生物质气化过程中热解焦油的生成及其均相转化机理

以两段式下吸气化炉焦油的衍化规律为背景对焦油的生成规律、均相转化过程中芳烃环的形成及增长机制等进行了阐述和总结。阐述了纤维素、半纤维素、木质素的热解特性及主要热解产物的生成规律,并与稻秆在200～500℃热解实验中检测得到的焦油成分进行了对比分析,两者结果基本一致。主要从官能团衍化角度分析了不同种类初级焦油的均相转化机理,阐述了单环芳香烃生成、单环向多环芳香烃转化及多环芳烃进一步聚合转化过程中的脱氢环化、脱氢加乙炔、氢转移、异构化及苯酚转化等机制。基于已有转化机理,初步构建了焦油均相转化路径图。     

利用Py-GC/MS研究温度和时间对杨木粉催化热解制芳烃的影响

文章以ZSM-5分子筛为催化剂,采用Py-GC/MS反应装置研究不同反应条件(热解温度和热解时间)下杨木粉催化热解制备芳香烃类化合物的反应性能,并重点分析芳香烃化合物的组成及其产率随反应条件的变化。研究结果表明:ZSM-5分子筛催化剂能够显著提高芳香烃类化合物的产率;当热解时间固定为25 s,热解温度为400~800℃时,芳香烃类化合物均为主要产物,当热解温度为600℃时,芳香烃类化合物的产率最高,随着热解温度的继续升高,芳香烃类化合物的产率先降低后增加;当热解温度固定为600℃时,芳香烃类化合物的产率在热解时间为25 s时达到最大值,并随着热解时间的继续延长先降低后增加。     

Ga/ZSM-5催化酚醛树脂热解选择性制备单环芳烃的研究

开发一系列用于酚醛树脂快速热解的Ga改性ZSM-5催化剂,并进行全面的催化剂表征,包括X射线衍射（XRD）、氮气吸附脱附、氨气程序升温吸附（NH₃-TPD）和透射电子显微镜（TEM）等,以阐明催化剂的结构特性。Ga物种显著调节了ZSM-5分子筛酸性位点的分布和孔结构,有利于高温下促进热解脱氧反应的进行,同时优化了择形催化性能。重点讨论了Ga负载量、热解温度、催化剂与酚醛树脂质量比和升温速率等参数对热解油组成分布的影响规律。与母体H-ZSM-5催化剂相比,0.5Ga/ZSM-5在酚醛树脂快速热解中催化生产单环芳烃的效率更高,且更能有效抑制酚类化合物的生成。当热解温度为800℃、升温速率为10℃/ms时,单环芳烃的相对含量达到64.1%。     

生物质快速热解蒸气的在线催化研究

在固定床上对生物质流化床快速热解产生的蒸气进行了直接催化试验.选用HZSM-5催化剂,探讨了催化温度和催化剂量对催化后产物分布及生物油组分的影响.结果表明:在催化温度为375℃、催化剂量为30 mL时,可获得较高的液相产率(36.4%)、较低的气相产率(20.4%)和焦产率(13.9%).通过分析最佳工况下的生物油组分,发现精制油中含氧量高的有机酸、酯、酮、醛、呋喃等含量明显降低,而含氧量低的小分子酚类及不合氧的烃类含量大幅提高.     

分级孔HZSM-5催化烘焙预处理杨木快速热解制取芳烃

采用NaOH溶液对HZSM-5进行处理,通过XRD,BET,NH3-TPD方法对改性前后的HZSM-5进行表征。在管式炉中对杨木进行烘焙预处理,利用改性前后的HZSM-5在催化剂评价装置中进行烘焙预处理杨木的催化热解实验,探究杨木烘焙预处理温度和HZSM-5碱处理浓度对芳烃产物的影响。研究结果表明,碱处理后的HZSM-5形成了含有微-介孔的分级孔道结构,酸分布有所变化;随着NaOH浓度的增加,生物油中多环芳烃的含量逐渐降低,单环芳烃的含量呈现先增加后降低的趋势,在0.3-HZSM-5催化下达到最高产率58.12%;随着烘焙温度的升高,生物油中单环芳烃的含量先增加后降低,含氧化合物的含量先减小后增加,260℃烘焙预处理杨木催化热解效果最佳,芳烃化合物总收率达到82.01%,其中单环芳烃选择性达到70.87%。     

