Zeolite Bed Research Articles

Enhanced Fischer-Tropsch synthesis through structured bed configurations and zeolite integration

The highly exothermic nature and wide range of products of the Fischer-Tropsch (FT) synthesis motivated the study of the influence of different fixed bed configurations on the conversion stability and selectivity of the system. A cobalt catalyst (Co-Ru/Al2O3) was synthesized as a fixed-bed powder reference and compared with monoliths (230 and 770 cpsi) loaded by the washcoating method. The monolith with the lowest cell density showed the greatest stability among the systems evaluated, with no drop in CO conversion during the 50-hour test. The same powder bed was compared with dual-bed configurations and physical mixing with HZSM-5 zeolite. These experiments showed that by adding HZSM-5 zeolite bed after the FT catalyst one can effectively increase the gasoline range selectivity, without favoring the formation of methane and C2-C4 gases. However, when the same mass of zeolite was physically mixed in a single bed, the formation of the C1-C4 fraction increased from 23 % to 33 %. The strategies employed improved product distribution and reduced the deactivation rate compared to the conventional single bed.

An Insight into the CO2 Adsorption and Temperature Evolution of a Zeolite Bed in a Fluidized Bed Reactor Using a Two-Fluid Modeling Approach

An Insight into the CO₂ Adsorption and Temperature Evolution of a Zeolite Bed in a Fluidized Bed Reactor Using a Two-Fluid Modeling Approach

Investigating the role of promoters (Ga, Nb, La, and Mg) on In2O3-based catalysts: Advancing on CO2 hydrogenation to C5+ hydrocarbons

Utilizing carbon dioxide (CO2) as a sustainable feedstock for producing chemicals and renewable fuels is of paramount importance, particularly in the face of intricate climate changes. However, despite significant CO2 hydrogenation advancements to different C1 chemicals, synthesizing value-added products with more carbons remains challenging due to the extreme inertness of CO2 and the high C–C coupling barrier. Thus, herein, we introduce a series of In2O3-promoted catalysts with different basicities (Ga/In2O3, Nb/In2O3, La/In2O3, and Mg/In2O3) to evaluate their role in the production of methanol that was used as an intermediate for the production of gasoline-range hydrocarbons after going through an HZSM-5 zeolite bed. While oxygen vacancies on the catalysts' surfaces are undoubtedly crucial, we have observed that the basicity of the promoters plays a significant role in their effectiveness. Interestingly, there seems to be a threshold regarding this matter, meaning that the promoter must possess an intermediate level of basicity. However, CO2 adsorption becomes excessively strong when the promoter is too basic, favoring the undesired reverse-water gas shift (RWGS) reaction and CH4 formation with acid counterparts. Our findings showed that the Ga-promoted In2O3 catalyst with intermediate basicity balances activity and selectivity, resulting in a higher yield of hydrocarbons. The observed outcome highlights the significant role of catalyst component interactions in suppressing undesirable reactions and improving overall performance. The Ga-promoted catalyst exhibited higher selectivity for hydrocarbons, averaging 61%, compared to In2O3, which achieved a selectivity of 54%.

Purification of hydrogen as green energy with pressure-vacuum swing adsorption (PVSA) with a two-layers adsorption bed using activated carbon and zeolite as adsorbent

Today, hydrogen is produced in refineries and petrochemicals using the methane reforming process, followed by a water gas shift reaction stage. The hydrogen produced has a purity of approximately 75%, and is purified further through an adsorption process. In this project, the feasibility of achieving a purity level greater than 90% through the use of a more effective adsorbent and the periodic process of pressure vacuum swing adsorption (PVSA) with a double-layer bed of active carbon and zeolite will be investigated. The design, simulation, and optimization of the hydrogen purification unit will also be conducted. The results of this study indicate that the proposed process can achieve a purity level of up to 97% for the output hydrogen.

Isotherms and Kinetics Study for Adsorption of Nitrogen from Air using Zeolite Li-LSX to Produce Medical Oxygen

This research investigates the adsorption isotherm and adsorption kinetics of nitrogen from air using packed bed of Li-LSX zeolite to get medical oxygen. Experiments were carried out to estimate the produced oxygen purity under different operating conditions: input pressure of 0.5 – 2.5 bar, feed flow rate of air of 2 – 10 L.min-1 and packing height of 9-16 cm. The adsorption isotherm was studied at the best conditions of input pressure of 2.5 bar, the height of packing 16 cm, and flow rate 6 Lmin-1 at ambient temperature, at these conditions the highest purity of oxygen by this system 73.15 vol % of outlet gas was produced. Langmuir isotherm was the best models representing the experimental data., and the model parameters were the maximum monolayer coverage (qm) 200 mg. g-1 and Kl 0.00234 L.mg -1. Also, from the Freundlich isotherm model, the sorption intensity (n) indicated favorable sorption of 1.435. The average free energy estimated from the DRK isotherm model was 0.02 KJ.mol-1, which proved the adsorption process to follow physical nature. The results got from experiments showed a coincidence to the pseudo-first-order kinetic model.

