Zeolite 4A Research Articles

Adsorption of Pollutants from Colored Wastewaters after Natural Wool Dyeing.

The presented study assesses the efficiency of selected adsorbents, zeolite 4A in two particle sizes and pelletized activated carbon (AC), for the potential removal of color, chemical oxygen demand (COD), total organic carbon (TOC) and metals from wastewaters after natural wool dyeing. Firstly, the natural coloring compounds were extracted from dried common walnut (Juglans regia) leaves and used further for exhaustion dyeing of wool fibers, together with three different metallic salts in two concentrations (meta-mordanting). Effluents with higher mordant concentration were additionally treated according to a shake-flask adsorption experiment. The obtained results revealed efficient removal of exceeded metallic ions by zeolite (up to 94.7%), on account of their superior ion exchange capability as compared to AC. The zeolites also reduced turbidity and electrical conductivity significantly. On the other hand, AC was more efficient for the reduction in organic pollution, COD up to 96% and TOC up to 95%, due to its higher specific surface area and total pore volume, and, thus, higher potential for adsorption of different compounds in comparison to 4A. All three proposed adsorbents lowered wastewaters’ coloration remarkably, up to 78% (AC) and up to 71% (4A), depending on the type of effluent/mordant and inspected wavelength; although, the spectral absorbance coefficient (SAC) values remained highly above the limit values for discharge of wastewaters into watercourses.

Mixture optimization of synthesized zeolites 4A and 13X for solar adsorption refrigeration application

Abstract In a way to overcome challenges with global warming, the use of fossil fuels in producing environmentally friendly energy towards reducing the ozone layer depletion and greenhouse gas emissions by participating countries is of interest. The adsorption refrigeration system has the advantages of a long lifespan and its environmental friendliness; however, its major disadvantage is the low coefficient of performance, which is a function of adsorbent–adsorbate, with zeolite–water as the most common adsorbent–adsorbate working pair. Zeolites 4A and 13X are the most used zeolite classes due to their higher selectivity for separating mixtures of CO2/N2 and CO2/CH4/N2 and their high-water adsorption capability, respectively. In this study, for the first time, the synthesis of zeolites 4A and 13X from natural sources (Kankara kaolin) and the mixture optimization for solar adsorption refrigeration application were considered. Raw Kankara kaolin, beneficiated Kankara kaolin, calcined Kankara kaolin and synthesized zeolites 4A and 13X were characterized using X-ray fluorescence, while the synthesized zeolites 4A and 13X were characterized using X-ray diffraction. Using the mixture simplex lattice design of experiment, mixtures of zeolites 4A and 13X were developed and characterized using Brunauer, Emmett and Teller analysis to obtain their pore size, specific surface area and pore volume. The statistical analysis produced the mathematical models of the response that were significant for pore size and specific surface area. The analysis proposed an optimal solution of 75 wt% zeolite 4A and 25 wt% zeolite 13X, which gave a desirability of 0.944.

Difluoromethane (HFC-32) and Pentafluoroethane (HFC-125) Sorption on Linde Type A (LTA) Zeolites for the Separation of Azeotropic Hydrofluorocarbon Refrigerant Mixtures.

Worldwide use of hydrofluorocarbons (HFCs) is currently being regulated and phased out because of high global warming potentials (GWPs). Separation techniques for recycling refrigerants are needed so that HFCs can be dealt with responsibly. Many HFCs currently in use are azeotropic or near-azeotropic refrigerant blends and must be separated so that the components can be recycled and repurposed effectively. One such refrigerant is R-410A, which is a near-azeotropic 50/50 wt % mixture of pentafluoroethane (HFC-125) and difluoromethane (HFC-32). This study examined the use of the LTA zeolites for separating HFC-32 from HFC-125. Pure gas isotherms were measured using a XEMIS gravimetric microbalance with zeolites 3A, 4A, and 5A. Reversible sorption was observed for HFC-32 with zeolites 4A and 5A, whereas irreversible sorption was observed for HFC-125 with zeolite 5A. Negligible sorption was observed for HFC-125 with zeolites 3A and 4A, and although sorption of HFC-32 with zeolite 3A was observed, the process was slow, making the sorbent not commercially viable. The enthalpy of adsorption was predicted using the vapor adsorption equilibrium (VAE) analogue of the Clausius-Clapeyron equation and measured using a calorimeter for HFC-125 and HFC-32 with zeolite 5A and for HFC-32 with zeolite 4A. Molecular-level interactions between the LTA zeolites and HFCs were discussed and used to interpret pure gas isotherms and enthalpy of adsorption results. Overall, zeolites 4A and 5A were found to be good candidates for kinetically and thermodynamically separating R-410A, respectively.

