Hydrocarbon Units Research Articles

Unit-Emitting Carbon Dots.

Understanding the photoluminescence mechanisms of carbon dots (C-dots) is of importance for both fundamental science and their corresponding applications. In this study, we verify the emitting-unit model of C-dots by an upgraded "contrastive analysis" research paradigm. Employing preparative thin-layer chromatography, we recently developed polyamide column chromatography separation techniques, and four kinds of highly correlative C-dots are obtained from a homologous sample made from ortho-aminophenol precursors. Combining comprehensive experimental characterizations, especially the direct evidence from electrospray ionization mass spectrometry, we demonstrate that the photoluminescence of the four C-dots comes from the same polycyclic aromatic hydrocarbon units (named as emitting units) indeed, although these C-dots have substantially different chemical compositions.

Photoredox-Enabled Dearomative [2π + 2σ] Cycloaddition of Phenols.

Dearomative photocycloaddition of monocyclic arenes is an appealing strategy for comprehending the concept of "escape from flatland". This brings the replacement of readily available planar aromatic hydrocarbon units with a 3D fused bicyclic core with sp3-enriched carbon units. Herein, we outline an intermolecular approach for the dearomative photocycloaddition of phenols. In order to circumvent the ground-state aromaticity and to construct conformationally restrained building blocks, bicyclo[1.1.0]butanes were chosen as coupling partners. This dearomative approach renders straightforward access to a bicyclo[2.1.1]hexane unit fused to a cyclic enone moiety, which further contributed as a synthetic linchpin for postmodifications. Mechanistic experiment advocates for a plausible onset from both the reactants, depending on the redox potential.

Indolo[3,2-b]indole-based multi-resonance emitters for efficient narrowband pure-green organic light-emitting diodes.

Organic light-emitting diodes (OLEDs) utilizing multi-resonance (MR) emitters show great potential in ultrahigh-definition display benefitting from superior merits of MR emitters such as high color purity and photoluminescence quantum yields. However, the scarcity of narrowband pure-green MR emitters with novel backbones and facile synthesis has limited their further development. Herein, two novel pure-green MR emitters (IDIDBN and tBuIDIDBN) are demonstrated via replacing the carbazole subunits in the bluish-green BCzBN skeleton with new polycyclic aromatic hydrocarbon (PAH) units, 5-phenyl-5,10-dihydroindolo[3,2-b]indole (IDID) and 5-(4-(tert-butyl)phenyl)-5,10-dihydroindolo[3,2-b]indole (tBuIDID), to simultaneously enlarge the π-conjugation and enhance the electron-donating strength. Consequently, a successful red shift from aquamarine to pure-green is realized for IDIDBN and tBuIDIDBN with photoluminescence maxima peaking at 529 and 532 nm, along with Commission Internationale de l'Eclairage (CIE) coordinates of (0.25, 0.71) and (0.28, 0.70). Furthermore, both emitters revealed narrowband emission with small full width at half-maximum (FWHM) below 28 nm. Notably, the narrowband pure-green emission was effectively preserved in corresponding devices, which afford elevated maximum external quantum efficiencies of 16.3% and 18.3% for IDIDBN and tBuIDIDBN.

Sequence stratigraphic divisions and correlation of the middle sub-member of Eocene Shahejie Formation in the Bonan Sag of Bohai Bay Basin (China): Implication for facies and reservoir heterogeneities

