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1.
Raw oil shale, kerogen (demineralized shale) and carbonaceous residues from kerogen pyrolysis in the range 350–700°C (at 50°C intervals) were studied by laser ablation Fourier transform ion cyclotron resonance mass spectrometry using the fundamental frequency of Nd: YAG laser (1064 nm). Normally, pyrolysis of the raw materials produces oil and the resulting residues have decreased hydrogen to carbon ratios and exhibit relative increases in aromatic carbons. Raw shale and kerogen give positive-ion spectra with mainly protonated species of m/z 100–400. Laser ablation positive-ion mass spectra of the pyrolysis products of the kerogen show the presence of C60, C70 and other fullerene ions with a distribution of higher mass fullerene ions up to m/z 4000. Using high laser powers (100–3000 MW cm?2), the residue from pyrolysis at 350°C initially did not produce any fullerene ions (apart from traces of C60 and C70), but after continued ablation a cavity was formed in the target and a wide distribution of fullerene ions was obtained with subsequent laser pulses. Residues obtained from the pyrolysis of kerogen at 400–500°C produced fullerene ions at both low (4–200 kW cm?2) and high laser powers. The 550°C pyrolysis residue gave only small amounts of C60 and C70 positive ions at low laser power whereas residues from the pyrolysis of kerogen above 550°C did not give fullerene ions over a wide range of laser powers. It is proposed from the above results that the changes in the aromatic nature of the kerogen residues with increasing pyrolysis temperature are directly related to the ease of fullerene formation. This is possibly due to the formation of large polycyclic aromatic systems at pyrolysis temperatures above 400°C, formed in the residues. It should be noted that the shale samples (raw or pyrolysed) did not generate fullerene ions under any of the conditions employed in these experiments.  相似文献   

2.
To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the T p of GLY-A and GLY-B were 254.6 and 275.7°C. The T peak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively. Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.  相似文献   

3.
Perdeuterioacrylonitrile can be prepared conveniently from succinonitrile in a two-step process. Succinonitrile is exchanged with D2O to obtain perdeuteriosuccinonitrile, which is then pyrolyzed at ~550°C to obtain perdeuterioacrylonitrile and DCN. CDBCN and CzDsCN are by-products of this reaction. A chemical procedure for separating perdeuterioacrylonitrile from these materials was developed. This involved formation of the Diels-Alder adduct of cyclopentadiene with perdeuterioacrylonitrile, followed by pyrolysis of the purified adduct at -330°C. Cyclopentadiene was removed from the resulting pyrolyzate by reaction with maleic anhydride. Purified perdeuterioacrylonitrile exchanged with H2O to yield β,β-dideuterioacrylonitrile in good yield and good isotopic purity.  相似文献   

4.

Cellulose, which comprises D-glucose and L-glucose (D,L-cellulose), was synthesized from D-glucose (1D) and L-glucose (1L) via cationic ring-opening polymerization. Specifically, the ring-opening copolymerization of 3-O-benzyl-2,6-di-O-pivaloyl-β-D-glucopyranoside (2D) and 3-O-benzyl-2,6-di-O-pivaloyl-β-D-glucopyranoside (2L), synthesized from compounds 1D and 1L, respectively, in a 1:1 ratio, afforded 3-O-benzyl-2,6-di-O-β-D,L-glucopyranan (3DL) with a degree of polymerization (DPn) of 28.5 (Mw/Mn?=?1.90) in quantitative yield. The deprotection of compound 3DL and subsequent acetylation proceeded smoothly to afford acetylated compound 4DL with a DPn of 18.6 (Mw/Mn?=?2.08). The specific rotation of acetylated compound 4DL was?+?0.01°, suggesting that acetylated compound 4DL was optically inactive cellulose triacetate. Furthermore, before acetylation, compound 4DL was an optically inactive cellulose comprising an almost racemic mixture of D-glucose and L-glucose. Compound 4DL was an amorphous polymer. This is the first reported synthesis of optically inactive D,L-cellulose.

