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All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Solvent Dynamics in Gel Polymer Electrolytes for Lithium–Sulfur Batteries

Li−sulfur (Li−S) batteries are promising as the next-generation energy storage technology but face challenges due to sluggish sulfur redox reaction (SRR) kinetics and a sulfur shuttling effect. While many studies have explored polycaprolactone (PCL)-based gel polymer electrolytes (GPEs) to address these issues, the influence of solvent properties, including dielectric constant (ϵ) and donor and acceptor numbers (DN and AN), remain unexplored despite their critical impact on performance and full-scale implementation. This study systematically compares three distinct electrolytes, dimethoxyethane (DME), dimethyl sulfoxide (DMSO), and tetraethylene glycol dimethyl ether (TEGDME)-paired with PCL, to correlate the varied solvent properties and their effects on the physical properties of the GPE, in terms of Li + transport and solvation, and polysulfide’s confinement. Among them, the DME-based GPE, with an intermediate DN, exhibited the lowest crystallinity (2.31%), highest ionic conductivity (7.49 mS/cm), and high Li + transference number (0.77). As a result, it achieved a specific capacity of 795 mAh/g sulfur and an average Coulombic efficiency of 97.5% after 120 cycles at C/5, outperforming its competitors. Operando Raman and UV−vis spectroscopy confirmed that PCL effectively confines long-chain polysulfides within its network, mitigating the shuttle effect and facilitating reversible polysulfide conversion. These findings demonstrate that GPEs with moderate DN values and balanced ϵ significantly enhance stability, extend cycle life, and improve rate performance for Li−S batteries. This work provides valuable insights into the design of advanced electrolyte systems for practical energy storage applications.

25 ENERGY STORAGE↗
DOE OSTI2025

Nanoscale Miscibility in In Situ Polymerized Hybrid Electrolytes Speeds Up Ion Dynamics and Enables Stable Cycling of Li Metal Batteries

While the potential use of copolymerized electrolytes in Li metal batteries is subject to intense investigation, the fundamental understanding of the nanoscale domain formation and its effect on Li + transport is still lacking. In this study, we investigated the correlation between the Li + transport mechanism and the miscibility of monomers in polymer blend electrolytes derived from the in situ copolymerization of methyl methacrylate (MMA) and vinylene carbonate (VC) in the presence of polyethylene glycol dimethyl ether (PEGDME) plasticizer and bis(trifluoromethanesulfonyl)imide (LiTFSI) salt. The addition of a polar short chain plasticizer reduced the dynamic and structural heterogeneities of the electrolyte. Small-angle X-ray scattering (SAXS) measurements and coarse-grained molecular dynamics (MD) simulations were used to investigate the nanoscale structure of the electrolytes. The distribution of relaxation times corresponding to the three distinct diffusion mechanisms of the free and interfacial Li + ions at the copolymer/plasticizer and electrolyte/SEI boundaries was analyzed in a broad temperature range to elucidate the Li + transport mechanism. Furthermore, the chemical composition of the SEI and the contribution of a ceramic lithium lanthanum zirconium oxide (LLZO, Li 7 La 3 Zr 2 O 12 ) phase on the interfacial resistance, salt degradation, and SEI stability were studied by X-ray photoelectron spectroscopy (XPS) depth profile analysis and electrochemical testing.

Li metal↗
DOE OSTI2022

Understanding methanol dissociative adsorption and oxidation on amorphous oxide films

Interactions between a transition metal (oxide) catalyst and a support can tailor the number and nature of active sites, for instance in the methanol oxidation reaction.In this report we use ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to identify and compare the surface adsorbates that form on amorphous metal oxide films that maximize such interactions. Considering Al (1−x) M x O y (M = Fe or Mn) films at a range of methanol : oxygen gas ratios and temperatures, we find that the redox-active transition metal site (characterized by methoxy formation) dominates dissociative methanol adsorption, while basic oxygen sites (characterized by carbonate formation) play a lesser role. Product detection, however, indicates complete oxidation to carbon dioxide and water with partial oxidation products (dimethyl ether) comprising a minor species. Comparing the intensity of methoxy and hydroxyl features at a fixed XPS chemical shift suggests methanol deprotonation during adsorption in oxygen rich conditions for high transition metal content. However, increasing methanol partial pressure and lower metal site density may promote oxygen vacancy formation and the dehydroxylation pathway, supported by a nominal reduction in the oxidation state of iron sites. These findings illustrate that AP-XPS and mass spectrometry together are powerful tools in understanding metal–support interactions, quantifying and probing the nature of catalytic active sites, and considering the link between electronic structure of materials and their catalytic activity.

