C6 Isomers Research Articles

Engineering Trifluoromethyl Groups in Porous Coordination Polymers to Enhance Stability and Regulate Pore Window for Hexane Isomers Separation.

Effective separation of hexane (C6) isomers is critical for a variety of industrial applications but conventional distillation methods are energy-intensive. Adsorptive separations based on porous coordination polymers (PCPs) offer a promising alternative due to their exceptional porosity and tunable properties. However, there is still an urgent need to develop PCPs with high stability and separation performance. This study investigates how substituting a methyl (-CH3) group with a trifluoromethyl (-CF3) group can regulate pores and hydrophobicity in PCPs. This precise adjustment aims to enhance stability and improve the kinetic separation performance of hydrophobic C6 isomers by considering the size and hydrophobicity of the trifluoromethyl group. Two isostructural PCPs with pcu topology, PCP-CH3 and PCP-CF3, were synthesized to vary pore diameters and hydrophobicity based on the presence of -CH3 or -CF3 groups. PCP-CF3 showed greater stability in water compared to PCP-CH3. While PCP-CH3 had high adsorption capacities, it lacked selectivity, whereas PCP-CF3 demonstrated improved selectivity, particularly in excluding dibranched isomers. Dynamic column separation experiments revealed that PCP-CF3 could selectively adsorb linear and monobranched isomers over dibranched isomers at room temperature. These findings highlight the potential of fluorine-modified PCPs for efficient isomer separation and underscore the importance of stability improvement strategies.

Mesoporogen-free synthesis of hierarchical SAPO-11 from kaolin for hydroisomerization of n-alkanes

Hierarchical SAPO-11, featuring both micropore and mesopore channels, demonstrates an outstanding performance in high-octane gasoline production. In this work, we propose an economic and effective approach to directly fabricate hierarchical SAPO-11 molecular sieve from natural kaolin, eliminating the need for mesoporogens. The systematic characterization results show that the kaolin-derived SAPO-11 possesses abundant micro-mesoporous structure and more Brønsted (B) acid sites on the external surface in contrast with the conventional SAPO-11 prepared employing silica sol as silicon source as well as SAPO-11 synthesized with the assist with of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127). The analysis of the formation process reveals that the kaolin not only provides silicon source for the SAPO-11 crystal growth, but also offers confined environment for crystal growth along the preferential orientation, resulting in the generation of the microporous and mesoporous structure. Benefiting from these unique properties, the kaolin-derived Pt/SAPO-11 exhibits considerably improved selectivity for di-branched C8 isomers in n-octane hydroisomerization.

Selective Separation of C8 Aromatics by an Interpenetrating Metal-Organic Framework Material.

O-xylene (OX) is an important chemical raw material, but it is often produced in mixtures with other C8 aromatics. Similar physicochemical properties of the C8 isomers make their separation and purification very difficult and energy intensive. There is an unmet need for an adsorbent that would be effective for the separation of OX from the other C8 isomers. This work reports a three-dimensional interpenetrated metal-organic framework, SYUCT-110, that interacts with each of the single-component C8 isomers to form. The selectivity of C8 aromatic hydrocarbons was determined through liquid-phase batch uptake experiments. The results revealed that the selectivity order was OX > PX > MX > ethylbenzene (EB). The selectivity values were found to be 2.63, 1.58, 5.51, 3.71, 1.86, and 3.02 for OX/MX, OX/PX, OX/EB, PX/MX, MX/EB, and PX/EB, respectively. The adsorption capacity of OX was 71 mg/g. Grand Canonical Monte Carlo simulations were used to study the C8 adsorption sites, revealing that π···π interactions are the main reason for the observed adsorption selectivity. The adsorption energy calculation results also verified the selectivity of SYUCT-110 for the synthesis of OX.

Structural study of minor C84 isomers as chlorofullerenes, C84(11)Cl22, C84(14)Cl22, C84(16)Cl22, and C84(16)Cl24

Chlorofullerenes C84Cl22,24 were obtained by chlorination of minor C84 isomers mixture with VCl4 at 330 °C. An X-ray crystallographic study with the use of synchrotron radiation revealed the presence of C84(11)Cl22, C84(14)Cl22, C84(16)Cl22, and C84(16)Cl24 in the same crystal.

