with chemical reaction mechanism corresponding to the second order kinetic model, except for the most high-temperature step for Cu-mordenite, for which the third-order model has the higher correlation coefficient. A detailed analysis of rehydration processes was studied by proton NMR spectroscopy. The obtained results allow one to distinguish different types of water and to associate them with a certain localization of water molecules in zeolite voids: the main channel for both Na and Cu-mordenites; a side pocket of Na-mordenite; molecules coordinated with Cu 2+ cations in Cu-mordenite. The diffusion measurements carried out using static field gradient NMR technique proved that the water diffusion character below 300 K is essentially intracrystalline, whereas above 300 K it becomes intercrystalline. The activation energy of intercrystalline diffusion is about 28 kJ/mol and does not depend on the Na/Cu ratio. That allows us to suppose that in the studied zeolites the intercrystalline diffusion is governed by the morphology of the sample mainly. [ABSTRACT FROM AUTHOR]

Cu 2+ and Zn 2+ ion-exchange locations in mordenite (MOR) were evaluated using infrared spectroscopy, pore-size distribution, and temperature-programmed reduction. Isolated copper ions were the most abundant ion-exchanged species, as detected by UV-vis spectroscopy, in addition to oxide nanoparticles, with no presence of binuclear species, which was assigned to a low copper loading of 0.3 Cu/Al. The characterization revealed that only zinc could exchange in 8-membered rings. Hartree-Fock modeling confirmed copper exchange into 12-membered rings involving at least one T1 atom, and zinc exchange in T4 sites and in 8-membered structures, including T3 sites. Copper ion exchange did not offer improvement in the dimethyl ether carbonylation rate or selectivity over acidic mordenite. Zinc ion exchange led to the selectivity and stability improvement with some loss of activity. This work contributes to the understanding of acid and metal site contribution to DME carbonylation and contributes to the understanding for Cu 2+ and Zn 2+ ion-exchange locations in MOR with a low metal/Al loading (<0.2). [ABSTRACT FROM AUTHOR]

Sodium mordenite was Cu 2+ -exchanged by conventional methods at ambient temperature (accepted as 20 °C) and with microwave radiation at 100 ± 1 °C. To increase the copper content, we repeat the exchange procedure several times. Both the degree of Cu 2+ exchange and the environment of the Cu 2+ ions depend on the method of exchange. Neither conventional, nor microwave methods do not destruct the topology of mordenite framework. XRD pattern of the mordenite persists, but slight elastic deformation and some dealumination of the surface layer occurs. For all the studied samples, all the copper ions are in Cu 2+ state, neither Cu 1+ nor Cu 0 were detected. All the copper ions play the role of charge-balancing counter-cations. Their placement into the interior of zeolite causes the channel contraction due to electrostatic interactions of double charged cations with [AlO 4 ] δ– units. The increase of copper content is accompanied by increasing of number of water molecules per unit cell. In fully hydrated samples the copper cations are effectively separated from the zeolite framework and are fully surrounded by a water ligand shell. [ABSTRACT FROM AUTHOR]

Two kinds of zeolites (mordenite and AlPO 4 -5, with MOR and AFI topology, respectively) have been synthesized using hexamethyleneimine (HMI) as structure directing agent. It is found that HMI is incorporated intact in its protonated form in MOR and AFI. Furthermore, the oxidation of HMI restricted in the two zeolites by H 2 O 2 has been studied. Analysis of FT-IR, Raman spectra, TG/DTA, EA and 13 C MAS NMR show that the restricted HMI molecules are changed into saturated hydrocarbons and some other amines in AFI, whereas unchanged in MOR. The adsorption tests illustrated that the as-synthesized samples and their oxidized products have high adsorption capacity for Ni(II). This work opens new opportunities for further research of molecular reactions on the inorganic hybrids, and provides a new idea for the application of SDAs present in molecular sieves. [ABSTRACT FROM AUTHOR]

In this study, a mordenite-rich tuff (M) from the Şile region (NW Turkey) was treated with HNO 3 and H 2 SO 4 at various concentrations (1.0, 3.0 and 5.0 M) at 80 °C for 3 h. The adsorption properties of ethylene (C 2 H 4 ) and hydrogen (H 2 ) on natural and that of acid forms were examined experimentally at 273 and 77 K and up to 100 kPa using volumetric instrument, respectively. All the samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), and nitrogen (N 2 ) adsorption methods. Some differences on XRD pattern were signed in between natural and acid modified samples according to the intensity, sharpness and crystallite degree of mordenite peaks. C 2 H 4 and H 2 adsorption capacities of the original and acid treated mordenites were in the range of 0.762–0.876 mmol g −1 and 1.373–1.672 mmol g −1 at 273 and 77 K, respectively. The increasing retention values of C 2 H 4 and H 2 after the acid treatments were analyzed in comparison with the structural changes. [ABSTRACT FROM AUTHOR]

