Zeolite Y from kaolin clay of Kachchh,India: Synthesis,characterization and catalytic application

Kaolin clay obtained from Kachchh, Gujarat was used as alumina and silica source to synthesize zeolite Y by hydrothermal method. The synthesis route comprised of the following steps: sulfuric acid treatment at 110 ​°C (4 ​h) for impurity removal followed by calcination at 600 ​°C for 4 ​h, thermal activation of kaolin into metakaolin by NaOH fusion at 850 ​°C (8 ​h); aging of reaction mixtures at 50 ​°C (24 ​h); crystallization (24 ​h) followed by washing and drying. The synthesized zeolite Y was examined by multiple characterization techniques which revealed a pore volume of 0.22 ​cm³/g with pore size of 2.89 ​nm having essential surface area of 320 ​m²/g, indicating a porous material having majority of micropores and remaining mesopores. The zeolite exhibited good catalytic activity for succinic acid esterification using ethanol to produce monoethyl and diethyl succinate. The conversion of SA (72%) and yield (60%) of valuable diester indicated good conversion rate and selectivity at moderate reaction conditions. Detailed structural comparison with zeolite Y synthesized using standard chemical route is also carried out. This work demonstrated an effective way of preparing environmentally benign porous zeolite Y having high surface area and pore volume that can be useful for catalytic applications.     

Synthesis and characterization of geopolymer-zeolites from Ghanaian Kaolin samples by variation of two synthesis parameters

Two kaolinitic clays from two Regions of Ghana: Western and Volta Regions, were first calcined at 600 °C for 2 h to transform into the amorphous aluminosilicate phases. The effects of kaolin and alkali ratio as well as aging on the amount and types of zeolite in the resultant geopolymers were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transformed spectroscopy, thermogravimetric analysis and specific surface area measurements. Alkali activation treatment of the metakaolin yielded bulk materials with different amounts and types of zeolite and different particle size distributions. The results showed that initial kaolin samples were dependent on the concentration of alkali treatment and crystallization time during the activation treatment and produced zeolite type A along with quartz which showed no reactivity regardless of the variation of the synthesis parameter.

     

Reaction sintering and microstructural evolution in metakaolin-metastable alumina composites

Fine needles of mullite grains were obtained successfully in a compact and low porous matrix using solid state sintering. We treated high-grade kaolin and sand-rich kaolin at 750 °C to amorphous metakaolins, and bauxite at 1,000 °C to metastable alumina. By designing a stochiometric composition of mullite, each amorphous metakaolin was added to metastable alumina. Fine grains of mullite with almost complete crystallization were obtained from 1,350 °C in a case of amorphous metakaolin from high-grade kaolin and at 1,550 °C in the other case where amorphous metakaolin is from sand-rich kaolin. The difference in the temperatures of mullitization was linked to the late dissolution of silica from the cristobalite and quartz phases which were still present in the sand-rich metakaolin sample at 1,350 °C. The use of metastable alumina and metakaolin instead of kaolin to design the mullite matrix allows the increase in number of mullite nucleation sites. This results to high densification and crystallization, fine grain size, and high mechanical properties of the final matrix.     

Evaluation of phase transformation behaviors of zeolite and antibacterial properties against Gram-positive and -negative bacteria

This study deals with the synthesis of zeolite from natural kaolinite using hydrothermal treatment and evaluation of its phase transformation behaviors. The synthesized zeolites were modified with silver ion by using the ion exchange method for the enhancement of antibacterial properties. The characterizations were performed by using X-ray diffraction spectroscopy, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray. Disk diffusion technique (DDT) was used for the evaluation of the antibacterial property of the modified zeolites. This study observed the transformation of kaolinite into amorphous metakaolin after calcination treatment at 900°C and the successful reconstruction of amorphous metakaolin into synthesized crystal zeolite in the presence of sodium hydroxide as an activating agent. It was also found that the zeolite type A was produced at 100°C, while sodalites were produced at 120 and 140°C. DDT analysis revealed that the modified zeolites showed significant antibacterial capability against Escherichia coli ATCC 11229 and Staphylococcus aureus ATCC 6538. In general, the present study has proven that the zeolites can be synthesized from natural material and can be modified with silver ion to enhance their antibacterial activity.     

超声陈化法制备纳米NaY分子筛及形成机理研究

Nano-sized NaY zeolite was synthesized from metakaolin in the hydrothermal synthesis system by using ultrasonic during aging time.The process of crystallizing NaY zeolite was studied by XRD、SEM、ICP OES ,and the formation mechanism of nano-sized NaY zeolite was researched,finally the conditions of synthesizing nano-sized zeolite NaY had been brought forward.     

