Study of the potential valorisation of heavy metal contaminated biomass via phytoremediation by fast pyrolysis: Part II: Characterisation of the liquid and gaseous fraction as a function of the temperature

Fast pyrolysis of heavy metal contaminated birch (CMB), resulting from phytoremediation, is investigated. The effect of the pyrolysis temperature (673, 773, 873 K) on the composition and evolution of the bio-oil/tar fraction and the gas fraction has been studied. The knowledge of the composition of the gaseous and liquid pyrolysis fractions, as a function of the pyrolysis temperature, affects directly future applications and valorisation of the pyrolysis products and are indispensable for making and selecting the proper thermal conditions for their optimal use. In view of the future valorisation of this heavy metal contaminated biomass, the pyrolysis temperature is imperative, because some of the heavy metals can volatilize at temperatures generally used for the co-combustion or fast pyrolysis of biomass.     

An FT-IR spectroscopic study of carbonyl functionalities in bio-oils

Pyrolysis bio-oil contains abundant O-containing structures. Carbonyls are particularly important not only because they are abundant and exist in many forms (e.g. as acids, esters, ketones and aldehydes) but also because they are reactive and are a key consideration of bio-oil upgrading. This study aims to investigate the distribution of carbonyl groups in a variety of bio-oil samples prepared from the pyrolysis of mallee wood, bark and leaves in a fluidised-bed reactor. Some bio-oil samples also underwent esterification reactions with methanol in the presence of solid Amberlyst acid catalyst. The bio-oil samples were diluted with isopropanol prior to the acquisition of FT-IR spectra using a CaF₂ liquid cell. The FT-IR spectra of bio-oils in the range of 1490–1850 cm⁻¹ were deconvoluted with 9 Gaussian bands. Our results reveal that the bio-oils from the pyrolysis of wood, bark and leaves of the same mallee tree species had very different concentrations and types of carbonyls, which are related to the contents of hemicellulose, cellulose, lignin and extractives in the wood, bark and leaves. Our study also reveals that the carbonyls in the light and heavy fractions of a bio-oil may react differently during the reactions of bio-oil with methanol in the presence of the Amberlyst solid acid catalyst.     

重质生物油理化性质及其热解特性研究

利用核磁共振波谱仪（NMR）与气相色谱/质谱联用仪（GC/MS）对重质生物油理化性质进行表征,并应用热重分析仪（ TG-DTG）与热裂解仪-气相色谱/质谱联用仪（Py-GC/MS）对重质生物油热解特性进行研究。结果表明：重质生物油主要由芳香族化合物和糖类物质组成。重质生物油在N₂氛围下热解主要分为三个阶段: 室温~300℃为蒸发段,300～520℃为热解段,520～800℃为成焦段。重质生物油经不同温度热解后,产物种类有明显差异：中温段（低于500℃）热解时,产物种类随温度的升高逐渐增加;高温段（高于500℃）热解时,随着热解温度的提高,产物种类逐渐趋于稳定。     

稻壳快速热裂解生物油的特性研究

Physicochemical properties of bio-oil obtained from fast pyrolysis of rice husk were studied in the present work.Molecular distillation was used to separate the crude bio-oil into three fractions viz.light fraction,middle fraction and heavy fraction.Their chemical composition was analyzed by gas chromatograph and mass spectrometer(GC-MS).The thermal behavior,including evaporation and decomposition,was investigated using thermogravimetric analyzer coupled with Fourier transform infrared spectrometer(TG-FTIR).The product distribution was significantly affected by contents of cellulose,hemicellulose and lignin.The bio-oil yield was 46.36%(by mass) and the yield of gaseous products was 27%(by mass).The chemicals in the bio-oil included acids,aldehydes,ketones,alcohols,phenols,sugars,etc.The light fraction was mainly composed of acids and compounds with lower boiling point temperature,the middle and heavy fractions were consisted of phenols and levoglucosan.The thermal stability of the bio-oil was determined by the interactions and intersolubility of compounds.It was found that the thermal stability of bio-oil was better than the light fraction,but worse than the middle and heavy fractions.     

