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At least 19 records

Comparison of microwave and conventional heating for CO 2 desorption from zeolite 13X

In this study, we investigate microwave irradiation as an alternative to conventional heating for temperature swing adsorption processes. The performance of microwave and conventional heating during sorbent regeneration was evaluated by measuring CO 2 desorption from zeolite 13X at different temperatures. Experimentally, a fixed bed of zeolite 13X was saturated by a 150 sccm flow of 15 % CO 2 at room temperature followed by sorbent regeneration under nitrogen at 55, 100, or 150 °C by applying either microwave irradiation or conventional heating. Microwaves reduced sorbent regeneration times by at least half compared to regeneration by conventional heating. Under conventional regeneration, desorption curves were resolved into two peaks representing physisorbed CO 2 (mass diffusion limited) at low temperature and bicoordinated CO 2 (thermally limited) with increasing temperature. Under microwave regeneration, only one desorption peak was observed suggesting that CO 2 desorption was limited by mass diffusion through the porous zeolite 13X structure, rather than by temperature. Depending on microwave power, apparent activation energy of the microwave-assisted regeneration was 15.8–18.1 kJ/mol, compared to 41.5 kJ/mol for conventional regeneration. The reduction in apparent activation energy is mainly attributed to selective microwave heating of CO 2 adsorption sites (Na + sites) resulting in greater steady state temperatures of Na + relative to framework atoms, suggesting greater heating efficiency due to microwaves compared to conventional heat transfer. Due to rapid cycling and efficient heat transfer to CO 2 sites on zeolite 13X, microwave regeneration is found to increase adsorption/desorption cycling productivity and potentially reduce the energy penalty of temperature swing capture.

54 ENVIRONMENTAL SCIENCES↗

Fabrication of yeast engineered porous 13X adsorbent layers for CO 2 capture

This study investigates a novel environmentally friendly coating technique using yeast fermentation to obtain super porous Zeolite 13X adsorbent layers through freeze-drying technique for CO 2 capture applications. Several mass ratios of sugar to yeast were used to control the porosity and pore sizes in the adsorbent layer. A unique peeling process was integrated to obtain foamy, hollow structures to have deeper layer accessibility of adsorbent for adsorption applications. These coated adsorbent layers were experimentally characterized as a function of the mass ratio of sugar to yeast and adsorbent solid fraction. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Fourier-transform infrared spectroscopy (FT-IR) are used to analyze the coated layers. Here, the void fraction for coated samples is found to vary between 0.48 and 0.56, making the samples applicable for adsorption applications. Adsorption performance experiments are performed to test the coated samples' performance compared to 13X powder. Due to their simplistic fabrication, cost-effectiveness, rapid pore formation, and high adsorption capacity, these porous 13X layers hold potential for large-scale fabrication and CO 2 capture applications.

Adsorbent coating↗

Plasma catalytic non-oxidative methane conversion to hydrogen and value-added hydrocarbons on zeolite 13X

Non-thermal plasma has unfolded highly efficient, safe to operate novel routes for methane conversion to hydrogen. In this work, methane conversion is performed under atmospheric dielectric barrier discharge (DBD) plasma with and without 13X zeolite-based catalysts i.e., 13X, Ga/13X, Pd/13X, and Pd-Ga/13X. Experimental results indicate that the plasma catalytic process delivered almost twofold higher product yield than the plasma only route. The binary Pd-Ga catalyst possesses highest catalytic performance with about 40 % CH 4 conversion at an input flowrate of 5 cm 3 min -1 and 2W due to the formation of the Pd-Ga alloy, which acts as catalytic active centre for activating C–H bonds. Product yield can be tailored by the catalyst design where the bimetallic Pd-Ga/13X preferably favours the hydrocarbon formation while H 2 is the dominant product obtained over the Pd/13X. The cleavage of C–H bonds of methane molecule over the plasma only route is mainly governed by energetic electrons in the gaseous phase the catalyst activity, and plasma-catalyst synergism play a significant role in the plasma catalysis process. Further, the findings from this work provide significant insights into the methane activation for subsequent optimization of the methane conversion processes operated on floating production, storage, and offloading vessels (FPSOVs). Exploiting untapped offshore natural gas reserves, where conventional pipeline systems are less economical.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

