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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Insights into co-pyrolysis of polyethylene terephthalate and polyamide 6 mixture through experiments, kinetic modeling and machine learning

The non-isothermal pyrolysis of polyethylene terephthalate (PET), polyamide 6 (PA6), and their mixtures was studied in a thermogravimetric analyzer at different heating rates. Temperature of maximum decomposition (T max ) decreased by 25–45 °C and 35–55 °C for the PET:PA6 mixtures (3:1, 1:1, 1:3) compared to PET and PA6, respectively. The kinetic analysis was initially carried out using isoconversional method. However, the dependency of activation energy on conversion was observed for the co-pyrolysis of PET and PA6 that suggested the occurrence of multi-step reactions in the mixtures. Distributed activation energy model (DAEM) was used in this study to describe the multistep reactions occurring during pyrolysis of PET:PA6 mixtures. Here, in this work, a four-parallel reaction DAEM was developed to describe the pyrolysis kinetics of PET:PA6 mixtures. The apparent mean activation energies (E o ) for PET, PA6, and mixtures varied in the range of 244–255, 140–215, and 138–255 kJ mol –1 , respectively. The mass loss profiles of PET and PA6 mixtures were also modeled using artificial neural network (ANN). Out of 155 ANN models, the best prediction was made by ANN511 with R 2 greater than 0.997 for both test and unseen data. The interaction effects observed through TGA experiments and subsequent kinetic analysis were further assessed in terms of product composition using analytical pyrolysis coupled with gas chromatograph/mass spectrometer (Py-GC/MS). Co-pyrolysis of PET and PA6 resulted in the formation of new aromatic compounds with nitrogen-containing functional groups, which were not detected when PET or PA6 were pyrolyzed individually.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Development of ceria-supported metal-oxide (MO x /CeO 2 ) catalysts via a one-pot chemical vapor deposition (OP-CVD) technique: Structure and reverse water gas shift reaction study

Current synthesis techniques for metal oxide (MO x )-supported catalysts have certain limitations of undesired target loading, ineffective dispersion of active species over the surface, uncontrolled particle size of active species, and complicated synthesis steps. Here, we developed a one-pot chemical vapor deposition (OP-CVD) methodology; by using which a solid metal precursor forms a vapor in a controlled condition and gets supported over the surrounding matrix. The theoretical stability followed by experimental validation using TGA is crucial for selecting the metal precursors. Three simple steps viz. premixing, dispersion, and rapid fixation by calcination are involved in the catalyst development via the OP-CVD approach. This study solely focused on the synthesis of 3d transition MO x over ceria support. The physicochemical characterizations of the prepared catalysts were performed by XRD, ICP-OES, SEM-EDX, CO pulse chemisorption, XANES, and EXAFS analyses to understand the crystal structure of involved species, target metal loading, dispersion, and particle size and prove the feasibility and viability of OP-CVD. The prepared catalysts were further tested for reverse water gas shift (RWGS) reaction to link their structural information with activity. The RWGS reaction data showed that the CO activity and CO selectivity were metal - and metal precursor-dependent. Higher CO activity of > 0.1 mol/h g-cat was observed for Cu and Co-based catalysts, with CO selectivity of ~100 %. This study provides an opportunity to produce efficient supported catalysts in a convenient way, providing effective catalytic activity.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Performance of fly ash concrete with ferronickel slag fine aggregate against alkali-silica reaction and chloride diffusion

Ferronickel slag (FNS) is an industrial by-product of ferronickel alloy production at a high temperature which can be a promising potential to be used as fine aggregate to produce more sustainable concrete. In this study, the performance of concrete containing ferronickel slag sand and fly ash relating to alkali-silica reaction (ASR) and chloride contamination was investigated. ASR-induced expansion, chloride diffusion resistance, and chloride binding capacity of FNS concrete were determined through concrete prism tests (CPT), accelerated diffusion test, and bulk diffusion test. Thermogravimetric analysis (TGA) was conducted to measure the amount of Portlandite and Friedel's salt in concrete. Concrete with 50 wt% FNS sand as fine natural aggregate replacement and 25 wt% of cement replacement by fly ash showed a remarkable potential to be used not only as a low-carbon concrete with comparable mechanical properties to conventional concrete but also with a better performance against ASR and chloride contamination.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Atomic structure and phase assemblages in novel M-(N)-A-S-H materials

