木质素结构及热解特性

为研究结构类型和提取方法对木质素热解特性的影响,本研究采用Klason方法预处理得到的棉杆、核桃壳Klason木质素和贝克曼方法预处理得到的核桃壳磨木木质素(MWL),并结合傅里叶红外光谱仪(FT-IR)和快速热解仪-气相色谱/质谱联用(Py-GC/MS)对其化学结构和热解特性进行分析。FT-IR表明碱木质素为G型木质素,棉杆木质素属于GS类型木质素,而核桃壳木质素具有HGS木质素的特征;Py-GC/MS分析发现原料的变化以及提取方法对木质素热解产物的组成有明显的影响,在棉杆Klason木质素中邻苯二酚类产物含量为28.18%,而在核桃壳Klason和磨木木质素的含量分别为18.12%和35.11%。同时研究表明经两种方法处理的木质素结构有明显的不同,其中Klason木质素结构中苯丙酸侧链上的α-和β-醚键明显断裂,而贝克曼处理主要体现在苯基芳基醚键的断裂。     

杏壳木质素的结构表征及其热解特性研究

为研究杏壳木质素的结构、热解特性及其产物的生成规律,通过硫酸脱除法从杏壳中分离出杏壳木质素,并通过红外光谱(FT-IR)和核磁共振(NMR)对其结构组成进行表征,利用热重及热重-红外联用分析研究其热解产物生成特性。研究结果表明：硫酸脱除法得到的杏壳木质素得率为30.42%,红外光谱图显示有较强的紫丁香基峰,还有一定量的愈创木基,二维核磁共振图谱表明杏壳木质素中有紫丁香基(S)、愈创木基(G)和对羟基苯基(H)3种木质素结构单元,属于SGH型木质素。热重及热重-红外联用分析表明杏壳木质素热解过程主要分为3个阶段,主要热解阶段发生在150~650 ℃之间的较宽温度范围内,360 ℃时热失重速率最大,热解产物主要为H₂O、CO、CO₂、CH₄以及醇、醛、酚、酸等。杏壳木质素中苯丙烷侧链上醚键和苯环间醚键断裂及挥发分二次裂解使CO的析出温度范围较宽,在200~700 ℃之间;羧基和羰基等官能团不稳定易断裂和重整,使CO₂的析出温度范围较窄,在250~650 ℃之间;苯丙烷侧链的断裂和苯环上甲氧基官能团的去甲基化反应,以及芳香环的深度断裂,使CH₄的析出在400和600 ℃时呈现2个峰值。     

基于TG/FT-IR, Py-GC/MS的聚乳酸塑料热降解研究

采用TG/FT-IR、Py-GC/MS联用技术研究了可降解塑料聚乳酸的气体释放过程及其热解产物.研究表明,聚乳酸在320～370℃区间发生剧烈热解反应,DTG曲线在359℃时出现最大值.热解气体的逸出情况由FT-IR进行实时检测,并且定性分析了CH_4, CO_2, CO 和有机物等产物的析出情况.通过比较TG/DTG曲线和FT-IR数据,发现DTG和FT-IR分析结果较为一致.Py-GC/MS联用技术用来分析聚乳酸热解产物,结果表明醛、酮、酯及低聚物是主要降解产物.Py-GC/MS方法快速、简便、准确,不失为聚合物热解研究的良好方法.     

棉杆有机溶剂型木质素的结构表征与分析

采用乙醇和1,4-丁二醇萃取的方法分别从棉杆中分离并提纯木质素。采用红外光谱、紫外光谱、核磁氢谱对两种方法所提取木质素分别进行结构表征。结果表明:两种方法提取的木质素的各种官能团包括羟基和甲氧基峰都很明显,且均具有明显的紫丁香基苯环和愈创木基苯环的特征结构,其中1,4-丁二醇提取的木质素中的紫丁香基和愈创木基的含量较多。     

Py-GC/MS在聚氨酯弹性体组成分析中的应用

应用裂解-气相色谱/质谱(Py-GC/MS)联用技术分析了聚氨酯弹性体的结构组成。研究发现,在约550℃的裂解温度下,聚氨酯弹性体中异氰酸酯、二元醇扩链剂等裂解成其单体,低聚物醚酯键断链生成其单体、多聚体,或C—C和C—O键断裂生成醚、醇特征碎片。该方法适用于分析醚型、酯型、醚酯型聚氨酯的组成,方法便捷、准确有效。     