Isotope exchange of ND 3 on Pt catalyst-loaded 13X molecular sieve

During D-T fusion operations the capture, purification, and recycling of unburned tritium will be crucial, as the formation of tritium containing molecules require additional processing. Here, removing the tritium can require costly processing to be unbound from the tritium-containing molecules and improvements to these processes will be necessary moving forward. Existing techniques using sorbent material beds to remove tritium-containing molecules from process gas streams undergo repeated high-heat cycling which leads to diminished bed lifespans, necessitating replacement and associated downtime. This work demonstrates the capture and isotopic exchange technique of deuterated ammonia (ND3), used as a surrogate for tritium, at ambient temperature using a Pt catalyst-loaded 13X molecular sieve. Unmodified 13X molecular sieve is capable of adsorbing and retaining the ND3 however, incorporation of a catalyst facilitates the isotopic exchange of the hydrogen isotopes. The effluent gas streams were analyzed in conjunction with desorbed ammonia isotopologues post-exchange to verify these results. Isotopically exchanging and removing heavier hydrogen isotopes using this technique provides an alternative to traditional removal methods.

08 HYDROGEN↗

Evaluation of adsorption and mechanical strength of 13X zeolite mixtures with phyllosilicate binders using molecular dynamics simulation and positron annihilation spectroscopy

There is growing interest in developing zeolites with novel internal structures that have optimal adsorptive capacity and high mechanical strength, while offering advantages, such as being light weight. We integrate computational and experimental methods to explore the effect of binder/zeolite types, and weight percentages on the mechanical strength of 13X zeolite and adsorption capacities of N 2 , H 2 O, and CO 2 for additive manufacturing (AM) applications with the goal of maximizing both adsorption and strength. Zeolite 13X mixtures and phyllosilicate binders (either bentonite or kaolin) are combined using molecular dynamics (MD) simulations to create structures with various binder/zeolite weight percentages. Further, adsorption capabilities and mechanical strength are assessed using the grand canonical Monte Carlo (GCMC) and ReaxFF modules, respectively. Our modeling shows that an optimized zeolite/binder ratio for N 2 adsorption is around 15 wt% for kaolin and roughly 10 wt% for bentonite. The resulting parameters can be applied to facilitate macro-scale computational fluid dynamics (CFD) and finite element method (FEM) simulations of an AM zeolite structure. We also performed Positron Annihilation Lifetime Spectroscopy (PALS) measurements on zeolite samples to explore the effect of changes in the internal volume. The results show an inverse relationship between the free volume and the solid loading and adding a binder changes the morphology of the zeolite-binder compound and decreases open-volume area significantly.

36 MATERIALS SCIENCE↗

Co-Adsorption of Carbon Dioxide on Zeolite 13X in the Presence of Preloaded Water

Environmental Control and Life Support requires highly effective CO2 removal systems. The current system onboard the International Space Station is known as Carbon Dioxide Removal Assembly. Recent high-fidelity simulation of this system predicted a major efficiency gain via reduction of desiccant zeolite. Commercial beaded 13X zeolite is used in the desiccant bed to scrub water below 1 ppm but is also a highly active CO2 sorbent. The simultaneous adsorption of water vapor and CO2 is known to strongly favor water, but more accurate measurements are needed. This work details the characterization of the zeolite to be used in the next-generation CO2 removal system for co-adsorption of water and CO2.

Cmarik, Gregory E↗

Zeolite Degradation: An Investigation of CO2 Capacity Loss of 13x Sorbent

System testing of the Carbon Dioxide Removal and Compression System (CRCS) has revealed that sufficient CO2 removal capability was not achieved with the designed system. Subsystem component analysis of the zeolite bed revealed that the sorbent material suffered significant degradation and CO2 loading capacity loss. In an effort to find the root cause of this degradation, various factors were investigated to try to reproduce the observed performance loss. These factors included contamination by vacuum pump oil, o-ring vacuum grease, loading/unloading procedures, and operations. This paper details the experiments that were performed and their results.

Air Revitalization↗

Co-Adsorption of Carbon Dioxide on Zeolite 13X in the Presence of Preloaded Water

Background: Carbon Dioxide removal is a key aspect of Life Support for long-duration missions - Need to improve Mass, Power, and Volume of systems; Cabin air has three major constituents - Oxygen and Nitrogen, Carbon dioxide (CO2), Water Vapor; The mechanism for strong CO2 adsorption in zeolites (and many sorbents) is also the same mechanism for H2O - Water vapor is selectively adsorbed over CO2.

