Zeolite Products Research Articles

Solvent-Free Synthesis of Zeolites from Solid Raw Materials

As important industrial materials, microporous zeolites are necessarily synthesized in the presence of solvents such as in hydrothermal, solvothermal, and ionothermal routes. We demonstrate here a simple and generalized solvent-free route for synthesizing various types of zeolites by mixing, grinding, and heating solid raw materials. Compared with conventional hydrothermal route, the avoidance of solvents in the synthesis not only significantly reduces the waste production, but also greatly increases the yield of zeolite products. In addition, the use of starting solid raw materials remarkably enhances the synthesis efficiency and reduces the use of raw materials, energy, and costs.

Characteristics of Brazilian coal fly ashes and their synthesized zeolites

Five different Brazilian fly ashes were used to synthesize zeolites by hydrothermal treatment. Raw fly ash materials and zeolitic products were characterized in terms of pH, conductivity, real density (Helium Pycnometry), specific surface area (BET method), morphological analysis (SEM), chemical composition (XRF), mineralogical composition (XRD) and cation exchange capacity (CEC). Humidity and loss of ignition (LOI) of the fly ashes were also evaluated. Results indicated that the fly ash sample from Figueira power plant (FG) has a high content of Pb. The fly ash from São Jerônimo power plant (SJ) presents a higher content of unburned carbon. Chemical composition analyses indicate that the content of SiO2 and Al2O3 is above 70wt.% in all fly ashes. After hydrothermal treatment, various zeolites such as hydroxy-sodalite, NaP1 and X zeolites were formed depending on sourced fly ash. Hydroxy-sodalite zeolite was formed in all samples. NaP1 zeolite was formed in fly ashes with high content of Ca while X zeolite was formed from the fly ashes with high content of Al. CEC values of the zeolitic materials are 40 times higher than fly ash samples, potential for use as ion exchangers.

Organotemplate-free and seed-directed synthesis of levyne zeolite

Small-pore zeolite levyne has been successfully synthesized following an organotemplate-free route using RUB-50 zeolite as seeds with the aid of a small amount of alcohols. Physicochemical characterization with a combination of techniques including XRD, N2 adsorption, FE-SEM, 27Al and 29Si NMR, and TPD-NH3 shows that the zeolitic product from this seed-directed organotemplate-free synthesis approach (designated as LEV-SDS) has good crystallinity, high surface area, uniform crystals, tetrahedral Al3+ species, and abundant acidic sites. It is also found that alcohols play an important role in preparation of LEV-SDS zeolite by inhibiting the formation of MOR zeolite. Catalytic tests for the conversion of methanol-to-olefins (MTO) show that H-form of LEV-SDS zeolite exhibits good conversion of methanol and high selectivities for ethylene and propylene, which could be potentially important for using LEV-SDS zeolite as a catalyst in MTO reaction.

Investigation of Extra-Large Pore Zeolite Synthesis by a High-Throughput Approach

Seven isoindoline-based organic structure directing agents (OSDAs) with increasing sizes have been prepared and each applied in a high throughput (HT) design of 33 × 5 experiments by varying the synthesis parameters such as Si/Ge, Al(B)/(Si+Ge), F–/(Si+Ge), and H2O/(Si+Ge). Among the 945 experiments, 395 lead to crystalline zeolite products, corresponding to eight zeolites, i.e., Beta (3D 12 × 12 × 12 ring), ITQ-7 (3D 12 × 12 × 12 ring), ITQ-17 (3D 12 × 12 × 12 ring), ITQ-15 (2D 14 × 12 ring), ITQ-21 (3D 12 × 12 × 12 ring), ITQ-37(3D 30 ring), ITQ-43 (3D 28 × 12 × 12 ring), and ITQ-44 (3D 18 × 12 × 12 ring). Most of the crystalline phases obtained (85.8%, 339 of 395) are Beta, ITQ-7, ITQ-17, and intergrowths of ITQ-7 and ITQ-17, which have been named as “Default Structures” here. It has been found that concentrated gels and high Ge/Si ratio favor the formation of low framework density structures. When the OSDAs are relatively small, only “Default Structures” can be obtained, while if the size of OSDA incr...

