NMR characterization of dihydrosterculic acid and its methyl ester

Cyclopropane FA occur in nature in the phosphoplipids of bacterial membranes, in oils containing cyclopropene FA, and in Litchi sinensis oil. Dihydrosterculic acid (2-octyl cyclopropaneoctanoic acid) and its methyl ester were selected for ¹H and ¹³C NMR analysis as compounds representative of cyclopropane FA. The 500 MHz ¹H NMR spectra acquired with CDCl₃ as solvent show two individual peaks at −0.30 and 0.60 ppm for the methylene protons of the cyclopropane ring. Assignments were made with the aid of 2D correlations. In accordance with previous literature, the upfield signal is assigned to the cis proton and the downfield signal to the trans proton. This signal of the trans proton is resolved from the peak of the two methine protons of the cyclopropane ring, which is located at 0.68 ppm. The four protons attached to the two methylene carbons α to the cyclopropane ring also show a split signal. Two of these protons, one from each methylene moiety, display a distinct shift at 1.17 ppm, and the signal of the other two protons is observed at 1.40 ppm, within the broad methylene peak. The characteristic peaks in the ¹³C spectra are also assigned.     

Effects of Solvation and Ionization on 13C NMR Spectra of Lignin Model Compounds,Spruce Milled Wood Lignin and Kraft Lignin

The effects of alkali and polar aprotic solvent on the aromatic carbons signals in ¹³C NMR (Carbon-13 nuclear magnetic resonance) spectra of lignin model compounds and spruce milled wood lignin (MWL) were studied. It was found that in 1 M aqueous NaOH signal shifts of C-1 and C-4 carbon atoms in the aromatic ring were the most noticeable in lignin models with free phenolic hydroxyl groups, which are ionized under the conditions. A similar effect in the spectra of the studied model compounds was observed in 0.5 M aqueous NaOD-deuterated dimethyl sulfoxide (DMSO) mixture (DMSO: water ratio 3:7 v/v). The model data help explaining changes in the ¹³C NMR spectra of MWL and lignin in situ dissolved in spruce kraft black liquor caused by ionization. In the ¹³C NMR spectra of spruce black liquor the signals of phenolic and non-phenolic lignin units are clearly separated and do not overlap with the signals of the carbon atoms of carbohydrates and other aliphatic products of wood degradation. The data obtained are useful in understanding the important role of solvation and ionization processes leading to lignin solubilization.     

Modified Kraft Pulping of Bagasse: Infrared Spectroscopy of Lignin

Abstract

The infrared spectroscopy of precipitated lignin from waste black liquors of bagasse pulping with kraft sulfite pulping process was investigated. Also the effect of anthraquinon and methanol addition in the soda, kraft and kraft-sulfite pulping liquor on the infrared specra of the precipitated lignin was studied. The presence of methanol in the pulping liquor causes an increase in the degradation as well as increase in the carboxylic group in the precipitated lignin. Also, the phenolic hydroxyl group in case of kraft lignin is higher than soda lignin. Presence of sulfite in the kraft-sulfite pulping liquor produces lignin hydroxyl groups.     

四苄基二苯甲酰基六氮杂异伍兹烷的结构归属

利用^1H和^13CNMR(包括DEPT）及2D NMR（HMQC,HMBC,NOESY）技术确定了2,4,8,10-四苄基-6,12-二苯甲酰基-2,4,6,8,10,12-六氮杂四环[5.5.0.0^5.9.0^3.11]十二烷的结构。对其^1H和^13CNMR谱进行了全归属,并观察到一些有意义的远程^13C-^1H和^1H-^1H耦合。     

Characterization of Anacardium occidentale exudate polysaccharide

The composition, structure and molar mass distribution of Anacardium occidentale exudate polysaccharide of Brazilian origin was investigated. The composition from gas–liquid chromatography (GLC) and ¹³C NMR was 72% β-D -galactopyranose, 14% α-D -glucopyranose, 4·6% α-L -arabinofuranose, 3·2% α-L -rhamnopyranose and 4·5% β-D -glucuronic acid. A thorough analysis of high resolution ¹³C NMR spectra from intact, partially hydrolysed and Smith-degraded polysaccharide enabled reliable chemical shift assignments to be made, and indicated the presence of three types of unit within the branched galactan core: linked at C-1 and C-3, at C-1 and C-6, and at C-1, C-3 and C-6. The polysaccharide was fractionated with respect to molar mass using water/ethanol as a solvent/non-solvent system. The polysaccharide and fractions were characterized by gel permeation chromatography (GPC), intensity light scattering, dilute solution viscometry and sedimentation velocity. The intrinsic viscosity in 0·1M aqueous NaCl at 25°C was found to depend on molar mass according to: [η]/(cm³g^-1)=0·052M^0·42. The molar mass distribution for the whole polysaccharide, determined by GPC using a universal calibration, exhibited two main peaks at 28000 and 67000gmol^-1, together with traces of much higher molar mass material. © 1998 SCI.     

