Showing papers by "ExxonMobil published in 2020"
TL;DR: A family of robust tetraamine-functionalized frameworks that retain cooperativity are reported, leading to the potential for exceptional efficiency in capturing CO2 under the extreme conditions relevant to natural gas flue emissions.
Abstract: Natural gas has become the dominant source of electricity in the United States, and technologies capable of efficiently removing carbon dioxide (CO2) from the flue emissions of natural gas-fired power plants could reduce their carbon intensity. However, given the low partial pressure of CO2 in the flue stream, separation of CO2 is particularly challenging. Taking inspiration from the crystal structures of diamine-appended metal-organic frameworks exhibiting two-step cooperative CO2 adsorption, we report a family of robust tetraamine-functionalized frameworks that retain cooperativity, leading to the potential for exceptional efficiency in capturing CO2 under the extreme conditions relevant to natural gas flue emissions. The ordered, multimetal coordination of the tetraamines imparts the materials with extraordinary stability to adsorption-desorption cycling with simulated humid flue gas and enables regeneration using low-temperature steam in lieu of costly pressure or temperature swings.
194 citations
TL;DR: Spirocyclic polymers with N-aryl bonds that demonstrated noninterconnected microporosity in the absence of ladder linkages are created that offer potential for the hybridization of energy-efficient technology with conventional processes such as distillation.
Abstract: The fractionation of crude-oil mixtures through distillation is a large-scale, energy-intensive process. Membrane materials can avoid phase changes in such mixtures and thereby reduce the energy intensity of these thermal separations. With this application in mind, we created spirocyclic polymers with N-aryl bonds that demonstrated noninterconnected microporosity in the absence of ladder linkages. The resulting glassy polymer membranes demonstrated nonthermal membrane fractionation of light crude oil through a combination of class- and size-based "sorting" of molecules. We observed an enrichment of molecules lighter than 170 daltons corresponding to a carbon number of 12 or a boiling point less than 200°C in the permeate. Such scalable, selective membranes offer potential for the hybridization of energy-efficient technology with conventional processes such as distillation.
113 citations
22 Jun 2020
TL;DR: In this paper, the authors used the Microscopy Service of the UPV for the TEM and STEM measurements in the CLAESS beamline of the ALBA synchrotron.
Abstract: This work was supported by the European Union through the European Research Council (grant ERC-AdG-2014-671093, SynCatMatch) and the Spanish government through the "Severo Ochoa Program" (SEV-2016-0683). L.L. thanks the ITQ for providing a contract. The authors also thank the Microscopy Service of the UPV for the TEM and STEM measurements. The XAS measurements were carried out in the CLAESS beamline of the ALBA synchrotron. We thank Giovanni Agostini for his kind support in the analysis of XAS data. HR-HAADF-STEM measurements were performed at DME-UCA at Cadiz University with financial support from FEDER/MINECO (MAT2017-87579-R and MAT2016-81118-P). C.W.L. thanks CAPES (Science without Frontiers -Process no. 13191/13-6) for a predoctoral fellowship. The financial support from ExxonMobil for this project is also greatly acknowledged.
109 citations
TL;DR: In this article, asphaltene science had been hindered by many significant uncertainties regarding molecular weight, molecular structure, and nanocolloidal characteristics in laboratory solvents and crud.
Abstract: Previously, asphaltene science had been hindered by many significant uncertainties regarding molecular weight, molecular structure, and nanocolloidal characteristics in laboratory solvents and crud...
95 citations
25 Oct 2020
TL;DR: A Tensorflow/Keras based library is designed which allows automatic conversion of non-streaming models to streaming ones with minimum effort and also explores novel KWS models with multi-head attention which reduce the classification error over the state-of-art by 10% on Google speech commands data sets V2.
Abstract: In this work we explore the latency and accuracy of keyword spotting (KWS) models in streaming and non-streaming modes on mobile phones. NN model conversion from non-streaming mode (model receives the whole input sequence and then returns the classification result) to streaming mode (model receives portion of the input sequence and classifies it incrementally) may require manual model rewriting. We address this by designing a Tensorflow/Keras based library which allows automatic conversion of non-streaming models to streaming ones with minimum effort. With this library we benchmark multiple KWS models in both streaming and non-streaming modes on mobile phones and demonstrate different tradeoffs between latency and accuracy. We also explore novel KWS models with multi-head attention which reduce the classification error over the state-of-art by 10% on Google speech commands data sets V2. The streaming library with all experiments is open-sourced.
