Zeolite Particle Size Research Articles

Preparation of zeolite-based zirconium functional materials (Ze-Zr) with the aid of response surface methodology

Abstract Zeolite-based zirconium functional materials (Ze-Zr) were obtained by the response surface methodology (RSM). The experimental conditions such as zeolite particle size, the concentration of zirconium oxychloride, mass ratio of zeolite and zirconium, processing time and temperature and assimilation temperature were optimized. The central Box–Behnken design (BBD) and mathematical modelling were adopted for optimizing experimental parameters. FT-IR, XRD and SEM were used to analyze the structure and morphology of the obtained Ze-Zr materials. The Ze-Zr materials with highest phosphorus removal rate of 97.08% were prepared under the following conditions: 0.15–0.20 mm of zeolite, 0.04 M zirconium, mass ratio of 0.09 of zeolite and zirconium, processing for 4 h and 100 °C as drying temperature.

ZEOLITE PROCESSING AS HEAVY MATERIAL

Research on zeolite processing as a reinforcement material is done to utilize natural resources in North Sumatera Province. Zeolite processing is so nanometer-sized by using a ballmill. Activation of zeolite is done by heating 1050 C for 10 minutes. The resulting zeolite particle size is 290 nanometers. It is obtained from 80 grams of zeolite measuring 1700 nanometers to 15 grams measuring 290 nanometers for 34 hours of grinding process in the ballmill.

Effects of the zeolite particle size on the charge separated states

Electron transfers occurring after sorption and photoexcitation of p-terphenyl molecules in the porous void of two MFI type zeolites were investigated. The influence of the morphology and particle size, i.e.; nanosheets and conventional coffin-shaped micron sized crystals (big crystals) on these phenomena were emphasized. The irradiation of PTP occluded in big crystals induces the formation of a radical cation which evolves to an electron-hole pair through the capture of another electron of zeolite. In contrast, if photoexcitation of PTP incorporated in nanosheets induces also radical cation, it is interesting to note that the electron-hole pair formation is not favored in such environment. The absence of charge compartmentalization within nanosheets is put forward to explain the inhibition of electron transfer to create the charge transfer complex. Indeed, the small thickness of nanosheets prevents electron hopping over long distance after ionization and consequently, as the electron is trapped nearby the radical cation, direct recombination is favored.

Synthesis and characterization of MFI-type borosilicate zeolites and evaluation of their efficiency as drug delivery systems

MFI-type borosilicate zeolites with different Si/B ratio were synthesized by hydrothermal method using silicic acid and sodium tetraborate decahydrate as starting materials. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry analysis (TGA/DTG) and Fourier transform infrared spectroscopy (FT-IR). Different characterization techniques confirmed the incorporation of boron atoms into the zeolite framework. SEM images revealed that the particle size of zeolites and their morphology can be controlled by different synthesis parameters. The effect of different parameters such as crystallization time and temperature, pH value of initial gel and Si/B ratio on the crystallinity, morphology and incorporation of boron atoms into final products was investigated and discussed in detail. The efficiency of synthesized borosilicate zeolites as drug delivery systems was examined by loading and in vitro release of anticancer drug doxorubicin (DOX). The results demonstrated that DOX-loaded borosilicate samples show a pH-sensitive drug release feature with higher drug release rate in relatively lower pH values. In vitro cytotoxicity of DOX- loaded borosilicate was evaluated by MTT assay.

Nanosized Particles of X Zeolite Containing Ammonium Cations as Basic Catalysts

There is great interest in reducing the size of zeolite particles, because this can improve their catalytic properties in various reactions. This work evaluates two faujasite-type X zeolites, one micrometric and one nanometric. Zeolites in the sodium form were exchanged ionically with methylammonium cations. The materials were then evaluated as catalysts in the Knoevenagel condensation reaction. Steric impediments restricted ion exchange in the micrometric zeolite and became more important with increasing cation volume. In the case of the nanometric sample, such impediments were less evident, because the smaller particle size provided greater access of exchanger cations, compared to the micrometric zeolite in which the sodium was inaccessible. The best catalytic performances were achieved with zeolites containing the monomethylammonium cation. The increased accessibility and diffusion of the reactants and products through the pores of the nanometric zeolite provided the best butyraldehyde conversions, independent of the exchanger cation. In order to increase accessibility to catalytic sites, several studies have been carried out in order to reduce the diameter of the particles of zeolites to the nanometer scale. This reduction can promote the increase in the activity of the catalysts in some reactions. In order to increase accessibility to catalytic sites, several studies have been carried out in order to reduce the diameter of the particles of zeolites to the nanometer scale. This reduction can promote the increase in the activity of the catalysts in some reactions.

