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A series of new composites have been synthesized—TiO2 nanoparticles introduced in the interlayer space of layered mordenite. The effect of the hydrolysis medium of titanium tetraethoxide (water or a mixture of water with ethanol) and hydrolysis time (from 6 to 24 h) on the properties and texture of the composite was studied. Treatment in ethanol leads to partially preserved ordered layered structure of 2D mordenite, presumably due to the slowdown of the hydrolysis of titanium tetraethoxide; this, in turn, provides higher mesoporosity after calcination, created by anatase nanoparticles of ~4 nm in the interlayer space. Immobilization of TiO2 on the zeolite surface is indicated by the formation of Si–O–Ti bonds. [ABSTRACT FROM AUTHOR]

Bio-oil contains many oxygenated compounds, as well as high acid and water content, which can reduce the stability of its components and have poor overall physicochemical properties. In this study, the quality of bio-oil produced from the pyrolysis of oil palm fronds was enhanced through a hydrodeoxygenation (HDO) reaction that was preceded by esterification as a pre-treatment. The catalyst used in the HDO reaction is mixed metal oxide (Fe2O3-CoO) anchored within zeolite mordenite (Fe2O3-CoO/Mor). The catalysts were characterized using XRD, SEM-EDX, and BET methods. The presence of metal oxides on the surface of mordenite increases the activity of the catalyst in producing liquid products while reducing the formation of coke. Upgrading of bio-oil has improved the physicochemical properties of bio-oil compared to the one-stage upgrading process. The analysis of product showed that the C and H content increased from 11.5 to 23.5 wt% and from 9.76 to 11.2 wt%, respectively. On the other hand, the O content decreased from 78.7 to 65.2 wt% with a degree of deoxygenation of 59.8%. Moreover, higher heating value (HHV) of the bio-oil increased by 38% from 11.6 to 16.0 MJ/kg. [ABSTRACT FROM AUTHOR]

This work is concerned with classification and study of the composition and properties of hydrothermal zeolites from the Yagodninskoe deposit, (Kamchatka) which were formed in volcanic rocks. The study involved X-ray phase analysis and X-ray fluorescence, optical and scanning electron microscopy. We determined specific syrface AREA the pore size distribution, as well as cation exchange capacity in zeolites. The study resulted in the identification of four main rock types at the deposit: the original unaltered perlites, zeolites rock, zeolitized tuffs, as well as poorly zeolitized tuff breccias. The Content of zeolite group minerals reaches 70%. The minerals mostly include clinoptilolite and, to a lesser degree, mordenite, stilbite, and heulandite. The zeolites are of the alkaline type, with the cation exchange capacity equal to 205.9 mg-equi/100 g. It has been found that these zeolites were mostly formed from perlites and tuff breccias. It is pointed out that the Yagodninskoe zeolites are high quality minerals, and make a promising object of further exploration. [ABSTRACT FROM AUTHOR]

Adsorption of various glycerol conformations at Brønsted sites in mordenite is studied by the density functional theory. It is shown that the adsorption energy depends on the initial conformation of the glycerol molecule and ranges from –44.0 kcal/mol (ββ conformation) to –64.7 kcal/mol (αγ conformation). In some cases, the glycerol molecule switches its conformation as a result of nanoconfinement. It is shown that the most energetically favorable adsorption of glycerol on mordenite proceeds via the primary OH group. High adsorption energy is due to the proton transfer from the zeolite Brønsted site to glycerol as a result of the hydrogen bond formation and also due to the formation of up to four additional hydrogen bonds with oxygen atoms of the zeolite framework. As a result, the backbone of the adsorbed molecule deforms, which fact should affect the course of chemical reactions involving glycerol. [ABSTRACT FROM AUTHOR]

The Pauzhetka geothermal field was surveyed to study the mineral deposits that were formed as thermal water was discharged from well separators. We studied the compositions, structure, and geochemical properties of these sediments along the flow and in vertical cross sections of manmade "sinters". It was found that, at the beginning of thermal water discharges, the sediments were composed of X-ray-amorphous mordenite–opal mixtures; later on, the sediments became wholly siliceous. The zeolite component of the mineral deposits determines their high sorption properties in relation to Au, Ag, Hg, As, Rb, Sr, Ba, Cs and other elements; the mordenite matrix receives sulfides of iron, silver, and copper. It is shown that the mineral deposits which were formed at the ground surface of the Pauzhetka geothermal field constitute an indicator of alkaline mineral-forming and ore-forming environment in the lower horizons of the Pauzhetka geothermal system. [ABSTRACT FROM AUTHOR]

Mordenite was synthesized at 170 ºC under stirring (60 rpm) with different contents of L-glutamic acid monosodium salt (MSG) between 4 and 48 h. The materials were characterized by XRD, EDX, NH3-TPD, TG/DTG, SEM and N2 physisorption. The catalytic activity of zeolites was evaluated in the n-hexane cracking reaction at 550 ºC for 180 min. Mordenite was obtained with high relative crystallinity (83 ˗ 101%). The insertion of the amino acid salt reduced the acidity of the zeolites from 0.788 to 0.612 mmol g-1. Thermal analyses indicated the complete removal of MSG from the zeolite structure after washing, eliminating the calcination process and consequently, reducing costs. The micrographs revealed crystals of < 10 μm. N2 physisorption isotherms showed an increase in microporosity (SMicro from 411 to 445 m2 g-1 and VMicro from 0.165 to 0.178 cm3 g-1) and a higher degree of mesoporosity (VMeso from 0.009 to 0.012 cm3 g-1) for the samples with the lowest contents of MSG, indicating an optimal range for the addition of amino acid salt. The results of the n-hexane cracking reaction over mordenite samples revealed a higher tendency for the production of light olefins. The Mor/6Glut sample demonstrated high activity and a slower deactivation rate than conventional mordenite, due to the synergy of its lower acidity and mesoporosity. [ABSTRACT FROM AUTHOR]

