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Furfural is a platform molecule that can be catalytically converted using a cascade series of reactions into levulinic esters, essential compounds used as fuel additives. Bifunctional catalysts containing Lewis and Brønsted acid sites such as zeolites are commonly used for these conversions. However, microporous zeolites often present diffusional restriction due to the size similarity of furfural and other molecules to the zeolites' micropores. Thus, incorporating mesopores in these materials through post-synthetic protocols is a promising pathway to circumventing these limitations. This study presents the creation of hierarchical beta and mordenite using Si or Al removal and their employment in the furfural conversion to isopropyl levulinate (PL). Mordenite zeolite did not produce satisfactory mesopores, while the beta was more efficient in generating them by both acid and alkaline treatments. Beta zeolite treated in an alkaline solution presented larger mesopores (14.9 and 34.0 nm), maintaining a total acidity value close to its parent zeolite and a higher Lewis/Brønsted ratio. The combination of these features led to an improved diffusion of bulkier products and the highest furfural conversion (94%) and PL selectivity (90%), suggesting that a post-modification of beta zeolites produced efficient catalysts for upgrading abundantly available furfural. [ABSTRACT FROM AUTHOR]

The silanol groups present on the surface of lamellar silicates are excellent reaction sites for a varied number of chemical modifications. The conversion of these solids into zeolitic structures has shown to be an interesting synthetic alternative, once avoiding hard templating methods and producing materials with particular characteristics. In this work, a post-synthesis OSDA-free procedure was employed for the 2D–3D transformation of Na-RUB-18 lamellar silicate into mordenite zeolite. The conversion was performed at 140 °C and produced small zeolitic crystals (300–500 nm) after 12 and 24 h of crystallization. The reaction presented 65% yield (mol/mol SiO 2), producing materials with a similar Si/Al molar ratio (around 6). The 27Al MAS NMR spectra showed signals related to tetrahedrally coordinated aluminum. The N 2 adsorption/desorption isotherms confirmed the solids microporous nature and volume (0.36 and 0.43 cm3 g−1). The number of acidic sites was determined by NH 3 -TPD (976 and 848 µmol g−1), which also revealed sites with weak and moderate to strong acidity. Finally, the samples' catalytic activity was evaluated by the ethanol dehydration reaction performed at low temperature (150 °C). The synthesized materials were compared to a commercial sample and all the catalysts showed ethanol conversion around 70%, producing ethene and diethyl ether; the latter being the major product at the employed temperature. Unlike the commercial sample, the synthesized ones did not present any deactivation during the time on stream. This feature was attributed to their low-defect structure and subtle mesoporosity. [Display omitted] • Na-RUB-18 was used as precursor in OSDA-free hydrothermal conversion to MOR zeolite. • Small MOR crystals were obtained in high yield after 12 and 24 h of crystallization. • Low temperature ethanol dehydration reaction was performed over the MOR catalysts. • The synthesized MOR was twice as active as the commercial one in ethene production. • The low-defect/mesoporous structure was the key for superior catalytic activities. [ABSTRACT FROM AUTHOR]

There is increasing interest in kinetic models of catalytic refining processes, because of their importance in developing and improving these processes. In fact, the models can be used to predict process performance parameters and to determine the optimum operating conditions. In this work, a detailed reaction kinetic model was developed to describe light naphtha isomerisation reactions over different Pt/zeolite catalysts (Pt/mordenite, Pt/ZSM5, and Pt/BETA). The proposed kinetic model included 66 isomerisation, 28 ring opening, 1 olefin saturation, 22 dehydrogenation, and 90 hydrocracking reactions for 52 real light naphtha components graded from methane to n -octane. A power law reaction kinetics was assumed for all reactions, and 414 kinetic parameters were fine-tuned by comparing the predictions of the model with the results of light naphtha isomerisation experiments at six different temperatures (290, 310, 330, 350, 370, and 390 °C). The Matlab software (version 2015a) was used to perform all the calculations in the current study, and the optimum set of kinetic parameters was estimated using genetic algorithm optimisation. The mean absolute errors for all component compositions at different temperatures were found to be 0.003608, 0.004841, and 0.004757 for the Pt/mordenite, Pt/ZSM5, and Pt/BETA catalysts, respectively. The values of the mean absolute errors estimated from the comparison between the experimental and predicted results showed a very good agreement between the model predictions and the experimental data. [ABSTRACT FROM AUTHOR]

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Cuban and Mexican zeolites are of particular interest from economic outlook because of their exceptional properties and abundance. Here, we present the results of the comparative study of the elemental, structural, morphological, thermal and textural properties of natural zeolites: clinoptilolite, mordenite and erionite from various deposits. Despite a complex phase and element compositions of the studied materials, some general features were detected. The observed dehydration steps are related to water desorption from porosity of different size ranges: mesopores, main and small zeolite voids. This dehydration pattern interferes with the exchangeable cation composition that also affects the general trends. Thermochemical properties of samples are influenced by the geographical location of the deposits. Depending on the origin of the sample, the dehydration enthalpy varies in quite a wide range, which is a function of both zeolite framework structure and exchangeable cation composition. The study of meso- and macropore systems reveals that all the samples exhibit multimodal pore size distribution and possess significant amounts of mesoporosity and even macroporosity. Among the studied samples, the mordenite from Palmarito de Cauto, the clinoptilolite from Etla and the erionite from Agua Prieta (Sonora) have a significant number of pores with average size of about 3 nm. All the samples, except erionite from Agua Prieta, show macroporosity with rather well-defined pore size between 0.3 and 2 μm. The porosity over mass does not change noticeably from one sample to other and varies from 0.32 to 0.65 cm3 g−1. [ABSTRACT FROM AUTHOR]

Two samples of protonated mordenite with close nominal molar ratios (MRs) SiO2/Al2O3 equal to 15.0 and 15.2 are studied by various physicochemical methods. Both samples have the mordenite crystal structure but different morphologies and exhibit different dehydration patterns. According to the 1H, 27Al, 29Si NMR data, these samples show different local structural features, e.g. relative coordination of Si and Al containing tetrahedra. The complex analysis of 1H NMR spectra of hydrated and partially dehydrated samples and IR spectroscopy data shows that acid sites in both samples are mainly bridging OH groups and that the charge in H-MOR-15.0 prepared from the ammonia form is neutralized (in addition to the hydroxyl groups) by residual ammonium ions, while the charge in H-MOR-15.2 prepared by acid etching is additionally neutralized by mobile H+ and/or H3O+ cations. [ABSTRACT FROM AUTHOR]