Improving the Energy Yield of Plasma-Based Ammonia Synthesis with In Situ Adsorption

Plasma-based ammonia synthesis is studied as an option for electrifying the chemical industry. However, the energy efficiency of plasma-based ammonia synthesis is severely limited by ammonia decomposition in the plasma phase. We show that the use of zeolite 4A as an adsorbent for in situ ammonia removal from the plasma phase suppresses product decomposition, thereby increasing the ammonia yield. It is found that the ammonia yield for plasma-chemical ammonia synthesis with in situ ammonia removal is improved by a factor of 2 compared to steady-state plasma-chemical ammonia synthesis. Plasma-induced surface heating limits the effective ammonia adsorption capacity of the zeolite, decreasing the adsorption capacity. In situ product removal is of interest for plasma chemistry and plasma catalysis, in general, as the product decomposition in the plasma is a general phenomenon limiting the product yield.

Comparative study on pressure swing adsorption system for industrial hydrogen and fuel cell hydrogen

In order to improve the design of PSA system for fuel cell hydrogen production, a non-isothermal model of eight-bed PSA hydrogen process with five-component (H 2 /N 2 /CH 4 /CO/CO 2 = 74.59%/0.01%/4.2%/2.5%/18.7% (vol)) four-stage pressure equalization was developed in this article. The model adopts a composite adsorption bed of activated carbon and zeolite 5A. In this article, pressure variation, temperature field and separation performance are stimulated, and also effect of providing purge (PP) differential pressure and the ratio of activated carbon to zeolite 5A on separation performance in the process of producing industrial hydrogen (CO content in hydrogen is 10 µl·L −1 ) and fuel cell hydrogen (CO content is 0.2 µl·L −1 ) are compared. The results show that Run 3, when the CO content in hydrogen is 10 µl·L −1 , the hydrogen recovery is 89.8%, and the average flow rate of feed gas is 0.529 mol·s −1 ; When the CO content in hydrogen is 0.2 µl·L −1 , the hydrogen recovery is 85.2%, and the average flow rate of feed gas is 0.43 mol·s −1 . With the increase of PP differential pressure, hydrogen recovery first increases and then decreases, reaching the maximum when PP differential pressure is 0.263 MPa; With the decrease of the ratio of activated carbon to zeolite 5A, the hydrogen recovery increases gradually. When the CO content in hydrogen is 0.2 µl·L −1 the hydrogen recovery increases more obviously, from 83.96% to 86.37%, until the ratio of activated carbon to zeolite 5A decreases to 1. At the end of PP step, no large amount of CO 2 in gas or solid phase enters the zeolite 5A adsorption bed, while when the CO content in hydrogen is 10 µl·L −1 , and the ratio of carbon to zeolite 5A is less than 1.4, more CO 2 will enter the zeolite 5A bed.

Nanoarchitectonics of AgBr/4A Zeolite Composites with Enhanced Photocatalytic Properties Under Visible Light