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

Gel composite electrolyte – an effective way to utilize ceramic fillers in lithium batteries

Achieving synergy between ion-conducting polymers and ceramics in a composite electrolyte has been proven to be difficult as the complicated ceramic/polymer interface presents challenges to understand and control. In this work, we report a strategy to utilize discrete ceramic fillers to form a gel composite electrolyte with enhanced transport properties for lithium metal batteries. The matrix of the composite membrane is crosslinked poly(ethylene oxide) with bis(trifluoromethane)sulfonimide lithium salt (LiTFSI). The membrane is plasticized with tetraethylene glycol dimethyl ether (TEGDME). The incorporation of doped-lithium aluminum titanium phosphate particles (LICGC™) into the membrane greatly improves the membrane's cycling characteristics against the lithium electrode, exhibiting lower interfacial impedance, lower overpotential and higher rate capability. The underpinnings of the superior performance of the gel composite electrolyte are discussed in depth. LICGC™ can immobilize the TFSI - anions in the polymer matrix and simultaneously promote Li+ transport by increasing the plasticizer to Li + ratio. Further, the transport enhancement is achieved without sacrificing mechanical properties. The composite membrane shows significantly improved handleability and processability. This work sheds light on the design strategy for a safe electrolyte towards stable Li metal batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Complete characterization of a lithium battery electrolyte using a combination of electrophoretic NMR and electrochemical methods

Improving transport properties of electrolytes is important for developing lithium-ion batteries for future energy storage applications. In Newman's concentrated solution theory, electrolytes are characterized by three transport parameters, conductivity, diffusion coefficient, and transference number, in addition to the thermodynamic factor. In this work, these parameters are all determined for an exemplar liquid electrolyte, lithium bis(trifluoromethanesulfonyl)imide mixed in tetraethylene glycol dimethyl ether, using electrochemical methods. The intrinsic coupling between parameters obtained by electrochemical methods results in large error bars in the transference number that obscure the transport behavior of the electrolyte. Here, we use electrophoretic NMR (eNMR) to measure the electric-field-induced ion and solvent velocities to obtain the transference number directly, which enables determination of the thermodynamic factor with greater certainty. In conclusion, our work indicates that the combination of eNMR and electrochemical methods provides a robust approach for complete characterization of battery electrolytes.

25 ENERGY STORAGE↗
DOE OSTI2023

An Experimental Comparison of Cyclic Variations in Diesel–Natural Gas and POMDME–Natural Gas Dual Fuel Combustion

Abstract Cyclic variations in internal combustion engines are caused by various factors, including combustion mixture stratification, in-cylinder flows, local fluctuations in air-fuel ratio, etc. Cyclic variations have a profound impact on engine performance and emissions. In this study, cyclic variations in dual fuel combustion are analyzed, comparing diesel–natural gas (NG) and polyoxymethylene dimethyl ether (POMDME)-NG dual fuel combustion. Cyclic variability was initially quantified using the coefficient of variation of gross indicated mean effective pressure (IMEPg) computed from experimental cylinder pressure data. The cases analyzed in this study had a coefficient of variation (COV) of IMEPg greater than or around 5%, which was the lower limit of onset of instability for this engine. Experiments were performed at two fixed start of injection (SOI) of high-cetane fuel: 310 CAD and 350 CAD. For all experiments, a constant load of 5 bar IMEPg was maintained, and the intake boost pressure and rail pressure were fixed at 1.5 bar and 500 bar, respectively. For each case, 1000 cycles of cylinder pressure data were recorded, filtered, and processed using an in-house heat release analysis code for each cycle. A comparison between individual cycles and the “ensemble averaged cycle” was made for both diesel–NG and POMDME–NG combustion. For the early SOI of 310 CAD, the peak cylinder pressure fluctuations of individual cycle were found to be ± 15 bar for both fuel combinations, compared to the ensemble averaged cycle, and < 1/10th of the cycles had an IMEPg lower than 0.05 bar of the ensemble averaged cycle. However, the peak pressure fluctuations were found to be lower for POMDME–NG (±3 bar) than diesel–NG dual fuel combustion at 350 CAD SOI, indicating lower cyclic variations. The higher reactivity of POMDME helped reduce fluctuations in combustion phasing at the retarded SOI. The presence of cycles of deterioration and cycles of recovery were also observed with diesel–NG combustion for 310 CAD SOI, and the scatter in the IMEPg return map was similar for both fuel combinations. The IMEPg return map for POMDME–NG combustion was less scattered at the 350 CAD SOI.