86 citations
TL;DR: In petroleum science, asphaltenes are well-known as the most refractory fraction of crude oil and remain infamous for problems in production, transportation, and refining processes as discussed by the authors.
Abstract: In petroleum science, asphaltenes are well-known as the most refractory fraction of crude oil and remain infamous for problems in production, transportation, and refining processes. Hence, they hav...
79 citations
Technical University of Berlin1, École Polytechnique Fédérale de Lausanne2, Ghent University3, University of Waterloo4, Leiden University5, Augsburg College6, University of Michigan7, National Institute of Advanced Industrial Science and Technology8, Monash University9, ExxonMobil10, University of Bordeaux11, Centre national de la recherche scientifique12, University of Zaragoza13
TL;DR: The current challenges of assessing impacts of resource use in LCA have been addressed by defining the safeguard subject for mineral resources, formulating key questions related to this safeguard subject, recommending existing LCIA methods in relation to these questions, and highlighting areas for future method development.
Abstract: Assessing impacts of abiotic resource use has been a topic of
persistent debate among life cycle impact assessment (LCIA) method developers
and a source of confusion for life cycle assessment (LCA) practitioners
considering the different interpretations of the safeguard subject for mineral
resources and the resulting variety of LCIA methods to choose from. Based on the
review and assessment of 27 existing LCIA methods, accomplished in the first
part of this paper series (Sonderegger et al. 2020), this paper provides recommendations regarding the
application-dependent use of existing methods and areas for future method
development. Within the “global guidance for LCIA indicators and
methods” project of the Life Cycle Initiative hosted by UN Environment,
62 members of the “task force mineral resources” representing
different stakeholders discussed the strengths and limitations of existing LCIA
methods and developed initial conclusions. These were used by a subgroup of
eight members at the Pellston Workshop® held in Valencia, Spain, to
derive recommendations on the application-dependent use and future development
of impact assessment methods. First, the safeguard subject for mineral resources within the area
of protection (AoP) natural resources was defined. Subsequently, seven key
questions regarding the consequences of mineral resource use were formulated,
grouped into “inside-out” related questions (i.e., current
resource use leading to changes in opportunities for future users to use
resources) and “outside-in” related questions (i.e., potential
restrictions of resource availability for current resource users). Existing LCIA
methods were assigned to these questions, and seven methods
(ADPultimate reserves, SOPURR,
LIME2endpoint, CEENE, ADPeconomic reserves, ESSENZ, and GeoPolRisk) are recommended for use in
current LCA studies at different levels of recommendation. All 27 identified
LCIA methods were tested on an LCA case study of an electric vehicle, and
yielded divergent results due to their modeling of impact mechanisms that
address different questions related to mineral resource use. Besides
method-specific recommendations, we recommend that all methods increase the
number of minerals covered, regularly update their characterization factors, and
consider the inclusion of secondary resources and anthropogenic stocks.
Furthermore, the concept of dissipative resource use should be defined and
integrated in future method developments. In an international consensus-finding process, the current
challenges of assessing impacts of resource use in LCA have been addressed by
defining the safeguard subject for mineral resources, formulating key questions
related to this safeguard subject, recommending existing LCIA methods in
relation to these questions, and highlighting areas for future method
development.
79 citations
TL;DR: It is reported that positively charged cobalt complexes, stabilized by chelating phosphine ligands, show higher activities at lower pressures than their neutral counterparts, approaching the activities of precious rhodium catalysts.