Understanding shape selectivity effects of hydroisomerization using a reaction equilibrium model.

We study important aspects of shape selectivity effects of zeolites for hydroisomerization of linear alkanes, which produces a myriad of isomers, particularly for long chain hydrocarbons. To investigate the conditions for achieving an optimal yield of branched hydrocarbons, it is important to understand the role of chemical equilibrium in these reversible reactions. We conduct an extensive analysis of shape selectivity effects of different zeolites for the hydroisomerization of C7 and C8 isomers at chemical reaction equilibrium conditions. The reaction ensemble Monte Carlo method, coupled with grand-canonical Monte Carlo simulations, is commonly used for computing reaction equilibrium of heterogeneous reactions. The computational demands become prohibitive for a large number of reactions. We used a faster alternative in which reaction equilibrium is obtained by imposing chemical equilibrium in the gas phase and phase equilibrium between the gas phase components and the adsorbed phase counterparts. This effectively mimics the chemical equilibrium distribution in the adsorbed phase. Using Henry's law at infinite dilution and mixture adsorption isotherm models at elevated pressures, we calculate the adsorbed loadings in the zeolites. This study shows that zeolites with cage or channel-like structures exhibit significant differences in selectivity for alkane isomers. We also observe a minimal impact of pressure on the gas-phase equilibrium of these reactions at typical experimental reaction temperatures 400-700K. This study marks initial strides in understanding the reaction product distribution for long-chain alkanes.

Myelin basic proteins charge isomers interact differently with the peptidyl arginine deiminase-2.

The deamination of arginine and its conversion to citrulline is a modification observed in positively charged proteins such as histones or myelin basic protein (MBP). This reaction is catalyzed by peptidyl arginine deiminase (PAD), whose abnormal activation is associated with autoimmune diseases like rheumatoid arthritis and multiple sclerosis. However, the mechanisms that trigger PAD activation and the pathophysiological processes involved in hypercitrullination remain unknown. In this study, we investigated the interaction between PAD and various charged isomers of MBP, each differing in the degree of post-translational modification. Immunoprecipitation experiments were conducted to examine the binding between PAD and the different charge isomers of MBP. Our findings revealed that the phosphorylated forms of MBP (C3 and C4) exhibited a higher affinity for PAD compared to the unmodified (C1) and fully citrullinated forms (C8). Additionally, we observed that only in the presence of the unmodified C1 isomer did PAD undergo autocitrullination, which was inhibited by the endogenous guanidine-containing component, creatine. In the presence of other isomers, PAD did not undergo autocitrullination. Furthermore, we found that the unmodified isomer of MBP-C1 contains methylated arginines, which were not affected by the pre-treatment with PAD. Based on our findings, we propose that the increased phosphorylation of central threonines in the original MBP may trigger PAD activation, leading to increased citrullination of the protein and subsequent disorganization of the myelin sheath. These insights contribute to a better understanding of the underlying mechanisms in autoimmune diseases associated with hypercitrullination, potentially opening new avenues for therapeutic interventions.

Formation of the icosahedral C60 fullerene via migration of single sp atoms and annihilation of sp-atom pairs.

The disappearance of sp2 structural defects during abundant fullerene isomer formation is considered within the framework of the atomistic mechanism with participation of carbon atoms with sp hybridization. The study is carried out using the example of the icosahedral C60-Ih fullerene formation from the appropriate C58-C2v fullerene with a 7-ring. In this case the studied atomistic mechanism includes the following stages: (1) insertion of single carbon atoms into the fullerene from carbon vapor as an sp-atom instead of or above a bond, (2) directional migration of the sp-atom positions towards the 7-ring with decrease of energy, and (3) meeting of two sp atoms near the 7-ring with annihilation of the sp-atom pair and formation of the sp2 structure of the C60-Ih fullerene. The probabilities of all possible sp-atom positions on the appropriate C58-C2v fullerene shell are estimated as a function of temperature using the total energies of these positions obtained by spin-polarized density functional theory calculations using the PBE functional. Based on these estimations, it is shown that formation of the C60-Ih isomer is the most probable within the framework of the considered mechanism relative to other C60 isomers. The energetics of sp-atom pair annihilation in the formation of the C60-Ih isomer is also studied via DFT calculations. The advantages of the considered atomistic mechanism of the abundant fullerene isomer formation are discussed.