AgBr/zeolite photocatalysts with different mass ratios were synthesized by depositing AgBr on the surface of 4A zeolite via the one-step precipitation method. AgBr/zeolite with mass ratios of 1:1 exhibited the highest photocatalytic activity, resulting in the complete degradation of the methyl orange (MO) dye under visible-light irradiation for 30[Formula: see text]min. The photocatalysts were characterized by N2 adsorption–desorption, scanning electron microscopy (SEM), X-ray diffraction (XRD), UV–Vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) spectroscopy. The AgBr particles around 4A zeolite were smaller than pure AgBr. The specific surface area of 1:1 AgBr/zeolite was much larger than that of pure AgBr, which indicates that 1:1 AgBr/zeolite possessed more active sites. The photocatalytic stability of 1:1 AgBr/zeolite was investigated, and MO degradation rate of 90.4% was achieved after five cycling runs. The trapping experiments showed that hydroxyl radical ([Formula: see text]OH), superoxide radical ([Formula: see text]O[Formula: see text]), and hole (h[Formula: see text]) were the reactive species responsible for removing MO, and h[Formula: see text] played a key role in MO removal. A possible reaction mechanism in AgBr/zeolite photocatalytic system for MO degradation was proposed.

Novel prosperous computational estimations for greenhouse gas adsorptive control by zeolites using machine learning methods

To predict CO2 adsorptive capture, as a vital environmental issue, using different zeolites including 5A, 13X, T-Type, SSZ-13, and SAPO-34, different models have been developed by implementing artificial intelligence algorithms. Hybrid adaptive neuro-fuzzy inference system (Hybrid-ANFIS), particle swarm optimization-adaptive neuro-fuzzy inference system (PSO-ANFIS) and the least-squares support vector machine (LSSVM) modeling optimized with the coupled simulated annealing (CSA) optimization have been employed for the models. The developed models, validated by utilizing various graphical and statistical methods exhibited that the Hybrid-ANFIS model estimations for the gas adsorption on 5A, T-Type, SSZ-13, and SAPO-34 zeolites with average absolute relative deviation (AARD) % of 8.21, 1.92, 4.99 and 2.26, and PSO ANFIS model estimations for the gas adsorption on zeolite 13X with an AARD of 4.85% were in good agreement with corresponding experimental data. It could be deduced that the proposed models were more prosperous and efficient in favor of the design and analysis of adsorption processes than previous ones.

A fast methodology to rank adsorbents for CO2 capture with temperature swing adsorption

A new methodology for evaluating different commercial adsorbents for CO2 capture using temperature swing adsorption (TSA) has been developed. The screening method is based on thermogravimetric analysis (TGA) combined with differential scanning calorimetry (DSC) to study the cyclic behavior of adsorbents paying attention on CO2 production and desorption energy. CO2 production and desorption energy were determined for commercial zeolites using a simulated flue gas (15% CO2 / 85% N2 v/v). Binderless zeolites had better CO2 production and lower desorption energy on TSA cycles than their analog binder-based zeolites. The zeolite with the highest CO2 production (0.077 kgCO2/kgads٠h) and the lowest desorption energy (0.56 kWh/kgCO2) was the 13XBL binderless zeolite. On the other side, the 5A zeolites (binder and binderless) had the lowest CO2 production (0.046–0.054 kgCO2/kgads٠h) and the highest desorption energy (0.78–0.93 kWh/kgCO2) among zeolites. Results obtained demonstrated that the proposed methodology is a good basis for the fast selection of the best adsorbent and for the selection of the adsorption and desorption cycling temperatures in CO2 capture processes through TSA.

Oxygen vacancies promoted heterogeneous catalytic ozonation of atrazine by defective 4A zeolite

The ozone activation reaction is becoming more popular with the treatment of organic pollutants, while the key to improving the efficiency heavily lies in the selection of active catalysts. In this study, we demonstrate that synthetic 4A zeolite with a high surface oxygen vacancy density and acidity exhibits excellent activity toward the ozonation process, where the removal rates of atrazine (ATZ) reached 87.5% at 6 min, and the removal rates of Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC) reached 66.7% and 35.8% at 15 min, respectively. Compared with commercial 4A zeolite and synthetic 4A zeolite with acid treatment, the ozonation activities of 4A zeolites positively correlate with the surface acidity. Mechanistic investigations have identified that hydroxyl radicals are the main reactive oxygen species, and thus, the degradation pathway of ATZ is provided. Moreover, the influences of catalyst dosage, reaction temperature, pH and cycling stability on ozonation performance are systematically evaluated.