Trivalent Chromium Ion Removal from Aqueous Solutions Using Low-Cost Zeolitic Materials Obtained from Exhausted FCC Catalysts

The hydrothermal treatment of exhausted FCC catalysts with zeolite was optimized by varying the chemical composition of the synthesis mixture. The zeolitic products obtained were used to evaluate their ability for the capture of Cr(III) cations from aqueous solutions. It was shown that the zeolitic product materials were capable of reducing the Cr(III) ion concentration to values lower than 1.2 ppm. The chromium ion-containing solids were afterwards solidified in cement mortars on which leaching studies of this cation were made. The results obtained showed that the synthesized solids acted as effective Cr(III) ion immobilizers and that their inclusion as additives in cement formulations could provide an environmental friendly disposal procedure.

Synthesis, characterization and catalytic performance of SAPO‐34 molecular sieves for methanol‐to‐olefin (MTO) reaction

AbstractThe methanol‐to‐olefin (MTO) process is important because it offers an alternative to the conventional oil route for the conversion of natural gas or coal to light olefins. The most promising catalysts for the MTO reaction are solid acids with a zeolite structure, where reactants and products such as ethylene and propylene may freely diffuse through active catalysts, but products with larger kinetic diameters are trapped within the cages. In this work, SAPO‐34 molecular sieves were synthesized by hydrothermal crystallization, using triethylamine (TEA) as the template. These samples were characterized by X‐ray diffraction, scanning electron microscopy, thermo‐gravimetric analysis–differential scanning calorimetry, energy dispersive spectroscopy, Fourier transform‐infrared (FT‐IR) and N2 adsorption–desorption. The effects of template concentration and crystallization time on the physicochemical properties and catalytic performance were investigated. The crystallinity and morphology of SAPO‐34 were influenced by the concentration of the template. Pure SAPO‐34 was obtained when the TEA/Al2O3 molar ratio was higher than 2.0. With increased crystallization time, the Si content in SAPO‐34 crystals increased, which influenced the surface acidity. FT‐IR spectra indicated that all samples were dominated by Lewis acid sites and the sample crystallized for 11 h exhibited the lowest number of Lewis acid sites. The catalytic performance of SAPO‐34 was tested with the MTO reaction. High selectivity to olefins (C2H4 + C3H6) was obtained over the catalyst synthesized with a TEA/Al2O3 ratio of 3.0 and crystallization time of 11 h. At the reaction temperature of 450 °C, the methanol conversion approached 100% and the yield of C2C4 olefins was more than 80%. Hence, SAPO‐34 molecular sieves were shown to be excellent catalysts for the MTO reaction. Copyright © 2010 Curtin University of Technology and John Wiley & Sons, Ltd.

Modified natural clinoptilolite with quercetin and quercetin dihydrate and the study of their anticancer activity

Natural zeolite of the clinoptilolite type (CT, particle size up to 200 μm) and its modified forms with different content (0.06–5%) of pharmaceutically active compounds (type of flavonoids): quercetin (Q) and quercetin dihydrate (QD) have been investigated by thermal analyses TG, DTA and DTG, FTIR spectroscopy, fluorescence spectroscopy, X-ray powder diffractometry, determination of the surface areas and the pore volumes by low-temperature adsorption of nitrogen and atomic force microscopy. The analyses checked the presence of Q or QD in modified zeolitic products (CTQ and CTQD). Natural zeolite of the clinoptilolite type and their modified forms CTQ and CTQD with low content (0.06% and 1%) of Q and QD have been used for the study of their anticancer activity. Carcinoma cell lines Jurkat, CEM, HeLa, MCF7, A549 and MDA were treated with various amounts of natural clinoptilolite and their modified forms CTQ and CTQD. The water content of the channel system influences the cytotoxicity of zeolite. The results of the study of pure CT thermally activated at two different temperatures 110 and 400 °C confirmed the better cytotoxicity of CT activated at 110 °C (CT110) with higher content of water in comparison with CT activated at 400 °C (CT400). Clinoptilolite modified with quercetin dihydrate (CTQD) has shown better cytotoxicity compared with clinoptilolite modified with quercetin (CTQ).