Cerium incorporated zeolite-modified carbon paste electrode (Ce-ZCPME) was studied for the anodic stripping voltammetric detection of lead and cadmium ions. The modified electrode which was fabricated in-house by a prior hydrothermal synthesis of Ce-impregnated zeolite displayed satisfactory results compared to other reported electrodes. Deposition of the metal was achieved at a potential of −1.2 V (vs. Ag/AgCl) for 120 s followed by a square wave stripping scan from −1.6–0.0 V. Various experimental conditions which include nature of supporting electrolyte, pH, amplitude, frequency, deposition potential and deposition time were optimized prior to the analyses. The fabricated electrode revealed a linear behavior over the metal ion concentrations with a LOD (S/N = 3) of 0.07 ppb and 0.46 ppb for lead and cadmium detection, as well as a good reproducibility (RSD 2.23%) respectively. The fabricated electrode has the potential to be used in the analysis of environmental samples due to its lack of toxicity, ease of fabrication and relative inexpensiveness. [ABSTRACT FROM AUTHOR]

In the present study, for the first time the synthesis of magnetic Fe 3 O 4 as core with separate two shells, mordenite (MOR) zeolitic shells and CuO shells, was suggested. The new core-shell (Fe 3 O 4 @MOR@CuO) was prepared in three steps: (i) preparation of iron oxide magnetite core via hydrothermal method with diameter size between 120 and 150 nm, (ii) development of mordenite (MOR) zeolite as first shells on the Fe 3 O 4 cores (Fe 3 O 4 @MOR) by hydrothermal method with thickness between 30 and 50 nm and (iii) coating of second shells from CuO by post-synthesis method with average thickness 215 nm. The properties of prepared magnetic core-shells were characterized by diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption measurement and vibration sample magnetometer (VSM). Based on EDX results, the weight percentage (wt%) of Fe 3 O 4 cores, MOR and CuO shells were calculated 68.13, 28.17 and 3.7%, respectively. The XRD results indicated diffraction peaks for each three compounds in core-shell. The diffuse reflectance spectrum of Fe 3 O 4 @MOR@CuO photocatalyst presented a strong absorption in the 400–800 nm range, indicating the introduction of MOR broadened the visible light absorption ability. The photodecolorization of Fe 3 O 4 @MOR@CuO core-shell was investigated in the absence and presence of H 2 O 2 . The results showed that, zeolitic shells and Fe 3 O 4 enhanced charge separation efficiency compared with that of the pure CuO and Fe 3 O 4 @CuO core-shell in photodegradation of methylene blue (MB) dye. The photocatalyst exhibited an enhanced and stable activity for the degradation of MB under visible light. The mechanism of separation of the photogenerated electrons and holes of the Fe 3 O 4 @MOR@CuO photocatalyst was discussed. [ABSTRACT FROM AUTHOR]

The catalytic transalkylation chemistry encountered with mesitylene interacting with benzene has been revealed working with the acid zeolites, H-mordenite and HY. Preferential adsorption on the active site of the alkyl group containing-aromatic molecule was very advantageous for transalkylation reactions since otherwise the smaller benzene would be the dominant adsorbed molecule; it was also noted that when the alkyl acceptor was a small molecule, formation of the transition state was favourable. The study has shown that transalkylation was favoured over disproportionation at higher temperatures and this was in line with the earlier conclusions that disproportionation would only be effective at low temperatures. Reaction temperature influences the selectivity of alkyl-transfer reactions. The feed composition seemed to play a significant role in transalkylation and its manipulation may result in effective removal of alkyl groups from the alkyl-containing molecule. The window of operation is reduced somewhat by the finding that working at high temperatures is associated with undesirable higher deactivation rates. [ABSTRACT FROM AUTHOR]

