中变质煤热解的有机挥发分析出研究

选择5种有代表性的中变质煤,在实验室条件下进行热解,利用法国Setaram公司的TGA92热重分析仪和瑞士Balzers公司的四极滤质质谱仪QMS422联用组合进行TG-MS分析(热重质谱分析),针对有机挥发分析出的研究表明:1)烷基侧链的热解导致煤结构的解体,甲基的热解断裂温度高于亚甲基及次甲基,随煤变质程度的增大,它们析出的峰温增高;2)甲烷的析出有三种类型:一种是煤中甲基的热解脱落,形成甲基离子然后与氢反应形成甲烷,第二种是煤中吸附的甲烷析出,第三种是芳香体系聚合的稠环体系释放出甲烷;3)苯的析出也有三种类型,第一种类型为煤中芳香结构热解脱落亚甲基和次甲基等形成的苯离子进一步加氢的结果,第二种是煤中芳香结构热解脱落甲基形成苯离子,苯离子与氢反应生成苯,第三种是煤中缩聚反应的结果.     

基于分子动力学模拟的VOCs热氧化特性分析

采用反应分子动力学模拟的方法,选择苯、甲苯和苯乙烯作为代表性VOCs组分,分析其在不同温度下发生热解和氧化的反应特性,获得其总包动力学参数,并应用于VOCs在蓄热氧化装置(RTO)中的CFD模拟。芳烃类VOCs的初始热解步骤主要发生脱氢、脱侧链和开环反应,生成对应支链结构的小分子烃类和苯,而氧化过程则直接生成CO、H₂O以及少量的烃类。不同VOCs的热解与氧化反应速率存在显著差异,动力学分析表明,使用一级反应假设适用于描述VOCs热解及氧化初始阶段的反应过程。CFD模拟表明,提高入口温度可以显著提升VOCs的转化效率,而在同等VOCs处理量的前提下,提高VOCs浓度、降低进口总流量,对VOCs转化效率的改善程度与提高入口温度相当,这表明VOCs浓缩技术耦合RTO更为高效节能。     

煤在氢压和慢速加热下的固定床热解

作者研究了100克煤在10Mpa 压力和加热至900℃条件下的固定床加氢热解。在固定床中处理的贝林根煤(其挥发分为32.8%重),其脱挥发分速度近似于快速加氢热解的脱挥发分速度,然而,油收率较少,因为煤的慢速加热,初次挥发物在反应空间的停留时间长,产品气中主要是甲烷。油的组成取决于热解温度,油中苯的含量随温度提高而增加。在温度恒定的     

煤在铜渣熔融还原铁尾渣降温中的热解特性

通过动力学计算,结合XRD和气相色谱分析,对降温条件下单煤及以铜渣熔融还原尾渣为载体的煤的热解行为进行了研究. 结果表明,在初始温度1200℃、降温速率6.667 K/min条件下,煤混渣中煤热解最大速率较单煤增大,时间提前6~7.5 min,失重增加4.51%~11.43%;煤混渣热解气体中H2含量增高,原因为渣中CaO组分对煤中芳香环的脱氢效应;单煤及煤混渣样在降温过程中热解及气化反应均属一级反应,煤混渣样初始热解及气化反应表观活化能低于单煤,但主热解区表观活化能大于单煤,原因为主热解区还原性气氛增强,同步发生渣中高价铁氧化物的还原,反应类型增加,表观活化能变大.     

丙烯生成苯和甲苯反应机理的数值模拟

结合Material Studio软件和Aspen Plus软件计算结果,通过自由基与不饱和烃的加成反应生成大自由基,大自由基再经过环化、脱氢生成五元环,再经由生成苯或甲苯的路径生成相应产物。其中生成苯的路径为环戊二烯基和CH_3·加成、链传递、脱氢、成桥环、桥键断裂,最终脱氢生成苯;生成甲苯的路径为乙炔和环戊二烯基加成、分子内加成、分子内氢转移、桥键断裂,最终链终止反应生成甲苯。将得到的模拟数据分布与文献中的数据进行对比可知,两者吻合良好。     