温度对木聚糖快速热解产物的影响

以半纤维素的主要成分木聚糖为原料,利用Py-GC/MS(快速热解-气相色谱/质谱)联用仪进行了快速热解及产物在线检测分析实验,考察了温度对木聚糖热解产物的影响。实验结果表明,木聚糖快速热解生成的可挥发性热解产物随温度的升高逐渐增加,并在700℃下达到最大,此后随温度升高开始降低。乙酸、羟基丁酮主要在低温热解时形成;而丙酮、环戊酮类产物在高温下收率较高;羟基乙醛、羟基丙酮和糠醛等产物则不随温度发生明显的变化。在此基础上,根据主要产物的形成规律,探讨了木聚糖主要热解产物可能的形成机理。     

W_2C/AC催化快速热解松木磨木木质素

以活性炭(AC)为载体制备了不同钨负载量的W_2C/AC催化剂,将其和松木磨木木质素(MWL)机械混合后进行Py-GC/MS(快速热解-气相色谱/质谱联用)实验,考察了钨负载量、催化剂/MWL比例对产物分布的影响,并通过外标法对主要产物(芳烃类和酚类)的真实产率进行了定量分析。结果表明,W_2C/AC催化剂可有效促进木质素的热解解聚生成单酚类产物,并对酚类产物具有脱羰基、脱甲氧基、脱羟基以及加氢的效果,从而促进稳定的酚类产物(不含羰基、甲氧基和不饱和碳碳双键)和芳烃类产物的生成。在4种W2C/AC催化剂中,10%-W2C/AC的催化效果最佳,在催化剂/MWL比例为5时热解产物总产率达到最大值,此时芳烃类和酚类产物的总产率由无催化剂时的21.2 mg·g~(-1)和151.0 mg·g~(-1)增加至102.1 mg·g~(-1)和191.1 mg·g~(-1)。     

基于PY-GC/MS的生物质组分间相互作用的热解实验

为研究生物质三组分间热裂解过程中的相互作用,利用热裂解-气相色谱/质谱联用仪（PY-GC/MS）联用的方法,对纤维素、木聚糖（半纤维素的模化物）和木质素进行单独热裂解及两两组分混合热裂解实验。单组分实验结果表明,在热解温度600℃、热解时间10s条件下纤维素的热解产物主要以左旋葡聚糖为主,木聚糖以乙酸和糠醛为主,而木质素主要以酚类物质为主。组分混合热裂解实验结果表明,纤维素促进了木聚糖热裂解生成更多的乙酸和糠醛,而木聚糖和木质素对纤维素热解生成左旋葡聚糖具有强烈的抑制作用;纤维素和木聚糖的存在大大促进了木质素热裂解生成酚类物质,而木质素抑制了木聚糖热裂解生成乙酸和糠醛。此外,研究还发现混合组分热解的相互作用受到热解温度和停留时间的影响。     

W2C/AC催化快速热解松木磨木木质素

以活性炭（AC）为载体制备了不同钨负载量的W₂C/AC催化剂,将其和松木磨木木质素（MWL）机械混合后进行Py-GC/MS（快速热解-气相色谱/质谱联用）实验,考察了钨负载量、催化剂/MWL比例对产物分布的影响,并通过外标法对主要产物（芳烃类和酚类）的真实产率进行了定量分析。结果表明,W₂C/AC催化剂可有效促进木质素的热解解聚生成单酚类产物,并对酚类产物具有脱羰基、脱甲氧基、脱羟基以及加氢的效果,从而促进稳定的酚类产物（不含羰基、甲氧基和不饱和碳碳双键）和芳烃类产物的生成。在4种W₂C/AC催化剂中,10%-W₂C/AC的催化效果最佳,在催化剂/MWL比例为5时热解产物总产率达到最大值,此时芳烃类和酚类产物的总产率由无催化剂时的21.2 mg·g^-1和151.0 mg·g^-1增加至102.1 mg·g^-1和191.1 mg·g^-1。     