Bio-oil from the pyrolysis of palm fronds waste has potential to be used as an alternative fuel. However, due to its poor physicochemical properties, it requires further treatment to improve its overall quality. In this study, the conversion of palm fronds waste into bio-oil was carried out using the semi-fast pyrolysis at 500 °C and continued with esterification and hydrodeoxygenation (HDO). Metal oxides of Cu and Zn with a zeolite carrier mordenite (Mor) were used as bifunctional catalysts in the HDO reaction performed in a fixed-bed system reactor with temperature variations (250, 300, and 350 °C) for 2 h. Upgraded bio-oil (UBO) products at optimum conditions were analyzed for their physicochemical properties. In the pyrolysis process, the highest bio-oil conversion of 46.3% was obtained at a sample size of 60 mesh with the main component of furan compounds (46.31%). In the upgrading process through the esterification pretreatment, the optimum condition of HDO was determined to be at 300 °C, this can be seen from the high yield of liquid phase products produced on each catalyst (Mor; 89.85%, and CuO-ZnO/Mor; 88.25%). The physicochemical properties of upgraded bio-oil obtained under optimum conditions showed an increase in the quality of bio-oil with a decrease in water content (up to 23%), an increase in higher heating value (HHV) (up to 14.67% in CuO-ZnO/Mor). It is known that HDO with CuO-ZnO/Mor catalyst has a higher selectivity than Mor catalyst in converting aromatic hydrocarbon compounds such as methyl cyclohexane which is a potential component of a fuel. [ABSTRACT FROM AUTHOR]

The adsorption, temperature-programmed desorption, and carbonylation of dimethyl ether (DME) in the presence of mordenite and ferrierite (SiO2/Al2O3 ≈ 20, Zeolyst International) is studied. The effect of introducing Cu, Co, and Mg cations by ion exchange is discussed. Dimethyl ether carbonylation is conducted at 200°С, a pressure of 3 MPa, and a space velocity of 8000 mL g–1 h–1 in the following mixture (vol %): DME, ⁓2.2; CO, 92.8–95.5; and the rest, N2. After an induction period, the methyl acetate content in the presence of mordenite is about 4–5 times higher than that in the presence of ferrierite. Water, methanol, and hydrocarbons are formed in trace amounts. The introduction of Cu, Co, and Mg cations into mordenite by ion exchange (single ion-exchange run, cation/Al ratio of no more than 35%) leads to an increase not only in stability, but also in activity in the DME carbonylation reaction. It is found that an increase in the content of copper (from 1.19 to 2.23 wt %) and magnesium (from 0.62 to 1.8 wt %) has different effects on activity. It increases in the case of copper and decreases in the case of magnesium. The prereduction of a copper-exchanged mordenite leads to the appearance of metallic copper particles on the surface of the mordenite crystallites and a decrease in activity. According to in situ diffuse reflectance infrared spectroscopy, the introduction of magnesium cations by three ion-exchange runs leads to a significant decrease in the number of Brønsted acid sites (BASes) in both the 12-MR and 8-MR channels of the mordenite. The catalytic characteristics of ferrierite hardly change upon the introduction of copper and magnesium by ion exchange. [ABSTRACT FROM AUTHOR]

A study is performed to establish the main factors that allow regulation of the activity and selectivity of the synthesis of solketal from glycerol and acetone, and the acidic and catalytic properties of mordenite zeolites (MOR, SiO2 : Al2O3 = 29.2) and faujasite (FAU, SiO2 : Al2O3 = 14.9; 97 and 810). The reaction is studied in a methanol solution at an acetone : glycerol molar ratio of 2.5 and a temperature of 25–50°C. Using zeolites, the main product is solketal with a selectivity of 88.1–94.7%. It is shown that the main factors determining the conversion of glycerol and the yield of solketal are the accessibility of the reagents to active sites, the number and strength of acid sites, and their resistance to the toxic action of water molecules that form during the reaction. [ABSTRACT FROM AUTHOR]

Micro-mesoporous Mordenite and ZSM-5 zeolites with tailor-made pore structures are produced using post-synthetic dealumination and desilication treatment. Inductively coupled plasma–optical emission spectroscopy (ICP-OES) analysis showed that post-synthetic acid and base treatment resulting into tuning the Si/Al ratio, thereby increasing the acidity of sample. Acidic characteristics of the samples were confirmed using pyridine FTIR and NH3− TPD. Acetic acid was converted to benzyl acetate by reacting with benzyl alcohol, over both hierarchical samples and their parent counterparts. Acid-modified zeolites were compared with those of base-modified one and also with the unaltered parent materials. Mesoporous pore volume of all zeolites significantly increased due to base alteration compared to the acid alteration and the parent samples. In other studies, the micro-/meso-H-ZSM-5 catalyst showed considerable potential for benzylation, exhibiting an impressive AA conversion rate of 94% with 95% benzyl acetate selectivity. In comparison, in the current study, an alternative catalyst consisting of base-altered Mordenite was found to surpass these results, achieving a 100% AA conversion and 98.2% selectivity towards benzyl acetate. Optimization of the process was investigated by altering time, temperature and catalyst amount. Analysis of reaction products was validated by GC and GC–MS. The reaction rate constants exhibited a positive correlation with increasing reaction temperature, as per the principles of first-order reaction kinetics (R2 > 0.94); and activation energy for AA benzylation over Mor-0.1 M NaOH was found to be 13.87 kJ mol−1, which is significantly lower than the previously reported value. [ABSTRACT FROM AUTHOR]

In this contribution, the formation and growth of coke and its consequences on the mordenite catalyst were investigated on microbalance, through the transformation of propene at 350 °C. The kinetic results revealed that a higher initial coking activity leads to faster initial deactivation and there is a proportionality between the rate of coke formation and the rate of its deactivation. The increase of propene pressure supports the rate of coke formation rather than its growth to heavier and more aromatic molecules. This self-deactivation results from the inhibition of Brønsted acid sites predominantly by pore blockage. Combining the residual acidity and coke composition data makes it possible to estimate the contribution of pore blocking and site poisoning. These two deactivation modes are related and occur simultaneously. [ABSTRACT FROM AUTHOR]

