枣泉煤分子模型构建及热解的分子模拟

以宁东枣泉煤为研究对象,使用工业分析、元素分析、X射线光电子能谱、~(13)C固体核磁等表征手段和计算机辅助,构建获得枣泉煤大分子结构模型。经过分子动力学退火动力学模拟和几何结构全优化,与初始结构相比键长、键角发生明显改变,立体构型显著,芳香层片之间近似平行的排列方式明显。获得的傅里叶变换红外和~(13)C固体核磁的实验与计算谱图总体吻合较好,进一步证明了构建模型的合理性。使用反应分子动力学方法模拟枣泉煤的热解过程,考察不同热解终温和升温速率对热解行为的影响。结果发现,随着温度的升高,反应速率逐渐加快。不同升温速率对枣泉煤热解过程中气体的产生有显著影响。在动力学模拟中大多产生C_(15)以下的碎片,大分子的种类则并不多。随着升温速率的增加,气、液、固三相产物整体上都呈现下降的趋势。此外,还根据反应分子动力学模拟结果追踪了热解过程中CO_2的形成机理,获得了三种不同的CO_2形成路径。     

典型宁东煤热解阶段硫迁移路径的分子动力学模拟

以典型宁东煤为研究对象,采用工业分析、元素分析、X射线光电子能谱(XPS)分析和¹³C固体核磁共振(¹³C-NMR)等手段研究了煤样的元素组成、原子比、官能团类型及含量等分子结构特征,构建了含硫原子的宁东煤有机化学结构。通过反应力场分子动力学(ReaxFF MD)模拟,考察了热解温度和升温速率对典型宁东煤热解产物的影响,结果表明:热解温度低于1500 K时,热解产物中气体组分较少,重质焦油较多;随着热解温度升高(1500 K~2500 K),大分子化合物和活性自由基均会发生二次反应产生小分子碎片,气体产物快速增加;增大升温速率会减少C1~C4有机气体的生成,促进重质焦油的产生;16 K/ps和2500 K分别是合适的模拟升温速率和热解温度。污染性元素S的迁移路径分析结果表明:宁东煤热解过程中S原子容易迁移到相对分子质量小的有机碎片中,最终将以硫氢根的形式与H自由基结合生成H₂S参与后续燃烧反应。     

五彩湾煤和吐鲁番煤热解动力学模型评估与应用

煤热解是煤热加工利用的基础反应,热解动力学模型有助于预测煤在热解过程中挥发分脱除规律,当前文献中已报道了多种热解动力学模型,厘清不同热解模型参数选择的差异,评估不同模型对煤种及热解反应适应性可为热解工艺设计提供参考。采用¹³C NMR核磁共振测量了五彩湾煤和吐鲁番煤的碳化学结构,并使用热重法测量了不同加热速率下的两种低阶煤失重曲线,结合分段式单一速率扫描法、等转化率法和3段式高斯分布活化能模型（3-DAEM）分析热重实验数据。结果表明单一速率扫描法得出的动力学参数难以准确揭示热解反应机理;等转化率法可以较好地得出热解活化能及指前因子分布图;将等转化率方法获得的指前因子赋值给分布活化能模型,可以避免分布活化能模型指前因子选择的盲目性;3-DAEM模型仅需要一条TGA曲线便可获得适用于整个加热速率的动力学参数,其预测结果与实验数据吻合最好,且模拟得出的活化能分布图很好地反映了煤热解三个阶段特征。     

基于热重-红外联用技术分析油酸的热解特性及动力学分析

利用热重红外联动技术（TG-DTG-FTIR）研究了橡胶籽油中的单不饱和游离脂肪酸油酸组分在不同升温速率（5℃/min、10℃/min、20℃/min、30℃/min）下的热解特性。然后,用多元线性回归法对油酸非等温热解所得到的特性参数进行研究并计算,求得不同升温速率下对应的反应级数、活化能和指前因子,并对不同升温速率下油酸热解反应活化能和指数前因子作线性拟合。结果表明：油酸热解过程主要可分为0～268℃和268～300℃两个阶段,由红外谱图特征峰的分析可知,不同升温速率下,在油酸热解的阶段内均出现了水蒸气、CH₄、CO₂和CO这4种主要气体挥发分。随着升温速率的增大,油酸热解的最大失重速率随之增大,热解区间也向着高温段移动,同时计算在升温速率从5～30℃/min的过程中,反应级数n=1时,热解反应活化能由105.57kJ/mol降低至93.99kJ/mol,指数前因子由6.99×10⁶降低至6.7×10⁵;n≠1时,热解反应活化能由102.45kJ/mol降低至93.38kJ/mol,指数前因子由3.13×10⁶降低至2.97×10⁴,反应活化能和指数前因子随升温速率的增大出现明显减小。通过对不同升温速率下油酸热解反应的活化能和指数前因子进行线性拟合后发现,两者间具有较好的补偿效应。     