This paper investigates the atomic structure and phase assemblages in new sodium-stabilized magnesium aluminosilicate hydrate (M-(N)-A-S-H) cementitious binders. Results indicate that in the absence of Ca{sup 2+}, Mg{sup 2+} promotes a binder atomic structure of Si-Al tetrahedral sheets and octahedral Mg sheets with hydrated Na{sup +} cations likely in the interlayer sites similar to trioctahedral micas (phyllosilicates). NMR studies verify the incorporation of Al in tetrahedral silicate sheets. XRD demonstrates the ability of these regions to nucleate and form zeolites (i.e., sodalite) as well as the formation of Mg-Al layered double hydroxide (LDH) phases (i.e., meixnerite), which is expected due to high concentrations of Mg and Al. TGA results indicate that M-(N)-A-S-H possesses chemically bound water and hydroxyl units similar to other Mg binders. These results evince the critical role of Mg to form unique atomic structures and durability-linked phases in low-calcium alkali-activated materials.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Use of kaolinite clays in development of a low carbon MgO-clay binder system

Magnesium oxide based cements may provide a promising alternative to the conventional Portland cement in many applications. This study investigates the feasibility of using calcined kaolinitic clay to produce an MgO binder. The MgO-based binder were prepared using a low kaolinite content clay and metakaolin and were compared with a silica fume system. Implications of the addition of magnesium carbonate in the binder were also investigated. Isothermal calorimetry, X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR) were used to study the hydration characteristics of the binder system whereas compressive strength and porosity were measured to determine mechanical and durability attributes. The economic and environmental aspects of the binder system is also discussed. Hydrotalcite like phases were clearly produced on hydration in the clay mixes containing carbonate additions. The compressive strength of clay mixes was at par or better compared to systems containing silica fume, and the clay systems had significantly lower porosity levels. The presence of magnesium carbonate further enhanced the physical properties of the clay mixes.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A parametric study of accelerated carbonation in alkali-activated slag

Resistance to carbonation is one important attribute that low-CO{sub 2} cement alternatives must possess, and is particularly crucial for cement alternatives subjected to aggressive CO{sub 2} concentrations such as those used in construction of oil wells and wells for below ground carbon sequestration. Here, a parametric study of alkali-activated slag (AAS) carbonation in aggressive environments has been conducted to examine (i) calcium carbonate polymorphism using X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy, and (ii) the extent of calcium carbonate formation and CO{sub 2} adsorption using thermogravimetric analysis (TGA). A range of AASs have been studied by varying the magnesium content of the slag, the activator type (sodium hydroxide and sodium silicate), the activator concentration, and the curing time prior to carbonation. It was uncovered that both (i) magnesium from the slag and (ii) silica from the activating solution are needed to reduce the propensity for the sodium-containing calcium-alumino-silicate-hydrate gel to undergo decalcification.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Mechanochemical formation of highly stable amorphous calcium carbonate in calcium silicates: Potential long-term storage of CO 2 in cement

Here, we have investigated mechanochemical reactions with the calcium silicate wollastonite to probe potential mechanisms of sequestration and long-term storage of CO 2 as mineral carbonates in cement pastes. Wollastonite, CaSiO 3 , was milled under ambient and 13 C enriched CO 2 atmospheres. Milling induced a structure change from monoclinic wollastonite-2M to triclinic-1T, consistent with high pressure treatment. The results from solid-state 13 C nuclear magnetic resonance (NMR) spectroscopy shows this process forms an extraordinarily stable amorphous calcium carbonate (ACC) phase that remains despite a high temperature dehydration treatment (130 °C) and persists in the same form after 3 yrs. of storage at ambient conditions. Thermogravimetric analysis (TGA) of these samples indicates that ACC is produced at the similar solid concentrations in both CO 2 -enriched and ambient atmospheres. The observation of meta-stable ACC due to wollastonite carbonation may play an important role in further exploration and optimization of mineral carbonation reactions for CO 2 capturing cement formulations.

