麦秸催化热解的TG-FTIR分析

在升温速率为20℃/min,催化剂为纯CaO和煅烧后的白云石（CaO/MgO）,氮气气氛下进行麦秸的热解和催化热解试验。由TG曲线可见麦秸催化热解可以提高其最大失重率,由DTG曲线可见催化热解有两个挥发分析出峰,通过比较说明添加催化剂有利于热解反应的进行,并且CaO/MgO催化效果更明显;对挥发分最大吸光率和第二大吸光率的红外谱图进行分析,再次证明了催化剂的效果;对挥发分大量析出阶段的主要气体CO2、CO、CH4、SO2的表观生成过程进行了研究分析;通过热解反应动力学的计算,采用Ozawa-Doyle法进行数据处理,表明添加催化剂后麦秸的热解活化能降低,有利于热解反应的进行。     

基于TG-FTIR的大豆油热解特性研究

利用热重-红外分析仪(TG-FTIR)研究了大豆油热解特性。通过大豆油热解产物的在线分析,验证了大豆油的热解机理,大豆油热解主要分为两个阶段:甘油三酯裂解阶段和由第1阶段生成的脂肪酸的裂解阶段。加入两种常用的油脂裂解催化剂碱性氧化物CaO和介孔分子筛MCM-41以考察油脂的催化裂解特性,两种催化剂对大豆油热解反应影响显著,使其热解终止温度升高,主要热解区间扩大,最大热解速率降低;由产物红外光谱图分析可知,CaO有较好的脱氧效果,MCM-41可以抑制酚类物质的生成。利用Coats-Redfern积分法计算大豆油主要热解区间的动力学参数,结果表明,在MCM-41催化下反应活化能降低,而CaO催化过程具有两个失重阶段,第1阶段活化能升高,第2阶段活化能降低。     

基于TG-FTIR联用的污水污泥热解实验研究

采用TG-FTIR联用技术研究了污水污泥热解,结果表明.污泥热解分为3个阶段,污泥热解的主要产物有脂肪烃、芳香烃及其化合物、酯类、羧酸、含氮化合物、酚、醇、醛、酮、水、CO2、CH4、CO和NH3,这些热解产物随热解温度的改变呈规律性变化.     

纤维素催化热解定向调控制取不含氧烃类液体燃料

为了将生物质能高效转化为高品位不含氧的液体燃料,以纤维素为例,研究了以催化热解方式将热解产物转化为芳香烃类液体燃料的过程.实验发现,纤维素热解产生的含氧有机小分子,可以通过催化热解的形式高效转化为不含氧的芳香烃类液体.催化剂采用HZSM-5(23)、催化剂原料质量比例为5∶1、热解温度为650℃、升温速率为10000 K/s的工况为纤维素催化热解的最佳工况,单环芳烃、多环芳烃产率分别为9.90%和12.91%,总芳香烃类产率为22.81%.热解温度提升至650℃前,更高的热解温度能获得更高的芳香烃产率.继续提高热解温度,单环芳烃、多环芳烃分子间还可能进一步发生聚合反应,最终产生积碳.同时本文也提出了一种可行的纤维素催化热解中的反应途径,与本文实验结果较为匹配.     

生物质催化热解的TG-FTIR研究

借助综合热分析仪和傅立叶红外联用技术(TG-FTIR),考察了HUSY、REY和HZSM-53种分子筛以及重油催化裂化催化剂MLC和馏分油催化裂解催化剂CIP对生物质催化热解的活性和选择性。研究结果表明,分子筛对生物质热解产物的脱氧活性顺序为:REY≈HUSY>HZSM-5,生成高辛烷值烃类的选择性顺序为:REY>HUSY≈HZSM-5;MLC催化剂和CIP催化剂都表现出较高的选择活性,前者的脱氧活性略高于后者;择形分子筛HZSM-5的引入对调整催化剂酸强度、提高催化转化选择性和抑制焦炭生成产生一定作用。     

有氧烘焙预处理对纤维素热解特性的影响

在有氧和无氧氛围下对纤维素进行了烘焙预处理,研究了氧气浓度(0％～15％)对纤维素理化性质和热解特性的影响.结果 表明:随着烘焙氧气浓度升高,纤维素碳元素和固定碳含量以及热值逐渐增加,而氧元素和挥发分大幅减少.有氧烘焙促进纤维素脱羟基、脱羰基和脱羧基等反应,导致含氧官能团减少和结晶度逐渐降低.有氧烘焙降低了纤维素热解初...     

松塔热解特性及热解过程气体产物分析

文章以废弃松塔为原料,采用热重分析的方法,研究了松塔热解失重规律,通过管式炉热解实验,研究了松塔热解过程中气体产物的变化规律.研究结果表明:松塔热解分为3个阶段,200～500℃是松塔热解的主反应区间,最大失重峰出现在338℃,热解反应过程存在两个较明显的DTG曲线肩峰,且这两个DTG曲线肩峰均与松塔抽提物有关;松塔热...     