The middle sub-member of the Eocene Shahejie Formation is mainly associated with deltaic environment, and considered as hydrocarbon bearing zone in the southeast of the Bonan Sag, Bohai Bay Basin, China. Previous research and the exploration work in an area were carried out separately, and inconsistency in understanding of stratigraphic division, correlation, and facies was encountered. Furthermore, the facies evolution in the targeted formation is still questionable. To fill these short-comings, sequence stratigraphic correlation and interpretation were conducted on the middle sub-member (Es3z) of the third member (Es3) of Eocene Shahejie Formation in the study area. Integrative facies and paleo-environment analyses are carried out through the correlation study of wireline logs, seismic data and core sedimentology. The sedimentological interpretation reveals that sandstone groups in the Es3z show five different facies associations in both lateral and vertical successions developed in the inner and outer delta front. These depositional facies include deposits in distributary channels, interdistributary channels, mouth bars, natural levees, and sheet sandstones. The Es3z sandstone intervals are characterized by five depositional sequences in terms of the third-order sequence, including Es3z2+3, Es3z4, Es3z5, Es3z6+7, and Es3z8. They are found in all wells consisting of the lowstand, transgressive, and highstand system tracts. These system tracts are separated by the maximum flooding surfaces and correlation boundaries of sandstone groups with unique characteristics of well log motifs, calibrated with the cores by particular lithology. Facies and reservoir heterogeneities are defined within a sequence stratigraphic framework approach for hydrocarbon reservoir prediction. Our results show that sediments were sourced from the southeast toward the northwest. Due to tectonic activity and lake level's fluctuations, reservoir facies are prograding towards the basin side. The steepness of the region impacts the facies and reservoirs evolution together with tectonics and fluctuations in lake level, which turns from the sandy conglomeratic reservoirs into a thick succession of sandstone reservoirs towards the basin side in LST HST and TST system tracts. These reservoir facies are considered as good, and capped by grayish mudstone (inner delta front) to dark gray mudstone (outer delta front) in TST system tracts. The facies architecture of all sandstone groups possesses the hydrocarbons potential in the inner and outer delta front region in which interpreted oil, oil-water layer and water-oil layers show variation in progradation and retrogradation stacking pattern. Among them lower sandstone units of Es3z8 and Es3z6+7 show dominancy in oil rich reservoirs, followed by Es3z2+3, Es3z4 and Es3z5 in LST, HST and TST system tracts. These hydrocarbon units can be correlated laterally with exploration wells for getting new well sites in third order sequence stratigraphic framework. Our findings shed new light on the facies and reservoir heterogeneities, which provide a useful aid for hydrocarbon exploration in the study area.

Synthesis of Chrysoporphyrins and a Related Benzopyrene-Fused System.

Reaction of 6-nitrochrysene with ethyl isocyanoacetate in the presence of a non-nucleophilic base gave a c-annulated pyrrole ethyl ester that was used to prepare chrysene-fused tripyrranes and a chrysopyrrole dialdehyde. Chrysene-fused tripyrranes were reacted with a pyrrole dialdehyde, but poor yields of chrysoporphyrins were obtained. However, condensation of the chrysopyrrole dialdehyde with a series of tripyrranes afforded excellent yields of chrysoporphyrins and an acenaphtho-chrysoporphyrin. Iron(III) chloride mediated oxidative cyclization of a dihexylchrysoporphyrin afforded a benzopyrene-fused porphyrin that exhibited a strongly red-shifted electronic absorption spectrum. DFT calculations show that both chrysoporphyrins and the benzopyrene-fused porphyrin have tautomers that possess 34π electron delocalization pathways that pass through the porphyrin nucleus and the fused polycyclic aromatic hydrocarbon (PAH) units. Protonation gave dications that favor 36-atom 34π electron circuits. c-Annulated pyrrole dialdehydes were also condensed with a carbatripyrrin to generate PAH-fused carbaporphyrins that retained fully aromatic properties.

Insight into biomass pyrolysis mechanism based on cellulose, hemicellulose, and lignin: Evolution of volatiles and kinetics, elucidation of reaction pathways, and characterization of gas, biochar and bio‐oil

