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At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Catalytic activities of two different morphological nano-MnO2 on the thermal decomposition of ammonium perchlorate

Highlights: • Nano-MnO{sub 2} was produced easily. • Nano-MnO{sub 2} can promote the decomposition of AP. • Sea-urchin nano-MnO{sub 2} is a superior catalyst. - Abstract: In order to investigate the catalytic activity of nano-MnO{sub 2} on the thermal decomposition of ammonium perchlorate, two different shapes of nano-MnO{sub 2} (sea-urchin and linear) were prepared by the hydrothermal method with MnSO{sub 4}·H{sub 2}O and Na{sub 2}S{sub 2}O{sub 8}, MnSO{sub 4}·H{sub 2}O and (NH{sub 4}){sub 2}S{sub 2}O{sub 8}, respectively. X-ray diffraction, scanning electron microscopy and the nitrogen adsorption/desorption analysis were used to characterize the structure of the nanocomposites. The sea-urchin nano-MnO{sub 2} possesses a greater specific surface area than the linear nano-MnO{sub 2}. The catalytic properties of nano-MnO{sub 2} on the thermal decomposition of ammonium perchlorate (AP) were demonstrated by differential scanning calorimeter (DSC). As show in the DSC carves, the addition of the sea-urchin nano-MnO{sub 2} got the thermal decomposition peak temperature of AP reduced much more than the addition of the linear nano-MnO{sub 2}, the low-temperature decomposition process even disappeared, and the high-temperature pyrolysis peak temperature decreased by 94.6 °C. All evidences indicated that the sea-urchin nano-MnO{sub 2} is a better catalytic than the linear one.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Cost-effective fabrication of (g-C3N4 + Mo) added photostable ZnO thin films for enhanced visible light responsive photocatalytic dye degradation

Highlights: • First report on ZnO:Mo/GCN films prepared by simple cost-effective jet nebulizer spray method for dye degradation. • A remarkable enhancement in the photocatalytic dye degradation efficiency is achieved for ZnO. • The mechanism for the enhanced degradation is explained on the basis of the obtained point of zero charge values. • Optical, PL, SEM and XPS studies support the discussion on the photocatalytic property of ZnO:Mo/GCN. - Abstract: The photocatalytic activity of ZnO:Mo/GCN (ZnO:Molybdenum/g-C{sub 3}N{sub 4}) thin films deposited using a simple cost-effective jet nebulizer spray pyrolysis technique with different Mo doping concentrations (1,2 and 3 at.%) was studied. The photocatalytic degradation test was carried out against Methylene blue (MB) and Rhodamine B (RhB) dyes under visible light. It is found that thin film of ZnO:Mo/GCN with 1 at.% of Mo exhibits superior photocatalytic efficiency compared with the other samples. The degradation rate constant of this sample is 0.0727 and 0.0268 min{sup −1} for the tested MB and RhB dyes, respectively which are nearly two times and four times greater than the respective rate constant values of pristine ZnO. The mechanism involved in the enhanced photocatalytic activity is addressed with the help of obtained results. The properties of the deposited samples are correlated appropriately with the photocatalytic efficiency of the samples. The photostability of the prepared catalysts is tested experimentally.

36 MATERIALS SCIENCE↗
DOE OSTI2018

A facile and low-cost synthesis of MnOx/Mn2NNC nanohybrid as an advanced oxygen reduction electrocatalyst

