Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “DME”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Study on ammonia and dimethyl ether oxidation and kinetic interaction up to 100 atm

NH 3 and DME dual fuel oxidation and kinetic coupling are experimentally studied by using a supercritical pressure jet-stirred reactor (SP-JSR) at 20 and 100 atm, over a temperature range of 500–900 K, and at fuel-lean and stoichiometric conditions with NH 3 to DME molar ratios of 4 and 0.62, respectively. An HP-Mech model for high-pressure NH3/DME oxidation is developed based on our previous studies and it shows generally better performance than other models in the literature on high-pressure oxidation experiments. Due to DME’s strong low-temperature reactivity, it dramatically enhances the oxidation of NH3 at low temperature. However, the effect of NH 3 on DME oxidation varies with temperature. At low temperatures, NH 3 inhibits low-temperature reactivity by consuming OH radicals. In addition, the NH 2 and NO x formation from NH 3 further suppresses the low-temperature DME reactivity by reducing alkylperoxyl and O 2 QOOH radicals via RO 2 + NH 2 = RO + H 2 NO, RO 2 + NO = RO + NO 2 and O 2 QOOH + NO = 2CH 2 O + HO 2 + NO 2 . At intermediate temperatures, due to enhanced kinetic coupling of NH 2 /NO x /HO 2 chemistry, DME oxidation is significantly promoted. It is found that there are two major NH 2 /NO x /HO 2 coupling pathways for OH radical production brought by NH 3 : (1) NH 2 + HO 2 = H 2 NO + OH and (2) NH 2 + NO 2 = H 2 NO + NO with NO + HO 2 = OH + NO 2 . Moreover, the resulting H 2 NO will further contribute to OH production via the H 2 NO/NO x /HONO coupling pathways: H 2 NO + NO 2 = HNO + HONO, HNO + NO 2 = HONO + NO, and HONO (+M) = OH + NO (+M). These new NH 2 /NO x /HO 2 and H 2 NO/NO x /HONO pathways play a critical role in promoting DME oxidation at intermediate temperatures. Novelty and Significance Statement: Blending NH 3 with DME can significantly enhance the reactivity of NH 3 and facilitate its practical application in advanced internal combustion engines. NH 3 /DME oxidation is studied in a novel supercritical pressure jet-stirred reactor up to 100 atm, a much higher pressure than previous studies. An interesting non-monotonic effect of NH3 addition on fuel oxidation has been found. Unique kinetic couplings of NH2/HO2/NOx and H2NO/NOx/HONO brough by NH3 and DME blending are identified to play important roles in radical generation and reactivity promotion. The valuable experimental data and key kinetics revealed in the current work can tremendously improve our understanding of NH 3 /DME oxidation via NO x /RO 2 and NH 2 / H 2 NO/HO 2 /NO x kinetic couplings at low to intermediate temperatures.

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

Harnessing dimethyl ether with ultra-low-grade heat for scaling-resistant brine concentration and fractional crystallization

Solvent-driven separations may enable scalable concentration of hypersaline brines, supporting a circular resource economy from the extraction of lithium and rare earth elements from spent battery and magnet leachates. This work analyses a novel solvent-driven water extraction (SDWE) system employing dimethyl ether (DME) and ultra-low-grade heat for brine concentration and fractional crystallization. SDWE exploits DME’s unique properties: (1) a low dielectric constant that promotes water solubility over charged solutes by a factor of 10 3 , and (2) a high volatility that facilitate efficient DME reconcentration with ultra-low-grade heat. The techno-economic viability of SDWE is assessed with a computational framework that encompasses a liquid–liquid separator and a solvent concentrator. We integrate the extended universal quasichemical model with the virial equation of state to predict the compositions of the complex three-phase DME-water mixture at vapor–liquid and liquid–liquid equilibrium. Subsequently, we optimize the thermodynamic and economic performance of SDWE, by controlling the interstage flash pressure, heat source temperature, and the number of concentrating stages. DME-based SDWE concentrates an input saline feed to 5.5 M and regenerates over 99 % of the DME using ultra-low-grade heat below 50 °C, with a DME/water selectivity ratio of 125. Here our calculations reveal that optimal performance is achieved at interstage flash pressures of 0.4 – 0.5 bar for heat source temperatures between 323–373 K, with improved exergetic efficiencies at lower temperatures. At a heat source temperature of 323 K and an interstage pressure of 0.489 bar, DME-driven SDWE achieves an optimal thermodynamic efficiency of 20.5 % and a projected specific cost of US$ 1.93 m -3 . These specific costs suggest that SDWE is competitive with commercialized thermal distillation technologies, while mitigating the traditional risks associated with scaling in heat and mass exchangers with hypersaline brines.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