Zeolites have been successfully applied as catalysts in the pyrolysis of plastics to obtain valuable lower molecular weight hydrocarbon compounds. In the present work, mordenite was directly synthesized and chemically modified from commercial mordenite to increase pore volume. For the first time, the performance of these mordenites was compared with that of an alkali-treated ZSM-5 as catalysts for assisting the pyrolysis of simulated urban plastic waste. The investigated zeolites were: (i) as-supplied synthetic ZSM-5 (ZSM-5/AS); (ii) 0.2 M NaOH treated ZSM-5 (ZSM-5/02); (iii) as-supplied mordenite (MOR/AS); (iv) 0.2 M NaOH treated mordenite (MOR/02); and (v) synthetic lab-developed mordenite (MOR/SD). The modified and synthesized zeolites were individually applied as catalysts in the 700 °C pyrolyzes of combined polyethylene, polypropylene, and polystyrene wastes in a mixture simulating most plastics found in Rio de Janeiro (Brazil) city garbage composition. X-ray diffraction revealed crystallite sizes of all zeolites in a nanometric range from 17 to 43 nm. Textural analysis disclosed the alkali-treated ZSM-5/02 with a superior external surface area, 153 m²/g, and mesopore volume equal to 0.253 cm3/g. Lower values were obtained by MOR/02 (39 m²/g and 0.072 cm3/g). The pyrolysis of the plastic mixture with ZSM-5/02 presented a lower initial degradation temperature, 387 °C, followed by MOR/02, with 417 °C. The ZSM-5/02 catalyst obtained the highest conversion in the pyrolysis of the plastic mixture, totaling 49.2%. However, pyrolysis assisted by the MOR/02 catalyst showed the largest fraction (81.5%) of light hydrocarbons. [ABSTRACT FROM AUTHOR]

Exploring advanced catalysts and reaction systems operated at mild reaction conditions is crucial for conducting the direct methane oxidation reaction toward oxygenate products. Many efforts have been put into research on pentasil−type (MFI) zeolites based on mononuclear and/or binuclear iron sites, using H2O2 as the oxidant. In this work, we present a modified liquid ion−exchange method to better control Fe loading in a mordenite−type (MOR) zeolite with a Si/Al molar ratio of 9. The optimized Fe/MOR catalyst showed excellent performance in the direct methane oxidation reaction with turnover frequencies (TOFs) of 555 h−1 to C1 oxygenates, significantly better than the reported activity. Multiple comparative experiments were conducted to reveal the mechanism behind the performance. Strikingly, the active sites in the Fe/MOR catalyst were found to be mononuclear iron sites, confirmed by transmission electron microscopy (TEM), ultraviolet−visible diffuse reflectance spectroscopy (UV−vis DRS), and X-ray absorption spectroscopy (XAS). Increasing the iron loading led to the aggregation of the iron sites, which tend to trigger undesirable side reactions (i.e., H2O2 decomposition and over−oxidation), resulting in a significant decrease in TOFs to C1 oxygenates. [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]

[Display omitted] • Na-MOR nanozeolite with an average crystal length of 70 nm was synthesized. • This zeolite shows an unprecedented dynamic DAC capacity of 1.58 mmol g−1 at 25 °C. • It also shows 10 times faster CO 2 adsorption kinetics than conventional Na-MOR. Systematic control of the crystal size and morphology of zeolites to enhance their CO 2 adsorption performance is of great importance from both environmental and economic perspectives. Here we report the seeded synthesis of sodium mordenite (Na-MOR) with a Si/Al ratio of 4.9 and an average crystal length and width of 70 and 40 nm, respectively, using γ-aminobutyric acid as a crystal growth inhibitor in the absence of any organic structure-directing agent (OSDA). This nanozeolite shows an unprecedented CO 2 capacity of 1.58 mmol g−1 under dynamic direct air capture (DAC) conditions at 25 °C, which is approximately 40 % greater than the value (1.15 mmol g−1) of the best zeolite adsorbent (an unidentified OSDA-directed Na-MOR (Si/Al = 5.0) zeolite with Na+ enrichment in 8-ring side pockets), mainly due to its nanocrystalline nature. It has also been characterized by much faster CO 2 adsorption kinetics (ca. 5 vs. 50 min equilibration time) compared to a commercial Na-MOR zeolite with Si/Al = 5.0. Our study paves the way for developing a more efficient zeolite-based DAC adsorbent. [ABSTRACT FROM AUTHOR]