Pyrolysis is the first step of gasification and combustion. The pyrolysis process of biomass is complicated, which is generally considered to consist of the pyrolysis of the three major components (i.e., cellulose, hemicellulose, and lignin). Understanding the pyrolysis behavior and product of each component holds a key to understanding the biomass pyrolysis mechanism. In this work, the pyrolysis behavior, pyrolysis kinetics, volatile evolution, and product characterization of the three major components are investigated. Results showed that pyrolysis characteristics and thermal stability of the three components were closely related to their unique chemical structures. During pyrolysis, the main pyrolytic volatiles of hemicellulose appeared first, followed by cellulose and then lignin volatiles in the 3D FTIR spectra. In term of pyrolysis products, gases were generated by the cracking of specific functional groups. Hemicellulose had the highest CO2 yield, whereas lignin had the highest CH4 yield due to the aromatic rings and methoxy groups in lignin structure. Whereas cellulose demonstrated the highest CO yield at high temperatures (above 550 °C). With increasing temperature, the carbon structures of carboxylic-C and O-alkyl-C in biochar decreased, while aryl-C was enhanced. This was due to the deoxygenation reactions such as dehydroxylation, decarboxylation, decarbonylation, and demethoxylation, resulting in a reduction in the number of oxygen-containing functional groups (such as –OH, –C=O, –COOH, and –OCH3), as well as the polycondensation reactions that formed more polycyclic aromatic hydrocarbon units during pyrolysis. The major components of cellulose bio-oil included anhydrosugars and furans. Whereas the bio-oils derived from hemicellulose and lignin showed the highest relative content of acids and phenols, respectively. Based on this analysis, the thermal decomposition pathways of cellulose, hemicellulose, and lignin were proposed.

Twins of Minimalistic Carbon Dots: Uniform Emitting‐Units and Molecular Level Repeatable Photoluminescence

AbstractUnderstanding the photoluminescence mechanism of carbon dots (C‐dots) is both of fundamental and technical significance. However, it has remained an extreme challenge due to C‐dots’ indeterminate constitution and complicated composition/structure. Herein, a combined processing system, namely extraction and subsequent preparative thin layer chromatography for C‐dots separation is presented. Benefiting from its powerful separation performances, two minimalistic C‐dots with almost identical structure and optical properties (named as “twin” C‐dots) are well separated. Then, by contrastive analysis, a photophysical picture for the C‐dots’ photoluminescence is presented: The C‐dots’ photoluminescence comes from uniform surface polycyclic aromatic hydrocarbon units instead of the whole particles, which is both size‐ and oxygen‐independent. The products not only are highly bright and stable against photobleaching, but possess repeatable photoluminescence with molecular level accuracy. So, the C‐dots favorably integrate the advantages from small molecule dyes to photoluminescent nanomaterials, which is unprecedented and desirable for property exploration and application expansion.

Logging identification for diagenetic facies of tight sandstone reservoirs: A case study in the Lower Jurassic Ahe Formation, Kuqa Depression of Tarim Basin

The Ahe Formation is one of the significant hydrocarbon units in the Kuqa Depression of Tarim Basin, which is characterized by poor reservoir quality and strong heterogeneities due to the diagenetic effects. Thus, ‘diagenetic facies’ are introduced to explore high-quality reservoir layers. According to the reservoir spaces, main diagenetic minerals and diagenesis, four types of diagenetic facies are categorized: tightly compacted facies, dissolution facies, carbonated cemented facies and microfracture facies. Petrophysical characteristics of different diagenetic facies are summarized, which shows that the dissolution facies and microfracture facies have higher porosities, permeabilities and bigger pore radii. Logging characteristics indicate that logging values of four diagenetic facies are overlapped seriously, making it impossible to classify them by original logging crossplot. Principal component analysis (PCA), linear discriminant analysis (LDA) and back propagation neural networks (BPNN) are used to build diagenetic facies identification models, and the former two belong to the linear statistical algorithms, while the latter is a nonlinear algorithm. By comparing the identification accuracy of these three algorithms, principal components (PCs) crossplot cannot recognize diagenetic facies effectively. LDA can achieve automatic identification by establishing discriminant functions, but its identification accuracy (71.7%) is too low to satisfy the exploration requirements. However, the trained BPNN yield 80% accuracy, which is more advantageous than PCA and LDA. The blind test shows that the predicted results by trained BPNN have a very high coincidence with the thin section analysis and the logging interpretation results. Therefore, the BPNN as provided in this paper can be effectively used for diagenetic facies identification based on conventional well logs.