由煤加氢产物制取轻芳烃

研究了由预加氢多环芳烃热裂化制取单环芳烃。描述了在700—900℃和常压下,于氮气流(作为惰性载气)中及在反应器内停留时间为0.5秒的条件下,热解1,2一二氢化萘,全氢化萘和全氢化茚所得的研究结果。萘烷(全氢化萘)裂化可得到很高产率的苯、甲笨、二甲苯(BTX)(达30%,以重量计)。乙烯的产率在20%以上,甲烷的产率为15—20%。可是,由萘仅部分加氢生成的1,2—二氢化萘或萘满,热解所得的苯和其他轻芳烃的产率都很低。主反应是萘的脱氢和重整。业已证明,萘完全加氢就可使它的两个环之一在750—850℃下发生断裂,并同时生成显著量的乙烯和轻芳烃。在全氢化茚和其他完全加氢多环芳香化合物的热解反应中也观察到相同的现象。因此,可以断定,完全加氢可使环的稳定性(这是多环芳烃的特征)消失。所得研究结果的工业兴趣在于:由煤加氢生成的全氢化多环芳香化合物可同时制取轻芳烃和乙烯。     

煤的快速热解所得焦油的化学结构

澳大利亚的一种褐煤和两种烟煤,经快速热解后,用~1H 核磁共振分光仪研究其焦油的结构和组成。煤在流化床中的反应时间约为1秒钟。当热解温度在650℃以下时,每种焦油的芳香氢含量随热解温度的增加而稍有增加;但在650～900℃时,则随热解温度而迅速增加。其芳香碳含量随热解温度直线增加。芳香碳收率在600—700℃达到最大值,然后降低;芳香氢收率则与温度无关。稠环结构的芳香族物质的比例随温度的增加而增加。认为有三种反应性的温度区:(1)在600℃以下,聚亚甲基链和芳香基团是稳定的。(2)在600～700℃之间,脂肪族取代物(除α基团外)均分解。(3)在700～900℃之间,α脂肪族基团和芳香族基团也分解,导致焦油收率减少。     

含有典型C—C煤炭模型化合物热解过程的自由基调控机理研究

煤本身是一种复杂的非均质混合物，含有大量的致密环状芳香烃。针对煤结构中各种C—C化学键，采用联苄、二苯甲烷、联苯作为煤C—C结构的模型化合物，分别在600℃,650℃,700℃,750℃下通过Py-GC/MS探究其热解产物分布情况；通过添加供氢溶剂(hydrogen donor solvent, HDS)捕获中间自由基验证其反应路径的存在；利用Gaussian09,Shermo,选取M06-2X泛函、def2-TZVP基组，加上D03(0)色散校正计算化学键解离焓(BDE)。通过实验与模拟相结合的方式印证自由基路径的存在。同时，用Py-GC/MS进行不同温度的模型化合物的热解实验。结果表明：模型化合物的热解均为自由基路径；由于C—C键类型不同，模型化合物的热解程度不同。各个键按能垒由大到小排序依次为C_ar—C_ar,C_ar—C_al,C_al—C_al,因此，热解程度由大到小的化合物依次为联苄、二苯甲烷、联苯。供氢溶剂可能会降低断键能垒；模型化合物热解中间自由基如...     

提高煤热解焦油中BTX产率的研究进展

总结了煤的催化热解和催化煤热解气来提高焦油中BTX产率的相关研究,简要分析了工艺条件(热解温度、热解气氛和压力、催化剂、煤的预处理等)对BTX产率的影响规律,并论述了BTX生成的反应途径:芳构化反应、重质组分裂解反应、含氧芳香化合物的脱氧反应。认为应深入探究煤催化热解过程中生成BTX的氢的来源,这将对充分利用煤热解过程中生成的H2、CH4等富氢气体与热解气中的重质组分耦合来提高BTX的产率提供重要的指导意义。     

提高煤热解焦油中BTX产率的研究进展

总结了煤的催化热解和催化煤热解气来提高焦油中BTX产率的相关研究,简要分析了工艺条件(热解温度、热解气氛和压力、催化剂、煤的预处理等)对BTX产率的影响规律,并论述了BTX生成的反应途径:芳构化反应、重质组分裂解反应、含氧芳香化合物的脱氧反应。认为应深入探究煤催化热解过程中生成BTX的氢的来源,这将对充分利用煤热解过程中生成的H2、CH4等富氢气体与热解气中的重质组分耦合来提高BTX的产率提供重要的指导意义。     

High temperature hydrogenolysis of bibenzyl

Bibenzyl was pyrolysed in the gas phase, in the presence of a large excess of hydrogen at 600–850 °C. Products formed were benzene, toluene, ethylbenzene and styrene; no stilbene or phenanthrene were formed. The yield of toluene decreased with increasing temperature, that of benzene increased, that of ethylbenzene dropped to zero and that of styrene slowly decreased. The decrease in toluene plus ethylbenzene yield was roughly equal to the increase in benzene yield. The apparent pseudo first order ‘activation energy’ for loss of bibenzyl under these conditions is 10.2 ± 0.8 kcal mol^?1. The nature of products formed, their variation with increasing temperature and the low activation energy can be interpreted in terms of a radical chain mechanism in which the chain carrier is the hydrogen atom.     

