As-prepared Zeolite Research Articles

Adsorption of rare earth elements (Ce3+, La3+, and Nd3+) and recovery from phosphogypsum leachate using a novel ZSM-5 zeolite

ZSM-5 zeolite is a multifunctional material highly efficient for adsorbing ions. Our ZSM-5 was synthesized by employing a nucleating gel as a structure-directing agent, followed by homogenization and hydrothermal treatment. The as-prepared ZSM-5 was physicochemically characterized to assess its properties. Next, the as-prepared zeolite was employed as an adsorbent to remove rare earth elements, REEs from synthetic solutions and real phosphogypsum leachate under batch mode operation. As expected, the ZSM-5 adsorbent was discovered to be highly microporous with abundant surface functionalities, which could positively impact REE adsorption. The adsorption data indicated a high affinity between ZSM-5 and all three REEs with rapid kinetics and high adsorption capacities. The modeling study suggested that the adsorption kinetic data were well fitted by Avrami-fractional order, and Liu described the equilibrium data. The maximum adsorption capacity for Ce3+, La3+, and Nd3+ were 99.42 mg g−1, 96.43 mg g−1, 118.10 mg g−1, respectively. Further, the thermodynamic analysis revealed that the interaction between ZSM-5 and Ce3+, La3+, and Nd3+ was favorable, spontaneous, and endothermic. The efficiency of ZSM-5 adsorbent was also studied in recovering several REEs from leachate of phosphogypsum wastes, and the data results proved its potency to do so. The findings reported in this work support the idea that ZSM-5 can be successfully used as an adsorbent to recover REEs from synthetic and real samples.

Study on using crystalline celluloses as templates for preparation of hierarchical LTA Zeolite for fast Cd(II) removal

Crystalline celluloses, such as microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC), which are originated from biomass, were utilized as templates to prepare hierarchical LTA zeolites. The effect of both size and surface properties of crystalline cellulose on the zeolite synthesis were carefully discussed. As-prepared zeolite based on surface-modification NCC showed hierarchical porous structure with monolithic morphology inherited from nanocrystalline cellulose. Its specific surface area was measured to be 18.3 m2/g, which was approximately 3.4 times that of the traditional zeolite A (Z0, 5.4 m2/g). Owing to its unique structure, ZNSC facilitated fast Cd(II) adsorption with the adsorption equilibrium time shortened by 81.3%. Kinetics study revealed that intraparticle diffusion was significantly enhanced and the effective diffusion coefficient increased by near 5 times. Furthermore, the maximum adsorption capacity achieved by ZNSC was 324.3 mg/g at 283 K, as calculated from the Langmuir model, which was 1.3 times that of Z0. These results are obtained when the grain size of ZNSC is larger than that of Z0, reflecting the superiority of the hierarchical structure in enhancing adsorption performance and thus providing a facile yet robust strategy for designing hierarchically structured zeolites for rapid and efficient wastewater treatment.

ZSM-5 Templated Porous Carbon: Synthesis and Characterization

Microporous zeolite ZSM-5 is prepared by the hydrothermal method, and its structure is tuned by changing the hydrothermal conditions. Then zeolite particles with uniform size and dispersion are etched into the hollow porous structures with an alkali solution to form zeolite templates. Porous carbon materials with ordered pore channels are acquired by the carbon deposition method (CVD). The detailed steps include introducing suitable carbon sources into the pore channels of the as-prepared zeolite templates, followed by carbon vapor deposition and continuous optimization of the deposition conditions, and finally, removing the template. The hollow porous structure of the carbon material facilitates the exposure of catalytic active sites and the improvement of diffusion kinetics. The hollow porous carbon (HPC) formed by carbon deposition perfectly inherits the structure and pore attributes of the hollow hierarchical zeolite ZSM-5. It can be further used as a carbon-based catalyst support.

