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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Catalytic degradation of waste rubbers and plastics over zeolites to produce aromatic hydrocarbons

Catalytic conversion of waste rubbers and plastics into aromatic hydrocarbons is a promising approach to waste management and energy recovery. In the present study, acidic HY zeolites were supported by cobalt, iron, and zirconium, and the catalysts were characterized by powder X-ray diffraction, nitrogen adsorption-desorption, ammonia temperature programmed desorption, X-ray photoelectron spectroscopy, and pyridine-Fourier transform infrared spectroscopy. Here, the catalytic degradation of waste polybutadiene rubbers (BR) was conducted to investigate the degradation mechanism and evaluate the catalytic activity of supported zeolites. Experimental results indicated that HY loaded by zirconium and iron led to a higher content of Lewis acid sites as opposed to cobalt supported one. Compared with the non-catalytic pyrolysis of BR, the zirconium supported HY (Zr/HY) led to a 10-fold increase in aromatic hydrocarbons production with a distinctively high selectivity of 97.9%. A series of waste polymers including waste tires (WT), polyethylene (PE), polycarbonate (PC), and BR, were subjected to catalytic pyrolysis to explore the effects of polymer type on aromatic hydrocarbons generation, and BR was the most effective substrate, with yield enhancement reaching 2.4 over Zr/HY. Catalytic co-pyrolysis of waste rubbers and plastics was conducted to probe the effect of polymer structure on aromatic hydrocarbons formation, where a significant synergistic effect was observed in the PE co-fed with PC run.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Removal of Antibiotics from Swine Wastewater Using an Environmentally Friendly Biochar: Performance and Mechanisms

Antibiotics used in the swine industry to treat diseases and improve animal growth are poorly absorbed by swine and have been classified as micropollutants due to their occurrence in surface water, wastewater, and soil. This study investigated the capacity of biochar produced from eastern red cedar to remove target antibiotics that have been extensively used in the swine industry. Biochar was produced by pyrolysis from eastern red cedar at 450 °C. The sorption tests were performed by mixing biochar and a solution (1:10 ratio) containing each antibiotic in 100, 300, 600, and 900 μg L –1 concentrations. The results indicate that red cedar biochar was able to effectively remove up to 99.93% tetracycline, 96.23% oxytetracycline, 98.28% chlortetracycline, 76.4% sulfadiazine, and 78.6% sulfamethazine at the lowest concentrations. The removal efficiencies at higher concentrations declined up to 83.52, 47.23, 64.16, 69.8, and 58.4% for tetracycline, oxytetracycline, chlortetracycline, sulfadiazine, and sulfamethazine, respectively. The biochar exhibited stronger adsorption capacity for chlortetracycline and sulfamethazine compared to the other antibiotics. The likely adsorption mechanisms driving the removal of tetracyclines and sulfonamides are hydrogen-bonding and π–π electron-donor–acceptor, supported by FTIR analyses of the biochar itself. Overall, the results highlighted the potential utilization of eastern red cedar biochar for practical applications, mitigating antibiotic residues from swine wastewater in a cost-effective and environmentally friendly manner due to its relatively low pyrolysis temperature (450 °C) and sustainable repurposing of an invasive tree species.

09 BIOMASS FUELS↗
DOE OSTI2025

Theoretical and kinetic modeling study of H 2 S pyrolysis

Hydrogen sulfide pyrolysis was investigated theoretically and through chemical kinetic modeling. Reactions on the SHH potential energy surface, primarily S + H 2 (+Ar) ⇌ H 2 S (+ Ar) (R1) and S + H 2 ⇌ SH + H (R6b) were characterized by ab initio calculations. Results for k 1 were in good agreement with experiment, but deviated strongly below 2000 K from values previously used in modeling. Collider efficiencies for H 2 S, S 2 , and N 2 compared to Ar were calculated for R1. Hydrogen sulfide decomposition experiments reported in literature were re-examined in terms of an updated detailed chemical kinetic model. Concentration profiles for the atomic S at high temperature in shock tubes supported the present value of k 1 and served to constrain the rate constants for reaction of S with SH and H 2 S. To explain results from batch and flow reactors, conducted at high H 2 S concentrations in the 900–1400 K range, a very fast rate constant was required for HSS + H ⇌ SH + SH. Under dilute conditions, the gas-phase chemistry was too slow to compete and the decomposition of H 2 S was controlled by loss on the reactor surface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Quantifying Impacts of Biomass Pelletization on Fast Pyrolysis Using a Single-Particle Reactor, X-ray Computed Tomography, and Computational Modeling

