Recent Submissions

  • Barcoding Amino Acids for Mutation Screening in Amyloid Beta Peptides

    Hoang, Phuong Mai; Khashab, Niveen M. (Small Methods, Wiley, 2019-10-04) [Article]
    Amino acid (AA) substitutions are directly correlated with specific pathologies such as Alzheimer's disease, making their rapid screening and detection critical to treatment and scientific study. A proof-of-concept implementation of the label-free and noninvasive Raman spectroscopy technique for the detection of AA substitutions in primary peptide fragments is demonstrated. By encoding the Raman “fingerprint” of individual AAs into binary formats called optical identification tags (OITs), a library of identifiers is created, which can then be used for detecting mutations. When the recorded Raman signal is enhanced by using surface-enhanced Raman scattering substrate, the mutation screening strategy can detect a single point missense mutation in an 11-AA peptide fragment of amyloid beta Aβ(25–35) and a frameshift mutation in a 42-AA fragment Aβ(1–42) down to picomolar concentrations. The combination of high sensitivity and simple operation makes the use of OITs a promising approach for high-throughput automated screening.
  • 3D Analysis of Ordered Porous Polymeric Particles using Complementary Electron Microscopy Methods

    Alvarez, Juan; Saudino, Giovanni; Musteata, Valentina-Elena; Madhavan, Poornima; Genovese, Alessandro; Behzad, Ali Reza; Sougrat, Rachid; Boi, Cristiana; Peinemann, Klaus-Viktor; Nunes, Suzana Pereira (Scientific Reports, Springer Science and Business Media LLC, 2019-09-27) [Article]
    Highly porous particles with internal triply periodic minimal surfaces were investigated for sorption of proteins. The visualization of the complex ordered morphology requires complementary advanced methods of electron microscopy for 3D imaging, instead of a simple 2D projection: transmission electron microscopy (TEM) tomography, slice-and-view focused ion beam (FIB) and serial block face (SBF) scanning electron microscopy (SEM). The capability of each method of 3D image reconstruction was demonstrated and their potential of application to other synthetic polymeric systems was discussed. TEM has high resolution for details even smaller than 1 nm, but the imaged volume is relatively restricted (2.5 μm)3. The samples are pre-sliced in an ultramicrotome. FIB and SBF are coupled to a SEM. The sample sectioning is done in situ, respectively by an ion beam or an ultramicrotome, SBF, a method so far mostly applied only to biological systems, was particularly highly informative to reproduce the ordered morphology of block copolymer particles with 32-54 nm nanopores and sampling volume (20 μm)3.
  • Structure-activity relationships in metal organic framework derived mesoporous nitrogen-doped carbon containing atomically dispersed iron sites for CO2 electrochemical reduction

    Sun, Xiaohui; Wang, Riming; Ould-Chikh, Samy; Osadchii, Dmitrii; Li, Guanna; Aguilar, Antonio; Hazemann, Jean-louis; Kapteijn, Freek; Gascon, Jorge (Journal of Catalysis, Elsevier BV, 2019-09-25) [Article]
    Mesoporous nitrogen-doped carbon nanoparticles with atomically dispersed iron sites (named mesoNC-Fe) are synthesized via high-temperature pyrolysis of an Fe containing ZIF-8 MOF. Hydrolysis of tetramethyl orthosilicate (TMOS) in the MOF framework prior to pyrolysis plays an essential role in maintaining a high surface area during the formation of the carbon structure, impeding the formation of iron (oxide) nanoparticles. To gain inside on the nature of the resulting atomically dispersed Fe moieties, HERFD-XANES, EXAFS and valence-to-core X-ray emission spectroscopies have been used. The experimental spectra (both XAS and XES) combined with theoretical calculations suggest that iron has a coordination sphere including a porphyrinic environment and OH/H2O moieties responsible for the high activity in CO2 electroreduction. DFT calculations demonstrate that CO formation is favored in these structures because the free energy barriers of *COOH formation are decreased and the adsorption of *H is impeded. The combination of such a unique coordination environment with a high surface area in the carbon structure of mesoNC-Fe makes more active sites accessible during catalysis and promotes CO2 electroreduction.
  • Gas separation performance and mechanical properties of thermally-rearranged polybenzoxazoles derived from an intrinsically microporous dihydroxyl-functionalized triptycene diamine-based polyimide

