Zeolite 4A Research Articles

Electrostatically driven kinetic inverse CO2/C2H2 separation in LTA-type zeolites

The identical molecular size and similar physical properties of carbon dioxide (CO2) and acetylene (C2H2) make their adsorptive separation extremely challenging to achieve with most adsorbents. Reports on the separation of CO2 and C2H2 mixtures by zeolites are even rarer with the mechanism of adsorptive separation requiring further exploration. In this paper, we report that ion modulation of zeolite 5A promotes the difference in kinetic diffusion of CO2 and C2H2, realizing the inverse separation of zeolite from selective adsorption of C2H2 to selective adsorption of CO2. Creating a compact pore space restricting the orientation of gas molecules enables charge recognition. The positive electrostatic potential at the pore openings was utilized to hinder the diffusion of C2H2 between the cages while ensuring the transfer of CO2, increasing their diffusion differences in pore channels and leading to the CO2/C2H2 kinetic selectivity of 31.97. Grand canonical Monte Carlo (GCMC) simulation demonstrates that the CO2 distribution in K-5A-β is significantly higher than that of C2H2. Dynamic breakthrough experiments verify the excellent performance of material in practical CO2/C2H2 separation, for CO2/C2H2 (50/50 and 1/99, V/V) mixtures can be separated in one step, thus directly generating high purity C2H2 (> 99.95%), which provides a promising thought for the zeolite-based separation of CO2 and C2H2.

تحضير معقدات جديدة لمثيل ميثا اكريلت مع بولي فنيل الكحول ودراسة بعض التطبيقات البيئية .

A new copolymer from Methyl methacrylate and polyvinyl alcohol [methyl-5-hydroxy-2-methylhexanoate] and its complexes were synthesized for some metals (Cr+3, Mn+ 2, Fe+ 3, Co+ 2, Ni+ 2, Cu+ 2, Zn+ 2, Cd+ 2). This ligand and its metal complexes were characterized using (FTIR) spectral, UV-Vis spectroscopy, conductivity, magnetic moment, and Thermo Gravimetric analysis. The nanoparticles for two complexes were characterized using x-ray diffraction, scanning electron microscope, and atomic force microscope. Zeolite 5A was prepared from local kaolin by hydrothermal preparation, then characterization, and used as a supporting material with prepared copolymer as a composite to remove several metals from polluted water taken from industrial water electric power stations in Dora and South of Baghdad. Trace concentrations of these metals were estimated before and after applying the prepared copolymer by atomic absorption spectroscopy. The removal using composite materials is significantly more effective, with the concentration recorded as very low and the concentrations of some metal ions like Fe+2, which completely disappeared from polluted water according to a polluted water analysis before and after using the produced compounds.

Sorption enhanced DME synthesis by one-step CO2 hydrogenation

DME synthesis by direct CO2 hydrogenation was studied on physical mixture of commercial CuZnO/Al2O3 (CZA) and in-house synthesized PTA (phosphotungstic acid)/γ-Al2O3 catalysts. Effects of PTA loading (0–50 % by mass) and relative amounts of the catalysts on CO2 conversion and DME yield were investigated. The process was intensified through integration of in-situ steam separation by Zeolite 3A (Z3A) adsorbent mixed with the catalysts. Experiments were run at 498 K, 30 bar, H2:CO2=3:1 and GHSV=1750 h−1 (based on CZA catalyst). Optimum PTA loading and CZA:PTA/γ-Al2O3 mass ratio were 30 % and 1:2, respectively, that gave ∼21 % CO2 conversion and 6.3 % DME yield. These values remained below the respective thermodynamic limits (28.5 % and 21 %), which were exceeded upon adsorbent integration. Catalytic performance depended strongly on adsorbent quantity studied at the catalyst (CZA+PTA/γ-Al2O3):adsorbent mass ratio range of 1:0.33–4. Catalysts and the adsorbent remained stable during the pressure swing driven adsorption-regeneration cycles. Sorption assistance at catalyst:adsorbent ratio=1:4 increased catalyst productivity from 5.5×10−3 to 2×10−2 kgDME h−1 kgcat−1. The latter value was comparable to those of the sorption enhanced CO2+CO hydrogenation systems due to the PTA-based dehydration catalyst with strong acidic features and was promising when the strong thermodynamic limitations of CO2-DME conversion was considered.