Hydrothermal synthesis of high-silica mordenite by dual-templating method

High-silica mordenite (MOR) zeolites were hydrothermally synthesized by a dual-templating method using tetraethylammonium hydroxide (TEAOH) and hexamethyleneimine (HMI) as co-structure-directing agents (SDAs). The MOR zeolites were crystallized readily with the addition of NH 4NO 3 from the gels that had a Si/Al ratio up to 60. The synthesis resulted in highly crystalline MOR zeolites possessing a Si/Al ratio of 37.1. The chemical coordination states of the Al ions in the MOR zeolites were characterized by 27Al and 29Si NMR MAS spectroscopy. The Al ions occupied dominantly the tetrahedral sites in the framework. The dual-templating effect that the two amines exhibited on the zeolite crystallization was investigated by 13C MAS NMR spectroscopy and elemental analyses. Both organic SDA molecules were incorporated simultaneously into the zeolite products, corresponding to 65% of TEA + and 35% of HMI. These two kinds of SDAs played a cooperative role in the nucleation and crystallization of the MOR structure under high silica conditions.

Synthesis of zeolites from the low-grade Tunisian natural illite by two different methods

Na-zeolites were successfully synthesised for the first time from Tunisian natural illite clay by two different methods: (1) alkaline fusion prior to hydrothermal reaction and (2) conventional hydrothermal alkaline activation. Both processes have been evaluated at different conditions of temperature and reaction time in order to optimise the synthesis. Products have been identified by X-ray diffraction and characterised by Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy (SEM). The textural properties were investigated by BET measurements, and also the cation exchange capacity (CEC) was determined. By fusion with NaOH followed by hydrothermal reaction, illite was converted into zeolite X. Using the second method, sodalite mixed with quartz and unreacted clay was formed during the treatment of illite in NaOH solution. In both cases, the synthetic zeolite products displayed significantly increased cationic exchange capacities compared to the raw material. However, the fusion method yielded better results in terms of shorter reaction times necessary to obtain a product with high crystallinity and excellent performance as a cation exchanger and surface area. The maximum surface area and CEC of the products were found to be 293 m 2/g and 342 meq/100 g, respectively.

Use of industrial kaolin waste from the Brazilian Amazon region for synthesis of zeolite A

AbstractProduction of kaolin for the paper-coating industry in the Brazilian Amazon region generates large amounts of waste, most of which is kaolinite. It is known that such materials can be used to synthesize zeolites. The use of kaolin waste for zeolite synthesis could, in principle, help social and economic development while providing valuable materials for industry. Additionally, there is a significant environmental appeal if such wastes could be used instead of new raw materials.This study focused on the production of zeolite A. Samples of the raw material were first calcined (700ºC/2 h) to obtain metakaolinite for further reaction with NaOH solution. Different parameters were evaluated to optimize the synthesis conditions of zeolite A. The results showed that zeolite A with a large degree of structural order was generally obtained as the only zeolitic product. The following synthesis conditions were used: temperature 110ºC, time 24 h and a Na/Al ratio of 1.36. Hydroxysodalite was also obtained under specific conditions.

