Zeolite Products Research Articles

Optimizing zeolitic hierarchical pore structure to boost the direct conversion of aromatics from syngas over the iron-based/zeolite bifunctional catalysts

The utilization of iron-based/ZSM-5 bifunctional catalysts for converting syngas to aromatics (STA) has garnered significant interest because of its cost-effectiveness. This study aims to elucidate the regulatory mechanism of zeolitic pore structure on the performance of the bifunctional catalyst in STA reaction. The relationship among the mesoporosity and mesoporous diameter of hierarchical ZSM-5 zeolite component, product distribution, and catalyst stability is investigated through a range of analyses techniques, including XRD, SEM, TG, Raman, N2-adsorption and desorption. The results demonstrate that as the mesoporosity of zeolite increased to 78.9%, the lifetime of the iron-based/ZSM-5 bifunctional catalyst extended beyond 96 h and maintained the aromatics selectivity over 40% at 2 MPa, 320 °C, and 3000 h−1. This outcome can be attributed to the role of high mesoporosity in restraining coke formation in zeolites. Moreover, the reduction in mesopore size from 11.1 to 5.8 nm results in an increased aromatics selectivity from 39.6% to 43.4%, and the fraction of light aromatics rose from 48.8% to 54.5%, indicating that small mesopore size can also expedite the production of aromatics, particularly light aromatics. It is thus concluded that the improvement of aromatics selectivity and stability of iron-based/ZSM-5 bifunctional catalysts in STA reaction can be achieved by increasing the mesoporosity and decreasing the mesopore size of the zeolite component.

Synthesis of zeolites using kaolin in concentrated sodium hydroxide-aluminate solutions

The synthesis of zeolites through the hydrothermal treatment of kaolin presents a cost-effective and sustainable method of production, however, the phases which remain stable in concentrated alkali solution with elevated NaAl(OH)4 are unclear. This study evaluated the equilibrium precipitation behaviour of zeolites from kaolin under a range of NaOH and NaAl(OH)4 concentrations at 523 K. The precipitates contained three types of low-silica (1:1 Si:Al) zeolites: zeolite JBW, two polymorphs of cancrinite (hydroxy- and aluminate-), and (hydroxy-)sodalite, as well as a novel sodium aluminate-intercalated nepheline-carnegieite phase at concentrated alkali-aluminate conditions. The construction of a phase diagram revealed distinct regions of stability and transition zones between phases through changing NaOH and NaAl(OH)4 concentration. The kaolin-to-zeolite phase transformation at early reaction time and Bayer pre-desilication conditions supported the phase transformation series: kaolinite → solution silicate species → aluminate-cancrinite → sodalite or cancrinite or a mixture. Substitution of caged aluminate [Al(OH)4−] for hydroxide [(OH)−] within zeolites was modelled, and revealed distinct deviation from ideal zeolite composition when starting molar Al2O3:SiO2 ≫ 1. As direct kaolin-to-zeolite technology emerges as a low-cost and low-energy alternative to conventional zeolite production, there will only be continued interest in its use in the future.

Cost-effectiveness analysis and cost-benefit analysis for X-type zeolite production from fly ash

Cost-effectiveness analysis and cost-benefit analysis for X-type zeolite production from fly ash

Pengolahan Air Sadah Menggunakan Zeolit Buatan Dari Batu Apung Lampung Dan Daun Kerai Payung

This research was conducted to determine the composition and crystal structure of the artificial zeolite produced, as well as the ability of artificial zeolite to reduce calcium and magnesium content in hard water. The zeolite was prepared using the hydrothermal method by mixing sodium silicate from Lampung pumice silica, sodium aluminate from aluminum can waste and charcoal from sunshade umbrellas. The artificial zeolite products were characterized using XRF, XRD, UV-Vis spectrophotometric and ICP-EOS. The results showed that the composition of the artificial zeolite was aluminum, silica, phosphorus, potassium, calcium, titanium, vanadium, chromium, manganum and ferum. The crystal structure of the optimum sample from the UV-Vis spectrophotometric characterization obtained the crystal structure of a natural zeolite type, namely Chabazite. And the artificial zeolite which was tested for adsorption on hard water could reduce the calcium content by 36.57% but could not reduce the magnesium content.