Study on the preparation and n-heptane isomerization performance of MoOx-Pd/Ce-MCM-48 catalyst.

A Ce-MCM-48 molecular sieve was prepared by the hydrothermal synthesis method. Using Ce-MCM-48 as the support, a series of MoOx Pd/Ce-M catalysts were prepared by the impregnation method by introducing MoOx and Pd. XRD, N2 adsorption desorption, SEM, TEM, NH3-TPD, Py-IR, FT-IR, and ICP-MS were used to characterize the physicochemical properties. The performance of n-heptane isomerization in a micro fixed bed device was evaluated. The results showed that the synthesized Ce-MCM-48 was mesoporous, with a spherical particle morphology, a long-range ordered pore structure, weakly acidic sites on the surface, and an increase of B and L acids. The 2% MoOx-Pd/Ce-M catalyst was used for the probe reaction of n-heptane hydroisomerization; when the reduction temperature was 400 °C, the reduction time was 2 hours, the reaction temperature was 300 °C, the WHSV was 7.6 h-1, the conversion rate was 58.7%, the selectivity was 91.2%, and the maximum yield was 53.5%. The product distribution of multiple C7 isomers increased the selectivity of multi branched isoheptane. The addition of an appropriate amount of MoOx would improve the performance of n-heptane isomerization.

Highly Selective p-Xylene Separation from Mixtures of C8 Aromatics by a Nonporous Molecular Apohost.

High and increasing production of separation of C8 aromatic isomers demands the development of purification methods that are efficient, scalable, and inexpensive, especially for p-xylene, PX, the largest volume C8 commodity. Herein, we report that 4-(1H-1,2,4-triazol-1-yl)-phenyl-1H-benzo[de]isoquinoline-1,3(2H)-dione (TPBD), a molecular compound that can be prepared and scaled up via solid-state synthesis, exhibits exceptional PX selectivity over each of the other C8 isomers, o-xylene (OX), m-xylene (MX), and ethylbenzene (EB). The apohost or α form of TPBD was found to exhibit conformational polymorphism in the solid state enabled by rotation of its triazole and benzene rings. TPBD-αI and TPBD-αII are nonporous polymorphs that transformed to the same PX inclusion compound, TPBD-PX, upon contact with liquid PX. TPBD enabled highly selective capture of PX, as established by competitive slurry experiments involving various molar ratios in binary, ternary, and quaternary mixtures of C8 aromatics. Binary selectivity values for PX as determined by 1H NMR spectroscopy and gas chromatography ranged from 22.4 to 108.4, setting new benchmarks for both PX/MX (70.3) and PX/EB (59.9) selectivity as well as close to benchmark selectivity for PX/OX (108.4). To our knowledge, TPBD is the first material of any class to exhibit such high across-the-board PX selectivity from quaternary mixtures of C8 aromatics under ambient conditions. Crystallographic and computational studies provide structural insight into the PX binding site in TPBD-PX, whereas thermal stability and capture kinetics were determined by variable-temperature powder X-ray diffraction and slurry tests, respectively. That TPBD offers benchmark PX selectivity and facile recyclability makes it a prototypal molecular compound for PX purification or capture under ambient conditions.

OSDA-free synthesis of FeZSM-22 zeolite from natural minerals for n-octane hydroisomerization

A seed-directed approach to synthesizing FeZSM-22 zeolite without organic structure directing agent (OSDA) was developed by using Fe-rich diatomite as all aluminum and iron sources. The FeZSM-22 zeolite with optimal crystallinity and purity can be obtained by systematically adjusting feed composition and synthesis conditions. Characterizations show that FeZSM-22 zeolite synthesized with OSDA-free owns high crystallinity, obvious thin needle-shaped morphology and high Bronsted/Lewis acid ratio. Significantly, when used for n-octane hydroisomerization reaction, its derived catalyst exhibits the best catalytic performance reflected by the highest selectivity to C8 isomers compared to the two reference catalysts prepared based on a Fe-containing and a Fe-free ZSM-22 synthesized through an OSDA-directed route from natural diatomite and conventional chemicals, respectively. This work provides an alternative route to sustainably synthesizing heteroatomic zeolites with high performance.