利用TG-FTIR研究造纸黑液碱木质素的热解机理

采用热重-傅里叶红外光谱（TG-FTIR）联用的分析方法对造纸黑液碱木质素的热解失重特性和产物生成特性进行了研究。结果表明：碱木质素热解失重过程可分为3个阶段,其中200~500℃是碱木质素主要的热解挥发阶段,反应符合一级反应动力学模型,利用Coats-Redfern动力学模型计算得出不同升温速率下热解主反应的表观活化能为39.3~43.1 kJ/mol。FTIR的实时分析结果表明：碱木质素热解的气态产物主要有H₂O、CO₂、CO、CH₄、甲醇、酚类和N₂O;产物中的CH₄、甲醇、酚类和N₂O主要在300~500℃区间内释放,随着热解温度的升高,这些气态产物在420℃附近集中释放,且产量达到最大。     

油页岩热解的FG-DVC模型

为研究油页岩结构与热解反应性之间的关系,在TG-FTIR分析仪上对甘肃油页岩在不同升温速率条件下（5、20、50℃·min^-1）进行了热解实验研究,对CH₄、CO、CO₂、H₂O和页岩油进行了定量分析,并采用非线性最小二乘拟合方法求解各组分析出的动力学参数,同时采用基于燃料化学结构的FG-DVC模型对各组分的析出过程进行了模拟。结果表明：油页岩的脱挥发分过程主要发生在200～600℃之间;油页岩中有机质所含官能团以脂肪烃为主;由于各官能团活性不同,导致气态产物的析出有先后顺序;由非线性最小二乘拟合方法获得的各种产物析出的活化能E分布在188～239 kJ·mol^-1之间,而指前因子A在10⁹～10¹³ s^-1之间;各产物的FG-DVC模拟结果与实验数据较为相符,这说明用FG-DVC模型来描述甘肃油页岩的热解脱挥发分过程是比较合适的。     

铁基载氧体纤维素化学链解聚试验及分子模拟

为探索纤维素在铁基载氧体作用下的化学链解聚机理及过程。通过热重分析试验研究不同升温速率下纤维素的化学链燃烧特性；通过化学反应动力学计算纤维素化学链燃烧过程中的活化能并揭示其动力学机制；利用ReaxFF MD模拟综合技术从微观原子尺度阐释纤维素化学链燃烧过程微观反应网络。热分析结果表明，铁基载氧体的加入可降低纤维素化学链解聚的起始温度，其释放的晶格氧有助于促进纤维素的化学链解聚。纤维素化学链燃烧过程分为3个阶段：挥发分析出燃烧、半焦转化燃烧和焦炭燃烧阶段。反应动力学研究显示，纤维素在热转化过程中不同转化率下的活化能为220～405 kJ/mol,其中第3个阶段的反应活化能最高。ReaxFF MD模拟结果显示，纤维素化学链燃烧过程整体遵循自由基链反应理论。纤维素裂解产生的活性自由基与载氧体释放的晶格氧反应生成2-羟基丙酮等中间体，然后进一步发生自由基反应生成CO₂。最终获得了载氧体作用下纤维素化学链解聚过程中CO₂生成释放的复杂反应网络。     

油坊梁煤加压热解特性的实验研究

为考察不同热解条件对煤加压热解产物分布和产品品质的影响，利用加压热重装置研究了不同升温速率(10℃/min, 20℃/min, 30℃/min, 40℃/min)、压力(1.0 MPa, 2.0 MPa, 3.0 MPa, 4.0 MPa)和气氛(100%N₂,100%CO₂,50%CO₂+50%H₂)对油坊梁煤加压热解特性的影响。结果表明：在反应终温800℃、升温速率30℃/min、100%N₂条件下，受加压抑制挥发分的逸出与扩散的影响，失重曲线、失重速率曲线及最大失重速率对应的峰温整体向高温侧移动，失重率由1.0 MPa时的24.52%减小至4.0 MPa时的19.46%。与100%N₂气氛相比，100%CO₂和50%CO₂+50%H₂气氛下失重率分别增加2.29%和1.32%。受高氢分压下较多的氢分子参与自由基的加氢饱和、高压促使挥发分发生二次反应，以及CO₂与重...     