Effects of Rare Earth Modifications on Structural Stability of HZSM-5 Zeolite

HZSM-5 zeolite modified by rare earth was prepared with ion exchange method in the study. The effects of different types of rare earth elements, modification temperatures, pH, and rare earth contents on structural stability of the as-prepared zeolite were investigated. The as-prepared zeolite was characterized by XRD, SEM and FT-IR spectroscopy. The characterization results showed that the crystal structure of the zeolite was not changed by the modification of rare earth, which was evenly distributed on the surface or in the pore channel of zeolite. Sm/HZSM-5 zeolite with the highest structural stability was obtained under the following modification conditions: 2% rare earth Sm, modification temperature of 70 °C, 2 h of ion exchange, and pH 3.

Atomic layer deposition precisely modified zeolite 13X: Physicochemical synergistic adsorption of space molecular contaminants

In spaceflight applications, molecular contamination control has become one of the most challenging issues. Porous zeolites are a potent molecular adsorbent with advantages of efficient adsorption at low pressure and/or high temperature, high interaction with adsorbates, and superior durability in extreme environments. Herein, zeolite 13X pellets were selected for adsorption of stearyl alcohol (C18H37OH) as a target molecular contaminant. Considering the excellent hydrophilicity of the zeolite 13X which limits the adsorption of most hydrophobic organic molecules, modification of the zeolite 13X by deposition of TiO2 via atomic layer deposition (ALD) technology was performed. Results show that ALD-grown TiO2 not only improves hydrophobicity but also renders high activity, whilst retains the hierarchical pores of the zeolites. As a result, the as-prepared zeolite 13X@TiO2 exhibits efficient adsorption toward trace stearyl alcohol under low pressure through the synergistic contribution of physisorption and chemisorption. Monte Carlo (MC) simulation, molecular dynamic (MD) and Density Functional Theory (DFT) calculations further discover that pore wall surfaces are primary adsorption sites for the physisorption while ALD-grown TiO2 provides active sites for the chemisorption.

Rapid synthesis of highly oriented hydrophobic silicalite-1 zeolite films on alloy steel at lower temperature for corrosion protection

• Rapid growth of oriented zeolite film on diverse substrates at lower temperature was studied. • Thickness of as-prepared zeolite films under three conditions is all around 1 μm. • Lower temperature leads to longer synthesis time and worse hydrophobicity of films. • Films prepared at 373 K for 4 h show terrific hydrophobicity and corrosion resistance. A method to quickly prepare highly oriented silicalite-1 zeolite films on different substrates at lower temperature was provided in this work. Compared with the traditional hydrothermal synthesis, rubbing a layer of seed pastes on the pretreated substrate surface in advance and using (NH 4 ) 2 SiF 6 as silicon source for subsequent secondary growth process can effectively reduce the synthesis temperature and shorten the contact time between the substrate and the strong alkaline synthesis solution. The thickness of the zeolite films prepared under three optimal conditions is all around 1 μm and the best contact angle value of 142.5° was achieved for the film prepared at 373 K for 4 h, while this values of the film prepared at 363 K for 6 h and 353 K for 10 h were 97.8° and 41.7°, respectively. The results of SECM showed that the detected localized current value of the film prepared at 353 K for 10 h was similar to that on bare steel after immersion in 0.62 M NaCl solution for 24 h (around 0.4 nA). At the same time, the current value measured under the other two preparation conditions was much higher, suggesting that the corrosion resistance of the film prepared under 353 K was unsatisfactory. In addition, EIS results demonstrated that the corrosion resistance of the films prepared at 363 K for 6 h also decreased significantly after 72 h immersion, while the films prepared at 373 K for 4 h still maintained excellent corrosion resistance and no obvious corrosion products were detected even immersion time up to 720 h. This work provides a new strategy for the application of zeolite in the field of material protection.