Synthesis and Characterizations of 5,5'-Bibenzo[rst]pentaphene with Axial Chirality and Symmetry-Breaking Charge Transfer.

Exploration of novel biaryls consisting of two polycyclic aromatic hydrocarbon (PAH) units can be an important strategy toward further developments of organic materials with unique properties. In this study, 5,5′‐bibenzo[rst]pentaphene (BBPP) with two benzo[rst]pentaphene (BPP) units is synthesized in an efficient and versatile approach, and its structure is unambiguously elucidated by X‐ray crystallography. BBPP exhibits axial chirality, and the (M)‐ and (P)‐enantiomers are resolved by chiral high‐performance liquid chromatography and studied by circular dichroism spectroscopy. These enantiomers have a relatively high isomerization barrier of 43.6 kcal mol−1 calculated by density functional theory. The monomer BPP and dimer BBPP are characterized by UV‐vis absorption and fluorescence spectroscopy, cyclic voltammetry, and femtosecond transient absorption spectroscopy. The results indicate that both BPP and BBPP fluoresce from a formally dark S1 electronic state that is enabled by Herzberg–Teller intensity borrowing from a neighboring bright S2 state. While BPP exhibits a relatively low photoluminescence quantum yield (PLQY), BBPP exhibits a significantly enhanced PLQY due to a greater S2 intensity borrowing. Moreover, symmetry‐breaking charge transfer in BBPP is demonstrated by spectroscopic investigations in solvents of different polarity. This suggests high potential for singlet fission in such π‐extended biaryls through appropriate molecular design.

Triphenylene containing blue-light emitting semi-fluorinated aryl ether polymers with excellent thermal and photostability

Integration of polycyclic aromatic hydrocarbon (PAH) units into semi-fluorinated polymers affords high thermal stability and excellent processability for potential applications in optoelectronic, gas-separation, and advanced composites.

Study of Petrophysical Properties of the Yamama Formation in Siba Oilfield

Evaluating a reservoir to looking for hydrocarbon bearing zones, by determining the petrophysical properties in two wells of the Yamama Formation in Siba field using Schlumberger Techlog software. Three porosity logs were used to identify lithology using MN and MID cross plots. Shale volume were calculated using gamma ray log in well Sb-6ST1 and corrected gamma ray in well Sb-5B. Sonic log was used to calculate porosity in bad hole intervals while from density log at in-gauge intervals. Moreover, water saturation was computed from the modified Simandoux equation and compared to the Archie equation. Finally, Permeability was estimated using a flow zone indicator. The results show that the Yamama Formation is found to be mainly limestone that confirmed by cuttings description and this lithology intermixed with some dolomite, in addition to gas and secondary porosity effects. Generally, the formation is considered clean due to the low shale volume in both wells with the elimination of the uranium effect in well Sb-5B. The calculated porosity was validated by core porosity in YC and YD units. Modified Simandoux gives a better estimation than the Archie equation since it takes into account the conductive of matrix in addition to the fluid conductivity. Five equations were obtained from porosity permeability relationship of core data based on five hydraulic flow units reorganized from the cross plot of reservoir quality index against normalized porosity index. The overall interpretation showed that YC and YD units are the best quality hydrocarbon units in the Yamama Formation, while YA came in the second importance and has properties better than YB. Moreover, YE and YFG are poor units due to high water saturation.