Cyclic zinc capture and zeolite regeneration using a column method, mass transfer analysis of multi regenerated bed.

Treatment of wastewater and reuse of purified water in an industrial process can provide an alternative source of fresh water as well as reduce pollution load by discharging a lower quantity of wastewater. When adsorption is used for treatment, the regeneration of the used adsorbent may also account for a large portion of the operational cost and cause secondary pollution. This problem may be solved by cyclic repetition of adsorption/regeneration cycles using a column method. In this paper, a total of nine successive cycles of zinc capture and zeolite bed regeneration using a column method have been investigated. The derived form of the breakthrough curve was used for analysing mass transfer in the column. For that purpose, the Dose-response, the Thomas, the Bohart-Adams, the Yoon-Nelson and the Wolborska models were used for modelling the breakthrough curve by nonlinear regression analysis. Simulation results and mathematical similarities between the models were discussed. This is the first study that used derived form of Dose-response model to analyse the inflection points of the breakthrough curve and mass transfer during nine consecutive sorption-regeneration cycles of zinc ions on natural zeolite. Obtained peak shape rate profiles were analysed for all cycles. Optimal operation conditions were evaluated with respect to the inflection point, the model parameters, and the residence time.

Performance of sorption thermal energy storage in zeolite bed reactors: Analytical solution and experiment

Sorption thermal energy storage (STES) has the advantage of high energy storage density and low heat loss, which has been considered as one of the promising solutions to achieve carbon neutrality in buildings. An insight into the thermal energy storage performance of reactors enables the optimization of STES systems. In addition, the analytical solution is concise and understandable in physical significance. In the present work, the perturbation theory was introduced to derive the analytical solutions for the fluid and solid temperatures in the reactor during the discharging process. Subsequently, a zeolite 13X STES system was built to conduct charging and discharging experiments. Based on the derived analytical solution, the fluid temperature at different axial positions in the reactor and energy storage density (ED) of zeolite were calculated and compared with the measured data. The results showed that there was a good agreement between the experimental test and the analytical solution, in which the maximum deviation of the energy storage density was less than 4 %. The analytical solution could obtain specific functional expressions for STES performance parameter of ED and further receive the results quickly.

Superhydrophobic Surface-modified zeolite to regulate the migration of nonadsorbed liquid water in an Open-loop adsorption heat pump

Superhydrophobic surface-modified zeolite 13X has been utilized to regulate nonadsorbed liquid water in an open-loop adsorption heat pump system for steam generation. The zeolite is modified by vinyltrimethoxysilane to achieve a superhydrophobic surface effect. The measured static water contact angles of the modified zeolite reached 152°. Thermogravimetric analysis results show good thermal stability at temperatures less than 400 °C. The measured adsorption capacity and adsorption heat slightly decrease for the modified zeolite. During the regeneration process dry air at 140 °C drives wet zeolite to remove adsorbed and free water. Then generation process proceeds for steam generation at a maximum of 220 °C from water at 72 °C. The mass and temperature of the steam generated from the modified zeolite bed increase compared with those of unmodified zeolite 13X. This is because of the apparent decrease in the total amount of free water, which allows the released adsorption heat to be transferred to passing water quickly for steam generation. Energy consumption during regeneration simultaneously reduces. System indicators such as the coefficient of performance for heating (COPh), specific heating power (SHP), gross temperature lift (GTL) and exergy efficiency (ηe) increase with increasing hydrophobicity of zeolite particles. The surface hydrophobicity decreases the affinity of zeolite for useless free water which cannot contribute to increasing the overall adsorption heat.