13C solid-state NMR↗
DOE OSTI2020

UO 2 + 5 vol% ZrB 2 nano composite nuclear fuels with full boron retention and enhanced oxidation resistance

The boron isotope ( 10 B) can be used as a neutron absorber in UO 2 to control the reactivity of nuclear fuel pellets, however, the boron source can react with oxygen source in UO 2 to form B 2 O 3 that vaporize readily at temperatures above 1200 °C. Unfortunately, the sintering of UO 2 fuel requires hours holding at high temperature (>1700 °C), resulting in an inevitable B loss during sintering and unpredictable B concentration in final product. It is challenging to incorporate boron through a conventional sintering method. In this work, we demonstrated that spark plasma sintering (SPS), a field assisted sintering technology, can effectively densify UO 2 + 5 vol% ZrB 2 composite fuel pellets by rapid consolidation at 1600 °C for a short duration of 5 min under an applied pressure of 40 MPa. Further, thermogravimetric analysis (TGA) measurements confirm that ZrB 2 is fully retained inside the composite fuel pellets. Inside the composite fuel pellets, nano sized ZrB 2 particles are uniformly distributed along the grain boundaries of the UO 2 matrix. The ZrB 2 particle transforms to a glassy B 2 O 3 phase covering the sample surface and grain boundaries of UO 2 matrix after a simple post-sintering annealing at 1000 °C in flowing Argon gas for 4 h. The formed glassy B 2 O 3 slows down the diffusion of oxygen ions and postpones the onset temperature for oxidation of UO 2 from 400 °C to 550 °C. This study demonstrates the capability of SPS, an advanced fuel manufacturing technique, to achieve a full retention of ZrB 2 in UO 2 oxide fuel and increase oxidation resistance through a simple post-sintering annealing. The reported work holds great engineering potential for development of advanced oxide fuel for nuclear application.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Removable coatings: Thermal stability and decontamination of steel surfaces from 241 Am

This study presents a comparative analysis of several strippable materials for decontamination of steel surfaces from 241 Am. The strippable coatings were chosen to have a history of application, to be commercially available, easily handled and have different composition and formulation. Carbon steel and stainless steel surfaces (coupons) were utilized as the most representative industrial materials, and the experimental series were expanded to include the rusting treatment of these surfaces as it is common for decommissioned old nuclear facilities. The experiments followed the path of pre-screening of the strippable materials (easiness of application, peeling etc.), their characterization with Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA), decontamination factors (DF) or removal efficiencies for different types of steel surfaces, and enhancement of the removal efficiencies of the select strippable coatings via amendment with EDTA. As a result, DF and removal efficiencies for stainless steel (both pristine and with rusting treatment) are higher than for pristine carbon steel, and decontamination factors and removal efficiencies are higher for pristine than for rusted carbon steel across all the coatings. It is also shown that EDTA amendment can improve DF and removal efficiency for a strippable coating (i.e., CC Strip), however other factors should also be considered. Thus, the coating CC Strip exhibited easiness in handling and high DF (up to 97% when EDTA-amended), but its drying period was the longest among the rest of the materials and its thermal decomposition indicates on a risk of intense release of heat in case of a fire event.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Combustion in the ZrF 4 -Mg-Si and ZrF 4 -Al-Si systems for preparation of zirconium silicides

The exothermic reactions in the ZrF 4 –Mg-Si and ZrF 4 -Al-Si systems are investigated by a fast temperature recording (thermocouple) technique, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). A quenching method is used to arrest the combustion process and conduct a layer-by-layer analysis of the products by x-ray diffraction (XRD) and electron microscopy. Two seemingly similar reactive systems exhibited considerably different combustion characteristics, composition, and morphology. Based on these investigations, we propose and discuss phase formation mechanisms at the early stages for each system. Three different pathways involving the reaction of ZrF 4 with other reagents and the Mg 2 Si intermediate are identified to occur in the ZrF 4 –Mg-Si system. Contrary to the complex mechanism in the ZrF 4 –Mg-Si system, the early stage of the combustion process for the ZrF 4 -Al-Si system involves the interaction of ZrF 4 with Al-Si eutectic melt. The exothermic reaction between reduced solid Zr and Si melt is the primary heat-generating step for both systems in spite of substantial differences in the early stages of the reactions. The silicon content in the reactive mixtures governs the phase composition of products. The ZrSi 2 phase, with a high growth rate, forms first on the Zr particle surfaces and then grows by a reactive diffusion mechanism. The ZrSi 2+ Zr reaction produces silicon-lean phases (e.g., ZrSi) when the silicon supply is limited. The combustion temperature also has a considerable influence on the phase compositions of the products. High combustion temperature in the ZrF 4 +2Mg+Si mixture enables the formation of multiphase products (α-ZrSi and β-ZrSi), whereas the relatively lower temperatures in the 3ZrF 4 +4Al+3Si mixture yields a single-phase α-ZrSi. As a result, lower combustion temperatures also make the ZrF 4 -Al-Si system more advantageous for the preparation of zirconium silicides.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Biofuel production from palm oil deoxygenation using nickel-molybdenum on zirconia catalyst using glycerol as a hydrogen donor