The Disordering Effect of Plant Metabolites on Model Lipid Membranes of Various Thickness

This study was focused on the effect of plant metabolites (phloretin, capsaicin, digitonin, diosgenin and betulin) on the model lipid membranes. The methods of assessing the permeability of lipid bilayers based on measuring the leakage of a fluorescent marker (calcein) from liposomes and differential scanning microcalorimetry of vesicle suspension were used. It was found that the release rate of calcein from 1-palmitoyl-2-oleyl-sn-glycero-3-phosphocholine (POPC) liposomes with test compounds added to the suspension at a ratio with lipid 1 : 50 decreased in the order capsaicin > phloretin >> betulin ≈ diosgenin ≈ digitonin. In the case of cholesterol- and ergosterol-containing POPC liposomes, the activity decreased as diosgenin ≈ digitonin > betulin > capsaicin > phloretin. It was demonstrated that phloretin and capsaicin significantly reduce the melting temperature (Tm) and to increase the half-width of the main peak on the endotherm (T1/2) of dipalmitoylphosphocholine (DPPC), distearoylphosphocholine (DSPC) and diarachidoylphosphocholine (DAPC). These results show that the incorporation of these small molecules between the polar “heads” of phosphocholine. It was found that the increase in the length of saturated chains of membrane-forming lipids (from 16 to 20 hydrocarbon units), the absolute values of ΔTm and ΔT1/2 decreased in the presence of phloretin and increased with capsaicin. This may be the result of differences in the localization of phloretin and capsaicin in the membrane. Steroid saponins exhibited a weak effect on the thermotropic behavior of phosphocholines. The absolute values of ΔTm and ΔT1/2 decreased in the order DPPC, DSPC, and DAPC and increased in the order betulin, diosgenin, and digitonin. Steroid saponins are characterized by a more pronounced effect on the thermotropic behavior of the sterol–phospholipid mixture. The findings are consistent with the assumption of a high affinity of the tested saponins for sterol-containing membranes.

Olefin polymerization behavior of titanium(IV) alkoxo complexes with fluorinated diolate ligands: The impact of the chelate ring size and the nature of organoaluminum compounds

Titanium(IV) coordination compounds are effectively used as precatalysts for ethylene polymerization and copolymerization with other olefins. New titanium(IV) complexes 3b–d with ligands containing two diphenylcarbinol fragments linked by the perfluorinated hydrocarbon units –CF2– or –C2F4– were synthesized. The structures of complexes 3b and 3d were determined by X‐ray diffraction. Titanium atoms in 3b have a distorted trigonal‐bipyramidal coordination environment while spiro‐complex 3d is characterized by tetrahedral molecular geometry. The catalytic behavior of complexes activated by mixtures of Bu2Mg and alkylaluminium chlorides from among Me2AlCl, Et2AlCl, EtAlCl2, and Et3Al2Cl3 were studied. The resulting catalytic systems catalyze ethylene polymerization to afford ultra‐high molecular weight polyethylene, suitable for modern processing methods, and the solvent‐free solid state formation of super high‐strength (1.37–2.75 GPa) and high‐modulus (up to 138 GPa) oriented film tapes. The same catalytic systems catalyze ethylene copolymerization with 1‐hexene to afford high molecular weight semicrystalline elastomeric polymers containing up to 20% of comonomer units.

Mild and Efficient Synthesis of Diverse Organo-AuI -L Complexes in Green Solvents.

An exceptionally mild and efficient method was developed for the preparation of (hetero)aryl‐AuI‐L complexes using ethanol or water as the reaction medium at room temperature and Ar‐B(triol)K boronates as the transmetalation partner. The reaction does not need an exogeneous base or other additives, and quantitative yields can be achieved through a simple filtration as the only required purification method, which obviates considerable waste associated with alternative workup methods. A broad reaction scope was demonstrated with respect to both the L and (hetero)aryl ligands on product Au complexes. Despite the polar reaction medium, large polycyclic aromatic hydrocarbon units can be incorporated on the Au complexes in very good to excellent yields. The approach was demonstrated for the chemoselective manipulation of orthogonally protected aryl boronates to afford a new class of N‐heterocyclic carbene‐Au‐aryl complexes. A mechanistic rationale was proposed.

Solvent-Assisted Tyrosine-Based Dipeptide Forms Low-Molecular Weight Gel: Preparation and Its Potential Use in Dye Removal and Oil Spillage Separation from Water.