The recovery of ammonium (NH 4 +) from aqueous solutions by zeolite is attractive. In this study, the physical-chemistry of NH 4 + adsorption process from aqueous solution by two zeolitic mixtures, either treated or not treated with NaCl, was assessed. Results suggested that the zeolitic mixture richer in mordenite and with high specific surface area adsorbed more NH 4 + than the one richer in clinoptilolite and heulandite showing a lower specific surface area. NaCl treatment increased the amount of NH 4 + adsorbed by the zeolitic mixtures. The higher amount of NH 4 + adsorbed by the zeolitic mixtures treated with NaCl was explained by the low/high density water model accounting for cation exchange among the two kosmotropic systems: Na-enriched zeolitic mixtures and NH 4 +-enriched aqueous solution. The adsorption kinetics were best approximated by the bimodal pseudo-first-order model. The two sorption kinetic constants, k 1 and k 2 were related to the adsorption (mediated by k 1) and the ion exchange (mediated by k 2) processes. The fitting of NH 4 + data to Langmuir-Sips model suggested that the NaCl treatment increased the number of active sites only of the zeolitic mixture with the large amount of mordenite. Thus, it is conceivable that modulation of NaCl treatment of zeolitic mixtures can be applied to obtain new materials for water remediation from NH 4 + contamination. [Display omitted] • Two zeolitic mixtures with different mineralogy were used for NH 4 + recovery. • Zeolitic mixtures showed good performance for NH 4 + removal from solution. • The mineralogical composition of zeolitic mixtures affected NH 4 + adsorption. • The bimodal-pseudo-first order model well described NH 4 + adsorption kinetics. • The Langmuir-Sips model provides the best fit for the NH 4 + adsorption isotherm. [ABSTRACT FROM AUTHOR]

SSZ-39 and mordenite zeolites were obtained from the conversion of zeolite Y in the presence of the same reaction precursors (organic templates, NaOH, water, etc.) under a wide range of reaction conditions. The applied templates were N,N -dialkyl-2,6-dimethyl-piperidinium-OH and -I (alkyl: ethyl or methyl). Curiously, SSZ-39 and mordenite were obtained from hydroxides and iodides, respectively, showing firstly the importance of the anion in the selective crystallization of zeolites. Reactions were also performed at the same set of pH values (achieved by adding small amounts of NaOH to the iodide-based precursors) to investigate the effect of basicity; the results did not vary appreciably with the pH of the synthesis precursors. Based on the phase conversion (MOR – > AEI or ANA with increasing reaction time and pH), the selective formation of SSZ-39 and mordenite from hydroxides and iodides, respectively, could be explained in terms of zeolite-promoting and -preventing anions (hydroxide and iodide, respectively). The phase conversion of zeolites could be explained on the basis of the maximum pore size of zeolites, rather than the framework densities. The obtained zeolites (SSZ-39 and mordenite), in their protonated forms, were employed in ethanol dehydration and direct ethylene-to-propylene conversion, and the results showed that the two zeolites have potential application in acid catalysis. In particular, the SSZ-39 with an AEI structure can be applied in the direct production of propylene from ethylene or ethanol. [ABSTRACT FROM AUTHOR]

The well acid-stable and hydrophilic mordenite membrane is applied as a “membrane extractor reactor” for the esterification of acetic acid and alcohol with the H 2 SO 4 as catalyst. The mordenite membrane reactors are placed into the reaction mixtures and continuously remove water from the esterification mixture by pervaporation, which could greatly improve the alcohol conversions of esterification. Besides, the effects of the reaction conditions (such as temperature, molar ratio of acetic acid/alcohol, and catalyst loading) on the ethanol conversion are investigated in details. As the reactional temperature, the molar ratio of acetic acid/alcohol, the catalyst loading, and the ratio of effective membrane surface area to esterification mixture volume are 85 °C, 1.5, 0.05 wt% (0.005 mol/L), and 0.31 cm 2 /cm 3 , the ethanol and n -butanol conversions of esterifications are up to 98.13% and 98.73%, respectively. Even if the mordenite membrane is applied to pervaporation-esterification for 8 times (96 h), the mordenite membranes are still kept the typical diffraction peaks and morphology by XRD and SEM characterization, and the dehydration performance of the membrane for 90 wt% HAc/H 2 O mixture at 75 °C is almost the same as the as-synthesized mordenite membranes, and the flux and separation factor of the mordenite membrane after 8 times PV-esterification are 0.44 kg m −2 h −1 and 627. [ABSTRACT FROM AUTHOR]

