预热处理对褐煤热解过程氧元素迁移的影响

以中国呼伦贝尔褐煤为原料,基于工业分析、元素分析、傅里叶变换红外光谱、气相色谱-质谱联用分析,考察140-230℃预热处理对褐煤650℃等温热解氧迁移的影响。结果表明,与未经预热处理的干煤热解相比,褐煤经200℃预热处理后热解,迁移至热解水和半焦中的氧分别下降7.55%和1.43%,迁移至焦油和气体中的氧分别增加6.66%和1.61%,焦油中酚类氧增加一倍。褐煤预热过程中氢键的减少与热解焦油中正己烷可溶物所含酚类化合物的增加,经原位红外漫反射光谱分析,发现源自OH…π、OH…N和羟基自缔合氢键在预热过程中断裂形成自由OH·,导致酚类化合物中苯酚和甲酚含量增加。     

溶剂溶胀对鄂尔多斯褐煤结构及热解产物分布的影响

采用四种有机溶剂对鄂尔多斯褐煤进行溶胀预处理并在粉-粒流化床上进行快速热解,探究溶胀对褐煤结构及热解特性的影响。采用傅里叶变换红外光谱仪、热重分析仪、气相色谱-质谱联用仪、固体核磁、X射线衍射、全自动化学吸附仪等仪器对溶胀煤及热解产物进行表征。结果表明,非极性溶剂对煤结构影响较小。极性溶剂可以降低褐煤含氧官能团的氢键交联,增加小分子的流动性,增加煤的平均孔径。溶胀后的煤热解焦油和气相产率提高,热解水产率降低。与原煤相比,极性溶剂甲醇、丙酮、四氢呋喃处理煤样的热解焦油产率分别提高了18.88%、26.72%、33.58%,焦油的轻质组分中酚类、单环和双环类芳香烃组分含量明显增加。     

外加铁矿石对哈密低阶煤热解特性影响

为探讨铁矿石对哈密低阶煤热解特性影响,采用热重分析仪(thermal gravity analysis/differential thermal gravity,TG/DTG)和实验室固定床反应器(fixed bed)对哈密低阶煤进行热解实验,研究了两种铁矿石对哈密煤热解反应性、热解气和焦油分布规律的影响。利用傅里叶红外光谱(FT-IR)和色谱-质谱分析仪(GC-MS)对焦油中官能团的变化以及焦油中物质组成进行了分析对比。结果表明,当热解温度从室温升高至150℃时,原煤中添加铁矿石的煤样失重速率峰逐渐向高温阶段推移;当热解温度高于450℃时,不同铁矿石对原煤热解的催化作用差异更加明显,且镜铁矿原生矿物质赤铁矿;当两种铁矿石添加量分别为20%时,热解焦油和热解气都能得到较高的收率;对于煤样HM-JT来说,此时焦油产率为7.88%,热解气相产物H_2、CO_2、CH_4、CO产率与未添加镜铁矿的原煤煤样相比分别提高了4.27%、3.76%、4.39%、3.61%。对于煤样HM-CT来说,焦油催化裂解效果一直受到铁矿石添加量的影响。在镜铁矿和赤铁矿添加量分别增加到20%的过程中,煤样热解生成焦油的产率逐渐下降,而轻质焦油产率和轻质焦油分数逐渐增大到6.37%、58.48%、5.34%、56.22%,焦油中氧脱除率分别达到43.16%、36.89%。随着铁矿石的加入,焦油中二甲苯相对含量由4.32%分别降低至3.78%、3.93%,而甲苯相对含量由1.11%升高至1.32%、1.45%;焦油中邻甲酚和二甲酚中分子中的甲基取代基被脱除生成苯酚或甲酚,且镜铁矿对焦油中苯系物和酚类化合物的脱甲基作用强于赤铁矿。     

先锋褐煤在水热处理过程中的结构演绎

以先锋褐煤(XF)为原料,在高压反应釜中考察了水热处理过程中褐煤的结构变化,通过13C固体核磁共振(NM R)和傅里叶变换红外光谱进行了分析表征。结果表明,在低于240℃的水热处理条件下,煤有机分子结构中的弱化学键有一定断裂,含氧官能团逐步减少;水中氢以离子形态迁移至褐煤中,处理后褐煤结构中甲基比例先增加后减少,次甲基比例由原煤的4.80%增加至XF-240的13.16%;释放的气体中主要是CO_2,烃类气体组分随处理温度的升高略有增加。当水热处理温度高于240℃时,褐煤中部分共价键开始断裂,释放的烃类气体(C1-4)由240℃时的2.13%增加至300℃时的8.59%,脂肪碳比例由XF-240的44.83%降低至XF-300的39.49%,与氧连接的碳比例由XF-240的12.57%降低至XF-300的1.49%。水热处理对褐煤的脱氧提质效果显著,300℃时氧含量降低约30%,芳香碳比例增加至60.50%,比原煤提高19%。     