Desilication of high-silica Indian coal fly ash by alkali leaching with KOH and NaOH: A comparative study

ABSTRACT Indian coal fly ash generally comprises 50–60% Si O 2 , and 25–35% A l 2 O 3 can potentially replace bauxite as an aluminum resource. Aluminum recovery from coal fly ash is highly dependent on removing amorphous silica, activating the inactive mullite phase, and increasing the Al / Si ratio. This work thoroughly investigated and compared the alkali-desilication operation by two widely used alkalis, KOH and NaOH , based on four operational parameters: liquid-to-solid ratio, KOH or NaOH concentration, leaching time and temperature. Using SEM, EDX, and XRD, the morphology and phase of fly ash and solid byproducts were analyzed. NaOH was more effective than KOH in Si O 2 dissolution at all operational parameters. A 20 wt% concentration, 5:1 liquid-to-solid ratio, 2hrs leaching time, and 100°C temperature were the optimum removal conditions for silica from fly ash using NaOH . With KOH , the ideal desilication conditions were obtained at 28 wt% concentration, 3hrs leaching time, and 150°C temperature. The highest Al / Si ratios were obtained under the same optimal desilication conditions. Using KOH and NaOH , the Al / Si ratio was enhanced from 0.58 to 1.26 and 1.45, respectively. The main zeolitic products obtained were Hydroxysodalite in NaOH -treated fly ash and Linde F zeolite and Kalsilite in KOH -treated fly ash.

Solarization of the zeolite production: Calcination of kaolin as proof-of-concept

The current production of zeolites from natural sources requires high temperatures to achieve a phase change in the feedstock materials. Thermal processes such as calcination are energy-consuming and industry relies on fossil fuels to generate the necessary heat, which is neither sustainable nor environmental. This study presents for the first time the treatment of aluminosilicate clay kaolin in a solar reactor to produce metakaolins that are eligible as precursors for zeolite synthesis. Kaolin was loaded in a rotary kiln and a solar simulator was used for calcination at temperatures of 700–1000 °C for 2 h. After the solar calcination process, solar-produced metakaolins were used to synthesize zeolite 4 A and zeolite 13X by hydrothermal route. The kaolin, metakaolin, and product samples obtained were analyzed by XRD, XRF, FTIR, and FE-SEM. Results show that solar-calcined kaolin was as good and efficient as the conventionally calcined one in terms of supplying the metakaolin for zeolite synthesis. Often disregarded by researchers, high-temperature calcination of the kaolin was proved to be an alternative way for the synthesis of zeolite 13X without using an extra silica source, which was achieved for the first time. The overall results suggest that solar calcination is a good alternative to mass produce meta forms of the minerals to be used in the synthesis of value-added products such as zeolites.

PREDICTION OF EMERGENCY SITUATIONS IN THE PRODUCTION OF ZEOLITE TYPE A

This article examines the problem of an emergency situation at work. The main causes of accidents at zeolite production facilities are described. The aim of the work is to improve the efficiency of the industrial safety and labor protection management system at the facility by analyzing incidents, identifying causes and systemic violations, finding solutions to prevent and eliminate such situations. In accordance with the goal, the following tasks were set: analysis of accidents, incidents and incidents at the considered and similar facilities, systematization and detailed analysis of technical and organizational causes and systemic violations leading to the occurrence of accidents. Based on the analysis, make recommendations on improving the effectiveness of measures to ensure industrial safety and labor protection at the facility.After analyzing a number of emergencies, it is possible to identify the causes and systemic violations. All the reasons can be divided into two groups: organizational and technical. As a result of a systematic analysis of the causes of emergencies, the primary sources of its occurrence were identified for each group of causes, and areas of activity were proposed, as a result of which, in the case of their effective application, the number of accidents significantly decreases, and the indicators of safe work at facilities increase. The main conclusions of the work: 1. it is necessary to modernize production with the involvement of financing for the renewal of outdated equipment; 2. pay special attention to the selection of qualified personnel, their training and motivation; 3. effective and high-quality management of human resources, together with the involvement of funding sources to solve technical problems, will, in our opinion, ensure an acceptable level of security. The practical significance of the work done lies in the implementation of the proposed measures to improve the efficiency of industrial safety and labor protection management.