    Yerzhankyzy, Ainur; Ghanem, Bader; Wang, Yingge; Alaslai, Nasser Y.; Pinnau, Ingo (Journal of Membrane Science, Elsevier BV, 2019-09-25) [Article]
    An intrinsically microporous hydroxyl-functionalized polyimide (PIM-PI) made from 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 2,6(7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH), was thermally converted to polybenzoxazole (PBO). The thermal rearrangement of the PIM-PI to PBO significantly increased the free volume, which was reflected by a boost in its microporosity as indicated by enhanced Brunauer-Emmett-Teller (BET) surface area from 167 to 405 m2 g−1. The increase in free volume noticeably improved the gas permeability but also resulted in reduced gas-pair selectivity. The fresh PBO membrane made by thermal treatment at 460 °C for 30 min (TRIP-TR-460-30) with a PBO conversion of 98% displayed a 20-fold higher CO2 permeability of 840 barrer than the initial value of 43 barrer for the 6FDA-DAT1-OH polyimide at the expense of ~ 60% decrease in pure-gas CO2/CH4 selectivity from 52 to 21. The TRIP-TR-460-30 PBO showed good performance for propylene/propane separation with pure-gas C3H6 permeability of 21 barrer and C3H6/C3H8 selectivity of 16 for a 28-days aged sample. When tested under mixed-gas conditions C3H6 permeability dropped to 12.8 barrer and C3H6/C3H8 selectivity of 8. TRIP-TR-460-30 PBO displayed mechanical properties comparable some rigid polyimides with tensile strength, Young's modulus and elongation at break of 58 MPa, 1.83 GPa and 4.3%, respectively.
  • Chemical kinetic study of triptane (2,2,3-trimethylbutane) as an anti-knock additive

    Atef, Nour; Issayev, Gani; Mohamed, Samah; Najjar, Ahmed; Wang, Zhandong; Wang, Jui-Yang; Farooq, Aamir; Sarathy, Mani (Combustion and Flame, Elsevier BV, 2019-09-19) [Article]
    2,2,3-Trimethylbutane (i.e., triptane) is a potential gasoline octane booster with a research octane number (RON) of 112. Recent studies showed that it can be catalytically produced with high selectivity from methanol (CH3OH) and dimethyl ether (DME), which presents a promising route for utilizing biomass derivatives as transportation fuels. Understanding the ignition properties of triptane at engine relevant conditions is crucial for its further evaluation. In this work, a detailed kinetic model for triptane combustion is developed and validated. The rate rules for the low-temperature oxidation reactions are evaluated based on quantum chemistry calculations from literature, and thermochemical properties of all the species are assessed based on new thermodynamic group values with careful treatment of gauche interactions. In addition, alternative isomerization pathways for peroxy-alkylhydroperoxide species (ȮOQOOH) are incorporated in the model. The model is validated against new ignition delay data from facilities at King Abdullah University of Science and Technology (KAUST): rapid compression machine (RCM) experiments at pressures of 20 and 40 bar, equivalence ratios of 0.5 and 1 and across a temperature range of 620 to 1015 K, and shock tube experiments at 2 and 5 bar, 0.5 and 1 equivalence ratio and over 1000–1400 K. Moreover, the model prediction of various species is compared against species profiles from jet stirred reactor experiments at three equivalence ratios (0.5, 1 and 2) at atmospheric pressure. Finally, triptane is compared with its less branched isomers, n-heptane and 2-methylhexane, to evaluate the effect of branching on fuel reactivity and importance of alternative isomerization pathway.
  • Electrostatically-coupled graphene oxide nanocomposite cation exchange membrane