Volcanic tuffs and sandstones have been used as natural building stones in the construction of monuments and buildings over the millennia of human history. Progressive weathering over time (e.g., temperature fluctuations, moisture uptake, variations in humidity, precipitation, the input of modern-day pollutants or salt crystallization) lead to damages in the internal structure of the stone. Scaling and layer-parallel flaking of rock fragments result from these types of damage-causing processes, especially when swellable clay minerals are present that lead to the generation of stresses in the rock fabric. Tuff and sandstone samples that exemplify these types of damages are investigated in this study, which were used in the construction of cultural heritage sites in Armenia, Mexico, Germany and Switzerland. Comparisons are made between these rock types considering that they show strong variations in fabric heterogeneity, grain sizes, mineralogical composition (e.g., swellable clay- and zeolite-bearing minerals), and visible macroscopic features such as depositional layering. Comprehensive investigations have been carried out that include detailed petrographic analyses, XRD analyses for the determination of the swellable and non-swellable clay fraction and minerals of the zeolite group, the cation exchange capacity (CEC), detailed SEM surveys for determining the type and localization of clays and zeolites in the rock fabric, as well as defining the petrophysical properties (e.g., porosity, capillary water uptake, water absorption, hydric expansion and mechanical properties). Moreover, this study explores the possible interaction between swellable clay minerals and zeolites (mordenite, heulandite/clinoptilolite) by conducting swelling experiments with salts and solvents and fluid-exchange experiments with and without the presence of zeolites. To explain the damages caused by the expansion in the tuffs and sandstones, two principle modes of moisture expansion are discussed when swellable clay minerals are present in the rock. These are dominantly inner or intracrystalline swelling, and secondarily, intercrystalline or osmotic swelling. When no swellable clay minerals are present, the study explains the damages in tuffs and sandstones as the result of disjoining pressure, where a high percentage of microporosity plays a pivotal role. [ABSTRACT FROM AUTHOR]

The H2O2 evaporation rate directly affected the oxidation of NO by H2O2. Green zeolite and synthetic mordenite were selected to promote H2O2 thermal decomposition and NO oxidation. The effects of different zeolites, evaporation conditions, temperatures, and reactant concentrations on the NO oxidation ratio were explored. The promotion mechanism of zeolite on NO oxidation by H2O2 thermal decomposition was explained. The results show that the zeolite surface can significantly accelerate the H2O2 evaporation rate to obtain a high NO oxidation ratio. The hydrophilicity and rich pore structure of zeolite enable the rapid diffusion and evaporation of droplets on the zeolite surface. Compared with the green zeolite with the mesoporous structure, the synthetic mordenite with the hierarchical pore structure has a more obvious promotion effect on the NO oxidation by H2O2 thermal decomposition. The reason is that the synthetic mordenite contains micropores, resulting in a larger specific surface area, and the mesoporous structure is conducive to the mass transfer and diffusion of H2O2 on its surface. The product of NO oxidation is mainly NO2, which proves that ·OH plays a major role in the process. [ABSTRACT FROM AUTHOR]

The application of mordenite in the adsorptive removal of Fe(III) from aqueous solution was investigated. Zeolite mordenite was synthesized hydrothermally without using an organic template. The synthesized material was characterized by X-ray diffraction (XRD) and Thermogravimetric analysis (TGA). The effect of various experimental parameters viz. pH, contact time and initial metal concentration on the adsorption process was studied. The Langmuir model, with a correlation value of 0.998, accurately explains the adsorption data, demonstrating that Fe(III) adsorption from aqueous solution proceeds via monolayer adsorption. The adsorption kinetic model was well-fitted by pseudo-second-order kinetic model. [ABSTRACT FROM AUTHOR]

The argillized deposits of the East Pauzhetka thermal field in the Pauzhetka hydrothermal system were found to contain a zone of intensive zeolitization which consists of medium to high silica calcium zeolite varieties, namely, laumontite, mordenite, heulandite-Ca, and stilbite-Ca. Of all these, stilbite-Ca has the highest abundance. The zeolites can be identified well enough based both on the relationship between Si and Al, which are part of the zeolite framework, and on the concentrations of non-framework cations (Ca, Mg, Na, K, Sr, and Ba). Zeolites are mostly formed in the lower horizons of hydrothermal clays and in the underlying argillized andesites, as deep alkaline chloride-sodium hydrothermal fluids are discharged and are mixed with condensates of acid (up to neutral) vapor. The resulting sequence of zeolite generation in the shallow zone where alkaline solutions are discharged reflects, to a certain degree, a change of zeolite facies in the deeper horizons of the system: from medium-silica laumontite to high silica stilbite-Ca. We have thereby a general inference as to the regressive directivity of hydrothermal metamorphic processes in the Pauzhetka system structure, from medium-temperature propylites generated during the paleo phase to the present-day low-temperature mudstones. [ABSTRACT FROM AUTHOR]

Kinetics of Cs+ uptake by natural and synthetic mordenites was studied. The experimental data is best fitted to the pseudo-second-order rate model and the parameters k2 and qe are calculated. The application of intra-particle diffusion and liquid film diffusion models show multilinear graphical dependence, indicating that both mechanisms influence the run of uptake. Rietveld XRD structural analyses were used for identification of the positions preferably occupied by Cs+ cations during the ion-exchange as a function of contact time. The obtained results show that the predominance of Na+ ions in the initial samples makes the exchanged sites more accessible by Cs+ ions. [ABSTRACT FROM AUTHOR]