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5.
A simple procedure is provided for the quantitative analysis of Diels-Alder adduct prepared from commercial methylcyclopentadiene and maleic anhydride by NMR spectra without further separation of its components. The adduct is considered as a mixture of endo norbornene derivatives (Cn), (Dn), (E) and (Fn) which are obtained from 1-, 2- and 5-methylcyclopentadiene and cyclopentadiene, respectively. The quantitative analysis of the adduct can be made on a basis of the ratio of the signal intensities of the olefinic protons in the adduct. The result shows that the adduct prepared under mild conditions mainly consists of three norbornene derivatives (Cn), (Dn) and (Fn), with a negligibly small amount of (E). When the adduct prepared under mild conditions is heated, it contains the exo isomers (Cx), (Dx) and (Fx). The ratio of the endo and the exo norbornene derivatives, i.e. ((Cn) + (Dn) + (Fn)):((Cx) + (Dx) + (Fx)), may be estimated from the signal intensities of the 5- and 6-protons. As the result of the analyses of the adducts which are obtained by heating at different temperatures the adduct prepared under mild conditions, the mole fraction of 2-methyl isomers (Dn) and (Dx), which is found to be 58 % in the adduct prepared at ? 15°C, keeps on increasing with rising temperature and shows almost the same value, ~86%, when heated above 150°C. Therefore, the equilibrium between 1-methyl and 2-methyl isomers does not change above 150°C. On the other hand, the isomerization from endo to exo isomers is not found below 110°C, and then exo isomers keep on increasing above 140°C.  相似文献   

6.
Reaction of trans(N)-[Co(D-pen)2]? (pen = penicillaminate) or trans(N)-[Co(L-pen)2]? with [MCl2(L)] {M = Pd or Pt, L = 2,2′-bipyridine (bpy) or 1,10-phenanthroline (phen)} in the presence of tetrafluoroborate stereoselectively gave an optically active S-bridged dinuclear complex, [M(L){Co(D-pen)2}]BF4 · 2H2O or [M(L){Co(L-pen)2}]BF4 · 2H2O. The mixture of equimolar amounts of these enantiomers in H2O crystallizes as [M(L){Co(D-pen)2}]0.5[M(L){Co(L-pen)2}]0.5BF4 · 4H2O (DLbpyM · 4H2O, DLphenM-A · 4H2O), in which the enantiomeric complex cations are included by the ratio of 1 : 1. In crystals of DLbpyM · 4H2O and DLphenM-A · 4H2O, [M(L){Co(D-pen)2}]+ and [M(L){Co(L-pen)2}]+ interact stereospecifically with each other through π-conjugated systems to form dimeric structures. Other racemic crystals with the same chemical compositions as DLphenM-A · 4H2O, DLphenM-B · 4H2O, were obtained from equimolar amounts of [M(phen){Co(D-pen)2}]+ and [M(phen){Co(L-pen)2}]+ in aqueous acetonitrile solution. In the crystals of DLphenM-B · 4H2O, [M(phen){Co(D-pen)2}]+ and [M(phen){Co(L-pen)2}]+ are arranged alternately while overlapping phen planes, and the π electronic systems of phen interact with each other. Although stereospecific hydrogen bonds between the coordinated ?NH2 and ?COO? groups are formed in both DLphenM-A · 4H2O and DLphenM-B · 4H2O, their bonding modes differ noticeably from each other. As a result, DLphenM-A · 4H2O builds up 1-D ladder-like networks due to the stereospecific π–π stackings and hydrogen bondings between enantiomers, while 2-D sheet-like networks are established for DLphenM-B · 4H2O.  相似文献   

7.
A mono‐lancunary keggin‐type decatungstosilicate (SiW11) polyoxometalate (POM) modified by γ‐aminopropyltriethoxysilane (KH550) was incorporated into polyimide (PI) through copolymerization. Nuclear magnetic resonance (NMR), fourier transition infrared spectroscopy (FTIR), and wide angle X‐ray diffraction (WAXD) were used to characterize the structure and composition of the polyoxometalate–organosilane hybrid (SiW11KH550) and PI/SiW11KH550 copolymers. The differential scanning calorimetry (DSC) studies indicate that the glass transition temperature (Tg) of PI/SiW11KH550 copolymers increases from 330°C (for neat PI) to 409°C (for the copolymer sample with 10 wt% of SiW11KH550). Dielectric measurement showed that both the dielectric constant and the dielectric loss for the copolymer thin films decreased with the increase in SiW11KH550 content, and the dielectric constant and dielectric loss values decreased to 2.1 and 3.54 × 10?3, respectively, for the copolymer sample with 10 wt% of SiW11KH550. The incorporation of SiW11KH550 into polymer matrices is a promising approach to prepare PI films with a low dielectric constant and low dielectric loss. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

