Zeolite Samples Research Articles

Structure-property relationship of zeolite-Y/cubic ZnS nanohybrid material and its utilization for gaseous phase mercury removal

Zinc acetate dihydrate and thiourea based metal sulfide was synthesized and used to develop zeolite-ZnS (ZY-ZnS) nanohybrid material by using sonication process, solvothermal method and heat treatment process. The sulfur atom in thiourea is involved in formation of metal sulfide and ethylene glycol was used as solvents in the solvothermal method. The structure of the nanohybrid material was analyzed by Raman spectroscopy, FTIR, XRD and XPS. Raman spectra confirmed the presence of 4, 6- membered rings of zeolite and polar modes A1 and E1 and nonpolar mode E2 of ZnS nanoparticles. The morphology of the nanohybrid material was analyzed by TEM and SEM analysis. The uniform distribution of ZnS in the zeolite matrix was observed in TEM and SEM morphology. The spherical aggregates ZnS crystals size between 100 and 200 nm were observed. Cubical morphology was observed in pure zeolite samples in the range of 400 nm−500 nm. The X-ray photoelectron spectroscopy analysis was used to confirm the metal-sulfide species in the hybrid material. Mercury adsorption (elemental (Hg°)) in the vapor phase follows both pseudo-first-order and pseudo-second-order kinetic models. Kinetic study shows that the mercury adsorption on the zeolite-ZnS nanohybrid adsorbent was mostly regulated by the chemisorption. Vapor phase mercury adsorption capacity of zeolite-Y (ZY) and zeolite-ZnS (ZY-ZnS), is 2295 and 3461 µg/g at 180 °C, respectively. In ZY and ZY-ZnS the intraparticle diffusion rates were 86.1 and 141.2 μg/gmin-1/2, respectively. The higher intraparticle diffusion rate observed in ZY-ZnS confirm the uniformly decorated ZnS nano particles in ZY-ZnS nanohybrid material.

Improved Apparatus for Dynamic Column Breakthrough Measurements Relevant to Direct Air Capture of CO2.

Dynamic column breakthrough (DCB) measurements are valuable for characterizing the adsorption of gaseous species by solid sorbents and are typically used for high concentrations of adsorptives, often at elevated temperatures and pressures. However, adsorbents for the direct capture of carbon dioxide from natural air demand measurement capability at low partial pressures of CO2 at atmospherically relevant temperatures and pressures. We have developed a new apparatus focused on the measurement of DCB curves under typical tropospheric conditions. The new apparatus is described in detail and validated with breakthrough curve measurements. Adsorption capacities are reported at (233.1 to 323.1) K and (351 to 1078) hPa for low carbon dioxide concentrations on 13X zeolite samples on the order of a few hundred milligrams. Measurement uncertainties related to timing, flow, temperature, and concentrations are analyzed and the present results at 273 K, 298 K, and 323 K are compared with static measurements obtained with a manometric adsorption analyzer. In addition, experiments at a typical atmospheric CO2 concentration of 400 μL · L-1 have been performed.

Design and optimization of multilayer composite membrane for biomethane enrichment: Process simulations and economics

The depletion of fossil fuels has led to the development of various biogas upgrading techniques that can be a reliable and sustainable energy source. At present, membrane-based gas separation and enrichment have received more acceptance to contend with the traditional biogas upgrading processes. Remarkably, multilayered composite membranes (MCM) fabricated from selective polymers and fillers have achieved high consideration in the field of CO2separation. In this regard, the present study focuses on fabricating and optimizing the porous layer of MCM using Polyether sulfone (PES) and Torlon polymers and their morphological influences on overall membrane performance. The MCM membranes fabricated from the PES porous substrate exhibited 3–4 fold higher permeation than the Torlon. Besides, the effect of zeolite type and % loading on the selective layer performance in CO2gas permeation was examined. From the gas permeation experiments, a 6 % loaded 3A zeolite sample exhibited maximum permeation flux for CO2, which is 1.7 folds compared to the neat Polyether block amide (PEBAX)/PES membrane and 5.8 fold to the neat PEBAX/Torlon without compromising the selectivity. Furthermore, process simulation using Aspen Hysys reveals the economic feasibility of membrane-based biomethane enrichment. Overall, the study results are compared with Robeson’s plot, which reveal the substantial potential of MCM-based membrane technology as a biogas upgrading process and offers assistance in developing an appropriate porous support for MCM.