CAPTURE OF CARBON DIOXIDE FROM SEWAGE SLUDGE PYROLYSIS GASES IN A FIXED BED OF 13X ZEOLITE

Pyrolysis gases can be upgraded through CO2 adsorption. This work shows the pyrolysis of sewage sludge in a 1 kg h−1 rotating cylinder reactor. Non-condensable gases passed through a fixed bed of 13X zeolite at 40 ◦C. Prior to processing actual pyrolysis gases, the equilibrium adsorption capacity of the 13X was evaluated with synthetic CO2 in a magnetic suspension balance to estimate Langmuir, Freundlich and Toth isotherm parameters. Afterwards, a synthetic mixture with composition similar to that of sewage pyrolysis gases was tested in a bench-scale fixed-bed adsorption column to assess both the breakthrough curves for different adsorbent masses (10, 15, and 20 g) and the saturation time of the adsorbent. The dynamic adsorption in the column was modeled as a system of partial differential equations (PDEs), which was transformed into a system of Ordinary Differential Equations (ODEs) via the Method of Lines and, then, solved using DASSL. The ODEs were used to estimate adsorption parameters such as coefficient of axial dispersion, effective diffusivity within the particle, and external coefficient of mass transfer. The synthetic gases were replaced with actual sewage sludge pyrolysis gases in the adsorption column with 13X. The breakthrough curves revealed a quick saturation of the bed by pyrolysis aerosols. Despite its short lifetime in comparison with synthetic gases, the 13X proved effective in adsorbing pyrolysis CO2.

MW-Assisted Regeneration of 13X Zeolites after N2O Adsorption from Concentrated Streams: A Process Intensification

N2O has a global warming potential about 300 times higher than CO2, and even if its contribution to the greenhouse effect is underrated, its abatement in industrial production’s tail gas has become imperative. In this work, we investigate the feasibility of the microwave (MW)-assisted regeneration of a 13X zeolite bed for N2O capture from tail gases. Several consecutive adsorption–desorption cycles were performed to verify the microwave heating effect on the zeolite’s adsorption properties. The results of the experimental tests, performed at N2O concentrations of 10, 20 and 40% vol, highlighted that (i) the steps are perfectly repeatable in terms of both adsorbed and desorbed amount of N2O, meaning that the MWs did not damage the zeolite’s structure, (ii) the presence of both H2O and O2 in the feed stream irreversibly reduces the adsorbent capacity due to nitrites and nitrates formation, and (iii) the presence of H2O alone with N2O still reduces the adsorbent capacity of the zeolites, which can be recovered through MW-assisted regeneration at 350 °C. Moreover, the MW-assisted TSA assured an energy and purge gas saving up to 63% and 82.5%, respectively, compared to a traditional regeneration process, resulting in effective process intensification.

Thermodynamics of translational and rotational dynamics of C9 hydrocarbons in the pores of zeolite-beta

There has been a growing interest in the separation of aromatic hydrocarbon molecules from the petroleum stream using zeolite-based technologies. This led to numerous experimental and molecular simulation studies of the structural and dynamical properties of aromatic hydrocarbons under the confinement of microporous materials like zeolites. The understanding of the behavior of the isomers of the trimethylbenzene under confinement is crucial for their separation and purification from industrial streams. Here, we investigate the translational and rotational dynamics and associated thermodynamics of three isomers of trimethyl benzene, namely, 1,2,3-trimethyl benzene (1,2,3-TMB), 1,2,4-trimethyl benzene (1,2,4-TMB), and 1,3,5-trimethylbenzene (1,3,5-TMB) under the confinement of zeolite-beta (BEA) using molecular dynamics (MD) simulations. The trends in the diffusion coefficients of the TMB isomers calculated from our MD simulation data are in good agreement with the data already available in the literature. Analysis of dynamics and associated thermodynamic properties indicate that 1,2,4-TMB is translationally more facile than the other two isomers. The rotational motion of TMB isomers is largely anisotropic and it is relatively more significant for both 1,2,4-TMB and 1,3,5-TMB. The thermodynamic properties reveal that the distinguishability in the dynamic properties among these three isomers is essentially caused by entropy. These results are not only critical to engineer the separation process of TMB isomers across the zeolite beds but also to understand the different catalytic processes such as trans-alkylation, conversion, cracking etc.

Scale-up of open zeolite bed reactors for sorption energy storage: Theory and experiment

Sorption energy storage (SES) technology has been considered one of the promising solutions to cope with the ever-increasing carbon emissions from buildings. Nevertheless, it is still elusive the extrapolation of conclusions from pilot-scale experiments to full-scale ones. In the present work, a relaxation technique was introduced to develop a scale-up model for SES reactors. A full set of scaling ratios of parameters for an analog reactor to those for a prototype reactor was explored, which theoretically ensured the similarity of the two reactors in geometry, dynamics, sorption-kinetics, and thermal performance. Subsequently, charging and discharging experiments were conducted in two geometrically similar reactors. Four performance ratios of the analog values to prototype values were calculated based on the measured data and were compared with theoretical values derived from the scale-up model. The results showed that these ratios were in good agreement with corresponding theoretical values, where the maximum deviation was less than 10%. Based on the developed scale-up model, a small-scale reactor can duplicate the thermal performance of a large-scale reactor on a miniature dimensional scale and in a reduced time scale.

