改性HZSM-5催化玉米秸秆与HDPE共热解制轻质芳烃

为提高生物质与聚乙烯共热解中苯、甲苯、乙苯、二甲苯和萘(简称)BTEXN和轻烯烃的产量，同时抑制C⁺₂₁蜡的形成，通过TG-MS/FTIR和Py-GC/MS探究催化共热解中HZSM-5和改性HZSM-5对玉米秸秆和HDPE相互作用的影响，并对BTEXN进行定量分析。结果表明，在HZSM-5的催化共热解中，HZSM-5可促进玉米秸秆与HDPE之间的相互反应，芳烃和轻烃产率增加。相比HZSM-5，在改性HZSM-5的催化共热解中，改性HZSM-5可促进轻烯烃、C₅-C₁₁脂肪烃和芳烃的析出，并抑制C⁺₂₁蜡的形成。Cu、Fe和Ce改性可促进单环芳烃的形成，同时提高BTEXN产量，相比HZSM-5分别提高20.99、25.43和20.89 mg/g，而P改性会抑制BTEXN形成。对于形成芳烃的Diels-Alder反应，Fe和Ce改性表现出较强的催化效果，而Cu改性对烃池反应催化效果较强。此外积碳分析表明，Fe和P改性具有较强的抗积碳能力。     

快速外热式热解工艺对生物质热解产物的影响

焦油一直是生物质热解技术发展的瓶颈。文中研究了快速外热式热解工艺对生物质热解产物的影响。研究表明:快速外热式热解工艺可以有效地避免常规热解过程中出现的原料夹生问题,缩短从加料到开始热解的时间,减少温度上升期间焦油的产生;由于热解温度高,速度快,大分子芳香族化合物发生二次热解,支链断裂生成小分子的烷、氢等物质,提高了热解气的产率和热值;焦油中CmHn等较大分子通过热解和重整的方式变成生物质气,降低了热解产物中焦油含量;热解过程中,由于生物质炭中的芳香族化合物分解成小分子的烷烃、烯烃等进入生物质燃气中,剩余的主要是固定碳,所以生物质炭的产率较低,其它物相与灰烬的相同。     

生物质与污水污泥共热解特性研究

采用热重分析仪(TGA)对生物质与城市污水污泥单独及共热解基本热解特性进行了考察,并结合测定的生物质中纤维素、半纤维素和木质素含量对共热解过程热解特性的影响规律发现:升温速率为20℃/min时,污泥单独热解分为水分析出、挥发分析出和焦炭化3个阶段;由生物质单独热解特性分析可知,松木屑热解特性最优,花生壳次之,狐尾藻最差;通过不同生物质添加量时的共热解过程考察,得知较高的生物质添加量更有利于共热解过程的进行;结合共热解特性变化与生物质组成的关系可知,含纤维素和木质素较多的松木屑与污泥共热解时有明显的协同作用发生,含木质素较多的花生壳也有较为明显的协同作用,含半纤维素较多的狐尾藻协同效果不明显。     

基于模型化合物的脱硫灰催化提质生物质热解气研究北大核心CSCD

该研究从清洁转化脱硫灰和生物质资源出发,利用自制的碳基固废热解炉研究了低温条件下(<600℃)脱硫灰对棉杆热解的催化效果。研究发现:脱硫灰明显促进了棉杆的热分解,提高了棉杆热解气产率和低位热值,提高了棉杆热解气中H_(2),CH_(4)和C_(2)H_(6)等富氢气的产量,同时,脱硫灰的催化效果降低了热解气中CO和CO_(2)的产量。通过模型化合物法研究发现:脱硫灰对棉杆中的纤维素和木质素成分生成热解气的过程有不同的催化效果;脱硫灰促进了脱硫灰/棉杆催化热解过程中纤维素生成H2和木质素生成CH4的化学反应,抑制了纤维素生成CO和CO_(2)的化学过程。     