Cmarik, Gregory E.↗

Zeolite Degradation: An Investigation of CO2 Capacity Loss of 13x Sorbent

System testing of the Carbon Dioxide Removal and Compression System (CRCS) has revealed that sufficient CO2 removal capability was not achieved with the designed system. Subsystem component analysis of the zeolite bed revealed that the sorbent material suffered significant degradation and CO2 loading capacity loss. In an effort to find the root cause of this degradation, various factors were investigated to try to reproduce the observed performance loss. These factors included contamination by vacuum pump oil, o-ring vacuum grease, loadingunloading procedures, and operations. This paper details the experiments that were performed and their results.

ECLSS↗

Microwave-induced selective decomposition of cellulose: Computational and experimental mechanistic study

Understanding microwave-material interactions will help facilitate the utilization of microwave technology in gasification and renewable energy production. In this study, cellulose was used as a model compound to simulate the organic matter in biomass, and its catalytic decomposition under a microwave (MW) field was studied to identify structural changes from the reaction. The study was conducted using a MW source coupled to a fixed-bed gas-flow reactor, mass spectroscopic, and Fourier transform infrared spectroscopy post-reaction analysis. Zeolite 13X was chosen as a microwave absorber to study the catalytic enhancement of the decomposition of cellulose. Density functional theory (DFT) was used to gain insights into the molecular transformations occurring in the presence of a static electric field, which was used to simulate the electric field component of the microwave electromagnetic radiation. Theoretical calculations demonstrated that both the positive and negative portion of the electric field interact with the permanent dipoles of the cellulose effecting the decomposition through the glycosidic bond breaking mechanism. The theoretical result was verified using infrared spectroscopic analysis of the pure cellulose during microwave heating. The theoretical calculations suggest only the positive electric field component may be active for the cellulose decomposition in the presence of Zeolite 13X. Physically mixing Zeolite 13X with the cellulose led to a significant enhancement in the decomposition rate of the glycosidic bond. Zeolite 13X enhanced the glycosidic O-C decomposition at lower MW power (lower temperatures), whereas the O-H functional group required higher MW power (higher temperature) for its decomposition. The DFT study coupled with the reaction studies revealed that the electric field polarizability is dependent upon both the direction and the orientation of the cellulose. Gas products revealed that applying 250 W of MW power led to the production of CO, H 2 , along with some CO 2 , CH 4 , and benzene at 305 °C. Finally, reaction under 500, 750, and 1000 W of power at constant temperature (305 °C) revealed that higher power led to the complete decomposition of cellulose to mostly CO, H 2 , and CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

CO2 Capacity Sorbent Analysis Using Volumetric Measurement Approach

In support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various solid sorbents to complement structural strength tests conducted at Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13X, Honeywell UOP APG III, LiLSX VSA-10, BASF 13X, and Grace Davison Grade 522 5A. CO2 capacity was for all sorbent materials using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0 C, 10 C, 25 C, 50 C, and 75 C isotherms. These data are to be used for modeling data and to provide a basis for continued sorbent research. The volumetric analysis method proved to be effective in generating consistent and repeatable data for the 13X sorbents, but the method needs to be refined to tailor to different sorbents.

Huang, Roger↗

CO2 Capacity Sorbent Analysis Using Volumetric Measurement Approach

In support of air revitalization system sorbent selection for future space missions, Ames Research Center (ARC) has performed CO2 capacity tests on various solid sorbents to complement structural strength tests conducted at Marshall Space Flight Center (MSFC). The materials of interest are: Grace Davison Grade 544 13X, Honeywell UOP APG III, LiLSX VSA-10, BASF 13X, and Grace Davison Grade 522 5A. CO2 capacity was for all sorbent materials using a Micromeritics ASAP 2020 Physisorption Volumetric Analysis machine to produce 0C, 10C, 25C, 50C, and 75C isotherms. These data are to be used for modeling data and to provide a basis for continued sorbent research. The volumetric analysis method proved to be effective in generating consistent and repeatable data for the 13X sorbents, but the method needs to be refined to tailor to different sorbents.