Highlights: • We demonstrate a facile route to fabricate a novel MnO{sub x}/Mn{sub 2}NNC hybrid. • MnO{sub x}/Mn{sub 2}NNC displays an excellent ORR activity. • MnO{sub x}/Mn{sub 2}NNC affords overwhelmingly better durability than 20 wt% Pt/C. - Abstract: We demonstrate a one-step, low-cost and easily scalable pyrolysis route to fabricate a novel MnO{sub x}/Mn{sub 2}NNC nanohybrid with MnO{sub x}/Mn{sub 2}N nanoparticles (20–30 nm) anchored on the wrinkled N-doped carbon nanosheets (denoted as NC). MnO{sub x}/Mn{sub 2}NNC displays a remarkably higher ORR activity than that of NC, suggesting that the MnO{sub x}/Mn{sub 2}N nanoparticles play an important role in enhancing the ORR activity. Furthermore, MnO{sub x}/Mn{sub 2}NNC exhibits overwhelmingly better durability than commercial 20 wt% Pt/C, to be specific, 93.7% current retention after continuous operation for 24,000 s, while 59.7% for 20 wt% Pt/C.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Nitrogen-doped hollow carbon nanospheres for highly sensitive electrochemical sensing of nitrobenzene

Highlights: • NHCPs were prepared using MSM as a template and PDA as carbon and nitrogen precursor. • NHCPs-750 with high content of pyrindinic N showed good electrocatalytic performance. • A sensitive electrochemical sensor for NB was developed based on the NHCPs-750–GCE. - Abstract: Following hard template method, nitrogen–doped hollow carbon nanospheres (NHCPs) were successfully prepared by using monodisperse silica microspheres as a template and dopamine as carbon and nitrogen precursor. A series of NHCPs-x samples with different pyrolysis temperatures were reported. The composite material formation was characterized by detailed methods (e.g., X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy). Results indicated that NHCPs treated at 750 °C with highest amounts of pyrindinic N showed improved electro-catalytic activity for nitrobenzene (NB) in neutral solution. NHCPs-750 can be developed as an effective sensing platform for the detection of NB, which showed high activity and superior analytical performance, such as a wide linear range of 5–2610 μM, a high sensitivity of 436 μAmM{sup −1}, and a low limit of detection of 2.29 μM.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Enhanced rate performance of Li3V2(PO4)3/C cathode by an improved rheological phase assisted microwave method

Highlights: • Rheological phase assisted microwave can utilize both advantages of two methods. • Polyethylene glycol was used as both rheological medium and carbon precursor. • 101.8 mA h g{sup −1} of specific capacity was obtained at 50 C rates. - Abstract: In this study, high-rate Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite is successfully synthesized via an improved rheological phase assisted microwave method using polyethylene glycol as both rheological medium and carbon precursor. The relatively uniform Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} particles are encapsulated in amorphous carbon architecture to form core-shell structure, providing effective electron and ion transport. When used as a cathode material in lithium ion battery, the Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}/C composite displays a maximum discharge capacity of 101.8 mA h g{sup −1} at 50 C charge/discharge rate and still possesses 98.3% of capacity retention after 100 cycles, demonstrating superior rate capability and excellent cycling stability when compared with bare Li{sub 3}V{sub 2}(PO{sub 4}){sub 3}. The observed electrochemical performance could be attributed to uniform coated-carbon pyrolysis from polyethylene glycol rheological phase precursor and small Li{sub 3}V{sub 2}(PO{sub 4}){sub 3} pristine particles synthesized by the fast microwave heating route.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Flame-made TiO2(B)

Highlights: • Flame-made titania can contain up to 27% TiO{sub 2}(B). • TiO{sub 2}(B) is present due to quenching. • The fraction of TiO{sub 2}(B) depends on residence time at high temperature. • Flame-made titania containing TiO{sub 2}(B) photocure epoxy more efficiently than P25. - Abstract: Titania nanoparticles containing both monoclinic (TiO{sub 2}(B) – a promising battery material and catalyst) and anatase crystal phases are synthesized with a low-cost, scalable flame spray pyrolysis (FSP) process, as confirmed by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. The latter reveals TiO{sub 2}(B) contents of up to 27% in the crystalline phase fraction. The amount of TiO{sub 2}(B) increases as the time for nanoparticle growth in the flame decreases through quenching with ambient air. It can be controlled by varying the flow rates of precursor solution and dispersion oxygen into the flame. The FSP-made titania outperforms commercial titania P25 in the photocuring of epoxy, indicating its potential as a photocatalyst.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Aromaticity and degree of aromatic condensation of char