Unit Cell Volume as a Measure of the Framework Composition of ZSM-5 Type Zeolites

A simple X-ray powder diffraction procedure is proposed to determine the framework composition of ZSM-5 type zeolites. The procedure is based on a linear relation between the unit cell volume and the framework aluminum content found by analyzing two families of ZSM-5 zeolites with different SiO2/Al2O3 ratios. One family consisted of products synthesized in the presence of TPA+ cations while hydrogen forms were included in the second series of samples. Linear relationships between cell constants, cell volume (Vu.c.), and the framework aluminum content (NAl) were established. For the samples synthesized in the presence of an organic template and sodium cations, the relation between NAl and Vu.c. is given by NAl = (Vu.c. – 5332 Å3)/15.13. A similar equation was computed for H-ZSM-5 zeolites: NAl = (Vu.c. – 5330 Å3)/15.40. Equations derived can be used to evaluate the number of framework aluminum in the unit cell. In this way, the ratio of the framework and nonframework aluminum atoms in the samples of ZSM-5 type zeolites subjected to heat treatment can be estimated.

Mechanoactivation of Clinoptilolites with Sodium and Ammonium Hydrophosphates to Improve Their Electrophysical Properties

The mechanochemical activation of zeolite (clinoptilolite and clinoptilolite–stilbite) rocks with acidic salts—sodium hydrogen phosphate and ammonium hydrogen phosphate—with the weight ratio of the initial components of 1 : 1 in an IVS-4 vibratory attritor (1500 rpm, 0.6 kW, specific power 4 W/g, steel grinding set) is studied. The structure, chemical and phase composition, and thermal stability of salt-modified zeolite samples are studied by infrared spectroscopy, atomic emission spectrometry, X-ray phase analysis, and differential scanning calorimetry. The specific volume resistance of pelletized samples is measured using a three-electrode circuit. It is established that the electrical conductivity of high-silica zeolite rocks modified with sodium and ammonium hydrophosphates is 2.2 × 10–6 up to 2.4 × 10–5 S m–1 at 25°C. It is shown that the mechanochemical activation of clinoptilolite and clinoptilolite–stilbite rocks with sodium hydrogen phosphate in a vibratory attritor at a mechanical energy dose of 2.4 kJ/g increases the conductivity of mechanically activated zeolites by factors of 140 and 470 at 25°C, and by factors of 30 and 490 at 100°C, respectively. This allows us to consider mechanochemical activation as a promising method for improving the electrical properties of mineral materials.

Evaluation of alkaline and acidic modification of NaY zeolite for enhancing adsorptive removal of diclofenac sodium from aqueous solution

In the present study, facile and cost-effective modification methods, including alkali treatment and acid treatment, were evaluated to improve the adsorption capacity of NaY zeolite for diclofenac sodium (DFS) elimination from the aqueous solution. The performance of unmodified NaY, sodium hydroxide treated NaY (SHT-Y), hydrochloric acid treated NaY (HAT-Y), and sulfuric acid treated NaY (SAT-Y) was compared, followed by optimization of sulfuric acid concentration since sulfuric acid was recognized as the preferred modifying agent. The modified NaY with a concentration of 0.1 M of sulfuric acid exhibited the highest adsorption capacity. Analyses of FE-SEM, EDS, FTIR, BET, and XRD were used to determine the characteristics of NaY and treated zeolites. All treatments changed the Si/Al ratio of NaY. Silanol and bridging hydroxyl functional groups were detected in all zeolitic samples. Acidic modifications enhanced the specific surface area of NaY more than the alkali treatment. The influence of the major factors on the DFS adsorption, including adsorbent dosage, contact time, pH of the solution, and initial concentration of DFS was investigated and optimized in detail. The maximum adsorption capacity was obtained at pH 11 at the equilibrium time of 180 min. The hydrogen bond formation and cation-π interaction were recognized as DFS adsorption mechanisms. From the results of kinetic studies, the Elovich model has better agreement with experimental data, suggesting that the adsorbent surface is energetically heterogeneous and chemisorption leads the DFS uptake onto the adsorbent, indicative of hydrogen bond formation. In accordance with the equilibrium modeling results, the Sips isotherm better expresses the DFS adsorption mechanism onto the surface of the modified zeolite. According to the Langmuir isotherm model, the maximum adsorption capacity obtained for 0.2 g/L of treated zeolite was 117.77 mg/g. Eventually, sulfuric acid treatment was found as an effective and facile method for enhancing zeolite performance in DFS removal from aqueous solution.