A separations and purification process for improving yields and meeting fuel contaminant specifications for high-octane gasoline produced from dimethyl-ether over a Cu/BEA catalyst

In this work, we have been developing a three-step conversion of biomass-derived syngas to methanol to dimethyl-ether (DME) to non-aromatic hydrocarbons for use as high-octane gasoline and sustainable aviation fuel. This process produces branched alkanes from DME using a Cu/BEA catalyst and is a promising alternative to other syngas conversion processes such as Fischer-Tropsch to linear alkanes and traditional ZSM-5 catalyzed methanol to aromatic gasoline. In this short article we describe some advances in our understanding related to separations and purification via the use of more detailed experimental speciation in an updated process model involving multiple phase equilibrium-based separation steps. Primary modeled reactor outlet constituents (and weight %) are: C3 and lighter hydrocarbon gases (11.1%), C4s (54.5%), H 2 (1.2%), CO 2 (2.9%), water (5.0%), unreacted DME (16.5%), methanol (2.3%), and C5+ hydrocarbons (6.4%). DME (the primary reactant) and H 2 recycle and reuse are important for the overall process efficiency, and the recycle of C4s is important to increase the C5+ yield via reactivation and homologation. Thus H 2 , C4s, and DME are targeted for recycle, while methanol and water need to be removed from the product to conform with fuel specifications. Model predictions from Aspen Plus using the NRTL-RK property method indicate a fuel composition with C5+ content of 97.1 wt%, with minor constituents: 2.4 wt% C4s, 0.3 wt% methanol, 0.1 wt% DME, 0.03 wt% water, and 0.01 wt% C3s. These ranges of minor components conform with fuel quality requirements, and the modeled product is amenable for unconstrained blending to boost gasoline octane ratings.

09 BIOMASS FUELS↗
DOE OSTI2022

Benchmarking Cu/BEA and HBEA catalysts for high-octane gasoline synthesis

We distinguish rates at which carbon deposition occurs during initiation, rates at which catalytic centers are lost during deactivation, and paraffin-to-olefin ratio during propagation as benchmarks that distinguish 5 wt% Cu/H-BEA and H-BEA (Si/Al = 13.5) catalysts during dimethyl ether (DME) homologation in the presence of hydrogen. Studies that systematically vary initial DME contact time (210, 94, and 45 mol H+, initial s (mol C ) -1 ), DME pressure (4 and 22 kPa), and H 2 pressure (1, 24, and 48 kPa) reveal that Cu enables lower carbon deposition rates (on a per proton basis) in the induction period, increases the effluent paraffin-to-olefin ratio during propagation, and decreases the instantaneous site-loss yields by a factor of ~ 1.5-2x (moles of active sites lost per mole of DME) during termination sequences thus affecting the degree of product saturation and catalyst stability during DME homologation. Furthermore, these results provide mechanistic insights revealing the critical role of Cu in facilitating DME homologation to high value, high-octane gasoline-range hydrocarbons with higher cumulative turnovers than proton form H-BEA.

