Zeolite Composites Research Articles

Zeolite/ZnO composites based on a Cuban natural clinoptilolite and preliminary evaluation in methylene blue adsorption

Two composites based on a Zn2+ exchanged natural clinoptilolite and ZnO nanoparticles were obtained by mechanosynthesis and ‘in situ’ methods. Characterization of resulting materials was carried out using XRD, Raman spectroscopy, TGA, FE-SEM and N2 adsorption. XRD results showed that no significant changes in the crystalline structure of the zeolite took place due to the performed treatments. Thermogravimetric behaviour indicated a high thermal stability for all samples. Raman spectra exhibited the characteristic bands for clinoptilolite zeolite and ZnO reported in the literature and the RRUFF database. Morphology changes were observed between natural and exchanged clinoptilolite and the ‘in situ’ obtained composite. Textural analysis showed a decrease in surface area of ‘in situ’ composite compared with the exchanged zeolites, related to the partial nanoparticle deposition in the pore entrances. The adsorption studies of methylene blue in the zeolitic samples and composites showed that all evaluated materials were able to absorb the dye from aqueous solutions.

Preparation of magnetic zeolitic imidazolate framework-67 composites for the extraction of phthalate esters from environmental water samples

In this paper, magnetic ZIF-67 composites were prepared by an in situ method and utilized in the magnetic solid-phase extraction of phthalate esters. The obtained magnetic ZIF-67 composites were characterized in detail, and the adsorption performance was evaluated. The results showed that ZIF-67 crystals in the composites had a chamfered cubic shape with about 2.0 μm diameter and Fe3O4 was attached on the surface of ZIF-67. The parameters affecting magnetic solid-phase extraction efficiency were optimized including the adsorption and desorption conditions. Under the optimum conditions, magnetic solid-phase extraction coupled with gas chromatography-mass spectrometry for analyzing seven phthalate esters in environmental water samples was established. All the analytes exhibited good linearity (1-200 ng mL-1) with correlation coefficients higher than 0.9950. The relative standard deviations were between 4.3% and 8.9%. The developed method showed high sensitivity and had good potential for analyzing trace phthalate esters in water samples.

Synthesis of ZSM-5/SAPO-34 zeolite composites from LAPONITE® and their catalytic properties in the MTO reaction

ZSM-5/SAPO-34 zeolite composites were successfully synthesized via a secondary growth method, and the SAPO-34 part of ZSM-5/SAPO-34 was synthesized from LAPONITE®.

Tailoring hierarchical zeolite composites with two distinct frameworks for fine-tuning the product distribution in benzene alkylation with ethanol.

A hierarchical zeolite composite, MOR@ZSM-5, with two distinct frameworks has been successfully fabricated via the repeated crystallization of ZSM-5 nanocrystals on mordenite surfaces. To avoid their phase separation, the surface of mordenite was pretreated with tetra(n-butyl)ammonium hydroxide (TBAOH) to induce the formation of the ZSM-5 nuclei, and it was subsequently modified by the continuous growth of nanocrystalline ZSM-5 on the entire area of the mordenite surfaces. Interestingly, the fully overgrown MOR@ZSM-5 composite exhibits a remarkable improvement in the ethylbenzene selectivity (>60%) obtained from the alkylation of benzene with ethanol with respect to isolated zeolites and their physical mixture due to the enhanced external surface area and hierarchical porosity as well as the reasonable acidity provided by the fully dispersed ZSM-5 nanocrystals on the mordenite surfaces. Moreover, coke species deposited on the designed composites are likely located at the external surfaces and do not considerably deteriorate the catalytic performance, whereas they are deposited predominantly in the micropores over the incompletely overgrown MOR@ZSM-5 composite. The present study illustrates the advantages of the overgrown zeolite composites of two incompatible frameworks in tailoring the hierarchical porosity, adjusting the acidic properties, and eventually controlling the product selectivity in acid-catalyzed reactions such as the alkylation of benzene with ethanol.

Catalytic Hydroconversion of Ethanol-Soluble Portion from the Ethanolysis of Hecaogou Subbituminous Coal Extraction Residue to Clean Liquid Fuel over a Zeolite Y/ZSM-5 Composite Zeolite-Supported Nickel Catalyst

A novel and highly active zeolite Y/ZSM-5 composite zeolite (CZ)-supported nickel catalyst (Ni/CZ with 10% of Ni loading) was prepared by modified deposition–precipitation to uniformly disperse Ni ...