Experimental and computational evaluation of Ag-exchanged ZSM-5 and SSZ-13 for xenon capture

Ag-doped ZSM-5 and SSZ-13 zeolites were prepared synergistically by hydrothermal synthesis and liquid-phase ion exchange for the trace Xe and Kr capture by physical adsorption at room temperature and atmospheric pressure. The crystalline structure and textural characteristics of the as-synthesized samples were characterized by XRD, FT-IR, XRF, N2 physisorption and SEM in detail. Adsorption isotherms of Xe, Kr and N2 in the as-prepared zeolites were determined at 298 K to assess the adsorptive selectivities of Xe/N2 and Xe/Kr, and GCMC simulations were employed to investigate the adsorption mechanism of Xe in the Ag-exchanged zeolites. The results showed that Xe adsorption capacity and Xe/N2 selectivity in Ag-SSZ-13 are up to 2.22 mmol/g and 116 while those in Ag-ZSM-5 are evaluated to 1.97 mmol/g and 85 respectively, which are enhanced by the introduction of Ag+ ions greatly. The GCMC simulation revealed that the simulated isotherms are all fitted well with the experimental isotherm at the low-pressure range, and the electronic charge transfers from the Ag+ to Xe result in the adsorbed Xe mainly around Ag+ ions in zeolites, confirming that Ag+ ions are the adsorption sites to strengthen the Xe adsorption in zeolites.

Tetracycline degradation using combined system of dielectric barrier discharge air plasma and zeolites synthesized at different Na2O/SiO2 ratios

In this work, a combination of synthesized zeolite with a Dielectric Barrier Discharge (DBD) air plasma reactor was applied for the removal of tetracycline (TC) from effluents. The zeolites with different Na2O/SiO2 ratios were synthesized and inserted in a DBD reactor. The as-prepared zeolites were characterized by FTIR, SEM, BET, EDX, XRD, and TEM. The XRD results showed that the P-type zeolite turned to Y-type zeolite with an increasing Na2/SiO2 ratio from 0.5 to 1.5 and 2.5. The TC degradation experiments indicated that 79.1% of the initial TC was removed from the solution by the hybrid plasma- zeolite (Na2O/SiO2 ratio of 0.5) system after 45 min. The plasma in synergy with zeolite caused the changing amount of long-life oxidants in the system and converted it to higher reactive species. The combined system could reduce around 17 and 10% of the total organic carbon (TOC) and chemical oxygen demand (COD) more than the sole DBD system, respectively. Losing just 8% of the initial efficiency of the hybrid system after four successive runs revealed the stability of the proposed system. The radical trapping experiment method indicated that the role of •OH in the TC degradation was more critical than that of O2•−.

Synthesis of novel ZSM-22 zeolite from Taiwanese coal fly ash for the selective separation of Rhodamine 6G

The present study reveals the potential of coal fly ash (CFA) as the environmental pollutant adsorbent. The conventional approach of alkali fusion followed by hydrothermal treatment of Taiwan based coal fly ash resulted in new and novel zeolite material ZSM-22. The composition, morphology, chemical structure, and the surface properties of as-prepared zeolite were investigated using BET, SEM, FT-IR, XRD, and XRF. The specific surface area (SSA) of the zeolite is enhanced from 1.28 m2/g to 30.21 m2/g with a drop in Si/Al ratio of 3.1 to 2.4 suggesting the improvement of crystallinity. Further, the application of zeolite on the adsorption of the cationic dye Rhodamine 6G (R 6G) from aqueous solution in a batch process was investigated. Besides, the effect of parameters such as the effect of time, temperature, pH, dosage, agitation speed, kinetics, and isotherms on the removal of dyes was studied. The results indicate that adsorption of dye is more significant at pH = 6 indicating the zeolite surface is positively charged. The proficient sorption efficacy of R 6G onto ZSM-22 followed pseudo-second-order kinetic model and fits well with the Langmuir adsorption isotherm with maximum specific removal of 195.3 mg/g. Moreover, the possible adsorption mechanism for the selective separation of dye using CFA is mainly due to the electrostatic interactions and the hydrogen bonding. Finally, the key takeaways of the present research are that zeolite ZSM-22 is a prospective candidate as an adsorbent for the separation of dye molecules.