The research about modification of mordenite characteristics has been performed by H2C2O4 and/or NaOH treatments and catalytic activity tests in hydrotreating of pyrolyzed a-cellulose. Commercial mordenite (HSZ-604OA) as mordenite control (HM) immersed in 0.05, 0.5, and 1.0 M H2C2O4 at 70 °C for three hours resulting in HM-0.05, HM-0.5, and HM-1. The four mordenites were immersed in 0.1 M NaOH for 15 minutes resulting in BHM, BHM-0.05, BHM-0.5, and BHM-1. The catalysts obtained were analyzed by XRD, SAA, ICP, and acidity test. The catalytic activity of the mordenites was evaluated in hydrotreating of pyrolyzed a-cellulose using stainless steel reactor with an H2 gas flow rate of 20 mL.min−1 at 450 °C for two hours with a catalyst: feed weight ratio of 1:60. The liquid products obtained from the hydrotreating were analyzed using GC-MS. The research results showed that the H2C2O4 and/or NaOH treatment towards the mordenites increased Si/Al ratio and decreased crystallinity. The acidity of mordenites decreased along with the increase of the Si/Al ratio. The average pore diameter of BHM, BHM-0.05, BHM-0.5, and BHM-1 mordenites were 2.898; 3.005; 3.792; 7.429 nm, respectively. The BHM-0.5 mordenite showed the highest catalytic activity in generating liquid product (88.88 wt%) and selectivity toward propanol (4.87 wt%). The BHM-1 mordenite showed catalytic activity in generating liquid product (41.16 wt%) and selectivity toward ethanol (1.21 wt%) and 2-heptyne (4.36 wt%). Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Copper mordenite catalysts are key for methane oxidation to methanol, yet lack sufficient activity. In this paper, noble metal (Au, Ru, Pt and Pd) modified copper ion-exchanged mordenite catalysts were prepared by the ion-exchange method for further improving the methanol yield in the gas-phase continuous catalytic direct partial oxidation of methane to methanol reaction, and the role of noble metal doping on Cu-ex-MOR catalysts was investigated. Experimental results showed that the doping of Ru resulted in a significant increase in the methanol yield of Ru/Cu-ex-MOR catalyst to 157.36 μmol/g cat /h compared to that of Cu-ex-MOR catalyst (12.89 μmol/g cat /h). SEM, XRD, FT-IR, N 2 adsorption-desorption, XPS, NH 3 -TPD and H 2 -TPR results showed that Ru/Cu-ex-MOR had uniformly dispersed Ru elements and the largest number of surface acidic and oxidation sites, which facilitated the adsorption and activation of methane. Additionally, it was found by TEM, in situ FT-IR and DFT characterization that Ru played a role in stabilizing the Cu active sites, the adsorptive activation of water on the Ru site and the H-transfer process reduced the energy required for breaking C–H bond of CH 4 at the Cu active site, which significantly improved the methane activation capacity of the Ru/Cu-ex-MOR catalysts, resulting in higher methanol yields. [Display omitted] • Noble metal-modified Cu MOR catalysts were prepared and used in methane-to-methanol. • The methanol yield increased significantly to 157.36 μmol/g cat /h after Ru doped. • H-transfer process on the Ru site reduced the energy required for breaking C–H bond. • Doped Ru facilitated the adsorption of methane and the polarization of the C–H bond. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mordenite with ammonium exchange were prepared for effective CH 4 /N 2 adsorbents. • CH 4 /N 2 selectivity significant increase on NH 4 -MOR as the ammonium exchange degree increases. • The introduction of the ammonium ion significantly amplifies the disparity in CH 4 and N 2 affinity on NH 4 -MOR. • NH 4 -MOR exhibited excellent CH 4 /N 2 separation performance and stability. Adsorption-based CH 4 /N 2 separation processes are promising and attractive, but remain a challenging task due to the lack of effective adsorbents. In this study, we present a strategy for the straightforward ammonium exchange of low-cost non-polluting sodium-type mordenite (MOR), obtaining MOR with varying ammonium contents (NH 4 -MOR) and exploring their effects on the CH 4 /N 2 separation performance. The results showed that the CH 4 /N 2 selectivity significant increase on NH 4 -MOR as the ammonium exchange degree increases. In particular, NH 4 -MOR-95 % exhibits a selectivity of CH 4 /N 2 up to 4.6, far exceeding that of the pristine Na-MOR (1.9), while also maintaining a high level of CH 4 adsorption (16.8 cm3/g) at 25 °C and 1 bar. The simulation results demonstrate that the introduction of ammonium ion significantly enhances the disparity in CH 4 and N 2 affinity on NH 4 -MOR. The breakthrough experiments confirmed that NH 4 -MOR has outstanding CH 4 /N 2 separation ability. Furthermore, it was demonstrated that this exceptional separation properties of NH 4 -MOR are maintained at a high level even with an increased activation temperature. This fully validates the effectiveness of the ion exchange strategy and the potential applications of mordenite in the efficient CH 4 /N 2 separation in the industry, where it was previously underutilized. [ABSTRACT FROM AUTHOR]

• Order of ion exchange affects the electronic state of Cu in Cu-Zn-Mordenite. • Cu is characterized with a higher affinity to mordenite compared to Zn. • UV–Vis in situ revealed the presence of O-Zn-O-Cu-O species in Cu-Zn-mordenite. This work evaluated the effect of Zn on the electronic state of copper in the Cu-Zn-mordenite binary system. The samples were prepared in two stages by sequential ion exchange of the initial sodium mordenite, using aqueous solutions of sulfate salts of these two metals, and changing the order of introduction of each of the cations, first Cu2+ and then Zn2+, or in the inverse order. The content of Zn and Cu changed within the 0.02–3.14 wt% interval at various Zn/Cu ratios. The prepared samples were characterized with UV–Vis spectroscopy in situ during temperature-programed oxidation (TPO) in oxygen, temperature-programed reduction (TPR) in hydrogen, and temperature-programed adsorption and desorption of NO (TPD). Cu and Zn have different affinities to mordenite, resulting in competition between them for zeolites sites, their redistribution, and formation of bimetallic Cu-O-Zn species. The order of ion-exchange makes it possible to modify the nature and the relative content of these metal species. Electronic properties of the resulting copper species strongly depend on both the Zn/Cu ratio and the order of exchange of metal ions. The knowledge we have obtained will be useful for designing of new effective catalysts based on copper-exchanged zeolites. [Display omitted] [ABSTRACT FROM AUTHOR]

Dimethyl ether (DME) carbonylation is an important intermediate step in the synthesis of methyl acetate (MA) and ethanol. H-form mordenite (MOR) can efficiently catalyze the reaction, in which Brønsted acid sites (BASs) associated with framework Al function as active sites. But the role of other Al species such as exteraframework Al (EFAl) and framework-associated Al still remains unknown. In this study, we have proposed two convenient approaches for controlling the two Al species and investigating their influence on the DME carbonylation reaction. NH 3 -TPD and Py-IR analyses revealed that the number of BASs increased after the removal of EFAl and the inhibition the formation of framework-associated Al. The reactivity results showed that the elimination of EFAl promoted the DME conversion from 28% to 46%. Additionally, through the implementation of in-situ calcination to impede the presence of framework-associated Al, the DME conversion increased from 28% to 50%. With the understanding that both EFAl and framework-associated Al have a detrimental effect on the reaction, the highest conversion is achieved with these two treatments, leading to 73% DME conversion with 99% selectivity to MA. Our findings provide a systematical strategy to effectively regulate the presence of Al species in zeolite, offering insights of rational design to optimize zeolite catalysts for important industrialized process. [Display omitted] • Post-treatment with EDTA-2Na successfully removed the extraframework Al of MOR. • In-situ calcination prevented the formation of framework-associated Al species. • Extraframework Al covers the BASs resulting in a reduction of the active sites. • The generation of framework-associated Al leads to a decrease in BASs in 8-MR and therefore reduces the DME conversion. • The increased Brønsted acidity in 8-MR upon the two treatments boosted the carbonylation activity. [ABSTRACT FROM AUTHOR]