玉米秸秆木质素的超临界提取及结构表征

采用超临界CO2/乙醇-水三元体系反应提取玉米秸秆中的木质素,并采用沉淀法对提取液中的木质素进行回收,得到木质素产品.利用气相色谱-质谱联用、红外光谱、紫外光谱分析了提取液成分及提取木质素产品的结构特性.采用热重分析方法对提取木质素的热稳定性进行了研究.结果表明:本试验方法提取的玉米秸秆木质素具有木质素的典型结构.提取木质素主要在180 ～500℃温度范围内分解失重.原木质素在超临界提取反应过程中发生了相当程度的降解,醚键发生了较大程度的断裂,木质素-水化合物复合体发生了不完全降解,提取木质素中含有一定量的碳水化合物.     

蒜头果木质素提取及成分分析

采用一般碱法、超声波辅助和微波辅助从蒜头果壳和枝中提取木质素,分别测定了蒜头果壳和枝中木质素含量及木质素的提取率,并对所提取木质素进行红外和紫外光谱分析。克拉森木素定量法测得蒜头果壳和枝中木质素质量分数分别为44.41%±0.65%和34.57%±0.52%,在碱浓度0.5 mol/L、碱液量30 mL/g、超声波处理时间1 h、水浴温度40℃的提取工艺条件下,蒜头果壳和枝的木质素提取率分别为45.21%±0.59%和63.78%±0.73%。紫外和红外光谱显示超声波辅助方法提取的木质素保持了木质素原有结构,存在明显的愈疮木基和紫丁香基苯环结构;并通过黏度法比较了3种不同提取方法所得木质素的相对分子质量。     

裂解-气质联用分析氧漂过程中木素结构的变化

从针叶木硫酸盐原浆、氧漂浆以及氧漂后的废液中分离出残余木素,在四甲基氢氧化铵（TMAH）存在下,采用裂解气相色谱-质谱联用(Py-GC-MS)的方法研究了氧漂过程中木素分子结构的变化.对裂解产物的分析表明,木素裂解时产生多种甲基化的芳香化合物,以愈创木基型化合物为主;氧漂能够氧化和降解木素分子,产生更多的羧基化合物,氧化程度高的木素分子容易从纸浆中溶出,氧漂优先脱除沉积在纤维表面上的短侧链木素.     

Catalytic pyrolysis-GC/MS of lignin from several sources

Lignin from four different sources, extracted by various methods, were pyrolyzed at 650 °C using analytical pyrolysis methods (Py-GC/MS). Pyrolysis was carried out in the absence and presence of two heterogeneous catalysts, an acidic zeolite (HZSM-5) catalyst and a mixed metal oxide catalyst (CoO/MoO₃). Non-catalytic Py-GC/MS was used to identify the lignin as characterized by their H-, G- or S-lignin makeup and also served as the control basis to evaluate the effect of the said catalysts on the production of aromatic hydrocarbons from these lignin sources. Experiments show that the selectivity to particular aromatic hydrocarbons varies with the composition of the lignin for both catalysts. The major pathway for hydrocarbon production over HZSM-5 is likely increased depolymerization efficiency that releases and converts the aliphatic linkers of lignin to olefins followed by aromatization. Simple phenols produced from the deconstruction of the lignin polymer are likely to be a source of zeolite deactivation. The CoO/MoO₃ is likely to produce aromatic hydrocarbons through a direct deoxygenation of methoxyphenol units.     

Mathematical modelling of lignin pyrolysis

Seven lignins from different sources were pyrolysed (i) isothermally in vacuum over the temperature range 300–1300 °C and (ii) at a constant heating rate of 30 °C min^?1 and a pressure of 0.1 MPa over the temperature range 150–900 °C. The mass fraction of each product—char, tar and gas species—and the elemental composition of the char and the tar were determined for the flash pyrolysis experiments. The evolution rates of the gas species and the tar versus the dynamic temperature of pyrolysis were determined for the constant heating rate pyrolysis experiments. Although the amount of each product species varied from lignin to lignin, the evolution rates were insensitive to the lignin source and the extraction process. To model the data, modifications were made to a recently developed model of coal pyrolysis. The model proved to be successful in simulating both the data from vacuum flash pyrolysis and constant heating rate pyrolysis of Iotech lignin.     