印尼油砂热重红外及基于AKTS动力学分析

通过热重分析仪、傅里叶红外光谱仪和质谱仪对印尼油砂的热解过程和热解产物进行了探究,基于不同升温速率下的TG-DTG曲线,将热解过程分为两个阶段,即热解低碳化合物析出段和无机物高温受热分解段。升温速率相同时,YN₂油砂比YN1油砂挥发分析出的温度低。油砂热解产物是由脂肪烃、芳香烃、含氧官能团和羟基等组成的混合物,利用傅里叶红外光谱仪探究印尼油砂在不同升温速率下气体产物H₂O、CO₂、CO、CH₄、C_nH_m等的析出特性,气态烃类、含氧有机物等有机气体是由羰基和羧基以及甲氧基、亚甲基、甲基在热解低温段受热分解产生的,根据质谱图,确定了各个时刻逸出气体的种类和产量。利用AKTS软件基于F-W-O和Kissinger模型计算了油砂脱挥发分的热解动力学参数,计算结果表明,在相同的转化率下,不同升温速率的活化能呈线性分布,YN1的活化能高于YN₂的活化能。     

府谷煤CO2催化气化反应性的研究

加入适宜的催化剂可以提高气化反应速率,降低起始气化温度。为了研究不同阴离子（SO₄^2-、CO₃^2-、Cl^-）盐对府谷煤热失重过程的影响,利用热重分析仪对负载了8种催化剂（K₂CO₃、K₂SO₄、KCl;Na₂CO₃、Na₂SO₄、NaCl;FeSO₄、FeCl₂）的煤样进行了CO₂气化实验,其中每克府谷煤的K⁺、Na⁺、Fe²⁺负载量分别为0.001mol。同时采用升温动力学模型进行了数据拟合。实验结果表明：催化剂对煤与CO₂的低温热解并无明显的催化作用,而在高温气化阶段催化效果显著。对于钾盐和钠盐催化剂,当阳离子相同时,其催化活性顺序为：CO₃^2->SO₄^2->Cl^-。对于铁盐催化剂,FeSO₄的催化活性优于FeCl₂。动力学结果发现：负载催化剂煤样的活化能大小符合上述实验规律,分布在169～232.6kJ/mol之间,相比原煤（267.9kJ/mol）都有一定程度的降低。     

Precipitation study of CO2-loaded glycinate solution with the introduction of ethanol as an antisolvent

Focused beam reflectance measurement (FBRM) and ¹³C nuclear magnetic resonance (¹³C NMR) analysis were used to study the precipitation process of CO₂-loaded potassium glycinate (KGLY) solutions at different CO₂ loadings, during the addition of ethanol as an antisolvent at a rate of 10 mL·min⁻¹. The volume ratio of ethanol added to the KGLY solution (3.0 mol·L⁻¹, 340 mL) ranged from 0 to 3.0. Three solid-liquid-liquid phases were formed during the precipitation process. The FBRM results showed that the number of particles formed increased with CO₂ loading and ethanol addition for CO₂-unsaturated KGLY solutions, whilst for CO₂-saturated KGLY solution it first increased then decreased to a stable value with ethanol addition. ¹³C NMR spectroscopic analysis showed that the crystals precipitated from the CO₂-unsaturated KGLY solutions consisted of glycine only, and the quantity crystallised increased with CO₂ loading and ethanol addition. However, a complex mixture containing glycine, carbamate and potassium bicarbonate was precipitated from CO₂-saturated KGLY solution with the maximum precipitation percentages of 94.3%, 31.4% and 89.6%, respectively, at the ethanol volume fractions of 1.6, 2.5 and 2.3.     

Spectroscopic analysis of carbon dioxide and nitrogen mixed gas hydrates in silica gel for CO2 separation

In this study solid-state NMR spectroscopy was used to identify structure and guest distribution of the mixed N₂ + CO₂ hydrates. These results show that it is possible to recover CO₂ from flue gas by forming a mixed hydrate that removes CO₂ preferentially from CO₂/N₂ gas mixture. Hydrate phase equilibria for the ternary CO₂–N₂–water system in silica gel pores were measured, which show that the three-phase H–L_w–V equilibrium curves were shifted to higher pressures at a specific temperature when the concentration of CO₂ in the vapor phase decreased. ¹³C cross-polarization (CP) NMR spectra of the mixed hydrates at gas compositions of more than 10 mol% CO₂ with the balance N₂ identified that the crystal structure of mixed hydrates as structure I, and that the CO₂ molecules occupy mainly the abundant 5¹²6² cages. This makes it possible to achieve concentrations of more than 96 mol% CO₂ gas in the product after three cycles of hydrate formation and dissociation.     