Sustainable industrial processes demand rapid and cost-effective synthesis procedures of zeolites. Herein, we report the synthesis zone of pure mordenite (MOR) zeolite under microwave irradiations. Phase purity, crystallinity, and morphology were carefully studied through optimization of synthesis parameters such as crystallization time, aging time and Si/Al ratio. Without the seeds, the organic-structure directing agent (OSDA)-free synthesis of pure MOR crystals was achieved in the shortest time of 12 h. Moreover, the addition of two different OSDAs, namely o-phenylenediamine (OPDA) and tetramethylammonium hydroxide (TEAOH), decreases the crystallization time up to 6 h with the same gel composition. Whereas, minimum crystallization time through conventional heating was 24 h with an OSDA and 48 h without the template. Rectangular and spherical shaped crystals with low aspect ratio were formed under this condition. The same optimized condition was used with different gel compositions (i.e. Si/Al of 15, 25, 50) to crystallize pure MOR. Also, effect of alkalinity was investigated at different Si/Al ratios. [ABSTRACT FROM AUTHOR]

The external surface of the H-Mordenite (MOR) was modified with lanthanide oxides such as CeO 2 , La 2 O 3 , Pr 2 O 3 , Sm 2 O 3 , Dy 2 O 3 , and Yb 2 O 3 , to investigate the deactivation of external acid sites. It is confirmed that the modification with the oxides prevents the isomerization of 2,6-diisopropylnaphthalene (DIPN) during the isopropylation of naphthalene (NP). The oxides accumulated on the MOR surface deactivated the acid sites with keeping catalytic activities of the isopropylation when their loadings are in the range of 5–10 wt%; however, the differences in the activities were observed when the loading was increased to 20–30 wt%: CeO 2 gave a high activity with a high selectivity for 2,6-DIPN, and Sm 2 O 3 maintained moderate activities, whereas the other oxides lost the activities. The differences of the modified MORs are ascribed to the morphologies of mesopores formed by the accumulation of the oxides. CeO 2 is accumulated as segregated nano-sized crystallites, and the pore-entrances of MOR are opened through their mesopores for the access of NP and its products, and the isopropylation occurs in the channels with a high selectivity for 2,6-DIPN without a significant loss of the activities. However, La 2 O 3 is accumulated as amorphous glassy oxide with a low surface area, leading to the loss of the activities by disturbing the access of NP to MOR pores. Further, amorphous glassy Sm 2 O 3 also supports the selective formation of 2,6-DIPN as the mesopores allow the access of NP to MOR channels. [ABSTRACT FROM AUTHOR]

We report the hydrothermal synthesis of mordenite zeolite in the absence of organic structuring directing agent (OSDA). The mordenite (MOR) zeolite with molar composition 6Na 2 O:Al 2 O 3 :30SiO 2 :780H 2 O was characterized by XRD, SEM, EDX, and NMR. It was further impregnated with lanthanum and was used in the construction of zeolite modified carbon paste electrode by mixing with different amounts of graphite and paraffin oil to form a paste. The paste composite with the ratio 65:5:30 (graphite:zeolite:paraffin) displayed the best electrochemical behavior in the cyclic voltammetry of K 4 Fe(CN) 6 and was hence used for the detection of Cd (II) ions. [ABSTRACT FROM AUTHOR]

SiO 2 /Al 2 O 3 ratio (SAR) is one of the most important parameters for zeolite materials, and tuning of SAR towards required topology is crucial for applications of zeolites. Mordenite (MOR) zeolites normally possess the moderate SARs of about 4–32. In this work, a breakthrough for straightforward synthesis of high-silica MOR zeolites was achieved without using seed or fluoride additive, attaining well crystallized MOR with wide window of SARs in the range of 11–263, in which the ultrahigh SAR of 263 represented the highest value for MOR up to date. The synthesis relied on the gel preparation by acidic hydrolysis of the silica precursor with the ionic liquid (IL), 1-butyl-3-methylimidazolium bromide ([BMIm]Br), as the structure-direct-agent, followed by dry-gel-conversion (DGC). Besides mordenite, ZSM-5 could be also obtained from this route. Thermal stability tests demonstrated that the obtained ultrahigh-silica MOR zeolites preserved the crystalline structure up to 800 °C, and the higher SAR, the better thermal stability. Our synthesis largely expands the SAR range of MOR zeolites and provides a series of highly thermal stable high-silica MOR zeolites as promising catalyst supports. [ABSTRACT FROM AUTHOR]