Progress on Hybrids and Mixed Alloys of Boron Subphthalocyanines (BsubPc) and Boron Subnaphthalocyanines (BsubNc); Tuning the Electrochemical Properties Towards Organic Electronic Applications

Our research and development focus has been on the molecular design, synthetic methodology and in-depth characterization of boron subphthalocyanines (BsubPcs) and subnaphthalocyanines (BsubNcs) to apply them to organic electronic applications. BsubPcs, BsubNcs and their hybrids are macrocycles with a chelated central boron atom via nitrogen bonding, and is a p-conjugated macrocyclic material. Our focal point balances between the basic and applied chemistry, chemical engineering, their in-depth physical properties (electrochemistry included). We also do computational modelling. Once materials are developed, we merge them into organic electronics to function as light emitting, light absorbing and electronic conducting materials within organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs)/organic solar cells (OSCs). The basic electrochemical and photophysical properties, developing and evaluating the properties is critical to move onto such applications.For this presentation, I will focus on our progress on the development of hybrids and mixed alloys of BsubPcs and BsubNcs.Regarding hybrids, they are a mixture of BsubPcs and BsubNcs, and are formed via a reaction of a statistical distribution of phthalonitrile and 2,3-dicyanonaphthalene intermediates on reaction with BCl3; we have named them X-RnBsub(Pcx-Ncy); X the axial substituent, Rn the number of peripheral substitutions, Pcx being the number of 6 p-conjugated bonds, Ncy being the number of 10 p-conjugated bonds (Figure). On first study, we found that X-RnBsub(Pc1-Nc2) have low photostability. Therefore, we moved onto developing a ‘statistical’ synthetic methodology to target highest yields of X-RnBsub(Pc2-Nc1)s, and we did achieve relatively high yields. X-RnBsub(Pc2-Nc1)s therefore could be purified to enable physical characterization. Within a couple past publications, the unique absorption spectra was noted and we have confirmed its uniqueness. The X-RnBsub(Pc2-Nc1)s absorption spectra is as wide as if BsubPc and BsubNc were mixed together. This therefore has good potential to harvest a larger scope of photons from solar or to achieved FRET transfer from a host to emit via an OLED. We then did in-depth first electrochemical characterization, confirmed their electrochemical oxidation and reduction stability and also did in-depth photoluminescence characterization. Therefore, merging X-RnBsub(Pc2-Nc1)s into organic electronic devices as well as other chemistry to synthesis the hybrids is ongoing.Regarding mixed alloys, in the past as we have shown that BsubNcs ended up being a mixed alloyed composition with random bay-position halogenation, that is formed during the reaction of BCl3 with 2,3-dicyanonaphthalene at temperature, which is the process to form the BsubNcs. The random bay-position halogenation has been shown to be impactful in a positive way within OPV devices, negative within OLED devices and also has electrochemical variations and good reversibility. Ongoing, given it is random halogenation, and some of the positive outcomes, this justifies considering additional mixed alloyed compositions.We have also recently shown that mixed alloyed BsubPcs can be formed with three peripheral halogens in the alpha (a) or beta (b) positions, named as Cl-αCl3BsubPc, Cl-βCl3BsubPc, Cl-αF3BsubPc, and Cl-βF3BsubPc. The alloyed mixtures consisted of C1 and C3 isomers of trihalogenated BsubPcs. The physical properties characterization including photophysics, electrochemistry, and thermal characterization, were studied and were also positive and then were engineered into OSCs as electron donors and electrons acceptors to clarify their impact on device performance which had positivity aspects. Therefore, we moved onto developing a set of additional BsubPc mixtures. To be outlined for this presentation, we considered sets of phthalonitrile mixtures to form peripherally halogenated BsubPc mixtures during the formation of BsubPcs from these intermediates. For example, 4,5-dichlorophthalonitrile (Cl2-pn), 4,5-difluorophthalonitrile (F2-pn), tetrachlorophthalonitrile (Cl4-pn), and tetrafluorophthalonitrile (F4-pn) are commercially available compounds that were mixed together and yields a mixture of BsubPc which we named: X-Cl2nF2mBsubPc and X-Cl4nF4mBsubPc (X = Cl or F being a variant, Figure). We then did physical characterization and found positive aspects including electrochemical oxidation and reduction stability. Merging them into organic electronic devices is ongoing and might be present during this presentation time.We did also recently develop additional chemistry methodology to develop additional mixed alloyed BsubPcs. The methodology was to develop phthalonitrile intermediates that have numbers of hydrogen, chlorine and fluorine substitutions and to take them onto the formation of the BsubPc mixed alloys. This is ongoing and may have some aspects to outline during this presentation.We also do computational modelling to look into other relative impacts of the materials being developed, for example the HOMO and LUMO orbital distributions, the local ionization etc. This will also be outlined during this presentation. Figure 1