09 BIOMASS FUELS↗
DOE OSTI2024

Electrically Powered High-Salinity Brine Separation Using Dimethyl Ether

Dewatering highly saline aqueous streams, from mining and geothermal leachates to industrial wastewater, is essential for effective resource recovery and safe disposal. Membraneless water extraction (MWE) uses a low-polarity solvent to separate water from concentrated aqueous solutions. In this study, we design a new MWE that uses dimethyl ether (DME) to selectively extract water from high-salinity brines, leveraging the volatility of DME to achieve rapid solvent recovery. By separating water and dissolved salts at a liquid–liquid interface, MWE minimizes the deleterious effects of scaling on vulnerable membrane and heat exchanger surfaces, reducing the need for extensive pretreatment and expensive materials. We begin by developing a computational framework for a multistage counterflow liquid–liquid contactor, which extracts water into DME, coupled with a multistage solvent regenerator that uses vapor compression to efficiently separate the desalinated water from the DME extractant. Excess Gibbs free energy and equation of state frameworks are used to model fluid phase equilibria in water–DME–sodium chloride (NaCl) mixtures, with interaction parameters estimated from experimental data. Incorporating equilibrium calculations into a system-scale computational model, we examine the performance of MWE using DME for the first time. Our analysis demonstrates that MWE can concentrate seawater desalination brine (>1.0 mol NaCl kg –1 ) to zero-liquid discharge salinities, with an energy consumption of under 50 kW h per m 3 of water extracted with a solvent recovery ratio greater than 99.9%. We highlight the importance of staging the vapor compression process to simultaneously minimize energy consumption while enabling brine concentration and product water solvent contamination. Finally, the thermodynamic framework developed here allows for the robust evaluation of new MWE solvents and systems for critical brine concentration and fractional precipitation applications.

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

Role of a Multivalent Ion–Solvent Interaction on Restricted Mg 2+ Diffusion in Dimethoxyethane Electrolytes

The diffusion behavior of Mg 2+ in electrolytes is not as readily accessible as that from Li + or Na + utilizing PFG NMR, due to the low sensitivity, poor resolution, and rapid relaxation encountered when attempting 25 Mg NMR. In MgTFSI 2 /DME solutions, “bound” DME (coordinating to Mg 2+ ) and “free” DME (bulk) are distinguishable from 1 H NMR. With the exchange rates between them obtained from 2D 1 H EXSY NMR, we can extract the self-diffusivities of free DME and bound DME (which are equal to that of Mg 2+ ) before the exchange occurs using PFG diffusion NMR measurements coupled with analytical formulas describing diffusion under two-site exchange. Further, the high activation enthalpy for exhange (65–70 kJ/mol) can be explained by the structural change of bound DME as evidenced by its reduced C–H bond length. Comparison of the diffusion behaviors of Mg 2+ , TFSI – , DME, and Li + reveals a relative restriction to Mg 2+ diffusion that is caused by the long-range interaction between Mg 2+ and solvent molecules, especially those with suppressed motions at high concentrations and low temperatures.

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

Design of a High-Pressure Fuel System for Use with Dimethyl Ether

The paper documents the modeling and experimental work on a common rail fuel injection system for Dimethyl Ether, a potential diesel substitute with a low carbon intensity signature. The DME fuel system is deployed on a light duty 2.2L compression ignition engine. The paper describes the injector optimization to shift to higher flows to account for the lower heating value and density of the DME when compared to diesel. The type of the injection system used for the DME application is an advanced rendering of the Common rail noted for a one-piece piston-needle injector construction and a solenoid driven spill valve featuring a pressure balanced poppet. A dedicated high-pressure fuel pump designed to pressurize DME is used. The design results in a fast acting open and close injection event, reduced leakage, with reduced cavitation in the fuel injector volume. Design parameters for system optimization included fill and spill orifices, needle lift, bias spring, and injector hole size. The design model provides good correlation of the instantaneous rates of injection with experiments across a wide range of pressure and injection timings. Proposed performance milestones for the design included similar DME injection duration to the diesel counterpart for same fuel energy injected into the cylinder to retain high engine cycle efficiency. Here, the dedicated DME design provided reduced hydraulic delays of 50%. Tests demonstrated sustained operation at pressures of 1000 bar, with capability to reach 1500bar. Durability tests showed no cavitation-deterioration over a 200-hour test cycle by means of spray imaging and hardware inspection.