Wet torrefaction (WT) proves to be a highly efficient pretreatment method for biomass waste, resulting in the production of hydrochar and valuable liquid products. In this study, a groundbreaking chemocatalytic approach is introduced, employing various zeolite catalysts (H-ZSM-5, H-Beta, H–Y, H-USY, and H-Mordenite) in a batch reactor under a nitrogen atmosphere. This method enables the simultaneous one-pot production of levulinic acid (LA) and/or bio-ethanol during the WT process of wood cellulose pulp residue (WCPR), ultimately yielding high-quality solid fuel. The WT process involves at 220 and 260 °C, H 2 O/WCPR = 10, and torrefaction time at 15, 30 and 60 min. The study identifies that at 220 °C and 15 min, as the optimal temperature and time, for bio-ethanol production, achieving a selectivity of 59.0 % with the H–Y catalyst, while the highest amount of bio-ethanol (75.6 %) was detected in presence of H-USY zeolite at 260 °C after 60 min. In addition, it was found the formation of relatively high amount of LA (62.0 %) at 220 °C after 60 min but using the H-ZSM-5 catalyst. For the WT + Mordenite sample (220 °C, 60 min), the highest carbon content of 71.5 % is achieved, resulting in the higher heating value (HHV) of 27.3 MJ/kg, an enhancement factor of 1.36, and carbon enrichment of 1.48, with the sequence of element removal during WT prioritized as DO > DH > DC and the weight loss of 68 %. Finally, the reaction mechanism was proposed to elucidate the formation of liquid products after WT of WCPR with participation of zeolite catalysts. The main pathway involving the direct conversion of cellulose into hydroxyacetone, followed by the subsequent generation of ethanol through the C–C cleavage of hydroxyacetone while LA formed via well-known route which includes cellulose hydrolysis to form glucose, conversion to 5-HMF and the subsequent transformation of 5-HMF into LA. [Display omitted] [ABSTRACT FROM AUTHOR]

• Mordenite zeolite is crystallized using bamboo leaves silica ash for the first time. • Three distinct morphologies are observed from parametric crystallization study. • The zeolite morphology affects the hierarchical micro/mesoporosity and surface acidity. • The modernite catalyst is active in acetalization of benzaldehye and glycerol. • 80.2 % of glycerol is converted to dioxolane and dioxane products at 180 °C for 10 min. Bamboo leaves ash (BLA) is a cheap and sustainable silica source but under-utilized. In this work, mordenite zeolites with various morphologies synthesized from BLA are reported. Our strategy involves merely mixing of silicate and aluminate solutions where parametric crystallization study successfully captured three mordenite synthesis recipes. The prepared solids are then characterized with XRD, SEM, XRF, FTIR, TGA/DTG, N 2 sorption and TPD-NH 3 before their catalytic behavior is tested in acetalization. Mordenites with three distinct shapes (nanostick, intergrown bulky ball, nanorod) are successfully synthesized via parametric crystallization study. Some mordenite zeolites contain hierarchical micro/mesoporosity which is beneficial in acetalization of benzaldehye and glycerol. The nanorod-like mordenite is the best catalyst (80.2 ± 2.4 % conversion, 54.4 ± 0.3 % selective towards 2-benzyl-4-hydroxymethyl-1,3-dioxolane) and its catalytic performance is better than those of classical homogeneous and zeolite catalysts with high recyclability. [Display omitted] [ABSTRACT FROM AUTHOR]

The formation and properties of silver and iron nanoscale components in the Ag-Fe bimetallic system deposited on mordenite depend on several parameters during their preparation. Previously, it was shown that an important condition for optimizing nano-center properties in a bimetallic catalyst is to change the order of sequential deposition of components; the order “first Ag+, then Fe2+” was chosen as optimal. In this work, the influence of exact Ag/Fe atomic proportion on the system’s physicochemical properties was studied. This ratio has been confirmed to affect the stoichiometry of the reduction–oxidation processes involving Ag+ and Fe2+, as shown by XRD, DR UV-Vis, XPS, and XAFS data, while HRTEM, SBET and TPD-NH3 show little change. However, it was found the correlation between the occurrence and amount of the Fe3+ ions incorporated into the zeolite’s framework and the experimentally determined catalytic activities towards the model de-NOx reaction along the series of nanomaterials elucidated in this present paper.

Nanocrystalline mordenite (MOR) zeolites were hydrothermally synthesized in a single step with commercial cetyltrimethylammonium (CTA) hydroxide as the sole organic template, while the aluminum source was varied in a typical synthesis gel. CTA can effectively reduce the crystal growth of MOR zeolites, in some cases selectively in the a‐ and b‐directions of the unit cell. These nanocrystalline MOR zeolites do not only have a larger external surface area than their bulk counterparts prepared without CTA, but the Brønsted acid sites in the side‐pockets are also more accessible. The combination of the use of CTA and AlCl3 ⋅ 6H2O afforded the best‐performing catalyst with much improved activity in benzene alkylation and hydroconversion of n‐hexadecane (n‐C16). Modifying MOR synthesis with CTA hydroxide is a cheap and effective method to open up the one‐dimensional micropore system of mordenite, increasing the catalytic performance in hydrocarbon reactions. [ABSTRACT FROM AUTHOR]

This study explored morphological, mineralogical, and physicochemical features of suspected toxic mordenite fibers from Northern Italy. All the mordenite samples (FAS1, GC1, SP1) show similar structural and chemical character, are Na-rich (Na > Ca > K), and the Al content decrease reflects the unit cell volumes in the series: FAS1 > SP1 > GC1. The aerodynamic diameter (Dae) values of the mordenite fibers are 1.19 μm for the GC1 sample, 2.69 μm for FAS1, and 3.91 μm for SP1. All the studied mordenite samples are characterized by "respirable" fibers despite the size differences, which could reach the deeper parts of the lungs. For this reason, fibrous mordenite could represent a potential health hazard and then need to be handled with attention, but further toxicity studies are needed. [ABSTRACT FROM AUTHOR]

Controlling the location of aluminum atoms in a zeolite framework is critical for understanding structure–performance relationships of catalytic reaction systems and tailoring catalyst design. Herein, we report a strategy to preferentially relocate mordenite (MOR) framework Al atoms into the desired T3 sites by low‐pressure SiCl4 treatment (LPST). High‐field 27Al NMR was used to identify the exact location of framework Al for the MOR samples. The results indicate that 73 % of the framework Al atoms were at the T3 sites after LPST under optimal conditions, which leads to controllably generating and intensifying active sites in MOR zeolite for the dimethyl ether (DME) carbonylation reaction with higher methyl acetate (MA) selectivity and much longer lifetime (25 times). Further research reveals that the Al relocation mechanism involves simultaneous extraction, migration, and reinsertion of Al atoms from and into the parent MOR framework. This unique method is potentially applicable to other zeolites to control Al location. [ABSTRACT FROM AUTHOR]