The growing demand for renewable energy has generated interest in biofuels as alternatives to fossil fuels. Second-generation biofuels, derived from deoxygenating fats and oils, have garnered a higher level of interest from industry and academia due to their potential for direct replacement of diesel and jet fuels. Palm oil, mostly cultivated in Thailand and composed of C16 and C18 fatty acids, is a primary feedstock sought for biofuel production. Palm oil deoxygenation contains several pathways that may or may not require hydrogen gas. This study aimed to produce biofuels in different fuel ranges, such as gasoline, jet fuel, and diesel, through palm oil deoxygenation using glycerol as a hydrogen source. Glycerol, a low-value byproduct, was used as a hydrogen donor, whereas nickel-molybdenum-supported catalysts were chosen for their high efficiency in deoxygenation and cost-effectiveness. The study investigated the impact of reaction time, temperature, and catalyst activation method on palm oil deoxygenation. Catalyst characterization methods, including XRD, SEM, TEM, XPS, FTIR, TGA, and nitrogen-sorption, were employed to understand the role of catalysts’ activity during palm oil upgrading. Findings indicated that alkane hydrocarbons are the major components in liquid products. The presence of excess hydrogen in post reaction gaseous phase proves the hydrogen donation capability of glycerol. Increased reaction time and temperature facilitated the removal of oxygen from palm oil. Nickel-molybdenum on zirconia activated by sulfidation demonstrated higher stability than by reduction activation.

09 BIOMASS FUELS↗
DOE OSTI2022

Effects of temperature and time on supercritical methanol Co-Liquefaction of rice straw and linear low-density polyethylene wastes

We report that biofuels are particularly attractive and play an increasingly important role in sustainable energy. However, biofuels originating from lignocellulosic biomass (LCB) are extremely challenging because of their low carbon content, low stability, and high oxygen content. This work evaluates the supercritical methanol (scMeOH) co-liquefaction of rice straw and linear low-density polyethylene (LLDPE) at temperature range of 240-340 °C for 0-2 h, to obtain hydrocarbons (HCs)-rich oil and carbon-rich solid product. Results show that reaction temperature dominated the yield and properties of products, but not the holding time. Among parameters tested, 30.07 wt% oil yield with 75.79% HCs content and 33.05 wt% oil yield with 70.91% HCs content were obtained at 300 °C for 1 h and 1.5 h, respectively. Simultaneously, the remaining solid products were still as high as 53.85 wt% with a carbon content of 79.59% and 48.28 wt% with carbon content of 81.34% under 300 °C for 1 h and 1.5 h, respectively. Ultimate analysis, FT-IR, TGA, and SEM show that solid products could be used as sustainable carbon resources, and solid fuel rather than soil amendment because of risk of micro plastic or adsorbent due to smooth surface without pores.

09 BIOMASS FUELS↗
DOE OSTI2020

Hydrothermal liquefaction of Cyanidioschyzon merolae and Salicornia bigelovii Torr.: The interaction effect on product distribution and chemistry