    Alabi, Adetunji; Cseri, Levente; Al Hajaj, Ahmed; Szekely, Gyorgy; Budd, Peter; Zou, Linda (Journal of Membrane Science, Elsevier BV, 2019-09-07) [Article]
    We report the preparation of an electrostatically-coupled graphene oxide nanocomposite cation exchange membrane (CEM) based on sulfonic group containing graphene oxide (SGO) (45 wt % loading) and polyvinylidene fluoride (PVDF), where the ion exchange groups were provided by the SGO additive. SGO was prepared via the mixing of graphene oxide (GO) with a mixture derived from 3,4-dihydroxy-L-phenylalanine (L-DOPA) and poly(sodium 4-styrenesulfonate) (PSS). A mold-casting technique was developed to fabricate the free-standing nanocomposite CEM. The presence of sulfonic groups in the nanocomposite was confirmed with FTIR spectroscopy. Energy dispersive spectroscopy analysis showed the SGO was distributed across the entire membrane matrix, with minimal aggregation. The resultant SGO/PVDF nanocomposite CEM membrane demonstrated high hydrophilicity and high water uptake, but low swelling ratio. Furthermore, evaluation of the electrochemical properties of the nanocomposite CEM showed favorable ion exchange capacity (0.63 ± 0.08 meq/g), permselectivity (0.95 ± 0.04), and area resistance (2.8 ± 0.2 Ω cm2). The nanocomposite CEM show good potential for use in electromembrane desalination applications.
  • Mining biosynthetic gene clusters in Virgibacillus genomes.

    Othoum, Ghofran K.; Bougouffa, Salim; Bokhari, Ameerah; Lafi, Feras Fawzi; Gojobori, Takashi; Hirt, Heribert; Mijakovic, Ivan; Bajic, Vladimir B.; Essack, Magbubah (BMC genomics, Springer Science and Business Media LLC, 2019-09-05) [Article]
    BACKGROUND:Biosynthetic gene clusters produce a wide range of metabolites with activities that are of interest to the pharmaceutical industry. Specific interest is shown towards those metabolites that exhibit antimicrobial activities against multidrug-resistant bacteria that have become a global health threat. Genera of the phylum Firmicutes are frequently identified as sources of such metabolites, but the biosynthetic potential of its Virgibacillus genus is not known. Here, we used comparative genomic analysis to determine whether Virgibacillus strains isolated from the Red Sea mangrove mud in Rabigh Harbor Lagoon, Saudi Arabia, may be an attractive source of such novel antimicrobial agents. RESULTS:A comparative genomics analysis based on Virgibacillus dokdonensis Bac330, Virgibacillus sp. Bac332 and Virgibacillus halodenitrificans Bac324 (isolated from the Red Sea) and six other previously reported Virgibacillus strains was performed. Orthology analysis was used to determine the core genomes as well as the accessory genome of the nine Virgibacillus strains. The analysis shows that the Red Sea strain Virgibacillus sp. Bac332 has the highest number of unique genes and genomic islands compared to other genomes included in this study. Focusing on biosynthetic gene clusters, we show how marine isolates, including those from the Red Sea, are more enriched with nonribosomal peptides compared to the other Virgibacillus species. We also found that most nonribosomal peptide synthases identified in the Virgibacillus strains are part of genomic regions that are potentially horizontally transferred. CONCLUSIONS:The Red Sea Virgibacillus strains have a large number of biosynthetic genes in clusters that are not assigned to known products, indicating significant potential for the discovery of novel bioactive compounds. Also, having more modular synthetase units suggests that these strains are good candidates for experimental characterization of previously identified bioactive compounds as well. Future efforts will be directed towards establishing the properties of the potentially novel compounds encoded by the Red Sea specific trans-AT PKS/NRPS cluster and the type III PKS/NRPS cluster.
  • A Supramolecular View on the Cooperative Role of Brønsted and Lewis Acid Sites in Zeolites for Methanol Conversion.