Theoretical Study on the Structure and Spectral Properties of Several Classical C84 Isomers and Their Newly Synthesized Derivatives.

The ground-state electronic/geometrical structures of the three classical isomers Cs(15)-C84, C2(13)-C84, and C2(8)-C84 as well as the corresponding embedded derivatives U@Cs(15)-C84, YCN@C2(13)-C84, and U@C2(8)-C84 have been calculated at the density functional theory (DFT) level. Then, the isomers of C84 were theoretically identified by X-ray photoelectron spectroscopy (XPS) and near X-ray absorption fine-structure spectroscopy (NEXAFS). The spectral components of total spectra for carbon atoms in various local environments have been investigated. The ultraviolet-visible (UV-vis) absorption spectroscopies of U@Cs(15)-C84, YCN@C2(13)-C84, and U@C2(8)-C84 have also been performed utilizing time-dependent (TD) DFT calculations. The UV-vis spectra are in good agreement with the experimental results. These spectra provide an effective method for the identification of isomers. The results of this study can offer useful data for further experimental and theoretical studies using X-ray and UV-vis spectroscopy methods on freshly synthesized fullerene isomers and their derivatives.

On the role of C4 and C5 products in electrochemical CO2 reduction via copper-based catalysts

We identify many larger organics as products of electrochemical CO2 reduction in high-current GDEs – most interestingly, C4 and C5 isomers. The analysis of selectivity trends allows for deduction of general hypotheses to build a detailed mechanism.

Adsorption and dynamics of linear and mono-branched hexane isomers in MIL-140 metal-organic frameworks.

Recent breakthrough experiments revealed the iso-reticular Zr-MOFs, MIL-140B and MIL-140C, as promising sorbents for the separation of C6 isomers. Interestingly while the ultra-small pore MIL-140B exhibited hexane isomer sorption hierarchy according to the normal boiling point order (n-C6 > 3MP (3-methyl pentane)), an uncommon shift in the elution order was observed in the larger pore MIL-140C. It was only speculated that the flexibility of the MOFs might be the origin of this intriguing behavior. Herein, flexible force field hybrid osmotic Monte Carlo combined with molecular dynamics simulations were carried out to unravel the microscopic mechanism of the adsorption and dynamics of both C6 isomers in MIL140B and MIL140C. Thermodynamically preferred adsorption of n-C6 over 3MP was predicted for MIL-140B and to a slightly less extent for MIL-140C. Interestingly while the mobility of n-C6 was found to remain higher than that of 3MP in the whole range of loading for MIL-140B, 3MP becomes more mobile than n-C6 at saturation in MIL-140C. This suggests that this kinetics order is most probably the origin of the inversion of the elution order observed experimentally for MIL-140C. The translational and rotational dynamics of the two guests in MIL-140B and MIL-140C was further understood in-depth.