Effect of zeolite, kaolin and alumina during cracking of heavy petroleum residue evaluated by thermogravimetry

This work evaluates the effect of the FCC catalyst components—Y zeolite, kaolin and alumina—on the formation of coke during the cracking of heavy residue (HR) of petroleum. The Y zeolite, kaolin and alumina were mixed with a HR at a ratio of approximately 1:4. The effect was studied using dynamic thermogravimetry at a heating rate of 50 K min⁻¹, with N₂ (between 35 and 700 °C) and air (in the 700–1,000 °C temperature range). The HR analyzed in these conditions formed 8.1% of coke. All the mixtures presented larger coke formation than that observed in pure HR. The Y zeolite presented fourfold larger coke formation, while kaolin and alumina showed twofold higher formation than pure HR. The major focus of this study was to verify the sensitivity of the TG technique in providing information about coke formation in the fluid catalytic process of refineries.     

Recrystallization of Zeolite Y to Analcime and Zeolite P with <SC>d</SC>‐Methionine as Structure‐Directing Agent (SDA)

In this study, the synthesis of template free zeolite Y and its recrystallization to two types of pure zeolite P and analcime in the presence of the amino acid d‐methionine as structure‐directing agent were investigated. The recrystallization occurred solely when specific heating cycles were applyed. A completely crystallized phase of zeolite Y for the mixture of zeolite P and analcime was observed in the presence of d‐methionine at a concentration of 0.015 <SC>m</SC>. The effect of different Si/Al ratios (2.3–9.3), crystallization temperatures (40–160 °C), and crystallization times (28–96 hours) on the achievement of two different zeolite types were studied as well. Pure zeolite P was obtained during conventional heating to 100 °C for 42 hours, whereas pure analcime zeolite was achieved by heating the mixture to 160 °C for 96 hours. The products were characterized by X‐ray diffraction, scanning electron microscopy, and IR spectroscopy.     

A study of thermal treatment and hydrothermal crystallization stages in production of granulated NaA zeolite from mechanically activated metakaolin

NaA zeolite was synthesized from mechanically activated granulated mixtures of metakaolin, sodium hydroxide, and aluminum oxide. The thermal treatment and hydrothermal crystallization processes were studied. It is shown that the optimal temperature of thermal treatment of grains based on a mechanically activated metakaolin is 600°C at a NaA zeolite content of about 65 wt %. Raising the calcination temperature leads to a decrease in the content of the zeolite and to formation of nepheline. It was found that the optimal concentration of the crystallization solution of NaOH is 2–4 M. Under these conditions, the content of the zeolite exceeds 90 wt %. Raising the alkali concentration leads to a decrease in the content of the zeolite and to its recrystallization into sodalite.     

Synthesis of hexagonal zeolite Y from Kankara kaolin using a split technique

Synthesis of hexagonal zeolite Y from Kankara kaolin using a split technique is presented. The technique entails splitting kaolin to alumina and silica components. These components were further recombined to synthesize zeolite Y. The as-synthesized NaY zeolite was transformed to REY zeolite. Characterizations of the as-synthesized zeolite Y were carried out using X-ray diffraction (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) texture analysis, scanning electron microscope (SEM), transmission electron microscope (TEM) and Fourier transform infrared (FTIR) spectroscopy. Catalytic desulfurization of the as-synthesized REY zeolite was studied using microwave assisted desulfurization of model diesel. The Si/Al molar ratio of the as-synthesized NaY zeolite was 4.27. The crystallinity of the as-synthesized NaY and REY zeolites were 79.1 and 56.5% respectively. The as-synthesized NaY and REY zeolites possessed hexagonal morphology with average crystal sizes of 200 and 100 nm respectively. The specific surface area, pore volume and pore diameter of the as-synthesized NaY zeolite were 732 m² g^?1, 0.2611 cm³ g^?1 and 1.426 nm respectively. The specific surface area, pore volume and pore diameter of the as-synthesized REY zeolite were 456 m² g^?1, 0.1591 cm³ g^?1 and 1.395 nm respectively. Zeolite Y synthesized using the split technique possessed physiochemical properties comparable to the commercial zeolite Y, it was also free of quartz and competing phase impurities reported in previous works. The as-synthesized REY zeolite resulted to 79% sulfur reduction when used as a catalyst in a microwave desulfurization of model diesel at 100?°C for 15 min.     