Abstract: The cobalt complexes HCo(CO)4 and HCo(CO)3(PR3) were the original industrial catalysts used for the hydroformylation of alkenes through reaction with hydrogen and carbon monoxide to produce aldehydes. More recent and expensive rhodium-phosphine catalysts are hundreds of times more active and operate under considerably lower pressures. Cationic cobalt(II) bisphosphine hydrido-carbonyl catalysts that are far more active than traditional neutral cobalt(I) catalysts and approach rhodium catalysts in activity are reported here. These catalysts have low linear-to-branched (L:B) regioselectivity for simple linear alkenes. However, owing to their high alkene isomerization activity and increased steric effects due to the bisphosphine ligand, they have high L:B selectivities for internal alkenes with alkyl branches. These catalysts exhibit long lifetimes and substantial resistance to degradation reactions.
78 citations
TL;DR: The in situ determination of solvated 2D COF structures, which exhibit obvious difference as compared to that of the same COF under dried state, and suggest new opportunities for the applications of COF materials under wet conditions.
Abstract: Layer-stacking structures are very common in two-dimensional covalent organic frameworks (2D COFs). While their structures are normally determined under solvent-free conditions, the structures of solvated 2D COFs are largely unexplored. We report herein the in situ determination of solvated 2D COF structures, which exhibit an obvious difference as compared to that of the same COF under dried state. Powder X-ray diffraction (PXRD) data analyses, computational modeling, and Pawley refinement indicate that the solvated 2D COFs experience considerable interlayer shifting, resulting in new structures similar to the staggered AB stacking, namely, quasi-AB-stacking structures, instead of the AA-stacking structures that are usually observed in the dried COFs. We attribute this interlayer shifting to the interactions between COFs and solvent molecules, which may weaken the attraction strength between adjacent COF layers. Density functional theory (DFT) calculations confirm that the quasi-AB stacking is energetically preferred over the AA stacking in solvated COFs. All four highly crystalline 2D COFs examined in the present study exhibit considerable interlayer shifting upon solvation, implying the universality of the solvent-induced interlayer stacking rearrangement in 2D COFs. These findings prompt re-examination of the 2D COF structures in solvated state and suggest new opportunities for the applications of COF materials under wet conditions.
73 citations
TL;DR: It is shown that one-dimensional intergrowths of zeolite MEL enable selectivity by formation of more rigid pores by creating more rigid and highly selective pores compared to pristine MFI nanosheets.
Abstract: Zeolite MFI is a widely used catalyst and adsorbent that also holds promise as a thin-film membrane. The discovery of nanometre-thick two-dimensional (2D) MFI nanosheets has facilitated methods for thin-film zeolite fabrication that open new horizons for membrane science and engineering. However, the crystal structure of 2D-MFI nanosheets and their relationship to separation performance remain elusive. Using transmission electron microscopy, we find that one- to few-unit-cell-wide intergrowths of zeolite MEL exist within 2D-MFI. We identify the planar distribution of these 1D or near-1D-MEL domains, and show that a fraction of nanosheets have high (~25% by volume) MEL content while the majority of nanosheets are MEL-free. Atomistic simulations show that commensurate knitting of 1D-MEL within 2D-MFI creates more rigid and highly selective pores compared to pristine MFI nanosheets, and permeation experiments show a separation factor of 60 using an industrially relevant (undiluted 1 bar xylene mixture) feed. Confined growth in graphite is shown to increase the MEL content in MFI nanosheets. Our observation of these intergrowths suggests strategies for the development of ultra-selective zeolite membranes. Two-dimensional zeolite MFI nanosheets show ultra-selective separation of xylene isomers, but it was not known why this occurs. Here, using electron microscopy and atomistic simulation, it is shown that one-dimensional intergrowths of zeolite MEL enable selectivity by formation of more rigid pores.
72 citations
TL;DR: A novel probabilistic fault detection and identification method is proposed which adopts a newly developed deep learning approach using Bayesian recurrent neural networks~(BRNNs) with variational dropout which yields uncertainty estimates which allow for simultaneous fault detection of chemical processes, direct fault identification, and fault propagation analysis.