The review analyzes the specific features of methyl acetate synthesis by dimethyl ether carbonylation in the presence of zeolite catalysts. The structural characteristics of zeolites, in particular, mordenite and ferrierite, that affect carbonylation are discussed. The bridging hydroxyl groups (Al–OH–Si) of zeolites function as Brønsted acid sites and interact with dimethyl ether. The carbonylation reaction is characterized by an induction period, during which dimethyl ether molecules interact with Brønsted acid sites to form methoxy groups. The incorporation of CO into the methoxy group leads to the formation of an acetyl intermediate. Methyl acetate is formed due to the interaction between a dimethyl ether molecule and an acetyl intermediate. The reaction is facilitated by the confinement effect characteristic of small zeolite pores, in particular, eight-membered pockets of mordenite. Methyl acetate is synthesized at moderate temperatures (about 200°C) in a CO–dimethyl ether mixture at a high selectivity and a significant dimethyl ether conversion. The occurrence of hydrocarbon formation side reactions, along with the methyl acetate synthesis target reaction, is observed; the side reactions decrease the on-stream stability of the catalyst. In the case of mordenite, these reactions are attributed to the sites present in the twelve-membered channels. The on-stream stability of the catalysts can be increased by using special techniques for neutralizing the deactivating sites of the zeolite. The effect can be achieved by pyridine adsorption or ion exchange of the respective protons of the mordenite structure for organic or metal cations. The introduction of zinc ions and, additionally, copper ions significantly inhibits the activity of the mordenite sites on which the side reactions occur. A new area of research is the use of multifunctional catalysts that mediate methyl acetate synthesis directly from synthesis gas. [ABSTRACT FROM AUTHOR]

The present paper assesses petrographic, mineralogical, chemical, and technological features of different zeolitic tuff samples from various western USA districts of the Basin and Range Province containing mainly erionite, mordenite, clinoptilolite/heulandite and phillipsite. The aim of this characterization is to evaluate the pozzolanic activity of these samples according to European normative UNI-EN 196/5 (Fratini test) to program a possible use as addition for blended cements. Petrographic and mineralogical results show that the two phillipsite-bearing tuffs have a higher theoretical Cation Exchange Capacity (CEC) than the other samples; technological characterization shows a pozzolanic behavior for all the samples but higher for the tuff samples containing phillipsite, which shows a higher reactivity with CaO. All the samples could be thus advantageously employed for the preparation of blended cements, potentially reducing CO2 emissions by 70–90%. [ABSTRACT FROM AUTHOR]

Hydrothermal, solvothermal or ionothermal routes are usually employed for the synthesis of zeolite, which is often accompanied by a high energy consumption, high cost and low efficiency. We have developed a novel route for the rapid and high yield synthesis of mordenite (MOR) zeolite via an ice-templating method. In comparison with traditional hydrothermal synthesis, not only the high yield, but also the superior crystallinity, large reduction in water level and reaction pressure, simple device and conventional silica sources by this route can have great potential for the commercial production of pure MOR zeolite. Moreover, the changed bonding environment of silicon atoms in MOR zeolite, that is, a relative decrease in the tetrahedrally coordinated Si–O–Si bond, and accordingly, an increase in the T–OH (T = Si, Al) groups and Si–O–Al sites, remarkably enhances its acid strength. [ABSTRACT FROM AUTHOR]

Bifunctional catalysts on the basis of Ukrainian natural mordenite-clinoptilolite rocks modified by hydrochloric acid and by witness impregnation with nickel have been synthesized. Samples have been characterized by means of XRD, XRF, FTIR-spectroscopy, low temperature nitrogen adsorption/desorption, DTA/TG, TEM. Catalysts have been tested in micro pulse linear hexane isomerization. Hydrochloric acid treatment of natural zeolite rock leads to silica-to-alumina ratio increasing and raising the BET surface as well as the volumes of mesopores and micropores. The nickel nanoparticles deposited over zeolite crystals have a predominant size of 10 nm, but for some samples smaller ones of 5 nm and bigger ones of 20–50 nm have been found using TEM investigations. Pyridine sorption shows Brønsted and Lewis acidity of the catalysts, moreover the lower hydrochloric acid concentration using leads to practically equal Brønsted and Lewis acidity, the higher acid concentrations causes the Lewis acidity predominance. DTA/TG investigations show that water physically sorbed in the pores of the samples has been removed up to 200 °C from lager cavities of acid-treated catalysts and up to 500 °C from narrower cavities for untreated initial rock. Removing zeolite structure water up to 800 °C causes the dehydroxylation and Brønsted acidity transformation into Lewis acidity. The sample dealuminated by 1 mol dm−3 acid with nickel nanoparticles of 5–8 nm demonstrates the best performance in the isomerization of n-hexane. It is characterized by a 20% yield of hexane isomers at 250 °C and 70% selectivity. [ABSTRACT FROM AUTHOR]

Zeolite is a potential material for use as a catalyst in various catalytic reactions. In this research, green diesel-range hydrocarbons were successfully derived from refined palm oil via a hydrotreating process in a batch-stirred autoclave reactor using activated Indonesian natural zeolite (ANZ) as a catalyst. A series of detailed characterizations, including XRD, XRF, SEM, FTIR, N2 sorption isotherm, and NH3-TPD, were utilized to investigate the physicochemical properties of the catalyst. Herein, the ANZ, dominated by the mordenite phase, was prepared through dealumination and NH4+-exchange, and directly used without calcination that is commonly performed to convert NH4+ into a proton. Moreover, the hydrotreating reaction was carried out at 375°C with a weight ratio of feed to catalyst of 100:1. The catalytic tests showed that C15 alkanes were the most dominant liquid product obtained via the decarbonylation reaction mechanism of refined palm oil. In addition, the highest activity of the ANZ catalyst exhibited up to ~36 wt.% and selectivity up to 70% toward the formation of C15 diesel-range with cetane numbers in the range 71 and 77. [ABSTRACT FROM AUTHOR]