    Bailleul, Simon; Yarulina, Irina; Hoffman, Alexander E J; Dokania, Abhay; Abou-Hamad, Edy; Chowdhury, Abhishek Dutta; Pieters, Giovanni; Hajek, Julianna; De Wispelaere, Kristof; Waroquier, Michel; Gascon, Jorge; Van Speybroeck, Veronique (Journal of the American Chemical Society, American Chemical Society (ACS), 2019-08-30) [Article]
    A systematic molecular level and spectroscopic investigation is presented to show the cooperative role of Brønsted acid and Lewis acid sites in zeolites for the conversion of methanol. Extra-framework alkaline-earth metal containing species and aluminum species decrease the number of Brønsted acid sites, as protonated metal clusters are formed. A combined experimental and theoretical effort shows that postsynthetically modified ZSM-5 zeolites, by incorporation of extra-framework alkaline-earth metals or by demetalation with dealuminating agents, contain both mononuclear [MOH]+ and double protonated binuclear metal clusters [M(μ-OH)2M]2+ (M = Mg, Ca, Sr, Ba, and HOAl). The metal in the extra-framework clusters has a Lewis acid character, which is confirmed experimentally and theoretically by IR spectra of adsorbed pyridine. The strength of the Lewis acid sites (Mg > Ca > Sr > Ba) was characterized by a blue shift of characteristic IR peaks, thus offering a tool to sample Lewis acidity experimentally. The incorporation of extra-framework Lewis acid sites has a substantial influence on the reactivity of propene and benzene methylations. Alkaline-earth Lewis acid sites yield increased benzene methylation barriers and destabilization of typical aromatic intermediates, whereas propene methylation routes are less affected. The effect on the catalytic function is especially induced by the double protonated binuclear species. Overall, the extra-framework metal clusters have a dual effect on the catalytic function. By reducing the number of Brønsted acid sites and suppressing typical catalytic reactions in which aromatics are involved, an optimal propene selectivity and increased lifetime for methanol conversion over zeolites is obtained. The combined experimental and theoretical approach gives a unique insight into the nature of the supramolecular zeolite catalyst for methanol conversion which can be meticulously tuned by subtle interplay of Brønsted and Lewis acid sites.
  • Evolution of oxygenated polycyclic aromatic hydrocarbon chemistry at flame temperatures

    Liu, Peng; Chen, Bingjie; Li, Zepeng; Bennett, Anthony; Sioud, Salim; Sarathy, Mani; Roberts, William L. (Combustion and Flame, Elsevier Inc.usjcs@elsevier.com, 2019-08-24) [Article]
    Oxygenated polycyclic aromatic hydrocarbons (OPAH) have received increasing attention due to their toxic effect on human health. This study comprehensively investigates the evolution of OPAH chemistry at flame temperatures. Jet-stirred reactor (JSR) experiments with benzene/phenol/C2H2/N2 and benzene/C2H2/O2/N2 revealed that OPAH with oxygenated heterocycle can be formed by the addition of C2H2 at 1400 K. To further clarify the evolution of OPAH chemistry in soot systems, OPAH formation and decomposition reaction pathways and kinetic parameters have been theoretically investigated. The potential energy surfaces of 1-naphtholate and 2-naphtholate growth, and thermal decomposition reactions, were calculated by combining the density functional theory B3LYP/6–311+G(d,p) and CCSD(T)/cc-pvdz methods. The reaction rate coefficients in the temperature range of 800–2500 K and pressure range of 0.1–100 atm were calculated using RRKM theory by solving the master equations. The potential energy surface of C2H2+1-naphtholate and C2H2+2-naphtholate growth reactions showed that the O atom could be locked in a naphthofuran molecule with the formation of a C[sbnd]O[sbnd]C oxygenated heterocycle; and the reaction rates were determined by adding the C2H2 elementary step with the energy barrier of 26.0 and 19.9 kcal/mol, respectively. Thermal decomposition reactions of 1-naphtholate and 2-naphtholate yielded an indenyl radical and CO. The thermal decomposition reaction rates were significantly sensitive to the zig-zag site structure next to the C[dbnd]O bond. The decomposition rate of 1-naphtholate at 1500 K, with a zig-zag site near the C[dbnd]O bond, was 14.8 times lower than that of 2-naphtholate with no zig-zag site near the C[dbnd]O bond. Rate comparison results indicate that the C[dbnd]O functional group rapidly converts to a C[sbnd]O[sbnd]C functional group with the addition of C2H2. The formation, growth and thermal decomposition reactions of 1-naphtholate and 2-naphtholate were added to a detailed PAH mechanism to check the effect of OPAH reactions on PAH formation chemistry. The concentration profile of naphthalene predicted by the updated PAH mechanism was lower than current PAH mechanism predictions by 29%, indicating that the OPAH reactions had a significant effect on PAH formation chemistry, and should be included in the PAH mechanism. However, due to the relatively low concentration of OPAH compared to PAH, it is possible to ignore the correlation between OPAH and soot nucleation at flame temperatures; therefore an OPAH evolution pathway (PAH → incipient soot → OPAH formation on soot particle → selective thermal decomposition of OPAH), is proposed to explain the high content of OPAH molecules (e.g., 9,10-anthraquinone, benz(a)anthracene-7,12-dione, and benzanthrone) adsorbed on the soot particle.
  • The influence of chemical composition on ignition delay times of gasoline fractions