Synthesis of TiO2/Zeolite-A Composite for The Removal of Methylene Blue on Direct Sunlight

Wastewater generated from textile industry contains azo dye, (e.g., methylene blue), which is inefficient to decompose by using biological processes, and requires long treatment time. TiO2 is the most widely used adsorbent for industrial applications and photocatalytic degradation of various azo dyes in textile wastewater. Its anatase is the most effective and widely used photocatalyst, however the wide band gap of TiO2 has limited its widespread application in industry since it needs to be excited by ultraviolet (UV) light. In order to overcome this issue, combination of adsorbent zeolite and TiO2 into the composite was used in this study so that TiO2 can adsorb methylene blue under direct sunlight. Composition of 1 g TiO2 and 1 g Zeolite composite was used in batch method to eliminate different methylene blue concentrations, i.e., 25; 50; 75; 100; 125; 150; 200; and 250 ppm by means of adsorption process under direct sunlight. The experimental result showed that addition of zeolite was able to considerably improve adsorption capacity of TiO2 on direct sunlight in the range of 97.2 – 99.3 % of methylene blue removal. The highest removal was observed in the case of lower concentrations of methylene blue, i.e., in the range of 25-50 ppm.

Antireflection Enhancement by Composite Nanoporous Zeolite 3A-Carbon Thin Film.

A straightforward and effective spin-coating technique at 120 °C was investigated for the deposition of a thin nanoporous layer with antireflection properties onto glass and indium tin oxide (ITO) coated glass. A mixture of zeolite 3A powder and high iodine value vegetable oil was deposited, creating a carbonic paste with embedded nanoporous grains. Experimental results evidenced excellent broadband antireflection over the visible-near-infrared wavelength range (450–850 nm), with a diffuse reflectance value of 1.67% and 1.79%. Structural and optical characteristics stabilized over time. The results are promising for the accessible and cost-effective fabrication of an antireflective surface for optoelectronic devices.

ZIF-derived Co nanoparticle/N-doped CNTs composites embedded in N-doped carbon substrate as efficient electrocatalyst for hydrogen and oxygen evolution

Herein, we report a bifunctional electrocatalyst for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by pyrolysis of zeolitic imidazolate framework-67 (ZIF-67), melamine, and PVP composites solid gel. During the pyrolysis, ZIF-67 formed N and Co co-doped carbon nanotubes on the surface (Co@CNT/NC), melamine and PVP have been converted into N-doped carbon (NC) substrate. Our Co@CNT/NC composites display the overpotential of HER and OER at current density of 10 mA cm−2 only need 136 mV and 280 mV, respectively. The synergistic effect of catalytic active sites such as metallic Co, Co–N bond, and N-doped carbon, and the large specific surface area caused by special morphology of the materials, enabled the catalysts to exhibit superior catalytic performance of HER and OER. The work provides a new idea to construct highly efficient HER and OER dual-functional electrocatalysts.

Propylene/propane separation on a ferroaluminosilicate levyne zeolite

Abstract The propylene/propane separation properties of levyne zeolites with different framework Si/Al and Fe/Al ratios have been examined and compared with those of the four well-studied zeolite adsorbents (i.e., Na-A, Ca-A, Na-X and ITQ-12) for this separation. Both zeolite framework structure and composition were found to be critical for the propylene uptake, kinetic separation and adsorbent durability. Among the zeolites studied here, the mixed CaNH4 form of a ferroaluminosilcate levyne (Si/Al = 15.5 and Fe/Al = 0.27) showed the highest propylene/propane selectivity (11). Under vacuum-swing adsorption mode at 298 K and reservoir pressure of 1.2 bar, this partially iron-substituted zeolite was characterized by a higher propylene uptake (ca. 1.0 vs 0.7 mmol g−1) than its aluminosilicate version, which can be attributed to a combination of the molecular sieve effect of its framework topology and relatively weaker acidity. The results of this study demonstrate that, in contrast to widely held belief, zeolite adsorbents selective for propylene/propane separation do not need to be a pure-silica composition.