Low-molecular weight gelators (supramolecular, or simply molecular gels) are highly important molecular frameworks because of their potential application in drug delivery, catalysis, pollutant removal, sensing materials, and so forth. Herein, a small dipeptide composed of N-(tert-butoxycarbonyl)pentafluoro-l-phenylalanine and O-benzyl-l-tyrosine methyl ester was synthesized, and its gelation ability was investigated in different solvent systems. It was found that the dipeptide was unable to form gel with a single solvent, but a mixture of solvent systems was found to be suitable for the gelation of this dipeptide. Interestingly, water was found to be essential for gelation with the polar protic solvent, and long-chain hydrocarbon units such as, petroleum ether, kerosene, and diesel, were important for gelation with aromatic solvents. The structural insights of these gels were characterized by field-emission scanning electronic microscopy, atomic force microscopy, Fourier transform infrared analysis, and X-ray diffraction studies, and their mechanical strengths were characterized by rheological experiments. Both of the gels obtained from these two solvent systems were thermoreversible in nature, and these translucent gels had potential application for the treatment of waste water. The gel obtained from dipeptides with methanol–water was used to remove toxic dyes (crystal violet, Eriochrome Black T, and rhodamine B) from water. Furthermore, the gel obtained from dipeptide with assistance from toluene–petroleum ether was used as a phase-selective gelator for oil-spill recovery.

Leveraging Fluorescent Emission to Unitary Yield: Dimerization of Polycyclic Aromatic Hydrocarbons

AbstractWe report on the synthesis and characterization of novel substituted 1,1′‐biperylene‐2,2′‐diols in which the dihedral angle between the two polycyclic aromatic hydrocarbon (PAH) units is tailored from ca. 60° to ca. 90° in the solid state by introduction of cyclo‐etheric straps or sterically hindered groups such as the triisopropylsilyl (TIPS) group. Depending on the type of substitution, we lock the dihedral angle between the perylenyl moieties enabling fine‐tuning of the molecular optoelectronic properties, with the molecules displaying the smallest angles acting as exceptionally strong emitters with unitary quantum yields.

Structures of carbonaceous nanoparticles formed in various pyrolysis systems

In the pyrolysis of different hydrocarbon/carbon suboxid fuels formation of carbon particles with the special view to their structures was examined. For this, the following three very different pyrolysis systems were investigated experimentally i) a pyrolysis reactor, ii) a shock tube and iii) a plasma reactor with respect to the influence of varying reaction parameters on the carbonaceous nanoparticles. The particles formed in these reaction systems were studied in view of their morphology and state of crystallization by use of electron microscopy (Philips CM30) at low- and high resolution combined with micro-diffraction measurements.As to be seen at low resolution of the transmission electron microscopy studies, the particle sizes in the pyrolysis reactor and shock tube do not differ significantly, but distinguished considerably from those particle sizes obtained in the plasma reactor. While the particles obtained in the pyrolysis reactor and shock-tube had particle diameters of about d≈ 30 nm, the particles in the plasma reactor consisted of fluffy-like units, and their sizes were about d≈ 4 nm. The various carbon layers consisted of different polyaromatic hydrocarbon units with variable sizes arranged to diverse states in the course of graphitization.

Unconventional Natural Gas Accumulations in Stacked Deposits: A Discussion of Upper Paleozoic Coal‐Bearing Strata in the East Margin of the Ordos Basin, China