    Naser, Nimal; Abdul Jameel, Abdul Gani; Emwas, Abdul-Hamid M.; Singh, Eshan; Chung, Suk-Ho; Sarathy, Mani (Combustion and Flame, Elsevier Inc.usjcs@elsevier.com, 2019-08-22) [Article]
    Tailoring fuel properties to maximize the efficiency of internal combustion engines is a way towards achieving cleaner combustion systems. In this work, the ignition properties along with the chemical composition (expressed as functional groups) of various light distillate (e.g., gasoline) cuts were analyzed to better understand the properties of full boiling range fuels. Various distillation cuts were obtained with a spinning band distillation system, which were then tested in an ignition quality tester (IQT) to obtain their global chemical reactivity (i.e., ignition delay time (IDT)). The distillates were further analyzed with 1H nuclear magnetic resonance (NMR) spectroscopy to identify and quantify various functional groups present in them. Various gasolines of research grade with specific target properties set forth by the Coordinating Research Council (CRC) that are known as FACE (fuels for advanced combustion engines) gasolines were distilled. When fuels with low aromatic content were distilled, the higher boiling point (BP) range (i.e., higher molecular weight) fractions exhibited lower IDT. However, distilled fractions of fuels with high aromatic content showed an initial decrease in IDT with increasing BP, followed by drastic increase in IDT primarily due to increasing aromatic groups. This study provides an understanding of the contribution of various volatile fractions to the IDTs of a multicomponent fuel, which is of relevance to fuel stratification utilized in gasoline compression ignition (GCI) engines to tailor heat release rates.
  • Performance and Stability Improvement of Layered NCM Lithium-Ion Batteries at High Voltage by a Microporous Al2O3 Sol–Gel Coating

    Wu, Yingqiang; Li, Mengliu; Wahyudi, Wandi; Sheng, Guan; Miao, Xiaohe; Anthopoulos, Thomas D.; Huang, Kuo-Wei; Li, Yangxing; Lai, Zhiping (ACS Omega, American Chemical Society (ACS), 2019-08-19) [Article]
    A simple and low-cost polymer-aided sol–gel method was developed to prepare γ-Al2O3 protective layers for LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode materials. The selected polyvinyl alcohol polymer additive not only facilitates the formation of a uniform and thin γ-Al2O3 layer on the irregular and rough cathode particle surface to protect it from corrosion but also serves as a pore-forming agent to generate micropores in the film after sintering to allow fast transport of lithium ions, which guaranteed the excellent and stable battery performance at high working voltage. Detailed studies in the full battery mode showed that the leached corrosion species from the cathode had a more profound harmful effect to the graphite anode, which seemed to be the dominating factor that caused the battery performance decay.
  • Scalable Synthesis of Amphiphilic Copolymers for CO2- and Water-Selective Membranes: Effect of Copolymer Composition and Chain Length

    Akhtar, Faheem; Kumar, Mahendra; Vovusha, Hakkim; Shevate, Rahul; Villalobos, Luis Francisco; Schwingenschlögl, Udo; Peinemann, Klaus-Viktor (Macromolecules, American Chemical Society (ACS), 2019-08-13) [Article]
    Dehumidification is a critical energy-intensive and crucial process for several industries (e.g., air conditioning and gas dehydration). Polymeric membranes with high water vapor permeability and selectivity are needed to achieve an energy-efficient water vapor removal. Herein, we demonstrate high-performance water vapor transport membranes based on novel amphiphilic tercopolymers. A series of amphiphilic tercopolymers comprising polyacrylonitrile, poly(ethylene glycol) methyl ether methacrylate (PEGMA), and poly(N,N-dimethylamino ethyl methacrylate) (PDMAEMA) segments are synthesized via an economical and facile free radical polymerization. The water vapor permeability increases with the increase in PEGMA chain length and the content of PEGMA segments. The best performing membrane (i.e., PEGMA-9502) achieved a water vapor permeability of 174 kBarrer. By optimizing the content and chain length of the PEGMA segments, the membranes could be tuned for carbon capture applications. The optimized membranes tested for CO2 separation showed a high CO2 permeability of 47 Barrer along with CO2/N2 and CO2/CH4 selectivities of 67 and 23, respectively. This work presents a simple and economic amphiphilic tercopolymer for the fabrication of membranes with excellent gas and water vapor separation performance.
  • Optimizing Pd:Zn molar Ratio in PdZn/CeO2 for CO2 Hydrogenation to Methanol