Hollow structures by controlled desilication of beta zeolite nanocrystals

The present work examines the different parameters that affect desilication of nanometric Beta zeolite crystals in alkaline solutions. The influences of different synthesis parameters such as the nature of the zeolite (size of the crystals, composition), the alkalinity, the temperature and the amount of added Al species on the morphology and properties of hollow structures are discussed. Addition of sodium aluminate to the alkaline solution protects the surface from desilication and favors dissolution at the center of the crystals, leading to the formation of hollow structures. The size, morphology and crystallinity of those structures depend mainly on zeolite composition, treatment temperature and alkalinity of the solution. If hollow structures are totally amorphous when desilication is carried out under stirring, their crystallinity and thermal stability are significantly improved in the presence of tetraethyammonium (TEA+) cations.

Citric Acid-Treated Zeolite Y (CY)/Zeolite Beta Composites as Supports for Vacuum Gas Oil Hydrocracking Catalysts: High Yield Production of Highly-Aromatic Heavy Naphtha and Low-BMCI Value Tail Oil.

Citric acid-treated zeolite Y (CY) and zeolite beta were mechanically mixed to obtain composite zeolites (CY-Beta) with various zeolite beta contents. The composite zeolites were used as the acid components of hydrocracking catalyst supports. The physical and chemical properties of the supports and catalysts were analyzed by N2 adsorption-desorption, XRD, SEM, and NH3-TPD. The mechanical mixing of CY and zeolite beta does not destroy the textual properties of the original zeolites. However, the acidity of the composite zeolite does not fit the linearly calculated value of the two zeolites because some of the acid sites are covered or reacted with other acid sites during the mixing process. In addition, weak acid sites favor the high yield of tail oil with low BMCI value. Compared with the CY-based and beta-based catalysts, the conversion and light oil yield of the CY-Beta-based catalyst was increased. The conversion, light oil yield, and petrochemical yield of the Ni-W/20CY-Beta(20)/ASA catalyst are 78.15, 65.0, and 83.7%, respectively. The BMCI value of the tail oil is 4.7, and the aromatic potential content (APC) of heavy naphtha (boiling point 65–177°C) is 42%. The 1,500 h pilot plant test of Ni-W/20CY-Beta(20)/ASA at 350°C, 7.0 MPa, 2.0 h−1 LHSV, and 800 H2/oil (v/v) shows that the activity remains stable during the 1,500 h evaluation. The heavy naphtha (APC about 41.0) yield of 41.2 illustrates that the catalyst has the ability to aromatize and cyclize the light fractions. The yield of diesel is about 25% with a cetane index (CI) of 59.2; the frozen point is lower than −45°C, and the cold filter plugging point is −35°C, demonstrating the isomerization performance for middle distillations. The yield of tail oil is 14.9% with a BMCI of 4.4, showing the high hydrogenation performance of the catalyst to transform the un-cracked tail oil to saturated hydrocarbon in order to reduce the BMCI value.

Synthesis and characterization of nanoparticles and composites as bactericides

In the present study, SiO2-TiO2 hybrid nanomaterial and zeolite-TiO2 (Z-TiO2) composites were synthesized by the sol-gel method. Then, the antibacterial activity of the above-mentioned synthesized materials, SiO2 and zeolite (Z) was investigated by the disk diffusion method using Echerichia coli and Enterobacter aerogenes as test microorganisms. All the materials showed antibacterial activity against E. coli with 7.2, 10.7, 3.5 and 8.2 mm of inhibition zone for SiO2-TiO2 hybrid nanomaterial, SiO2, zeolite and Z-TiO2 composite, respectively. However, none of them showed antibacterial activity against E. aerogenes. The obtained results pointed out that these natural-based materials (i.e. Z, SiO2, Z-TiO2 and SiO2-TiO2), known to be noncarcinogenic and nontoxic, can be used as disinfectants against E. coli (an important indicator of the bacteriological quality of water) as safe and eco-friendly alternatives to chlorine.