Adsorption behavior of iodide ion by silver-doped zeolite 4A in LiCl-KCl molten salt

In this study, the porous material zeolite with cage-like structure was modified to prepare silver-doped zeolite 4A (abbreviated as Ag@4A) using ion exchange method, with a silver loading of 34.2 wt% and a specific surface area of ​​23.62 m2/g. The adsorption performance of Ag@4A for anionic iodine in LiCl-KCl molten salt system was investigated through static adsorption experiments. The modified adsorbents and experimental samples were analyzed by XRD, SEM, ICP-OES and other methods. At 550 °C, compared with the unmodified zeolite 4A, adsorption capacity of 34 mg/g of iodine, the maximum adsorption capacity of Ag@4A for iodine ions was up to 160 mg/g. When Cs+ existed in the system, the maximum adsorption capacity of Ag@4A for iodide ions was about 64 mg/g; when Cs+ and Sr2+ coexisted, the maximum adsorption capacity of Ag@4A for iodide ions decreased to 103 mg/g. Ag@4A also showed a certain adsorption capacity for Cs+ and Sr2+. These results indicated that the Ag@4A has potential application for the removal of iodide ions and other cations in chloride molten salt.

Equilibrium and Kinetic Adsorption of Hydrogen Fluoride onto Zeolite 3A

Equilibrium and kinetic adsorption behaviours of hydrogen fluoride (HF) onto zeolite 3A were investigated under different temperatures (298–338 K) and pressures (0.15–1.1 bar). The HF adsorption isotherms on zeolite 3A were well described by the Dubinin–Astakhov (DA) model. The isosteric heat of HF adsorption was calculated based on the DA model and Clausius–Clapeyron equation, and different kinetic models were used to analyze the HF adsorption kinetic. The results showed HF adsorption isotherms are type I of the IUPAC classification. The maximum adsorption capacities by the DA model are 0.443–0.5631 mg/g. The [Formula: see text] values decrease with increasing surface loading indicating the surface energy heterogeneity of zeolite 3A. The HF adsorption kinetics on zeolite 3A follows simple first-order kinetics. The calculated film diffusion parameter [Formula: see text] values show nonlinear characteristics with time. The order of magnitude of interparticle HF diffusion coefficient [Formula: see text] is 10−9 m2/s. The higher pressure and temperature are in favour of HF diffusion. The intraparticle diffusion curves for HF adsorption on zeolite 3A show quart-linear characteristics, indicating the presence of four consecutive HF adsorption steps including film diffusion, interparticle diffusion, intraparticle diffusion, and surface adsorption. The intraparticle diffusion is a rate-controlling stage.

Improved accessibility of Na-LTA zeolite catalytic sites for the Knoevenagel condensation reaction

The use of zeolites in basic catalysis is limited when large molecules are involved, such as in the manufacture of fine chemicals, due to difficulty in accessing the micropores of the catalyst. A solution to this problem is to synthesize zeolites containing mesopores that improve the accessibility of the active sites. This work investigates the synthesis of zeolites 4A according to a bottom-up method employing the organosilane surfactant [3-(trimethoxysilyl) propyl] octadecyldimethylammonium chloride (TPOAC), at different concentrations in the synthesis mixture (TPOAC/Al2O3 = 0–0.09), to produce mesopores. The zeolites were evaluated in the Knoevenagel condensation reaction, which is strongly influenced by the accessibility of the catalytic sites, due to the large sizes of the molecules involved. Zeolites 4A with mesopores, showing higher external surface areas, were formed in the presence of TPOAC at the different concentrations tested. Higher conversions were achieved using the zeolites with mesopores, compared to conventional zeolite 4A, due to improved access of the reactant molecules to the catalytic sites. In addition, the reaction catalyzed by the zeolite with mesopores had lower activation energy, compared to use of the conventional zeolite 4A.