    Ojelade, Opeyemi A.; Zaman, Sharif F.; Daous, Muhammad A.; Al-Zahrani, Abdulrahim A.; Malik, Ali S.; Driss, Hafedh; Shterk, Genrikh; Gascon, Jorge (Applied Catalysis A: General, Elsevier BV, 2019-07-30) [Article]
    We report the compositional optimization of Pd:Zn/CeO2 catalysts prepared via sol-gel chelatization for the hydrogenation of CO2 under mild reaction conditions. The formation of a PdZn alloy, which is the main active phase for this reaction, was maximized for the catalyst with a Pd to Zn ratio close to 1. For this catalyst, a maximum conversion of 14%, close to thermodynamic equilibrium, and high selectivity to methanol (95%) were achieved at 220 °C, 20 bar, 2400 h−1 GHSV and H2:CO2 stoichiometric ratio of 3:1. The formation of PdZn alloys was achieved by reducing the catalyst precursor at 550 °C under hydrogen flow and confirmed by XRD. XPS study confirmed the presence of Pd°, being maximum for the optimized catalyst composition. At lower temperature, i.e. 180 °C, 1.0PdZn catalyst showed 100% selectivity to methanol with 8% CO2 conversion. RWGS reaction is responsible for the production of CO and its selectivity increases with temperature. In situ DRIFTS suggests that CO2 is activated as adsorbed CO3- species over CeO2. Surface micro-kinetics demonstrates that methanol can be formed either via formaldehyde or formic acid surface intermediates.
  • Maximizing Ag Utilization in High-Rate CO2 Electrochemical Reduction with a Coordination Polymer-Mediated Gas Diffusion Electrode

    Wang, Riming; Haspel, Henrik; Pustovarenko, Alexey; Dikhtiarenko, Alla; Russkikh, Artem; Shterk, Genrikh; Osadchii, Dmitrii; Ould-Chikh, Samy; Ma, Ming; Smith, Wilson A.; Takanabe, Kazuhiro; Kapteijn, Freek; Gascon, Jorge (ACS Energy Letters, American Chemical Society (ACS), 2019-07-29) [Article]
    e report the preparation and electrocatalytic performance of silver-containing gas diffusion electrodes (GDEs) derived from a silver coordination polymer (Ag-CP). Layer-by-layer growth of the Ag-CP onto porous supports was applied to control Ag loading. Subsequent electro-decomposition of the Ag-CP resulted in highly selective and efficient CO2-to-CO GDEs in aqueous CO2 electroreduction. Afterward, the metal–organic framework (MOF)-mediated approach was transferred to a gas-fed flow electrolyzer for high current density tests. The in situ formed GDE, with a low silver loading of 0.2 mg cm–2, showed a peak performance of jCO ≈ 385 mA cm–2 at around −1.0 V vs RHE and stable operation with high FECO (>96%) at jTotal = 300 mA cm–2 over a 4 h run. These results demonstrate that the MOF-mediated approach offers a facile route for manufacturing uniformly dispersed Ag catalysts for CO2 electrochemical reduction by eliminating ill-defined deposition steps (drop-casting, etc.) while allowing control of the catalyst structure through self-assembly.
  • Simultaneous production and functionalization of hexagonal boron nitride nanosheets by solvent-free mechanical exfoliation for superlubricant water-based lubricant additives