基于EPR检测技术的木质素模型化合物催化热解反应机理

针对生物质三大组分中最难分解的木质素,选取了愈创木酚及香兰素作为其模化物,为明晰其催化热解机理以实现对催化热解定向调控进行指导,采用电子顺磁共振(EPR)检测技术,结合Py-GC/MS的分析,研究了愈创木酚及香兰素催化热解的反应机理及反应路径.结果表明:以HZSM-5为催化剂,催化剂与反应物质量比为2∶1时,催化热解对于反应物的热解效果均优于非催化热解,愈创木酚催化热解主要液相产物有呋喃类、酚类、单环芳烃和多环芳烃.对于香兰素的催化热解产物主要为芳烃类、酚类和醛类.在催化热解过程中通过EPR技术可检测到甲基自由基的存在.依据自由基反应,分别梳理了愈创木酚及香兰素的催化热解机理及反应路径.     

改性ZSM-5催化热解生物质和低密度聚乙烯实验研究

通过碱处理和浸渍Zn制备了介孔双功能Zn/ZSM-5分子筛,在Pyroprobe 5200分析热解仪上研究对榉木和低密度聚乙烯(LDPE)共催化热解反应的催化性能。采用X射线衍射,N2-吸附脱附和吡啶红外等方法对催化剂的结构和酸性进行了表征。实验结果表明:ZSM-5分子筛经过改性之后,B酸酸量下降,L酸酸量上升。在榉木和低密度聚乙烯共催化快速热解中,改性分子筛显著提高了石油化学品的产率。与传统ZSM-5相比,介孔Zn/ZSM-5将共热解产物中高附加值单环芳烃和烯烃的产率提高了24.3%,同时抑制了多环芳烃的产生。这一结果表明,在生物质和LDPE共催化快速热解中,浸渍Zn和碱处理复合改性ZSM-5分子筛有利于提高转化效率和优化产物分布。     

基于镓改性ZSM-5分子筛作用下的环氧树脂催化热解制芳烃反应性能研究

为实现环氧树脂的清洁处置与资源化利用,在一系列金属镓改性的ZSM-5催化体系中进行快速热解实验,并进行了包括氮气吸附-脱附测试、X射线衍射（XRD）、氨气程序升温吸附（NH₃-TPD）、热重分析（TGA）和透射电镜（TEM）在内的全面的催化剂表征,以阐明催化剂的结构特性。镓的改性显著调节了ZSM-5分子筛的布朗斯特/路易斯酸分布和孔隙结构,改善了高温下分子筛的热解脱氧性能,提高了催化剂的择形催化能力。选取镓负载量、热解温度、催化剂用量、热解升温速率和催化剂回用次数为实验变量,探究了热解油组成分布的变化规律。结果表明,与未改性的分子筛相比,镓改性的ZSM-5分子筛显著提高了环氧树脂快速热解过程中芳烃的选择性。通过不同热解条件的研究发现,环氧树脂催化热解制备芳烃的最佳条件为：1Ga-ZSM-5分子筛∶环氧树脂 = 1∶1,热解温度为600℃,热解速率为10℃/ms,此时芳烃总选择性最高可达56.4%,其中更有价值的单环芳烃的相对含量达到31.6%。     

竹屑热解过程及产物特征研究

以竹屑为原料,选择250~950℃温度范围,在小型固定床反应器上探究竹材热解过程及产物特征。研究发现:随着热解温度的升高,固体焦炭产率减小,气体产率规律与之相反,液体产率先增后减,且在450℃时达到最大(52.28%)。固体焦炭中化学官能团的种类随温度的升高逐渐减少,含量随之减小,650℃之后除苯环结构外,基本无其他官能团,说明竹屑热解主要发生在650℃之前。在较低温度下,热解油中以呋喃类、醛酮类、酚类等含氧化合物为主,气体产物中主要以CO、CO_2为主,当温度超过750℃后,热解油以萘、苊等多环芳烃为主要含量,由于挥发分的二次裂解加剧,使CO和H_2体积分数增大,CH_4比例随温度变化缓慢。     