橄榄石基固体热载体影响褐煤热解产物分布的分析

为了提高固体热载体煤热解工艺中焦油的品质,降低焦油中沸点大于360 ℃的重质组分含量,本实验采用固定床反应器,在450~600 ℃下进行褐煤固体热载体快速热解反应.分析对比了橄榄石基和石英砂固体热载体对褐煤热解产物收率、焦油馏分、气体组成的影响.结果发现,Co能改变煤内部挥发分氢元素的分布,橄榄石负载Co热载体能将焦油中重质组分转化为轻质焦油和热解气.热解温度为550 ℃时,与橄榄石相比,负载Co的橄榄石固体热载体使焦油收率提高了19.2%.与石英砂相比,负载Co的橄榄石固体热载体使焦油中重质组分含量降低了17.0%,轻质组分收率达5.1%,其中,轻油、酚油和萘油分别提高了19.6%、17%和15.2%,气体产物中H₂、CH₄含量下降.     

昭通褐煤的热解提质及其对气化反应性能的影响

为了对储量相对丰富的昭通褐煤进行合理有效的分级转化利用,采用固定床程序升温热解的方法研究了不同温度下煤的热解行为,借助GC-MS和拉曼光谱对所得焦油和煤焦进行了表征分析,并在850℃下对不同热解温度制得的煤焦进行了水蒸气等温气化特性评价。结果表明,热解温度为700℃时,热解气体有效组分(H_2、CO、CH_4)的累积物质的量占总释放量的70%,此温度下热解气低位热值增长速率最快(以500℃下热解气低位热值为基准计算,其值为90%);酚类化合物在500-700℃大量生成析出,而温度高于700℃时,酚类化合物的分解反应加剧。不同热解温度下所制煤焦的表观气化反应速率随热解温度的升高不断降低,气化产物中CO_2与CO的物质的量逐渐升高,700℃热解制得的煤焦在水蒸气气氛下气化所得合成气中有效组分H_2与CO的比率最高。     

折流内构件移动床中煤在不同停留时间下的热解行为特性

针对常规移动床煤热解工艺所面临的无法处理粉煤,轻质焦油产率低、焦油品质差等问题,开发了折流内构件移动床热解工艺来调控气固两相的热质传递和热解反应过程。利用多段集气系统可及时地收集煤在不同热解阶段释放出的油气产物,研究了淖毛湖煤在不同温度和停留时间下的热解行为特性和产物品质。结果表明,折流内构件强化了颗粒间的热量和挥发分物质的传递,使其可处理0.4-6.0 mm的粉煤;在热解温度550℃,停留时间为3.0 h时,热解焦油产率达到最高为11.38%(占格金焦油产率的86.87%,质量分数),焦油馏分中低于360℃的轻质组分质量分数为85.0%;随着停留时间的延长,热解气中的H2体积分数从22.1%增加到了35.1%,CO体积分数从8.0%增加到了9.5%;在第一和第二层反应器中的焦油产率随停留时间的延长而增加,在第三和第四层反应器内当停留时间为2.0 h时焦油产率最大;随着床层数的增加,焦油模拟蒸馏馏分中的轻质组分含量增加,焦油脂肪烃化合物含量减小,而单环芳烃和二环芳烃的含量逐渐增加。     

热解和加氢热解煤焦油的组成和煤结构的关系

用色谱质谱联用技术测定了兖州烟煤和红庙褐煤在氮气下热解和加氢热解焦油的组成。在４５０℃～６５０℃的温度范围内考察了温度对热解和加氢热解苯类、酚类、萘类化合物产率的影响。结果表明兖州煤热解和加氢热解焦油中的正构烷烃以Ｃ８～Ｃ１０占优势，红庙煤中以Ｃ１７～Ｃ２０占优势。从热解产物看兖州煤和红庙煤的主体分子结构有着显著差别，兖州煤主要以稠环芳烃为主，其中的氧以氧杂环的形式掺杂在稠环结构中；红庙煤含有较多的酚羟基、酮、醚等官能团与碳骨架相连。加氢热解可以有效的脱除焦油中含氧、含硫官能团，改善焦油质量。     