The effect of an Al-based cellular structure on the thermal performance of a zeolite-based hybrid heat accumulator

The heat accumulator designed for the purposes of this study consists of two chambers with metal foam structures and honeycomb segments casted by the means of investment casting from an AlSi alloy. The cellular metal castings, characterized by a relatively large coefficient of thermal conductivity, provide rapid transport of heat energy from the source to the heat storage materials (paraffin or zeolite). In order to simulate the conditions of solar heating, two outdoor halogen reflectors were used for the heating stage. Multiple long-term cycles of charging and discharging of this heat accumulator, with and without porous metallic inserts to improve the thermal conductivity and increase the heat transfer area, were conducted and subsequently analysed. The metal foams are suitable for enhancing heat transfer in a zeolite bed, whereas the durable honeycomb casting is preferable for phase change material. Additionally, the porous foam improves the conditions for transporting vapour during dehydration/hydration. The application of cast inserts in the zeolite chamber helped to decrease the temperature gradient to below 50 °C. The overall amount of energy stored in the hybrid TES unit equaled 7676.4 kJ (2.14 kWh).

Performance and onsite regeneration of natural zeolite for ammonium removal in a field-scale non-sewered sanitation system

Natural zeolite clinoptilolite was used as the primary ammonium removal method from the permeate of an anaerobic membrane bioreactor (AnMBR) treating high-strength blackwater generated from a community toilet facility. This zeolite-based nutrient capture system (NCS) was a sub-component of a non-sewered sanitation system (NSSS) called the NEWgenerator and was field tested for 1.5 years at an informal settlement in South Africa. The NCS was operated for three consecutive loading cycles, each lasting 291, 110, and 52 days, respectively. Both blackwater (from toilets) and blackwater with yellow water (from toilets and urinals) were treated during the field trial. Over the three cycles, the NCS was able to remove 80 ± 28%, 64 ± 23%, and 94 ± 11%, respectively, of the influent ammonium. The addition of yellow water caused the rapid exhaustion of zeolite and the observed decrease of ammonium removal during Cycle 2. After Cycles 1 and 2, onsite regeneration was performed to recover the sorption capacity of the spent zeolite. The regenerant was comprised of NaCl under alkaline conditions and was operated as a recycle-batch to reduce the generation of regenerant waste. Modifications to the second regeneration process, including an increase in regenerant contact time from 15 to 30 h, improved the zeolite regeneration efficiency from 76 ± 0.7% to 96 ± 1.0%. The mass of recoverable ammonium in the regenerant was 2.63 kg NH4-N and 3.15 kg NH4-N after Regeneration 1 and 2, respectively. However, the mass of ammonium in the regenerant accounted for only 52.8% and 54.4% of the estimated NH4-N originally sorbed onto the zeolite beds after Cycles 1 and 2, respectively. The use of zeolite clinoptilolite is a feasible method for ammonium removal by NSSS that observe variable nitrogen loading rates, but further research is still needed to recover the nitrogen from the regenerant waste.

Treatment efficiency of synthetic urban runoff by low-cost mineral materials under various flow conditions and in the presence of salt: Possibilities and limitations

Urban runoff belongs to important carriers of pollutants that during infiltration can accumulate in the soil/water environment. One of the protection solutions may be the enhancement of infiltration systems by horizontal permeable treatment zones. The article presents the results of column tests carried out in order to determine (1) the influence of the hydraulic loading rate on the dynamic capacities of selected reactive materials: low-cost mineral materials (zeolite, limestone sand, halloysite) and reference material (activated carbon), and control soils (topsoil and Vistula sand) against Zn, NH4+ and PO43−, and (2) remobilization of contaminants under the influence of salt (NaCl 5 g/L) present in synthetic runoff water. The research has revealed that the most useful for the removal of zinc ions was limestone sand (>4.36 mg/g), of orthophosphates – halloysite (2.29 mg/g on the average), and of ammonium ions – zeolite (2.75 mg/g on the average). The control soils were characterized by low ability to immobilize the contaminants tested. In addition, increase in the hydraulic loading rate of synthetic runoff water reduced the dynamic capacity of materials to a variable degree depending on the material applied and the contamination removed (by 24% for limestone sand-PO43− system to 95% for activated carbon-NH4+ system). The presence of NaCl caused significant leaching of ammonium ions from zeolite and halloysite filter beds (up to 99.3%), and phosphates from the activated carbon filter bed (up to 41.3%). All tracer contaminants tested leached intensively from the Vistula sand filter bed, while only ammonium ions leached from the topsoil filter bed. It seems justified to support the performance of infiltration systems by layers of: limestone sand, to enhance the processes of heavy metal precipitation and ammonium ion volatilization by increasing the pH, and halloysite for the sorption of phosphates.