不同金属氧化物对重质生物油再裂解的比较性研究

通过TG-FTIR、GC/MS和XRD等分析手段,研究了Fe₂O₃、Al₂O₃、CaO和TiO₂四种金属氧化物催化下重质生物油的热解特性及产物差异。结果表明：应用上述四种催化剂的再裂解实验均促进了重质生物油的脱氧,其中CaO催化下脱氧效果最好,Al₂O₃能够有效降低反应温度,Fe₂O₃有效促进了重质生物油成炭前的解聚、固相产物质量降幅达21.23%,TiO₂对CO₂的生成有最明显的抑制效果、同时可以降低反应结束温度;在低温下,除CaO外的三种催化剂均对有效产物的生成有促进作用,但对不同种类的物质各有侧重,而CaO则会使反应所需温度升高且对愈创木酚的富集有很强的选择性;在中温下,CaO和TiO₂表现出较好的催化效果。上述催化热解过程有效促进了酚类的富集,效果最好的是Al₂O₃,酚类相对含量增幅达31.10%。除Fe₂O₃外的三种金属氧化物均降低了生物炭的有序度,添加CaO制备的生物炭具有最无序的炭结构和最高的固相产率。     

Evaluation of various types of Al-MCM-41 materials as catalysts in biomass pyrolysis for the production of bio-fuels and chemicals

MCM-41, is one of the latest members of the mesoporous family of materials. They possess a hexagonal array of uniform mesopores (1.4–10 nm), high surface areas (>1000 m²/g) and moderate acidity. Due to these properties the MCM-41 materials are currently under study in a variety of processes as catalysts or catalyst supports. The objective of this study was to evaluate different types of MCM-41 materials as potential catalysts in the catalytic biomass pyrolysis process. We expected that the very high pore size and the mild acidity of these materials could be beneficial to reformulate the high molecular weight primary molecules from biomass pyrolysis producing useful chemical (and especially phenolic compounds) and lighter bio-oil with less heavy molecules. Three different samples of Al-MCM-41 materials (with different Si/Al ratio) and three metal containing mesoporous samples (Cu–Al-MCM-41, Fe–Al-MCM-41 and Zn–Al-MCM-41) have been synthesised, characterized and tested as catalysts in the biomass catalytic pyrolysis process using a fixed bed pyrolysis combined with a fixed catalytic reactor and two different types of biomass feeds. Compared to conventional (non-catalytic) pyrolysis, it was found that the presence of the MCM-41 material alters significantly the quality of the pyrolysis products. All catalysts were found to increase the amount of phenolic compounds, which are very important in the chemical (adhesives) industry. A low Si/Al ratio was found to have a positive effect on product yields and composition. Fe–Al-MCM-41 and Cu–Al-MCM-41 are the best metal-containing catalysts in terms of phenols production. The presence of the Al-MCM-41 material was also found to decrease the fraction of undesirable oxygenated compounds in the bio-oil produced, which is an indication that the bio-oil produced is more stable.     

碱土金属氧化物基催化剂催化热解生物质研究进展

快速热解是生物质高效转化利用的重要方法之一,然而其目标产物生物油因含氧量高、组分复杂等不足而难以直接利用。通过在热解体系中引入碱土金属氧化物基催化剂,可以将热解产物中的氧元素以CO₂和H₂O等方式脱除,从而实现生物油品质的提升。总结了典型碱土金属氧化物基催化剂对生物质催化热解过程中发生的酮基化、羟醛缩合、开环和侧链断裂反应及机理,讨论了催化剂类型（CaO、MgO、基于碱土金属氧化物的分子筛和活性炭等）、生物质原料、温度、催化剂用量、停留时间、催化方式、催化剂失活等因素对生物油产率与品质的影响,并对生物质催化热解制备高品质生物油及其应用进行了展望。     