Effect of ultrasound on the thermal behavior of the mixtures for the LTA zeolite synthesis based on metakaolin

The effect of ultrasonic treatment on the thermal behavior of the mixtures from metakaolin, sodium hydroxide and alumina designed for LTA zeolites synthesis was studied. X-ray diffraction analysis, infrared spectroscopy, scanning electron microscopy and synchronous thermal analysis have been used. It was shown that after evaporation of the suspension, LTA zeolite (24 mass%) is contained in the samples. It was established that the new phase (sodium aluminum silicate) is formed at a calcination temperature of about 600 °C. It was demonstrated that at a calcination temperature over 800 °C, nepheline is synthesized. The reaction of nepheline formation has been described by the topochemical equation of four-dimensional nucleation/nucleus growth according to Avrami/Erofeev. Using the Ozawa–Flynn–Wall analysis for non-isothermal data, the values of the activation energy and the pre-exponential factor have been calculated. It is shown that after the ultrasonic treatment the activation energy of the nepheline synthesis reaction has smaller values than in the sample without pretreatment. These phenomena have been explained by differences between the structural parameters of the particles (dimension of the coherent scattering region, the value of microdeformations).     

Production of metakaolin from industrial cellulose waste

Research focused on the transformation and utilization of industrial wastes into products of commercial interest plays an increasingly important role. Residual pulp can become useful in the manufacture of different materials, providing high value to this waste and reducing its environmental impact when disposed of improperly in the environment. The main constituents of this waste are kaolin and calcium carbonate (CaCO₃). Starting from kaolin, metakaolin can be produced by calcination of the residue at 630?°C for 2?h in a rotary reactor with air flow, followed by solubilization with hydrochloric acid to remove the CaCO₃. The development of technological alternatives aimed at the reuse of certain wastes can result in applications of real economic interest to the chemical industry and ceramics and glass, which is the case in this study. The raw material and metakaolin obtained were analyzed by thermogravimetric analysis and derivative thermogravimetric analysis, X-ray diffraction, and X-ray fluorescence spectroscopy with promising results. This is because metakaolin was obtained free of contamination by other materials.     

由酸活化高岭土制备多级纳米孔HY分子筛及其表征

由酸活化的高岭土制备了多级纳米孔HY分子筛。通过改变老化时间和晶化时间可得到最大的多级因子(HF),此时外比表面积最大而微孔孔体积变化不大。运用X射线衍射(XRD)、X射线荧光光谱、N2吸附-脱附法和NH3程序升温脱附对所得样品进行了表征。老化2 d和晶化24 h所制的纳米孔HY分子筛样品的HF值最大。样品的酸性和结晶度也随着制备条件而变化。另外,适量NaCl的嵌入对提高对所制样品的HF值、酸性和结晶度起到重要作用。通过比较样品和常规HY分子筛的XRD峰强度算得样品的结晶度。结果表明,优化合成条件可得到广泛适用于工业化的分子筛制备路线。     

Preparation and characterization of nanosized ZSM-5 zeolite using kaolin and investigation of kaolin content, crystallization time and temperature changes on the size and crystallinity of products

Nano sized ZSM-5 zeolite samples were synthesized successively from kaolin clay as alumina source having a large amount of quartz (39%) and silicic acid as silica source by hydrothermal treatment with NaOH in the presence of tetrapropylammonium hydroxide as a template. Then the effect of kaolin content, crystallization temperature and time on the size and crystallinity of the products were investigated. The prepared samples were characterized using XRD, SEM, EDS and FT-IR techniques. The results showed that the synthesized ZSM-5 zeolite samples were almost pure and their crystallization was almost complete. The average particle size, as determined by Debye-Scherrer equation, was in the range of 20-42 nm. Increasing kaolin content on crystal size was more effective than increase in crystallization temperature and time. Additional evidences for the nano sized ZSM-5 zeolite were the asymmetric stretch vibration band at 1225 cm^-1 in the FT-IR spectra and TEM images. The scanning electron micrographs of the synthesized zeolites showed that they are spherical shape crystals.     

新型FCC催化剂的制备与性能

研究了高岭土型流化催化裂化催化剂的制备与性能，粒度分布中粒么μｍ左右的细高岭土，经浆化和喷雾成型制在４０－８０目的母体微球，部分微球在高温下焙烧使生高岭土通过高于特征温度焙烧转化为ＣＭＡ，另一部分在较低温度下焙烧使其转化为偏高岭ＣＭＢ。ＣＭＡ和ＣＭＢ混合后与硅酸钠等反应２０－３０ｈ，使混合球上发生晶化，生成２５％以上的ＮａＹ分子筛。     

A tool for predicting the integrity of Y zeolite crystalline structure

The purpose of this work was to employ the differential thermal analysis technique (DTA) to compare variations in the collapse energy of the Y zeolite crystalline structure in a fresh sample and in the sample after temperature treatment and impregnated with 3,000 ppm of vanadium and nickel. A small exothermic signal in the DTA curve at 950–1,150 °C indicated the collapse of the crystalline structure. The areas of the exothermic signals in the DTA curves of the samples indicated a 20% reduction in the exothermic area peak of sample treated 600 °C for 3 h and 25% reduction in same peak in the metal impregnated Y zeolite. These results were compared with X-ray data leading to the conclusion that metal impregnation affects the Y zeolite crystalline structure and that the DTA technique is a potentially useful tool for measuring the integrity of Y zeolite in catalysts.     