AlO4/SiO4 Distribution in Tetrahedral Double Chains of Mullite

The order–disorder of the tetrahedrally coordinated aluminum and silicon atoms in mullite has been investigated by means of ²⁹Si nuclear magnetic resonance (NMR) spectroscopy. Sinter (3/2) and fused (2/1) mullites in the as-received state and reheated at 1750°C, and a reference sillimanite were used for this study. All mullites display similar ²⁹Si NMR spectra: The strongest peak occurs at about −88 ppm, with two subpeaks close to −92 and −96 ppm. The −88 ppm signal is assigned to a sillimanite-type environment with three aluminum oxygen tetrahedra as next nearest neighbors of the silicon oxygen tetrahedra. The two ²⁹Si NMR signals near −92 and −96 ppm are assigned to silicon oxygen tetrahedra surrounded by two aluminum oxygen and one silicon oxygen tetrahedra, and one aluminum oxygen and two silicon oxygen tetrahedra, respectively. ²⁹Si NMR spectra with different short-range-order parameters were simulated by an array of 2 × 10 000 tetrahedral positions by means of an adapted random generator. The comparison between measured and simulated mullite and sillimanite ²⁹Si NMR spectra yields a moderate degree of tetrahedral aluminum–silicon order, with no tendency toward cation demixing.     

麦草碱法蒸煮黑液氮气加压热处理降黏技术

分别对麦草碱法蒸煮黑液热处理的用碱量、温度、保温时间三因素三水平和氮气加压热处理的用碱量、加热温度、保温时间、氮气压力四因素三水平方差分析工艺技术进行研究,发现温度对黏度的影响均是最大的,而保温时间和氮压对黏度的影响均比较小。另外,将处理后黑液浓缩至45%以上,氮气加压热处理的黑液黏度比单纯热处理的低,其原因将进一步研究。     

C NMR study of C-enriched single-wall carbon nanotubes synthesized by catalytic decomposition of methane

¹³C NMR spectra and spin-lattice relaxation times were measured for single-wall carbon nanotubes with 99.9 and 50.0% ¹³C enrichments and natural abundance (1.1% ¹³C) prepared by catalytic decomposition of CH₄. The ¹³C isotropic shift is about 116 ppm from tetramethylsilane, being estimated from magic-angle-spinning (MAS) spectra. The value does not depend on the degree of the ¹³C enrichment. The ¹³C MAS NMR spectra show two additional small peaks at 171 and 152 ppm, which are ascribed to carbon species at defects or edges. The line widths of the main isotropic peak in MAS spectra are about 30 ppm, the origin of which is mostly chemical shift dispersion, reflecting a distribution of diameter and helicity. The line width in the ¹³C static spectra originates from chemical shift dispersion, chemical shift anisotropy and dipole–dipole interactions between ¹³C spins as well as between ¹³C and ¹H spins at defects or edges. ¹H NMR spectra confirm the presence of H-containing species. The ¹³C spin-lattice relaxation is dominated presumably by interaction with magnetic impurities.     

Solid-State 13C CP/MAS NMR for Alkyl-O-Aryl Bond Determination in Lignin Preparations

Several lignin preparations (Freudenberg lignin, Björkman lignin, and Pepper lignin), technical lignins (soda, soda-AQ, Kraft, Kraft-AQ, and hydrolysis), dimeric lignin model compounds, and different polysaccharides (galactoglucomannan, arabinogalactan, xylan, and arabinan) were analyzed by means of solid-state ¹³C CP/MAS NMR. Signals assignment in solid-state NMR lignin spectra was performed on the basis of the conducted studies and earlier published data. It was established that there exists strong linear correlation (r = 0.985) between Alkyl-O-Aryl inter-unit bond content in lignin and integral signals intensity in NMR spectra in the range of chemical shifts of 96–68 ppm. The integral signals intensity was measured in correlation with the reference integral signals in the range of chemical shifts of 162–102 ppm, typical for aromatic carbon atoms. To eliminate the effect, caused by carbohydrates contained in lignin, the correction factor of 0.67% of the area of integration per 1% of carbohydrates was determined. It was shown that the solid-state ¹³C CP/MAS NMR method allowed to determine Alkyl-O-Aryl bond content in both soluble and insoluble lignin preparations, and also to determine methoxyl groups content in soluble preparations.     