Gas and water vapor transport properties of mixed matrix membranes containing 13X zeolite

Mixed matrix membranes (MMM) containing 13X zeolite particles were prepared to study the impact of hydrophilic inorganic component on membrane gas and water vapor transport properties. Rubbery ethylene-vinyl acetate copolymer (EVA), hydrogenated nitrile rubber (HNBR), and glassy polysulfone (PSF) varying in permeability were selected as membrane matrices. The incorporation of 13X decreased gas permeability of all MMMs and had only a marginal effect on ideal selectivity (e.g. 20wt% loading reduced N2 permeability by 21%, 19%, and 4% for PSF, EVA, and HNBR, respectively). The observed trend was in agreement with the diminished free volume size obtained from the positron annihilation lifetime spectroscopy (PALS) measurements suggesting pore blockage. In contrary, water vapor permeability through all MMMs was significantly enhanced by zeolite filling (e.g. 30wt% loading increased H2O permeability by 153%, 34%, and 22% for PSF, EVA, and HNBR, respectively). This was explained as due to the increased water solubility documented by the sorption results, that compensates for the effect of the reduced water diffusivity in MMMs. The variations in MMMs permeabilities were also found to depend on zeolite particle size and its porosity. Two opposite effects were noticed of increased water vapor permeability and decreased gas permeability for MMMs filled with smaller but more porous particles. The water permeation through PSF based membranes may cause debonding at the particle/matrix interface and deterioration of the MMMs properties as indicated by their enhanced gas permeability and reduced selectivity.

Nano size Hβ zeolite as an effective support for Ni and Ni[sbnd]Cu for COx free hydrogen production by catalytic decomposition of methane

Mono and bimetallic catalysts of Ni and Cu on Hβ zeolite supports were tested for the COx free hydrogen production by decomposition of methane. The effect of Cu addition and the support particle size were investigated. XRD analysis of the reduced samples demonstrated that for catalysts based on nano-sized Hβ zeolite particles (nano-Hβ), the Ni and Cu were only present in the form of a NiCu alloy, whereas when commercial Hβ zeolite (Hβ) was used; segregated Cu0 and Ni0 species were also observed. Addition of Cu was found to dramatically improve the H2 yield by the formation of surface NiCu alloys. The particle size of the Hβ zeolite has a pronounced effect on the Ni and NiCu dispersion, and consequently on the methane decomposition activity. The surface area of NiCu on the nano-Hβsurface was estimated by a combination of H2 pulse chemisorption and N2O titration methods. The Cu species in close proximity to Ni sites inhibited carbon deposition at the Ni sites, resulting in higher rates of H2 formation. Consistent with this finding, NiCu/nano-Hβ was the most active of the catalysts tested. The physicochemical characteristics of the commercial and nano-Hβ supported Ni and/or NiCu catalysts are rationalized by TEM, H2-TPR, XPS and Raman spectroscopy in conjunction with H2 production rates.

The role of pore diffusion in determining NH3 SCR active sites over Cu/SAPO-34 catalysts

Cu/SAPO-34 catalysts have been extensively investigated recently for NOx selective catalytic reduction (SCR) reactions. Due to the small pore size (4.3Å) of the zeolites, it is a natural concern that the reaction rates might be dictated by the pore diffusion regime rather than the intrinsic kinetics. In this work, a series of Cu/SAPO-34 catalysts, with identical Cu ion active site loadings but varying zeolite particle sizes (1–9μm), were evaluated. A variety of characterization techniques (XRD, BET, H2 TPR, and NH3 TPD) have confirmed that the same copper species and surface chemistry existed in these samples despite the different SAPO-34 particle sizes. While the Thiele modules governing the pore diffusion effects were vastly different, up to nine times, these samples shared a similar turnover frequency (TOF) and apparent activation energy (44.8±3.0kJ/mol) for the NH3 SCR reaction. These results unequivocally conclude that under the representative SCR reaction conditions investigated in this work, the reaction rates on Cu/SAPO-34 powder catalysts are kinetically controlled and pore diffusion plays little role in disguising the intact intrinsic activity per single-site copper.