8.
The unimolecular decomposition of 3,3-dimethylbut-1-yne has been investigated over the temperature range of 933°-1182°K using the technique of very low-pressure pyrolysis (VLPP). The primary process is C? C bond fission yielding the resonance stabilized dimethylpropargyl radical. Application of RRKM theory shows that the experimental unimolecular rate constants are consistent with the high-pressure Arrhenius parameters given by log (k/sec?1) = (15.8 ± 0.3) - (70.8 ± 1.5)/θ where θ = 2.303RT kcal/mol. The activation energy leads to DH0[(CH3)2C(CCH)? CH3] = 70.7 ± 1.5, θH0f((CH3)2?CCH,g) = 61.5 ± 2.0, and DH0[(CH3)2C(CCH)? H] = 81.0 ± 2.3, all in kcal/mol at 298°K. The stabilization energy of the dimethylpropargyl radical has been found to be 11.0±2.5 kcal/mol.  相似文献   

9.
The thermal unimolecular decomposition of ethylbenzene, isopropylbenzene, and tert-butylbenzene was studied using the very-low-pressure pyrolysis (VLPP) technique. Each reactant decomposed by way of β C? C bond homolysis, producing methyl radicals and benzyl or benzylic-type radicals. RRKM calculations show that the observed rate constants, when combined with thermochemical estimates, are consistent with the following high-pressure rate expressions: \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.3 - (72.7/{\rm \theta)} $\end{document} for ethylbenzene between 1053 and 1234 K, \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.8 - (71.3/{\rm \theta)} $\end{document} for isopropylbenzene between 971 and 1151 K, and \documentclass{article}\pagestyle{empty}\begin{document}$ \log k(\sec ^{ - 1}) = 15.9 - (69.1/{\rm \theta)} $\end{document} for tert-butylbenzene between 929 and 1157 K, where θ (kcal/mol) = 2.303RT. Resulting activation energies combined with heat capacity and heat of formation data led to the following dissociation enthalpies and enthalpies of formation at 298 K: DH° (øCH(CH3)? CH3) = 73.8 kcal/mol, ΔHf° (øÇCH(CH3)) = 39.6 kcal/mol, DH° (øC(CH3)2? CH3) = 72.9 kcal/mol, and ΔHf° (øÇ(CH3)2) = 32.4 kcal/mol. Derived high-pressure rate constants are in good accord with results of lower temperature toluene- and aniline-carrier experiments.  相似文献   

10.
The thermodynamic stability of a cytosine(C)-rich i-motif tract of DNA, which features pH-sensitive [C..H..C]+ moieties, has been studied as function of both pressure (0.1–200 MPa) and pH (3.7–6.2). Careful attention was paid to correcting citrate buffer pH for known variations that stem from changes in pressure. Once pH-corrected, (i) at pH >4.6 the i-motif becomes less stable as pressure is increased (KD decreases), giving a small negative volume change for dissociation (ΔD) of the i-motif – a conclusion opposite to that which would be drawn if the buffer pH was not corrected for the effects of pressure; (ii) the i-motif's melting temperature increases by more than 30 K between pH 6.5 and 4.5, the consequence of an enthalpy for dissociation (ΔDH°) of 77(3) and 90(3) kJ (mol H+)−1 at 0.1 and 200 MPa, respectively; (iii) below pH 4.6 at 0.1 MPa (pH 4.3 at 200 MPa) the melting temperature decreases as a result of double protonation of cytosine pairs, and ΔDH° and ΔDV° change signs; and (iv) the combination of ΔDH° and ΔDV° lead to the melting temperature at pH 4.3 being 3 K higher at 200 MPa than at 0.1 MPa.  相似文献   

11.
A thermal analysis of a series of polylactides (PLA) was carried out based on the number of average molecular mass (M n), and the nature of isomer (D, L and DL). It is confirmed that the glass transition temperature (T g) of PLA increased as a function of molecular mass irrespective of isomer type except sample with a high polydispersity index. The melting temperature (T m) and enthalpy of crystal fusion (ΔH f) of L-isomer increased as the M n was increased from 1100 to 27500. The degree of crystallinity (χc%) increased as a function of molecular mass. However no crystallization peak was detected in the lower molecular mass range (550–1400). The non-isothermal crystallization behavior of the PLA melt was significantly influenced by the cooling rate. Both D and L isomers exhibited insignificant difference in thermal properties and DL lactides exhibited amorphous behavior at identical molecular masses. Change in microstructure showed significant difference between two isomers. Analysis of the FTIR spectra of these PLA samples in the range of 1200–1230 cm−1 supported DSC observation on crystallinity.  相似文献   