A catalyst was developed in the form of a composite based on a zeolite matrix modified with titanium nanoparticles based on zeolite raw materials from the Kulikovskoe deposit in the Amur Region. Ion-plasma sputtering of a titanium target in a vacuum was used to obtain a composite. The features of the structure and composition of the obtained material were established. It is shown that the zeolite matrix can be enriched with Ti nanoparticles. [ABSTRACT FROM AUTHOR]

Starch-g-poly(acrylic acid)/organo-mordenite (St-g-PAA/OMOR) superabsorbent composites were prepared via inverse suspension polymerizationutilizing potassium persulfate as an initiator and N, N'-methylene bisacrylamide as a crosslinker. Different dosages of cetyltrimethylammonium bromide were used to obtain organo-mordenite (OMOR) samples with different organification degrees. The effects of the organification degree of OMOR on the water absorbency, swelling behavior, and reswelling properties of St-g-PAA/OMOR were studied. The results from both FTIR and XRD analyses indicate that the Si–OH group of OMOR was involved in the formation of the St-g-PAA/OMOR composite. SEM analyses showed that the organification degree of OMOR influenced the morphology of the St-g-PAA/OMOR composite. The water absorption absorbency, swelling rate, and reswelling capability of the St-g-PAA/OMOR composite prepared using the OMOR with the optimal organification degree were superior to those of the St-g-PAA/mordenite composite. The swelling behaviors of the St-g-PAA/OMOR composites, which were measured in distilled water, obeyed Schott's second-order kinetics model. The St-g-PAA/OMOR composite prepared using the OMOR with the 8 wt.% organification degree had the highest water absorption capacity and the highest swelling rate. Moreover, after five swelling–shrinking cycles, the composite retained its excellent water absorption capacity. [ABSTRACT FROM AUTHOR]

It is of great significance to clarify the roles that various seeds play in the induced synthesis of target zeolites from a viewpoint of topological structure. Zeolites, including ZSM-5, β, mordenite, ZSM-35, ZSM-22, SSZ-13, SSZ-24 and analcite, were used as seeds for the template-free synthesis of ZSM-5. It was found that zeolites with lower framework density and identical composite building units (CBUs) and secondary building units (SBUs) could be used as seeds for the successful synthesis of ZSM-5. Zeolites (ZSM-5, β, mordenite, ZSM-35 and ZSM-22) having identical CBUs and SBUs to ZSM-5 were capable of accelerating the crystallization of ZSM-5, whereas zeolites (SSZ-13 and SSZ-24) lacking identical CBUs and SBUs could act as seeds to synthesize ZSM-5 zeolite only if they possessed lower framework density than ZSM-5. As such, zeolites possessing simultaneously identical CBUs and/or SBUs and low framework density had a strong inductive effect in template-free synthesis of ZSM-5. [ABSTRACT FROM AUTHOR]

A series of gas‐phase reactants is used to treat a Cu‐exchanged mordenite zeolite with the aim of studying the influence of the reaction environment on the formation of Cu pairs. The rearrangement of Cu ions to form multimeric sites as a function of their oxidation state was probed by X‐ray absorption spectroscopy (XAS) and also by applying advanced analysis through wavelet transform, a method able to specifically locate Cu–Cu interactions also in the presence of overlapping contributions from other scattering paths. The nature of the Cu‐oxo species formed upon oxidation was further crosschecked by DFT‐assisted fitting of the EXAFS data and by resonant Raman spectroscopy. Altogether, the CuI/CuII speciation clearly correlates with Cu proximity, with metal ion pairs quantitatively forming under an oxidative environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Isolated Cu2+ and [CuOH]+ species were the precursors of Cu sites with high activity for CH 4 activation. • The optimum activity was strongly dependent on the Cu/Al ratio. • The Si/Al ratio of the zeolite framework determined the Cu/Al ratio for higher activity. • The copper active species were identified throughout in situ Diffuse Reflectance spectroscopy (DRS). • DRS revealed different copper actives species and their dynamic behavior with temperature. This work investigates the influences of Cu content, Si/Al ratio, and sample preparation method on the active Cu species in mordenite (MOR). The Cu/MOR prepared by multiple Cu-exchange procedures showed an optimum Cu/Al ratio for the formation of the most active species for methanol formation. XANES spectra indicated that isolated Cu+ species were formed after CH 4 interaction and were re-oxidized under a flow of water steam. The Cu-MOR samples obtained by ion-exchange method presented well-dispersed CuO in the zeolite pores, while samples obtained by impregnation method presented segregated CuO and were inactive for CH 4 activation. The methodology used for in situ UV–vis spectra analyses indicated that different Cu species were active for CH 4 oxidation. Isolated Cu2+ species were not involved in CH 4 activation at temperatures lower than 300 °C. The isolated Cu2+ species were partially hydrolyzed by O 2 treatment and species like [CuOH]+ and [CuO x ] n or polynuclear Cu2+-oxyhydroxide were formed. The formation of polynuclear species in substitution of di-copper would impact the specific activity with the Cu content and decrease the activity for methanol production. [ABSTRACT FROM AUTHOR]

The catalytic activity of Co and Pd loaded on mordenite (MOR) was evaluated in the hydrotreatment of cashew nut shell liquid (CNSL) into biofuel. Metals were loaded into MOR as support via wet impregnation process. The Co content was varied as 2, 4, and 6 wt.% to produce Co(1)/MOR, Co(2)/MOR, Co(3)/MOR catalysts. The micro-mesoporous structure of the catalyst was confirmed by XRD, SEM, TEM, FTIR, and N2 adsorption-desorption measurement. AAS were used to analyze the amount of metal that is successfully loaded in the catalysts. Hydrotreating of the CNSL was conducted in a semi-batch reactor at 450 °C with hydrogen flow (20 mL/min) for 2 h. The liquid product was analyzed using GC-MS. The activity of Co/MOR was compared with the activity of Pd/MOR as a noble metal. The result of the hydrotreatment process showed a decrease of liquid product in the sequence of Co(3)/MOR > Co(2)/MOR > Pd/MOR > Co(1)/MOR > MOR. The Co(3)/MOR catalyst exhibited the highest conversion of liquid hydrocarbon than the others (61.8 wt.%), comprising predominantly by gasoline compounds with over 25.21 wt.% conversion.