Light olefin production using the mixture of HZSM-5/MCM-41 and γ-Al2O3 as catalysts for catalytic pyrolysis of waste tires

In this paper, micro-mesoporous HZSM-5/MCM-41 zeolites were prepared by a two-step hydrothermal method using commercial HZSM-5 with two different silica/alumina ratios (38 and 50) as starting materials. The structures, morphologies and acidity of as-prepared zeolites were analyzed using XRD, FT-IR, SEM, N2-adsorption/desorption and NH3-TPD. The HZSM-5/MCM-41 zeolites combined the acidity of microporous HZSM-5 with the pore advantages of mesoporous MCM-41. Mesopores and microspores of 3.34 and 0.95 nm in diameter were found to be present in HZSM-5/MCM-41 zeolites. When they were used to catalyze the pyrolysis of waste tires, the selectivity of light olefins for HZSM-5/MCM-41 prepared using HZSM-5 with the silica/alumina ratio of 50 as starting materials was 21.42%, higher than 18.43% of HZSM-5/MCM-41 synthesized using HZSM-5 with the silica/alumina ratio of 38. In order to further overcome the pore size constraints and mass transfer limitations of HZSM- -5/MCM-41 zeolites for catalyzing pyrolysis of waste tires, macroporous ?-Al2O3 were mixed with HZSM-5/MCM-41 and used as catalysts. The selectivity to light olefins for the mixture of ?-Al2O3 and HZSM-5/MCM-41 prepared using HZSM-5 with the silica/alumina ratio of 50 as starting materials was 33.65%, which was obviously enhanced by the introduction of ?-Al2O3.

1999P - Impact of tumor reoxygenation by nanoparticles on tumor associated macrophages (TAMs)

BackgroundGlioblastoma (GB), a highly hypoxic brain tumor (Bekaert et al. 2017), is characterized by a massive macrophage (MΦ) infiltration (Lapa et al. 2015). Hypoxia triggers a shift to a pro-tumoral M2 phenotype in GB (Leblond et al. 2016). Thus, strategies aiming to reduce hypoxia could promote an anti-tumoral M1 phenotype. Among these reoxygenation strategies, we recently developed a new approach with zeolites nanoparticles. These zeolites are able to carry hyperoxic/hypercapnic gases and release them according to a hypoxic gradient. We have demonstrated that the charge balancing cation changes affinity to the gases but also the ability to track zeolite with MRI. Our objective is to study the reoxygenation efficacy of zeolites specifically in the GB and to evaluate their impact on tumor associated MΦ with in vitro and in vivo studies. MethodsFaujasite zeolites (FAU, ∼20nm of diameter) were used and modified by ion exchange with various cations (Fe, Gd, Cu, Ag). GB model was obtained by orthotopic glioblastoma cells implantation (U251) in nude rats (ONCOModels/Unicaen). 7T MRI (Bruker/Cyceron) was used to follow zeolites after intravenous injection and for oxygen measurement. Murine bone marrow derived MΦ were prepared and polarized to M1 and M2 using LPS/IFNg or IL4 as previously described (Leblond et al. 2016). Zeolites were added in MΦ medium and their impact on MΦ were evaluated by crystal violet dye assay, flow cytometry (Plateau ICORE/Unicaen) and polarization assays. ResultsOur results show that zeolites are able to accumulate and release the carried gases specifically in the brain tumor leading to tumor reoxygenation. Regarding the effect on MΦ, our preliminary results show, in vitro, the safety of as-prepared zeolites or Fe, Gd or Cu dopped zeolites on M0, M1 and M2 MΦ cultures. Similarly, no alteration of the cell cycle was observed. As a positive control of cell death, the presence of Ag-dopped zeolites dramatically decreased M0 and M1 MΦ viability. ConclusionsZeolites can deliver oxygen to the brain tumor and may improve the effectiveness of conventional treatments. Zeolites do not exhibit toxicity on primary cultures of MΦ. Additional studies are underway to evaluate the effect of zeolites on the polarization of MΦ, both in vitro and in vivo. Legal entity responsible for the studyThe authors. FundingRégion Normandie, CNRS, Université de Caen Normandie, Ministère de l’Enseignement Supérieur et de la Recherche, European Union-Fonds Européen de Développement Régional (FEDER), HABIONOR European project, co-funded by the Normandy County Council, the French State in the framework of the interregional development Contract “Vallée de la Seine” 2015-2020, ARCHADE, Fédération pour la Recherche sur le Cerveau (FRC) et INCa (INCA-11699). DisclosureAll authors have declared no conflicts of interest.