生物质油改性方法研究进展

生物质快速裂解液体产物生物油(简称生物质油),具有水含量高、氧含量高、热值低、粘度大、热不稳定和化学不稳定等特性,在一定程度上影响了其广泛应用,因此必须通过精制改善其品质.按生物质快速裂解的反应过程,将提高生物质油品质的方法归纳为三类:第一类(反应前),快速裂解反应前,原料脱水和脱碱金属处理;第二类(反应中),快速裂解反应过程中,生物质油蒸汽不经冷凝直接改质;第三类(反应后),快速裂解反应完成后,采用对收集到的生物质油催化加氢、催化裂解、催化酯化、乳化、添加溶剂或添加抗氧化剂等方法进行改质.     

Study of the potential valorisation of heavy metal contaminated biomass via phytoremediation by fast pyrolysis: Part I. Influence of temperature, biomass species and solid heat carrier on the behaviour of heavy metals

Presently, little or no information of implementing fast pyrolysis for looking into the potential valorisation of heavy metal contaminated biomass is available. Fast pyrolysis of heavy metal contaminated biomass (birch and sunflower), containing high amounts of Cd, Cu, Pb and Zn, resulting from phytoremediation, is investigated. The effect of the pyrolysis temperature (623, 673, 773 and 873 K) and the type of solid heat carrier (sand and fumed silica) on the distribution of the heavy metals in birch and sunflower pyrolysis fractions are studied. The goal of the set-up is “concentrating” heavy metals in the ash/char fraction after thermal treatment, preventing them to be released in the condensable and/or volatile fractions. The knowledge of the behaviour of heavy metals affects directly future applications and valorisation of the pyrolysis products and thus contaminated biomass. They are indispensable for making and selecting the proper thermal conditions for their maximum recovery. In view of the future valorisation of these biomasses, the amounts of the pyrolysis fractions and the calorific values of the obtained liquid pyrolysis products, as a function of the pyrolysis temperature, are determined.     

Catalytic Pyrolysis of Pine Wood Sawdust to Produce Bio-oil: Effect of Temperature and Catalyst Additives

In this work, non-catalytic pyrolysis of Turkish pine (Pinus brutia Ten.) wood sawdust was performed in a fixed-bed reactor at various temperatures to obtain the optimum conditions to achieve a maximum bio-oil yield. The highest yield of bio-oil was obtained about 46 wt% at 550°C for non-catalytic pyrolysis. At the optimum conditions, the effects of different catalyst types (KOH, ZnCl₂, and ZnO) and amount of catalyst (5, 10, 15, and 20 wt%) on the pyrolysis product yields and bio-oil properties were investigated. The presence of catalysts changed the product distribution considerably. Increasing the amount of catalyst led to a decrease in the yield of liquid product, while the gas and char yields increased compared to non-catalytic pyrolysis. The chemical compositions of bio-oil were determined with GC-MS analyses. It was determined that bio-oils contain a large variety of organic compounds, such as furans, aldehydes, ketones, phenols, acids, benzenes, alcohols, alkanes, and polycyclic aromatic hydrocarbons (PAHs). The catalysis by KOH significantly increased the levels of phenols, while it reduced the formation of acids and aldehydes. ZnCl₂ produced bio-oil with high percentages of aldehydes. Moreover, ZnO reduced the proportion of PAH in the bio-oil. These results demonstrated that bio-oils could improve with a catalyst. Therefore, catalyst selection for high bio-oil quality is crucial in industrial applications.     

杉木屑真空热解制备生物油的实验研究

以杉木屑为原料,进行了真空热解制备生物油的实验研究. 考察了体系压力、热解终温、终温保持时间及升温速率等热解参数对生物油产率、生物油组分及其相对含量的影响. 结果表明,热解终温为500℃、体系压力为20 kPa、热解终温保持时间为60 min、升温速率为60℃/min的条件有利于杉木屑真空热解制备生物油的生产,其产率达67%以上. 真空热解过程中,慢速热解可得到较高的生物油产率.     