The pore structure and density of lignocellulosic feedstocks dictate intraparticle transport phenomena and thereby play an important role in thermochemical conversion processes such as fast pyrolysis for biofuel and biochemical production. Variations in microstructure are inherent from different biomass species and can be introduced by preprocessing techniques such as cutting and pelletization. Morphological changes also occur during conversion and lead to vastly different pore structures and behavior during pyrolysis, which impact required conversion times and product distributions. The current work presents a comprehensive comparison of fast pyrolysis of neat and pelletized pine feedstocks, which includes single-particle experiments, modeling, and 3D imaging by X-ray computed tomography (XCT). The particle-scale model included anisotropic heat and mass transport in a shrinking particle with pyrolysis reactions based on the CRECK mechanism with boundary conditions informed by reactor-scale simulations of the single-particle reactor. The models were validated by measurements of the temperature and mass loss from single-particle pyrolysis experiments of neat and pelletized pine. Quantitative analysis of XCT geometries revealed that pyrolytic conversion yielded chars with increased porosity and permeability compared to the unpyrolyzed materials, along with decreased tortuosity and anisotropy. Pelletization of the pine feedstock resulted in a much denser, less permeable material, which converted slower and produced more residual char after pyrolysis compared to neat pine. The results from particle modeling revealed that accounting for the dynamic and anisotropic heat and mass transport caused by differences in pore structure is critical to achieving agreement with experimental results. Overall, this study highlights the dramatic differences in conversion behavior imparted by pelletization and the importance of capturing microstructural attributes in computational models to guide the design and optimization of pyrolysis processes for specific biomass feedstocks.

09 BIOMASS FUELS↗
DOE OSTI2022

Molecular weight growth by the phenyl + cyclopentadienyl reaction: Well-skipping, ring-opening, and dissociation

Radical-radical reactions contribute to molecular weight growth of polycyclic aromatic hydrocarbons (PAHs), but their role is not well understood. The phenyl (Ph, C 6 H 5 ) + cyclopentadienyl (C 5 H 5 ) reaction has not been studied but can serve as a surrogate reaction for many reactions of larger aryl-σ radicals with resonance-stabilized π-radicals. The adducts of these reactions easily lose an H atom to produce a new π-radical. Here, through a combination of dilute flash pyrolysis experiments, theory, and simulation, we find that for the title reaction, substantial Ph—C 5 H 4 + H is formed, dominantly by a well-skipping pathway, at conditions around 30 Torr and 1400 K. This radical is thermally stable at moderate temperatures but decomposes at higher temperatures following ring opening of the 5-member ring. Products corresponding to the loss of H, C 2 H 2 , and C 3 H 3 are observed experimentally. Calculation of the C 11 H 9 potential energy surface affirms that these are expected decomposition products and reveals multiple possible pathways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Efficient kinetic thermal inverse modeling for organic material decomposition

The prevalent use of organic materials in manufacturing is a fire safety concern, and motivates the need for predictive thermal decomposition models. A critical component of predictive modeling is numerical inference of kinetic parameters from bench scale data. Currently, an active area of computational pyrolysis research focuses on identifying efficient, robust methods for optimization. This paper demonstrates that kinetic parameter calibration problems can successfully be solved using classical gradient-based optimization. We explore calibration examples that exhibit characteristics of concern: high nonlinearity, high dimensionality, complicated schemes, overlapping reactions, noisy data, and poor initial guesses. The examples demonstrate that a simple, non-invasive change to the problem formulation can simultaneously avoid local minima, avoid computation of derivative matrices, achieve a computational efficiency speedup of 10x, and make optimization robust to perturbations of parameter components. Techniques from the mathematical optimization and inverse problem communities are employed. By re-examining gradient-based algorithms, we highlight opportunities to develop kinetic parameter calibration methods that should outperform current methods.