纤维素和木质素含量对稻草、锯末热解及燃烧特性的影响

利用热重分析仪分析了生物质中纤维素和木质素含量对稻草、锯末热解及燃烧特性的影响。在热解过程中,生物质中纤维素含量较高的锯末,与纤维素含量较低的稻草相比,燃料失重要大。在燃烧过程中,通过实际生物质与纤维素和木质素混合物的对比,发现稻草和锯末的燃烧分为挥发分的脱除和焦的燃烧两个阶段,且燃烧特性与焦的形貌密切相关。     

钾盐对纤维素热解特性的影响

利用微型热解系统,研究500℃终温条件下,钾盐(K2SO4,KNO3,K2HPO4,KOH)对纤维素热解特性的影响。收集炭、焦、重油、轻油、气5种产物,计算各产物产率,分析结果表明,钾盐添加作用下,钾对热解存在主要影响,盐本身理化特性存在次要影响。利用气质联用仪(GC-MS)对重油和轻油进行分析,发现糖、苯类物质主要集中于重油,而醛、酮类物质主要集中于轻油,钾盐显著降低了糖类产物产率,增加了酮类、环烷烃类物质产率。利用X射线光电子能谱仪(XPS)对浸渍样、热解炭、焦含碳官能团进行分析,结果表明,热解后,热解炭与热解焦具有类似的含碳官能团分布,但热解炭中以芳香环中的C=C官能团为主,含氧官能团主要为羰基-CO-而热解焦中另外含有-COO-官能团。     

木质纤维素类生物质热解转化研究进展

综述了木质纤维素类生物质热解技术的研究进展,总结了不同生物质原料的热解机理,分析了产物的组成和性质,研究了产物的调控、改性和应用。指出未来的研究方向应该集中在以下几方面：技术改进,致力于改进生物质热解技术,提高能源转化效率和产物选择性;产品多样化,除了生物质热解产生的主要能源产品,如生物炭、生物油和生物气,还应着眼于开发高价值的化学品和材料,包括生物基化学品、特殊化学品和高性能材料;集成系统,应尝试将生物质热解与其他能源转化技术相结合,形成多能源联供系统,与生物质发酵、光催化、电解和储能等技术集成,以提高整体能源系统的效率和可持续性。     

基于TG-FTIR木耳基废弃物热解特性研究

利用热重-傅立叶红外光谱(TG-FTIR)联用技术对木耳基废弃物的热解特性进行了研究,并采用Coats-Redrern模型计算了木耳基废弃物的热解动力学参数。研究表明,木耳基废弃物的热解主要发生在200⁵00℃,活化能为50 kJ/mol左右,并随着升温速率的升高而增加。热解气态产物主要有CH4,H2O,CO2,CO等,同时还检测到含有C=O官能团的有机混合物,其中可能含有具有高附加值的化学品左旋葡萄糖酮(LGO)。热解气态产物和有机混合物的析出是引起木耳基废弃物失重的主要原因。     

Numerical simulation of cellulose pyrolysis

A mathematical model of transport phenomena and chemical processes of the thermal degradation of cellulose is presented. The kinetic model developed by Bradbury et al. (J. Appl. Polym. Sci. 23, 3271, 1979) for primary pyrolysis is extended to include secondary reactions of volatiles:

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From the physical point of view, the model describes convective, conductive and radiative heat transfer, mass convection and diffusion and velocity and pressure variations interior to the porous solid (Darcy law). Furthermore, porosity, mass diffusivity, permeability and thermal conductivity vary with the composition of the reacting medium. Time and space evolution of the main variables, and reaction product distribution, are simulated by varying the reactor temperature and the reactor heating rate.     

纤维素热裂解试验研究及分析

利用自行设计的固定床热裂解试验系统,在不同压力条件下,研究了纤维素的热解行为,在常压下分别考察热解温度、N2流量对热解产物的影响。研究结果表明,热解温度为450℃时,可得到较高收率的液体产物,并且液体产物的收率随着N2流量的增加而降低。当压力降低时,在450℃热解温度下液体产物的收率最高,为58.6%,比常压热解提高12.3%,生物油中水分含量随着热解温度的升高而升高。试验对在不同真空度下热解得到的液体产物进行了元素分析。     

TG-FTIR and Py-GC/MS study of the pyrolysis mechanism and composition of volatiles from flash pyrolysis of PVC