The aromatic carbon structure is a defining property of chars and is often expressed with the help of two concepts: (i) aromaticity and (ii) degree of aromatic condensation. The varying extent of these two features is assumed to largely determine the relatively high persistence of charred material in the environment and is thus of interest for, e.g., biochar characterization or carbon cycle studies. Consequently, a variety of methods has been used to assess the aromatic structure of chars, which has led to interesting insights but has complicated the comparison of data acquired with different methods. We therefore used a suite of seven methods (elemental analysis, MIR spectroscopy, NEXAFS spectroscopy, 13 C NMR spectroscopy, BPCA analysis, lipid analysis and helium pycnometry) and compared 13 measurements from them using a diverse sample set of 38 laboratory chars. Here, our results demonstrate that most of the measurements could be categorized either into those which assess aromaticity or those which assess the degree of aromatic condensation. A variety of measurements, including relatively inexpensive and simple ones, reproducibly captured the two aromatic features in question, and data from different methods could therefore be compared. Moreover, general patterns between the two aromatic features and the pyrolysis conditions were revealed, supporting reconstruction of the highest heat treatment temperature (HTT) of char.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Quantitative analysis of changes in antioxidant in crosslinked polyethylene (XLPE) cable insulation material exposed to heat and gamma radiation

Quantitative analysis of the antioxidant poly(1,2-dihydro-2,2,4-trimethylquinoline) (pTMQ) was conducted on pristine, thermally-aged, and gamma radiation-aged commercial cross-linked polyethylene-(XLPE-)based cable insulation material aged at temperatures 60, 90, and 115?°C, with gamma radiation exposure dose rates of 0, 120, 300, and 540?Gy/h for 15 days. The quantification of antioxidant was performed using pyrolysis gas chromatography-mass spectrometry (Py-GCMS). Oxidation induction time (OIT) was measured using differential scanning calorimetry (DSC) and correlation was made between the quantified depletion of antioxidant and measured OIT. It was observed that, in the case of isothermal aging, the quantity of antioxidant and OIT decreased with increasing gamma radiation dose. In the case of samples exposed to the same gamma radiation dose, the quantity of antioxidant and OIT were observed to decrease with increasing aging temperature. Depletion in the quantity of antioxidant relative to that in the pristine material ranged from 7 to 93% for differently aged samples. The measured decline in OIT ranged from 0 to 80%. Change in the quantity of antioxidant in the material was observed to follow the same trend as the change in OIT when the samples were aged under various conditions. The observations are explained in terms of the reaction between the antioxidant and free radicals created during exposure of the samples to thermal and gamma radiation.

Pyrolysis gas chromatography-mass spectroscopy, an↗
DOE OSTI2026

Impact of DMP-30 catalyst concentration on the degradation and kinetics of bisphenol A epoxy thermosets cured with linear amine hardener

Epoxy thermosets are a crucial component in carbon-fiber composites, serving as the organic binding matrix. Catalysts are commonly used in prepolymer formulations to accelerate curing of the thermosets. However, the impact of catalysts on the thermal stability, degradation pathways, and kinetics of the final thermoset is poorly understood. Here, in this work, Product-Specific Kinetics (PSK) analysis was utilized with isoconversional kinetics to provide a first look into the degradation kinetics of major pyrolysis pathways in bisphenol A (BPA) epoxy resins and determine the impact of altering catalysis concentrations on these kinetic pathways. Results revealed new insights into previously identified degradation pathways, provided evidence of multiple degradation pathways for some products, and showed that use of excess catalyst results in polymer network alterations and reduced thermal stability of the thermosets.