高硫煤泥燃烧过程中的汞排放特性

通过固定床程序升温汞脱附试验系统对所选高硫煤泥中汞排放特性进行在线监测,并利用热重分析仪对煤泥热解和燃烧特性进行研究,结合试验所得热解和燃烧特性参数,采用分布活化能模型,进行动力学分析。结果表明：煤泥的热解和燃烧过程可分为3个阶段,非等温条件下,随着升温速率增加,热解过程在高温区发生,最大失重率提升,对应峰值温度偏移,产生热滞后,利于挥发分析出;在煤泥热解过程中少量氧气的参与,抑制挥发分的析出,在7% O₂条件下综合热解特性参数值D最大。热解性能随CO₂浓度升高而得到改善;煤泥燃烧性能随升温速率的增加而得到加强,其活化能随转化率变化呈现“U”型趋势分布;煤泥中无机汞化合物主要为HgCl₂、α-HgS、HgSO₄以及硅铝酸盐类结合汞,总汞释放主要范围对应200~600℃;煤泥中汞释放量随O₂浓度增大,CO₂气氛条件下,随着CO₂浓度增加,总汞释放量逐渐增大。     

宁东红石湾煤大分子模型构建及量子化学计算

使用工业分析、元素分析、固体核磁（¹³C NMR）、X射线光电子能谱（XPS）、傅里叶变换红外光谱（FT-IR）对宁东红石湾（HSW）煤样进行表征,获得煤样中元素赋存的种类、价态、化学键环境等物质微观结构的关键参数。结果表明HSW煤结构以芳香族为主,占75.96%,桥接芳碳与周碳比为0.315,可知其结构中以萘为主,苯和蒽为辅。氧原子主要以醚氧基（C-O）、羰基（C=O）和羧基（-COO）的形式存在,其中C-O占53.57%。氮原子以吡啶和吡咯的形式存在。苯环的连接方式以三、四取代为主,分别占47.77%、32.97%,脂肪族中环烷烃或脂肪烃-CH₃占优势。确定HSW煤的分子式为C₂₂₁H₁₄₈O₂₈N₂,分子量为3142.32。在此基础上结合计算机辅助实现了二维和三维大分子模型构筑。应用量子化学计算对HSW煤大分子模型进行了优化及核磁共振、红外光谱模拟,验证了所建模型的合理性。最终实现了HSW煤的微观分子结构的实验与量子化学描述。     

一种快速冷却超高温流体方法的数值模拟

在许多强吸热化学反应的化工过程中，常常需要对反应流体流出反应器时进行快速急冷来避免副反应或逆反应发生，以期最终获得可观的目标产物。在本实验室前期开展的热等离子体裂解二氧化碳实验研究中，采取在高温反应器出口加装收缩喷管将裂解气高速导入夹套水冷管的方法，实现了对高温裂解气的快速急冷，显著地避免了裂解气中CO与O的逆反应，获得了意想不到的CO₂高转化率。本文利用计算流体力学软件模拟这一过程，以期揭示这种新的冷却方法导致极快速冷却的机制。模拟结果表明，加装收缩喷嘴确实可以期待对高温射流产生10⁷ K·s^-1量级的温降速率。深入分析表明，仅仅靠气体动力学效应不能完全解释如此快速的冷却速率。从喷管高速喷出的黏性流体在夹套水冷管内形成高速涡流，这种涡流一方面增强了主流体对周围气体的卷吸，另一方面加强了被卷吸流体在被卷入之前与夹套水冷管壁面的强制换热过程，是导致快速急冷的主要机制。     

葡萄树枝烟气气氛下热解气化特性研究

以葡萄树枝为研究对象,采用热重-傅里叶变换红外光谱（TG-FTIR）联用技术,研究了反应气氛和升温速率对其热解特性的影响。结果表明：在烟气气氛（80% N₂、15% CO₂、5% O₂）下,DTG曲线在80、350和800℃温度附近存在3个明显失重峰,而在氮气气氛下仅存在80和350℃左右2个失重峰;升温速率为30℃/min时,氮气气氛下样品失重率达80%左右,而烟气气氛下达到95%。说明烟气气氛可提高葡萄树枝转化率,促进热解气化反应的进行。升温速率对生物质热解气化过程有双重影响,提高升温速率有利于葡萄树枝挥发分析出,促进热解气化反应进行,但容易引起葡萄树枝炭结焦,进而影响热失重的进程。热解析出产物采用FTIR分析,结果表明：不同热解阶段气体析出产物及析出量差别很大,且不同热解产物的析出特性由葡萄树枝样品内部官能团的重组、断裂引起。360℃时热解析出的气相产物种类最多,主要包括CO、CO₂、H₂O和CH₄等小分子气体,以及醛类、烃类、羧酸类等大分子物质。     