12.
Fe3O4@hybrid-molecular-imprinted polymers (Fe3O4@HMIPs) with three monosaccharide templates (D-(+)-galactose, L-(?)-fucose, and D-(+)-mannose), and hybrid materials were modified by deep eutectic solvents (DESs). The materials obtained were combined with solid-phase extraction (SPE) to purify of D-(+)-galactose, L-(?)-fucose, and D-(+)-mannose from seaweed, and the SPE procedure was optimized further. Compared to Fe3O4@HMIPs, DESs-Fe3O4@HMIPs were developed to achieve stronger recognition and higher recoveries of D-(+)-galactose, L-(?)-fucose, and D-(+)-mannose from seaweed. The optimal practical recoveries of the three monosaccharides, D-(+)-galactose, L-(?)-fucose, and D-(+)-mannose, purified by DESs-4-Fe3O4@HMIPs from seaweed were 90.12, 92.82, and 91.94%, respectively. When acetone was used as the washing solution, the actual amounts extracted were 6.87, 4.17, and 5.29?mg?·?g?1, respectively.  相似文献   

13.
N2O was photolyzed at 2139 Å to produce O(1D) atoms in the presence of H2O and CO. The O(1D) atoms react with H2O to produce HO radicals, as measured by CO2 production from the reaction of OH with CO. The relative importance of the various possible O(1D )–H2O reactions is The relative rate constant for O(1D) removal by H2O compared to that by N2O is 2.1, in good agreement with that found earlier in our laboratory. In the presence Of C3H6, the OH can be removed by reaction with either CO or C3H6: From the CO2 yield, k3/k2 = 75,0 at 100°C and 55.0 at 200°C to within ± 10%. When these values are combined with the value of k2 = 7.0 × 10?13exp (–1100/RT) cm3/sec, k3 = 1.36 × 10?11 exp (–100/RT) cm3/sec. At 25°C, k3 extrapolates to 1.1 × 10?11 cm3/sec.  相似文献   

14.
The method of chemical difference was utilized to accurately determine the relative importance of all the reaction steps in the direct photolysis of N2O at 2139 Å (25° and 250°C) and 1849 Å (25° C), as well as in the Hg6(1P1)-sensitized photolysis of N2O at 1849 Å (25°C). In all cases, the primary process is predominantly, if not exclusively, Experiments with trace amounts of C3H6 added showed a slight, but not significant, difference in product ratios (N2 and O2). From these experiments the quantum yield of O(3P) from all possible sources was estimated as 0.02 ± 0.02. Experiments with excess N2 at 1849 Å indicated that O(1S) was not produced in the direct photolysis. The O(1S) yield is probably zero, and certainly <0.05. The O(1D) atom can react with N2O via The ratio k2/k3 was found to be 0.69 ± 0.05 in all cases. When combined with other data from our laboratory, the average value is 0.65 ± 0.07. This represents the value for translationally energetic O(1D) atoms. When excess He was added to remove the excess translational energy, k2/k3 rose to 0.83 ± 0.06, which is in reasonable agreement with the value of 1.01 ± 0.06 found in another laboratory. We conclude that for O(1D) atoms with no excess thermal energy, k2/k3 = 0.90 ± 0.10.  相似文献   

15.
Poly(dimethylsiloxane)‐containing diblock and triblock copolymers were prepared by the combination of anionic ring‐opening polymerization (AROP) of hexamethylcyclotrisiloxane (D3) and nitroxide‐mediated radical polymerization (NMRP) of methyl acrylate (MA), isoprene (IP), and styrene (St). The first step was the preparation of a TIPNO‐based alkoxyamine carrying a 4‐bromophenyl group. The alkoxyamine was then treated with Li powder in ether, and AROP of D3 was carried out using the resulting lithiophenyl alkoxyamine at room temperature, giving functional poly(D3) with Mw/Mn of 1.09–1.16. NMRPs of MA, St, and IP from the poly(D3) at 120 °C gave poly(D3b‐MA), poly(D3b‐St), and poly(D3b‐IP) diblock copolymers, and subsequent NMRPs of St from poly(D3b‐MA) and poly(D3b‐IP) at 120 °C gave poly(D3b‐MA‐b‐St) and poly(D3b‐IP‐b‐St) triblock copolymers. The poly(dimethylsiloxane)‐containing diblock and triblock copolymers were analyzed by 1H NMR and size exclusion chromatography. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 6153–6165, 2005  相似文献   

16.
Thermosensitive star-shaped poly(2-isopropyl-2-oxazoline) (molar mass M≈21000 g mol?1) in D2O solution was studied by the static and dynamic light scattering methods. The behavior of the polymer investigated in deuterated water is similar qualitatively to that observed previously in undeuterated water. At the same time, the considerable quantitative changes of polymer behavior in D2O were seen. Deuterium substitution of solvent affects the phase transition temperature by decreasing its value by 1°C. The temperature interval of phase transition in D2O solution expands (by about 1°C) in comparison with that in H2O solution.  相似文献   