Water Removal from an Ethanol-Water Mixture at Azeotropic Condition by Adsorption Technique

The separation of ethanol-water mixture is employed in the present work to produce pure ethanol, the present investigation on the separation of water from the ethanol to achieve pure ethanol by adsorption process. The different parameters like quantity of adsorbent, flow rate of feed mixture, and different adsorbents which are zeolite 3A, zeolite 4A, and silica gel are selected to study purification of ethanol by adsorption. The effect of process parameter for purification is also recorded and studied to evaluate the performance of adsorption equipment and adsorbent. The experiments are conducted at 30°C. The feed mixture is 95.6% (v/v) concentration of ethanol and 4.4% (v/v) of water. The designed adsorption column is suitable for purification of ethanol. The highest ethanol concentration 99.9443% obtained at 20 ml/min flow rate of feed mixture using 50 g of zeolite.

Analysis of nano material based Zeolite catalytic converter and urea injection in single cylinder engine fuelled with diesel and plastic pyrolysis oil

The consistent state movement of Zeolite 4A and 5A with urea infusion framework has been researched tentatively for Nitrogen oxide, Hydrocarbon, Carbon monoxide & smoke with exceptionally oxidizing catalysts, for ordinary lean consumed motor exhaust. The ZSM powder is added to 8 % of bentonite earth, 5 % of carboxymethyl cellulose and 34 % of refined water & blended continually to shape like a trim sand. Carboxymethyl cellulose is used which has good binding property. The mold is placed in the oven at 150 °C with an increment of 75 °C each 45 mins until the temperature arrived at 450 °C then it has been saved for 60 mins for calcination. Most of the developing countries depend of crude oil because diesel is used as a main transportation fuel. Finding an alternative fuel to replace diesel is an important need, plastic pyrolysis oil is suitable for compression ignition engines. The property of plastic oil is similar to diesel fuel, Emission test has been performed with a combination of 50 % Diesel + 50 % Plastic Oil in direct injection engines and compared with Diesel. Our objective is to investigate the possibility of reducing NOx emissions in tail pipe. Reduction of oxides of nitrogen (NOx) was carried out by injecting urea in the tail pipe of a diesel engine. Urea has been infusion to accomplish NOx decrease with Zeolite impetus powered with Diesel fuel and Diesel + Plastic Pyrolysis Oil.

Degradation of Desiccants in Temperature Swing Adsorption Processes: The Temperature Dependent Degradation of Zeolites 4a, 13x and Silica Gels

Degradation of Desiccants in Temperature Swing Adsorption Processes: The Temperature Dependent Degradation of Zeolites 4a, 13x and Silica Gels

A novel adsorption differential volumetric apparatus to measure mass transfer in nanoporous materials

A novel adsorption differential volumetric apparatus was developed for the determination of diffusional time constants in nanoporous materials and applied to diffusion of nitrogen and argon in commercial pellets of 4A zeolite. The system is designed for high rates of data acquisition allowing to determine mass transfer time constants of seconds over the pressure range from vacuum to 130 kPa. Diffusion of N2 and Ar on a single pellet and fragments obtained from the pellet are studied between –10 °C and 35 °C and 0.8 to 55 kPa. These systems are chosen as representing weak adsorption to demonstrate the sensitivity of the apparatus that gives a good signal-to-noise ratio even with a single pellet in the entire pressure range. The systems studied confirm micropore diffusion control and an isothermal diffusion model was shown to reproduce accurately the observed kinetics using reduced pressure plots. As the crystal size in the pellet is not known accurately, the resulting activation energies and the ratio of diffusional time constants of N2 and Ar were used to validate the results against known literature values.

Atomic and Electronic Structures of an Ag-Containing 4a Zeolite

Atomic and Electronic Structures of an Ag-Containing 4a Zeolite

Investigating the properties and performance of 3A molecular sieves as an adsorbent to prevent coke formation in olefin dehydration process