Hierarchical ZSM-5 based MCM-41 aluminosilicates: Ostwald ripening effect of 8 years old aged samples

MCM-41 with zeolitic nanocomposite has been reported to reduce diffusional restrictions, strengthen structural stability of mesophase and improve acidity. Here we study the natural growth process known as Ostwald ripening effect over composite zeolite particles with aging time. Three different MCM-41/ZSM-5 composites were studied along with conventional AlMCM-41 (AlM41) that are stored for 5 and 8 years. Textural features of MCM-41 with proto-zeolitic nanoclusters at pore walls (ZMST2), ZSM-5/MCM-41 composite with equiproportion mixture of meso and microphases (50 wt%) (ZM27), disordered hexagonal/ZSM-5 composite (ZM23), and AlMCM-41 were compared using x-ray diffraction (XRD), nitrogen adsorption isotherm, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), 27Al MAS NMR, scanning electron microscope (SEM) and transmission electron microscope (TEM). Calcined AlMCM-41 showed aging stability, while calcined ZMST2 showed high Ostwald ripening effect. The disordered hexagonal surface area and pore volume of ZMST2 increase to ∼54% and ∼68% compared to fresh ZMST2. Remarkably, aging in as-synthesised form (A-ZMST2) slowed down the Ostwald process and improved hexagonal thermal stability at 550 °C and 800 °C. ZM27 exhibited high aging stability even in calcined form. The surface area showed about 92% of retainment with an increase in the pore volume (∼20%). ZM23 with disordered hexagonal structure showed that aging period of 5 years decreases meso and increases micropore characters of ZSM-5. Overall, the study shows Ostwald ripening effect dominates over calcined ZMST2, while A-ZMST2 and A-ZM27 in as-synthesised form are able to withstand the structural collapse during long shelf time. Prolonged aging rearranges aluminium coordination environment similar to micropore environment of ZSM-5. The study will further help to understand the atmospheric moisture interactive process with hierarchical zeolites and facilitate preventive measures for long-term industrial applications.

Geopolymerization of Raw Fly Ash to Sodium Zeolites for Sequestration of As (III) in Aqueous Medium

Objective: Massive quantity of Raw Fly Ash (RFA) is generated during incineration due to rapid surge in global energy needs posing severe threat to natural balance owing to constraints associated with its storage and disposal. There exists a pressing and ongoing need to recycle RFA into novel mesoporous geopolymer that can sanitize aqueous medium from hazardous As (III) posturing bioaccumulation. Methodology: NaOH activated Fusion based Hydrothermal Technique (FUHT) was applied for synthesis of sodium zeolites from cost effective Si and Al source i.e. RFA. The characteristics like morphology and surface porosity, surface chemistry and crystallinity in conjunction with ion exchangeability of the Geopolymerized Sodium Zeolite (GSZ) were evaluated by SEM, FTIR, XRD and CEC techniques, respectively. We investigated that scavenging performance of the adsorbent for sequestration of As (III) via ICP-AES and optimized at pH ≈ 8 for 30 minutes by using 150 mg of adsorbent dose. Findings: Adsorption results confirmed that the developed sodium zeolite composites favor multilayer heterogeneous adsorption isotherm. Application: The effort towards industrial waste recycling into value added materials is an emergent move toward achieving a sustainable environment. Keywords: Adsorbent Materials, As (III) Removal, Fly Ash, Water Treatment, Zeolite Synthesis

Enhancing the removal performance of Cd(Ⅱ) from aqueous solutions by NaA zeolite through doped thiourea reduced GO which is trapped within zeolite crystals

In this study, thiourea reduced graphene oxide/NaA zeolite composite (tGO-Zeo) was successfully prepared by a facile two-step synthetic route and used as an efficient adsorbent for removal of Cd(II) from aqueous solution. Characterization of the composite material showed that tGO was entrapped within zeolite crystalline particles and intimately interacted with the zeolite framework. Furthermore, the presence of tGO considerably reduced zeolite crystal size and altered crystal morphology, turning cubic zeolite crystals of micrometer size into nanometer irregular particles. Batch adsorption experiment for Cd(II) removal was conducted and the adsorption performance of tGO-Zeo and Zeo (zeolite) were determined. It was shown that doped tGO significantly enhanced the adsorption capacity of zeolite by 31.54%. The adsorption mechanism differs for tGO-Zeo and Zeo, and tGO-Zeo has higher affinity for Cd(II). The adsorption capacity of tGO-Zeo with a tGO doping amount of 1.26% (wt%) was estimated to be 196 mg/g (1.74 mM/g) at 30 °C and superior to most previously reported zeolite based composites, which often contain large amounts of dopants. The effects of pH and ionic strength on adsorption suggest that ion exchange and coordination are responsible for Cd(II) adsorption by tGO-Zeo. Humic acid can slightly increase Cd(II) adsorption performance of tGO-Zeo, which may be due to tGO-Zeo—humic acid—Cd(II) complexes formation. Therefore, tGO-Zeo composite is a cost-effective and eco-friendly adsorbent for efficient removal of Cd(II) ions from aqueous solutions.