Thermochemical study of sorption of pyridine derivates by copper forms of synthetic and natural zeolites

Sorption of hazardous pyridine derivates by copper forms of synthetic zeolite ZSM5 and natural zeolite of the clinoptilolite type (CT) has been investigated. Sorption of 2-chloropyridine (clpy) and 2-ethylpyridine (ethylpy) from liquid and gas phase by copper forms of zeolites (Cu-ZSM5 and Cu-CT) has been studied by CHN analysis, thermal (TG, DTG and DTA) analysis, FTIR spectroscopy, X-ray powder diffractometry and determination of the surface areas and the pore volumes by low-temperature adsorption of nitrogen. The results of thermal analyses of Cu-ZSM5, Cu-(clpy) x -ZSM5, Cu-(ethylpy) x -ZSM5, Cu-CT, Cu-(clpy) x -CT and Cu-(ethylpy) x -CT zeolitic products with different composition (x depends on the experimental conditions of sorption of pyridine derivates) clearly confirmed their different thermal properties and the sorption of pyridine derivates. The main part of the decomposition process of zeolitic samples containing pyridine derivates occurs at considerably higher temperatures than the boiling point of pyridine derivates proving strong bond and irreversibility of clpy- and/or ethylpy–zeolite interaction. FTIR spectra showed well-resolved bands for pyridine derivates in the Cu-(clpy) x -zeolite and Cu-(ethylpy) x -zeolite. Surface area and pore volumes of the samples Cu-clpy-ZSM5, Cu-ethylpy-ZSM5, Cu-clpy-CT and Cu-ethylpy-CT in comparison with Cu-ZSM5 and Cu-CT decreased due to the adsorption of pyridine derivates.

Synthesis of Aluminosilicate and Gallosilicate Zeolites via a Charge Density Mismatch Approach and Their Characterization

Aluminosilicate and gallosilicate zeolite syntheses via a charge density mismatch (CDM) approach are compared at intermediate-silica compositions (Si/Me = 5-16, where Me is Al or Ga). With a variation of the crystallization temperature and of the type and/or concentration of alkali metal ions added as a crystallization structure-directing agent (SDA) to tetraethylammonium-tetramethylammonium, tetraethylammonium-hexamethonium, and strontium-choline mixed-SDA systems, we were able to obtain 11 different zeolite structures. However, only 5 out of a total 40 pairs of aluminosilicate and gallosilicate synthesis runs at otherwise identical chemical compositions were found to give the same zeolite product with no detectable impurities, suggesting that the structure-directing ability of Ga is quite different from that of Al even in intermediate-silica synthesis conditions. The CDM approach to offretite synthesis led to hexagonal plate-like crystals with aspect ratios lower than 0.3, and UZM-22 exhibited no significant preference of Al substitution for particular tetrahedral sites, especially for site T1, unlike its framework type material ZSM-18. More interestingly, the EU-1 zeolite obtained from an aluminosilicate synthesis mixture containing Li(+) as an inorganic crystallization SDA in the tetraethylammonium-hexamethonium double-organic additive system has been characterized to locate about half of its Li(+) ions in the framework, while the Li distribution over the 10 topologically different tetrahedral sites is nonrandom in nature.

Effects of Supplementation of Natural Zeolite on Intake, Digestion, Ruminal Fermentation, and Lactational Performance of Dairy Cows

ABSTRACT A lactating dairy cow experiment was conducted to determine the influence of a ruminal buffer product containing magnesium-exchanged zeolite on ruminal fermentation and lactational performance. The experimental TMR diet consisted of 38% alfalfa hay, 19% corn silage, 14% corn grain, and 30% concentrate mix on a DM basis, and it was fed ad libitum. Thirty primiparous and multiparous lactating Holstein cows (52 ± 23.0 DIM) were assigned to 1 of 3 dietary treatments with 10 cows in each treatment: control (TMR diet without ruminal buffer), TMR diet with 1.4% sodium bicarbonate (SBD), and TMR diet with 1.4% zeolite product (ZD). The experiment was a completely randomized design performed over 12 wk. Intake of DM was similar (26.5 kg/d) across treatments. Milk yield was similar among the 3 treatments (40.7 kg/d on average), and efficiency (4% FCM/DMI) was not affected by treatments. Milk fat concentration did not differ among treatments, whereas milk protein concentration tended to be higher for the ZD than for the control and the SBD (P = 0.15). Although feeding the ZD resulted in a tendency of increased milk protein concentration, feed nitrogen (N) efficiency for milk N did not differ among the 3 treatments. In addition, milk urea N concentration was not influenced by feeding the ZD. Ruminal pH tended to increase (P = 0.11) when feeding the SBD or the ZD compared with the control. Concentration of ammonia N did not differ among treatments. Feeding the ZD tended to decrease (P = 0.14) total VFA production compared with feeding the control and the SBD, whereas molar proportions of acetate and propionate were not affected by the treatments. The zeolite product used in this study would cost-effectively replace sodium bicarbonate as a ruminal buffer additive in a lactating dairy diet, but its efficacy needs to be further assessed when supplemented in a high-concentrate lactating dairy diet whereby animals may experience subacute ruminal acidosis.