Engineering↗
DOE OSTI2026

Identifying Bounds of Inorganic Content in Solventless Processing of Hybrid Solid Electrolytes

Solid-state lithium batteries require safe, robust electrolytes to enable higher energy densities and improved safety over conventional cells. Hybrid polymer–ceramic electrolytes are a promising solution, combining the processability of polymers with the high ionic conductivity and mechanical strength of inorganic fillers. In this work, we demonstrate a solventless, UV-curing method to produce hybrid solid electrolytes using a poly(ethylene glycol) dimethyl ether (PEGDME)-based photocurable matrix incorporating Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP) or Li 7 La 3 Zr 2 O 12 (LLZO) ceramic electrolyte. Inorganic filler loadings up to ∼55 wt.% could be successfully incorporated via this process which was the highest inorganic content at which the slurry remains processable and cured into a uniform film. The resulting UV-cured composite electrolytes remain flexible and exhibit room-temperature ionic conductivities on the order of 10 −4 S·cm −1 , along with notably improved lithium-ion transference numbers compared to conventional polymer electrolytes. Similar performance and processing limits were observed for both LAGP and LLZO, indicating that ceramic filler chemistry does not significantly affect the UV-curing process or the electrolyte's ion transport properties in this regime. Eliminating solvents from fabrication not only simplifies processing and mitigates environmental concerns but also enables higher solid contents that enhance mechanical strength and help suppress lithium dendrite formation. In conclusion, this scalable approach thus paves the way for manufacturing robust composite solid electrolytes for next-generation solid-state batteries (SSBs).

Batteries↗
DOE OSTI2024

Performance and Emissions of an SI Engine Fueled With DME-Propane Blends

Dimethyl Ether (DME) is an alternative fuel that can be produced renewably and has the potential for lower CO and NOx emissions than conventional petroleum-based fuels. Blending DME with another gaseous fuel such as propane, which has a lower knock tendency than gasoline, can allow this fuel to be leveraged on SI engines. In this study, the use of DME-propane blends on a spark ignition (SI) engine was studied via computer simulations in order to understand the impact on engine performance and emissions and to identify the knock limitations of using such fuel blends. A 2L Hyundai SI engine was modeled in GT Power and the model was validated by comparing it with computational fluid dynamics (CFD) simulation results. Starting from pure propane, DME was added incrementally until knock was observed in the engine. Results indicate that it is feasible to run propane with DME percentages up to 35% before severe knock impacts were observed. The BTE was higher, but the BSFC also increased for DME-propane blends as compared to gasoline. Here, an increase in NOx emissions was detected along with a significant decrease in CO emissions. CO 2 emissions declined for propane as compared to gasoline but increased with the addition of DME.

alternative fuels↗
DOE OSTI2024

Experimental Investigation of the Effect of Air-Handling and DME-Propane Blends on the Performance and Emissions of a 4-Cylinder CI Engine