Facile synthesis of Sn-containing MFI zeolites as versatile solid acid catalysts

Sn-containing MFI zeolites with controllable Al contents were successfully synthesized with the utilization of the EDTA-Sn complex as tin source and citrate as buffer solution for the first time. The elaborately strategy achieves a right release of Sn4+ ions rate to combine with the silicon tetrahedron species in the synthesis process which could make the heteroatom tin warmly incorporate into the zeolite frameworks. The structural information about the Sn-containing MFI zeolites was confirmed by XRD, FTIR, and solid-state NMR spectroscopy. Characterization results of HRTEM, FTIR, XPS, and UV-vis spectroscopy illustrated that most Sn species exist as isolated tetrahedral Sn(IV) in the as-prepared zeolites. The creation of Lewis acid sites in Sn-MFI and Sn-Al-MFI zeolites, and Brønsted acid sites in Sn-Al-MFI zeolites were determined by FTIR spectroscopy of pyridine adsorption and 1H and 31P MAS NMR spectroscopy after ammonia and trimethylphosphine oxide (TMPO) adsorption. Both the Sn-MFI and Sn-Al-MFI zeolite catalysts exhibit a remarkable catalytic performance in the conversion of dihydroxyacetone (DHA) to methyl lactate (ML), while the bifunctional Sn-Al-MFI catalyst exhibits a significant combination effect, and a remarkable active site-based turnover frequency with a high methyl lactate productivity can be achieved.

Synthesis of zeolite nanostructures from waste aluminum cans for efficient removal of malachite green dye from aqueous media

Different zeolite nanostructures were synthesized from waste aluminum cans via a low-cost hydrothermal method using different silicon sources. The produced nanostructures were identified using XRD, FT-IR, SEM, and TEM analyses. XRD proved that the samples which synthesized using fumed silica and sodium metasilicate consist of a composite of (analcime, hydroxysodalite, and zeolite P1) and (sodium aluminum silicate hydroxide hydrate and nepheline hydrate), respectively. Moreover, the samples which synthesized using silica gel and tetraethyl orthosilicate composed of LTA zeolite and a composite of (sodium aluminum silicate hydroxide hydrate and zeolite 4A), respectively. The as-prepared zeolite nanostructures were tested in the removal of malachite green dye from aqueous media using a batch method. The results revealed that the adsorption processes fitted well with the pseudo-second-order kinetic model and Langmuir adsorption isotherm. In addition, the mechanism of adsorption processes was controlled by three successive stages, namely inner diffusion, outer diffusion, and pore diffusion processes where the pore diffusion is the rate-determining step. Additionally, thermodynamic parameters showed that the adsorption processes were spontaneous, physisorption, and exothermic.

Fluorescent Ag+-exchanged zeolite nanoparticles with improved photoluminescence properties via X-ray irradiation