Bisphenol A↗
DOE OSTI2018

Electrosorption of organic acids from aqueous bio-oil and conversion into hydrogen via microbial electrolysis cells

Neutralization of the bio-oil pH has been shown to generate a neutralized bio-oil aqueous phase (NBOAP) that includes most of the acidic components and a neutralized bio-oil organic phase (NBOOP) that includes hydrophobic organics, such as phenols. NBOOP can be used for fuel production, while NBOAP can be fed to microbial electrolysis cells (MECs) for hydrogen production. After pH neutralization, some organic acidic components remain in NBOOP. This work is focused on capturing acidic compounds from NBOOP through water extraction and electrosorption, and demonstrating hydrogen production via MECs. Capacitive deionization (CDI) is proven effective in capturing ions from NBOOP-contacted water and NBOAP via electrosorption. Captured acidic compounds enable the MEC application to effectively produce renewable hydrogen. Chemical oxygen demand (COD) removal of 49.2%, 61.5%, and 60.8% for 2, 4, and 10 g/L-anode/day loading were observed, corresponding to a total COD degradation of 0.19 g/L, 0.79 g/L, and 1.3 g/L, respectively. A maximum hydrogen productivity of 4.3 L-H 2 /L-anode/day was obtained. Major compounds in the water phase such as fatty acids, sugar derivatives, furanic and phenolic compounds were converted to hydrogen with an efficiency of 80–90%. Lastly, this approach may lead the entire biomass pyrolysis process to be an overall carbon-neutral process.

09 BIOMASS FUELS↗
DOE OSTI2026

Artificial intelligence-driven municipal solid waste sortation and its significance on downstream waste valorization in the United States: Techno-economic and life cycle assessment

Municipal solid waste (MSW) generation is quickly increasing due to population growth, industrialization, and urbanization. Current sorting technologies, e.g., optical sorters have low sortation efficiency and produce contaminated sorted materials unsuitable for downstream valorization. This study evaluates a novel artificial neural network (ANN)-based MSW sortation system through sorting efficiencies, economic performance, and environmental impacts. ANN system can sort up to 8 plastic types and all organic waste (i.e., food, yard, and paper waste) with 99% and 93% recovery efficiency, respectively, compared to optical sortation which could separate only polyvinyl chloride (PVC) plastic ultimately producing mixed plastics (except PVC) and organics streams as products. Nonetheless, their sortation costs are similar, $28.7 for ANN-based sortation and $28 for optical sortation per metric ton (Mt) of MSW at processing capacity of 94,860 metric tons (Mt)/yr of MSW in the United States. Additionally, ANN system produced high purity feedstocks for downstream valorization. A biochar pyrolysis plant modeled to process 3.6 and 14 Mt/h of sorted yard waste outperformed biochar production from mixed organic fraction (MOF), achieving 8% lower production cost and 34% lower global warming impact (1.37 kg CO 2 eq. per kg) compared to biochar derived from mixed organic feedstock (2.08 kg CO 2 eq.).

09 BIOMASS FUELS↗
DOE OSTI2016

Impact of feedstock quality and variation on biochemical and thermochemical conversion

The production of biofuels from lignocellulosic feedstock is attracting considerable attention in the United States and globally as a strategy to diversify energy resources, spur regional economic development and reduce greenhouse gas emissions. Because of the wide variation in feedstock types, compositions and content of convertible organics, there is a growing need to better understand correlations among feedstock quality attributes and conversion performance. Knowledge of the feedstock impact on conversion is essential to supply quality controlled, uniform and on-spec feedstocks to biorefineries. This review paper informs the development of meaningful feedstock quality specifications for different conversion processes. Discussions are focused on how compositional properties of feedstocks affect various unit operations in biochemical conversion processes, fast pyrolysis and hydrothermal liquefaction. In addition, future perspectives are discussed that focus on the challenges and prospects of addressing compositionally intrinsic inhibitors through feedstock preprocessing at regionally distributed depots. As a result, such preprocessing depots may allow for the commoditization of lignocellulosic feedstock and realization of stable, cost-effective and quality controlled biomass supply systems.