Hydrothermal liquefaction (HTL) has proven to be a promising technology for processing wet biomass into valuable biofuel intermediates. We investigated the influence of HTL process parameters on the individual and co-liquefaction of Salicornia bigelovii Torr. (SL) and Cyanidioschyzon merolae (CM) biomass and their respective product properties and characteristics. SL and CM biomasses were subjected to HTL conditions of process temperatures (250–350 °C), 10 wt% solid loading, 30 min reaction time, and co-liquefaction ratios (80–20, 50–50, 20–80, CM-SL, respectively). The individual maximum HTL biocrude yields for CM (34.63 wt%) and SL (7.63 wt%) were obtained at 300 °C. In both cases, biocrude oils had a higher carbon and hydrogen content relative to those of the original biomass. The HHV (higher heating value) values for the biocrude samples ranged from 24.2 to 33.12 MJ/kg, which were significantly higher than those of the original biomasses. A positive synergistic effect was observed during the co-liquefaction of two biomasses, where the experimental yield of biocrude oil was higher than the theoretical value. During the co-liquefaction experiments, a maximum biocrude yield of 32.95 wt% was obtained at 300 °C and 80–20 CM-SL biomass mix ratio. Co-liquefaction led to an increase in the energy content of the co-liquefied biocrude oil and a higher energy recovery rate. Finally, the properties of HTL products and biomasses were determined with TGA, CHN elemental analyzer, GC/MS, bomb calorimeter, HACH Spectrophotometer, and ICP OES.

09 BIOMASS FUELS↗
DOE OSTI2020

Effect of Si/Al ratio of ZSM-5 support on structure and activity of Mo species in methane dehydroaromatization

The effect of the Si/Al ratio of the ZSM-5 support on the structure and activity of Mo/HZSM-5 catalysts in methane dehydroaromatization (MDA) was studied. ZSM-5 (with Si/Al = 15, 25, and 40) supported Mo oxide catalysts (MoOx/ZSM-5) with 3 and 10 wt% Mo loading were prepared by incipient wetness impregnation followed by calcination in air at 500 °C. The as-prepared catalysts were activated by temperature programmed reduction in hydrogen in order to maximize Mo dispersion. To understand the structure-activity relationship, the fresh and spent samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 adsorption isotherms, Scanning Transmission Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (STEM-EDS), X-ray absorption spectroscopy (EXAFS and XANES), thermogravimetric analysis (TGA), and Raman spectroscopy. The results show that the Si/Al ratio does not influence the the local structure around the Mo centers. It does however affect the number of available Brønsted acid sites in the support and the amount of Mo species entering the zeolite channels. A lower Si/Al ratio and higher Mo loading resulted in a higher Mo occupation within the zeolite channels. The higher channel occupation directly correlated with higher benzene selectivity and yield, as well as a lower catalyst deactivation rate.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Metastable solubility and local structure of amorphous calcium carbonate (ACC)

The properties of amorphous calcium carbonate provide the foundation for understanding mineralization of calcified skeletons but inconsistencies between studies suggest the physical picture is incomplete. This study quantifies the metastable solubility and structure of ACC produced under a series of chemical conditions. Using complementary in situ methods that quantify ACC structure (in situ PDF analysis) in parallel with chemical composition (TGA, ICP-OES), we find two short-range structures are produced that also show distinct morphological differences. Conditions with high carbonate ion concentrations stabilize a Ca-rich ACC with short-range order that is independent of Mg content. In contrast, low carbonate solutions favor Mg-rich ACC with mixed Ca- and Mg-short range order. Measurements of solubility product determined from supersaturated and undersaturated conditions find the distinctive structures are related to solution carbonate activity while solubility is primarily determined by the magnesium content of the solid. Bulk solubility is a composite that concurs with established values. The findings demonstrate the type of ACC that forms is tuned by Mg2+ and CO3-2- concentration and suggest ACC structure, not bulk composition, is a reliable indicator of intermediate phase. This chemical framework also provides a basis for interpreting apparent differences between observations of ACC in synthetic and natural systems that reconciles previous structural studies.

Mergelsberg, Sebastian T.↗
DOE OSTI2026

Triple oxygen and hydrogen stable isotope composition of hydroxyl water in Orgueil (CI-type) and Tagish Lake (C2-type) carbonaceous chondrites