有机胺制碱的回顾与展望

为提高钠利用率 ,5 0年代提出用有机胺替代氨碱法中的氨 ,称为有机胺制碱。它虽能显著提高钠利用率 ,但胺的再生使用一直没能解决。早期提出的石灰蒸馏胺再生法 ,仍有废液废渣产生。80年代前苏联提出的电化学胺再生法 ,其实质是电化学制碱 ,不仅消耗大量电能 ,同时产生出NaHCO3一半量的氯。 90年代提出的胺盐热分解再生法 ,因制碱速度受控于气体的热扩散速度 ,使生产成本提高 ,生产强度受到限制。有机胺制碱要替代氨碱法成为胺碱法 ,需另辟新路解决上述问题     

氯化钙生产中蒸发器结垢及处理方法探讨

利用氨碱法制碱系统蒸氨废液为原料生产氯化钙的过程中,蒸发器组产生难以清除的ＣａＳＯ４沉淀是生产中一大难题。本文从理论和实践的角度,探讨了结垢的原理、延缓结垢的措施及清除方法。     

Amber: the organic gemstone

Resins are produced by woody plants on a worldwide basis. We have found several distinct classes of modern diterpenoid resins based phenomenologically on the solid-state (13)C NMR spectra of the bulk material. Resin fossilizes over millions of years into a robust material sometimes called amber. We have characterized several hundred samples of fossil resin by solid-state (13)C NMR spectroscopy. We can relate one globe-spanning group of fossil resins to the modern genus Agathis, based on spectral evolution over time. A second large group has not been related with certainty to specific modern plants. Fossil resins from Europe fall into two categories, the famous Baltic ambers and another that resembles the Agathis group. Fossil resins from the Americas and Africa are closely related to the modern genus Hymenaea. Based on spectral distinctions, fossil resin found in an archaeological context sometimes can be assigned to a specific geographical origin on the basis of its (13)C NMR spectrum.     

用13C-NMR研究气相法乙烯-丁烯共聚物

用核磁共振（＾１３Ｃ－ＮＭＲ）研究了不同丁烯投料量的气相法乙烯－丁烯共聚物，给定了＾１３Ｃ－ＮＭＲ各吸收峰化学位移归属，计算了乙烯－丁烯共聚物的三元序列分布、链节数和链节长度。用沸己烷抽担乙烯－丁烯共聚物，对不溶物、可溶物的＾１３Ｃ－ＮＭＲ谱研究表明，经抽提后不溶物分子链中丁烯链节减少了，惭烯链节增加；可溶物分子链中丁烯链节增加，乙烯链节减少。＾１３Ｃ－ＮＭＲ研究表明，对不同丁烯投料量的乙烯－丁烯     

Soda Pulping of Hardwoods Catalyzed by Anthraquinone and Methyl Substituted Anthraquinones

Abstract

Black liquor gasification (BLG) as well as the recovery of lignin and other organic compounds from pulping black liquor would be aided if an efficient sulfur‐free pulping process could be developed. This has provided new impetus for research on soda pulping with redox catalysts instead of sodium sulfide that is presently used in the kraft process. Soda/anthraquinone (AQ) pulping afforded white birch (Betula papyrifera) and sugar maple (Acer saccharum) pulps with equal if not superior strength to kraft pulps. However, the delignification rate was significantly lower for soda/AQ pulping. When AQ was replaced by 2‐methylanthraquinone (2‐MAQ) a delignification rate only slightly lower than that of kraft pulping was obtained at the same effective alkali (EA). At a kappa number of ～20, a soda/2‐MAQ pulp was produced from sugar maple at a higher yield (1.2% on chips) than for a kraft pulp. 2‐MAQ was synthesized, as a powder, at 75% yield using an AlCl₃–mediated Friedel‐Crafts reaction that is one of the methods used for commercial production of AQ.     