Synthesis of Low-Silicon X-Type Zeolite from Lithium Slag and Its Fast Exchange Performance of Calcium and Magnesium Ions.

Without the addition of silicon and aluminum sources, a pure-phase KNaLSX zeolite was successfully synthesized from the residue (lithium slag), which was produced from spodumene in the production process of lithium carbonate. The KNaLSX samples were characterized by an X-ray Diffractometer (XRD), Scanning Electron Microscope (SEM), X-ray Fluorescence Spectrometer (XRF), Thermogravimetric Differential Thermal Analysis (TG-DTA), Fourier Transform Infrared Spectrometer (FT-IR), and N2 adsorption measurement. The ion exchange capacity and the ion exchange rate of calcium and magnesium ions were measured as used for a detergent builder, and the results were compared with the standard zeolites (KNaLSX and 4A). The experimental results show that the pure-phase KNaLSX synthSynthesis and characterization of co-crystalline zeolite composite of LSX/esized from lithium slag has a SiO2/Al2O3 ratio of 2.01 with a grain size of 3~4 μm, which is close to the commercial KNaLSX sample of a SiO2/Al2O3 ratio of 2.0. The BET-specific surface area of KNaLSX is 715 m2/g, which is larger than the low-silicon X-type zeolite (LSX) synthesized from waste residue reported in the literature. The ion exchange rate constant of calcium and magnesium ions in KNaLSX is 5 times and 3 times that of 4A zeolite, respectively. KNaLSX also has a high ion exchange capacity for magnesium ion of 191 mgMgCO3/g, which is 2 times than that of 4A zeolite, and a high ion exchange capacity for calcium ion of 302 mgCaCO3/g, which meets the first-grade standard of zeolite for detergent builders in China. The work provides the basis for high-value resource utilization of lithium slag and the development of a detergent builder for rapid washing.

Recycling of an industrial waste used for the disposal of organic compounds in a fixed bed column

Molecular sieves 4A zeolite are materials used to dehydrate natural gas in liquefaction plants (LNG) in Algeria. After several cycles of regeneration and reuse, their structures degrade and affect their performances. Once replaced by new ones, they will be stored within the plant as an industrial used 4Azeolite (U4AZ). The aim of this study is to investigate the possibility of using U4AZ as an adsorbent for removing phenol and ethanol from aqueous solutions in a fixed bed column. Breakthrough curves were plotted for the adsorption of ethanol and phenol on the adsorbent U4AZ by varying initial concentrations (281, 444 mg/L) and contact time for constant flow rate (0.5 mL/min). The experimental data were fitted by empirical relationship based on Bohart-Adams model. The obtained correlations were in good agreement with the experimental breakthrough curve data. This investigation indicated that U4AZ could be used as a recyclable material to remove phenol and ethanol from aqueous solution by adsorption.

Description of non-ideal effects in composite membranes by a new theoretical approach

In present study, a theoretical model is introduced to calculate the gas permeability of mixed matrix membranes (MMMs) containing porous fillers. This model is based on analogy of gas permeation in MMMs with tensile modulus in composites. The representative parameters of MMM morphologies such as polymer chains tightening around the filler (β<1), unselective channel formation (β>1) and polymer chains penetrating into filler pores (0≤α≤1) which leads to the filler pore blocking are all included in the model. Furthermore, the interphase thickness (t) which is a critical parameter of MMMs participates in calculation equation along with the other parameters. To validate the proposed model, an experimental study with poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend as polymer matrix and zeolite 4A and NH2-MOF-199 as fillers is performed. The obtained gas permeability data of constructed MMMs and some of the literature data are employed to be fitted with the proposed model. The details of the existence morphologies of MMMs can be described by earning the mentioned parameters ranges. Therefore, by this model, by having a measure of t, the gas permeation of MMM can be achieved accompany with details of the related morphologies. All the theoretical investigations are done utilizing one equation which contains all parameters simultaneously.