Continuous flow hydrothermal synthesis of zeolite LTA in intensified reactor. Experimental and multiphysics CFD modeling approach

Zeolites are conventionally synthesized in batch-wise hydrothermal processes that usually take several hours or days to complete. In current research work, continuous flow process is developed on pilot scale for the hydrothermal synthesis of zeolite LTA. The pilot reactor was able to produce highly crystalline zeolite nanoparticles without any clogging, which often encounters for particle flow in tubular reactors. Steady-state zeolite production rates of 55–80 g⋅h −1 (dry basis) were achieved with a residence time below 10 min, with corresponding space time yields (STY) between ca. 700 and 1100 g⋅L −1⋅h −1. A couple CFD model with a population balance model was developed to investigate the continuous flow hydrothermal process. The average particle size obtained from the model was in good agreement with the experimental data. The model was further applied to study the effects of critical parameters, such as temperature and flow rate, to highlight potential process optimization directions.

Eco-friendly zeolites for innovative purification of water from cationic dye and heavy metal ions.

Along with industrial development, coal consumption and the amount of waste fly ash increase, negatively impacting the environment. Fly ash contains silicon and aluminum oxides, and could serve as a substrate for the synthesis of zeolite. The novelty of this study was to assign a potential of fly ashes from lignite combustion in three energy blocks operating on circulating fluidized bed boilers to convert them into zeolites. The X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy; pore volume, size and specific surface area tests; thermal analysis; leaching test; and radioisotope activity analysis were applied to characterize the materials. Zeolites were synthesized using hydrothermal and fusion methods modified in the molar concentration of NaOH, the ratio of NaOH to raw material, drying and heating temperatures, and treatment time. Both, hydrothermal and fusion synthesis were found to result in the efficient formation of the zeolite Linde Type A, gismondine, and sodalite; with the largest specific surface area of zeolite developed after fusion synthesis (132 m2 g−1). The zeolite had surpassingly high efficiency of adsorption of cationic impurities from post-production wastewater, ranging from 85% to 97% and from 89% to 100%, when tested with methylene blue and lead ions, respectively. The costs of zeolite production were estimated to range from 3.82 to 6.36 $ per 1 kg, thus reducing the price of commercial zeolite by up to 99.5%. The new engineering method of zeolite is an attractive alternative to the storage of hazardous byproducts from coal-fired power plants. Eco-zeolite is also a technological innovation in the cleaning of post-production wastewater from harmful impurities, while water reuse in a closed circuit. Our studies provide tools for novel and integrated environmental management in line with the 'Cleaner Production' goal to reduce the production of waste, while improving use efficiency of energy, resources, and water.

Synthesis and Sorption Properties of Microsphere Zeolite Materials Based on Coal Fly Ash Cenospheres with Respect to Cs+ and Sr2+

The effect of the hydrothermal synthesis conditions (temperature, duration, mixing), composition, and presynthetic processing of narrow fractions of cenospheres of fly ash, which act as a template and source of Si and Al, on the production of microspherical zeolite materials of the given structural type in the Na2O–H2O–(SiO2–Al2O3)glass of two molar compositions is studied. The synthesis products are characterized by XRD, SEM-EDS, and low-temperature nitrogen adsorption, and their sorption properties in relation to Cs+ and Sr2+ are studied. The factors contributing to the predominant formation of NaX zeolite of the faujasite structural type are revealed. It is established that zeolite products based on cenospheres with a glass phase content of about 95 wt % demonstrate the highest sorption parameters, including the maximum capacity for Cs+ and Sr2+ of up to 250 and 180 mg/g, distribution coefficient of about 104 and 106 mL/g, and degree of extraction of 99.1 and 99.9%, respectively.