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

Reactions of Propyl Radicals: A Shock Tube - VUV Photoionization Mass Spectrometry Study

The pyrolytic reactions of n-propyl and i-propyl radicals and their precursors have been investigated at elevated temperatures and pressures (600 – 900 K and 5 – 8 bar). The studies were performed in a miniature high repetition rate shock tube with synchrotron vacuum ultraviolet photoionization mass spectrometry yielding comprehensive datasets of temporal and photoionization energy dependencies of reagents and products. The propyl radicals were generated by pyrolysis of alkyl nitrites. In addition to the main decomposition path, NO elimination, the mass spectra allowed an alternative minor path via HNO elimination to be identified and quantified. For the n-propyl precursor the HNO elimination route accounted for 9% of the alkyl nitrite while for the i-propyl precursor it was 2.5%. These values are in good agreement with a recent study on i-butyl radicals in the same apparatus at similar conditions. The ratio of disproportionation/recombination was obtained for n- propyl from the relative concentrations of n-hexane and propene and for i-propyl from 2,3-dimethyl butane and propene. For n-propyl the ratio is 0.3 and 1.2 for i-propyl, both are independent of temperature and pressure over the experimental range. The disproportionation/recombination ratios are about a factor of 2 higher than prior evaluations that are based mainly on room temperature data. The experimental results are some of the first from the apparatus used and comments are made about the technique, challenges encountered, and suggestions for future developments.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Circular plastics technologies: pyrolysis of plastics to fuels and chemicals

Pyrolysis technologies are a staple in plastic chemical recycling because of the robustness to contamination and existing infrastructure. Pyrolysis is already considered to be a reasonably mature technology with numerous pilot plants operating to pyrolyze plastic waste into fuels and chemicals. Here this chapter will describe the pyrolysis process and important process parameters, the types of plastics that are suitable for pyrolysis recycling, the mechanism of pyrolytic degradation of various plastics, the products derived from different plastics, companies that have successfully scaled pyrolysis recycling, and recent innovations in the technology.

09 BIOMASS FUELS↗
DOE OSTI2022

Model quantification of the effect of coproducts and refinery co-hydrotreating on the economics and greenhouse gas emissions of a conceptual biomass catalytic fast pyrolysis process

Here we present model results for a scaled-up conceptual process informed by bench scale biomass catalytic fast pyrolysis (CFP) and hydrotreating experimental data. This process uses a Pt/TiO 2 catalyst during CFP, which produces a partially deoxygenated organic biocrude intermediate that is then hydroprocessed to a hydrocarbon fuel blendstock; the catalyst also enables high yields of acetone and methyl-ethyl-ketone (MEK) coproducts. Two options for hydroprocessing were modeled: (A) co-hydrotreating at a petroleum refinery using hydrogen sourced from steam reforming of natural gas and (B) standalone hydrotreating at a biorefinery using hydrogen sourced from CFP off gases. The results revealed that Case A was economically advantageous with a modeled minimum fuel selling price (MFSP) of $\$$2.83/GGE or gallon gasoline equivalent (in 2016 US dollars), while the additional cost of standalone hydrotreating facilities in Case B increased the MFSP to $3.13/GGE. Conversely, greenhouse gas (GHG) emissions were lower for Case B (3.9 g CO 2 e/MJ) compared to Case A (21.5 g CO 2 e/MJ) due to the use of biogenic (Case B) and fossil-derived (Case A) hydrogen. In a third option (Case C), the requirements for separation and purification of acetone and MEK were removed from the refinery co-processing scenario (Case A) to evaluate the impacts of this process simplification. Elimination of these coproducts increased the MFSP to $3.21/GGE and GHG emissions to 35 g CO 2 e/MJ. These comparisons based on our detailed conceptual models provide economic and sustainability guidance regarding processing choices for future biorefineries. While refinery coprocessing using existing equipment and the production of relatively valuable coproducts can benefit the economics, the hydrogen-source and biogenic coproducts can have significant impacts on the sustainability of the process, and feasibility to use CFP off-gases or other renewable sources for hydrogen production can help lower GHG emissions.