Samples of mordenites with variable Si/Al atomic ratio and different counter-ions were exchanged with copper ions by two methods – the conventional treatment in water solution and by microwave-assisted procedure. The zeolite-solution ratio and the concentration of solution were kept equal for both procedures. We report on the results of XRD, TGA and XPS studies. The XPS analysis confirms that despite observed differences in the spectra of the samples the copper ions are in the +2 oxidation state. The preparation method influences copper and water content and copper surrounding, but does not change the electronic state of copper ions. [ABSTRACT FROM AUTHOR]

The incorporation of lanthanum by ion exchange into InHMordenite was studied in order to investigate the modification of the physicochemical properties of the InHM catalysts. The prepared solids, LaInHM and InHM, were treated under rigorous reaction conditions, i.e. 25 h of TOS with addition of 10% of water and 500 °C. The structural changes of the catalysts were followed by spectroscopic, volumetric and microscopic studies. The presence of lanthanum in the InHM acts like a protection for the zeolite structure avoiding the formation of EFAl species, but the alteration of the indium environment into the matrix leads to a reduction of the catalytic yield of the InHM catalyst. In fact the XPS results revealed that the concentration of the indium active sites (InO) + in LaInHM is lower than in the InHM catalyst, while the remaining indium species interact strongly with Lanthanum. After the reaction, a decrease of In active site in the LaInHM catalyst was observed, suggesting a closer interaction In–La which was later corroborated by TEM microscopy. On the other hand, a steric factor between the side channels of the mordenite and the hydrated cation of La during the exchange process locates lanthanum in outer position, with the consequent loss of pore volume and area specific. The lanthanum exchanged ions protect the deactivation process by structure collapse, but negatively affect the activity of the InHM catalyst. [ABSTRACT FROM AUTHOR]

Methylene-bridged mordenite zeolite with highly-conserved framework carbon is successfully prepared by an improved DGC route for the first time, which is facile, controllable, and efficient. By the improved DGC method, the C content reserved in the framework of the hybrid materials is calculated to be from 88.4 to 99.2 wt%, much higher than those synthesized by conventional hydrothermal (<32 wt%) and conventional DGC (<59 wt%) methods, indicating that only a little amount of Si–CH 2 –Si linkage cleaved during the crystallization under relative low H 2 O vapour pressure. Compared with the conventional DGC route and hydrothermal synthesis method, the improved DGC route has obvious advantages, inclusive of highly-conserved organic framework carbon, highly-efficient usage of autoclaves, highly-efficient usage of chemical sources, saving of energy and low pressure. Moreover, the high competitive adsorptivity for organics and water over the hybrid materials is studied. The new crystallization methodology is instructive for the preparation and application of other organic–inorganic hybrid zeolite analogues. [ABSTRACT FROM AUTHOR]

Desilication of mordenite crystals previously enriched in silica by dealumination has been investigated in order to better understand the process of mesopore formation. Pentene oligomerization in the liquid phase in the presence of an alkane solvent has been used to evaluate the catalytic activity of the desilicated zeolite. Relevant physico-chemical characteristics such as texture, porosity, acidity and composition of zeolite samples desilicated at 80 °C in NaOH solutions at different base concentrations were analyzed quantitatively. The generation of mesoporosity is due to the hydrolysis and dissolution of the surface of the crystals, probably initiated by the formation of etch pits at low coordination atoms, followed by surface roughening, formation and growth of internal mesopores, fragmentation and, ultimately, by a complete dissolution of the crystal. Such a process which is similar to the one involved in the chemical weathering of rocks, results in a severe loss of crystalline material and of the strong acidity associated to it. The oligomerization catalyst prepared from desilicated mesoporous mordenite proved highly stable and selective for the production of C 15 –C 30 oligomers from pentene. [ABSTRACT FROM AUTHOR]

Mordenite nanocrystal-layered membranes consisting of a mordenite nanocrystal layer and protection layer were successfully prepared. The obtained mordenite membranes were applied to the separation of water from water/organic solutions (organic solvents: ethanol, acetone, iso-propanol, or acetic acid) using a pervaporation method at temperatures from 60 to 100 °C. Water permeance through the mordenite membrane in each water/organic solution system was almost identical regardless of organic solvent types in the feed solution. In contrast, the permeance of the organic molecules depended on their polarities. The pre-aging temperature of the mother liquid and the heating rate for formation of the protection layer affected the secondary growth process that formed the protection layer, leading to different morphologies and sizes of the crystals in the protection layer. Water flux increased with decreasing crystal size in the protection layer because the number of non-zeolitic pores among the mordenite crystal increased as the crystal size decreased. [ABSTRACT FROM AUTHOR]