Inception and Trapping of ZnO Nanoparticles within Desilicated Mordenite and ZSM‐5 Zeolites

AbstractZnO nanoparticle inception within mordenite and ZSM‐5 zeolites, of varied Si/Al ratios, was achieved via the exchange of zeolite cations with Zn2+, followed by NaOH leaching, and thermal treatment at 550 °C under O2. ZnO particles were observed by electron microscopy; further characterization included X‐ray diffraction, thermogravimetric analysis, and N2 sorption. NaOH addition caused a partial desilication of mordenite and ZSM‐5 zeolites as shown by a decreased Si/Al ratio. The bulk and surface Zn and Al concentrations were measured by ICP‐AE spectrometry and XPS, respectively. N2 sorption isotherms on ZnO/zeolite specimens indicated the existence of micropores and mesopores; the amounts of them in mordenite and ZSM‐5 zeolites were determined from adsorption data at low pressures. The progressive growth of ZnO nanoparticles induced some micropore widening as well as the inception of a slit‐like intrazeolite mesoporosity due to the desilication of the substrate during the NaOH leaching process. The final zeolite products are potentially useful as they are endowed with a twofold micro‐mesoporosity.

Removal of pyridine from liquid and gas phase by copper forms of natural and synthetic zeolites

Zeoadsorbents on the basis of copper forms of synthetic zeolite ZSM5 and natural zeolite of the clinoptilolite type (CT) have been studied taking into account their environmental application in removing harmful pyridine (py) from liquid and gas phase. Sorption of pyridine by copper forms of zeolites (Cu-ZSM5 and Cu-CT) has been studied by CHN, X-ray photoelectron spectroscopy, X-ray powder diffractometry, FTIR spectroscopy, thermal analysis (TG, DTA and DTG) and analysis of the surface areas and the pore volumes by low-temperature adsorption of nitrogen. The results of thermal analyses of Cu-ZSM5, Cu-(py)xZSM5, Cu-CT and Cu-(py)xCT zeolitic products with different composition (x depends on the experimental conditions of sorption of pyridine) clearly confirmed their different thermal properties as well as the sorption of pyridine. In the zeolitic pyridine containing samples the main part of the pyridine release process occurs at considerably higher temperatures than is the boiling point of pyridine, which proves strong bond and irreversibility of py–zeolite interaction. FTIR spectra of Cu-(py)xzeolite samples showed well resolved bands of pyridine. The results of thermal analysis and FTIR spectroscopy are in a good agreement with the results of other used methods.

Structural analysis of zeolite NaA synthesized by a cost-effective hydrothermal method using kaolin and its use as water softener

Zeolite 4A (LTA) has been successfully synthesized by a hydrothermal method, where kaolin was used as silica and alumina source. The synthesized zeolite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser granulometry, and FTIR spectroscopy. XRD data from the Rietveld refinement method confirmed only one crystallographic phase. Zeolite A morphology was observed by SEM analysis, and it showed well-defined crystals with slightly different sizes but with the same cubic shape. Particle size distribution of the crystals was confirmed by laser granulometry, whereas FTIR spectroscopy revealed significant structural differences between the starting material and the final zeolite product used as water softener.