Insecticidal potential of zeolite formulations against three stored-grain insects, particle size effect, adherence to kernels and influence on test weight of grains

Laboratory studies were conducted in order to evaluate the insecticidal potential of three commercially available zeolite formulations against adults of Sitophilus oryzae, Tribolium confusum and Oryzaephilus surinamensis in wheat. For each zeolite formulation, three particle size levels were tested, i.e. 0–50, 0–150 and 0–500 μm. Zeolites were applied at three dose rates, 250, 500 and 1000 ppm, and insect mortality was assessed after 2, 7, 14 and 21 d of exposure. After the final mortality count, dead and alive insects were removed and offspring numbers were determined following an additional period of 65 d. In another series of laboratory bioassays, the effect of zeolite application on the test weight of wheat, maize and barley, as well as the adherence of zeolite particles to wheat, maize, barley and rice kernels was also measured. Oryzaephilus surinamensis was the most susceptible species to zeolite application, regardless of the zeolite formulation, dose and particle size level tested, whereas T. confusum was the most tolerant. No significant differences in efficacy were recorded among the three tested zeolite formulations. At the same time, particle size did not affect zeolite efficacy, at least for the particle size levels tested. All zeolites caused a significant reduction on the test weight of the treated grains. Moreover, zeolite particles showed different adherence among wheat, maize, barley and rice kernels. The results of the present study indicate that zeolites can be used with success as grain protectants, but there is a considerable effect on some physical properties of the grains. This information aims to encourage further evaluation of zeolites as grain protectants.

Influence of zeolite shape and particle size on their capacity to adsorb uremic toxin as powders and as fillers in membranes.

Membranes with zeolites are promising for performing blood dialysis because zeolites can eliminate uremic toxins through molecular sieving. Although the size and the shape of zeolite particles can potentially influence the performance of the membranes with respect of creatinine uptake level, it is not clear what sizes and shapes lead to better performance. In this paper, we carry out experiments to answer this question. Spherical microparticle 840, spherical nanoparticle P-87 and rod-like nanoparticle P-371 zeolites were chosen to be used in all the experiments. Their creatinine uptake levels were first measured as powders in creatinine solutions with different concentrations, volumes and adsorption times. Then, nanofibrous membranes with zeolites were electrospun and their ability to adsorb creatinine was measured and compared against their respective powders' creatinine uptake level. The experiment shows that the zeolites have similar creatinine uptake ability as powders. However, they have significantly different creatinine uptake ability after being incorporated inside the membranes. Spherical microparticle 840 in the membrane presented the best creatinine uptake ability, at 8957 µg g-1 , which was half of its powders'. On the other hand, P-87 presented largely decreased, while P-371 presented even lower creatinine uptake ability in membranes when compared to respective powders'. The results shows that microparticle and sphere shaped particles perform better inside the membranes. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1594-1601, 2017.

Wet gringing of zeolite in stirred media mill

In the present study the results of systematic experimental series are presented with the specific goal of optimizing the zeolite nanoparticles' production using a wet stirred media mill. The diameter of the grinding media as well as the rotor velocity were varied in the experiments. Particle size distribution and "outer" specific surface area of the ground samples were measured by a laser particle size analyser. Additionally, BET, XRD and FT-IR analyses were performed for the characterization of the "total" specific surface area as well as the crystalline and material structure, respectively. Based on the results of the laboratory experiments it was found that wet stirred media milling provided significant reductions in the particle size of zeolite. Furthermore, the crystallinity of the samples also decreased, so not only the physical but the mineralogical characteristics of zeolite can be controlled by stirred media milling.