Mordenite was synthesized from diatomite in a template-free system. The crystallization behavior and changes of medium-range structure during the crystallization were studied by X-ray diffraction, scanning electron micrograph, vibrational spectroscopy and high-energy X-ray diffraction. It is indicated that major 4-membered rings are formed at a stage later than that of 5-membered ring in the course of crystallization. Diatomite has also been demonstrated to consist of 5-membered rings and various rings lager than 5-membered ring. A formation pathway for mordenite from diatomite could be proposed that 5-membered rings formed initially are undergoing accommodation of 4-membered rings around them to form mordenite. [ABSTRACT FROM AUTHOR]

The selective capture of radiological iodine ( 129 I) is a persistent concern for safe nuclear energy. In nuclear fuel reprocessing scenarios, the gas streams to be treated are extremely complex, containing several distinct iodine-containing molecules amongst a large variety of other species. Silver-containing mordenite (MOR) is a longstanding benchmark for radioiodine capture, reacting with molecular iodine (I 2 ) to form AgI. However the mechanisms for organoiodine capture is not well understood. Here we investigate the capture of methyl iodide from complex mixed gas streams by combining chemical analysis of the effluent gas stream with in depth characterization of the recovered sorbent. Tools applied include infrared spectroscopy, thermogravimetric analysis with mass spectrometry, micro X-ray fluorescence, powder X-ray diffraction analysis, and pair distribution function analysis. The MOR zeolite catalyzes decomposition of the methyl iodide through formation of surface methoxy species (SMS), which subsequently reacts with water in the mixed gas stream to form methanol, and with methanol to form dimethyl ether, which are both detected downstream in the effluent. The liberated iodine reacts with Ag in the MOR pore to the form subnanometer AgI clusters, smaller than the MOR pores, suggesting that the iodine is both physically and chemically confined within the zeolite. [ABSTRACT FROM AUTHOR]

We present detailed ONIOM(ωB97X-D:PM6) calculations for the formation mechanism of novel composites combining protonic mordenites (H-MOR) with various ionic liquids: 1,3-dimethyl-imidazolium chloride [MMIm]Cl, 1-ethyl-3-methyl-imidazolium chloride [EMIm]Cl; 1-methyl-3-propyl-imidazolium chloride [PMIm]Cl; 1-butyl-3-methyl-imidazolium chloride [BMIm]Cl, 1-(2-hydroxyethyl)-3-methyl-imidazolium chloride [HEMIm]Cl, 1,3-dimethyl-1,3,2-diazasilolium chloride [MMSiN]Cl, and 1,3-dimethyl-1,3-diphospholium chloride [MMPP]Cl. The most feasible [M]-MOR formation mechanism ([M]+ = [MMIm]+, [EMIm]+, [PMIm]+, [BMIm]+, [HEMIm]+, [MMSiN]+ [MMPP]+) involves an ion exchange at the T4O10 position favoring the isolation of a minimal number of [M]+ isomers (i.e., conformational traps). The interaction of these [M]-MOR composites with pollutant gases has afterward been evaluated. Among the studied sytems, [EMIm]-MOR and [HEMIm]-MOR present electronic and steric conditions for potential applications in gas separation, capture, and storage (H 2 and H 2 S). The H-MOR framework exhibits two structural conformers with the [HEMIm]+ cation in the confined space. Both, the MOR-T4O10-[HEMIm] and MOR-T4O10-[HEMIm] HB conformers, interconvert by a dynamic equilibrium with a transition state MOR-T4O10-TS1 acting as a conformational switch (▪-▪) that selectively recognizes and captures H 2 S through a plier-like conformation. [Display omitted] • In silico design of novel composites combining Ionic Liquids with mordenite (MOR) was examined. • A composites formation mechanism that involves the ion exchange of H+ by Imidazolium-based Ionic Liquid cation on T4O10 position in H-MOR. • The existence of conformational traps within the mordenite framework was demonstrated. • A new molecular H 2 S recognition/capture mechanism using [HEMIm]-MOR composite was proposed. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sequential steaming-acid leaching-alkaline treatment on Al-rich mordenite. [•] Intra-crystalline mesopores are introduced by this sequential method. [•] Elevated steaming temperature enhances the final mesoporosity. [•] An extraction-realumination is observed for Al sites with Si(2Al) configuration. [ABSTRACT FROM AUTHOR]