Heat Transfer in Adsorption Chillers with Fluidized Beds of Silica Gel, Zeolite, and Carbon Nanotubes

One of the main disadvantages of conventional fixed-bed adsorption chillers is the low coefficient of performance due to the high voidage of the sorbent beds. The common method, which can help to handle this problem, is modifying the beds’ design, including the application of fluidization. An innovative idea, shown in the article, constitutes in the use of the fluidized bed of sorbent, instead of the conventional, fixed-bed, commonly used nowadays in the adsorption chillers. Bed-to-wall heat transfer coefficients for fixed and fluidized beds of adsorbent are determined in the study. Effects of Sorbent particles diameters and velocities of fluidizing gas are discussed in the study. The calculations confirmed that the bed-to-wall heat transfer coefficient in the fluidized bed of adsorbent is much higher than that in a conventional bed. The proposed idea allows significantly reducing the size of a chiller and overcome the main reason for the limited dissemination of the adsorption cooling technology.

Zeolite Heat Storage: Key Parameters from Experimental Results with Binder‐Free NaY

AbstractThe application of heat storage systems in households or the industry is one possibility to optimize the degree of heat utilization and to reduce greenhouse gas emissions. In contrast to established heat storage systems based on water, zeolitic systems reach energy densities of 150–200 kWh m−3 and allow for seasonal storage with almost no heat loss. However, a commercial breakthrough was not yet successful. Given this background, it is the aim of the present study to identify appropriate operational parameters for a zeolite heat storage system in the laboratory and to prepare an upscaling to demonstration scale. To this end, the pressure drop of the zeolite bed, the cycle time, and the optimal process parameters during thermal loading and deloading were determined.

Prediction of the effective thermal conductivity of an adsorption bed packed with 5A zeolite particles under working conditions

To predict effective thermal conductivity (ETC) of an adsorption bed during the adsorption process, a scale-up model is established that couples a macro-level comprehensive thermal conductivity model and a microlevel grand canonical Monte Carlo (GCMC) method. The effect of the adsorbed phase on the gas phase thermal conductivity is comprehensively considered. The proposed model is validated with experimental data for the thermal conductivities of the zeolite adsorbent particles and bed. Comprehensive sensitivity analyses regarding the effects of the pressure and temperature on the ETC of the adsorption bed are conducted. The results show that the thermal conductivities of the zeolite adsorbent particles and bed can be divided into three regions, namely, the weak adsorbed phase region (0–0.1 kPa), the adsorbed phase and gas phase competitive region (0.1–50 kPa), and the saturation adsorption region (50–1000 kPa). Inflection point temperatures of 350, 450, and 600 K are identified for the three regions. The gas adsorption effect can be ignored when the temperature is higher than these inflection point temperatures. The ETC of the adsorption bed will be underestimated when the adsorption phase is not considered, and it will be overestimated when the coupled effect of the adsorption phase and gas phase is ignored.

Heat Transfer Prediction of a Zeolite Bed Through Addition of Metal Additives

Heat Transfer Prediction of a Zeolite Bed Through Addition of Metal Additives

Performance and characteristics of continuous, fluidized bed pyrolysis of reed black liquor

Fluidized bed pyrolysis is a promising technology for recovering value from reed black liquor (RBL) but it can be limited by agglomeration of the bed material and loss of fluidization. To address this challenge, laboratory experiments examined the continuous, fluidized bed pyrolysis of RBL using two different bed materials at temperatures ranging from 530 to 780 °C. Pyrolysis with silica sand as the bed material showed sintering within 120 s and loss of fluidization at a bed temperature of 680 °C. Pyrolysis with calcium-based zeolite as the bed material retained fluidization for the entire test period of 30 min at all temperatures examined. Increasing pyrolysis temperature with the calcium-based zeolite increased H2 generation and decreased tar production, with the highest temperature examined (780 °C) providing the best performance. Fluidized bed combustion of the pyrolysis char (both at 780 °C) recovered 87% of the sodium in the RBL. Pyrolysis of RBL using fluidized bed technology with a calcium-based zeolite bed material is feasible and effective.