双金属共改性沸石催化杉木热解制备轻质芳烃

以杉木为原料在金属改性分子筛作用下进行热解制备芳烃,采用热裂解-气相色谱质谱法进行热解。结果表明：单金属改性中5%Zn/HZSM-5可达到最好催化效果,其芳烃的相对峰面积达到最高的34.17%,苯、二甲苯的产率相对最高;与单金属改性相比,1%Zn-4%Co/HZSM-5可增大单环芳烃产率,其中苯增大1.19倍,甲苯增大1.21倍;萘、甲基萘等大分子芳烃产率显著减小,同时氧化物产率减少。验证不同金属结合会产生某种协同效应,在热解过程中添加双金属改性分子筛有利于热解油品位的提高。通过NH₃-TPD表征和BET测试阐述金属改性对催化剂表面结构及酸位点变化的影响。     

Comparative study on pyrolysis and catalytic pyrolysis upgrading of biomass model compounds: Thermochemical behaviors,kinetics, and aromatic hydrocarbon formation

In order to understand the pyrolysis mechanism, reaction kinetic and product properties of biomass and select suitable agricultural and forestry residues for the generation desired products, the pyrolysis and catalytic pyrolysis characteristics of three main components (hemicellulose, cellulose, and lignin) of biomass were investigated using a thermogravimetric analyzer (TGA) with a fixed-bed reactor. Fourier transform infrared spectroscopy (FTIR) and elemental analysis were used for further characterization. The results showed that: the thermal stability of hemicellulose was the worst, while that of cellulose was higher with a narrow range of pyrolysis temperatures. Lignin decomposed over a wider range of temperatures and generated a higher char yield. After catalytic pyrolysis over HZSM-5 catalyst, the conversion ratio increased. The ratio for the three components was in the following order: lignincellulose < biomass < xylan. The Starink method was introduced to analyze the thermal reaction kinetics, activation energy (Ea), and the pre-exponential factor (A). The addition of HZSM-5 improved the reactivity and decreased the activation energy in the following order: xylan (30.54%) > biomass(15.41%) > lignin (14.75%) > cellulose (6.73%). The pyrolysis of cellulose gave the highest yield of bio-oil rich in levoglucosan and other anhydrosugars with minimal coke formation. Xylan gave a high gas yield and moderate yield of bio-oil rich in furfural, while lignin gave the highest solid residue and produced the lowest yield of bio-oil that was rich in phenolic compounds. After catalytic pyrolysis, xylan gave the highest yield of monocyclic aromatic hydrocarbons, 76.40%, and showed selectivity for benzene and toluene. Cellulose showed higher selectivity for xylene and naphthalene; however, lignin showed enhanced for selectivity of C10 + polycyclic aromatic hydrocarbons. Thus, catalytic pyrolysis method can effectively improve the properties of bio-oil and bio-char.     

Enhancing the aromatic hydrocarbon yield from the catalytic copyrolysis of xylan and LDPE with a dual-catalytic-stage combined CaO/HZSM-5 catalyst

The high concentration of oxygenated compounds in pyrolytic products prohibits the conversion of hemicellulose to important biofuels and chemicals via fast pyrolysis. Herein CaO and HZSM-5 was developed to convert xylan and LDPE to valuable hydrocarbons by thermogravimetric analysis (TGA) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and elucidate the reaction mechanism were also investigated in detail. The results indicated that xylan/LDPE copyrolysis was more complicated than pyrolysis of the individual components. LDPE hindered the thermal decomposition and aromatic hydrocarbon formation from xylan at temperatures under 350 °C and had a synergistic effect at high temperatures. 50% LDPE was proven to be more beneficial than other percentages for the formation of monocyclic aromatic hydrocarbons. Simultaneously, the addition of CaO/HZSM-5 significantly reduced the reaction Ea and increased the reaction rate. CaO can effectively improve the deoxygenation and aromatization reaction, enhancing the yield and selectivity of aromatics to a certain extent. The maximum yield of hydrocarbons (96.01%), mono-aromatic hydrocarbons (88.53%) and S_BTXE (85.79%) were obtained at a CaO/HZSM-5 ratio of 1:2, a pyrolysis temperature of 450 °C, a catalytic temperature of 550 °C, a catalyst dose of 1:2 and a xylan-to-LDPE ratio of 1:1 via an ex situ process. The system was dominated by toluene, xylene and alkyl benzene. Diels-Alder reactions of furans and hydrocarbon pool mechanism of nonfuranic compounds improved aromatic formation. This study provides a fundamental for recovering energy and chemicals from pyrolysis of hemicellulose.     