Preparation of type 4A zeolite from Iraqi kaolin: Characterization and properties measurements

Molecular sieves or zeolites are important widespread industrial materials of unique chemical structure, which are used in most industrial plants as an adsorbent for gases or even as catalysts. Zeolite 4A was prepared from Iraqi kaolin using the ion exchange technique to insert a sodium ion in to the kaolin structure. It was characterized by X-ray diffraction and tested for water adsorption capacity to test the reliability of kaolin as a raw material for zeolite production, and this seems to be the case.

Adaptation of bagasse fly ash, a sugar industry solid waste into zeolitic material for the uptake of phenol

AbstractBagasse fly ash (BFA), a sugar industry waste was converted into zeolitic material (ZBFA) by alkaline hydrothermal treatment. The virgin BFA and synthesized ZBFA were characterized by various instrumental techniques viz. XRF, FTIR, PXRD. Zeolitazation achieved showed that zeolite‐P was the dominant constituent of ZBFA. The physico‐chemical properties of BFA and ZBFA were compared. Morphology of the sorbents was examined by SEM. The kinetic and thermodynamic data of sorbents were evaluated by Coats and Redfern method using Thermal Analysis (TGA, DTG, and DTA) data. The point of zero charge value of the sorbents determined by mass titration method showed higher value for ZBFA (pH 8.62) as compared with BFA (pH 5.80). The specific surface area of ZBFA increased to 505 m2/g (BFA = 440 m2/g). Sorption capacities of BFA and ZBFA were examined by sorption of phenol at various operational parameters. The equilibrium data were analyzed by various adsorption isotherms viz. Langmuir, Freundlich, Temkin, and D‐R. Langmuir isotherm best fits the experimental data for ZBFA (qm = 35.43 mg/g) and BFA (qm = 16.33 mg/g). The isotherms study indicates that the sorption capacity of synthetic zeolitic (ZBFA) products is significantly increased after alkaline hydrothermal treatment. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Effects of ultrasonic treatment on zeolite synthesized from coal fly ash

The synthesis of zeolites from three samples of fly ash was carried out through a low-temperature (25–60 °C) hydrothermal process with a NaOH pre-fusion treatment preceded by sonication. The results were compared with those of conventional hydrothermal syntheses. XRD and SEM investigations demonstrate that the application of ultrasonic treatment facilitates the formation of zeolites at a lower-temperature (25 °C) than syntheses not preceded by sonication. No significant difference in type, temperature of crystallization, or amount of zeolites synthesized was noted between the three different samples of fly ash, implying that the chemical composition of fly ash had little influence on the zeolite product within the compositional range of these fly ash precursors. Although there appears to be a correlation between the SiO 2/Al 2O 3 ratio of the fly ash and the temperature of zeolite formation by conventional synthesis, no correlation was apparent when ultrasonic pre-treatment was used at low-temperatures.

Bench-scale synthesis of zeolite A from subbituminous coal ashes with high crystalline silica content

In this present work, fly ash and bottom ash with high crystalline silica content were obtained from the coal-fired boilers within the paper industries in Thailand. These coal ashes were used as the basic raw materials for synthetic zeolite production. The crystal type and crystallinity, specific surface area and pore size, and textural properties of zeolite products were characterized by using X-ray diffraction spectroscopy (XRD), N 2 sorption analysis, and Scanning Electron Microscopy (SEM), respectively. It was found that sodalite octahydrate was selectively formed via the direct conventional (one-step) synthesis, whereas through a two-step, sodium silicate preparation and consecutive zeolite A synthesis process, 94 and 72 wt.% zeolite A products could be produced from the fly ash and bottom ash, respectively. The cation-exchange capacity (CEC) of fly ash and bottom ash-derived zeolite A products were closely similar to that of the commercial grade zeolite A.