To facilitate the reuse and recycling of polyvinyl chloride (PVC) to achieve sustainable development and new industrialization, the composition and mechanism of formation of volatiles during the flash pyrolysis of PVC were studied by thermogravimetry-Fourier transform infrared (TG-FTIR) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). TG and derivative thermogravimetry (DTG) analyses indicated two main degradation stages during flash pyrolysis of PVC, namely dehydrochlorination of PVC and decomposition of dechlorinated-PVC. Simultaneously, the FTIR results revealed that the main functional groups in the pyrolysis process were H–Cl, -C-Cl, C–H, CH, and aromatic groups. The relative content of main volatiles was determined by Py-GC/MS, and decreased in the following order: aromatics > alkenes > hydrogen chloride (HCl) > chlorinated hydrocarbons. Specifically, the relative content of aromatics was as high as 76.790–81.809%, while that of HCl was in the range of 3.016–3.096%. The carbon number distribution and the relative content of main products obtained from the flash pyrolysis of PVC at different final temperatures were also analysed. According to the experimental results, the mechanism of formation of the main volatiles based on free-radical reactions was deduced in detail. Therefore, this study provides further details for deepening the understanding of the PVC pyrolysis process.     

纤维素微波热解基础研究

为了改善生物质热解油品质,有必要开展微波选择性热解的基础研究。以微晶纤维素为模型,研究微波热解温度、微波吸收剂(催化剂)等条件对产物分布组成规律的影响,确定了呋喃类和糖类是裂解的主要产物。通过分析几种主要产物的变化行为和转化途径,认为微波特有的"体加热"机制促进了3,6-脱水吡喃糖开环路径、左旋葡萄糖二次脱水以及通过C2和C5的缩合形成呋喃结构葡萄糖苷。在此基础上,探讨了纤维素微波热裂解机理模式。     

Mechanism study on cellulose pyrolysis using thermogravimetric analysis coupled with infrared spectroscopy

Based on the investigation of the polysaccharide structure of cellulose by using Fourier transform spectrum analysis, the pyrolysis behaviour of cellulose was studied at a heating rate of 20 K/min by thermogravimetric (TG) analysis coupled with Fourier transform infrared (FTIR) spectroscopy. Experimental results show that the decomposition of cellulose mainly occurs at the temperature range of 550–670 K. The weight loss becomes quite slow when the temperature increases further up to 680 K and the amount of residue reaches a mass percent of 14.7%. The FTIR analysis shows that free water is released first during cellulose pyrolysis, followed by depolymerization and dehydration. Glucosidic bond and carbon-carbon bond break into a series of hydrocarbons, alcohols, aldehydes, acids, etc. Subsequently these large-molecule compounds decompose further into gases, such as methane and carbon monoxide. __________ Translated from Journal of Zhejiang University (Engineering Science), 2006, 40(7): 1 154–1 158 [译自: 浙江大学学报 (工学版)]     

Impacts of co-feeding alcohols on pyrolysis of cellulose

Reactive atmosphere significantly affects pyrolysis of biomass, as the gases such as NH₃ involves in the reaction network in pyrolysis. In this study, instead of feeding reactive gas, the impacts of co-feeding ethanol or glycol on the pyrolysis of cellulose were investigated at varied pyrolysis temperatures (400 and 600 °C). The results showed that the co-feeding of the alcohols affected yields of bio-char and tar, evolution of light organics and heavy organics, elemental composition, formation of fused ring structures, crystallinity, thermal stability, distribution of functionalities in the bio-char. The co-feeding of both glycol and ethanol enhanced the formation of the heavy components with the π-conjugated ring structures and affected the production of the light organics such as furfural and glycolaldehyde. Glycol or its derivatives cross-polymerized with the organics in bio-char, increasing bio-char yield and made the bio-char more oxygen-rich. Ethanol, however, showed the converse effects. Co-feeding of the alcohols promoted crystallinity but showed distinct effects on thermal stability of the bio-char at the varied pyrolysis temperatures. Both pyrolysis temperature and structures of the alcohols determined their extents of involvement in the pyrolysis of cellulose.     

The kinetics of vapour-phase cellulose fast pyrolysis reactions

Biomass fast pyrolysis reactions consist of primary activation and fragmentation reactions, followed by secondary vapour-phase cracking reactions. Kinetic data derived from in-house experiments and published literature have clearly indicated that under true fast pyrolysis conditions, the primary reaction rates exceed those of the secondary reactions by several orders of magnitude. Therefore, since the cracking reactions are rate-limiting, an estimation of the rate of conversion of biomass to secondary products is in fact an estimation of the secondary reaction rate. This paper focuses on the determination of the key kinetic parameters (rate constants, pre-exponential constant and activation energy) for the vapour-phase cracking reactions which occur during cellulose pyrolysis. The parameters were determined using a first-order kinetic model and a non-linear regression routine. The experimental work was conducted in the Ultrapyrolysis equipment at the University of Western Ontario in London, Canada.     

木质纤维热解的热重和反应动力学研究

试验研究了木质纤维素的热解特性,并对其热解过程进行了分析.结果表明,纤维素在不同升温速率下的热解分为3个阶段:水分的析出、挥发分的析出以及固定炭的生成.纤维素热解是一级反应过程,根据积分法中的Coats和Redfern法对试验数据处理可得到反应的动力学参数(活化能E,频率因子A).