Catalytic pyrolysis of pinewood over ZSM-5 and CaO for aromatic hydrocarbon: Analytical Py-GC/MS study

A higher amount of oxygenates is the main constraint for higher yield and quality of aromatics in catalytic pyrolysis while a study of hydrocarbon production with a balance of reactive species lies importance in the catalytic upgrading of pyrolytic vapor. Catalytic pyrolysis of pinewood sawdust over acidic (ZSM-5) and basic (CaO) catalyst was conducted by means of Py-GC/MS to evaluate the effect of biomass to catalyst loading ratio on aromatic hydrocarbon production. Catalytic pyrolysis with four different biomass to catalyst ratios (0.25:1, 0.5:1, 1:1, and 2:1) and non-catalytic pyrolysis were conducted. It has been obtained that ZSM-5 showed better catalytic activity in terms of a high fraction of aromatic hydrocarbon. The ZSM-5 catalyst showed a potential on the aromatization as the yield of aromatic hydrocarbon was increased with a higher amount of ZSM-5 catalyst and the highest yield of aromatics (42.19 wt %) was observed for biomass to catalyst ratio of 0.25:1. On the other hand, basic CaO catalyst was not selective to aromatic hydrocarbon from pinewood sawdust but explored high deacidification reaction in pyrolytic vapor compared to ZSM-5 catalyst, whereas non-catalytic pyrolysis resulted in acidic species (13.45 wt %) and phenolics (46.5 wt %). Based on the results, ZSM-5 catalyst can only be suggested for catalytic pyrolysis of pinewood sawdust for aromatic hydrocarbon production.     

Influence of metal (Fe/Zn) modified ZSM-5 catalysts on product characteristics based on the bench-scale pyrolysis and Py-GC/MS of biomass

In this study, sawdust was selected as the raw material for biomass pyrolysis to obtain organic products. The catalyst was modified with two elements (Fe and Zn). Through analysis of the catalytic products, we attempted to identify a pyrolysis catalyst that can improve the yield of aromatic hydrocarbon products. ZSM-5, modified with Fe and Zn, was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and Brunauer–Emmett–Teller (BET) measurements. Tube furnace and flash pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) were used to comprehensively investigate the characteristics of the products of biomass pyrolysis. The highest yield of phenols was obtained using the Fe-modified ZSM-5 catalyst, which was 18.30% higher than the yield obtained by the pure ZSM-5 catalyst. The lowest yield of acid products was obtained by single-metal-supported catalytic pyrolysis with Fe or Zn, which was 50.66% lower than the yield obtained by direct pyrolysis. During the pyrolysis of biomass using metal-modified catalysts, the production of aromatic hydrocarbons was greatly improved. Among them, compared with direct pyrolysis, the Fe-Zn co-modified ZSM-5 catalyst exhibited the weakest promotion of aromatic hydrocarbon formation, but there was still a 68.50% improvement. Although the co-modified catalyst did not show absolute advantages under the conditions used for this experiment, the improvements in the production of aromatics and phenolic products also showed its potential for improving bio-oil products. Under the action of Fe-modified catalysts, the most abundant components in the gas product were CO and CO₂, which reached levels as high as 53.45% and 15.34%, respectively, showing strong deoxidation capabilities. Therefore, Fe-modified ZSM-5 catalysts were found to better promote the formation of aromatic hydrocarbon products of biomass pyrolysis.     

Microwave-induced pyrolysis of waste truck tyres with carbonaceous susceptor for the production of diesel-like fuel

Microwave-induced pyrolysis technique was utilised to pyrolyse waste truck tyres (TT) into useful pyrolysis oil with the aid of activated carbon. The effect of temperature was studied to determine the truck-tyre pyrolysis oil (TTPO) yield, hydrocarbon fractions, chemicals composition, energy yield and fuel properties. The activated carbon functions as microwave absorber to elevate the pyrolysis temperature for enhancing production of pyrolysis oil. The optimal pyrolysis temperature of 500 °C produces highest TTPO yield of 38.12 wt% with calorific value of 42.39 MJkg^?1 and energy yield of 40.55 wt%. Detailed analysis shows the TTPO contained large amount of aromatic hydrocarbons and limonene (14.29%) compared to pyrolysis oil from personal car tyre. Among the important chemical compounds also discovered in TTPO are benzene, toluene, xylene (BTX). The relative yields of toluene obtained at 400 °C is 14.85%, whereas the relative yields of benzene and xylene at 450 °C were 0.85 and 7.60%, respectively. The physiochemical properties of TTPO500 are rather similar to conventional diesel, except the slightly lower flash point and calorific value for the former. This work shows that microwave-induced pyrolysis is a promising technique to recover diesel-like fuel for use as supplemental alternative fuel.     