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。     

TG-MS联用研究生物质的热解特性

采用TG-MG技术研究稻秆、稻壳和玉米芯的热解特性。采用活化热解区与消极热解区法、热解特性指数法分析了3种生物质的热解特性,质谱分析重点关注热解过程中不凝性气体和焦油产物的形成。结果表明:(1)含木质素较低的秸秆类生物质在消极区的热解不活跃;在同升温速率下,3种生物质的热解难易程度为:玉米秆玉米芯稻秆;(2)含氧气体量大大高于烃类和H2,H2O是所有试样中的主要产物;在相同实验条件下,稻秆热解生成H2O最多,而生成焦油量最少;而玉米秆和玉米芯生成少量H2O和大量焦油;对于不可凝性气体产物,CO和CO2是主要的气体产物,而H2和CH4只占小部分;(3)焦油的主要产物为苯、甲苯和苯酚,除苯在550℃后还有析出外,其余芳香烃产物的析出范围均为300℃~550℃。     

生物质/塑料共热解热重分析及动力学研究

考察了生物质、塑料(高密度聚乙烯、低密度聚乙烯和聚丙烯)及其混合物的热重行为。结果表明,生物质的分解温度比塑料低,3种塑料HDPE、LDPE、PP有相似的热解失重行为,是由于分子结构的相拟性。生物质的失重率低是由于灰分和固定炭含量高。生物质和塑料存在重叠的热解温区,有利于塑料向生物质供氢。生物质/塑料共热解时在高温区存在明显的协同效应。动力学分析表明,采用1或3个连续一级反应模型可很好地拟合实验数据,活化能和指前因子分别为107～217 kJ/mol和2.99×10~8～7.51×10~(34),取决于材料本身的特性。     

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。     

梨木炭蒸汽气化制取富氢燃气的试验研究

生物质气化技术已得到广泛的应用,但气化过程产生的焦油会影响设备稳定运行。为了大幅减少焦油的干扰,以梨木的热解炭为原料,在管式炉中进行水蒸气气化制取富氢燃气试验研究,探究了反应温度、K₂CO₃添加量及利用次数对气化特性的影响。结果表明：900℃时H₂的产气量为2.19 L/g,合成气中H₂含量超过58%;K₂CO₃添加量为10%时产气效果最佳,此时合成气中H₂+CO含量达到了88.5%。当K₂CO₃催化剂在第三次利用时,仍有较好的催化效果。     

基于密度泛函理论的海藻热解中美拉德反应机理研究

文中研究旨在通过密度泛函理论计算更好地从分子层面理解纤维素单元(葡萄糖和鼠李糖)与三种典型的脂肪氨基酸(脯氨酸、缬氨酸、亮氨酸)的共热解机理,深入了解生物质热解过程中纤维素组分对含氮组分热解过程的影响。研究发现葡萄糖与脯氨酸的反应能垒最高,而亮氨酸比较容易发生反应。并且葡萄糖自身也较易发生闭环反应生成呋喃类化合物(糠醛),这也是热解产物中糠醛多的原因。鼠李糖与脯氨酸热解过程中的第一个基元反应的过渡态形成的自由能能垒极高,而后生成相当稳定的缩合产物。而亮氨酸与鼠李糖的反应能垒最低,反应更容易发生。同时,我们发现鼠李糖由于其L型手性结构及6-脱氧特殊结构,在Amadori重排后发生了两次脱水形成多重度不饱和化合物。本研究为揭示生物质热解过程中糖类化合物与氨基酸之间的相互作用及含氮产物的生成途径奠定基础,对生物质的清洁高效利用有重要的意义。     

Investigating the release behavior of biomass and coal during the co-pyrolysis process

The release behavior of biomass and coal in the co-pyrolysis process was investigated. The release characteristics of the small molecules from 100 to 1000 °C were researched by TG-MS at the heating rate of 30 °C/min. The pyrolysis products during the co-pyrolysis process were compared with that in the separate pyrolysis process. It is found that the changes of pyrolysis products in the co-pyrolysis process are similar to that in the separate pyrolysis process. The main pyrolysis products of the biomass are released at the temperature lower than 500 °C. Some of the small molecules of Shenfu coal release at the temperature higher than 900 °C. The yields of aromatic compounds in biomasses are lower than that in Shenfu coal. In addition, most of the raw materials are pyrolyzed independently during the co-pyrolysis process. The differences between the experimental values and calculated values are slightly. With the addition of biomass, the content variations of aromatic compounds are not significant.     