Highlights: [•] Natural mordenite with a Pt/Al2O3 bed formed a membrane reactor for ethane dehydrogenation. [•] H2 selectively extracted achieving an equilibrium shift at 500–550°C. [•] Ethylene yield enhancement of ∼17% was achieved at 500°C. [•] Membrane reactor experiments at 550°C yielded even higher enrichment. [ABSTRACT FROM AUTHOR]

Highlights: [•] Silver-exchanged mordenite with antifungal activity. [•] Growth inhibition of yeasts and moulds. [•] Release of ions with a higher activity than free ions in solution. [•] Growth control of fungi considered as contaminants in the food industry. [Copyright &y& Elsevier]

Low valence bismuth cationic centers were introduced into hydrogen forms of ZSM-5 and mordenite zeolites via impregnation of zeolites in aqueous solution of bismuth salts and subsequent reductive solid state ion exchange (SSIE). It has been found that Near IR photoluminescent bismuth monocations Bi+ and cluster ions are formed in the exchange positions and their optical properties in ZSM-5 and mordenite depend mainly on a zeolite Si/Al ratio and, to a lesser extent, on the amount of loaded bismuth. The photoluminescence emission and excitation spectra of bismuth cationic species (monocations or clusters) are markedly different in ZSM-5 and mordenite. This difference can be explained, taking into the account, that extraframework (exchanged) cations in mordenite zeolite, unlike ZSM-5, can occupy only several distinct positions relative to the mordenite framework structure. [Display omitted] • Low valence bismuth cations were introduced into zeolites via the reductive SSIE. • NIR photoluminescence was observed from bismuth exchanged ZSM-5 and mordenite. • Bi+ and Bi cluster ions cause the photoluminescence of Bi-ZSM-5 and Bi-mordenite. • Formation of bismuth cluster ions is suppressed in the high-silica zeolites. [ABSTRACT FROM AUTHOR]

Highlights: [•] Na-RUB-18 was used as precursor for mordenite. [•] Na-RUB-18 lamella were activated by bonding to aluminum ions. [•] The reaction occurs in 7–14days depending on the Al source. [•] No structure directing agent was added in the reaction mixture. [ABSTRACT FROM AUTHOR]

Highlights: [•] The chemical composition of reactant mixture and reaction time play an important role in mordenite synthesis. [•] Highly crystallized and pure mordenite could be obtained through conversion of magadiite. [•] The as-synthesized mordenite exhibits well thermal stability. [•] The as-made mordenite is exceptional stability towards strong acid. [Copyright &y& Elsevier]

Abstract: Owing to their acidic nature, sulfonamide antibiotics concentrate in anionic form in water bodies where they can remain unchanged for long periods of time, accounting for great concern for antibiotic-resistance issues. In this study the removal of sulfachloropyridazine (4-amino-N-(6-Cl-3-pyridazinyl)benzene sulfonamide) antibiotic from water by adsorption on a high silica mordenite with channel window dimension comparable to that of the antibiotic, and with a significant concentration of internal silanol groups due to the dealumination process, was investigated. The adsorption of sulfachloropyridazine by mordenite at room temperature was completed within 4h with the maximal amount of adsorbed antibiotic of 15.1% zeolite dry weight. The desorption trials elucidated the irreversibility of the adsorption process. The embedding of sulfachloropyridazine into mordenite channels was confirmed by a combined XRPD and FTIR study. Rietveld structure refinement revealed that the incorporation of sulfachloropyridazine molecules caused changes in the dimension of the zeolite channel systems, when compared to the parent zeolite, and a close vicinity of the heterocycle ring nitrogen to the oxygens of mordenite side pocket. FTIR revealed a strong perturbation of the vibrational modes of both the pyridazinyl ring and mordenite silanol groups upon antibiotic adsorption. When the adsorption was conducted at 65°C, an unfavourable temperature effect was highlighted and, interestingly, sulfachloropyridazine transformed with 100% selectivity to 4-amino-N-(6-hydroxyl-3-pyridazinyl)benzene sulfonamide. A nucleophilic aromatic substitution (SNAr) mechanism was suggested for the formation of the reaction product. It is proposed that the H-bond between mordenite silanol groups and pyridazine nitrogen atom, clearly detected by FTIR, stabilize in the ring partial positive charges favouring the displacement of the chloride leaving group. [Copyright &y& Elsevier]