Hydrogen production by methane cracking over different coal chars

Hydrogen production by methane cracking over a bed of different coal chars has been studied using a fixed bed reactor system operating at atmospheric pressure and 1123 K. The chars were prepared by pyrolysing four parent coals of different ranks, namely, Jincheng anthracite, Binxian bituminous coal, Xiaolongtan lignite and Shengli lignite, in nitrogen in the same fixed bed reactor operating at different pyrolysis temperatures and times. Hydrogen was the only gas-phase product detected with a GC during methane cracking. Both methane conversion and hydrogen yield decreased with increasing time on stream and pyrolysis temperature. The lower the coal rank, the greater the catalytic effect of the char. While the Shengli lignite char achieved the highest methane conversion and hydrogen yield in methane cracking amongst all chars prepared at pyrolysis temperature of 1173 K for 30 min, a higher catalytic activity was observed for the Xiaolongtan lignite char prepared at 973 K, indicating the importance of the nature of char surfaces. The catalytic activity of the coal chars were reduced by the carbon deposition. The coal chars had legible faces and sharp apertures before being subjected to methane cracking. The surfaces and pores of coal chars were covered with carbon deposits produced by methane cracking as evident in the SEM images. The results of BET surfaces areas of the coal chars revealed that the presence of micropores in the chars was not an exclusive reason for the catalytic effect of the chars in methane cracking.     

Investigation on initial stage of rapid pyrolysis at high pressure using Taiheiyo coal in dense phase

Rapid pyrolysis of Taiheiyo coal was investigated with a laboratory-scale batch type reactor (BTR), which was specially developed to study various gasification processes at the conditions close to an industrial entrained bed gasifier. The experiments were carried out in helium at 1073 K, 7.1 MPa, varying reaction times from 1 to 80 s and coal/gas ratios in the range of 0.41-1.65 g/l. Extents of pyrolysis and profiles of product formation were discussed based on the results of char yield, gas and tar formation characteristics. It was observed that reaction of pyrolysis was significantly affected by coal/gas ratio. At high coal/gas ratios, pyrolysis was found to be retarded at initial stage. Pyrolysis products can be roughly divided into two groups. One is the ultimate products such as methane, carbon oxides, hydrogen, and benzene and the other is the intermediate products such as ethylene and toluene. Heat supply inside BTR was examined and the influence of thermal properties of atmospheric gases was investigated by carrying out pyrolysis in nitrogen and by comparing the results with that in helium. As a result, the heat capacity of atmospheric gas has less influence on pyrolysis process whereas heat conductivity of atmospheric gas as well as mixing conditions of gas and coal sample significantly affect the pyrolysis reaction.     

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。     

木材经催化热分解向BTX和合成燃料的转化

以废木材生物质的有效利用为目的,使用粉粒流化床反应器,对3种木材进行了催化热分解实验,以4种催化效果不同的粒子作为流化床内的流化介质来考察催化热分解过程中介质颗粒、反应气体和热分解温度对产物分布的影响.木材的挥发性物质在700K时就已几乎分解出来,挥发性物质中的轻质芳香烃碳氢化合物（苯、甲苯、二甲苯和萘：BTXN）的收率随着热分解温度的升高而增加,1173K下达到3.1%（质量分数）,daf.在氢气气氛下,当作为流化介质颗粒Zn(3%,质量分数)/HZSM-5催化剂对木材进行催化热分解时,853K下可得到6.1%, daf的轻质芳香烃碳氢化合物的收率(BTX 5.5%,daf、萘0.6%,daf).而在活性很高的NiMo-A加氢催化剂下,在863K时,催化热分解产物几乎全为甲烷.     

Noncatalytic and catalytic pyrolysis of toluene

Noncatalytic and catalytic pyrolysis of toluene has been studied at atmospheric pressure in the temperature range of 1043 to 1153 K using steam or nitrogen as the diluent. The catalyst used was potassium carbonate impregnated calcium aluminate. Compared to noncatalytic pyrolysis, the conversions were significantly higher in the presence of the catalyst although the product selectivities were not affected. With nitrogen as the diluent the main products were hydrogen, methane, benzene, bibenzyl and higher hydrocarbons. When steam was used as the diluent, in addition to the above products appreciable amounts of carbon monoxide and carbon dioxide were also produced. The overall reaction of toluene could be represented by two parallel paths; one for toluene decomposition and the other for the toluene-steam reaction. The kinetic constants of these two reactions for catalytic as well as noncatalytic pyrolysis were determined by nonlinear optimization. In the presence of the catalyst, the activation energy for toluene decompostion was significantly reduced, whereas there was only a marginal reduction in the activation energy of the toluene-steam reaction.     