De Ojeda, William [WM International Engineering, L↗
DOE OSTI2026

Methanol mixing−controlled compression ignition enabled via homogeneous charge compression ignition of dimethyl ether through catalytic decomposition of methanol

Methanol is a potentially attractive fuel for marine and off−road engines owing to its availability at bunkering and global distribution locations. Although methanol is well−distributed worldwide, its fuel chemistry and ignition properties make it poorly suited as a direct drop−in replacement for diesel fuel in compression−ignition engines. However, industrial processes are regularly used to convert methanol, via catalytic dehydration, to dimethyl ether (DME) over nonprecious metal catalysts. This chemical conversion can occur at relatively low pressures, temperatures, and catalyst space velocities, highlighting a potential opportunity to generate DME via onboard catalytic dehydration of methanol. DME’s fuel kinetic and ignition properties for compression ignition are much more favorable than those of methanol or even diesel fuel, but DME is more challenging than diesel fuel or methanol to pump, store, and deliver through conventional diesel fueling injection hardware. Thus, a potential opportunity exists to use the ignition and kinetic properties of DME, with the transportation and delivery advantages of methanol, in a methanol−fueled mixing−controlled compression−ignition engine. The present work explores performance, combustion behavior, and emissions reduction opportunities for methanol mixing−controlled combustion, enabled by a HCCI of DME that represents a small fraction of the total fuel energy that can be generated onboard via catalytic dehydration of methanol.

Splitter, Derek [ORNL] (ORCID:0000000174044047)↗
DOE OSTI2020

Enhanced stability of Fe-modified CuO-ZnO-ZrO 2 -Al 2 O 3 /HZSM-5 bifunctional catalysts for dimethyl ether synthesis from CO 2 hydrogenation

In this report a series of iron (Fe) modified CuO-ZnO-ZrO 2 -Al 2 O 3 (CZZA) catalysts, with various Fe loadings, were prepared using a co-precipitation method. A bifunctional catalyst, consisting of Fe-modified CZZA and HZSM-5, was studied for dimethyl ether (DME) synthesis via CO 2 hydrogenation. The effects of Fe loading, reaction temperature, reaction pressure, space velocity, and concentrations of precursor for the synthesis of the Fe-modified CZZA catalyst on the catalytic activity of DME synthesis were investigated. Long-term stability tests showed that Fe modification of the CZZA catalyst improved the catalyst stability for DME synthesis via CO 2 hydrogenation. The activity loss, in terms of DME yield, was significantly reduced from 4.2% to 1.4% in a 100 h run of reaction, when the Fe loading amount was 0.5 (molar ratio of Fe to Cu). An analysis of hydrogen temperature programmed reduction revealed that the introduction of Fe improved the reducibility of the catalysts, due to assisted adsorption of H 2 on iron oxide. The good stability of Fe-modified CZZA catalysts in the DME formation was most likely attributed to oxygen spillover that was introduced by the addition of iron oxide. This could have inhibited the oxidation of the Cu surface and enhanced the thermal stability of copper during long-term reactions.

42 ENGINEERING↗
DOE OSTI2022

Olefin methylation over iron zeolites and the methanol to hydrocarbons reaction

The effect of olefin addition to a stream of dimethyl ether on the methanol homologation reaction is investigated using iron-substituted zeolites Fe-beta and Fe-ZSM-5. The reaction was investigated using plug-flow microreactors in the temperature range of 240–400 °C, at a total pressure of 0.239 MPa and a WHSV of 6.12 (g DME/ gcat -hr). For Fe-beta (Si/Fe= 9.2) catalysts, isobutene co-feeding almost doubles dimethyl ether (DME) consumption rate and shifts selectivity towards larger olefins with carbon numbers from 5 to 7. Addition of isobutene above 6.3%, however, resulted in a reduction of DME consumption rates, an effect assigned to the replacement of surface methoxy groups for adsorbed olefins in the zeolite pores. Below a temperature of 340 °C hydride-transfer rates are negligible; reaction rates are stable for over 5.5 h and the products consist almost exclusively of olefins and a small amount of methane. Above 360 °C the onset of catalytic hydride transfer processes is observed leading to fast catalyst deactivation rates and an increase in the concentration of aromatic species. Iron ZSM-5 (Si/Fe = 21.4) catalysts under similar reaction conditions consumes methanol faster than Fe-beta at approximately three times the TOF (on a per iron basis). The Fe-ZSM-5 catalyst was selective to a distribution of products (C5 to C8) as compared to Fe-beta which was selective to primarily C5 and C7. Co-feeding larger olefins (2-methyl-2-butene, 2,3-dimethyl-2-butene, 2,3,3-trimethyl-1-butene, and 2,4,4-trimethyl-2-pentene) at a 3.9% olefin concentration over Fe-beta changed selectivity towards cracking products (C4 compounds such as isobutene). As the size of the olefin increases, a reduction of DME consumption rate is also observed. Here these results show that co-feeding olefins with DME over Fe-zeolites is a promising route to increase methylation rates at relatively low temperatures producing larger branched olefins and that the product distribution is highly dependent on the zeolite pore size and structure of the olefin.