09 BIOMASS FUELS↗
DOE OSTI2017

The influence of catalysts on biofuel life cycle analysis (LCA)

Catalysts play an important role in biofuel production but are rarely included in biofuel life cycle analysis (LCA). In this work, we estimate the cradle-to-gate energy consumption and greenhouse gas (GHG) emissions of Pt/γ-Al 2 O 3 , CoMo/γ-Al 2 O 3 , and ZSM-5, catalysts that could be used in processes to convert biomass to biofuels. We also consider the potential impacts of catalyst recovery and recycling. Integrating the energy and environmental impacts of CoMo/γ-Al 2 O 3 and ZSM-5 into an LCA of renewable gasoline produced via in-situ and ex-situ fast pyrolysis of a blended woody feedstock revealed that the ZSM-5, with cradle-to-gate GHG emissions of 7.7 kg CO 2 e/kg, could influence net life-cycle GHG emissions of the renewable gasoline (1.7 gCO 2 e/MJ for the in-situ process, 1.2 gCO 2 e/MJ for the ex-situ process) by up to 14% depending on the loading rate. CoMo/γ-Al 2 O 3 had a greater GHG intensity (9.6 kg CO 2 e/kg) than ZSM-5, however, it contributed approximately only 1% to the life-cycle GHG emissions of the renewable gasoline because of the small amount of this catalyst needed per kg of biofuel produced. As a result, given that catalysts can contribute significantly to biofuel life-cycle GHG emissions depending on the GHG intensity of their production and their consumption rates, biofuel LCAs should consider the potential influence of catalysts on LCA results.

09 BIOMASS FUELS↗
DOE OSTI2018

Charcoal from anaerobically digested dairy fiber for removal of hydrogen sulfide within biogas

Highlights: • Anaerobically digested (AD) fiber was used for charcoal production via pyrolysis. • Charcoal from AD fiber can effectively adsorb H{sub 2}S from biogas. • Impregnation of charcoal from AD fiber with Na{sub 2}CO{sub 3} increases H{sub 2}S sorption capacity. • Ash in the AD fiber helps the retention of S on the surfaces of the char. • Charcoal manufacture is a promising approach to use abundant AD fiber. - Abstract: Anaerobically digested fibrous solid (AD fiber) is an abundant material that offers potential to produce value-added products such as biochar. The objective of this paper is to better understand how thermochemical processing conditions affect the capacity of biochars derived from AD fiber to adsorb H{sub 2}S from biogas. AD fiber was pyrolyzed in an electric tube reactor at temperatures up to 600 °C and 60 min. The chars were employed for H{sub 2}S scrubbing tests from a synthetic biogas. Results showed that the chars’ capacity for H{sub 2}S removal is comparable to that of activated carbon. An additional step consisting of impregnation of the chars with Na{sub 2}CO{sub 3} resulted in an improved capacity for H{sub 2}S removal. To study the effect of ash, the AD fiber was also subjected to an alternative thermal treatment, hot water extraction (HWE), at 200 °C for 60 min. The resulting HWE material showed no removal of H{sub 2}S from biogas, indicating that the ash and the environment employed for the thermal treatment of AD fiber play an important role in the char’s performance for H{sub 2}S removal. Results also suggest that a portion of the S in the charcoal after the H{sub 2}S sorption process exists as free or adsorbed S (i.e., not chemically bonded to the charcoal).

09 BIOMASS FUELS↗
DOE OSTI2021

Current Status on the Manufacturing of Nanomaterials for Proton Exchange Membrane Energy Systems by Vapor-Based Processes