Hydrogenolysis and hydrocracking of the carbonoxygen bond. 3. Thermolysis in tetralin of substituted anisoles

Mild pyrolysis and hydrogenolysis products of coal contain substantial amounts of pyrocatechol and resorcinol and their homologues whereas hydroquinone and its homologues are absent or present in only low amounts. In the present work the model compounds anisole and methyl-, methoxy- or hydroxy-substituted anisoles were studied to elucidate substituent effects on the carbon—oxygen bond cleavage in the presence of tetralin. The experiments were carried out at 618 K and 6 MPa (H₂). The major reaction is demethylation to the corresponding phenols. A steric effect can be seen in the ortho compounds and an electronic effect when the substituent is a strongly electron-releasing group. In compounds with oxygen substituents para to each other little or no hydroquinone can be isolated whereas the ortho and meta compounds, respectively, give pyrocatechol and resorcinol. It is suggested that the low yield or absence of hydroquinone in this work and in coal pyrolysis is due to the high reactivity of the intermediate p-hydroxyphenoxy radical, which gives rise to adducts and other compounds of high molar mass. The ortho radical is sterically hindered and the meta radical has a lower reactivity and are hence abstracting hydrogen from the hydrogen donor or coal.     

Role of the influence of potassium during pyrolysis of medium volatile coal

The pyrolysis activities of a medium volatile coal, occurring in two temperature regions with maximum activities at 775 and 975 K, are influenced by potassium carbonate. Whereas in the low temperature region oxygen and total pyrolysis losses are hardly influenced by potassium addition, at higher temperatures a decrease of the pyrolysis losses, probably by oxygen retention due to potassium catalysis, is observed. Above 1000 K, evaporation of potassium can be observed.     

Kinetics of the reaction of hydrogen with thin films of carbon

The kinetics of the reaction of hydrogen with thin films of carbon has been studied over the temperature range 870–1150K and at pressures of hydrogen from 50–300 Torr (6.7–40 KPa). Thin films of carbon of average thickness about 30 nm were deposited on the surface of a quartz reactor by the pyrolysis of methane at 1100 K and the kinetics were studied in a static system. The products of the reaction were methane, ethane and ethylene, formed in successive hydrogenation steps, which in the low temperature region occurred largely on the surface of the carbon. In this region the activation energy of the rate of formation of methane was 6.5 kcal/mole. At temperatures above about 1050 K the thermal dissociation of hydrogen provided a source of radicals which caused a rapid increase in the rate of hydrogenation, both heterogeneous and homogeneous, giving an activation energy for the rate of formation of methane of 51 kcal/mole. A self-inhibition was observed, probably caused by a heterogeneous polymerization reaction leading to the formation of higher molecular weight products which remained adsorbed on the surface.     

The mechanism of the formation of soot and other pollutants during the co-firing of coal and pine wood in a fixed bed combustor

The co-firing of coal and biomass reduces the emission of pollutants by a mechanism which has been extensively studied but is still uncertain. Emissions were collected during the combustion in a fixed-bed furnace of Polish bituminous coal and pine wood, both individually and together, and it was observed that biomass produced less soot and burned at a lower temperature. Complementary analytical-scale combustion and pyrolysis experiments were carried out. The results of the analysis of emissions and reaction products, mainly by gas chromatography–mass spectrometry (GC–MS), but for large molecules by size exclusion chromatography (SEC), were interpreted so as to construct a reaction scheme for pollutant formation during co-firing. Evidence for three main routes to pollutant formation during co-combustion was adduced. Firstly, the presence of high MW material (from SEC) indicates escape of devolatilisation products round the outside of the flame. Secondly, the emission factors (ef) of PAH, alkyl-PAH, oxygen-containing PAH (O-PAC) and phenols are consistent with partial pyrolysis, while the high concentrations of the two-ring (naphthalenes and indene) PAH precursors evidently arise through radical reactions involving cyclopentadiene intermediates from phenols generated by pyrolysis of both coal and of biomass lignin. Thirdly, the concentrations of larger PAH are consistent with contributions from a hydrogen abstraction carbon addition (HACA) mechanism in which acetylene or butadiene formed in the flame are added to smaller PAH radicals. A kinetic model was applied to coal, biomass and coal/biomass co-combustion and highlighted the role of HACA in soot production during biomass combustion, but this route to soot was insufficient to model the higher yields of soot observed during coal combustion. In this latter case radical reactions involving either cyclopentadiene or condensation reactions of smaller PAH molecules initially formed in the pyrolysis stage to give ‘aromers’ are more important.