热预处理影响褐煤热解行为研究

采用固定床反应器研究了不同气氛热预处理对内蒙胜利褐煤结构的改变,及其对后续热解行为的影响。结果表明,与原煤相比,热预处理后煤中羟基含量和芳香氢与脂肪氢的比减少,脂肪氢的相对含量增加。与未经处理的煤热解相比,N2、N2+O2、CO2气氛下热预处理后热解水收率下降,热解气收率增加,热解气中CO2含量增高,导致高位热值下降。过热水蒸气热预处理后,焦油质量收率提高3～4个百分点。热解焦油组成的变化与预处理气氛、温度密切相关,过热水蒸气200℃下预处理使得焦油中轻质组分的含量(沸点低于360℃的馏分)比原煤焦油提高了约27个百分点;水蒸气和模拟烟气混合气氛下在200℃及250℃预处理后,其热解焦油中轻油和酚油含量分别提高约60和42个百分点。     

预脱氯处理PVC残渣和平朔煤共热解的协同效应研究

热解是煤炭清洁高效利用的有效途径,也是处理废旧塑料高效转化的重要方式。本文针对无害化处理困难的含氯塑料,以聚氯乙烯(PVC)和平朔煤为研究对象,提出将PVC先经预热处理脱除大部分氯,然后将预处理后的PVC残渣与煤进行共热解,并利用气相色谱(GC)、模拟蒸馏、GC-MS、元素分析、红外光谱及拉曼光谱等对热解产生的气体、焦油以及半焦的组成和性质进行分析表征。结果表明,预脱氯处理后的PVC和平朔煤的共热解过程存在协同效应,共热解对半焦和焦油的形成具有明显的正协同作用,焦油产率实验值比理论计算值最大高3.35%;而对热解水和气体的形成产生负协同作用,其中,CH_4产率下降最多,即出现最强的负协同效应;共热解使焦油中轻质焦油含量提高,其中,萘类物质含量显著增加,沥青减少,当预脱氯处理PVC添加量为10%时,轻质焦油含量比理论计算值提高5个百分点。此外,共热解半焦表面更为光滑,结构变得更加有序,石墨化度提高。     

Basicity of the nitrogen atom and of the carbonyl function of methyl isonicotinate and 4-acetylpyridine. An infrared study of the interaction with proton donors

The hydrogen bonded complexes between methyl isonicotinate and 4-acetylpyridine and phenol derivatives acting as proton donors have been investigated by ir spectroscopy. The thermodynamic parameters (K, — ΔH°, — ΔS°) have been determined. The ir data show that the hydrogen bond interaction occurs at the carbonyl function and at the nitrogen atom of the ring. When the acidity of the proton donor increases, N-complexation is favoured over carbonyl complexation and with the stronger acid hydrochloric acid, only N-protonated species are observed. The data are compared with those obtained for closely related pyridine derivatives, bearing a X-C=O substituent and it is shown that the proportion of OH···N and OH···O=C species is related to the basicity of the nitrogen atom of the heterocyclic ring and to inductive and mesomeric effects depending on the nature of X.     

Miscibility and intermolecular specific interactions in thermosetting blends of bisphenol S epoxy resin with poly(ethylene oxide)

Thermosetting blends composed of phloroglucinol‐cured bisphenol S epoxy resin and poly(ethylene oxide) (PEO) were prepared via the in situ curing reaction of epoxy in the presence of PEO, which started from initially homogeneous mixtures of diglycidyl ether of bisphenol S, phloroglucinol, and PEO. The miscibility of the blends after and before the curing reaction was established on the basis of thermal analysis (differential scanning calorimetry). Single and composition‐dependent glass‐transition temperatures (T_g's) were observed for all the blend compositions after and before curing. The experimental T_g's could be explained well by the Gordon–Taylor equation. Fourier transform infrared spectroscopy indicated that there were competitive hydrogen‐bonding interactions in the binary thermosetting blends upon the addition of PEO to the system, which was involved with the intramolecular and intermolecular hydrogen‐bonding interactions, that is, OH···O?S, OH···OH, and OH, versus ether oxygen atoms of PEO between crosslinked epoxy and PEO. On the basis of infrared spectroscopy results, it was judged that from weak to strong the strength of the hydrogen‐bonding interactions was in the following order: OH···O?S, OH···OH, and OH versus ether oxygen atoms of PEO. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 359–367, 2005     