Sapo-34 Obtained from Amazonian Flint Kaolin: Influence of Impurities of “Oxidized Fe/Ti” in Synthesis and Its Application in the Removal of Cationic Dye from Water

Non-processed kaolin (flint kaolin) from a mine located in the Capim area (Amazon region, northern Brazil), usually considered as waste, was selected as a source of silicon and aluminum in the synthesis of SAPO-34. This is a molecular sieve and cationic exchanger chosen for tests focusing on the removal of methylene blue in aqueous solutions, which is a cationic dye widely used by textile industries in Brazil. The results revealed that the SAPO-34 has been successfully synthesized with typical cubic morphology, good crystallinity (>90%), and thermal stability (~998 °C). Although the oxidized Fe/Ti impurities contained in the flint kaolin affect the degree of crystallinity of the zeolitic product, its adsorptive properties are not significantly affected, which demonstrates the excellent adsorption results (pH = 11; % removal > 90%). It proved to be an adsorbent with considerable adsorption capacity (9.83 mg·g−1). The pH test confirmed the acidic surface characteristics (pH solution 2–4; ↓ removal), and the kinetic model that best fitted the experimental data was pseudo-second-order, with R2 = 0.998 (kinetics controlled by chemisorption).

Research Progress on CO2 Capture, Utilization, and Storage of Fly Ash

The research progress of different technologies of fly ash for CO2 capture, utilization, and storage at home and abroad was summarized, and the research opportunities were discussed. Fly ash could mineralize, capture, and store CO2 through direct dry, semi dry, wet, and indirect methods, reducing the leaching of heavy metals in fly ash while mineralizing CO2. The mineralized fly ash was more suitable for making concrete additives because it could effectively reduce the content of free CaO and MgO. Fly ash could also be made into activated carbon, zeolite, porous silica, and other products for physical adsorption and capture of CO2. The type of products depended mainly on the composition and physical/chemical properties of fly ash. In terms of CO2 utilization, fly ash could not only expand the utilization of building materials but also be made as catalysts or catalyst carriers required for various chemical processes of CO2 and new materials such as pseudo boehmite. The proposal of "double carbon" in China and the physical/chemical characteristics of fly ash from coal-fired power plants provide a new method for comprehensive utilization of fly ash.

High-throughput phase elucidation of polycrystalline materials using serial rotation electron diffraction

Rapid phase elucidation of polycrystalline materials is essential for developing new materials of chemical, pharmaceutical and industrial interest. Yet, the size and quantity of many crystalline phases are too small for routine X-ray diffraction analysis. This has become a workflow bottleneck in materials development, especially in high-throughput synthesis screening. Here we demonstrate the application of serial rotation electron diffraction (SerialRED) for high-throughput phase identification of complex polycrystalline zeolite products. The products were prepared from a combination of multiple framework T atoms ([Si,Ge,Al] or [Si,Ge,B]) and a simple organic structure-directing agent. We show that using SerialRED, five zeolite phases can be identified from a highly complex mixture. This includes phases with ultra-low contents undetectable using X-ray diffraction and phases with identical crystal morphology and similar unit cell parameters. By automatically and rapidly examining hundreds of crystals, SerialRED enables high-throughput phase analysis and allows the exploration of complex synthesis systems. It provides new opportunities for rapid development of polycrystalline materials.

In Situ Imaging of Faujasite Surface Growth Reveals Unique Pathways of Zeolite Crystallization.

Zeolite crystallization occurs by complex processes involving a variety of possible mechanisms. The sol gel media used to prepare zeolites leads to heterogeneous mixtures of solution and solid states with diverse solute species. At later stages of zeolite synthesis when growth occurs predominantly from solution, classical two-dimensional nucleation and spreading of layers on crystal surfaces via the addition of soluble species is the dominant pathway. At earlier stages, these processes occur in parallel with nonclassical pathways involving crystallization by particle attachment (CPA). The relative roles of solution- and solid-state species in zeolite crystallization have been a subject of debate. Here, we investigate the growth mechanism of a commercially relevant zeolite, faujasite (FAU). In situ atomic force microscopy (AFM) measurements reveal that supernatant solutions extracted from a conventional FAU synthesis at various times do not result in growth, indicating that FAU growth predominantly occurs from the solid state through a disorder-to-order transition of amorphous precursors. Elemental analysis shows that supernatant solutions are significantly more siliceous than both the original growth mixture and the FAU zeolite product; however, in situ AFM studies using a dilute clear solution with a lower Si/Al ratio revealed three-dimensional growth of surfaces that is distinct from layer-by-layer and CPA pathways. This unique mechanism of growth differs from those observed in studies of other zeolites. Given that relatively few zeolite frameworks have been the subject of mechanistic investigation by in situ techniques, these observations of FAU crystallization raise the question whether its growth pathway is characteristic of other zeolite structures.