    An, Lulu; Yu, Yuanlie; Bai, Changning; Bai, Yongqing; Zhang, Bin; Gao, Kaixiong; Wang, Xinbo; Lai, Zhiping; Zhang, Junyan (npj 2D Materials and Applications, Nature Publishing GroupHoundmillsBasingstoke, HampshireRG21 6XS, 2019-07-26) [Article]
    Hexagonal boron nitride nanosheets (h-BNNSs), with a crystal lattice structure similar to graphene by over 98%, exhibit good lubrication properties as lubricant additives. However, the poor dispersibility in solvents has limited their wide practical applications as lubricant additives. In the present report, water dispersible Pebax functionalized h-BNNSs (Pebax-BNNSs) have been prepared through a one-step solvent-free mechanical exfoliation process which relies on a simple exfoliation of h-BN layers by shearing force in molten Pebax at 200 °C. In this process, Pebax molecules can synchronously react with the dangling bonds formed during the exfoliation process to achieve in situ functionalization of h-BNNSs. The reciprocating friction tests demonstrate that the as-obtained Pebax-BNNSs possess excellent antifriction and antiwear performance as water-based lubricant additive with a low concentration of 0.3 mg/mL under atmospheric condition. The friction coefficients can be <0.01, achieving superlubrication. Further systematical investigations on the wear traces, wear debris, and counter balls propose a “dispersion-compensation-filling repairment” friction mechanism. All these results demonstrate that h-BNNSs can achieve superlubrication as water-based lubricant additives via facile surface modification, making them very promising candidates as lubricant additives in practical applications.
  • Recycled Poly(ethylene terephthalate) for High Temperature Solvent Resistant Membranes

    Pulido, Bruno; Habboub, Ola; Aristizabal, Sandra; Szekely, Gyorgy; Nunes, Suzana Pereira (ACS Applied Polymer Materials, American Chemical Society (ACS), 2019-07-22) [Article]
    Porous membranes of recycled poly(ethylene terephthalate) (PET) were prepared by non-solvent induced phase separation (NIPS) and evaluated for the first time for the filtration in high temperature solvents and other harsh environments. The PET was recycled from commercial water bottles. The morphology, pore size and pore density were optimized by varying the composition of the polymer concentration in the casting solution, the solvent, and the non-solvent bath in conditions of controlled humidity and temperature. Poly(ethylene glycol) (PEG) of 0.2 and 1 kg mol-1 was used as an additive and pore inducing agent. The filtration performance of the membranes was tested under different solvents and temperatures. The obtained PET membranes were successfully applied for ultrafiltration with a MWCO of 40 kg mol-1 in dimethylformamide (DMF) at temperatures up to 100 ˚C. PET membranes were found to be resistant to a wide variety of solvents as well as in chlorine and acid medium. They could be used as porous support for thin-film composite membranes and for different applications requiring high chemical and heat resistance.
  • Towards cleaner PolarClean: efficient synthesis and extended applications of the polar aprotic solvent methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate

    Cseri, Levente; Szekely, Gyorgy (Green Chemistry, Royal Society of Chemistry (RSC), 2019-07-12) [Article]
    As a result of recent efforts in green solvent selection, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate, sold under the brand name Rhodiasolv PolarClean, has received considerable scientific and industrial attention as a possible non-toxic replacement for common polar aprotic solvents. However, the multicomponent nature and multi-step synthesis of this solvent remains an obstacle for its more widespread use and niche applications. In this work, a retrosynthetic approach was taken to identify novel shorter synthetic routes in alignment with green chemistry principles. High purity methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate was obtained in novel single-step reactions via two different base-catalysed Michael additions from readily available building blocks. The more advanced synthetic route shows great potential owing to the swift (30 min), solvent-free reaction and catalytic amounts of base (<6.5 mol%). Green metrics analysis, including Atom Economy, Complete E factor, Carbon Intensity and hazard analysis found the new synthesis to be more sustainable than the patented routes. Application of this green solvent was demonstrated for the first time for O- and N-arylation in SNAr reaction with solvent recovery with similar or superior yields compared to other green solvents. Moreover, broad opportunities for this green solvent in membrane science were identified, where the use of conventional, toxic polar aprotic solvents in large quantities is unavoidable. Important practical solvent properties and parameters such as dielectric constant, solubility parameters, solvent miscibility and NMR residual shifts have been determined to facilitate the uptake of methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate as a green solvent.
  • Turning a Methanation Co Catalyst into an In–Co Methanol Producer