Insights on structural characteristic of Xilinguole lignite chars from low-temperature pyrolysis

The cleavage behavior of covalent bonds in Xilinguole (XLGL) lignite and changes in chemical structure of lignite and its chars during low-temperature pyrolysis were investigated by thermogravimetric (TG) analysis and Fourier-transform infrared (FTIR) spectroscopy. Based on the TG and differential thermogravimetric (DTG) analysis results, the cleavage of different types of chemical bonds in lignite occurred mainly at four certain temperatures, 170 °C, 376 °C, 432 °C, and 521 °C. The latter three were selected as the final pyrolysis temperatures of chars evaluated in this study. The FTIR analysis results indicate that thermal treatment increased the relative content of two and three adjacent H deformation structures but decreased that of four adjacent H deformation structure. This was caused by the cleavage of C_al–C_al and C_ar–C_al bonds. The oxygen-containing functional groups in lignite are dominated by C–O and C–OH groups with a lower chemical reactivity than C=O–C and conjugated C=O groups. Moreover, XLGL lignite has the highest ratio of CH₂/CH₃ which declines with increasing temperature, indicating the decrease in the length of aliphatic chains and increase in the degree of branching of aliphatic side chains. This change mainly resulted from the cleavage of C_al–O, C_al–C_al, and C_ar–C_al bonds. Furthermore, XLGL lignite and its chars contain five specific hydrogen bonds: OH–N, cyclic OH, OH–ether O, OH–OH, and OH–π hydrogen bonds. The relative content of OH–OH hydrogen bond was the highest, indicating that OH–OH hydrogen bond has the highest thermal stability.

     

Hydrogen bonding and the protonation site in 3-methyl-4-pyrimidone

The interaction between 3-methyl-4-pyrimidone and phenol derivatives or HBr has been studied by IR spectrometry in solution and in the solid state. For pK_a values ranging from 10.3 to 4.5, normal OH··· OC hydrogen bonds are formed. With stronger acids (PK_a = 0.4 to ?6) protonation occurs at the N(1) nitrogen atom of the ring. For phenols of intermediate pK_a values (3.5), there is no preferred site of interaction, both OH···OC and NH⁺···O^? bonds being formed in solution.     

Hydrogen-bonding interaction in a complex of amino acid with urea studied by DFT calculations

Theoretical studies on hydrogen-bonded complexes between amino acids (glycine, alanine, and leucine) and urea in gas phase have been carried out using density functional theory (DFT) and ab initio methods at the B3LYP/6-311++g** and MP2/6-311++g** theory levels. The structures, binding energy, Chelpg (charges from electrostatic potentials using a grid-based method) charge distribution, and bond characteristics of the mentioned complexes were calculated. Urea is a good H-bond donor and an excellent receptor for highly electronegative atoms like O and N, through the formation of two or more hydrogen bonds. The NH₂ and COOH groups of amino acids can form several different types of H-bonds with urea molecular, as well as C^αH and alkyl side chains. The calculated high binding energy also suggests multiple H-bonds formed in one complex. The OH···O contact is the strongest hydrogen bond interaction with H···O separation around 1.65 Å and its relevant angle close to 176°. The closely linear amide H-bonds NH···O and OH···N strongly stabilize the amino acid–urea complex with H···O separation between 1.89 and 2.38 Å. The weaker CH···O/N H-bonds are also discussed as significant interaction in biological systems involving amino acids.     

Two polymorphic modifications of 1-(N-morpholiniomethyl)spirobi- (3-oxo-2,5-dioxa-1-silacyclopentan)- ate hydrate

The compound 1-(N-morpholiniomethyl)spirobi(3-oxo-2,5-dioxa-1-silacyclopentan)ate crystallizes from aqueous solution of γ-butyrolactone in the form of two crystal hydrate modifications: monoclinic (with D = 1.53 g/cm³, space group P 2₁/n) and triclinic (D = 1.45 g/cm³, space group P1^-). For the monoclinic form, an X-ray structural study at -100°C has been performed. For both structures the coordination polyhedron of the silicon atom is a trigonal bipyramid. In the crystal structures there are strong intermolecular hydrogen bonds of NH···O and OH···O types.     