Preparing New Ceramic Membranes from Syrian Zeolite Coated with Silver Nanoparticles to Treatment Wells Water

As a result of the exacerbation of the problem of water pollution, research was directed towards studying the treatment using ceramic membranes, which proved to be highly effective in treating all water sources. The research aims to study the possibility of preparing a new type of ceramic membranes from Syrian zeolite that was not previously used in this field. In this research, ceramic membranes were prepared from Syrian raw zeolite in several stages. Zeolite sample was characterized, grinded, mixed with boric acid, pressed to form desks, treated thermally according to experiment program, finally coated with silver nanoparticles. Specifications of prepared membranes were determined according to reference methods, effectiveness of prepared membranes were tested in well water handling, that water sample was filtrated through prepared membranes, and then it type MAC, so removal degree was 100%, While removal degree was 97% for bacterial strains on Agar with type PCA, 93% on Agar with type PDA which were conformed to Syrian standard /45 /2007. Specifications of prepared membranes were determined according to reference methods, effectiveness of prepared membranes were tested in well water handling, that water sample was filtrated through prepared membranes, then it was Characterized after treatment. Results showed that prepared zeolite membranes were high effectiveness through decrease chemical and microbial pollutants which were conformed to Syrian standard /45 /2007

Evaluation of adsorption and mechanical strength of 13X zeolite mixtures with phyllosilicate binders using molecular dynamics simulation and positron annihilation spectroscopy

There is growing interest in developing zeolites with novel internal structures that have optimal adsorptive capacity and high mechanical strength, while offering advantages, such as being light weight. We integrate computational and experimental methods to explore the effect of binder/zeolite types, and weight percentages on the mechanical strength of 13X zeolite and adsorption capacities of N2, H2O, and CO2 for additive manufacturing (AM) applications with the goal of maximizing both adsorption and strength. Zeolite 13X mixtures and phyllosilicate binders (either bentonite or kaolin) are combined using molecular dynamics (MD) simulations to create structures with various binder/zeolite weight percentages. Adsorption capabilities and mechanical strength are assessed using the grand canonical Monte Carlo (GCMC) and ReaxFF modules, respectively. Our modeling shows that an optimized zeolite/binder ratio for N2 adsorption is around 15 wt% for kaolin and roughly 10 wt% for bentonite. The resulting parameters can be applied to facilitate macro-scale computational fluid dynamics (CFD) and finite element method (FEM) simulations of an AM zeolite structure. We also performed Positron Annihilation Lifetime Spectroscopy (PALS) measurements on zeolite samples to explore the effect of changes in the internal volume. The results show an inverse relationship between the free volume and the solid loading. Adding a binder changes the morphology of the zeolite-binder compound and decreases open-volume area significantly.

Improved Catalytic Performances of the NaOH-Treated ZSM-22 Zeolite in the 1-Butene Skeletal Isomerization Reaction: Effect of External Acid Sites.

In this paper, a series of alkaline-treated ZSM-22 zeolite samples were prepared by treating the parent ZSM-22 zeolite using NaOH aqueous solution with different concentrations. By investigating the effects of alkaline treatment on the parent ZSM-22 zeolite, we discovered that the alkaline treatment contributed to the reduction of Brønsted acid sites due to the coverage of extra-framework Al on its external surface. In addition, it was found that the alkaline-treated samples were favorable to the improvement of the isobutene yield and selectivity, while these features appeared to be low for the subsequent acid-washed counterparts in the skeletal isomerization reaction of 1-butene. These results indicate that the catalytic performance of ZSM-22 zeolite is related to reduced amounts of Brønsted acid sites in it. To further reveal the reasons for the promoted catalytic performances of the alkaline-treated ZSM-22 series zeolites, we studied the properties of coke deposited on the two series of samples using Raman spectroscopy and thermogravimetric analysis and mass spectrometry (TG/MS-TPO). It was shown that the carbon deposited on the alkaline-treated series samples was mainly distributed at the outer surface, while the coke was distributed to a relatively lesser extent at the exterior surface for the acid-washed series samples. Moreover, by partially passivating outer acid sites of the parent zeolite, the selected alkaline-treated zeolite, and acid-washed zeolite, their isobutene selectivities were all improved with the decrease in outer acid sites. These phenomena confirmed that the improved catalytic performances of the alkaline-treated samples are related to their decreased external Brønsted acid site density, which further demonstrated that the high isobutene yield and selectivity in the skeletal isomerization reaction of 1-butene is realized via the monomolecular reaction pathway of 1-butene.