High-throughput synthesis of AlPO and SAPO zeolites by ink jet printing.

Ink jet printing is for the first time introduced into the synthesis of aluminophosphate (AlPO) and silicoaluminophosphate (SAPO) zeolite. As a high-throughput technique, 256 zeolite precursors with multiple formulations could be obtained within 2 h, while the product phase was regulated relative to the variant compositions.

Fusion-Assisted Hydrothermal Synthesis and Post-Synthesis Modification of Mesoporous Hydroxy Sodalite Zeolite Prepared from Waste Coal Fly Ash for Biodiesel Production

Increases in biodiesel prices remains a challenge, mainly due to the high cost of conventional oil feedstocks used during biodiesel production and the challenges associated with using homogeneous catalysts in the process. This study investigated the conversion of waste-derived black soldier fly (BSF) maggot oil feedstock over hydroxy sodalite (HS) zeolite synthesized from waste coal fly ash (CFA) in biodiesel production. The zeolite product prepared after fusion of CFA followed by hydrothermal synthesis (F-HS) resulted in a highly crystalline, mesoporous F-HS zeolite with a considerable surface area of 45 m2/g. The impact of post-synthesis modification of the parent HS catalyst (F-HS) by ion exchange with an alkali source (KOH) on its performance in biodiesel production was investigated. The parent F-HS zeolite catalyst resulted in a high biodiesel yield of 84.10%, with a good quality of 65% fatty acid methyl ester (FAME) content and fuel characteristics compliant with standard biodiesel specifications. After ion exchange, the modified HS zeolite catalyst (K/F-HS) decreased in crystallinity, mesoporosity and total surface area. The K/F-HS catalyst resulted in sub-standard biodiesel of 51.50% FAME content. Hence, contrary to various studies, the ion exchange modified zeolite was unfavorable as a catalyst for biodiesel production. Interestingly, the F-HS zeolite derived from waste CFA showed a favorable performance as a heterogeneous catalyst compared to the conventional sodium hydroxide (NaOH) homogeneous catalyst. The zeolite catalyst resulted in a more profitable process using BSF maggot oil and was economically comparable with NaOH for every kilogram of biodiesel produced. Furthermore, this study showed the potential to address the overall biodiesel production cost challenge via the development of waste-derived catalysts and BSF maggot oil as low-cost feedstock alternatives.

Zeolite NaP1 synthesized from municipal solid waste incineration fly ash for photocatalytic degradation of methylene blue

The disposal of hazardous municipal solid waste incineration (MSWI) fly ash is a challenge nowadays. Recently, the re-utilization of MSWI fly ash by converting it to useful zeolite-containing materials has attracted attention. However, the zeolitic products fabricated from MSWI fly ash are usually of low quality and rarely reported to be applied for photocatalysis. In this study, valuable zeolites (e.g., NaP1) are synthesized from MSWI fly ash via a modified microwave-assisted hydrothermal method. The key parameters for the hydrothermal method including temperature, duration, the amount of additive, and water volume, are investigated and optimized. Specifically, increasing the hydrothermal temperature can promote the synthesis of zeolitic materials; a relatively long hydrothermal duration is essential to accomplish the assembly of zeolites; the addition of Na2SiO3 can increase the precursor for the fabrication of zeolites; the water volume makes little influence on the crystal style of products. Eventually, the hydrothermal condition of 180 °C, 1 h, 0.5 g Na2SiO3, and 10 mL water is suggested based on the energy consumption and the quality of zeolites. The product containing zeolite NaP1 from such a condition is further applied to degrade methylene blue by photocatalysis. The removal rate has reached 96% within 12 h, which dramatically surpasses that of the raw fly ash (38%). Such excellent photocatalytic performance is attributed to the 10-fold increased surface area (24.864 m2 g−1) and active metal elements embedding in the zeolite structures.