Experimental PSA reactor for methanol-enhanced production VIA CO2 hydrogenation

Methanol synthesis via catalytic CO2 hydrogenation has emerged as one of the main ways to valorize CO2. The main problem is that the methanol synthesis reaction is thermodynamically controlled, and there is a parallel endothermic reaction, reverse water gas shift (RWGS), so low methanol production ratios are achieved.In this scenario, process intensification, particularly multifunctional reactors where reaction and separation occur simultaneously, is of great interest. Sorption-enhanced reaction processes (SERP) technologies are widely used in equilibrium-controlled processes to increase reagent conversion through selective product removal.Various authors have proposed SERP processes for CO2 hydrogenation to methanol, but most of them are simulations studies and it is difficult to find experimental data. The aim of the work is the experimental study of the CO2 conversion and selectivity to methanol of a SERP process based on a four-step PSA reactor. The process has been carried out with a commercial Cu/ZnO/Al2O3 catalyst and commercial 3A zeolite as adsorbent.Conversions beyond the equilibrium have been achieved in the SERP process, even complete conversion of CO2 at 50 bar, 250 °C, and 300 °C. In the cyclic process, high CO2 conversions far from equilibrium are achieved in all the range of temperatures, 200–300 °C. The best results of methanol yield are achieved at 250 °C and 50 bar, followed closely by 200 °C. It is worth mentioning that methane is detected in the transitory state at 300 °C and 50 bar. Also, the purge step has been studied, concluding that it is necessary for adsorbent regeneration, improving CO2 conversion in the cyclic steady state.

Zeolites synthesis from phyllosilicates and their performance for CO2 adsorption

Five phyllosilicates (kaolinite, montmorillonite, saponite, sepiolite and palygorskite) have been selected as starting materials for the synthesis of zeolites. Among them, kaolinite and montmorillonite display the lowest Si/Al molar ratio leading to aluminosilicates with high crystallinity. Thus, the hydrothermal treatment under basic conditions forms 4A zeolite when kaolinite is used as starting material while 13X zeolite is obtained when montmorillonite is used as starting material. The microporosity and CO2-adsorption capacity of the prepared zeolites are directly related to its crystallinity. Thus, in order to improve it, raw phyllosilicates were subjected to a microwave-assisted treatment to remove undesired Mg or Fe-species, which have a negative effect in the assembling of the zeolites by hydrothermal basic conditions in a second step. The highest adsorption value was 3.85 mmol/g at 25 °C and 760 mm of Hg for Mont-A-B sample after the consecutive treatments.

Experimental demonstration of a sorption-enhanced methanation (SEM) cyclic process on a lab-scale TRL-3 fixed bed reactor

In this work, the scaling-up of the sorption-enhanced methanation (SEM) process to a TRL-3 fixed bed reactor has been demonstrated. The SEM process for synthetic natural gas (SNG) production consists mainly of two stages: in the first stage, the zeolite facilitates the removal of a product from the methanation reaction, thereby enhancing CO/CO2 conversion; in the second stage, zeolite regeneration takes place. The functional materials chosen were a zeolite 4A and a Nickel-based catalyst, selected for their high H2O adsorption capacity and high catalytic activity, respectively. Various operational variables, including temperature and pressure, were optimized during both SEM and regeneration stages to enhance the performance of the process. Optimum regeneration conditions consisted of pressure swing operation—from 10 bar during the SEM reaction to atmospheric pressure—while maintaining a constant temperature at 230°C. These operating conditions were tested for more than 20 SEM/regeneration cycles using a feed gas containing H2/CO/CO2. Stable performance throughout the cycles was fulfilled, reaching a CH4 purity of 100 % during 25 min during SEM for the operating conditions chosen. Finally, the number of reactors needed to obtain a continuous stream of CH4 was calculated resulting in a process productivity of 8.00×10-4 molCH4/kgcat·s.