The primitive carbonaceous chondrites are of interest to cosmochemical science because they contain relatively large amounts of ‘water’ (H 2 O and/or OH – ) within phyllosilicate minerals. This water is evidence for the accretion of ices by their parent planetesimals, and thus represents an archive of the isotopic compositions of H 2 O in the protoplanetary environments. Here, in this study, we used thermogravimetry-enabled laser spectroscopy (TGA-IRIS) analyses of the Orgueil and Tagish Lake meteorites to make δ 2 H, δ 18 O, and Δ′ 17 O measurements of the H 2 O and OH – contained in the different hydrous minerals that comprise each meteorite. In Orgueil, we measured mass-weighted averages of OH – in the saponite and serpentine phyllosilicate matrix to be δ 2 H = 192 ‰, δ 18 O = 1.5 ‰, which are unquestionably of extraterrestrial origin with Δ′ 17 O = 1.0 ‰. For Tagish Lake, analogous values of OH– in the saponite and serpentine phyllosilicate matrix are δ 2 H = 704 ‰, δ 18 O = 11.3 ‰, and are similarly unambiguously extraterrestrial with Δ′ 17 O = 0.82 ‰. We estimate that the parent H 2 O involved in aqueous alteration of Orgueil had δ 18 O value ≥ +23 ‰. In Orgueil, we interpret the phyllosilicate petrographic relationships, and the δ 18 O values of OH – in saponite and serpentine to indicate that saponite formed first, at a lower temperature by 35 to 53 °C than serpentine. This suggests that the Orgueil parent body experienced increasing temperature during the phase of active aqueous alteration (prograde) which set the δ 18 O OH values of the serpentine and saponite. In the case of Tagish Lake, serpentine formed at a lower temperature by 32 to 60 °C than saponite, for the simplest case with constant δ 18 O H2O values. If serpentine formed first, followed by saponite formation at 32 to 60 °C °C higher temperature, this suggests that Tagish Lake sample TL1 underwent prograde aqueous alteration as the parent body heated up. We find evidence that the parent H 2 O for Orgueil, Tagish Lake sample TL1, and Murchison (based on data from a previous study) may have had Δ′ 17 O values of >0.64 ‰.

Aqueous alteration↗
DOE OSTI2020

Synergistic enhancement of nanocellulose foam with dual in situ mineralization and crosslinking reaction

Cellulose nanocrystals (CNCs) foams have recently gained research interests because they are renewable, abundant, biodegradable and exhibit high surface area. However, the application of CNCs-based foams is still challenging, which is attributed to its lack of effective entanglements between the CNCs particles, thus lowering foam properties. In this study, a synergistic enhancement strategy was proposed, based on the in situ mineralization with hydroxyapatite (HAP) layer onto the CNCs surface, followed by a chemical crosslinking reaction. The physical and chemical structures of the composites were analyzed with SEM, STEM, XRD, FTIR, and TGA. By controlling the amount of coated HAP and the crosslinker, it is possible to manufacture a series of CNCs-based foams that are lightweight (50–75 mg/cm 3 ), highly porous (~90%) with high water absorption (>1300%) and outstanding mechanical strength properties (as high as 1.37 MPa). Moreover, our study further indicated that these CNCs/HAP materials could increase the proliferation of rat osteoblast cells. The method developed in this study presents a novel approach to design improved networked CNCs foam, which has the potential to be used in thermal-retardant material, wastewater treatment, tissue engineering, and personal care applications.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Investigation of methane and ethane pyrolysis with highly active and durable iron-alumina catalyst to produce hydrogen and valuable nano carbons: Continuous fluidized bed tests and reaction rate analysis

The goal of this research work was to evaluate a novel iron-alumina catalyst for methane and ethane pyrolysis with high conversion rates to H 2 with a long life time to address two major issues reported with previous catalysts. Fluidized bed tests demonstrated continuous hydrogen production while collecting carbon containing fines. During the 230 h fluid bed test the methane conversion rate to hydrogen at 700 °C remained above 80% for 160 h while creating valuable nano carbons. Similarly high catalyst lifetimes with high methane conversions have not been reported before. Ethane was more active than methane for pyrolysis with 100% conversion to H 2 . Transmission electron microscopy and Raman analysis of the carbon showed single and multiwall nanotubes and conglomerate nano-fibers. Ethane did not impact the allotrope of carbon formed. TGA was used to create a data array that was used for kinetic analysis and reaction model parametric regressions. Ethane had a higher rate of pyrolysis that was 2.3–2.8 times that of methane. Ethane pyrolysis was found to be more sensitive to temperature with a higher activation energy of 62 kJ/mol as compared to methane at 43 kJ/mol. The frequency factor, A i , was significantly higher for ethane at 0.73 [[kmol/m 3 -sec]/[N/m2] n ] compared to 0.03 for methane on the same basis. Both gases had a functional partial pressure order dependence of ~0.6 based on the regression analysis.

08 HYDROGEN↗