Synthesis, Isolation, and Structural Study of Trifluoromethyl Derivatives of the IPR Isomer of C84 Fullerene, C84(11)(CF3)14,16,18

AbstractC84 is the most abundant higher fullerene which is present in the arc‐discharge fullerene soot. Among 24 topologically possible IPR isomers of C84, two major isomers, C84(22) and C84(23), and several minor ones have been identified experimentally. We report the synthesis, isolation, and structure elucidation of trifluoromethyl derivatives of the most abundant minor isomer of C84, C84(11)(CF3)14,16,18. The experimentally determined addition patterns of altogether eight new compounds, four C84(11)(CF3)14, three C84(11)(CF3)16, and one C84(11)(CF3)18, are discussed in terms of the attachments in ribbons of para C6(CF3)2 hexagons and formation of stabilizing substructures of local aromaticity on the C2−C84(11) carbon cage. The general principles of multi addition of bulky CF3 groups are considered which are based on theoretical DFT calculations of formation energies of C84(11)(CF3)n isomers. Thus, trifluoromethylation pathways are now discussed in details for five different isomers of C84.

Group additivity values for the heat of formation of C2–C8 alkanes, alkyl hydroperoxides, and their radicals

A set of 58 group additivity values (GAV) for the calculation of the heat of formation is derived from an extensive and accurate database of 192 ab initio heats of formation. The ab initio values are from companion calculations at the CCSD(T)–F12/cc-pVTZ-F12//B2PLYPD3/cc-pVTZ level of theory employing second order connectivity based hierarchy reference reactions with ANL energies for the reference species. This database of 192 species consists of alkanes (RH), alkyl radicals (Ṙ), alkyl hydroperoxides (RO2H), alkyl-peroxy (RȮ2) radicals, and hydroperoxy-alkyl (Q˙OOH) radicals of all of the isomers of C2–C5 alkane fuels and a select set of C6–C8 isomers. The GAV and ab initio based enthalpies for this dataset show excellent agreement, with an estimated 2σ uncertainty of 0.9 kcal mol–1. Among the 58 GAV terms, 40 are refinements of previously reported terms, while 18 are newly developed. These new GAV terms are mainly non-next-nearest neighbor interactions (NNI) and β-corrections. The inclusion of these new groups significantly improves the accuracy of the GAV estimates of the heats of formation. The updated GAVs can be used with increased confidence to estimate the heats of formation of combustion relevant hydrocarbons and oxygenated hydrocarbons and their corresponding radicals, which are important in predicting low-temperature chemistry and are critical in the development of accurate chemical kinetic models.

Dual pore‐size sieving in a novel oxygenate‐pillared microporous adsorbent for C6 alkane isomers separation

AbstractAdsorbents executing molecular sieving mechanisms for the efficient separation of n‐hexane (C6) alkane isomers require delicate pore size control, but afford unsatisfactory single‐component separations according to their branch degrees. Herein, we report a novel oxygenate‐pillared microporous adsorbent, MoOFOUR‐Co‐tpb, ([Co(tpb)2MoO4], tpb = 1,2,4,5‐tetra(pyridin‐4‐yl) benzene), with three gourd‐shaped channels for dual pore‐size sieving of C6 isomers. In particular, MoOFOUR‐Co‐tpb excludes 2,2‐dimethylbutane, while 3‐methylpentane (3MP) can enter one channel showing a high uptake of 82.6 mg g−1, contrasting to the n‐hexane (nHEX) adsorption by two channels (136 mg g−1). This dual pore‐size control strategy renders a record high equilibrium–kinetic combined selectivity for nHEX/3MP (30.2). Moreover, three‐ and five‐component breakthrough experiments confirm the practical separation performances and cycling stability. Multiple theoretical simulations reveal the separation mechanism and adsorption sites.

Neonatal screening for isovaleric aciduria: Reducing the increasingly high false-positive rate in Germany.