Air Revitalization↗

(Preliminary) Effects of Ball Milling Zeolite Powders for Use in Additively Manufactured Solid Sorbents

Zeolite 13X is favorable to be used as an adsorbent in carbon dioxide (CO2) removal from the spacecraft cabin air. Reducing the size of the zeolite particles and particle size distribution is thought to increase the capacity of CO2 adsorption of the zeolite 13X powder, and potentially increase its manufacturability as a paste for additive manufacturing or slip casting. This paper will go into detail on the process of using ball milling in order to reduce particle size and particle size distribution of commercial zeolite 13X powder, as well as to characterize CO2 adsorption and manufacturability of the milled powder. Both dry and wet ball milling was analyzed during the experiment. Studies were also ran on the amount of time the powder was milled, rotational speed of the milling machine, ball to powder ratio, ball to jar ratio, and ethanol to powder ratio. The processed powder was then characterized through laser diffraction, SEM, and surface measurement techniques to show that particle size and particle size distribution could be reduced, and to show the effect of the reduced particle size and particle size distribution on CO2 adsorption and manufacturability.

zeolite↗

Scaled-up fabrication of durable and porous adsorbent-coated minichannels on aluminum for CO 2 separation

A method was developed to fabricate zeolite 13X adsorbent-coated minichannels on aluminum for CO₂ adsorption applications in this study. It emphasizes the innovative use of aluminum as a substrate, which offers airtight assembly, paving the way for highly efficient adsorption systems. An optimized coating process was developed using a slurry of Zeolite 13X, yeast, sugar, and xanthan gum, resulting in durable and highly porous layers that enhance CO₂ capture performance. A PETG peeler was designed to remove the top layer of the yeast-engineered adsorbent coatings, revealing a super porous and foamy structure. The teeth of the peeler were designed and fabricated for high repeatability and rapid prototyping. Breakthrough experiments were conducted on the scaled-up adsorbent bed using gas mixtures of 80% CO₂, 20% N₂, and 20% CO₂, 80% N₂ to represent different industrial scenarios. The performance of the bed was evaluated at flow rates of 160 and 190 cm³ min -1 using a Raman Laser Gas Analyzer (RLGA), demonstrating stable adsorption without degradation across multiple cycles. Computational modeling of integral transport phenomena under the chosen experimental conditions was pursued using gPROMS ProcessBuilder™, and the modeling results were compared with those from the tests for adsorption time, which resulted in an error margin of 2% to 9% for the breakthrough time, confirming the easy reproducibility of the design through modeling. This research advances CO₂ capture technologies by providing an effective and scalable solution for producing aluminum-based adsorbent coated beds, supporting industrial carbon capture efforts.

CO2 capture↗

Analysis of energetics and economics of sub-ambient hybrid post-combustion carbon dioxide capture

Adsorption of CO 2 from post-combustion flue gas is one of the leading candidates for globally impactful carbon capture systems. In this report, work focused on understanding the opportunities and limitations of sub-ambient CO 2 capture processes utilizing a multistage separation process. A hybrid process design using a combination of pressure-driven separation of CO 2 from flue gas (e.g., adsorption- or membrane-based separation) followed by CO 2 -rich product liquefaction to produce high-purity (>99%) CO 2 at pipeline conditions is considered. The operating pressure of the separation unit is a key cost parameter and also an important process variable that regulates the available heat removal necessary to reach the sub-ambient operating conditions. The economic viability of applying pressure swing adsorption (PSA) processes using fiber sorbent contactors with internal heat management was found to be most influenced by the productivity of the adsorption system, with productivities as high as 0.015 mol CO2 /kg sorb -1 sec -1 being required to reduce costs of capture below $60/ton CO 2 captured. This analysis was carried out using a simplified two-bed process, and thus there is opportunity for further cost reduction with exploration of more complex cycle designs. Three exemplar fiber sorbents (MIL-101(Cr), UiO-66, and zeolite 13X) were considered for application in the sub-ambient process of PSA unit. Among the considered sorbents, zeolite 13X fiber composites were found to perform better at ambient temperatures as compared to sub-ambient. MIL-101(Cr) and UiO-66 fiber composites had improved purity, recovery, and productivity at colder temperatures reducing costs of capture as low as $61/ton CO 2 . Future economic improvement could be achieved by reducing the required operating pressure of the PSA unit and pushing the Pareto frontier closer to the final pipeline requirement via a combination of PSA cycle design and material selection.

42 ENGINEERING↗