Co-pyrolysis and co-gasification of biomass and polyethylene: Thermal behaviors,volatile products and characteristics of their residues

Co-pyrolysis and co-gasification of biomass and plastics could be a promising method to alleviate environmental pollution and provide renewable energy. In this paper, co-pyrolysis and co-gasification of eucalyptus wood (EW) or rice straw (RS) with polyethylene (PE) were investigated by a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR) and a scanning electron microscope coupled with energy-dispersive spectroscopy (SEM/EDS). Results showed that the pyrolysis behaviors were characterized by two stages. The first stage was the decomposition of EW and RS, and the second stage primarily consisted of the degradation of PE. The gasification exhibited a third stage for the reaction of products with CO₂. A synergistic effect was presented in the pyrolysis and gasification of biomass with PE, and it could have a positive effect on the decomposition of biomass. Compared to individual pyrolysis and gasification, co-pyrolysis and co-gasification generated no new substances, but the yield of some products was changed in these processes. In co-pyrolysis, the decomposition of biomass was promoted. In co-gasification, the production of CH₄, CO and oxygenated compounds was inhibited, while the reaction to generate H₂O was promoted. Gasification and the addition of PE both increased the carbon content and reduced the oxygen content of volatile products. Additionally, more metal elements could be deposited in residues when PE was added.     

Synergistic effects during co-pyrolysis of biomass and plastic: Gas,tar, soot,char products and thermogravimetric study

Synergistic effects of biomass and plastic co-pyrolysis on gas, tar, soot and char production and pyrolysis kinetics were studied using a fixed-bed reactor and a thermogravimetric analyzer, respectively. These pyrolysis products' yields and compositions were measured during the individual pyrolysis of biomass and plastic at 800–1100 °C, and synergistic effects were explored under non-sooty (900 °C) and sooty (1100 °C) conditions. Results shows that the soot starts to form from tar at 900–1000 °C for both biomass and plastic and that the soot from plastic pyrolysis is of greater yield and size than the biomass pyrolysis. Under non-sooty conditions, the synergistic effect of co-pyrolysis results in higher char yields but lower tar yields, while under sooty conditions co-pyrolysis inhibits the gas and soot formation, resulting in higher tar yields and different soot morphologies. The synergistic effect observed by the thermogravimetric analysis agrees with that in a fixed-bed reactor.     

Multifaceted analysis of products from the intermediate co-pyrolysis of biomass with Tetra Pak waste

This study investigates the co-pyrolysis of two types of biomass (pine bark and wheat straw) with Tetra Pak waste (TPW). The experiments were performed using a fixed-bed reactor equipped with an innovative system, where a sample was rapidly heated to 600 °C before being rapidly cooled. The multifaceted analysis included the determination of the i) physical and chemical properties of the feedstocks and chars, ii) aqueous phase, tars, and waxes, iii) char ignition and burnout temperature, iv) chemical composition of gas, and v) distribution of carbon and hydrogen in the obtained products. The results showed that the addition of TPW to the both types of biomass significantly reduced the char mass and aqueous phase, decreased the carbon, hydrogen, and nitrogen contents of the char, and increased the wax and tar yields retained in the water cooler. Different organic compounds such as alkenes, aromatic hydrocarbons, and acids were found in tars and waxes. The chemical composition of the released gases was detected in situ (by a flue-gas analyser) and ex-situ (using gas chromatography). Changes in the concentrations of H₂, CH₄, CO, CO₂, and C2–C4 were observed. The addition of Tetra Pak to the two types of biomass had an evident and positive effect on the hydrogen content of the pyrolysis gas.     

Production of hydrogen by lignins fast pyrolysis

This paper reports the results of experiments performed on the flash pyrolysis of lignin samples submitted to controlled heat flux densities (short flashes of a concentrated radiation). Two types of lignins are used: Kraft and Organocell lignins. Microscopic observations of the reacted samples reveal the formation of an intermediate liquid compound that precedes the further formation of char, vapours and gases. The rates of mass loss and the production rates of the products are determined for both lignins. The results are compared to each other and to those obtained in former similar studies made with cellulose.

The analyses of the produced gases reveal high syngas and H₂ contents (respectively 87 and 50 mol%). This composition is compared to results obtained in other different thermal conditions with lignins and other types of biomasses. The possible mechanism of hydrogen formation is further discussed.     