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

Homoleptic Perchlorophenyl “Ate” Complexes of Thorium(IV) and Uranium(IV)

The reaction of AnCl 4 (DME) n (An = Th, n = 2; U, n = 0) with 5 equiv of LiC 6 Cl 5 in Et 2 O resulted in the formation of homoleptic actinide-aryl “ate” complexes [Li(DME) 2 (Et 2 O)] 2 [Li(DME) 2 ][Th(C 6 Cl 5 ) 5 ] 3 ([Li][1]) and [Li(Et 2 O) 4 ][U(C 6 Cl 5 ) 5 ] ([Li][2]). Similarly, the reaction of AnCl 4 (DME)n (An = Th, n = 2; U, n = 0) with 3 equiv of LiC 6 Cl 5 in Et 2 O resulted in the formation of heteroleptic actinide-aryl “ate” complexes [Li(DME) 2 (Et 2 O)][Li(Et 2 O) 2 ][ThCl 3 (C 6 Cl 5 ) 3 ] ([Li][3]) and [Li(Et 2 O) 3 ][UCl 2 (C 6 Cl 5 ) 3 ] ([Li][4]). Density functional calculations show that the An–C ipso σ-bonds are considerably more covalent for the uranium complexes vs the thorium analogues, in line with past results. Additionally, good agreement between experiment and calculations is obtained for the 13 C ipso NMR chemical shifts in [Li][1] and [Li][3]. Here, the calculations demonstrate a deshielding by ca. 29 ppm from spin–orbit coupling effects originating at Th, which is a direct consequence of 5f orbital participation in the Th–C bonds.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Quantification of Key Peroxy and Hydroperoxide Intermediates in the Low-Temperature Oxidation of Dimethyl Ether

Dimethyl ether (DME) oxidation is a model chemical system with a small number of prototypical reaction intermediates that also has practical importance for low-carbon transportation. Although it has been studied experimentally and theoretically, ambiguity remains in the relative importance of competing DME oxidation pathways in the low-temperature autoignition regime. To focus on the primary reactions in DME autoignition, we measured the time-resolved concentration of five intermediates, CH 3 OCH 2 OO (ROO), OOCH 2 OCH 2 OOH (OOQOOH), HOOCH 2 OCHO (hydroperoxymethyl formate, HPMF), CH 2 O, and CH 3 OCHO (methyl formate, MF), from photolytically initiated experiments. We performed these studies at P = 10 bar and T = 450-575 K, using a high-pressure photolysis reactor coupled to a time-of-flight mass spectrometer with tunable vacuum-ultraviolet synchrotron ionization at the Advanced Light Source. Our measurements reveal that the timescale of ROO decay and product formation is much shorter than predicted by current DME combustion models. The models also strongly underpredict the observed yields of CH 2 O and MF and do not capture the temperature dependence of OOQOOH and HPMF yields. Adding the ROO + OH $\rightarrow$ RO + HO 2 reaction to the chemical mechanism (with a rate coefficient approximated from similar reactions) improves the prediction of MF. Increasing the rate coefficients of ROO ↔ QOOH and QOOH + O 2 ↔ OOQOOH reactions brings the model predictions closer to experimental observations for OOQOOH and HPMF, while increasing the rate coefficient for the QOOH $\rightarrow$ 2 CH 2 O + OH reaction is needed to improve the predictions of formaldehyde. In conclusion, to aid future quantification of DME oxidation intermediates by photoionization mass spectrometry, we report experimentally determined ionization cross-sections for ROO, OOQOOH, and HPMF.