    Bavykina, Anastasiya; Yarulina, Irina; Al Abdulghani, Abdullah; Gevers, Lieven; Hedhili, Mohamed N.; Miao, Xiaohe; Galilea, Adrian; Pustovarenko, Alexey; Dikhtiarenko, Alla; Cadiau, Amandine; Aguilar-Tapia, Antonio; Hazemann, Jean-Louis; Kozlov, Sergey; Oud-Chikh, Samy; Cavallo, Luigi; Gascon, Jorge (ACS Catalysis, American Chemical Society (ACS), 2019-07-05) [Article]
    The direct hydrogenation of CO2 to methanol using hydrogen is regarded as a potential technology to reduce greenhouse gas emissions and the dependence on fossil fuels. For this technology to become feasible, highly selective and productive catalysts that can operate under a wide range of reaction conditions near thermodynamic conversion are required. Here we combine a CO-producing In oxide catalyst with a methane-producing Co catalyst to obtain an In/Co catalyst for CO2 reduction to methanol. Density functional (DFT) simulations demonstrate that the charge transfer between the Co support and the In oxide film leads to enrichment of the surface of indium oxide with O vacancies, which serve as active sites for selective conversion of CO2 to methanol. Moreover, our simulations suggest that CO2 reduction on Co-supported In2O3–x films will preferentially yield methanol, rather than CO and methane. As a result, the prepared In@Co catalysts produce methanol from CO2 with high selectivity (>80%) and productivity (0.86 gCH3OH gcatalyst–1 h–1) at conversion levels close to thermodynamic equilibrium, even at temperatures as high as 300 °C and at moderate pressures (50 bar).
  • Engineering Metal-Organic Frameworks for the Electrochemical Reduction of CO2 : A Minireview.

    Wang, Riming; Kapteijn, Freek; Gascon, Jorge (Chemistry, an Asian journal, Wiley, 2019-06-27) [Article]
    The electrochemical reduction of CO2 holds great promise for lowering the concentration of CO2 in the Earth's atmosphere. However, several challenges have hindered the commercialization of this technology, including energy efficiency, the solubility of CO2 in the aqueous phase, and electrode stability. In this Minireview, we highlight and summarize the main advantages and limitations that metal-organic frameworks (MOFs) may offer in this field of research, either when used directly as electrocatalysts or when used as catalyst precursors.
  • Autoignition Characteristics of Ethers Blended with Low Cetane Distillates

    Nicolle, André; Naser, Nimal; Javed, Tamour; Rankovic, Nicolas; Sarathy, Mani (Energy & Fuels, American Chemical Society (ACS), 2019-06-25) [Article]
    The introduction of high cetane components has enabled the use of low cetane base gasoline in compression ignition engines. This study provides an understanding of the autoignition characteristics of various ethers blended with light distillates. The spontaneous ignition of mixtures was herein studied both experimentally [ignition quality tester (IQT)] and computationally, allowing the impacts of distillate composition, ether structure, and reaction progress on key ignition pathways to be determined. Various multicomponent base fuel surrogates were formulated to closely match actual fuel composition, thereby accurately simulating the interplay between distillates and oxygenates. Despite its lower cetane number, di-n-butyl ether (DNBE) was found to promote a more vigorous ignition than diethylether. However, OH radical scavenging by p-xylene counteracts the DNBE effect. Two preignition phases may be distinguished, namely, oxidation initiation by ether and subsequent chemical runaway involving simultaneously fuel and ether. According to the present kinetic mechanism, direct cross-reactions between ether radicals and light distillate components have little impact on the ignition delay time under the IQT operating conditions. As ignition progress increases, ether contribution to OH production decreases and oxidation paths related to aliphatic and cyclic alkanes become dominant. In the case of polyoxymethylene methyl ethers, the extra production of formaldehyde during the ignition phase does not impair the overall reactivity. The respective effects of OME1 and OME3 on ignition may be explained by the emergence of a new OH production path from OME3 oxidation products, while methyl formate production from OME1 acts as an OH radical sink. Even though locally lean zones of the IQT reactor may favor specifically neopentane oxidation at the expense of n-hexane, the new OH production path remains active over a wide range of conditions. Overall, the present detailed model qualitatively captures the nonlinear impact of various ethers on autoignition over the 15–30 DCN range, which makes it attractive for optimizing low cetane fuel formulation.

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