17.
The kinetics of anionic polymerization of α-methylstyrene with Na+ as counterion have been studied in mixed solvents of tetrahydrofuran (THF) and toluene in various compositions at ?25 to 5°C. The ion-pair rate constant k(±) increases by about a factor of 50 at ?10°C, whereas the activation energy decreases from 5.1 to ?2.2 kcal/mole, when THF in the mixed solvent increases from 30 to 100 vol-%. The plot of log k(±) against (D ? 1)/(2D + 1) is a curve, where D is the dielectric constant of the medium. This deviation from linearity is explained in terms of propagation by two types of ion-pairs.  相似文献   

18.
Densities, apparent molar volumes, and partial molar volumes of benzene solutions ofmeso-tetradimethylphenyl porphyrin derivatives H2T(i,j-CH3)PP (where i,j = 2,3-; 2,4-; 3,4-; 2,5-; 3,5-);meso-tetra-4-alkoxyphenyl porphyrin derivatives H2T(4-OCnH2n+1)PP (wheren = 2–4,6–8,10,12,16);meso-tetra-3-butoxyphenyl porphyrin H2T(3-OC4H9)PP;meso-tetra-4-tert-butylphenyl porphyrin H2T(4tBu)PP;meso-tetra-3,5-ditert-butylphenyl porphyrin H2T(3,5-tBu)PP at 25°C and tetraphenylporphyrin, H2TPP,H2T(4-OC10H21)PP;H2T(4-OC12H25)PP and H2T(4tBu)PP at 20°C; 30°C; 40°C; 50°C were determined. The solubilities of the compounds in benzene at 25°C were measured. The solvent excluded volumes for different conformational states and the topology of dimethyl derivatives of tetraphenylporphyrin were calculated and compared with partial molar volume data. The correlation between the partial molar volumes and van der Waals volumes for the derivatives H2TPP,n-alkanes,n-alkanols, fatty acids, cyclic compounds, and crown ethers using the equation of Terasawa was elaborated. The average increment of the methylene group for alkoxy-substituted H2TPP was calculated as δV 2 o (CH2) = 16.6±0.4cm3-mol-1. The volumetric expansion coefficients of benzene solutions of H2TPP; H2T(4-OC10,H21)PP; H2T(4-OC12H25)PP and H2T(4-tBu)PP were determined and discussed. The importance of packing efficiencies around the solute molecules were examined.  相似文献   

19.
Nanocrystalline zirconium carbonitride (Zr‐C‐N) and zirconium oxide (ZrO2) films were deposited by chemical vapor deposition (CVD) of zirconium‐tetrakis‐diethylamide (Zr(NEt2)4) and ‐tert‐butyloxide (Zr(OBut)4), respectively. The films were deposited on iron substrates and characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS). The Zr‐C‐N films show blue, golden brown or bronze colours, with colour stability depending upon the precursor composition (pure metal amide or mixed with Et2NH). The deposition temperature showed no pronounced effect on the granular morphology of the Zr‐C‐N films. The XRD data of the films correspond to the formation of carbonitride phase whereas the XPS analyses revealed a strong surface oxidation and incorporation of oxygen in the film. The films deposited using a mixture of Zr(NEt2)4 and Et2NH showed higher N content, better adhesion and scratch resistance when compared to films obtained from the CVD of pure Zr(NEt2)4. Subject to the precursor composition and deposition temperature (550‐750 °C), the microhardness values of Zr‐C‐N films were found to be in the range 2.11‐5.65 GPa. For ZrO2 films, morphology and phase composition strongly depend on the deposition temperature. The CVD deposits obtained at 350 °C show tetragonal ZrO2 to be the only crystalline phase. Upon increasing the deposition temperature to 450 °C, a mixture of tetragonal and monoclinic modifications was formed with morphology made up of interwoven elongated grains. At higher temperatures (550 and 650 °C), pure monoclinic phase was obtained with facetted grains and developed texture.  相似文献   

20.
Polycrystalline β-zinc sulfide thin films were prepared by solution pyrolysis of an ethylzinc isopropylthiolate–zinc bis(dibutyldithiocarbamate) combined precursor (EtZnSiPr–Zn(S2CNnBu2)2) in chloroform solution on glass or silicon(111) substrates at 300°C. Homogeneous but amorphous indium sulfide thin films were obtained from butylindium bis(isopropylthiolate) (nBuInSiPr2) in P-xylene on these substrates at 300°C similarly. The sulfide thin films obtained were characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray fluorescence Microanalysis, scanning electron microscopy (SEM) and optical band gap measurements.  相似文献   

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