09 BIOMASS FUELS↗
DOE OSTI2025

Selective electrified polyethylene upcycling by pore-modulated pyrolysis

Plastic waste is a increasing problem, accumulating in landfills and the environment. Pyrolysis is a promising and industrially relevant approach for transforming plastic waste into value-added chemicals. However, the selectivity and yield of traditional plastic pyrolysis are poor, with products featuring broad molar mass distributions. Here we report a highly selective, energy-efficient and catalyst-free pyrolysis method that can upcycle plastic into value-added chemicals via pore-modulated pyrolysis. Using a Joule-heated carbon column, we demonstrate the pivotal role of the reactor’s graded porous structure in decreasing the polydispersity of the reaction intermediates, enabling high product selectivity and yield. The decreasing pore size of the reactor modulates the mass transport in an apparent gating effect—preventing high-molar-mass species from exiting the reactor before sufficient pyrolysis has occurred. Using polyethylene as a model reactant, we demonstrate a high yield of 65.9 ± 5.2% and up to 80.8% selectivity toward value-added aviation fuel precursor (C8–C18 hydrocarbons) without the use of any catalysts.

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

Isopropanol dehydration reaction rate kinetics measurement using H 2 O time histories

H 2 O formation during thermal decomposition of isopropanol was measured behind reflected shock waves at temperatures ranging from 1127 to 1621 K at an average pressure of 1.42 atm using a laser absorption technique. Of the five modern chemical kinetics models used to compare the H 2 O time histories, the model from Li et al (Combust. Flame 2019;207:171-185) showed the best overall agreement. Sensitivity and rate of production analyses using the Li et al model (as well as those from AramcoMech 3.0, CRECK, and Togbe et al (Energy Fuel. 2011;25:676-683)) showed unimolecular dehydration of isopropanol, iC 3 H 7 OH ⇌ H 2 O + C 3 H 6 (R1), is nearly the sole reaction controlling H2O production at early times, allowing for an a priori measurement of the forward rate constant k 1 . The Arrhenius expression k1 (s –1 ) = 2.60 × 10 13 exp(-31 120 K/T) was determined to represent best the data from this study. According to the models and previous experimental investigations, the pressure investigated is well within the high-pressure limit (HPL) for this reaction. Additional, higher-pressure experiments also confirmed the HPL assumption. An uncertainty analysis was performed by varying secondary reactions within their uncertainties and examining their effect on the overall prediction, establishing an uncertainty within ±20% for all but the highest temperature cases, which have a maximum uncertainty of ±40%. Experiments conducted with a radical trapper, toluene, showed little influence from radical chemistry, suggesting this estimated uncertainty is fairly conservative. Experimental data from Heyne et al (Z Phys Chem. 2015;229:881-907) were found to be in good agreement with the rate measurements from this study and, therefore, a second Arrhenius expression, k 1 (s –1 ) = 2.11 × 10 13 exp(-30 820 K/T), was found to represent both datasets well. This second expression has a larger temperature range of 976-1621 K. Here the present study provides the first high-temperature data collected for this reaction, adding to the limited data available for isopropanol in the literature.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

BETO 2021 Peer Review - FCIC Task 6: High Temperature Conversion

The impacts of feedstock variability on pyrolysis processes are significant but poorly defined. Current engineering designs are based on empirical guidelines, useful only over a narrow range of feedstock properties. The objectives of this project are to (1) Develop science-based knowledge of how feedstock attributes and operational parameters impact pyrolysis process reliability and product quality; and (2) Build an experimental and computational toolset that predicts these outcomes, enabling processes to optimize reliability and product quality. Biomass is a complex feedstock. Controlling for and testing the effects of individual attributes is very challenging. This project couples multiscale experimentation and modeling to accurately capture the fundamental physics and chemistry of biomass flow and conversion behavior in feeding and pyrolysis reactor operations. Our focus is on pine residue attributes – anatomical fraction (bark, needles, wood), particle morphology (size/shape distribution, density, porosity), and chemical composition (extractives, biopolymers, alkali metals) – that impact product quality for downstream catalytic upgrading. Because detailed pyrolysis product characterization is limited, cutting-edge analytical techniques are being developed to reveal impactful product attributes. The tools and knowledge developed here will enable integrated pyrolysis-based processes that are more robust, flexible, and market-responsive with respect to feedstock variability.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2020