Re-examination of the intumescence mechanism of ammonium polyphosphate/pentaerythritol/zeolite 4A fire-retarded formulation using advanced spectroscopic techniques

The mixture of ammonium polyphosphate and pentaerythritol is a very efficient intumescent system suitable for polyolefins, especially polypropylene. In this article, the intumescence mechanism of this intumescent system with and without zeolite 4A used as a synergy agent is revisited. The intumescent system was investigated in depth using continuous-wave electron paramagnetic resonance spectroscopy, solid-state nuclear magnetic resonance, and the advanced technique, namely hyperfine sublevel correlation pulsed electron paramagnetic resonance. It was observed that the char generated between 250°C and 350°C is made of polycyclic heterocyclic radicals with nitrogen atoms and that free radicals are mainly generated at these temperatures with a spin concentration relatively stable at least up to 500°C. Moreover, the presence of hydrogen, carbon, nitrogen, and phosphorus was clearly evidenced in the chemical environment of free electrons at 350°C (hyperfine sublevel correlation pulsed electron paramagnetic resonance). Besides, it was also evidenced that 4A totally collapses below 250°C. Contrary to previous works suggesting the presence of aluminosilicophosphate complexes, this work demonstrated that distinct alumino- and silicophosphate complexes are generated and protected the residue at high temperatures.

Comparative analysis of CO2 and N2 adsorption on zeolite 4A: Thermodynamics parameters and site energy distribution investigations

Adsorption equilibrium data for CO2 and N2 on zeolite 4A were volumetrically measured at temperatures ranging from 278 K to 328 K and gas pressures up to 4 MPa. The experimental data was correlated using the high-pressure Langmuir, Sips, and DA adsorption isotherm models. The high-pressure DA model was found to be the optimal model for describing the adsorption isotherms on basis of nonlinear regression analysis. Subsequently, the thermodynamic parameters, including isosteric heat of adsorption (Hst), adsorption phase specific heat capacity (cpa), adsorption phase entropy (sa), and enthalpy (ha), considering the actual adsorption state, were estimated. The results demonstrate that the adsorption of CO2 on zeolite 4A is greater than that of N2. The higher Hst and ha values and the lower sa values of CO2 compared to N2, suggest a stronger surface interaction of CO2 with zeolite 4A, resulting in a more ordered arrangement of CO2 molecules than N2. Site energy distribution theory analysis indicates that less energy is required for CO2 adsorption and greater site energy heterogeneity of CO2 than those of N2 on zeolite 4A. The obtained results evidence that the studied zeolite 4A could be a promising candidate adsorbent for greenhouse gas capture.

Green nanomaterial-based adsorbent for Cs and Pb removal: Synthesis from industrial waste producing high-value products

ABSTRACT The search for a sustainable society makes necessary the reuse of residues contributing to the producing high-value product. Producing new materials with high-added value increases technological development and builds up new applications. The present study aimed to use residue from the alumina industry and coal ash generated in thermal plants in energy production to synthesize zeolite for wastewater treatment to remove Cs and Pb. Two types of nanomaterials were synthesized: zeolite 4A (ZEA) and zeolite sodalite (ZSD). The Cs adsorption efficiency achieved 73% and 9.4% for ZEA and ZSD, respectively, fitting better for Lineweaver-Burk isotherm and both zeolites removed 100% of Pb from synthetic solutions. Results here reported may be used to design novel wastewater treatment systems from nuclear plants and other industrial processes. The present study can contribute to achieving Sustainable Development Goals 9, 11, and 12.