Fluorescent Faujasite (FAU)-Y Ag+-exchanged zeolite is a lanthanide-free phosphor with a high photoluminescence (PL) quantum yield to convert near-ultraviolet (near-UV) to visible light. Here, we focused on nanometer-sized fluorescent FAU Ag+-exchanged zeolite as a wavelength converter for optoelectronic devices. The prepared Ag+-exchanged zeolite nanoparticles were irradiated with X-rays to improve their PL properties because X-ray irradiation does not possess the disadvantages of other treatments, such as aggregation and sintering of nanoparticles exposed to thermal treatment, excessive growth of silver particles with visible light absorption following chemical reduction, and amorphization of zeolite by high-energy electron beam irradiation. FAU-Y zeolite nanoparticles were prepared by template-free hydrothermal synthesis and then fluorescent Ag+-exchanged zeolite nanoparticles were obtained through the ion exchange of Na+ with Ag+. The prepared Ag+-exchanged zeolite nanoparticles were irradiated by X-rays from a commercial tabletop device. The average size of the as-prepared zeolite nanoparticles was 35.7 ± 12.6nm according to transmission electron microscopy (TEM) images. TEM also confirmed that Ag-related particles such as silver clusters and/or silver nanoparticles were generated and grew from Ag+, possibly through reduction accompanied with oxidation of oxide ions of the zeolite framework during X-ray irradiation. PL quantum efficiency was enhanced by X-ray irradiation by up to ~3 times. Analysis of PL properties and electron spin resonance spectra implied that fluorescent Ag42+ clusters were formed under X-ray irradiation, resulting in the enhancement of PL quantum efficiencies. Similar behavior was also observed for micrometer-sized Ag+-exchanged zeolites. X-ray irradiation of fluorescent Ag+-exchanged zeolites is therefore a useful method to improve their PL properties.

Hydrothermal tuning of the morphology and crystallite size of zeolite nanostructures for simultaneous adsorption and photocatalytic degradation of methylene blue dye

We herein have reported on tuning of the morphology and crystallite size of the hydrothermally prepared zeolite nanostructures by using different aluminum sources. The investigation revealed that aluminum sulfate and aluminum chloride precursors produced non-crystalline forms, while aluminum isopropoxide, alumina, and aluminum metal precursors generated analcime nanoparticles with crystallite size of ca. 94.79, 112.57, and 105.87nm, respectively. However, sodium aluminate precursor gave a mixture of analcime and nacrite phases with a crystallite size of ca. 77.95nm. The as-prepared nanostructures were identified using XRD, FT-IR, FE-SEM, EDS, UV–Vis spectroscopy and BET surface area. The results exhibited that the direct optical energy gaps (Eg) and BET surface area were found to be (3.29eV and 20.18m2/g), (3.15eV and 16.28m2/g), (3.21eV and 18.67m2/g), and (2.69eV and 17.82m2/g) for the zeolite products prepared using aluminum isopropoxide, sodium aluminate, alumina, and aluminum metal precursors, respectively. The results also showed that the as-prepared zeolite nanostructures could be simultaneously used as adsorbents and photocatalysts for the removal of methylene blue (MB) dye from aqueous solutions. The adsorption of methylene blue dye over the zeolite adsorbents obeys pseudo-second-order model and intra-particle diffusion model. Interestingly, zeolite photocatalyst prepared using aluminum isopropoxide degraded the MB dye with percentage of 85% and 100% within 180 and 110min in the presence of UV and (UV+H2O2), respectively. The degradation processes followed the pseudo-first-order model. The prepared zeolites are proposed as promising candidates for the removal of MB from aqueous media.

Environmentally benign alcoholysis of urea and disubstituted urea to alkyl carbamates over alkali-treated zeolites

Alkali-treated zeolite material was prepared by using 0.1–0.4 mol/L NaOH aqueous solution, as characterized by XRD, SEM, N2 adsorption-desorption technique and ammonia-temperature programmed desorption (NH3-TPD). The as-prepared zeolite was found to be an effective catalyst for alcoholysis of urea and disubstituted urea to produce alkyl carbamate, getting 91.8–100% conversion of urea and substituted urea with >98.0% selectivity to alkyl carbamates. The results indicated that the high reactivity of the zeolites for alcoholysis of urea and N-substituted urea could be mainly ascribed to the enhanced specific area and balance between acidic and basic sites on the HZSM-5 surface caused by the alkali-treatment. This catalyst can be easily recovered and reused.