Strain-controlled graphdiyne membrane for CO2/CH4 separation: Firstprinciple and molecular dynamic simulation

Tensile strain of porous membrane materials can broaden their capacity in gas separation. In this work, using van der Waals corrected density functional theory(DFT) and molecular dynamics(MD) simulations, the performance and mechanism of CO_2/CH_4 separation through strain-oriented graphdiyne(GDY) monolayer were studied by applying lateral strain. It is demonstrated that the CO_2 permeance peaks at 1.29 × 10~6 gas permeation units(GPU) accompanied with CO_2/CH_4 selectivity of 5.27 × 10~3 under ultimate strain, both of which are far beyond the Robeson's limit. Furthermore, the GDY membrane exhibited a decreasing gas diffusion energy barrier and increasing permeance with the increase of applied tensile strain. CO_2 molecule tends to reoriented itself vertically to permeate the membrane. Finally, the CO_2 permeability decreases with the increase of the temperature from300 K to 500 K due to conserving of rotational freedom, suggesting an abnormal permeance of CO_2 in relation to temperature. Our theoretical results suggest that the stretchable GDY monolayer holds great promise to be an excellent candidate for CO_2/CH_4 separation, owing to its extremely high selectivity and permeability of CO_2.     

The pyrolysis of scrap automotive tyres: The influence of temperature and heating rate on product composition

Shredded automotive tyre waste was pyrolysed in a 200 cm³ static batch reactor in a N₂ atmosphere. The compositions and properties of the derived gases, pyrolytic oils and solid char were determined in relation to pyrolysis temperatures up to 720 °C and at heating rates between 5 and 80 °C min⁻¹. As the pyrolysis temperature was increased the percentage mass of solid char decreased, while gas and oil products increased until 600 °C after which there was a minimal change to product yield, the scrap tyres producing approximately 55% oil, 10% gas and 35% char. There was a small effect of heating rate on the product yield. The gases were identified as H₂, CO, CO₂, C₄H₆, CH₄ and C₂H₆, with lower concentrations of other hydrocarbon gases. Chemical class composition analysis by liquid chromatography showed that an increase in temperature produced a decrease in the proportion of aliphatic fractions and an increase in aromatic fractions for each heating rate. The molecular mass range of the oils, as determined by size exclusion chromatography, was up to 1600 mass units with a peak in the 300–400 range. There was an increase in molecular mass range as the pyrolysis temperature was increased. FT-i.r. analysis of the oils indicated the presence of alkanes, alkenes, ketones or aldehydes, aromatic, polyaromatic and substituted aromatic groups. Surface area determination of the solid chars showed a significant increase with increasing pyrolysis temperature and heating rate.     

Change of nitrogen functionality of N-enriched condensation products during pyrolysis

Changes in the nitrogen functionality of ¹⁵N-enriched condensation products prepared from glucose and ¹⁵N-glycine were investigated during pyrolysis at 600–1000 °C. The structural changes in the condensation products were studied by means of solid-state ¹³C and ¹⁵N NMR spectroscopies. During pyrolysis, the aliphatic moieties of the condensation products decomposed and evolved as gas and tar. At pyrolysis temperatures above 600 °C, almost all the carbon in the chars were converted to aromatic carbon. After pyrolysis, large amounts of nitrogen remained in the chars as char nitrogen (char-N), and about 30% of the nitrogen was eliminated from the chars as HCN and NH₃. With increasing temperature, the production of HCN and NH₃ increased and the amount of char-N decreased. By combining X-ray photoelectron spectroscopy and NMR results, detailed results for nitrogen fractions in chars were obtained. During pyrolysis, the fraction of unsubstituted pyrrole-N decreased and the fraction of quaternary-N increased. The fraction of pyridine-N remained almost constant at temperatures below 800 °C, but at 900 °C and above, the fraction of pyridine-N decreased. The fraction of substituted pyrrole-N showed minimum at 800 °C. On the basis of these results, structural changes of nitrogen functional groups during pyrolysis are discussed.