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

A fine-tuned mordenite was prepared to overcome the low selectivity of tert-amyl anthracene production in the direct alkylation of anthracene. Herein, a series of boric acid-modified Fe-Zr mordenite materials were prepared, and tert-amyl anthracene was smoothly and efficiently obtained over these catalysts. The boron sites in modified catalyst promoted the alcohol dehydrogenation, which benefited the reaction conversion. Moreover, the existence of Brønsted and Lewis acid sites was the key in alkylation reaction, making 1.0B-Fe-Zr/MOR good reactivity (Conv. 47.8%, Sel. 91.4%). Calculated results correlated the products properties with catalyst structures, verifying that boric acid-modified Fe-Zr/MOR was a successful shape-selective catalyst. The present work opens a new frontier for a sustainable and high-selective method to process anthracene alkylation. [ABSTRACT FROM AUTHOR]

Cobalt-based catalysts supported on MOR zeolites with various degree of dealumination were prepared and characterized by XRD, N2 adsorption, SEM, UV–vis, XPS, H2-TPR and FTIR. Their catalytic performance for ethane dehydrogenation was compared. More Co(II) species were found on the surface of dealuminated zeolites, leading to an enhancement in dehydrogenation activity. An ethane conversion of 53.4% with 92.1% selectivity to ethylene can be obtained over optimal catalyst. Characterization results indicate the increasing Co(II) species may derive from the increased silanol nest of MOR support via dealumination, which can interact with cobalt precursor to enhance its dispersion. [ABSTRACT FROM AUTHOR]

Mechanisms of Cr(VI) reduction by Fe(II) modified zeolite (clinoptilolite/mordenite) and vermiculite were evaluated. Adsorbents were treated with Fe(SO4)·7H2O to saturate their exchange sites with Fe(II). However, this treatment decreased their CEC and pHPZC, probably due to the dealumination process. Vermiculite (V-Fe) adsorbed more Fe(II) (21.8 mg g−1) than zeolite (Z-Fe) (15.1 mg g−1). Z-Fe and V-Fe were used to remove Cr(VI) from solution in a batch test to evaluate the effect of contact time and the initial concentration of Cr(VI). The Cr(VI) was 100% reduced to Cr(III) by Z-Fe and V-Fe in solution at 18 mg L−1 Cr(VI) after 1 min. Considering that 3 mol of Fe(II) are required to reduce 1 mol of Cr(VI) (3Fe+2 + Cr+6 → 3Fe+3 + Cr+3), the iron content released from Z-Fe and V-Fe was sufficient to reduce 100% of the Cr(VI) in solutions up to 46.8 mg L−1 Cr(VI) and about 90% (V-Fe) and 95% (Z-Fe) at 95.3 mg L−1 Cr(VI). The Fe(II), Cr(III), Cr(VI), and K+ contents of the adsorbents and solutions after the batch tests indicated that the K+ ions from the K 2 Cr 2 O 7 solution were the main cation adsorbed by Z-Fe, while vermiculite did not absorb any of these cations. The H+ of the acidic solution (pH around 5) may have been adsorbed by V-Fe. The release of Fe(II) from Z-Fe and V-Fe involved cation exchange between K+ and H+ ions from solution, respectively. The reduction of Cr(VI) by Fe(II) resulted in the precipitation of Cr(III) and Fe(III) and a decrease in the pH of the solution to < 5. As acidity limits the precipitation of Cr(III) ions, they remained in solution and were not adsorbed by either adsorbent (since they prefer to adsorb K+ and H+). To avoid oxidation, Cr(III) can be removed by precipitation or the adsorption by untreated minerals. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

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]

Anthropogenic CO2 emissions are the major drivers of global warming and climate change. The adsorption of CO2 is one of the strategies to mitigate these emissions. In this sense, different materials have been used as adsorbents as is the case of zeolites. In this work,experimental infrared and X-ray analyses together with DFT (Density Functional Theory)theoretical calculations were employed to study the adsorption of CO2 on mordenite zeolites (Na-MOR). Ion exchange followed by chemical analysis showed that the Na+ of Na-MOR was not completely substituted under the experimental conditions employed. The XRD (X-ray Diffraction) analysis indicated that Na+ exchanged for Li+ did not affect the crystallinity of the materials. The infrared results showed that CO2 interacted linearly with the sodium and lithium cations present in the main channel of the mordenite framework. Sodium in dry samples favored the formation of carbonates and hydroxycarbonate species, as did the presence of low water content in the LixNa-MOR. The DFT periodical calculation of dehydrated mordenite models led to CO2 adsorption energies in the range of − 31.6 to − 34.2 kJ mol−1, with the highest adsorption energy found for sodium mordenite.The asymmetric stretching ν3 (CO2) vibration mode resulted intense and presented a shift which indicated a higher CO2 interaction of Na-MOR. The presence of some water molecules in the mordenite framework caused a decrease in the adsorption energy. [ABSTRACT FROM AUTHOR]

This study examines a selective removal of Al metal from Al-Beta (BEA), Al-Faujasite (FAU, type Y) and Al-Mordenite (MOR) whose frameworks have high and close Si/Al ratios ≥ 30. Dealumination was performed using acid leaching (nitric acid, 13 M) solution at 100 °C for 20 h. Unlike Al-BEA, Al-FAU and Al-MOR were hardly dealuminated for their ultra-stable structure. Solid-state incorporation (SSI) method was applied to incorporate Lewis acidic Sn metal in dealuminated zeolitic frameworks. Newly formed zeolites have numerous vacant tetrahedral sites with a siliceous-rich framework. These zeolites were characterized by powder XRD, elemental analysis, N2 sorption, DRIFT and 27Al MAS NMR spectroscopies. Meerwein–Ponndorf–Verley (MPV) was selected as a reaction to assess the catalytic performance of prepared zeolites. While SSI-Sn-BEA exhibited superior catalytic activity for the presence of Lewis acid-Sn, FAU and MOR showed less catalytic activity due to their confined structural effects, presence of silanol nest and inadequate Sn incorporation. [ABSTRACT FROM AUTHOR]

