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.     

Pyrolysis of Alternanthera philoxeroides (alligator weed): Effect of pyrolysis parameter on product yield and characterization of liquid product and bio char

In the present work, fast pyrolysis of Alternanthera philoxeroides was evaluated with a focus to study the chemical and physical characteristics of bio-oil produced and to determine its practicability as a transportation fuel. Pyrolysis of A.philoxeroides was conducted inside a semi batch quartz glass reactor to determine the effect of different operating conditions on the pyrolysis product yield. The thermal pyrolysis of A. philoxeroides were performed at a temperature range from 350 to 550 °C at a constant heating rate of 25 °C/min & under nitrogen atmosphere at a flow rate of 0.1 L/min, which yielded a total 40.10 wt.% of bio-oil at 450 °C. Later, some more sets of experiments were also performed to see the effect on pyrolysis product yield with change in operating conditions like varying heating rates (50 °C/min, 75 °C/min & 100 °C/min) and different flow rates of nitrogen (0.2, 0.3, 0.4 & 0.5 L/min). The yield of bio-oil during different heating rate (25, 50, 75 and 100 °C/min) was found to be more (43.15 wt.%) at a constant heating rate of 50 °C/min with 0.2 L/min N₂ gas flow rate and at a fixed pyrolysis temperature of 450 °C. The High Heating Value (HHV) value of bio-oil (8.88 MJ/kg) was very less due to presence of oxygen in the biomass. However, the high heating value of bio-char (20.41 MJ/kg) was more, and has the potential to be used as a solid fuel. The thermal degradation of A. philoxeroides was studied in TGA under inert atmosphere. The characterization of bio-oil was done by elemental analyser (CHNS/O analyser), FT-IR, & GC/MS. The char was characterized by elemental analyser (CHNS/O analysis), SEM, BET and FT-IR techniques. The chemical characterization showed that the bio-oil could be used as a transportation fuel if upgraded or blended with other fuels. The bio-oil can also be used as feedstock for different chemicals. The bio-char obtained from A. philoxeroides can be used for adsorption purposes because of its high surface area.     

生物质热解液化技术研究现状

对生物质热解液化技术及其液化机理进行阐述,并介绍国内外生物质热解反应器类型及其发展现状,分析热解过程中的影响因素。生物质热解液化技术很大程度上能缓解当今社会的能源危机和环境污染,是人类开发可再生资源的一种有效途径。     

生物质热裂解制取液体燃料技术的发展

对生物质热裂解技术进行了系统的研究，阐述了其基本技术要求和发展现状，并将现有的生物质热裂解反应器进行分类，分析了相应的优势与不足。最后评估了生物质热裂解制取液体燃料技术的经济和社会效益，结果表明它具有广泛的应用前景。     

我国生物质热解液化技术的现状

文章主要阐述了我国生物质热解液化技术的研究现状，包括现有的热裂解液化装置、反应动力学模型、已检测出的不同原料裂解产生的生物油成分及其物理特性分析，提出了生物油精制的必要性和未来需要研究的问题。     

Hydrogen production via catalytic pyrolysis of biomass in a two-stage fixed bed reactor system

This study introduces an innovative process of generating hydrogen-rich gas from biomass through the catalytic pyrolysis of biomass in a two-stage fixed bed reactor system. Water hyacinth was used as the biomass feedstock. The effects of various factors such as pyrolysis temperature, catalytic bed temperature, residence time, catalyst, and the nickel content of the catalyst on the pyrolysis productivity were investigated and the yields of H₂, CO, CH₄, and CO₂ were obtained. Results showed that the high productivity of hydrogen can be obtained particularly by increasing the catalytic bed temperature, residence time, and catalysts. The favorable reaction conditions are as follows: a first-stage pyrolysis temperature of 650 °C–700 °C, a second-stage catalytic bed temperature of 800 °C, a catalytic pyrolysis reaction time of 17 min, and a nickel content of 9% (wt %).     