AbstractThe Upper Paleozoic (Carboniferous to Permian) succession in the east margin of the Ordos Basin in the North China Craton has a potential to contain significant hydrocarbon resources, though attention have been mainly attracted for its successful development of coalbed methane (CBM). To improve the previous resource estimates and evaluate the hydrocarbon play possibilities, this study incorporated new discoveries of hydrocarbon units and their stratigraphic relation with source rocks, hydrocarbon migration and trapping configurations. Continuous hydrocarbon accumulation units were identified within the Upper Paleozoic, including the Taiyuan, Shanxi and Xiashihezi formations with great tight gas potential, and the Taiyuan and Shanxi formations also containing shale gas and CBM. Different strata combinations are identified with coal deposition and favour for continuous gas accumulations, including the tidal flat, deltaic and fluvial systems distributed in most of the study areas. Methane was not only generated from the thick coal seams in the Taiyuan and Shanxi formations, but also from shale and dark mudstones. The coal, shale and tight sandstones are proved of remarkable gas content and hydrocarbon indications, and the gas saturation of tight sandstones decreases upward. The stacked deposit combinations vary isochronally in different areas, while the coal seams were developed stably showing good gas sources. Two key stages control the hydrocarbon enrichment, the continuous subsidence from coal forming to Late Triassic and the anomalous paleo‐geothermal event happened in Early Cretaceous, as indicated by the fluid inclusions evidence. Extensive areas show good hydrocarbon development potential presently, and more works should be focused on the evaluation and selection of good reservoir combinations.

Minimum explosible concentrations of mist and dust clouds

When hot vapor condenses the nucleation particles initially formed coalesce rapidly and exothermically. Most of the heat of coalescence is released in less than a millisecond while droplets are less than 100 nm diameter. Consequently, the heat is released close to the source of the vapor and has no effect on dispersion. Coagulation rate is governed by an inverse square law with respect to number density; calculations showed that a vapor cloud initially within its flammable range should produce droplets smaller than 10 µm after a minute of coalescence. Such micronized droplets completely vaporize in flame preheat zones and behave as premixed vapors rather than as individual droplets; this characteristic is not due to the increased surface energy accompanying subdivision into micronized droplets but to short evaporation times in the thick preheat zones of limit flames. Droplet growth time is a nonlinear function of cloud mass concentration and if the latter exceeds about 10 times the minimum explosible concentration (MEC), droplets quickly grow to above 20–40 µm. These larger droplets tend to burn individually and the estimation of MEC becomes complicated, although rain‐out of large droplets might hasten dispersal to below the MEC.With the assumption that micronized crystalline organic materials behave similarly to liquid droplets, we derive “intrinsic” MEC values for both hydrocarbons and a series of CHOx fuels having increasing O:C ratios. In each case, the MEC attains a constant “terminal value” as carbon number is increased. Terminal MEC values are 40 g m−3 for CH (hydrocarbons), 50 g m−3 for CHO (aldehydes, ethers, etc.), 60 g m−3 for CHOO (esters), 67 g m−3 (polyethylene glycols), and 103 g m−3 (carbohydrates). MEC values for CHO and CHOO decrease rapidly with increased carbon number since additional hydrocarbon units dilute the functional oxygen group. For polyethylene glycols and carbohydrates, the MEC is less dependent on carbon number since oxygen is contained in a repeating group. Although scission and/or decomposition replace simple evaporation as carbon number increases, flash pyrolysis data for polyethylene in air show that the products of decomposition can have little effect on MEC. Nevertheless, owing to experimental deficiencies published MEC values for polyethylene are as low as 10–30 g m−3. Of the many factors affecting MEC tests, we focus on the effects of gravity and flame radiation. Radiation not only affects MEC but also the burning rates of metal dusts such as titanium; such tests should be carried out on an adequately large scale. © 2017 American Institute of Chemical Engineers Process Process Saf Prog 37:4–17, 2018

Enantioselective aliphatic C-H bond oxidation catalyzed by bioinspired complexes.

Enantioselective aliphatic C-H bond oxidation simultaneously installs functionality and chirality into hydrocarbon units, converting in a single step readily available, inexpensive and typically inert hydrocarbons into precious building blocks for organic synthesis. The reaction remains however an open problem eager for catalyst development and improvement. Metal complexes reproducing structural and reactivity aspects of oxygenases are emerging as promising homogeneous catalysts for this class of reactions. The present work reviews the current status of field, analyzing the difficulties of the reaction, discussing principles of catalyst design, and critically highlighting the limitations of the current state-of-the-art methodologies.