This work is a successful synthesis of a series of ZSM and ZK zeolites on the basis of the natural zeolite of Nakhchivan without organic agent along with the research of the effect of temperature and alkalescency on the process of their crystallization. The respective natural sample has been obtained from the zeolite horizon in the north-west of the Kyukyuchai River, where zeolite content varies in the range of 75–80%. Zeolite tuffs of Nakhchivan have been used as a source of the sample, 78.5% of which is the major mineral – mordenite, 19.5% is quarts, and 2.00% is anortite. The initial material and the resultant products have been studied using the X-ray diffraction and IR-spectroscopy analysis techniques. The optimum conditions for maximum crystallinity degree of synthesized zeolites ZSM and ZK have been obtained. It has been found that crystallization temperature and alkalescency have different effects on the rate formation of resultant products, their degree of crystallinity, pure phase zeolite. It has been found that the synthesis of zeolites ZSM-5, ZSM-10, ZSM-25, ZK-5 and ZK-4 takes a long time, with the exception of ZK-4, which has been obtained within a few hours. These results can be explained by the Goldschmidt principle. [ABSTRACT FROM AUTHOR]

Dehydrogenation of ethane to ethylene assisted by CO2 was investigated over CrOx catalysts supported on MOR zeolites. The catalysts were characterized by XRD, N2 adsorption, SEM, 27Al and 29Si MAS NMR, XPS, DRIFTS, H2-TPR and laser Raman spectroscopy. The catalysts exhibit enhanced activity and stability after MOR dealumination, with an optimal ethane conversion of ~ 38% and ethylene yield of ~ 33%. Characterization results indicate that the improved catalytic performance derives from the increased silanol nests of MOR support created by acidic dealumination, which are in favor of dispersion and stabilization of CrOx species, resulting in more reducible Cr(VI) considered as the active site for dehydrogenation. [ABSTRACT FROM AUTHOR]

Helicobacter pylori can be found in the stomach of about half of the humans, and a large population can be associated with serious diseases. To survive in the stomach H. pylori increases the pH locally by producing ammonia which binds to H+ becoming ammonium. This work investigated the effects on the in-vitro growth of H. pylori of a natural cation-exchanger mainly composed (≈70%) of clinoptilolite and mordenite. The zeolitized material from Cuba was evaluated in its original form (M), as well as in its Na- (M-Na) and Zn-exchanged (M-Zn) counterparts. In the preliminary agar cup diffusion test, H. pylori revealed susceptibility only to M-Zn, with a direct relationship between concentration and width of inhibition halo. Further experiments evidenced that bacterium replication increases when ammonium is supplied to the growth medium and decreases when zeolites subtract NH4+ via ion exchange. Due to the multi-cationic population of its zeolites M was not effective enough in removing ammonium and, in the Minimum Inhibitory Concentration (MIC) test, allowed bacterial growth even at a concentration of 50 mg/mL. Inhibition was achieved with M-Na because it contained sodium zeolites capable of maximizing NH4+ subtraction, although the MIC was high (30 mg/mL). M-Zn evidenced a more effective inhibitory capacity, with a MIC of 4 mg/mL. Zinc has antimicrobial properties and H. pylori growth was affected by Zn2+ released from clinoptilolite and mordenite. These zeolites, being more selective towards NH4+ than Zn2+, can also subtract ammonium to the bacterium, thus enhancing the efficacy of M-Zn. [ABSTRACT FROM AUTHOR]

Zr-mordenite catalysts were prepared by post-treatment method and H-mordenite catalyst was synthesized by hydrothermal method for the dimethyl ether carbonylation reaction. XRD, N2 adsorption/desorption, ICP-OES, SEM, TEM, UV–Vis, XPS, Raman, CO-TPD, NH3-TPD, 27Al MAS NMR, FTIR and Py-IR were employed to characterize the catalysts. The results demonstrated that part of Zr atoms existed in a tetrahedral coordination state after incorporating into the mordenite framework. Zirconium Lewis acid sites with the ability to absorb CO molecules were formed during this process although the amount of Brønsted acid sites in 8-member ring channels decreased upon the incorporation of zirconium. During the concentration of zirconium nitrate solution increased from 0.02 to 0.08 mol/L, the Zr-mordenite catalyst through post-treatment with 0.04 mol/L zirconium nitrate solution exhibited the best catalytic performance at 473 K and 1 MPa. Dimethyl ether conversion and methyl acetate selectivity increased to 78% and 96% respectively compared with H-mordenite catalyst. Schematic of Zr incorporating MOR framework [ABSTRACT FROM AUTHOR]

Nylon 6-mordenite composite membranes having porous morphology were applied to the selective separation of heavy metal ions from aqueous heavy metal solution with Pb2+, Cu2+ and Cd2+. The membrane preparation was carried out in the wet phase inversion method using methanol/CaCl2/Nylon 6 solution. The resultant membranes containing mordenite powders with 10, 20 and 30 wt% loading were obtained as coagulated in water. Depending on the mordenite loading in the composite membranes, the porous morphology was changed in a finger-like and/ or sponge structure. In batch adsorption experiments, the higher mordenite loading in the composite membranes was the higher separation capacity for heavy metal ions. The composite membrane loading 30 wt% mordenite (NZC 30) had the optimal performance of Pb2+ ion capture in the maximum adsorption capacity of 38.5 mg/g at pH 5. The batch separation factor calculated using Langmuir isotherm parameters supported the selective adsorption of Pb2+ relative to those of Cd2+ and Cu2+. In addition, the permeabilities of water and the mixed ion solution with 20 mg/L concentration were investigated. The value of the separation factor of NZC 30 was 9.2 for Pb2+ against Cu2+. In the regeneration of the reused membranes, the values of the regeneration efficiency of NZC 30 still maintained a good separation performance in Pb2+ with 24.1 mg/g at 5-time reusing. Article Highlights: The porous nylon 6-mordenite zeolite composite membranes were fabricated by the wet phase inversion method for the first report. The composite membrane containing 30 wt% mordenite (NZC 30) showed the extraordinary performance for the separation of Pb2+ with 89.9 % from the mixture solution. The separation factor of NZC 30 was 9.2 for Pb2+against Cu2+ The composite membranes can be used as a low-cost and environmentally friendly adsorbent for the separation of heavy metals from wastewater. Porous nylon 6-mordenite composite membranes were fabricated from methanol/CaCl2/Nylon 6 solution via the wet phase inversion method and applied to selective separation of Pb2+, Cu2+ and Cd2+ from mixture solution [ABSTRACT FROM AUTHOR]