Preparation and Characterization of Various Kraft Lignins and Impact on Their Pyrolysis Behaviors

Lignin-derived chemicals and fuel products have received much attention in the context of bio-refinery. In this study we prepared and characterized various lignin samples from black liquor (BL), a major byproduct from the pulp and paper manufacturing processes, and studied the pyrolysis behaviors of these isolated lignin samples at 600 °C under a N2 atmosphere. Three lignin samples were isolated from the Kraft pulping BL of Loblolly pine linerboard grade process (KL, obtained by direct evaporation; L10, obtained by precipitation at pH 10; L3, obtained by precipitation at pH 3), while another three were from the Kraft pulping BL of Loblolly pine bleach grade process (KB, B10, B3). The inorganic elements present in lignin samples were analyzed using an inductively coupled plasma (ICP) analyzer. The KL and KB samples contained a larger amount of inorganic elements, especially Na and S, than did the other lignin samples. Owing to large quantities of inorganic elements, the ash contents in KL and KB were higher than in the precipitated lignin samples (L10, B10, L3, and B3). These inorganic elements have a significant effect on the subsequent pyrolysis process, as a result, more extensive depolymerization of lignin occurred in KL and KB samples, leading to the formation of fewer pyrolysis oils, with lower molecular weights. NMR analyses of pyrolysis oils show that more methoxyl groups and ether bonds were cleaved, resulting in fewer methoxyl groups and aromatic C–O bonds for the KL and KB heavy oil than for the precipitated lignin heavy oil.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Absolute Photoionization Cross Section of the Simplest Enol, Vinyl Alcohol

The absolute photoionization cross section of vinyl alcohol was determined by multiplexed photoionization mass spectrometry of the Norrish type II photodissociation of butanal at 308 nm. The measured cross sections at 10.005 and 10.205 eV are 7.5 ± 1.9 MB and 8.1 ± 1.9 MB respectively. Here, a higher signal-to-noise ratio photoionization spectrum of vinyl alcohol was recorded via the pyrolysis of 2-chloroethanol and scaled to the absolute cross sections measured using the Norrish type II method. From comparison of our spectrum with previously reported photoelectron spectra we conclude that vinyl alcohol is mainly ionized by direct ionization in the energy range 9 – 9.6 eV, whereas autoionization is responsible for the steady rise in the photoionization spectrum above the end of the Franck-Condon envelope at 9.9 eV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Analysis of Tar and Oil Derived from Pyrolysis and Copyrolysis of Waste Plastics and Biomass

Pyrolysis has been proposed as a potential technology for managing the growing volume of plastic waste generated worldwide. Co-pyrolysis of plastic waste with biomass is a promising technology for generating fuel and chemical products. However, this process generates tar as a waste product. The chemical properties of this tar have yet to be thoroughly analyzed. Further, this study presents the results of gas chromatography–mass spectrometry (GC–MS), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) of oil and tar obtained from the pyrolysis of pure plastics including high-density polyethylene (HDPE), low-density polyethylene (LDPE), polyethylene (PE), polystyrene (PS), and plastic-biomass mixtures. GC–MS analysis revealed the presence of C 7 –C 37 carbon-containing hydrocarbons, which include alkanes and alkenes as the dominant products. FTIR data revealed the presence of various functional groups, including alcohols, aldehydes, ketones, and carboxylic acids, indicating the complexity of the pyrolysis and copyrolysis oil obtained from waste plastics and biomass. TGA data show that tar from all four plastics has a higher decomposition rate, suggesting the presence of heavier hydrocarbons compared with their corresponding oils. This research will be of interest to researchers looking to advance the study of plastic and biomass waste management.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