Properties of Soda Aluminosilicate Glasses: II, Internal Friction

Internal friction measurements of soda aluminosilicate glasses, the physical properties of which were reported in Part I of this series, are discussed. The low- and intermediate-temperature internal friction peaks were studied in detail and are shown to be due to the stress-controlled movement of the sodium and nonbridging oxygen ions, respectively. A close correlation was found between the temperature shift of the low-temperature peak and the activation energy for electrical conduction in the soda aluminosilicate glasses. The magnitude of the low-temperature peak was found to depend more on the structural environment of the sodium ions than on the actual soda content. Changes in the intermediate-temperature peak are explained on the basis of the structural model proposed for these glasses.     

Absorption and emission spectra of Athabasca asphaltene in the visible and near ultraviolet regions

Absorption, excitation and emission spectra in the visible and ultra-violet region were recorded at room temperature for Athabasca (Alberta, Canada) asphaltene and five of its fractions separated according to molecular weight (MW) by gel permeation chromatography (g.p.c.) on Bio-Beads SX-1. Strong concentrations effects were observed on the profiles of all the excitation and emission spectra at concentrations higher than 5.0 mg l⁻¹. The proper excitation and emission spectra were taken at concentrations lower than 5.0 mg l⁻¹ where the profiles are independent of concentration. All the spectra obtained were broad, structureless bands with the exception of that of the lowest MW fraction, which shows the sharp Soret band characteristic of the vanadyl porphyrin complex. The absorbance of the whole asphaltene was found to be equal to the weighted sum of absorbances of the fractions at a given wavelength and a given weight concentration. This additive property was not observed among the intensities in the emission spectra. The profiles of all the excitation and absorption spectra are identical throughout the asphaltene fractions, suggesting that the basic absorbing chromospheres are the same throughout the fractions and independent of MW of the fractions. In addition the absorption spectra are not significantly affected by the Tyndall scattering. From the examination of absorptivity and the position of the absorption band, the average number of aromatic rings in the average absorbing chromophores throughout the fractions was found to consist of approximately two to three. The fluorescence spectra, on the other hand, show a very rapid decrease of intensity at a constant weight concentration and a gradual shift of the band maxima toward longer wavelength with increasing number average MW. The origin of the fluorescence band is considered to be exciplexes. The average rate of non-radiative processes decreases steadily with decreasing MW from fraction 1 to fraction 5. The influence of various solvents was explored on the absorption, excitation and emission spectra of the lowest MW (1200) asphaltene fraction.     

NMR研究PMMA的序列分布

采用13C-NMR对自由基聚合得到的聚甲基丙烯酸甲酯(PMMA)进行了结构表征,对其中羰基碳裂分峰的积分面积进行了计算,归属了其三单元组和五单元组的结构,并将三单元组和五单元组的分数与Bernolli和Markov模型的计算值加以对照。结果表明:该PMMA的序列分布符合一级和二级Markov过程,但与Bernolli统计模型存在一定的偏差。     

氨化-碳酸化法开发天然盐碱湖的相图研究

将盐碱湖的卤水氨化,然后碳酸化,可以大大提高钠利用率.为了研究其最适条件,特研究了Na~+、NH_4~+/HCO_3~-、Cl~-、SO_4~(2-)、H_2O体系相图,并以此对如何提高钠利用率进行了讨论.     

1H‐ and 13C‐NMR spectroscopic study of chemical equilibria in the system acetaldehyde + water

Acetaldehyde is an important intermediate in the chemical industry and often used in mixtures with water. These mixtures are reactive multicomponent systems, as acetaldehyde forms oligomers with water. Quantitative studies of the resulting speciation are scarce in the literature and limited to the formation of the smallest oligomer, ethane‐1,1‐diol. Therefore, in the present work, a comprehensive study of chemical equilibria in mixtures of acetaldehyde and water was carried out by quantitative ¹H‐ and ¹³C‐NMR spectroscopy. The study covers temperatures between 275 and 338 K and overall acetaldehyde mole fractions between about 0.05 and 0.95 mol/mol. The peak assignment is given for both the ¹H‐ and ¹³C‐NMR spectra. From the speciation data, obtained from the peak area fractions, numbers for the chemical equilibrium constants of the oligomer formation are obtained and a correlation is presented. © 2014 American Institute of Chemical Engineers AIChE J, 61: 177–187, 2015     

综合利用联碱厂废液副产白炭黑工艺研究

本文叙述了采用联碱生产过程中的外排废液与水玻璃反应,制取工业白炭黑的工艺条件及其优化,产品质量符合ＧＢ１０５１７－８９橡胶配合剂标准。此项研究对治理联碱生产过程环境污染,化废为宝方面进行了有益的探讨。