Using Zeolites to Cold Stabilize White Wines

Background and Aims. Tartrate stabilisation is a necessary step in commercial wine production. The traditional method to prevent crystallisation and precipitation of potassium bitartrate (KHT) after a wine is bottled is by adding seed KHT crystals to wine stored in a tank and holding temperatures below 0°C for a set period of time before bottling. This process requires time and energy and a filtration step to remove sediment. However, compared to other technical solutions such as reverse osmosis, electrodialysis, or ion exchange, it is still the most economical stabilisation option. This work aims to evaluate the ability of zeolites to cold stabilize white wines. Since zeolites can also remove proteins and thus heat-stabilize white wines, the new process can potentially combine heat and cold stability in a single treatment. Methods and Results. Effective tartrate stabilisation was achieved by mixing a natural zeolite sample with white wine for three hours. Although the quantum of required zeolite was larger than bentonite, zeolite did not exhibit shrink-swell behaviour, thus enabling greater wine recovery and capacity to be regenerated. Effective heat and cold stability could be achieved using a low-calcium zeolite as a processing aid in a single treatment. To avoid aluminium leaching and elevated aluminium concentrations in the treated wine, the zeolite was calcinated before being added to the wine. The calcination process also reduced calcium content in the wine after treatment with zeolite, thus eliminating the risk of calcium instability. Conclusions. The application of zeolite as a processing aid can potentially be effective in cold-stabilizing white wines and removing proteins responsible for haze formation. Significance of the study. Zeolites may constitute an alternative technology in white wine production facilitating heat and cold stabilisation in a single treatment.

NO adsorption/desorption pathways over Pd/SSZ-13 low temperature NOx adsorbers investigated by operando FT-IR spectroscopy and microreactor study

In this study a Pd-doped SSZ-13 zeolite sample is synthesized, characterized and evaluated for potential use in the low-temperature NOx adsorption. TEM/HR-TEM and in-situ CO/NO adsorptions followed by FT-IR spectroscopy are used to gain information on the nature and accessibility of the Pd sites. It is found that over the calcined sample Pd is present as isolated Pd+ and Pd2+ cations formed by ion exchange with the Brønsted acid sites of the zeolite, and as Pd+ and Pd2+ species belonging to PdOx particles on the external surface of the zeolite. Isolated Pd2+ ions prevail on the calcined fresh sample. The NOx adsorption/desorption performances, investigated by microreactor studies and operando FT-IR under relevant operating conditions, indicate that significant amounts of NO are stored on the catalyst (i.e. ca. 80–95 μmol/gcat of NOx in the temperature range 50–150 °C) which suggests the participation in the NOx uptake of both isolated Pdn+ sites and PdOx particles. NO is adsorbed as nitrosyls (anhydrous and hydrated) over both Pd2+ and Pd+; at low temperatures the formation of nitrates is also observed. The NO uptake as nitrosyls occurs with evolution of NO2 according with a NO storage mechanism which implies (i) the initial adsorption of NO on Pd2+, followed by (ii) the reduction of Pd2+ to Pd+ by NO accompanied by NO2 release and eventually (iii) the adsorption of NO on Pd+. The suggested interconversion of Pd2+ into Pd+ during NO adsorption is herein discussed based on FT-IR evidences. The stored NOx species are decomposed upon heating; nitrates are responsible for low temperature NOx desorption (below 200 °C), whereas nitrosyls show much higher stability and lead to a high temperature NO desorption (above 200 °C). The presence of NO2 in the feed stream increases the NOx adsorption capacity and results in the formation of mainly surface/bulk nitrates and nitro-compounds at the expense of nitrosyls.