Three zeolites (Beta, Mordenite and ZSM-5), which present different pore channels but the same Si/Al ratio (25), were used as catalysts to investigate the effects of acidity and channel structure on the catalytic activity for toluene butylation at 180°C in an automated high-pressure stainless steel reactor. The same Si/Al ratio of the three zeolites did not result in a similar catalytic activity, since both acidity and channel structures of zeolites can affect catalytic activity. Zeolite Beta possessing a 3D 12-ring channel system, the smallest crystal size and larger amount of B acid sites exhibited the highest toluene conversion (54.0%). Mordenite, with 32.7% toluene conversion, presented higher para-selectivity than Beta, which can be explained by the shape-selective catalysis. ZSM-5 with the largest amount of B acid sites showed the lowest catalytic activity, since alkylation can occur only on the surface active sites. [ABSTRACT FROM AUTHOR]

The current research presents the fabrication of mordenite nanoparticles via a hydrothermal technique using low-cost mixed organic templates. The utilized templates such as (polyethylene glycol 200 and glycerol), (polyethylene glycol 200 and ethylene glycol), (ethylene glycol and glycerol), and (ethylene glycol, polyethylene glycol 200, and glycerol) were named PEG-GL, PEG-EG, EG-GL, and EG-PEG-Gl, respectively. Characterization of the fabricated nanoparticles was carried using FE-SEM, HR-TEM, FT-IR, XRD, and BET techniques. XRD confirmed that the average crystallite sizes of PEG-GL, PEG-EG, EG-GL, and EG-PEG-Gl were 86.78, 38.75, 98.70, and 45.96, respectively. Also, HR-TEM confirmed that the average diameters of the previous samples were 80.42, 35.50, 92.85, and 44.73, respectively. In addition, FE-SEM confirmed that the previous samples consist of (spherical and cup), (tree leaves and cylindrical rods), (cylindrical rods and spherical), and (spherical and rods) shapes, respectively. Besides, characteristic vibrations of mordenite such as internal symmetric, external symmetric, internal asymmetric, external asymmetric, and bending were detected using FT-IR at 690–705, 780–795, 1025–1030, 1222–1235, and 447–464 cm−1, respectively. The PEG-EG sample efficiently removed Pb(II) ions from aqueous media where 17.40 mg/g is the capacity value. Pore diffusion, intra-particle diffusion, pseudo-first-order, and liquid film diffusion kinetic models successfully described the removal of Pb(II) ions in the view of the kinetic study. In addition, Langmuir isotherm successfully described the removal of Pb(II) ions in the view of the equilibrium study. Moreover, the exothermic and chemisorption properties of the removal of Pb(II) ions were confirmed in the view of the thermodynamic study. The capacity of the PEG-EG sample or % removal of Pb(II) ions was not greatly affected after five desorption-adsorption cycles. [ABSTRACT FROM AUTHOR]

Isobutylene synthesis from acetone in the presence of micro–mesoporous MOR zeolites obtained by hydrothermal recrystallization and modified with magnesium acetate by incipient wetness impregnation has been studied. A kinetic study of the reaction has been conducted, and product formation routes have been determined. It has been found that an increase in the mesopore content leads to an increase in the catalyst activity owing to the removal of diffusion restrictions. It has been shown that isobutylene formation occurs on both Lewis and Brønsted acid sites. The modification of the initial aluminosilicates with magnesium has been found to decrease the number and strength of Brønsted acid sites and thereby lead to a decrease in the number of side reactions and an increase in the time-on-stream stability of the catalysts. [ABSTRACT FROM AUTHOR]

The effects of temperature and duration of thermochemical treatment in a sodium silicate solution of metakaolin; a mechanical mixture containing 60 wt % mordenite, 30 wt % metakaolin, and 10 wt % fumed silica; and granules of the same composition on the mass transfer between the liquid and solid phases of the reaction mixture have been studied. The main steps of the formation of high-crystallinity granular mordenite with a hierarchical pore structure have been established. [ABSTRACT FROM AUTHOR]

Synthesis of ethanol from non-petroleum carbon resources via syngas (a mixture of H2 and CO) is an important but challenging research target. The current conversion of syngas to ethanol suffers from low selectivity or multiple processes with high energy consumption. Here, we report a high-selective conversion of syngas into ethanol by a triple tandem catalysis. An efficient trifunctional tandem system composed of potassium-modified ZnO–ZrO2, modified zeolite mordenite and Pt–Sn/SiC working compatibly in syngas stream in one reactor can afford ethanol with a selectivity of 90%. We demonstrate that the K+–ZnO–ZrO2 catalyses syngas conversion to methanol and the mordenite with eight-membered ring channels functions for methanol carbonylation to acetic acid, which is then hydrogenated to ethanol over the Pt–Sn/SiC catalyst. The present work offers an effective methodology leading to high selective conversion by decoupling a single-catalyst-based complicated and uncontrollable reaction into well-controlled multi-steps in tandem in one reactor. Direct synthesis of ethanol from non-petroleum carbon resources via syngas (CO/H2) is a highly attractive but challenging target. Here, the authors report a triple tandem catalytic system for single-pass conversion of syngas into ethanol with selectivity as high as 90%. [ABSTRACT FROM AUTHOR]