Development of novel technologies for catalyst synthesis and membrane electrode assembly (MEA) fabrication is of primary importance for further improvement of the performance and economics of proton exchange membrane fuel cells (PEMFCs) and proton exchange membrane water electrolyzers (PEMWEs). While the traditional manufacturing methods are time-consuming, energy intensive, and require many processing steps, the new vapor-based methods provide many benefits including the development of improved catalysts and catalyst supports, deposition of uniform thin films, reduction of catalyst loading, and minimizing the number of manufacturing steps. Recent publications in the field identified spray pyrolysis, reactive spray deposition technology, chemical vapor deposition, and atomic layer deposition as advanced vapor-based catalyst synthesis and deposition methods used for fabrication of MEAs for PEMFCs and PEMWEs. Here, the MEAs fabricated via vapor-based processes have shown significant performance improvements in comparison to the state-of-the-art MEAs, which are attributed to better catalyst distribution, improved catalyst supports, and controlled, uniform catalyst layer microstructures. This review provides an overview of the vapor-based synthesis and deposition methods currently being used for the development of PEM-based devices. The advantages and disadvantages of these methods are critically compared and discussed while the outlook for future development is provided.

25 ENERGY STORAGE↗
DOE OSTI2021

Corrosion of Ferrous Structural Alloys in Biomass Derived Fuels and Organic Acids

This work investigated the corrosivity of biomass-derived liquid fuels and organic acids associated with bio-oils and conducted a corrosion compatibility evaluation of several structural ferrous alloys in the fuels and acids. Here, the acidity parameters and solution conductivity values were higher in raw pyrolysis bio-oils than postprocessed oils with significant corrosion attack for carbon steel and Fe-2.25Cr-1Mo. However, higher-grade stainless steels, ferritic Fe-15Cr (15Cb) and austenitic types 304L and 316L, showed negligible corrosion loss, whereas lower-Cr ferritic grades 409, 410, and 416 were attacked. Metal leaching tests and electrochemical impedance spectroscopy measurements revealed superior corrosion resistance of 316 over 410 stainless steels in solutions of formic and oxalic acids that can be present in bio-oils. The corrosion evaluation methods utilized in this work provide effective screening tools to identify the compatible structural alloys for bio-oils.

09 BIOMASS FUELS↗
DOE OSTI2023

Theoretical Insights on the Fragmentation of Cellulosic Oligomers to Form Hydroxyacetone and Hydroxyacetaldehyde

The presence of heavy unknown oligomeric sugar products in bio-oil is evidenced in experimental results reported in the literature. In this paper, we study the fragmentation reactions yielding acetol and glycolaldehyde from oligomeric sugars following previous work on dehydration reactions to propose structures of these oligomers. Acetol and glycolaldehyde are primary products of cellulose fast pyrolysis but the fragmentation reaction mechanism of these compounds from oligomers merits further study. The density functional theory (DFT) approach was employed to study this reaction. Results revealed that acetol and glycolaldehyde fragments are favorably removed from the non-reducing end based on their thermodynamic stabilities. Theoretical FTIR and NMR spectra were calculated to aid in understanding the structures of the oligomeric sugars. Also, the thermodynamics and physical properties of these compounds were estimated using the Group Contribution Method (GCM). In conclusion, these properties are essential in the design of processing technologies and the upgrading of products.

10 SYNTHETIC FUELS↗
DOE OSTI2017

Adsorption Characteristics of Coals Pyrolyzed at Slow Heating Rates

Underground coal pyrolysis is a process similar to in situ oil shale production wherein heat is applied to deep coal formations to produce light hydrocarbons. Like enhanced coal bed methane, the injection of CO 2 post thermal treatment can improve hydrocarbon recovery and serves as a means of carbon sequestration. Little information exists pertaining to coals pyrolyzed to temperatures expected with this process. This work examines the development of meso- and micropores and their influence on methane and carbon dioxide adsorption and permeability on a thermally treated Utah bituminous coal. Residual tars were found to affect the pore size distributions in pyrolyzed coals. Generally, with increasing treatment temperature, there are more meso- and micropores. A correlation was established between the prevalence of mesopores in pyrolyzed coals and adsorption and, to a lesser extent, permeability. Finally, the treatment temperature of this particular coal is directly related to the amount of CO 2 said coal can store and how the plume of injected CO 2 moves through the formation.

01 COAL, LIGNITE, AND PEAT↗