Performance of clinoptilolite zeolite after milling as a pretreatment on hydration kinetics, shrinkage, and alkali-silica reaction of cementitious materials

Natural clinoptilolite zeolite has been a popular supplementary cementitious material (SCM) due to its acceptable pozzolanic performance and the overall lower environmental footprint. Previous research established that milling is an effective pretreatment technique to further increase the pozzolanic reactivity of zeolitic tuffs leading to an increased specific surface area and amorphous contents. Therefore, the present study characterized the zeolite particles after ball milling for 1 and 3 h using phase analysis by X-ray diffraction (XRD), particle size distribution by laser diffraction, microstructural analysis by scanning electron microscopy (SEM), moisture absorption rate, and relative chemical dissolution. The performance of milled clinoptilolite zeolite as a SCM with the replacement of up to 20% portland cement was evaluated through hydration kinetics (heat of hydration, setting time, chemical shrinkage, degree of hydration), workability, compressive strength, autogenous shrinkage, drying shrinkage, and alkali-silica reaction (ASR). Results revealed that 1 and 3 h of milling led to an increased specific surface area, moisture absorption capacity, and relative dissolution of particles, but had no visible effects on the crystalline structure of zeolite particles compared to the unmilled zeolite particles. For the hydrated system, both 1 and 3-h milled zeolite increased the overall heat of hydration leading to an increased silicate and aluminate reaction along with the acceleration effects in the setting time. The compressive strength of up to 20% milled (1 and 3 h) zeolite samples was increased by about 20 to 25% compared to the unmilled zeolite samples at an early age which suggested an increasing pozzolanic response of milled zeolite particles in the system due to an increased volume of hydrated phases and degree of hydration. Milling slightly decreased the workability by demanding a higher content of fresh water which was released at a later age leading to a higher drying and autogenous shrinkage. In addition, milling reduced the internal curing capacity leading to damage to the porous structure of zeolite particles. The use of up to 20% 3-h milled zeolite reduced the deleterious expansion by about 80% due to ASR compared to the control sample and the overall performance of milled clinoptilolite zeolite as the SCM was satisfactory in the hydrated system.

One-pot lower olefins production from CO2 hydrogenation

In this work the one-pot conversion of CO2 into lower olefins is investigated over a physical mixture of a methanol synthesis catalyst and a methanol-to-olefins (MTO) zeolite. First, the feasibility of the single reactions is tested at CO2 to olefins conditions, i.e., high temperature and high H2/CO2 pressure, providing insights on the reaction mechanism and catalyst stability. The effects of the operating conditions are then analyzed over the individual samples, starting from CO2/H2 mixtures in the case of the methanol synthesis catalyst and from methanol in CO2/H2 in the case of the zeolite. The In2O3-ZrO2 catalyst exhibits very good selectivity to methanol and high activity, reaching thermodynamic equilibrium above 380 °C. The zeolite sample showed high activity as well and the presence of high H2 partial pressure consistently increases the zeolite lifetime at high temperatures, but also the paraffin selectivity at the expense of the olefins, especially at low space velocity. It is therefore clear that a trade-off should be identified when testing the bi-functional catalytic samples in order to guarantee high methanol formation and good olefins production in the one-pot process. Finally, a comparison between methanol-mediated and modified Fischer-Tropsch (MFT) routes is presented, highlighting strengths and weaknesses of each reaction pathway. In particular, CO must be reduced in the methanol-mediated route, while methane and C5+ hydrocarbons formation is the main issue for the MFT reaction.

Evidence of Synergy Effects between Zinc and Copper Oxides with Acidic Sites on Natural Zeolite during Photocatalytic Oxidation of Ethylene Using Operando DRIFTS Studies

In this article, the role of surface sites of modified zeolites with semiconductor nanoparticles as alternative photocatalyts for protecting post-harvest foodstuff from the detrimental effects of ethylene is addressed. Two single and one double catalyst based on zinc and copper oxides supported over modified zeolite samples were prepared. Physical, chemical, and surface properties of prepared materials were studied by several characterization methods. UV-Vis absorption spectra show that the applied modification procedures increase the optical absorption of light in the UV and visible regions, suggesting that an increase in the photocatalytic activity could take place mainly in the obtained co-impregnated catalyst. An ethylene conversion around 50% was achieved when the parent natural zeolite support was modified with both transition metal oxides, obtaining higher removal efficiency in comparison to single oxide catalysts. Adsorption and photocatalytic oxidation experiments were also performed using single and double catalysts supported over fumed silica, attaining lower ethylene conversion and thus highlighting the role of zeolite surfaces as adsorption sites for ethylene during photocatalytic reactions. Operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) studies reveal that a synergistic mechanism occurs, involving ethylene adsorption at acidic sites of zeolite and its photocatalytic oxidation due to the generation of radicals by the light activation of nanoparticles of zinc and copper oxides.