Synthesis and characterization of zeolites NaA and NaY from rice husk ash

In this study, both zeolites NaA and NaY were synthesized from rice husk ash (RHA) by a simple conventional hydrothermal route. Rice husk (RH) was used as a silicate source to produce various zeolites. The hydrothermal route was conducted via a seeding technique involving the preparation of two separate gels, i.e. colloidal seed and feedstock gel. The zeolite was first produced using commercially available chemicals and followed by the replacement of the commercial silicate sources with RHA derived silicate. The RHA silicate was obtained by combusting the RH at different temperatures and durations i.e. 450 °C for both 2 and 6 hours, as well as 750 °C for 6 hours. Zeolite NaY (faujasite) was successfully synthesized with commercial chemical seed and RHA derived feedstock gel. On the other hand, using RHA silicate in both colloidal seed and feedstock gel would give only zeolite NaA. Elemental, structural and morphological analyses of RHA and zeolites were carried out with X-ray fluorescence (XRF) spectrometer, X-ray diffractometer (XRD) and scanning electron microscopy (SEM).     

Synthesis of liquid hydrocarbons enriched with triptane via dimethyl ether conversion over combined catalyst

A combined catalytic system composed of catalysts with different functions was prepared. The catalyst for the synthesis of lower olefins based on is H-ZSM-5 zeolite modified with Mg, was mixed with the catalyst for alkylation of isobutane by olefins based on H-Y zeolite modified with La and Pd. In the presence of the combined system, liquid branched hydrocarbons were synthesized from dimethyl ether in a hydrogen medium at 340 °C and a pressure of 10 MPa. The effect of the composition of the combined catalyst on its selectivity to liquid hydrocarbons and, specifically, triptane was shown.

     

Influence of catalyst binder on the acidity and activity/selectivity of Ga/H-ZSM-5 zeolite in propane aromatization

The acidity and initial and time-on-stream activity in propane aromatization (at 550°C, space velocity of 3100 cm³g⁻¹ _(zeolite)h⁻¹) of Ga-impregnated H-ZSM-5 zeolite without or with binders (50 wt%), such as silica, alumina and kaolin, have been investigated. Both the acidity and catalytic activity of the zeolite are influenced by the presence of binder in the catalyst, depending upon the binder. The influence is found to be lowest for alumina and highest for kaolin. Among the binders, alumina is the most preferred binder for the zeolite catalyst.     

Preparation of uniform and nano‐sized NaA zeolite using silatrane and alumatrane precursors

Nano‐sized Na A zeolite was successfully synthesized via the sol–gel process and microwave techniques. The synthesis parameters, such as hydroxide ion concentration, seed amount, as well as heating time and temperature, were studied to obtain the most uniform and very small sized NaA zeolite using the composition of SiO₂:Al₂O₃:xNa₂O:410H₂O; 3 ≤ x ≤ 6. It was found that hydroxide ion concentration affects the crystal size and heating time, whereas a higher amount of seed provides smaller sized NaA zeolite. The zeolite product can be synthesized using a higher temperature for a shorter time or lower temperature for a longer time. The best conditions for synthesizing the smallest size, 0.1–0.2 µm, and the most homogeneous NaA zeolite is to use the composition of SiO₂:Al₂O₃:3Na₂O:410H₂O and 3 wt% crystal seed at 80 °C microwave heating for 6 h. The synthesized NaA zeolite was characterized using XRD and SEM. Copyright © 2006 John Wiley & Sons, Ltd.     

Targeted Synthesis of Ultrastable High‐Silica RHO Zeolite Through Alkali Metal–Crown Ether Interaction

High‐silica RHO zeolite was directly synthesized using an alkali metal‐crown ether (AMCE) complex as organic structure‐directing agent (OSDA). Derived from the UV‐vis spectra and zeolite patterns, the crown ether‐cesium cation interaction was found to have crucial effect on the enhancement of silica content within the zeolite framework. The synthesized RHO zeolites possess up to four times larger silica/alumina ratio (SAR) values than that in their conventional form, which gives them extraordinarily rigid frameworks even after hydrothermal aging under 800 °C. Compared to commercial zeolites, copper‐exchanged high‐silica RHO zeolites demonstrate considerably high reaction activity in NO_X removal, making them promising candidates for diesel exhaust treatment.