Dimethyl ether (DME) is considered an excellent alternative to diesel because of its higher cetane number and lower carbon content. Additionally, DME can be blended with abundantly available propane with minimal modifications to the propane infrastructure. This paper focuses on an experimental investigation of the effect of air-handling i.e., boost pressure and exhaust gas recirculation (EGR), and DME-propane blends on the combustion and emissions performance of a light-duty, four-cylinder, compression ignition (CI) engine. Here, the boost pressure and EGR sweeps were carried out and showed that higher boost pressures resulted in increased brake thermal efficiencies (BTE) at the expense of higher NOx emissions which could be reduced by an increase in EGR. The fuel sweeps were carried out at 0, 15 and 25% propane (neat, 85% and 75% DME) with 0% and 25% EGR. The fuel sweeps indicated that the ignition delay (ID) increased and burn duration (BD) decreased monotonically when the blend increased to 25% propane/75% DME. The results suggest optimum engine performance with neat DME at 105 kPa boost pressure and 25% EGR with propane addition improving the BTE with negligible increase in emissions. Higher contents of Propane, up to 25%, did not affect the variability of combustion, with standard deviations of burn duration and peak cylinder pressures below 1% for all test cases.

air-handling↗
DOE OSTI2020

Materials Data on ZnP2H15C5NO9 by Materials Project

ZnP2H3O8C3NH8CH3CHO crystallizes in the orthorhombic P2_12_12_1 space group. The structure is three-dimensional and consists of four dimethyl ether molecules, four trimethylazanium molecules, and one ZnP2H3O8 framework. In the ZnP2H3O8 framework, Zn2+ is bonded to four O2- atoms to form ZnO4 tetrahedra that share corners with four PO4 tetrahedra. There are a spread of Zn–O bond distances ranging from 1.94–1.98 Å. There are two inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent ZnO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.52–1.59 Å. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with two equivalent ZnO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.53–1.61 Å. There are three inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.04 Å) and one longer (1.50 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the third H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.03 Å) and one longer (1.55 Å) H–O bond length. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Zn2+ and one P5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Zn2+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Zn2+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Zn2+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a trigonal planar geometry to one P5+ and two H1+ atoms. In the seventh O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H1+ atom. In the eighth O2- site, O2- is bonded in a bent 120 degrees geometry to one P5+ and one H1+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on H4C6O by Materials Project

(CH)4C2O crystallizes in the orthorhombic Pbcn space group. The structure is zero-dimensional and consists of four dimethyl ether molecules and sixteen methane molecules.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al3P3C4NO13 by Materials Project

C2N(AlPO4)3C2O is Low Tridymite-derived structured and crystallizes in the orthorhombic P2_12_12 space group. The structure is three-dimensional and consists of four dimethyl ether molecules, four n-methyl methanimine molecules, and one AlPO4 framework. In the AlPO4 framework, there are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four PO4 tetrahedra. There is two shorter (1.75 Å) and two longer (1.76 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four PO4 tetrahedra. There is two shorter (1.75 Å) and two longer (1.76 Å) Al–O bond length. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four PO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.74–1.76 Å. There are three inequivalent P5+ sites. In the first P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four AlO4 tetrahedra. There is two shorter (1.53 Å) and two longer (1.54 Å) P–O bond length. In the second P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four AlO4 tetrahedra. There are a spread of P–O bond distances ranging from 1.53–1.55 Å. In the third P5+ site, P5+ is bonded to four O2- atoms to form PO4 tetrahedra that share corners with four AlO4 tetrahedra. All P–O bond lengths are 1.54 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the second O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the sixth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the ninth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the eleventh O2- site, O2- is bonded in a bent 150 degrees geometry to one Al3+ and one P5+ atom. In the twelfth O2- site, O2- is bonded in a linear geometry to one Al3+ and one P5+ atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Zn2H24C12Br7O6 by Materials Project