High performance and antifouling zeolite@polyethersulfone/cellulose acetate asymmetric membrane for efficient separation of oily wastewater

Microfiltration membranes have emerged as a promising alternative for oily wastewater treatment due to their high efficiency, low cost, and ease of operation. In this study, polyethersulfone (PES), cellulose acetate (CA), and 4A zeolite were blended to fabricate asymmetric membranes by the phase inversion technique and examined in oily wastewater treatment. Kerosene was chosen as a model polluting oil. The fabricated pure PES membrane (P), PES membranes incorporating 4A zeolite (ZP), PES membrane blended with CA (PC), and PES/CA blended membranes with 4A zeolite (ZPC) were characterized using field emission scanning electron microscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, porosity, and contact angle to study the structure properties of these membranes. The performance of membranes was examined by water permeation, oil permeation flux, oil rejection, flux recovery ratio, and relative flux reduction. The ZPC membranes showed the highest performance in comparison with other prepared membranes. Incorporating 4A zeolite nanoparticles with 0.5 wt% into the PES/CA blended membrane significantly enhanced the microfiltration performance and decreased the contact angle of the P membrane from 70° to 29.8°. The effect of operation parameters such as transmembrane pressure (1–4 bar), feed temperature (25–50 ºC), and concentration of oil feed solution (250–1000 mg/L) on the permeation flux and oil rejection was studied on the PES/CA blended membrane containing 0.5 wt% 4A zeolite (0.5%ZPC). The 0.5%ZPC membrane showed improved porosity of 87.7% and it gave the highest value of pure water flux of 91.1 L/m2.h, oil permeation flux of 75.55 L/m2.h, maximum oil rejection of 98.8%, flux recovery ratio of 97.7%, and relative flux reduction of 21.8%. The permeation flux given by the 0.5%ZPC membrane was improved by about 8 times that of the P membrane. Re-usability studies verified the durability of the blended membranes and their performance in oily wastewater treatment.

Development and testing of lab-scale atmospheric molecular sieve bed with zeolite 4A adsorbent

Tritium Extraction System (TES) is one of the most important systems of fusion blanket. The two basic systems of TES are Atmospheric Molecular Sieve Bed (AMSB) and Cryogenic Molecular Sieve Bed (CMSB). AMSB removes ppm levels of water vapour (Q2O), while CMSB removes hydrogen isotopes (Q2), oxygen, and nitrogen from helium purge gas. Though detailed parametric study of AMSB is very important for fuel cycle technology, such studies are very limited. In this work, a lab-scale AMSB is designed and developed at Institute for Plasma Research, Gandhinagar, using Zeolites 4A as an adsorbent material. Experimental break through curves for the adsorption of various concentrations of moisture (H2O) (up to ∼20,000 ppm) at flow rates (1–3 NLPM) from helium gas at room temperature have been generated and compared with theoretical estimation. Adsorption capacity of lab scale AMSB has been estimated at various operating conditions. The effects of the initial moisture concentrations and flow rates on breakthrough curves are studied in detail.

Florfenicol removal from veterinary pharmaceutical effluents: Tri-metallic zeolite 5A° for electrochemical oxidation and catalytic ceramic membrane separation