Low energy consumption and high quality bio-fuels production via in-situ fast pyrolysis of reed straw by adding metallic particles in an induction heating reactor

An in-situ fast pyrolysis of biomass by adding metallic particles in an induction heating reactor was proposed to produce high quality bio-fuels. After adding metallic particles into biomass, the times required to reach complete pyrolysis during reed straw pyrolysis process were significantly reduced up to 28.9%. The yields of combustible gas and bio-oil products were significantly increased. Furthermore, higher-quality combustible gas and bio-oil products were obtained with the LHV of gas products and HHV of bio-oil (dry basis) increased by 14.2%–19.1% and 4.16%–16.35%, respectively, under 400–600 °C. The lower oxygen content and higher yields of aromatics, alkenes and alkanes contents in bio-oil were obtained after metallic particles addition. More importantly, up to 26.5% of the total energy consumption during pyrolysis process was reduced after adding metallic particles into biomass in an induction heating reactor. The results indicate that adding metallic particles into biomass in an induction heating reactor can significantly enhance the heat transfer, decomposition reaction intensity and energy utilization efficiency of biomass pyrolysis process with lower energy consumption and higher-quality bio-fuel production.     

Effect of lignin on the co-pyrolysis of sludge and cellulose

In order to investigate the role of the lignin in the co-pyrolysis process of the sludge and the cellulose, the co-pyrolysis process was carried out in a thermogravimetry analyzer. The result shows that when the proportion of the sludge:cellulose:lignin was 1:1:0.4, the main co-pyrolysis temperature range was narrower, the ultimate pyrolysis weight loss was more, and the synergistic effect had a longer duration time. When the pyrolysis temperature was below 400°C, the addition of the lignin could promote the co-pyrolysis process of the cellulose and the sludge, such as the decrease of the activation energy E.     

麦秆酶解残渣热解特性及动力学分析

对比分析了麦秆及其酶解残渣的基础物化特性,利用热重−红外联用技术研究了酶解残渣的热解反应过程及其主要气体产物的析出特性,并用混合反应模型计算了酶解残渣热解过程的表观动力学参数。结果表明,麦秆酶解残渣是一种富含木质素的高灰分、低热值的生物质原料,与麦秆原料相比,其热解过程相对平缓,主要失重温度区间为200℃ ~ 800℃,最大失重峰为350℃,与木质素的热解特性相近;提高升温速率可以使酶解残渣热解反应剩余产物质量明显减少,最大失重速率提高;热解主要气体产物中CH4析出的温度区间为400℃ ~ 700℃,CO和CO2在380℃、450℃和650℃都存在析出峰。动力学分析结果表明,酶解残渣热解过程在低温区（200℃ ~ 350℃）和高温区（350℃ ~ 800℃）分别遵循一级和二级反应动力学规律。     

Hydrogen production by biomass gasification in supercritical or subcritical water with Raney-Ni and other catalysts

Gasification of peanut shell, sawdust and straw in supercritical or subcritical water has been studied in a batch reactor with the presence of a series of Raney-Ni and its mixture with ZnCl₂ or Ca(OH)₂. The main gas products were hydrogen, methane, carbon dioxide, and a small amount of carbon monoxide. Different types of Raney-Ni, containing different metal components such as Fe, Mo or Cr, have different influences on the gasification yield and hydrogen selectivity. The catalysis effect can be improved obviously by adding ZnCl₂ or Ca(OH)₂. Increasing the reaction temperature or adding ZnCl₂ and Ca(OH)₂ could improve the mass of H₂ in gas products and reduce the mass of CH₄ and CO₂ at the same time. The possible mechanism is that ZnCl₂ can decompose the biomass particle by accelerating cellulose hydrolyzation in high-temperature water, increasing more specific surface to admit catalysts, while Ca(OH)₂ can absorb CO₂ to produce CaCO₃ deposit, which can drop out from the reactant system, and which will drive the reaction to get more hydrogen. With respect to the biomass conversion to gas product and selectivity of H₂ at low temperature, the series of Raney-Ni has shown many advantages over other catalysts; thus, this kind of catalyst has great potential to be utilized in the hydrogen industry for the gasification of biomass.