Polyethylenimine-Modified Zeolite 13X for CO2 Capture: Adsorption and Kinetic Studies.

A class of high molecular weight polyethylenimine (PEI)-modified zeolite 13X adsorbents were synthesized by varying the concentration of imines and screened for preliminary investigation of CO2 capture studies. The impregnated molecular amine zeolite composite was characterized and CO2 adsorption performance was investigated through TGA in the presence of atmospheric pure CO2 gas at 25, 50, 75, and 100 °C, respectively, using 20–80 wt % of PEI-loaded zeolite 13X adsorbents. This paper reports on the effects of temperature and amine (PEI) loading on CO2 adsorption capacity and estimated kinetic parameters through modeling of selected models which represent the reaction rate and diffusion rate models. The studied adsorbents showed the highest adsorption capacity at 75 °C with 60 wt % PEI loading. Thus, the optimum temperature of 75 °C and optimal loading of 60 wt % was observed from the current studies for CO2 capture. From modeling study, it was found that Avrami’s fractional order and dual kinetic models (DKM) described well the adsorption behavior of CO2 on PEI-impregnated zeolite 13X at all temperatures accurately and up to 75 °C, respectively. Besides, intraparticle diffusion was found to be the rate-limiting step when compared with the film diffusion model.

Hexavalent chromium removal from aqueous solution by adsorption on modified zeolites coated with Mg-layered double hydroxides.

In this study, MgAl-LDHs and MgFe-LDHs were synthesized via co-precipitation method and in situ coated on pre-washed zeolites through dipping process in beaker. The obtained modified zeolites and original zeolites were utilized as substrates of constructed rapid infiltration systems (CRIS) to remove hexavalent chromium (Cr(VI)) in wastewater. Micro-morphology features and chemical composition of zeolites before and after modification were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray fluorescence spectrometer (XRF). The SEM, XRD, and XRF results demonstrated the feasibility of LDHs coated on the surface of the original zeolites. Purification experiments in simulated CRIS showed that the Cr(VI) removal rates of zeolites/MgAl-LDHs increased by 110.03% on average every concentration (0.5-16 mg L-1) compared with the original zeolites under 24-h HRT. The adsorption capacity of zeolites/MgAl-LDHs reached 66.98 mg kg-1 at 32 mg L-1 initial Cr(VI) concentration, which is nearly twice that of the original zeolites (33.24 mg kg-1) and 1.5 times higher than that of zeolites/MgFe-LDHs (42.01 mg kg-1). Isothermal adsorption tests showed that the Freundlich isotherm equations gave better fitting to the adsorption process. And zeolites/MgAl-LDHs showed a best fit with pseudo-second-order model which meant that the adsorption of Cr(VI) by zeolites/MgAl-LDHs was dominated by chemisorption. Thermodynamic parameters showed that the process of adsorption for the three substrates was spontaneous and endothermic intrinsically. Zeolites/MgAl-LDHs also displayed nearly 60% desorption rate with low concentration eluent (0.01 mol L-1 NaCl). Therefore, zeolites/MgAl-LDHs were chosen out as an optimal substrate for removing Cr(VI) from wastewater in CRIS. Graphical Abstract.