Contaminants of emerging concern, including pharmaceuticals, are commonly found in wastewater from households, farms, and healthcare facilities. When active pharmaceutical ingredients enter water sources, they contaminate the waterways and cause potential hazard effects on the aquatic environment and human populations. This concern is especially critical with antibiotics, due to the development of antibiotic-resistant bacterial strains. However, Florfenicol, a bacteriostatic antibiotic widely used in veterinary medicine, poses a significant risk of water pollution when discharged into waterways. In the present study and its practical application, removal of targeted pollutant namely antibiotic florfenicol by ozonation was investigated by measuring chemical oxidation demand (COD), biochemical oxygen demand (BOD), and turbidity for pharmaceutical wastewater in the batch reactor, while optimizing feeding electro flocculation voltage, O3 flow rate, O3 dosage and ceramic membrane filtration. Due to the production of hydroxyl radicals with strong oxidation properties, pollutants in wastewater can be effectively degraded via heterogeneous catalytic ozonation. It was examined whether the regenerated catalyst exhibited good catalytic activity after three cycles of washing with Milli-Q water and ethanol. The results show that the effluent concentration of antibiotic Florfenicol is about 99% alongside residual values for 91%, 79%, and 89% for COD, BOD, and turbidity, respectively (Time: 30 min, pH: 7.5). Meanwhile, the wastewater's degradability capacity (BOD5/COD ratio) increased from 0.37 to 0.53, rendering it more readily biodegradable for further treatment. These results indicate that the process of hybrid electro flocculation and catalytic ozonation with ceramic membrane has a high treatment efficiency for veterinary antibiotics, and a continuous-flow reactor can be utilized more practically for a full-scale industrial application.

Utilization of Bengkalis Beach Sand Silica as Raw Material in the Synthesis of Zeolite 4A

Zeolite 4A is a porous material that is widely used as an adsorbent, catalyst, membrane, ion exchanger, molecular sieve, etc. As a source of silica in the synthesis of zeolite 4A, silica from natural materials, biomass waste or chemicals has been used. In this research, silica extracted from Bengkalis beach sand (BBS) was used as raw material. The silica content in its oxide form, silicon oxide (SiO2) in BBS reaches 90%. The synthesis of zeolite 4A was carried out using a hydrothermal process, by varying the mole ratio of Si/Al from the reactant sodium silicate to sodium aluminate, namely 1.2:1; 1.4:1; 1.6:1 at reaction temperatures of 100, 110 and 120°C. Based on characterization using X-ray diffraction and an infrared spectrometer, the best conditions were obtained at a mole ratio reactant of 1.6, a reaction temperature of 100°C with a crystallinity percentage reaching 80.97%. Based on SEM-EDX analysis, the zeolite has an agglomerated morphology with a Si/Al ratio of around 1.09. The surface area, pore volume, and pore diameter of the synthesized zeolite were analyzed using a Brunauer-Emmet-Teller (BET) technique, respectively 81.844 m2/g, 0.039 cm3/g, and 3.07 nm.

Simultaneous degradation of methyl orange and indigo carmine dyes from an aqueous solution using nanostructured WO3 and CuO supported on Zeolite 4A

In this study, a novel composite catalyst system, Zeolite 4A/WO3/CuO with a Z-scheme design, was synthesized for photocatalysis, sonocatalysis, and sono-photocatalysis methyl orange (MO) and indigo carmine (IC) dyes simultaneously. The properties of the Zeolite 4A/WO3/CuO composite were thoroughly investigated using various techniques, and the results confirmed the synthesis of the desired catalyst system. In the sono-photocatalytic process, using the Zeolite 4A/WO3/CuO composite, the maximum efficiency for MO (99.12 %) and IC (97.24 %) was achieved at pH of 2 and 3, with a catalyst dosage of 0.15 g/L, a dye concentration of 10 mg/L, a contact time of 25 min, and H2O2 dosage of 30 µL/100 mL. The dye elimination efficiency using the sono-photocatalytic process was reduced in the presence of Cl- and PO43- in the distilled water. The efficiency also declined in the medium of river and well water resources. Moreover, the Zeolite 4A/WO3/CuO catalyst maintained over 90 % of its performance even after five reuse cycles. Based on the kinetic study, the sono-photocatalytic process exhibited higher activation for the removal of MO (k: 0.1946 min−1 and t1/2: 3.561) and IC (k: 0.1433 min−1 and t1/2: 4.836) than other processes. The synergy values for the MO and IC degradation using the Zeolite 4A/WO3/CuO composite were determined to be 2.167 and 2.303, respectively. The impact of various scavengers demonstrated that in the degradation processes of the target dyes using the sono-photocatalytic process, different active species like OH•, e-, h+, and O2–• are involved. The purification of dye-laden water using the sono-photocatalytic process was not toxic for plant germination, microorganisms, and fish, highlighting the successful biocompatibility of the process for dye removal.