University of Texas at Austin1, University of Wisconsin-Madison2, Massachusetts Institute of Technology3, University of Kansas4, California Institute of Technology5, American Hereford Association6, Spanish National Research Council7, University of La Laguna8, Los Alamos National Laboratory9, AmeriCorps VISTA10, University of Hong Kong11, University of California, San Diego12, University of Bern13, Max Planck Society14, Smithsonian Institution15, University of North Carolina at Chapel Hill16, University of Arizona17, Dartmouth College18, University of California, Los Angeles19, Bishop's University20, Technical University of Denmark21, Princeton University22, Ames Research Center23, University of Michigan24, Université de Montréal25, Search for extraterrestrial intelligence26, NASA Exoplanet Science Institute27, Goddard Space Flight Center28, University of New Mexico29, University of California, Berkeley30, University of Tokyo31, Ithaca College32, Cornell University33, University of California, Riverside34, Moorpark College35, Lehigh University36, Fisk University37, Vanderbilt University38, ExxonMobil39
TL;DR: These findings for the WD 1856+534 system indicate that giant planets can be scattered into tight orbits without being tidally disrupted, motivating the search for smaller transiting planets around white dwarfs.
Abstract: Astronomers have discovered thousands of planets outside the Solar System1, most of which orbit stars that will eventually evolve into red giants and then into white dwarfs. During the red giant phase, any close-orbiting planets will be engulfed by the star2, but more distant planets can survive this phase and remain in orbit around the white dwarf3,4. Some white dwarfs show evidence for rocky material floating in their atmospheres5, in warm debris disks6–9 or orbiting very closely10–12, which has been interpreted as the debris of rocky planets that were scattered inwards and tidally disrupted13. Recently, the discovery of a gaseous debris disk with a composition similar to that of ice giant planets14 demonstrated that massive planets might also find their way into tight orbits around white dwarfs, but it is unclear whether these planets can survive the journey. So far, no intact planets have been detected in close orbits around white dwarfs. Here we report the observation of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days. We observed and modelled the periodic dimming of the white dwarf caused by the planet candidate passing in front of the star in its orbit. The planet candidate is roughly the same size as Jupiter and is no more than 14 times as massive (with 95 per cent confidence). Other cases of white dwarfs with close brown dwarf or stellar companions are explained as the consequence of common-envelope evolution, wherein the original orbit is enveloped during the red giant phase and shrinks owing to friction. In this case, however, the long orbital period (compared with other white dwarfs with close brown dwarf or stellar companions) and low mass of the planet candidate make common-envelope evolution less likely. Instead, our findings for the WD 1856+534 system indicate that giant planets can be scattered into tight orbits without being tidally disrupted, motivating the search for smaller transiting planets around white dwarfs. A giant planet candidate roughly the size of Jupiter but more than 14 times as massive is observed by TESS and other instruments to be transiting the white dwarf star WD 1856+534.
03 Jan 2020
TL;DR: The article as mentioned in this paper contains sections titled:==================@@@@@@@@@@@@@@@@@@@@@@@@````============�₷1.1.2.3.4.5.6.
Abstract: The article contains sections titled:
1. Acrylic Acid and Esters
1.1. Physical Properties
1.2. Chemical Properties
1.3. Production
1.3.1. Propene Oxidation
1.3.2. Esterification
1.4. Quality Specifications and Analysis
1.5. Storage and Transportation
1.6. Uses
1.7. Some Special Acrylates
1.8. Economic Aspects
1.9. Toxicology and Occupational Health
2. Cyanoacrylates
3. Acrylamide
TL;DR: In this paper, the authors comprehensively review the CO2 sequestration process in saline aquifers and evaluate the storage mechanisms including structural, residual, solubility, and mineral trappings along with their relative contributions, and their key parameters and optimisations.
TL;DR: This paper applied real-space single molecule imaging non-contact atomic force microscopy to obtain exact structures of individual molecules, and compared the results from other characterization techniques to validate some of the previously hypothesized average structures.