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

Comparing different density-matrix expansions for long-range pion exchange

Empirical energy density functionals (EDFs) are generally successful in describing nuclear properties across the table of nuclides. But their limitations motivate using the density-matrix expansion (DME) to embed long-range pion interactions into a Skyrme functional. Recent results on the impact of the pion were both encouraging and puzzling, necessitating a careful re-examination of the DME implementation. In this study, we take the first steps, focusing on two-body scalar terms in the DME. Exchange energies with long-range one-pion contributions are well approximated by all DME implementations considered, with preference for variants that do not truncate at two derivatives in every EDF term. The use of the DME for chiral pion contributions is therefore supported by this investigation. For scalar-isovector energies it is important to treat neutrons and protons separately. The results are found to apply under broad conditions, although self-consistency is not yet tested.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

H2A.X promotes endosperm-specific DNA methylation in Arabidopsis thaliana

Background: H2A.X is an H2A variant histone in eukaryotes, unique for its ability to respond to DNA damage, initiating the DNA repair pathway. H2A.X replacement within the histone octamer is mediated by the FAcilitates Chromatin Transactions (FACT) complex, a key chromatin remodeler. FACT is required for DEMETER (DME)-mediated DNA demethylation at certain loci in Arabidopsis thaliana female gametophytes during reproduction. Here, we sought to investigate whether H2A.X is involved in DME- and FACT-mediated DNA demethylation during reproduction. Results: H2A.X is encoded by two genes in Arabidopsis genome, HTA3 and HTA5. We generated h2a.x double mutants, which displayed a normal growth profile, whereby flowering time, seed development, and root tip organization, S-phase progression and proliferation were all normal. However, h2a.x mutants were more sensitive to genotoxic stress, consistent with previous reports. H2A.X fused to Green Fluorescent Protein (GFP) under the H2A.X promoter was highly expressed especially in newly developing Arabidopsis tissues, including in male and female gametophytes, where DME is also expressed. We examined DNA methylation in h2a.x developing seeds and seedlings using whole genome bisulfite sequencing, and found that CG DNA methylation is decreased genome-wide in h2a.x mutant endosperm. Hypomethylation was most striking in transposon bodies, and occurred on both parental alleles in the developing endosperm, but not the embryo or seedling. h2a.x-mediated hypomethylated sites overlapped DME targets, but also included other loci, predominately located in heterochromatic transposons and intergenic DNA. Conclusions: Our genome-wide methylation analyses suggest that H2A.X could function in preventing access of the DME demethylase to non-canonical sites. Overall, our data suggest that H2A.X is required to maintain DNA methylation homeostasis in the unique chromatin environment of the Arabidopsis endosperm.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

CMI Winter Meeting 2025 Presentation

Lanthanides are important to many technologies including magnets used in high efficiency traction motors. While common in the environment and industrial waste streams, lanthanides are often present at very low concentrations. This work demonstrates synergistic lanthanide recovery from an aqueous magnet leachate to single ppm concentrations using Na2SO4 addition and subsequent DME-FC treatment. It was found that combining DME-FC with low concentrations of Na2SO4 (~0.1 M) results in synergistic isolation of lanthanides while making use of Na2SO4, an excessive byproduct of hydrometallurgical metal production. Combined Na2SO4 + DME reduced lanthanide metal ion's (Pr, Nd, Sm, Gd, Dy, and Ho) solubilities by 1,000 - 25,000x with final concentrations ranging from 2 ppm to 200 ppm. This can be compared to 0.1 M Na2SO4 alone providing a 10 - 200x reduction and DME providing a 100 - 1,500x reduction in lanthanide solubilities. Final solution concentrations of lanthanides were 99.8% lower than what could not be achieved with either individual process. The results also reveal different periodic trends in the solubility reduction for DME and Na2SO4.