Corrosion processes of painted metals may be monitored by accelerated and/or electrochemical assays. There is certain relationship between both types of test. Particularly, when using paint coatings with high barrier effect (R > 108 Ω cm2) and low dielectric capacity (C < 10−9 F cm−2), a good anti-corrosion performance was accomplished and results from both types of tests match. Once corrosion has started, a charge transfer resistance value > 106 Ω cm2 ensures kinetic inhibition of the corrosion process. The question arises when the values of the above-mentioned parameters differ from those and a realistic approach to the coating useful service life is needed. In this paper, it was demonstrated that, in such cases, accelerated and electrochemical assays complement each other. Accelerated tests are related to coating durability while electrochemical ones provide information about the degradation mechanism. To carry out this investigation, three anti-corrosive paints containing ecological pigments were prepared and their protective behavior evaluated in the salt spray chamber and by electrochemical impedance spectroscopy (EIS). [ABSTRACT FROM AUTHOR]

The process of dealumination of mordenites differing in morphology and crystal size obtained under identical conditions from reaction mixtures of similar composition has been studied. Parameters that have been chosen to change the morphology and crystal size are the dry matter concentration in the reaction mixture, the pH of the reaction mixture, the crystallization time, the presence of crystalline seeds, and agitation during the synthesis. Dealumination has been performed by heat treatment at 700°C followed by acid treatment. It has been shown that the stability of the mordenite crystal framework to dealumination depends on the thickness of the primary needle crystal, which forms the basis of large zeolite crystals, not on the size of the zeolite crystal as a whole. With a decrease in the average needle crystal thickness from 250 to 90 nm, the Si/Al molar ratio in the crystal lattice, determined from 29Si NMR data, increases from 6.8 to 9.5. The dealumination is accompanied by a change in the texture of large mordenite crystals associated with a decrease in the packing density of the primary needles. [ABSTRACT FROM AUTHOR]

Two zeolite structures (mordenite and ZSM-5) were crystallized as a mesostructure by a one-pot hydrothermal method using a supramolecular assembly and applying cetyltrimethylammonium bromide (CTAB) as a surfactant. The as-prepared materials were subjected to a pillaring process with amorphous SiO2 forming MFI-P and MOR-P pillared systems. The textural properties were significantly improved due to the efficient pillaring process, i.e., surface areas increased from 255 to 687 m2/g for MFI and from 393 to 710 m2/g for MOR. The zeolitic materials grew in the form of lamellar mesostructures when CTAB was used as a bulk filler between the laminar arrays of zeolites as revealed by transmission electron microscopy and X-ray diffraction. The lamella sizes were in the range of ~ 2.5 nm, which is similar to one unit cell of the growing zeolite for both samples. These results are consistent with the theoretical calculations obtained by the Powdercell program for the X-ray diffraction powder pattern of the mesostructured lattice for both samples. It was found that calcining of the as-synthesized samples at 550 °C leads to a non-congruent collapse of the mesostructure. [ABSTRACT FROM AUTHOR]

The synthesis of aluminosilicate zeolites by using piperazine as the organic structure-directing agent was studied. Under optimized conditions, zeolites ZSM-4 (MAZ), mordenite (MOR), ZSM-35 (FER), ZSM-5 (MFI) and ZSM-12 (MTW) were obtained in pure phase. The effect of SiO2/Al2O3 ratio in the initial gel on zeolite phase selectivity was systematically investigated. The SiO2/Al2O3 ratio ranges for the formation of each zeolite had been established. At low SiO2/Al2O3 ratios, ZSM-4 (SiO2/Al2O3 = 9) and mordenite (SiO2/Al2O3 = 12.8) could be obtained, while ZSM-35 (14.3 ≤ SiO2/Al2O3 ≤ 29.3), ZSM-5 (SiO2/Al2O3 = 58.7) and ZSM-12 (SiO2/Al2O3 = 117.2) gradually evolved as the SiO2/Al2O3 ratio increased. Piperazine was considered to have a charge-compensatory role when the amine group was protonated; its overall effectiveness depended on the zeolite structure. Piperazine fitted best with the FER structure, and the obtained FER zeolite had a hierarchical house of card texture which was assembled by the primary plate-shaped crystals. The ZSM-4, mordenite and ZSM-35 zeolites (in acidic form) were tested for the dimethyl ether carbonylation reaction; the essential role of 12-member ring (12MR) pore in mordenite for molecule transportation to the 8MR pore was proved by comparing to ZSM-4 that lacks interconnectivity between 12MR and 8MR pores. [ABSTRACT FROM AUTHOR]

Experimental and theoretical XRD patterns of mordenite frameworks were correlated in this work. The experimental XRD analysis showed that the incorporation of Ag and Fe ions in mordenite modified the intensity of peaks in the diffraction patterns. For theoretical studies, two framework models of mordenite (MOR6 and MOR7) were used. Theoretical results conducted through DFT computational simulations were able to predict correctly the angular positions of the experimental peaks observed in XRD patterns. These theoretical results showed that the ion exchange of Na+ by Ag+ cations in the zeolitic framework leads to a decrease in intensity of XRD peaks {2 0 0}, {0 2 0} and {1 5 0}, similar to observed experimentally. This is caused by local structural rearrangements produced by the ion exchange. For Fe incorporation in zeolite, two options were considered theoretically: ion exchange and isomorphous substitution of Al3+ in tetrahedral positions. [ABSTRACT FROM AUTHOR]

Anatase–mordenite nanocomposite was synthesized in situ and characterized by X-ray diffraction analysis, Brunauer–Emmett–Teller measurements, infrared (IR) spectroscopy, electron diffraction measurements, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and scanning and transmission electron microscopy. It was found that X-ray-amorphous anatase located in the zeolite micropores resulted in a decrease in the specific surface of anatase–mordenite compared to the initial mordenite. Anatase-containing nanoparticles in anatase–mordenite showed round shape and formed nano-associates and conglomerates. The water content in the zeolite cavities in anatase–mordenite was lower compared to mordenite. Anatase–mordenite nanocomposite exhibited higher photocatalytic activity in the model decomposition reaction of methyl orange under ultraviolet (UV) radiation and higher adsorption capacity for extraction of P(V) and As(V) ions from aqueous environment in the dark compared to the initial mordenite or anatase due to an increase in the content of active OH-groups on the nanocomposite surface compared to mordenite and an increase in the specific surface compared to anatase. [ABSTRACT FROM AUTHOR]