Direct dimethyl ether synthesis from syngas on copper–zeolite hybrid catalysts with a wide range of zeolite particle sizes

This paper reports on direct dimethyl ether synthesis from syngas on hybrid bifunctional copper–zeolite catalysts. Both laboratory synthesized and commercial zeolites were used in this work. The catalyst performance is evaluated under pressure in a continuous fixed bed milli-reactor. The relationships between zeolite particle sizes, acidity and catalytic performance of the hybrid catalysts in dimethyl ether synthesis have been studied. The catalysts and catalyst precursors were characterized using a wide range of characterization techniques: nitrogen adsorption–desorption measurements, X-ray diffraction, 27Al NMR, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy with adsorbed molecular probes.It is found that the reaction rate in direct dimethyl ether synthesis is strongly affected by the sizes of zeolite particles. The hybrid catalysts containing small individual nanosized zeolite particles (60–100nm) were much active than their counterparts with intergrown crystal agglomerates. The phenomenon is interpreted in terms of enhanced transport of methanol from the copper catalyst to the acid sites in the small zeolite particles with a shift of the thermodynamic equilibrium. The catalyst deactivation was attributed to copper sintering in the presence of the acid sites on the external surface of zeolites. It is established that the catalyst deactivation is less significant with the catalysts containing ZSM-5 zeolites with lower concentration of acid sites on the zeolite external surface. A new methodology to enhance the catalytic performance and stability of copper–zeolite hybrid catalysts for direct dimethyl ether synthesis is proposed.

Static in-situ hydrothermal synthesis of small pore zeolite SSZ-16 (AFX) using heated and pre-aged synthesis mixtures

The conditions of static in-situ hydrothermal synthesis were optimized to prepare crystalline, pure phase and template-free small pore zeolite SSZ-16 (AFX) particles. The type of silica source and prolonged ageing process at an elevated temperature were decisive in obtaining pure phase zeolite SSZ-16 particles under static conditions and conventional heating. Colloidal and fumed silica-based synthesis mixtures were successful in forming the zeolite SSZ-16. The zeolite particle size was reduced from 46 to 5 μm when the fumed silica was replaced by colloidal silica. Uniform, fine-grained and fully crystalline zeolite SSZ-16 particles were synthesized only from the colloidal silica-based mixtures that were aged at 80 °C for 7 days. The elevated temperature of the ageing stage is supposed to promote nucleation of viable nuclei leading to the reduction of the induction period. The two cycle calcination procedure with maximal temperature of 550 °C, ensured the removal of template molecules from the bulk phase of zeolite SSZ-16 particles. Carbonaceous residua were observed in zeolite subsurface region and mainly in the core shell morphology of zeolite SSZ-16 particles. The phase purity of zeolite SSZ-16 particles was checked by XRD and sorption properties were determined by N2 adsorption at −196 °C. Zeolite SSZ-16 particles showed the micropore volume of 0.24 cm3/g and BET surface area of 496 m2/g.

Mixed matrix membrane of nano-zeolite NaX/poly (ether-block-amide) for gas separation applications

In this work, mixed matrix membranes (MMMs) were prepared by incorporating nano-zeolite NaX into poly (ether-block-amide) (Pebax-1657) as an active layer on the polyethersulfone (PES) membrane as a support layer. The influence of filler content, zeolite particle size and operating conditions on the gas separation performance of the prepared membranes were studied. In order to achieve this aim, the zeolite NaX nanoparticles, which were fabricated by the hydrothermal technique using microwave heating, were uniformly distributed in the polymer solution by a two-step procedure for preparation of the membrane casting solution and the mixed matrix membrane was fabricated via the phase inversion technique by solvent evaporation. The prepared membranes were characterized by the ATR-FTIR, AFM, SEM, DSC and contact angle analyses. The gas permeation results revealed that incorporation of nano-zeolite NaX into the Pebax-1657 membrane decreased the gas permeability for all tested gases, while the ideal selectivity for CO2/N2 and O2/N2 significantly enhanced. Also, the mixed matrix membranes containing nano-sized zeolite had superior gas separation performance in comparison with the micro-sized zeolite loaded membrane. It was found that the CO2/N2 selectivity enhanced from 98.0 to 121.5 with increasing the feed pressure, while the O2/N2 selectivity decreased from 7.8 to 4.2. For CO2/N2 separation, the membrane containing 2wt% nano-zeolite at the operating pressure of 7bar and temperature of 25°C overcomes the Robeson's upper bound and showed fairly good gas separation performance, compared with the similar Pebax mixed matrix membranes in the literature.