Thermal decomposition characteristics of poly(ether imide) by TG/MS

Thermal degradation of poly(ether imide) (PEI) was studied by the combination of pyrolysis/gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetric analysis/mass spectrometry (TG/MS) techniques. The composition of evolved gases was determined by Py-GC/MS and the real-time formation curves were obtained through TG/MS. The thermal degradation mechanisms of PEI were resolved through TG/MS methods. The major pyrolysis mechanisms with the two-stage reaction regions were main chain random scission and carbonization. In the first stage pyrolysis, the decomposition of the hydrolyzed-imide, ether and isopropylene groups caused the evolution of CO₂ and phenol as major products accompanied by a chain transfer of carbonization to form partially carbonized solid residue. In the second stage pyrolysis, the decomposition of partially carbonized solid residue and the remaining imide group produced CO₂ as a major product along with benzene and small a amount of benzonitrile. Afterward, the chain transfer of carbonization dominated the decomposition of solid residue in higher temperatures to produce a high char yield. A kinetic model was proposed from the calculation of two flat regions in the activation energy curve. The theoretical pyrolysis curve from the proposed model was calculated and compared with the experimental curve, which were quite well matched.     

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。     

葵花杆的热解特性及热解产物分析

为充分利用生物质葵花杆,采用同步热分析仪以升温速率为影响因素对葵花杆的热解特性进行研究,利用Coats-Redfern积分法计算主要阶段热解动力学参数,并采用气相色谱/质谱联用仪对热解产物进行了定量分析.研究结果表明:葵花杆的热解过程可分为预热干燥、主要热解及炭化3个阶段;随着升温速率的增大,葵花杆热解的TG曲线向高温...     

基于Py-GC/MS的玉米秸秆快速热解实验研究

以玉米秸秆为原料,利用Py-GC/MS设备在不同热解条件下进行快速热解实验,并对热解气相产物进行在线检测分析,考察了热解时间、热解温度及ZSM-5催化剂对玉米秸秆热解特性及热解产物分布的影响.实验结果表明:热解温度越高,热解反应越充分,且热解温度为550℃时对应的热解产物品质最高,其中芳香族化合物最高达28.3％;随着...     

Mechanism and kinetic modelling of PEEK pyrolysis by TG/MS

A new technique combining Py-GC/MS with TG/MS can be used in analyzing the mechanism and kinetic modelling of pyrolysis. The results of this study show that a combined approach of Py-GC/MS and TG/MS exhibited dynamic curves of 13 evolved gases from the pyrolysis of PEEK from room temperature to 900°C. In this study we also discovered that there are two stable pyrolysis reaction regions during the pyrolysis in helium atmosphere at a heating rate of 10°C/min from room temperature to 900°C. In the first pyrolysis region the ether group and ketone group from the main chain of PEEK decomposed to phenol and CO₂, respectively. It also showed that the thermal stability of the ketone group was better than that of the ether group. Accompanied with the chain transfer in the first pyrolysis region, the fluorenone structure appeared in part of the carbonization scheme. Above 650°C it moved to the second reaction region. In this region the main decomposition products were CO₂ from the ketone group of fluorenone and from the carbonized structure described above. From the two flat regions of the activation energy curve of pyrolysis, we have proposed a kinetic model with two pyrolysis regions. Based on this model, we compared the theoretical pyrolysis curve with the experimental curve, the two curves being quite similar.     

废旧电路板热解特性的研究

热解是回收处理废旧电路板中金属及树脂成分的重要方法。文中采用热重差热联用分析仪和裂解气相色谱质谱联用仪检测了以酚醛树脂为基板的废旧电路板热解特性;分析了不同速率下的动力学参数,及其热解产物的化学成分。实验研究结果表明:废旧电路板热解过程主要有2个快速质量损失阶段(270—350℃,350—480℃),其平均活化能分别约为67,97 kJ/mol。其裂解产物主要是苯酚、对甲苯酚、邻异丙烯基苯酚、邻甲苯酚、对异丙基苯酚、糠醛等。