碱改性HZSM-5热解生物质模型化合物影响研究

实验采用Py-GC/MS在500 ℃下对NaOH、Na₂CO₃和有机碱（CTAB/TPAOH）改性HZSM-5催化热解生物质模型化合物的产物分布影响机制进行探究。结果表明,利用0.1 mol/L NaOH/Na₂CO₃改性HZSM-5使热解油中小分子酮、酚和酯类物质的收率有所提高,有利于碳链长度≥5产物（C_≥5）的生成;0.2 mol/L NaOH/Na₂CO₃改性HZSM-5催化剂有助于脱羰和脱羟基反应的进行,促使环状化合物开裂转化为链状化合物。TPAOH的加入使NaOH改性HZSM-5催化热解产物中酮类产物收率降至18.56%、醛类产物收率增至3.01%,并促使C_≥9产物向C_≤4转化,链状产物增加;经CTAB改性后C_≥9产物向C_5-8转化,环状产物增加。     

Preparation of bio-oil derived from catalytic upgrading of biomass vacuum pyrolysis vapor over metal-loaded HZSM-5 zeolites

The Fe-, Co-, Cu-loaded HZSM-5 zeolites were prepared via impregnation method. The upgrading by catalyst on biomass pyrolysis vapors was conducted over modified zeolites to investigate their catalytic upgrading performance and anti-coking performance. The Brønsted acid sites amount on Cu-,Co-loaded HZSM-5 decreased sharply, while that of Lewis both increased. The yield of liquid fraction and refined bio-oil over metal loaded ZSM-5 catalysts decreased, while that of char almost kept constant. The physical property of refined bio-oil was promoted in terms of pH value, dynamic viscosity and higher heating value (HHV). FT-IR analysis revealed that the chemical structure of refined bio-oil obtained over Fe-, Co-, Cu-loaded HZSM-5 zeolites was highly similar. The yield of monocyclic aromatic and aliphatic hydrocarbon over Fe-,Co-loaded HZSM-5 were boosted by around 2.5 times compared with original ZSM-5 zeolites. Data analysis revealed that Cu/HZSM-5 presented the worst deoxygenation ability. The anti-coking capability of Fe/HZSM-5 was obviously better, i.e., the coke content showed an approximate decrease of 38%. Thus, this study provided an efficient Fe/HZSM-5 catalysts for preparation of bio-oil derived from catalytic upgrading of biomass pyrolysis vapor.     

Catalytic co‐pyrolysis of Eichhornia Crassipes biomaѕѕ and polyethylene using waste Fe and CaCO3 catalysts

A wild aquatic plant, Eichhornia Crassipes, and polyethylene have been converted into liquid product thermo‐catalytically and cost effectively through co‐pyrolysis using batch steel pyrolyzer. The Fe and CaCO₃ catalysts were obtained as wastes from various mechanical processes. The catalytic process was compared with non‐catalytic pyrolysis. The effect of various reaction conditions was investigated in order to find out the optimized process conditions. It was found that the favorable reaction conditions were 450 °C temperature and 1‐h reaction time at a heating rate of 1 °C/s and 0.4‐mm biomass particle size. The bio‐oil yield was found to be 34.4% and 26.6% using Fe and CaCO₃ respectively with catalysts particle size of 0.4 mm at the optimized reaction conditions and 5 wt% of biomass. The non‐catalytic and catalytic co‐pyrolysis using Fe as catalyst produced 23.9% and 28.7% oil respectively. Thus the efficiency of processes in terms of bio‐oil production was found in order of: Fe > CaCO₃ > non‐catalytic pyrolysis. The GC/MS analysis of n‐hexane extract of bio‐oil shows that Fe catalyst favors formation of aliphatic hydrocarbons while CaCO₃ and non‐catalytic pyrolysis favors formation of aromatic hydrocarbons. Mostly unsaturated aliphatic hydrocarbons were formed in case of co‐pyrolysis reactions. The calorific value of bio‐oil was also measured in order to find out the fuel properties of the products. Copyright © 2016 John Wiley & Sons, Ltd.