Cost-effective two-stage varying-temperature rapid crystallization of zeolite T and SAPO-34

In this paper, zeolite T and SAPO-34 have been synthesized by two-stage varying temperature crystallization method (TVTC method). The feature of this method is dividing the hydrothermal process into two steps. The first step is lower temperature treatment which is favorable for the crystals nucleation and the second step is higher temperature treatment which is helpful to the crystals growth. The advantage of this method is that it greatly reduces the crystallization time and particle size compared to conventional constant temperature crystallization method (CCTC method). The influences of different initial and final temperatures on the zeolite crystallinity, morphology and particle size have been investigated in detail. Ultimately, the optimal crystallization conditions of zeolite T and SAPO-34 using this method have been summarized. The samples prepared with TVTC method and CCTC method also have been contrasted. With TVTC method, the synthesis time of zeolite T crystals is reduced from 7 days to 4 days and the synthesis time of SAPO-34 crystals is reduced from 48h to 16h. Furthermore, the sample prepared by TVTC method has higher crystallinity compared with the sample prepared by CCTC method. The particle size distributions of samples prepared by two methods have strongly confirmed that TVTC method is beneficial to form uniform and small zeolite particles. This paper provides an efficient and economical route to the industrial preparation of zeolite T and SAPO-34.

Removal of methylene blue from water using zeolites prepared from Egyptian kaolins collected from different sources

Na-Y Zeolites prepared from local Egyptian kaolins were investigated as adsorbents to remove methylene blue (MB) from aqueous solutions. Three Egyptian kaolins, KS, KD and KK were collected from Saint Catherine, Dehessa and Kalabsha, respectively. The influences of the chemical composition of kaolin ores and the surface properties of the prepared zeolites on the adsorption processes have been studied. The effects of various parameters such as surface area, particle size, initial MB concentration, contact time, adsorbent concentration and successive adsorption cycles were examined. Comparison with previous studies show satisfactory removal performance for MB as compared to other reported zeolites. The adsorption capacities of zeolite toward MB are mainly influenced by the particle size of zeolites rather than the zeolitic content. Zeolite samples with small particle size and high external surface area are recommended for the removal of MB.

Effect of Particle Size of NaX Zeolite on Adsorption of CO2/CH4

In the present work, the nano-NaX zeolite and micro-NaX zeolite were synthesized via hydrothermal method. Then, the adsorption capacities and isotherms of pure gases CO2 and CH4 on the synthesized zeolite nanoparticles were determined at three temperatures of 288, 298 and 308 K and various pressures from 1 up to 20 bar. Adsorption capacities of CO2 on the nano-sized zeolites NaX were showed to be higher than CH4. The selectivity of CO2/CH4 of the nano-sized zeolites NaX was 5.47 at 288 K and pressure about 20 bar. The results of the experimental data follows the Langmuir-Frendlich adsorption isotherm. Reduction of the particle size from micrometer to nanometer results in increasing the adsorption capacity for carbon dioxide on the X zeolite nanoparticles about 28% (from 5.067 to 6.536 mmol/g) at 288 K and 20 bar.

La zeolita y su efecto en la eficiencia del nitrógeno en arroz y maíz

Este trabajo evaluó el efecto de la zeolita en las reducciones de volatilización del nitrógeno amoniacal (RVNA) y volumen de lixiviados (RVL) así como en rendimientos de arroz Oryza sativa L. y maíz Zea mays L. En el primer experimento bajo un Diseño Completamente al Azar (DCA) se evaluó el tamaño de partícula de zeolita (< 1 mm, 1 - 2 mm, 2 - 3 mm y 3-5 mm) en RVNA. El segundo experimento, consistió en evaluar RVL con la aplicación de cuatro tratamientos: testigo (T), zeolita (Z), urea (U) y urea + zeolita (UZ). El tercer experimento se desarrolló en un cultivo de arroz, donde se evaluaron dos métodos de aplicación (al voleo y trasplante) con cuatro tratamientos (T, U, UZ10% y UZ15%) y su efecto en el rendimiento del cultivo. El cuarto experimento realizado en un campo de maíz con dos tratamientos (U y UZ15%) evaluó el rendimiento del cultivo en dos suelos (aluvial y esquelético). Los tamaños de partícula entre 3 y 5 mm obtuvieron RVNA del 50% y RVL del 48%. La aplicación de zeolita en arroz obtuvo RVNA de 60% y mejoró los rendimientos