University of Texas at Austin1, University of Wisconsin-Madison2, Massachusetts Institute of Technology3, University of Kansas4, California Institute of Technology5, American Hereford Association6, University of La Laguna7, Spanish National Research Council8, Los Alamos National Laboratory9, AmeriCorps VISTA10, University of Hong Kong11, University of California, San Diego12, University of Bern13, Smithsonian Institution14, Max Planck Society15, University of North Carolina at Chapel Hill16, University of Arizona17, Dartmouth College18, University of California, Los Angeles19, Bishop's University20, Technical University of Denmark21, Princeton University22, Ames Research Center23, University of Michigan24, Université de Montréal25, Search for extraterrestrial intelligence26, NASA Exoplanet Science Institute27, Goddard Space Flight Center28, University of New Mexico29, University of California, Berkeley30, University of Tokyo31, Cornell University32, Ithaca College33, University of California, Riverside34, Moorpark College35, Lehigh University36, Vanderbilt University37, Fisk University38, ExxonMobil39
TL;DR: In this paper, the discovery of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days was reported.
Abstract: Astronomers have discovered thousands of planets outside the solar system, most of which orbit stars that will eventually evolve into red giants and then into white dwarfs. During the red giant phase, any close-orbiting planets will be engulfed by the star, but more distant planets can survive this phase and remain in orbit around the white dwarf. Some white dwarfs show evidence for rocky material floating in their atmospheres, in warm debris disks, or orbiting very closely, which has been interpreted as the debris of rocky planets that were scattered inward and tidally disrupted. Recently, the discovery of a gaseous debris disk with a composition similar to ice giant planets demonstrated that massive planets might also find their way into tight orbits around white dwarfs, but it is unclear whether the planets can survive the journey. So far, the detection of intact planets in close orbits around white dwarfs has remained elusive. Here, we report the discovery of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days. The planet candidate is roughly the same size as Jupiter and is no more than 14 times as massive (with 95% confidence). Other cases of white dwarfs with close brown dwarf or stellar companions are explained as the consequence of common-envelope evolution, wherein the original orbit is enveloped during the red-giant phase and shrinks due to friction. In this case, though, the low mass and relatively long orbital period of the planet candidate make common-envelope evolution less likely. Instead, the WD 1856+534 system seems to demonstrate that giant planets can be scattered into tight orbits without being tidally disrupted, and motivates searches for smaller transiting planets around white dwarfs.
TL;DR: The rates of catalytic oxidation of cyclohexane and CO were 4 and 20 times higher, respectively, with Cu supported on a cerium-based metal-organic framework (MOF) than on the structurally analogous MOF.
Abstract: The rates of catalytic oxidation of cyclohexane and CO are 4 and 20 times higher, respectively, with Cu supported on a cerium-based metal–organic framework (MOF) than on the structurally analogous ...
TL;DR: In this article, a micromechanical force measurement apparatus was used to explore the interaction between waxes and hydrates, both surface-deposited and dissolved in the bulk phase, and those which have been treated with anti-agglomerant chemicals.
05 Aug 2020-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the behavior of CrCoFeMnNi high-entropy alloy (Cantor) during cyclic deformation at room temperature was compared with those of a twinning-induced plasticity (TWIP) steel and 304 stainless steel (SS304).
Abstract: The behavior of CrCoFeMnNi high-entropy alloy (Cantor) during cyclic deformation at room temperature was compared with those of a twinning-induced plasticity (TWIP) steel and 304 stainless steel (SS304). The three materials with similar grain sizes (~65 μm) were made by controlled heat treatment and tested to evaluate tensile and low-cycle fatigue (LCF) properties. The tensile strength and ductility of Cantor were much lower than those of TWIP steel and SS304. Cantor and TWIP steel revealed cyclic hardening and then softening; SS304 showed secondary hardening at the latest stage of cyclic deformation due to formation of α′-martensite, which led to a significant decrease in its LCF life. At high total strain amplitudes >0.4% LCF life was longer in Cantor than in SS304, but shorter than in TWIP steel. However, at total strain amplitudes ≤0.4%, Cantor showed the shortest LCF life. It was found that the Coffin-Manson plot of Cantor followed the trend of TWIP steel rather than that of SS304. Microstructural analysis of the Cantor with increasing cycles revealed the formation of twins and well-defined cell structures, the latter of which is the evidence of wavy slip.
TL;DR: In this paper, a series of polybenzimidazoles based on a tetraaminodiphenylsulfone (TADPS) monomer have been characterized at temperatures from 35 to 190°C.