生物质的热裂解与热解油的精制

生物质能属于可再生能源，其利用符合社会可持续发展的原则。生物质在中等温度下(约500℃)热裂解主要得到热解油。介绍了温度对热裂解过程的影响、热解油——水的二元相图、热裂解过程的机理和热解油的特性，综述了催化剂种类，溶剂等对热解油催化裂解的影响。结果表明，催化剂H-ZSM-5的脱氧效果最好，以四氢萘为溶剂时，精制油的收率大幅提高，达39．4％。     

生物质热解液化技术经济分析

我国生物质资源十分丰富，但主要以各类农业残余废弃物为主，其特点是能量密度低、分布不集中，如果采用热解液化技术在产地将其先分散转化成生物油，然后再对生物油进行应用或再加工，则就避免了大规模收集和长距离运输生物质所带来的巨大困难。研究分析表明：热解液化设备的规模以每小时可处理2t农业残余废弃物较为适宜，且这种技术在我国具有良好的市场应用前景。     

Product distribution from solar pyrolysis of agricultural and forestry biomass residues

Solar pyrolysis of pine sawdust, peach pit, grape stalk and grape marc was conducted in a lab-scale solar reactor for producing fuel gas from these agricultural and forestry by-products. For each type of biomass, whose lignocellulose components vary, the investigated parameters were the final temperature (in the range 800°C–2000 °C) and the heating rates (in the range 10–150 °C/s) under a constant sweep gas flow rate of 6 NL/min. The parameter influence on the pyrolysis product distribution and syngas composition was studied. The experimental results indicate that the gas yield generally increases with the temperature and heating rate for the various types of biomass residues, whereas the liquid yield progresses oppositely. Gas yield as high as 63.5wt% was obtained from pine sawdust pyrolyzed at a final temperature of 2000 °C and heating rate of 50 °C/s. This gas can be further utilized for power generation, heat or transportable fuel production.     

Influence of temperature and residence time in the pyrolysis of woody biomass waste in a continuous screw reactor

The aim of this paper is to study the influence of temperature and residence time in the quality of the charcoal obtained in the pyrolysis of biomass waste, in order to be used as a reducing agent in metallurgical applications. Woody biomass waste (pinus pinaster) coming from forest activities carried out in the north of Spain has been pyrolyzed in a laboratory scale screw continuous reactor connected to a second reactor where the pyrolysis vapors have been thermally treated to promote further cracking, with the aim of diminishing tars and improving the composition of the gas phase.Both the peak temperature and the exposition time at peak temperature have an impact in the pyrolysis fractions yields and composition, however it is at 1173 K where the bigger changes occur both in pyrolysis products yield and composition. In all cases the solids obtained (charcoal) fulfill the requirements to perform as metallurgical reducers. The higher the peak temperature the greater the charcoal quality but the lower the pyrolysis solid yield since secondary pyrolysis reactions consume charcoal. The pyrolysis gases obtained are valuable products rich in CO (22–35 vol%) and hydrogen (35–50 vol%); on the contrary, the pyrolysis liquids obtained are mainly worthless products composed of water and some aromatic compounds (e.g. naphthalene, fluorene & antrhacene).     

生物质在高频耦合等离子体中的热解气化研究

采用高频电容耦合等离子体热解技术对生物质原料进行了热解气化试验，研究气体产物产率、成分随反应条件的变化规律。反应在3000-8000Pa的真空范围内进行，热解温度为1000～2000K。该技术可大幅度提高生物质气的热值及产率，本试验中产气率达到了66％以上，并且还有提高的潜力。     

Preparation and characterization of bio-oil by microwave pyrolysis of biomass

A low temperature method was used to produce bio-oil from fir sawdust by means of microwave pyrolysis. Effects of reaction temperature, ratios of the microwave absorption medium to sawdust, and reaction time on the yield of bio-oil were investigated. The results show that an optimized yield of 21.22% is achieved. Bio-oil obtained was analyzed by gas chromatography-mass spectrometry and Fourier transform infrared, and the result reveals that the product mainly consists of phenolic compounds with esteric compounds as the minor components. Thermal weight loss curves of bio-oil were determined by thermogravimetry-differential thermal analysis in the oxygen atmosphere at different super-heating rates, and combustion kinetic parameters were calculated.     

Gasification of torrefied oil palm biomass in a fixed-bed reactor: Effects of gasifying agents on product characteristics

Gasification represents an attractive pathway to generate fuel gas (i.e., syngas (H₂ and CO) and hydrocarbons) from oil palm biomass in Malaysia. Torrefaction is introduced here to enhance the oil palm biomass properties prior to gasification. In this work, the effect of torrefaction on the gasification of three oil palm biomass, i.e., empty fruit bunches (EFB), mesocarp fibres (MF), and palm kernel shells (PKS) are evaluated. Two gasifying agents were used, i.e., CO₂ and steam. The syngas lower heating values (LHV_syngas) for CO₂ gasification and steam gasification were in the range of 0.35–1.67 MJ m⁻³ and 1.61–2.22 MJ m⁻³, respectively. Compared with EFB and MF, PKS is more effective for fuel gas production as indicated by the more dominant emission of light hydrocarbons (CH₄, C₂H₄, and C₂H₆) in PKS case. Gasification efficiency was examined using carbon conversion efficiency (CCE) and cold gas efficiency (CGE). CCE ranges between 4% and 55.1% for CO₂ gasification while CGE varies between 4.8% and 46.2% and 27.6% and 62.9% for CO₂ gasification and steam gasification, respectively. Our results showed that higher concentration of gasifying agent promotes higher carbon conversion and that steam gasification provides higher thermal efficiency (CGE) compared to CO₂ gasification.     