Acid-alkaline treatment using acetic acid and sodium hydroxide (NaOH) were applied on mordenite (MOR) to increase the Si/Al ratio and surface area properties. Various time treatment (3, 6, and 9 h) and concentration of acetic acid (6, 9, and 12 M) were used to treat MOR, and followed by the treatment with NaOH (0.1 M) under room temperature. The MOR and treated mordenite were applied as a catalyst for hydrotreatment of cellulose-derived bio-oil. The acetic acid treatment caused the increase of the Si/Al ratio of mordenite up to 27.03. The Si/Al ratio was determined using ICP-AES analysis which was also confirmed using FT-IR analysis. The acidity was determined using NH3 vapors adsorption. The acidity test revealed that as the Si/Al ratio increased the acidity of mordenite decreased. The advantage of using acetic acid for acid treatment was that the XRD patterns of mordenite can be preserved with a little decrease of the intensity. On the other hand, the NaOH treatment under room temperature decreased the crystallinity down to 68%, which was calculated using XRD. The acid-alkaline treatment of mordenite succeeded to increase the surface area 2 times larger than the parent mordenite. The surface area was obtained from BET analysis. The acid-alkaline treated mordenite exhibited better catalytic activity upon hydrotreatment of biomass-derived bio-oil compared to the parent mordenite which corresponded to its highest surface area.

Zn(II)-ZMT material development based on natural zeolite mordenite type (ZMT) as a drug carrier for ibuprofen has been explored and assessed. The ion exchange method was carried out to prepare Zn(II)-ZMT material. XRD, FTIR, and FESEM-EDS were used to characterize the physico-chemical characteristics of all materials. The performance of Zn(II)-ZMT as a drug delivery agent for ibuprofen was also evaluated using drug loading-release, zeta potential measurement, and cytotoxicity testing. Six kinetic models (including the zero-order, first-order, Peppas-Sahlin, Higuchi, Hixson-Crowell, and Korsmeyer-Peppas models) were utilized to simulate the drug release process. Meanwhile, a microtetrazolium (MTT) assay was used to analyze the material's cytotoxicity. The Zn(II)-ZMT material has a drug loading content (DLC) of 90.37 % and an efficiency entrapment content (EEC) of 54.22 %, according to drug loading. The drug releases kinetic modeling of Ibuprofen from Zn(II)-ZMT followed the Hixson-Crowell model. This material exhibits good biocompatibility based on a cytotoxicity test using the MTT assay. Ibu@Zn(II)-ZMT has a zeta potential of − 61.55 mV ± 0.1 mV. These findings suggest that the material in the dispersion system has a high degree of stability, indicating that it will not flocculate or coagulate in the body. Furthermore, Zn(II)-ZMT is an inorganic substance that has the potential to be employed as a medication delivery material in the future.

A comprehensive study of the catalytic properties of the copper-iron binary system supported on mordenite, depending on the iron valence—CuFe2MOR and CuFe3MOR—was carried out, and redox ability has been considered as a decisive factor in determining catalytic efficiency. Acidity was studied by TPD-NH3, DRIFT-OH, and DRT methods. The total acidity of both samples was high. The Brönsted acidity is similar for both bimetallic samples and is explained by the acidity of zeolite; Lewis acidity varies greatly and depends on the exchange cations. A screening DRIFT study of CO and NO has shown redox capacity and demonstrated a potential for using these materials as catalysts for ambient protection. CuFe2MOR demonstrated stable Cu and Fe species, while CuFe3MOR showed redox dynamic species. As expected, CuFe3MOR displayed higher catalytic performance in NO reduction via CO oxidation, because of the easily reduced intermediate NO-complex adsorbed on the metallic Cu and Fe sites, which were observed through in situ DRIFT study.

This study examines the development of geopolymers from clinoptilolite, mordenite, and analcime and compares the properties of the resulting green-binding materials. Sodium silicate and sodium hydroxide solutions were used as activators. Compressive-strength, X-ray diffractometer (XRD), and scanning electron microscopy (SEM/EDX) analysis were employed to characterize the mechanical development, mineralogical composition, and microstructure of the geopolymers. The results show that clinoptilolite, mordenite, and analcime were found to offer much potential for the synthesis of geopolymers. Clinoptilolite-based geopolymer is the most reactive of the three and generates a higher rate of geopolymerization than mordenite- and analcime-based geopolymers. Reactive components other than zeolites are also found to be critical to the geopolymerization reaction. Feldspar provides additional Na for the reaction, reinforcing the gel structure and developing better compressive strength. The difference in the mechanical and microstructural properties of natural zeolite-based geopolymers is attributed to the varying nature and mineralogical content of the starting materials. Different gel characteristics provide valuable information on the role of the active phases involved in the reaction.

The potential use of some cation-exchanged mordenite (H+, Na+, Cu+, and Ag+) as a selective adsorbent for volatile iodine species (ICH3 and I2), which can be released during a nuclear accident together with a steam carrier gas, is investigated using density functional theory. It is found that in the case of Cu-MOR and Ag-MOR, the absolute values of interaction energies of ICH3 and I2 are higher than that of water which indicates that these forms of zeolite could be suitable for selective adsorption of iodine species. In contrast, the H-MOR and Na-MOR are found to be unsuitable for this purpose. A systematic investigation of all adsorption sites allowed us to analyze the structural effects affecting the adsorption behavior. For the Ag-MOR and Cu-MOR zeolites, the iodine compounds are adsorbed preferentially in the large channel of mordenite (main channel) while water prefers the small channel or the side pocket where it forms stronger hydrogen bonds. The factors governing the interaction energies between the cationic sites and the different molecules are analyzed and the important role of van der Waals interactions in these systems is highlighted. [ABSTRACT FROM AUTHOR]

Two Al-rich mordenite samples were prepared by the same synthesis procedure except for the activation of the gel for which classical stirring and ultrasonic pretreatment was used. The organization of Al atoms both in the synthesis gel and zeolite product was investigated. Although both methods of the gel activation resulted in a similar transformation of Al and Si source according to NMR spectroscopy, stirring provided a significantly higher fraction of AlSiAl sequences in the gel compared to the ultrasonic pretreatment. These sequences were transferred to the zeolite product and were more populated in the conventionally prepared mordenite. Al atoms of AlSiAl sequences face different channels and mainly behave as single Al atoms, but they can also form Al pairs or close unpaired Al atoms, observed for the first time for mordenite. [ABSTRACT FROM AUTHOR]