Biogas upgrading by intensified methanation (SESaR): Reaction plus water adsorption - desorption cycles with Ni-Fe/Al2O3 catalyst and LTA 5A zeolite

This work is conducted within the framework of the Power to Gas (PtG) technologies, focusing on the topic of “biogas upgrading”. The objective is to enhance the CH4 content of biogas streams by utilizing the CO2 present in these streams through the Sabatier reaction, thereby producing a renewable alternative to natural (fossil) gas. Referred to as “SESaR”(Sorption Enhanced Sabatier Reaction), this process employs a catalytic fixed-bed reactor, featuring selective water adsorption using LTA 5A zeolites, as an innovative approach to traditional methanation reactors. The catalyst used comprises Ni-Fe (7.5:2.5 wt/wt) as the active metallic phase supported on γ-Al2O3. Experimental work has been divided in two sets of trials. The first set focuses on the hydrogenation of CO2 as single reactant (H2 also supplied in the inlet with 4:1 = H2:CO2 molar ratio). The second set of experiments was carried out with a synthetic gas mixture representative of a sweetened biogas stream (molar ratio CH4:CO2 = 7:3). Maximum intensification behavior for CO2 conversion was found at 350 °C, also showing that CH4 presence in the inlet gas has negligible influence on the conversion of CO2. Selectivity to CO is minimized at temperatures exceeding 300 °C and remains constant after three consecutive cycles of methanation, water adsorption, and desorption. The Fe-Ni catalyst has demonstrated sustained performance throughout the experimental cycles, exhibiting no significant loss of activity.

Spherical Binderless 4A/5A Zeolite Assemblies: Synthesis, Characterization, and Adsorbent Applications.

Zeolite microspheres have been successfully applied in commercial-scale separators such as oxygen concentrators. However, further enhancement of their applications is hampered by the post-synthetic shaping process that formulates the zeolite powder into packing-sized spherical bodies with various binders leading to active site blockage and suboptimal performance. Herein, binderless zeolite microspheres with a tunable broad size range from 2 µm to 500 µm have been developed with high crystallinity, sphericity over 92%, monodispersity with a coefficient of variation (CV) less than 5%, and hierarchical pore architecture. Combining precursor impregnation and steam-assisted crystallization (SAC), mesoporous silica microspheres with a wide size range could be successfully transformed into zeolite. For preserved size and spherical morphology, a judicious selection of the synthesis conditions is crucial to ensure a pure phase, high crystallinity, and hierarchical architecture. For the sub-2-µm zeolite microsphere, low-temperature prolonged aging was important so as to suppress external zeolization that led to a large, single macroporous crystal. For the large 500 µm sphere, ultrasound pretreatment and vacuum impregnation were crucial and facilitated spatially uniform gel matrix dispersion and homogenous crystallization. The obtained zeolite 5A microspheres exhibited excellent air separation performance, while the 4A microspheres displayed ammonium removal capabilities. This work provides a general strategy to overcome the existing limitations in fabricating binder-free technical bodies of zeolites for various applications.

Adsorptive Drying of Liquid Mixtures Containing Formaldehyde, Methanol, Water, and Poly(oxymethylene) Dimethyl Ethers on Zeolite 3A

Adsorptive Drying of Liquid Mixtures Containing Formaldehyde, Methanol, Water, and Poly(oxymethylene) Dimethyl Ethers on Zeolite 3A