Zn2C10H20O5Br7CH3CHO crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two dimethyl ether molecules and one Zn2C10H20O5Br7 cluster. In the Zn2C10H20O5Br7 cluster, there are two inequivalent Zn2+ sites. In the first Zn2+ site, Zn2+ is bonded to four O2- and two Br1- atoms to form corner-sharing ZnBr2O4 pentagonal pyramids. There are a spread of Zn–O bond distances ranging from 2.22–2.37 Å. There are one shorter (2.44 Å) and one longer (2.50 Å) Zn–Br bond lengths. In the second Zn2+ site, Zn2+ is bonded to one O2- and three Br1- atoms to form corner-sharing ZnBr3O tetrahedra. The Zn–O bond length is 2.13 Å. There are a spread of Zn–Br bond distances ranging from 2.36–2.45 Å. There are ten inequivalent C+0.75- sites. In the first C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the second C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the third C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the fourth C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.45 Å. In the fifth C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the sixth C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. In the seventh C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.45 Å. In the eighth C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.45 Å. In the ninth C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.45 Å. In the tenth C+0.75- site, C+0.75- is bonded in a distorted trigonal non-coplanar geometry to two H1+ and one O2- atom. Both C–H bond lengths are 1.10 Å. The C–O bond length is 1.44 Å. There are twenty inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the second H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the third H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the fourth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the fifth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the sixth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the seventh H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the eighth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the ninth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the tenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the eleventh H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the twelfth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the thirteenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the fourteenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the fifteenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the sixteenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the seventeenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the eighteenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the nineteenth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. In the twentieth H1+ site, H1+ is bonded in a single-bond geometry to one C+0.75- atom. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Zn2+ and two C+0.75- atoms. In the second O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Zn2+ and two C+0.75- atoms. In the third O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to one Zn2+ and two C+0.75- atoms. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Zn2+ and two C+0.75- atoms. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to one Zn2+ and two C+0.75- atoms. There are seven inequivalent Br1- sites. In the first Br1- site, Br1- is bonded in a single-bond geometry to one Zn2+ and one Br1- atom. The Br–Br bond length is 3.11 Å. In the second Br1- site, Br1- is bonded in a water-like geometry to two Zn2+ atoms. In the third Br1- site, Br1- is bonded in a single-bond geometry to one Zn2+ atom. In the fourth Br1- site, Br1- is bonded in a single-bond geometry to one Zn2+ and one Br1- atom. The Br–Br bond length is 2.99 Å. In the fifth Br1- site, Br1- is bonded in a distorted linear geometry to two Br1- atoms. The Br–Br bond length is 2.42 Å. In the sixth Br1- site, Br1- is bonded in a distorted single-bond geometry to one Br1- atom. In the seventh Br1- site, Br1- is bonded in a distorted linear geometry to two Br1- atoms. The Br–Br bond length is 2.43 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Rapid Assessment of Autoignition Propensity in Novel Fuels and Blends

We developed a computational strategy to correlate bulk combustion metrics of novel fuels and blends in the low-temperature autoignition regime with measurements of key combustion intermediates in a small-volume, dilute, high-pressure reactor. We used neural net analysis of a large simulation dataset to obtain an approximate correlation and proposed experimental and computational steps needed to refine such a predictive correlation. We also designed and constructed a high-pressure laboratory apparatus to conduct the proposed measurements and demonstrated its performance on three canonical fuels: n-heptane, i-octane, and dimethyl ether.