Nickel catalysts supported on activated montmorillonite modified with titanium dioxide and mordenite were prepared by various methods. The catalytic properties of these catalysts in the isomerization of hexane were studied. The greatest hexane conversion (36.2%) was achieved on a nickel catalyst supported on activated montmorillonite modified with mordenite and TiO2 introduced by mixing the components. The optimal composition of the catalyst at 350°C and 1 atm gave the conversion of hexane into C4C7 isomers in 34.2% yield and 93.6% selectivity. Among the catalysts studied, this composition has the greatest specific surface, greatest amount of mesopores, as well as greatest total content of weak and medium-strength acid sites. [ABSTRACT FROM AUTHOR]

IM-5 zeolite is synthesized in solutions of sodium hydroxide, sodium aluminate, and silica gel, along with N-methyl pyrrolidine and 1,5-dibromopentane by one-pot hydrothermal method. The method described in this paper is more convenient and environmentally benign than the conventional one, in which 1,5-bis (methylpyrrolidinium) pentane bromide is used as structure directing agent, because it eliminates the complex and toxic synthesis process of the agent. The influences of synthesis variables including OH−/SiO2 ratio, H2O/SiO2 ratio, temperature, seed content, and crystallization time on the synthesis of IM-5 zeolite are studied with X-ray powder diffraction, field emission scanning electron microscopy and nitrogen adsorption characterization techniques. The experiments show that analcime and mordenite are the two impurity phases that compete with IM-5 zeolite in synthesis process and the alkalinity of solution, temperature, and the crystallization time are three key factors that affect the crystal phase of products. A tentative explanation for the mechanism of the crystal phase dependence on the synthesis variables is given. By carefully choosing synthesis conditions along with using seed, the crystallization time of synthesizing IM-5 zeolite has been greatly reduced. [ABSTRACT FROM AUTHOR]

Abstract: The hydrolysis of cellulose into glucose is a critical step for the conversion of lignocellulosic biomass into fuels and chemical products. The combination of supercritical water hydrolysis in ultrafast reactors, with the subsequent hydrolysis of the cello-oligosaccharides on silver-exchanged mesoporous mordenite zeolite, offers the possibility of a clear enhancement in the conversion of cellulose and in glucose formation. Complete dissolution of cellulose is achieved in the supercritical step and 81.8% of formed oligosaccharides are hydrolyzed in the catalytic step, with a yield into glucose of 77.0%. A fraction of Al is octahedrally coordinated, indicating a distribution of acid sites after the silver exchange. A deactivation of the catalyst between the first and third reaction cycle is observed, with a reduction in hydrolyzed carbon from 81.8% up to 45.6%. However, the selectivity to glucose only varies from 94.1 to 81.8%. Afterwards, the activity remains constant up to the fifth cycle. The presence of Ag(0) particles, together with the formation of coke, are responsible for the partial blockage of the pores of the support and loss of catalytic activity.Graphical abstract: [ABSTRACT FROM AUTHOR]

Isomerization of n-hexane on Pt-catalysts supported on activated Tagan montmorillonite in the Na-form is studied as a function of the method for introducing TiO2 into the catalyst. The textural properties of the obtained catalysts and their acidic characteristics and x-ray phase and elemental compositions were determined. The isomerization properties of Pt-catalysts supported on pillared TiNaHMM and prepared by mixing TiO2 and NaHMM were compared. A simplified method was developed for preparing Pt/NaHMM + TiO2 catalyst that had stronger isomerizing activity than Pt on pillared TiNaHMM. The maximum conversion of n-hexane was shown to be 57%; maximum total yield of C6 + C7 isomers, 51.6% on Pt/NaHMM + TiO2 + HM at 400°C. [ABSTRACT FROM AUTHOR]

The effects of temperature (540–640°C), weight hour space velocity (1.0–7.0 h–1), and steam : raw material ratios (0–2.5) on the yield of C2–C4 olefins, conversion, and octane characteristics in the cracking of a mixture of model hydrocarbons (cyclohexane and 1-hexene) were studied. The influence of the structure of zeolites in mono-, bi-, and tri-zeolite catalysts on the distribution of cracking products was examined. It was found that the combination of catalyst components in bi- and tri-zeolite systems makes it possible to increase the efficiency of the consecutive cracking of hydrocarbons (C6–C12 → C4–C8 → C3–C6 → C2–C4) according to the following reaction scheme: matrix → ZSM-5 → FER. The maximum total yield of C2–C4 olefins (50.2 wt % at a conversion of 75.5%) was achieved with the use of a bi-zeolite catalyst of ZSM-5 + FER. [ABSTRACT FROM AUTHOR]

Using a Nakhchivan natural mineral as a base, zeolites of different structural types are synthesized. Natural zeolite is modified under hydrothermal conditions in aqueous solutions of LiOH, KOH, NaOH, and Ca(OH)2, as well as in the presence of mineralizers (LiCl, KCl, NaCl, CaCl2) in an autoclave. Based on the data of IR-spectroscopic, X-ray phase, and elemental analyses, it is shown that during the hydrothermal treatment, natural zeolite is transformed into other minerals of the zeolite group that are important in practice. It is found that mordenite retains the structure's stability in the alkaline solutions with a concentration of 1 N at a temperature of up to 100°C for 10 h. When the conditions of hydrothermal treatment change, natural zeolite gradually transforms into hydrosodalite through the mineral phases: chabazite, heulandite, clinoptilolite, analcime, phillipsite, faujasite, scapolite, zeolite M, gismondine, leucite, and kalsilite. The presence of mineralizers in the environment leads to the production of structural types of zeolites that differ from those obtained in a thermal solution. [ABSTRACT FROM AUTHOR]