Novel synthesis and characterization of Fe-ZSM-5 nanocrystals in hot compressed water for selective catalytic reduction of NO with NH3

Abstract This paper describes a new synthetic method to prepare a composite of metal oxide nanoparticles and zeolite (Fe-ZSM-5) in hot compressed water. Two approaches, one-pot immobilization of iron oxide on ZSM-5 and post-ZSM-5-synthesis iron oxide impregnation are studied. The products show various morphologies, which lead to different activities during the selective catalytic reduction of NO with NH3. In the first approach, Fe-ZSM-5 is synthesized in hot compressed water from precursors with various concentrations of Fe(NO3)3, while in the second route, firstly, ZSM-5 powder is prepared and then impregnated with iron oxide. The state of Fe in Fe-ZSM-5 was studied through TEM, XPS, XRD, NH3-TPD, and H2-TPR. Both methods result in the production of highly dispersed iron species, however, Fe-ZSM-5 prepared from the one-pot synthesis method contains more acidic sites and more reducible iron species because of the presence of FeOx nanoparticles mainly in the intra-framework of the zeolite. Furthermore, it is observed that the increase in iron concentration in the precursor has an adverse effect on the surface area and acidity of the final Fe-ZSM-5 product. On the other hand, Fe-ZSM-5 obtained from the impregnation process contains higher quantities of iron in the extra-framework position in the form of bulky aggregates with lower activity. Consequently, Fe-ZSM-5 synthesized through the one-pot route showed higher activity because of the well dispersive iron oxide in the zeolite support. The highly dispersive state is attributed to the predominant presence of iron bound to the framework of aluminum in the zeolite. The results also show that the protonation of the catalyst has no crucial effect on the activity of the catalyst, while the oxidation state of iron oxide is greatly responsible for the SCR activity of the catalyst.

Optimization of the use of fly ash and natural zeolite activated as composite for an adsorbent of lead heavy metal (Pb)

Coal is an alternative source of energy besides petroleum and natural gas which are widely used so they can produce a large amount of waste such as fly ash. Natural zeolite is a natural material that is widely spread in the territory of Indonesia. Fly ash and natural zeolite contain a SiO2 and Al2O3 that can be used as an adsorbent. This study aims to create a composite of fly ash/natural zeolite activated as adsorbent to optimize the performance of Pb heavy metal adsorption. Fly ash and natural zeolite were activated using NaOH 3M, and HCl 1M. The adsorption process was carried out with variations of composition 100:00, 75:25, 50:50, 25:75, 00:100 (w/w), variations in pH of 1, 2, 3, 4, 5, 6, and contact time variations 15, 30, 45, 60, 75, 90 min. The adsorbent characterization was performed with FTIR, XRD, SAA, and total specific acidity as well as the final measurement of Pb metal concentration determined by AAS spectrophotometer. The activation process can be shown on the FTIR spectra with the shift of wave numbers, XRD diffractogram showed the decrease of intensity in fly ash and natural zeolite, the increase of acidity value and surface area on each material shows the availability of more active groups. The adsorption of metal Pb reached the optimum condition on fly ash:natural zeolite composition 75:25 (w/w), pH condition of 5, and contact time 60 min, and adsorption capacity of 0, 577 mg/g and 97% adsorption percentage following Langmuir isotherm. The adsorption result obtained is supported by characterization of adsorbent after and before adsorption using SEM EDX indicating the presence of Pb element on adsorbent after adsorption and the surface morphology became rougher due to effect of Pb metal absorption.

Experimental study of heat and mass recovery on steam generation in an adsorption heat pump with composite zeolite-CaCl2

High-temperature steam generation in adsorption heat pump with composite zeolite-CaCl2 has been experimentally investigated by introducing heat and mass recovery. A direct contact heat exchange method is utilized to enhance the overall heat transfer rate. Composite zeolite (CZ) is prepared by immersing zeolite particle in CaCl2 solution at mass concentration of 40%. Cyclic experiment consists of two processes: regeneration with 130 °C dry air and steam generation with 80 °C hot water. The heat and mass recovery with steam below 90 °C is added before generation process. Mass of generated steam above 200 °C is increased by 9.12%. The effective time for steam generation is dramatically extended by 18.33%. Adsorption and thermal equilibriums inside the packed bed are achieved more quickly with heat and mass recovery. Gross temperature lift for one-stage adsorption heat pump is above 100 °C. Coefficient of performance for heating (COPh) and specific heat power (SHP) are elevated by 9.55% and 9.23%, respectively. The increase in mass of generated steam contributes to the improvement of COPh. Meanwhile, only a short time used for heat and mass recovery enables the rise in SHP.