Process optimisation of low silica zeolite synthesis from spodumene leachate residue

Lithium extraction from hard rock sources, such as spodumene, generates an aluminosilicate waste that can be converted into zeolite materials. Increased lithium demand in recent years highlights a growing need to develop a residue mitigation strategy. Zeolite synthesis from aluminosilicate waste is more complex than conventional synthetic zeolite production routes and typically involves an activation step, such as alkali fusion. In this context, a key challenge to increase product quality involved understanding the influence of factors such as aluminium supplement addition and alkali fusion processing options. Zeolite X crystalline content and particle morphology was compared in relation to various reaction gel compositions. Zeolite X was produced from alkali-fused SLR which was found to contain 60 wt% crystalline zeolite X after adjusting key synthesis parameters to 2.0 Si:Al ratio, 1.4 Na2O:SiO2 ratio, 30 H2O:Na2O. The product was highly agglomerated (D[4,3] = 51.1 µm) with small crystal sizes of< 2 µm. Holding this gel composition constant and introducing the aluminium supplementation during gel aging, the average particle agglomeration was reduced (D[4,3] = 14.1 µm). Further processing of the fused SLR qualitatively reduced agglomeration and increased zeolite X crystal size, with little impact on the crystalline zeolite X content; the latter strategy produced a zeolite X material with similar morphological characteristics to a commercially available analogue. This work demonstrated that controlling the processing and additions of activated aluminosilicate was a key consideration in terms of controlling zeolite crystal morphology.

Low-cost zeolitic carriers for delivery of hydroxychloroquine immunomodulatory agent with antiviral activity

The coronavirus pandemic prompted scientists to look for active pharmaceutical ingredients that could be effective in treating COVID-19. One of them was hydroxychloroquine, an antimalarial and immunomodulatory agent exhibiting antiviral activity. The anchoring of this drug on porous carriers enables control of its delivery to a specific place in the body, and thus increases bioavailability. In this work, we developed low-cost zeolitic platforms for hydroxychloroquine. The waste solution generated during zeolite production from fly ashes was used in the synthesis of Na-A and Na-X carriers at laboratory and technical scale. The materials were characterized by high purity and single mineral phase composition. The surface charge of zeolites varied from negative at pH 5.8, and 7.2, to positive at pH 1.2. All samples indicated good sorption ability towards hydroxychloroquine. The mechanism of drug adsorption was based on electrostatic interactions and followed the Freundlich model. Zeolitic carriers modified the hydroxychloroquine release profiles at conditions mimicking the pH of body fluids. The mode of drug liberation was affected by particle size distributions, morphological forms, and chemical compositions of zeolites. The most hydroxychloroquine controlled release at pH 5.8 for the Na-X material was noted, which indicates that it can enhance the drug therapeutic efficacy.

Use of Multiscale Data-Driven Surrogate Models for Flowsheet Simulation of an Industrial Zeolite Production Process

The production of catalysts such as zeolites is a complex multiscale and multi-step process. Various material properties, such as particle size or moisture content, as well as operating parameters—e.g., temperature or amount and composition of input material flows—significantly affect the outcome of each process step, and hence determine the properties of the final product. Therefore, the design and optimization of such processes is a complex task, which can be greatly facilitated with the help of numerical simulations. This contribution presents a modeling framework for the dynamic flowsheet simulation of a zeolite production sequence consisting of four stages: precipitation in a batch reactor; concentration and washing in a block of centrifuges; formation of droplets and drying in a spray dryer; and burning organic residues in a chain of rotary kilns. Various techniques and methods were used to develop the applied models. For the synthesis in the reactor, a multistage strategy was used, comprising discrete element method simulations, data-driven surrogate modeling, and population balance modeling. The concentration and washing stage consisted of several multicompartment decanter centrifuges alternating with water mixers. The drying is described by a co–current spray dryer model developed by applying a two-dimensional population balance approach. For the rotary kilns, a multi-compartment model was used, which describes the gas–solid reaction in the counter–current solids and gas flows.