Abstract To study the affinity of 3A aluminosilicate adsorbents to prevent oligomerization of olefin molecules and forming green oil, physical and chemical properties of 3A molecular sieves are measured by using characterization techniques such as temperature-programmed desorption (TPD), nitrogen (N2) and water adsorptions, X-ray diffraction (XRD), X-ray fluorescence (XRF), crushing strength, and carbon dioxide (CO2) adsorption. Moreover, coke formation affinities of the understudy adsorbents are evaluated in a bench-scale system using 1-butene and 1,3-butadiene at temperatures of 220 and 260 °C, and outcomes are validated against the actual data gathered from an industrial scale olefin dehydration plant. Results confirm that the type of binder and the amount of ion exchange affect the performance of a 3A molecular sieve nominated for dehydrating olefinic streams. The binder with the least amount of acidity is preferred, and at least 35% of Na ions of the 4A zeolite should be exchanged with K ions to make it applicable for synthesizing an appropriate 3A molecular sieve. Furthermore, to control the oligomerization and inhibit green oil formation, the CO2 adsorption and acidity of Trisiv shape molecular sieves with the sizes of 1/4 inch should be less than 0.5 wt % and 1.7 mmol NH3/g, respectively. For extrudate shape with the sizes of 1/16 inch CO2 adsorption and acidity should be less than 0.2 wt % and 2.2 mmol NH3/g, respectively.

Controllable Preparation of Cubic Zeolite A and Application of Langmuir Model in Carbon Dioxide Adsorption.

A large amount of remaining fly ash has been piled up or landfilled, which not only a waste of land resources but also results in a series of environmental problems. Therefore, using fly ash to produce high value-added products is a win-win development orientation between human beings and nature. In this study, zeolite A is successfully synthesized using a hydrothermal method using fly ash. Additionally, it is at 1.0 mol·L−1 of the alkali concentration that the crystallinity of zeolite A reaches the maximum value, about 96.6%. FTIR research shows that the main secondary structural unit D4R vibration band of zeolite A appears at 555 cm−1. The results of the SEM study indicate the structure of zeolite A is cubic. The TEM results show that the crystal structure of the zeolite A belongs to the body-centered cubic structure. Meanwhile, the positively charged sodium ions cooperate with the silicon oxygen tetrahedron and the aluminum oxygen tetrahedron to form the zeolite A skeleton. Carbon dioxide adsorption equilibrium study shows that the maximum adsorption capacity of zeolite A of 46.5 mL·g−1 is significantly higher than the maximum adsorption capacity of commercial-grade zeolite 4A of 39.3 mL·g−1. In addition, the application of the Langmuir model in the adsorption of carbon dioxide by commercial-grade zeolite 4A and zeolite A is studied, which not only extends the application of zeolite A, but can be further extended to other zeolite materials as well. Meanwhile, the adsorption process belongs to the Langmuir model, which is a single layer adsorption on an ideal surface.

Microchannel zeolite 13X adsorbent with high CO2 separation performance

• Microchanneled zeolite monoliths for removal of CO 2 through phase separation. • CO 2 dynamic uptake of 3.4 mmol g −1 was obtained for 13X monoliths. • The monoliths present markedly low pressure drop under fast flow rate. • Mass transfer resistance in monolith significantly lower than those for beads. • Ultra high mechanical strength and thermal conductivity for zeolite adsorbent. Uniform 13X films with thicknesses of 3 and 11 µm were grown on supports in the form of steel monoliths with a cell density of 1600 cpsi and microchannels width of 0.5 mm. Sharp breakthrough fronts and a dynamic uptake of 3.4 mmol CO 2 g −1 zeolite were observed in the forwarding step of breakthrough experiments for a feed of 10% CO 2 in N 2 with a high flow rate at 293 K and 1 bar. Numerical modeling showed that the adsorption process was very fast and that the transport of CO 2 in the thin zeolite layer was the rate-limiting step, the mass transfer resistance for the 11 µm film is 2.2 times lower than zeolite 13X pellets and 100 times lower than zeolite 4A beads. Axial dispersion, pressure drop, and gas film resistance were shown to be negligible. The steel monolith support provides good mechanical strength and excellent thermal conductivity for the 13X films. The combination of properties makes this adsorbent a good performer when compared with other types of structured zeolite adsorbents in reported literatures. This microchannel adsorbent is a promising alternative to traditional adsorbents in processes of fast CO 2 separation with short cycle times.