[Display omitted] • CAN and ANA are formed via solution-mediated transformation of natural zeolite. • CAN and ANA synthesis pathways highly depend on the alkalinity of initial solution. • MOR as a Si/Al precursor gives a higher crystalline ANA than traditional synthesis. • A gel alkalinity of 1.124 mmol/L with TPA+ and MOR NZ leads to pure CAN formation. • Adjacent acidic-cationic sites favor acetaldehyde production. In this study, one-pot syntheses of cancrinite (CAN) and analcime (ANA) frameworks from mordenite (MOR) natural zeolite were performed for the first time. The effects of the synthesis gel composition and alkalinity on the phase formation and crystallinity of the product were investigated. All studied zeolites were evaluated for their catalytic activities in ethanol conversion reactions from 473 K to 673 K and at 1 atm. The results suggested that the formation pathways of CAN and ANA are highly dependent on the alkalinity of the synthesis solution and the type of starting material regardless of synthesis template. The use of natural MOR zeolite (MOR NZ) in the synthesis can contribute to highly crystalline ANA structures comparable to the ANA products obtained from fumed silica and sodium aluminate (NaAlO 2). The quantity and locations of the acidic-cationic dual active sites of the proton-form product zeolites are suitable for synthesizing acetaldehyde from ethanol with over 90% product selectivity. However, further development of synthesis procedures to enhance the surface area is needed to improve the ethanol conversion of the resulting zeolites. This work provides a new perspective on highly crystalline and pure-phase zeolitic structural formations from natural zeolite and their potential application in ethanol conversion. [ABSTRACT FROM AUTHOR]

Syngas from biomass gasification is being developed for alternative feedstock in the chemical industry. Palm kernel shell which is generated from palm oil industry can be potentially used as raw material for gasification process. The purpose of this study was to investigate the use of modified natural zeolite catalysts in steam gasification of palm kernel shells. Mordenite type zeolite was modified by acid leaching to be used as a tar cracking catalyst. Steam gasification was conducted at the temperature range of 750–850 °C and the steam to biomass ratio was in the range of 0–2.25. The result showed that steam gasification of palm kernel shell with the addition of zeolite catalyst at 750 °C and steam to biomass ratio 2.25 could reduce tar content up to 98% or became 0.7 g/Nm³. In this study, gasification of palm kernel shells produced syngas with the hydrogen concentration in the range of 52– 64% and H2/CO ratio of 2.7–5.7. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mordenite supported mono, bi, and trimetallic Ni-Cu-Co catalysts were prepared by ion exchange synthesis. • Cryogenic argon isotherms clearly show that divalent metal cations preferentially adsorb at the "side pocket" 8-membered ring channel of mordenite. • Catalysts were tested for acetic acid deoxygenation where activity was strongly correlated to Ni content. • Deoxygenation pathways included gasification, decarboxylation, decarbonylation, hydrodeoxygenation, and ketonization. A series of mono (Ni, Cu, Co), bi (NiCu, NiCo, CuCo), and trimetallic (NiCuCo) mordenite supported catalysts were characterized and evaluated for the continuous, near-atmospheric pressure, thermal deoxygenation of acetic acid. Acetic acid was selected as a model reactant due to its abundance in both biomass pyrolysis upgrading streams and its analogous structure to carboxylic acids found in vegetable oil upgrading streams. Surface area and metal loading were nearly constant for all studied catalysts, allowing an in-depth direct comparison of the metallic activity for reaction pathways including gasification, decarboxylation, decarbonylation, hydrodeoxygenation, and ketonization. In the absence of Ni or in the absence of H 2 , the observed catalytic activity was low. Results from the bimetallic samples at 400 °C highlighted the importance of Ni for H 2 activation and Co for the simultaneous promotion of hydrodeoxygenation and gasification. A nearly linear correlation between the Ni content and the conversion of acetic acid was observed at 400 °C. Cryogenic argon isotherms revealed the location of metal sites within the mordenite pore, further emphasizing the impact of confining environments on the deoxygenation of bio-derived compounds. TGA, TPR, and TPD studies provided information on catalyst stability, reducibility, and acidity, respectively. HRTEM indicated that agglomerates formed under the studied reaction conditions. The fresh Ni/MOR catalyst, under differential conversion conditions, was stable for ~ 24 h at 460 °C, for an additional ~ 20 h upon regeneration at 460 °C, and for an additional 30 h upon regeneration at 500 °C. Long-exposure activity was observed in the Ni/MOR catalyst, favoring hydrodeoxygenation and decarbonylation for at least 70 h under integral conversion conditions. In the bimetallic NiCo/MOR catalyst, Co stabilized Ni active sites in a co-located configuration which promoted hydrodeoxygenation, but also promoted gasification, and eventually lead to coking/lower conversion. [ABSTRACT FROM AUTHOR]

Conventional washing methods release little radioactive cesium fixed in soils. Adding a Cs+ adsorbent to a suspension of Cs-contaminated soil rapidly removes the Cs+ released to the solution, causing more Cs+ release from the soil. We investigated this method by adding a sheet embedded with mordenite powder to a suspension of 133Cs+-retaining wet/dry montmorillonite and water/0.1 mol L−1 KNO3. Adding the sheet increased Cs+ release in all cases, with the highest increase for wet montmorillonite in water. The advantages of this method are the easy removal of the sheet from the suspension and the low Cs concentration in the final solution. [ABSTRACT FROM AUTHOR]

In the present work, various experimental and theoretical methods were combined to study in detail the modifying effect of differences in the order of deposition of components on the state of silver in bimetallic iron–silver samples based on mordenite. In each of the silver-containing samples, the formation of large (≥2 nm in diameter) varieties of silver was observed, which differed from the varieties in the other samples, and in varying degrees. The formation of large Ag NPs on the outer surface of mordenite is explained by the redox interaction of Ag+-Fe2+ and the selectivity of ion exchange. The local surrounding of Ag in the studied samples is different: for AgMOR—monatomic species dominate, FeAgMOR—silver dimers and AgFeMOR—metal particles. In all investigated samples, the partially charged intra-channel Agnδ+ clusters (~0.7 nm in size) were formed due to partial Ag+ reduction and subsequent Ag0 agglomeration into the mordenite channel. Most of the silver in the bulk of the zeolite is represented in the cationic state attached to the mordenite framework by differently coordinated electrostatic forces, which can be Ag-O, Ag-Si or Ag-Al, with variations in interatomic distances and do not depend on the order of metal deposition. In addition, the arrangement of the cations in the side pockets means that the transport channels of mordenite are free, which is favorable for the application of the materials under study in catalysis and adsorption.