Newborn screening (NBS) for isovaleric acidemia (IVA) is performed by flow injection tandem mass spectrometry quantifying C5 carnitines (C5). Isovalerylcarnitine, however, is isomeric with pivaloylcarnitine which can be present in blood due to maternal use of pivaloylester-containing antibiotics, available in Germany since late 2016. During a 36-month period (January 19-December 21), all newborns screened in Hamburg with a C5 above cutoff (NeoGram®: 0.50 μmol/L or Neobase®2: 0.45 μmol/L) were included in the study. As a second-tier test, a simple ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to differentiate the C5 isomers pivaloyl-, 2-methylbutyryl-, isovaleryl-, and valerylcarnitine. Out of 156 772 newborns tested, one turned out to have genetically proven IVA while 99 were false positive (C5: 0.5-8.2μmol/L) due to the presence of pivaloylcarnitine. These cases have increased year by year and show local clusters. Retrospective analysis of another 39 cases from 287 206 neonates tested at the NBS center in Heidelberg with C5 elevation (0.9-10.6μmol/L) but clinical and biochemical exclusion of IVA yielded evidence of pivaloylcarnitine in all cases. Inclusion of a second-tier test into NBS significantly reduces the high and increasing false-positive rate of IVA screening. This avoids further diagnostic steps, prevents unnecessary stress and anxiety of parents in a remarkably high number of cases. If Hamburg data of 2021 are extrapolated to all of Germany, one can assume around 800 (1‰) false-positive cases in comparison to an average of two classic IVA cases per year. Unless licensing of pivaloylester-containing drugs for use during pregnancy is reconsidered, a second-tier test for C5 determination is indispensable.

Carbene Addition Isomers of C70 formed in the Flame of Low-Pressure Combustion.

In the flames during low-pressure combustion, not only a rich variety of fullerenes but also many reactive intermediates can be produced (e.g., carbene, CH2) that are short-lived and cannot be stabilized directly under normal circumstances. These intermediates can be captured by fullerene carbon cages for stabilization. In this paper, three C71H2 isomers were synthesized in situ in low-pressure benzene-acetylene-oxygen diffusion flame combustion. The results, which were unambiguously characterized by single-crystal X-ray diffraction, show that the three isomers are carbene addition products of D5h-C70 on different sites. The relative energies and stability of different C71H2 isomers are revealed by Ultraviolet-Visible (UV-Vis) absorption spectroscopy, in combination with theoretical calculations, in this work. Both the in situ capture and theoretical study of these C71H2 isomers in low-pressure combustion will provide more information regarding carbene additions to other fullerenes or other carbon clusters at high temperatures.

Effect of diesel blended with di-n-butyl ether/1-octanol on combustion and emission in a heavy-duty diesel engine

Two kinds of C8 isomers, di-n-butyl ether (DNBE) and 1-octanol, as potential oxygen-containing alternative fuels, show important value in the trade-off between efficiency and emission. In the present work, the effects of DNBE/1-octanol with different proportions (0, 10%, and 20%) blended into diesel on the combustion characteristics, fuel economy, and emission characteristics in a six-cylinder heavy-duty diesel engine were studied at low, medium, and high loads. 1-Octanol with a 20% blending ratio showed different combustion characteristics in the cylinder compared with the other fuels. The economic analysis showed that the brake specific fuel consumption of DNBE–diesel blend fuels was higher than that of 1-octanol–diesel blend fuels, while brake thermal efficiency was the opposite tendency. The emissions of nitrogen oxides (NOx), hydrocarbons (HC), and carbon monoxide (CO) were affected by the types of blend fuels, blending ratios, and loads. In comparison with 1-octanol–diesel blend fuels, the addition of DNBE in diesel promoted the emission of nitrogen oxides, but inhibited the emissions of soot, HC, and CO. DNBE– and 1-octanol–diesel blend fuels increased the weighted brake specific fuel consumption but decreased the weighted brake thermal efficiency compared with diesel in the World Harmonized Stationary Cycle test cycle of Euro VI regulation. The weighted NOx, HC, soot, and CO emissions of blend fuels depended on the types of blend fuels and blend ratios. The weighted NOx, HC, and soot emissions were reduced by blending 1-octanol into diesel, while the weighted CO emission was increased. The weighted CO and soot emissions of diesel blended with DNBE were reduced than that of diesel.