A comparative study of the dimers of selected hydroxybenzenes

Hydroxybenzenes are the parent compounds of large classes of derivatives, many of which exhibit biological activities. This work presents the results of a comparative study of the dimers of selected hydroxybenzenes, considering all the possible mutual geometrical arrangements of the two monomers and comparing their relative stabilities and interaction energies. The OH···OH hydrogen bond between the two monomers is the dominant stabilizing factor, with frequent preference for mutual perpendicularity of the two aromatic rings. C? H···O unconventional H‐bonds, OH···π unconventional H‐bonds, H···π interactions and π··π interactions also may play significant roles. The factors stabilizing individual hydroxybenzenes (presence of intramolecular hydrogen bonds; number, positioning and orientation of the OH groups; symmetry features) have greater influence on the dimers' relative energy than on the interaction energy between monomers. While results from different calculations methods (HF, MP2, and DFT/B3LYP) show consistency for all the features just‐mentioned, they show some relevant differences in the way they take into account different types of interactions between monomers, resulting in some differences in the geometry arrangements of the monomers in the lowest energy dimers and in differences in the relative preferences among higher‐energy dimer geometries. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012     

Cellulose Iβ investigated by IR-spectroscopy at low temperatures

Highly crystalline oriented Halocynthia roretzi cellulose Iβ films were investigated by IR-spectroscopy between ?180 and +10 °C. Changes in the IR-spectra induced by temperature were compared to published changes induced by mechanical stretching. This made it possible to conclude that frequency shifts in the O–H stretching region of the IR-spectra due to temperature were not predominantly an indirect effect of thermal expansion leading to greater O–O distances, but were due directly to the effect of temperature on the O–H···O hydrogen bonds. Temperature induced frequency shifts of C–H stretching bands were consistent with the presence of weak inter-sheet C–H···O bonds. Furthermore, no phase transition in cellulose Iβ was found between ?180 and +10 °C.     

煤基和石油基C7-沥青质的结构特征及缔合行为

采用核磁(NMR)、小角散射分析(SAXS)、X射线光电子能谱(XPS)、改进的B-L法等手段,研究了煤基C7-沥青质(CT-asp)和石油基C7-沥青质(M-asp)两类沥青质的化学组成、官能团和分子结构等组成结构特征以及差异性,进而通过极性溶剂中沥青质稳定参数研究两类沥青质的缔合行为和聚集体尺寸以及两者之间的氢键和酸碱作用。结果表明,CT-asp分子芳香环数较少且有较多短烷基侧链,且芳香度较高,较高含量氧杂原子以芳香醚和酚羟基赋存形态为主;而M-asp的芳香核尺寸和平均相对分子质量明显高于CT-asp,芳香环数虽较多且有较多长烷基支链,且芳香度较小;两类沥青质缔合聚集程度关联物质的量比(n_(CT-asp)/n_(M-asp))及其分子结构特征,源于杂原子官能团的氢键和酸碱作用是两类沥青质缔合的主要作用力。     

INTRAMOLECULAR OH···S HYDROGEN BONDS AND MOLECULAR CONFORMATIONS IN 2-METHYLMERCAPTOETHANOL

Abstract

The infrared absorption spectrum of monomeric 2-methylmercaptoethanol in dilute CC1₄, solution exhibits four overlapped bands in the fundamental OH stretching region. The individual band components were resolved using digital computing techniques [1], and the relative band intensities are temperature dependent. The “free” OH bands at 3634 and 3623 cm correspond to gauche and trans orientations about the C-O bond, respectively, by analogy with similar band components in the infrared spectrum of ethanol in dilute CC1₄, solution. The OH bands at 3539 and 3446 cm^?1 are assigned to gGt and gGg¹ conformers, respectively, each involving an intramolecular OH···S hydrogen bond (conformer notation refers to the orientation about the C-O, C-C and C-S(CH₃) bonds, respectively). A similar interpretation of the matrix isolated infrared spectra of ethylene glycol, involving two conformers with intramolecular OH···O hydrogen bonds and differing principally in the orientation of the proton-acceptor OH group, has been presented recently [2]. The microwave spectrum of 2-mercaptoethanol in the vapour phase arises from an all-gauche conformation with an intramolecular OH···S hydrogen bond [3].