Characterization of Zeolite ZSM-5 Synthesized from Kaolin and TPABr Using X-Ray Diffraction and Infrared Spectroscopy

Kaolin with alumina and silica content is used as the main material in this research to study the synthesis of ZSM-5 zeolite. The hydrothermal process was carried out through different aging times, namely 12, 24 and 36 hours. Tetrapropyl ammonium bromide (TPABr) was used as a template for the Mobile Five-1 (MFI) structure guide. X-ray diffraction (XRD) and infrared spectroscopy (FTIR) instruments were used to characterize the ZSM-5 zeolite formed from the synthesis results. This was done to identify the phase change from kaolin to zeolite ZSM-5. The results of the analysis using XRD for all samples showed a characteristic peak of the ZSM-5 zeolite at 2θ around 7.88°; 8.72° ;23.09°; 23.84° and 24.32°. However, samples with an aging time of 12 hours also showed peaks at 2θ around 15.84° and 26.03° which indicated an analsim phase. The absorption bands from the FTIR characterization for all samples are seen at wave numbers around 453, 542, 793, 1088 and 1221 cm−1 which are the characteristic peak points of ZSM-5 zeolite. The longer the aging time indicates that the crystallinity of the ZSM-5 zeolite is increasing. The highest crystallinity was obtained from ZSM-5 zeolite samples which were aged for 36 hours. This indicates an increasing number of ZSM-5 crystal nuclei with high purity because there is no other phase besides the ZSM-5 phase.

Preparation, Characterization, and Performance of Natural Zeolites as Alternative Materials for Beer Filtration.

The clarity of the beer is essential to its marketability and good consumer approval. Moreover, the beer filtration aims to remove the unwanted constituents that cause beer haze formation. Natural zeolite, an inexpensive and widespread material, was tested as a substitute filter media for diatomaceous earth in removing the haze constituents in beer. The zeolitic tuff samples were collected from two quarries in Northern Romania: Chilioara, in which the zeolitic tuff has a clinoptilolite content of about 65%, and the Valea Pomilor quarry, containing zeolitic tuff with a clinoptilolite content of about 40%. Two-grain sizes, <40 and <100 µm, from each quarry were prepared and thermally treated at 450 °C in order to improve their adsorption properties and remove organic compounds and for physico-chemical characterization. The prepared zeolites were used for beer filtration in different mixtures with commercial filter aids (DIF BO and CBL3) in laboratory-scale experiments, and the filtered beer was characterized in terms of pH, turbidity, color, taste, flavor, and concentrations of the major and trace elements. The results showed that the taste, flavor, and pH of the filtered beer were generally not affected by filtration, while turbidity and color decreased with an increase in the zeolite content used in the filtration. The concentrations of Na and Mg in the beer were not significantly altered by filtration; Ca and K slowly increased, while Cd and Co were below the limits of quantification. Our results show that natural zeolites are promising aids for beer filtration and can be readily substituted for diatomaceous earth without significant changes in brewery industry process equipment and protocols for preparation.

Environmental Applications of Zeolites: Hydrophobic Sn-BEA as a Selective Gas Sensor for Exhaust Fumes

Environmental monitoring of pollutants, such as NOx and COx, which can be facilitated by a range of gas sensors, is of considerable fundamental and practical importance. This work has been focused on the synthesis and evaluation of zeolite β with tin (Sn-BEA) and dealuminated β (DeAl-BEA) zeolites. The zeolite samples have been extensively investigated by IR, UV-VIS and NMR spectroscopy, XRD, TGA, and N2 adsorption-desorption. The prepared Sn-BEA sample is characterised by the submicron particle size, an almost defect-free structure, and high hydrophobicity. Sensors containing selective microporous layers based on Sn-BEA and DeAl-BEA zeolites have been prepared and extensively tested. Both the Sn-BEA and DeAl-BEA zeolites have been deposited in thin films and evaluated as gas sensors for CO, CO2, NO, and NO2 in the presence of water vapour at room temperature. The Sn-BEA zeolite-based sensor showed high selectivity towards NO2, while the DeAl-BEA is selective towards CO2 and NO2.