Catalytic cracking of n-dodecane over hierarchical HZSM-5 zeolites synthesized by double-template method

Hierarchical HZSM-5 zeolites have been prepared by a double-template method with tetrapropylammonium hydroxide and polydiallydimethylammonium chloride (PDDA) as micro- and meso-scale template, respectively, and Al(NO3)3 as aluminum source. The as-prepared zeolites were characterized by XRD, SEM, TEM, N2-adsorption–desorption, TGA, ICP, in situ FT-IR and NH3-TPD. The hierarchical HZSM-5 zeolite prepared at the PDDA/TEOS weight ratio of 0.2 in the synthesis gel (HZ-0.2P) had uniform mesopores (11–13 nm) and high acid site accessibility. An increase of the PDDA/TEOS resulted in enlargement of mesopore size and broadening of size distribution, together with appearance of some non-uniform accumulation pores. Moreover, the accessibility of acid sites in hierarchical HZSM-5 decreased. Catalytic cracking of n-dodecane carried out at 500 °C and 4 MPa in a wall-coated tubular reactor with HZSM-5 zeolites showed that HZ-0.2P exhibited the superior catalytic activity and stability, with the increase higher than 20% in the conversion of n-dodecane and reduction to ca. 1/2 in the deactivation rate compared with micro-porous HZSM-5 zeolite. This could be ascribed to its highest acid site accessibility, which improves the diffusion of n-dodecane and its cracking product molecules inside pore channels of catalyst.

Methyl Acetate Synthesis by Esterification on the Modified Ferrierite: Correlation of Acid Sites Measured by Pyridine IR and NH3-TPD for Steady-State Activity.

The amounts of Brønsted acid sites on K, P, and Zr-modified microporous Ferrierite zeolite were investigated through pyridine FT-IR and NH3-TPD analyses. P-modified Ferrierite showed a superior catalytic activity for methyl acetate synthesis by esterification of methanol and acetic acid. The catalytic activity at steady-state with the acidic properties of as-prepared catalysts was well correlated with the results of pyridine FT-IR (intensity ratio of Brønsted acid sites to total acid sites) compared with that of NH3-TPD. The results can suggest the proper and simple method to estimate the esterification activity at steady-state using the measured acid sites on the as-prepared zeolites.

Biodiesel Produced from Catalyzed Transesterification of Triglycerides Using ion-Exchanged Zeolite Beta and MCM-22

In this work, biodiesel production from catalyzed transesterification of triglycerides with excess methanol was studied by using ion-exchanged Zeolite Beta and MCM-22 as heterogeneous catalysts. Zeolite Beta and MCM-22 were synthesized with hydrothermal processes and, subsequently, modified by ion-exchanged with alkali ions. These as-obtained zeolite catalysts could yield a high conversion of triglycerides to biodiesel. The conversion efficiency was largely affected by crystallinity and frameworks of zeolite support, pH value of alkali ion-exchange solutions and alkali loadings onto the zeolite support. Furthermore, the effects of the duration of the sodium ion-exchange process on the final conversion efficiency of triolein to biodiesel, both the as-prepared Zeolite MCM-22 and Zeolite Beta catalysts were used. The effect of the duration of the sodium ion-exchange process is insignificant in transesterification using Na-ion-exchanged Zeolite MCM-22 catalysts from 0.5 to 4h. In contrast, the conversion efficiency of triolein to biodiesel reached ca. 95% in 0.5hours of transesterification using Zeolite Beta ion-exchanged with 3 mmol-eq. Na+/g cat for 0.5hours.

Synthese of Cancrinite from Alkali-Fused Fly Ash by “Dry Method”

In this study, zeolite was prepared from fused fly ash with very little water treatment. The as-prepared zeolite was characterized by X-ray diffraction (XRD) and scanning electron microscope. XRD results showed that cancrinite was the major phase in the product. The influence of preparation conditions on the yield of zeolite was described. Experiments showed that the crystallization time of zeolite became shorter and the crystallinity of cancrinite became higher with the increase of NaOH dose in fusion stage. Based on the fact that the water was not enough to be as the solvent which was different from conventional method, it can be concluded that the synthesis mechanism of zeolite from fused fly ash is the Solid-state Conversion Theory.