Ultrafine nanocrystalline mesoporous NaY zeolites from fly ash and their suitability for eco-friendly corrosion protection

Fly ash, an industrial waste from coal based thermal power stations and a vast resource for silica and alumina, remains underutilized. It consists of polycyclic aromatic hydrocarbons, metals, silica etc. which are toxic in nature and silica has also been classified as a carcinogenic material. So a definite need is to make a proper use of the fly ash in order to convert it into useful materials possessing enormous functionality. Preparation of uniform nanocrystalline mesoporous NaY zeolites from fly ash without use of organic structural directing agents is reported for the first time. Different ratios of fumed silica are added to fly ash for preparation of NaY zeolites. The effect of amount of water used during the crystallization process on particle size of the zeolite is reported. Detailed characterization of the prepared zeolites is carried out using XRD, FTIR, SEM EDAX and DLS. Si/Al ratio was calculated using NMR and EDAX data. Porosity, pore size distribution and pore volume were determined using nitrogen adsorption data. The particle size of zeolites was found to be in the range of 400–670 nm whereas the crystallite size calculated from the XRD data was in 9–13.4 nm range. The synthesized zeolites are found to possess high crystallinity (90–93 %). Formation of octahedral crystals is confirmed by SEM observations. BET analysis shows high surface areas and presence of mesopores. IR and NMR spectroscopy confirms the formation of NaY with increased silica content. The prepared zeolites exhibited good ion exchange capacities which were found to decrease with increase in Si/Al ratio. Unlike the common applications of zeolites in catalysis where high purity is desirable, the fly ash based zeolites were exchanged with zinc metal ion and applied as pigment in anticorrosive paint formulations. Corrosion resistance was evaluated using electrochemical impedance spectroscopy measurements. The results indicate that metal exchanged zeolite possesses good anticorrosive property and can be used as an alternate to the conventionally used toxic, lead and chromate based anticorrosive pigments.

Does Particle Size of Clinoptilolite Zeolite Have a Role in Textural Properties? Insight through Differential Pore-Volume Distribution of Barret, Joyner, and Halenda Model

Analysis of differential pore-volume distribution (PVD) patterns of commercial clinoptilolite fractions [(<125 µ (Z8; fine), 125–250 µ (Z9; medium), and >250 µ (Z10; coarse)] has been conducted experimentally using an analyzer to measure the nitrogen (N2) adsorption isotherms. The differential PVDs of the clinoptilolite fractions were calculated from the hysteresis loop according to the adsorption and desorption curves of the Barret, Joyner, and Halenda (BJH) model. The adsorption and desorption cycles of BJH produced heterogeneous as well as dissimilar differential PVD patterns with assorted peaks. While the adsorption curve has prolonged up to 300 nm, the desorption cycle was confined up to 190-nm pore diameter only. In the adsorption cycle, all the clinoptilolite fractions displayed U-shaped curves and had a differential pore volume in the range of 3 × 10–3 to 8 × 10–3 cm3/g A° in the micropore region with a sole peak at 1.75 nm for the fine fraction (Z8). In contrast, the curves were linear in the mesoporous region for all the fractions, with the fine fraction (Z8) having the greatest differential pore volume, whereas the other two fractions were almost parallel to each other. The desorption cycle has revealed an inverted V-shape curve with no definite patterns for the microporous region. Although the adsorption cycle could ascertain the micropore region, the desorption cycle was unable to do so. It was apparent from the differential PVD of the BJH model that fraction size has a major role in determining the textural properties of clinoptilolite fractions.