Preparation and modification of zeolite A from kaolin for catalytic methanation of carbon dioxide

AbstractDifferent types of zeolite including Zeolite A are prepared from natural kaolin originated in Vietnam. Raw kaolin was collected from Phu Tho, Vietnam, underwent metakaolization at 650 °C within 2 hours and alkalination with NaOH to synthesize various zeolitic samples. Various characterization techniques were performed, including X‐ Ray Diffraction, Fourier‐transform infrared spectroscopy, and Scanning Electron Microscopy. Different concentrations of NaOH were utilized to study the difference of the prepared zeolite. Nickel‐doped zeolite A samples with different nickel loading were also prepared via ion exchange method and were employed as catalyst for the hydrogenation of carbon dioxide (CO2) to obtain methane (CH4). The best catalytic activity of 55.2 %CO2 conversion and 92.7 %CH4 selectivity was achieved with 10 %Ni/ZM1 at 350 °C, 1 atm, H2:CO2 ratio of 4:1, and gas hourly space velocity of 9,000 mL.g‐1.h‐1. This study demonstrates a promising pathway of modifying Vietnamese natural kaolin as a low‐cost but an effective alternative material for the preparation of zeolite A and its application in the carbon dioxide methanation reaction.

MORPHOLOGYCAL, ELEMENTAL CONTENT, AND PHYSICAL PROPERTIES OF CLEANED CLINOPTITOLITE ZEOLITE (10X) USING SONICATION AND MICROWAVE

This research was conducted to determine the morphology, elemental content and physical properties of the zeolite samples before and after cleaning. The characterization used in this study is the Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX). Based on the results of SEM-EDX, it was shown that the 200 mesh zeolite sample and the zeolite that passed the filter had a non-spherical particle shape and no visible pores on the surface, while the microwave zeolite sample had an aggregate shape and visible pores on the particle surface which were very clear. In addition, in the 200 mesh zeolite sample, filtered zeolite and microwave zeolite each had an Al content percentage of 1.64%, 3.18 and 3.80% and a Si content of 7.58%, 15.15% and 18 .38%.

Quantitative 67Zn, 27Al and 1H MAS NMR spectroscopy for the characterization of Zn species in ZSM-5 catalysts.

67Zn MAS NMR spectroscopy was used to characterize the state of Zn in Zn-modified zeolites ZSM-5. Two 67Zn enriched zeolite samples were prepared: by solid-state exchange with metal 67Zn (Zn2+/ZSM-5 sample) and by ion exchange with zinc formate solution (ZnO/H-ZSM-5 sample), both containing ca. 3.8 wt% Zn. The elemental analysis, TEM, and quantitative BAS and aluminum analyses with 1H and 27Al MAS NMR have shown that Zn2+/ZSM-5 contains zinc in the form of Zn2+ cations, while both ZnO species and Zn2+ cations are present in ZnO/H-ZSM-5 besides BAS. 67Zn MAS NMR has detected the signal of Zn in a tetrahedral environment from ZnO species for both the activated and hydrated ZnO/H-ZSM-5 zeolite. The signal of Zn in an octahedral environment was detected for the hydrated Zn2+/ZSM-5 and ZnO/H-ZSM-5 zeolites. This signal may belong to zinc cation [HOZn]+ or Zn(OH)2 species surrounded by water molecules. Quantitative 67Zn MAS NMR analysis has shown that only 27 and 38% of zinc loaded in the zeolite is visible for the activated and hydrated ZnO/H-ZSM-5 zeolite, and 24% of Zn is visible for the hydrated Zn2+/ZSM-5. Zinc in the form of ZnO species is entirely visible in both the activated and hydrated ZnO/H-ZSM-5 zeolite, while Zn2+ cations are not detected at all for the activated sample and only 29% of Zn2+ cations is visible for the hydrated zeolite. Detection of only a part of Zn2+ cations in the form of [HOZn]+ or Zn(OH)2 species in octahedral environment presumes only partial hydrolysis of the bond of Zn2+ cation with framework oxygen and further solvation of the Zn species formed at hydrolysis by the adsorbed water.