37 - INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL C↗
DOE OSTI2024

SHOCK TUBE IGNITION STUDIES OF RENEWABLE DIESEL FUELS FOR MEDIUM AND HEAVY-DUTY TRANSPORTATION

Currently extensive research on alternative fuels is being conducted due to their increasing demand to reduce greenhouse emissions. One renewable fuel studied in this work is dimethyl ether (DME) blended with propane(C3H8) as a potential mixture for heavy-duty engines used in semi-trucks. The blend has the potential to drastically reduce particulate and greenhouse gas emissions compared to a conventional diesel engine operating under similar conditions. To develop the use of mixture, one must conduct detailed conceptual and simulation studies before progressing to detail studies in CFD, engine modifications, and live testing. For simulations, accurate high-fidelity chemical kinetic models are necessary. However, the validity of the chemical kinetic mechanism for operating conditions of a heavy-duty mixing-controlled compression (MCCI) engine was widely unknown until recent work presented here and published. In this work, we studied the ignition of DME and propane blends in a shock tube under MCCI engine conditions. Ignition delay time (IDT) gathered behind the reflected shock for DME-propane mixtures for heavy-duty compression ignition (CI) engine parameters. Testing was conducted for undiluted varieties spanning from temperatures of 700 to 1100 K at pressures ranging from 55 to 84 bar for various blends (100% CH3OCH3, 100% C3H8, 60% CH3OCH3/ 40% C3H8) of DME and propane were combusted in synthetic air (21% O2/ 79% N2). Several experiments were conducted at higher pressures (90-120 bar) to improve the model performance and accuracy. The ignition delay times (IDTs) were compared to recent mechanisms, including Aramco3.0, NUIG, and Dames et al. A common trend among the mechanisms was overpredicted experimental IDTs. Further studies were conducted by a sensitivity analysis using the Dames et al. model, and critical reactions sensitive to IDTs of DME-propane mixture near 60 bar are outlined. Chemical analysis was conducted on the NTC region to explain chemical kinetics which is critical for developing MCCI heavy duty engines.

Mohammed, Zuhayr Pasha↗
DOE OSTI2023

Ultra-thin ZrO 2 overcoating on CuO-ZnO-Al 2 O 3 catalyst by atomic layer deposition for improved catalytic performance of CO 2 hydrogenation to dimethyl ether

Abstract An ultra-thin overcoating of zirconium oxide (ZrO 2 ) film on CuO-ZnO-Al 2 O 3 (CZA) catalysts by atomic layer deposition (ALD) was proved to enhance the catalytic performance of CZA/HZSM-5 (H form of Zeolite Socony Mobil-5) bifunctional catalysts for hydrogenation of CO 2 to dimethyl ether (DME). Under optimal reaction conditions (i.e. 240 °C and 2.8 MPa), the yield of product DME increased from 17.22% for the bare CZA/HZSM-5 catalysts, to 18.40% for the CZA catalyst after 5 cycles of ZrO 2 ALD with HZSM-5 catalyst. All the catalysts modified by ZrO 2 ALD displayed significantly improved catalytic stability of hydrogenation of CO 2 to DME reaction, compared to that of CZA/HZSM-5 bifunctional catalysts. The loss of DME yield in 100 h of reaction was greatly mitigated from 6.20% (loss of absolute value) to 3.01% for the CZA catalyst with 20 cycles of ZrO 2 ALD overcoating. Characterizations including hydrogen temperature programmed reduction, x-ray powder diffraction, and x-ray photoelectron spectroscopy revealed that there was strong interaction between Cu active centers and ZrO 2 .

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

Lanthanide Sulfate Recovery by Synergistic Dimethyl Ether and Na 2 SO 4 Fractional Crystallization

Lanthanides (Lns) are important to many technologies including magnets used in high-efficiency traction motors and generators. While commonly occurring in the environment and industrial waste streams, Ln are generally present at low concentrations. This work demonstrates synergistic Ln recovery from an aqueous magnet leachate to single ppm concentrations using Na 2 SO 4 addition and subsequent dimethyl ether-driven fractional crystallization (DME-FC) treatment. It is found that combining DME-FC with low concentrations of Na 2 SO 4 (≈0.1 M) results in synergistic isolation of Lns while making use of Na 2 SO 4 , an excessive byproduct of hydrometallurgical metal production. Combined Na 2 SO 4 + DME reduces Ln metal ion (Pr, Nd, Sm, Gd, Dy, and Ho) solubilities by 700–27,000x with final concentrations ranging from 2 ppm to 200 ppm. Separately, Na 2 SO 4 0.1 M provides a 10–200x reduction and DME provides a 90–1,400x reduction in Ln solubilities. Final Ln concentrations of the combined process are 99.8% lower than what is achieved with each individual process.

dimethyl ether↗