10 SYNTHETIC FUELS↗
DOE OSTI2022

A Novel Catalytic Membrane Reactor for DME Synthesis from Renewable Resources

Production of liquid fuels or chemicals from CO 2 (captured from the air or flue gases) and renewable hydrogen presents a new approach to producing clean fuels domestically. While significant progress has been made in the area of renewable electricity generation from solar and wind, a large gap remains with respect to the production of renewable liquid fuels/chemicals. Other processes for producing liquid fuels/chemicals from renewable electricity are constrained by thermodynamic limitations, making them prohibitively expensive and impractical. The team is overcoming these limitations and developing catalytic membrane reactor processes with high yields and low energy penalties. Supported by the Advanced Research Projects Agency-Energy (ARPA-E) of the US Department of Energy (DOE), GTI Energy and partners have been developing a technology for the production of renewable dimethyl ether (DME) from carbon dioxide (CO 2 ) and renewable hydrogen (H 2 ) using a novel catalytic membrane reactor and demonstration of this system at a scale of 1 kg/day. DME is a clean-burning, non-toxic fuel with a high cetane value (55-60), making it an excellent diesel alternative. DME can be stored as a liquid under moderate pressure, eliminating the need for the high-pressure containers used for CNG or cryogenics, as in the case of LNG. DME is also approved as a renewable fuel under the U.S. Environmental Protection Agency’s Renewable Fuels Standard (RFS), making it eligible for Renewable Identification Numbers (RINs) credits. By producing DME through the catalytic conversion of captured CO 2 and renewable H 2 , this process will produce renewable liquid transportation fuel and a means of large-scale utilization of captured CO 2 . In the DME synthesis process, CO 2 and H 2 are fed to a hollow fiber catalytic membrane reactor at 300-600 psig that contains a bi-functional catalyst that combines two reactions, methanol synthesis (CO 2 + 3H 2 → CH 3 OH + H 2 O) and methanol dehydration (2CH 3 OH → CH 3 OCH 3 + H 2 O), into a one-step process to produce DME. The bifunctional catalyst converts methanol to DME, enabling higher overall CO 2 conversion. A Cu/ZnO/ZrO 2 /Al 2 O 3 (CZZA) catalyst is used for methanol synthesis and is coupled with a zeolite catalyst H-ZSM-5 for dehydration. This one-step process intensifies a process that would otherwise require multiple reaction steps. However, combining these two reactions results in increased water production which inhibits catalytic activity. Here, the Na + -gated, water-transport membrane (Science, vol. 367, pp. 667, 2020), removes water in situ, shifting the thermodynamic equilibrium towards product formation while decreasing kinetic inhibition from water adsorption onto the catalyst surface. The Na + gated, water-transport nanochannel membrane showed H 2 O/CO 2 selectivity of 560 at 250 °C and 300 psig for H 2 O/CO 2 /CO/H 2 /MeOH gas mixtures. The selectivities of H 2 O/H 2 , H 2 O/CO, and H 2 O/MeOH were 190, 170, and 80, respectively. In a laboratory-scale membrane reactor, DME synthesis testing using this membrane, a DME production rate of 440 g DME /kg cat /h was achieved at 260 °C and 550 psig. Compared to the packed bed reactor, the CO 2 conversion and DME production rate in the membrane reactor were 80% and three times higher, respectively. A prototype test system (1 kg/day) was designed, constructed, and tested. A DME production rate of 1.31 kg/day and a DME productivity of 360 g/h/kg were achieved in the prototype membrane reactor. Good stability was demonstrated during 150-h continuous operation and multiple startups/shutdowns tests.

10 SYNTHETIC FUELS↗
DOE OSTI2023

Direct conversion of syngas to lower olefins precursors of jet fuel and chemicals

This study investigates the direct conversion of syngas to olefins as a pathway to produce sustainable aviation fuels. This approach combines methanol/ dimethyl ether synthesis with methanol-to-olefins into one unit operation to avoid the equilibrium limitation of methanol synthesis and the Anderson–Schulz–Flory distribution limitations from the Fischer Tropsch process. The ability to combine reactor functionalities into a single step are also projected to significantly lower capital costs over current synthesis approaches for the syngas to olefins process.

10 SYNTHETIC FUELS↗
DOE OSTI2021

Spill Behavior, Detection, and Mitigation for Emerging Nontraditional Marine Fuels

In this report, we describe the predicted impact of large spills or releases of alternative marine fuels. The fuels covered in this report are those that have been identified as potential future fuels for the marine shipping sector by industry experts and government agencies overseeing the development of renewable and low-carbon fuels. Several of these fuels are already in use, such as liquified natural gas, renewable diesel, ethanol, methanol, and biodiesel. Other fuels are hydrogen, dimethyl ether, ammonia, and bio-intermediates, such as catalytic fast pyrolysis biooils and hydrothermal liquefaction bio-crudes. The property databases of these fuels are extensive enough to form predictive assessments. Other potential marine fuels, such as lignin ethanol, have not been extensively evaluated and are therefore not included is this study. For each fuel chemistry, we have surmised the spill profiles and environmental impacts based on existing studies and relevant properties. The technologies used to detect spills (especially those for crude oil detection) are also reviewed for their applicability with alternative fuels, and in some instances, recommendations to improve these technologies for use with a particular fuel chemistry are put forward. Finally, current containment and remediation technologies are reviewed and assessed for their efficacy at handling these alternative fuels.

04 OIL SHALES AND TAR SANDS↗