Abstract: A Na–mordenite membrane was prepared by using sol–gel synthesis protocol, and spin-coating was chosen as the impregnation methodology. The gel was impregnated onto commercial ceramic tubular support (α-alumina) and surface characterizations were carried out on Na–mordenite powder prepared with the same gel. The Na–mordenite surface charge is not appreciably modified by a contact with monovalent or divalent salts. The average pore diameter was estimated in the range of 8nm. Previous results showed that monovalent salts were not retained by the stabilized Na–mordenite membrane while after an alkaline treatment, rejections were observed according to the order of hydration energies (NaF>NaCl>NaBr>NaI). After an acid cleaning, the membrane recovered its initial properties. A new estimation of average pore radius proved that steric effects were not responsible for rejection themselves. A new filtration test of mixed monovalent salt solution was carried out. Fluoride ions were retained by a majority while the others were almost not retained. Infrared characterizations indicate that, after an alkaline treatment, surface chemistry modifications may be at the origin of these interactions. Especially, the apparition of an ultrapolar layer all over the Na–mordenite surface greatly modifies Van der Waals interactions between the hydrated anions and the Na–mordenite surface. [Copyright &y& Elsevier]

Abstract: Hydroisomerization of n-hexane, n-octane and n-hexadecane has been studied over Pt-containing micro/mesoporous materials obtained by mordenite (MOR) recrystallization in alkaline solution in the presence of cethyltrimethylammonium bromide. The degree of recrystallization was controlled by varying the concentration of NaOH. Micro/mesoporous nanocomposites MOR/MCM-41 with intermediate degree of recrystallization showed remarkably high activity and selectivity in hydroisomerization of n-octane and high selectivity in hydroisomerization of n-hexadecane. The effect is due to high accessibility of the active sites, improved transport of bulky molecules provided by mesopores and optimal size of Pt particles located in mesopores. [Copyright &y& Elsevier]

Abstract: The addition of Pd improves the catalytic performance of InH mordenite for the SCR of NO with methane, but this effect depends on the In/Al ratio. We studied two PdInMordenite samples, one with In/Al=1/3 (PdInHM(1/3)) and the other with In/Al=1/6 (PdInHM(1/6)). While in the former the presence of Pd in the InHM(1/3) catalyst increased the activity, in the sample with lower In content this effect was not observed. In order to explain these observations, the catalysts were characterized with several techniques. TPR results showed that the presence of palladium shifted the reduction peak of the solid PdInHM(1/3) towards higher temperatures, while on solid PdInHM(1/6), the shift was negligible. This effect could be ascribed to a higher Pd-In interaction in the PdInHM(1/3) catalyst. FTIR of CO adsorbed showed the presence of Pd2+, Pd+ and Pd0 adsorption sites in the calcined PdInHM(1/3). However, in the case of PdInHM(1/6), there was no evidence of Pd2+ species. The TEM images of used PdInHM(1/3) catalysts suggested the mobilization of indium to inner positions into the matrix, thus increasing the interactions with Pd. In the fresh PdInHM(1/6) the indium particles could not be detected but after reaction some agglomeration of particles could be observed, which is in agreement with CO-FTIR and XPS results. In brief, the results indicate that in the PdInHM(1/3) catalyst, Pd and In interact closely, giving place to a promotional effect of Pd, which prevents the agglomeration of In species. [Copyright &y& Elsevier]

Abstract: High-performance mordenite membranes were prepared in fluoride media on porous tubular mullite supports by a single hydrothermal synthesis. Mordenite membranes and powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), magic-angle spinning nuclear magnetic resonance (MAS NMR) and contact angle with water droplets. The microstructure (i.e. hydrophilicity and crystal morphology) and pervaporation (PV) performance were influenced by the fluoride source and synthesis temperature. The 19F MAS NMR evidence shows the fluorine anion is present in channels of the mordenite crystal as a counterion of cations. Eight mordenite membranes (M-3 serial) prepared using NH4F-modified gels exhibited high fluxes of 1.50±0.25kgm−2 h−1 together with high separation factors of 1380±110 for a water/ethanol (10/90wt.%) mixture at 75°C. The membranes also displayed good water-selective for the water/i-propanol mixture. The high performance is attributed to the thin zeolite layer and good surface hydrophilicity of mordenite membranes prepared in fluoride media. [Copyright &y& Elsevier]