TL;DR: C2+ n-alkane gases (ethane, propane, butane, and pentane) are initially produced by irreversible cracking chemistry, but, as thermal maturity increases, the isotopic distribution of these species approaches thermodynamic equilibrium, becoming indistinguishable from equilibrium in the most thermally mature gases.
Abstract: Natural gas is a key energy resource, and understanding how it forms is important for predicting where it forms in economically important volumes. However, the origin of dry thermogenic natural gas is one of the most controversial topics in petroleum geochemistry, with several differing hypotheses proposed, including kinetic processes (such as thermal cleavage, phase partitioning during migration, and demethylation of aromatic rings) and equilibrium processes (such as transition metal catalysis). The dominant paradigm is that it is a product of kinetically controlled cracking of long-chain hydrocarbons. Here we show that C2+n-alkane gases (ethane, propane, butane, and pentane) are initially produced by irreversible cracking chemistry, but, as thermal maturity increases, the isotopic distribution of these species approaches thermodynamic equilibrium, either at the conditions of gas formation or during reservoir storage, becoming indistinguishable from equilibrium in the most thermally mature gases. We also find that the pair of CO2 and C1 (methane) exhibit a separate pattern of mutual isotopic equilibrium (generally at reservoir conditions), suggesting that they form a second, quasi-equilibrated population, separate from the C2 to C5 compounds. This conclusion implies that new approaches should be taken to predicting the compositions of natural gases as functions of time, temperature, and source substrate. Additionally, an isotopically equilibrated state can serve as a reference frame for recognizing many secondary processes that may modify natural gases after their formation, such as biodegradation.
TL;DR: In this article, the authors present a system-scale energy analysis tool, the Sustainable Energy System Analysis Modelling Environment (SESAME), to assess the pathway and system-level GHG emissions of today's changing energy system.
TL;DR: The present review is intended to help demystify the ecotoxicity of IOCs and provide recommendations for their hazard and risk assessment.
Abstract: Ionizable organic chemicals (IOCs) such as organic acids and bases are an important substance class requiring aquatic hazard evaluation. While the aquatic toxicity of IOCs is highly dependent on the water pH, many toxicity studies in the literature cannot be interpreted because pH was not reported or not kept constant during the experiment, calling for an adaptation and improvement of testing guidelines. The modulating influence of pH on toxicity is mainly caused by pH-dependent uptake and bioaccumulation of IOCs, which can be described by ion-trapping and toxicokinetic models. The internal effect concentrations of IOCs were found to be independent of the external pH due to organisms' and cells' ability to maintain a stable internal pH milieu. If the external pH is close to the internal pH, existing Quantitative Structure-Activity Relationships (QSAR) for neutral organics can be adapted by substituting the octanol-water partition coefficient by the ionization-corrected liposome-water distribution ratio as the hydrophobicity descriptor, demonstrated by modification of the target lipid model. Charged, zwitterionic and neutral species of an IOC can all contribute to observed toxicity, either through concentration-additive mixture effects or by interaction of different species, as is the case for uncoupling of mitochondrial respiration. For specifically acting IOCs, we recommend a two-step screening procedure with ion-trapping/QSAR models used to predict the baseline toxicity, followed by adjustment using the toxic ratio derived from in vitro systems. Receptor or plasma binding models also show promise for elucidating IOC toxicity. This review is intended to help demystify ecotoxicity of IOCs and provide recommendations for their hazard and risk assessment. This article is protected by copyright. All rights reserved.
TL;DR: A critical review examines current practices for UVCB risk assessment and reveals a need for a multipronged and transparent approach integrating whole‐substance and constituent‐based information.