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。     

生物质热解制炭与制气一体化研究

在自行设计的管式炉上进行生物质热解制炭与制气一体化研究,对生物质种类和热解终温两个因素进行了实验和分析,得到了生物质热解过程中气体析出的规律和固体炭的产率。当以制炭和制气一体化为目的,在4种生物质原料中选用麦秆,热解终温选择500℃时,可以得到较大的固体炭产率和气体析出浓度。     

生物质燃料层热解过程的传热传质模型研究

通过分析生物质热解过程的传热传质特点,建立了生物质燃料层热解过程的传热传质教学模型。通过数值计算,研究了生物质燃料层在热解过程中所发生的热量和质量迁移现象,分析了热解过程生物质床内部温度场的分布、生物质固体密度的变化和热解区的迁移规律。     

Heat transfer controlled pyrolysis kinetics of a biomass slab, rod or sphere

A theory for deriving the pyrolysis rate of a single infinite slab, infinite cylinder or sphere in a constant temperature furnace is suggested. In analogy with the shrinking-core model a pyrolysis propagation front velocity is defined. The velocity is thereafter used in a compartment-model approach for deriving a set of ordinary differential equations for solving the burn-off over time. A comparison with experimental and published data is also made.     

Experimental investigation of the pyrolysis of biomass to produce green fuels

This work aims to utilise the experimental approach to perform the analysis of three-biomass feed stocks – bamboo, mustard and camellia and to provide insight into the operation and design of pyrolysis processes. Experiments on biomass fast pyrolysis were performed in a fixed bed (tubular) reactor at a temperature of 500°C and a residence time of 2?min under the constant flow of nitrogen. The analysis of pyrolysis gases and bio oil produced by pyrolysis was done using GC-MS and GC-TCD. Hydrous pyrolysis of biomasses was performed in a high-pressure autoclave for the temperature range 250–400°C and at a pressure of 20?bar with 30?min of residence time. Experiments were conducted both with and without the use of a catalyst. The pyrolysis vapour is made to pass through the catalyst bed of ZSM-5 (Si/Al?=?35). The results for all the biomass samples are then compared.     

生物质及其热裂解产物生物油的特性分析

以红松、白松、落叶松、玉米秸秆等不同生物质为原料,对流化床反应器热裂解制取的生物油进行了研究试验,通过对生物油的物理特性及其成分的分析,得出的实验结果表明:红松制取的生物油品质最好,热值高,含水率低,更适合进一步改性研究和应用,并利用现代精密仪器GC-MS对生物油进行了组分分析,解释了生物油高含氧和高含水特性。     

Catalytic fast pyrolysis of rice husk: Influence of commercial and synthesized microporous zeolites on deoxygenation of biomass pyrolysis vapors

Research on utilization of abundant rice residue for valuable bioenergy products is still not explored completely. A simple, robust, cheap, and one‐step fast pyrolysis reactor is still a key demand for production of bioenergy products, ie, high quality bio‐oil and biochar. Bio‐oil extracted from fast pyrolysis does not have adequate quality (eg, acidic and highly oxygenated). Catalytic fast pyrolysis using zeolites in the fast pyrolysis process effectively reduces the oxygen content (no H₂ required). In this paper, the zeolites with different pore sizes and shapes (small pore, SAPO‐34 (0.56) and ferrierite (30); medium pore, ZSM‐5 (30), MCM‐22 (30), and ITQ‐2 (30); and large pore zeolite, mordenite (30)) were tested in a drop‐type fixed‐bed pyrolyzer. Catalytic deoxygenation is conducted at 450°C at the catalyst/biomass ratio of 0.1. Zeolite catalysts, its pore size and shape, could influence largely on deoxygenation. It was found that the small pore zeolites did not produce aromatics as compared to higher amount of aromatics formed in case of medium pore zeolites. ZSM‐5 and ITQ‐2 zeolites were especially efficient for the higher deoxygenation of biomass pyrolysis vapors due to better pore dimension and higher acidity.