Abstract: Substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs) pose unique risk assessment challenges to regulators and to product registrants. These substances can contain many constituents, sometimes partially unknown and/or variable, depending on fluctuations in their source material and/or manufacturing process. International regulatory agencies have highlighted the difficulties in characterizing UVCBs and assessing their toxicity and environmental fate. Several industrial sectors have attempted to address these issues by developing frameworks and characterization methods. Based on the output of a 2016 workshop, this critical review examines current practices for UVCB risk assessment and reveals a need for a multipronged and transparent approach integrating whole-substance and constituent-based information. In silico tools or empirical measurements can provide information on discrete and/or blocks of UVCB constituents with similar hazard properties. Read-across and/or whole-substance toxicity and fate testing using adapted emerging methods can provide whole-substance information. Continued collaboration of stakeholders representing government, industry, and academia will facilitate the development of practical testing strategies and guidelines for addressing regulatory requirements for UVCBs. Environ Toxicol Chem 2020;39:2097-2108. © 2020 Health and Environmental Sciences Institute. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
TL;DR: In this article, a systematic study of water adsorption isotherms of zeolite 3A and 4A crystals was carried out over a pressure range of 10-5 to 10-1 bar and temperatures from 25 °C to 250 °C.
Abstract: A systematic study of water adsorption isotherms of zeolite 3A and 4A crystals was carried out over a pressure range of 10-5 to 10-1 bar and temperatures from 25 °C to 250 °C. This work focuses on ...
TL;DR: In this article, stable isotopes including methane clumped-isotope measurements were applied to solution and associated gases from several producing fields in the U.S. Gulf of Mexico to estimate the proportions, properties and origins of microbial and thermogenic endmembers.
TL;DR: Screening of publicly available metagenomes revealed that Sulfurimonas spp.
Abstract: Sulfur-oxidizing Sulfurimonas spp. are widespread in sediments, hydrothermal vent fields, aquifers and subsurface environments such as oil reservoirs where they play an important role in the sulfur cycle. We determined the genome sequence of the oil field isolate Sulfurimonas sp. strain CVO and compared its gene expression during nitrate-dependent sulfide oxidation to the coastal sediment isolate Sulfurimonas denitrificans. Formation of elemental sulfur (S0 ) and high expression of sulfide quinone oxidoreductase (SQR) genes indicates that sulfide oxidation in both strains is mediated by SQR. Subsequent oxidation of S0 was achieved by the sulfur oxidation enzyme complex (SOX). In the coastal S. denitrificans, the genes are arranged and expressed as two clusters: soxXY1 Z1 AB and soxCDY2 Z2 H, and sulfate was the sole metabolic end product. By contrast, the oil field strain CVO has only the soxCDY2 Z2 H cluster and not soxXY1 Z1 AB. Despite the absence of the soxXY1 Z1 AB cluster, strain CVO oxidized S0 to thiosulfate and sulfate, demonstrating that soxCDY2 Z2 H genes alone are sufficient for S0 oxidation in Sulfurimonas spp. and that thiosulfate is an additional metabolic end product. Screening of publicly available metagenomes revealed that Sulfurimonas spp. with only the soxCDY2 Z2 H cluster are widespread suggesting this mechanism of thiosulfate formation is environmentally significant.
TL;DR: This work expands the existing guidances designed for pharmaceutical applications by recommending additional elements that are relevant to environmental chemicals that can be adopted and customized by public health agencies receiving PBPK model submission and can serve as general guidance for submitting P BPK-related studies for publication in journals or other modeling sharing purposes.
TL;DR: An example of a nonaqueous flow cell electrolyzer with [Ni(cyclam)]2+ as the homogeneous electrocatalyst for CO2 reduction using ferrocene as a sacrificial electron donor and ammonium salts as both electrolyte and proton donor is presented.
Abstract: A significant number of molecular catalysts have been developed for electrochemical CO2 reduction with high efficiency and selectivity; however, testing of these electrocatalysts in an application-ready system is lacking. Here, we present an example of a nonaqueous flow cell electrolyzer with [Ni(cyclam)]2+ as the homogeneous electrocatalyst for CO2 reduction. Using ferrocene as a sacrificial electron donor and ammonium salts as both electrolyte and proton donor, efficient catalytic CO2 reduction is achieved. The nonaqueous design shows high selectivity for the reduction of CO2 to CO (>80%) and achieves high current densities with a graphite felt working electrode (up to 50 mA·cm-2 with 0.5 M proton donor in MeCN solution), producing >40 mL·h-1 of CO. The choice of a molecular electrocatalyst, solvent, and proton donor are the key factors for achieving high activity with an efficient flow electrolyzer and the eventual development of a viable continuous process.