Deactivating species in the transformation of crude bio-oil with methanol into hydrocarbons on a HZSM-5 catalyst

A study has been carried out by using different techniques (TPO, FTIR, Raman, ¹³C NMR, GC/MS of the coke dissolved in CH₂Cl₂) on the nature of the coke deposited on a HZSM-5 catalyst modified with Ni in the transformation of the crude bio-oil obtained by flash pyrolysis of lignocellulosic biomass (pine sawdust) into hydrocarbons. The reaction system has two steps in-line. In the first one, the components of crude bio-oil derived from the pyrolysis of biomass lignin are polymerized at 400 °C. In the second one, the remaining volatile oxygenates are transformed into hydrocarbons in a fluidized bed catalytic reactor at 450 °C. The reaction has been carried out with different bio-oil/methanol mass ratios in the feed (from 100/0 to 0/100). Co-feeding methanol significantly attenuates coke deposition, and the nature of the coke components varies according to the bio-oil/methanol ratio in the feed. When bio-oil is co-fed, the coke deposited on the catalyst has a significant content of oxygenates and oxo-aromatics and consists of two fractions, identified by temperature programmed oxidation, corresponding to external and internal coke in the zeolite crystals. The fraction of external coke is soluble in CH₂Cl₂, with a high content of oxygenates and oxo-aromatics, and is generated by polymerization of products derived from biomass lignin pyrolysis activated by the zeolite acid sites. The fraction of coke retained within the zeolite crystals is partially insoluble and is formed by several routes: from the intermediates in the transformation of both methanol and bio-oil oxygenates into hydrocarbons; by evolution of the other coke fraction; from the hydrocarbons (with high aromatics content) in the reaction medium.     

Biofuels from waste fish oil pyrolysis: Continuous production in a pilot plant

Fast pyrolysis of waste fish oil was performed in a continuous pyrolysis pilot plant. The experiment was carried out under steady-state conditions in which 10 kg of biomass was added at a feed rate of 3.2 kg h⁻¹. A bio-oil yield of 72-73% was obtained with a controlled reaction temperature of 525 °C. The bio-oil was distilled to obtain purified products with boiling ranges corresponding to light bio-oil and heavy bio-oil. These biofuels were characterized according to their physico-chemical properties, and compared with the Brazilian-fuel specifications for conventional gasoline and diesel fuels. The results show that the fast pyrolysis process represents an alternative technique for the production of biofuels from waste fish oil with characteristics similar to petroleum fuels.     

蒙脱石的催化生物质热解特性

以纤维素和橡树叶为研究对象,探索了蒙脱石催化作用下热解产物的变化规律及机理.结果表明:蒙脱石负载促进纤维素向β-消除路径转化,导致活化能增加、DTG(微商热重分析曲线)峰值温度升高和热解速率降低,而对橡树叶的热解过程影响较小;蒙脱石可催化热解液体的2次裂解,使液体产率降低,气体产率增加,而对固体产物产率的影响较小,其中...     

Simultaneous catalytic esterification of carboxylic acids and acetalisation of aldehydes in a fast pyrolysis bio-oil from mallee biomass

This paper reports the simultaneous catalytic esterification and acetalisation of a bio-oil with methanol using a commercial Amberlyst-70 catalyst at temperatures between 70 and 170 °C. The bio-oil was prepared from the pyrolysis of mallee woody biomass in a fluidised-bed pyrolysis reactor under the fast heating rate conditions. Our results show that the conversion of light organic acids and aldehydes to esters and acetals rises significantly with increasing temperature, reaction time and catalysts loading. However, some acetals (e.g. dimethoxymethane) could decompose at higher operating temperatures (>110 °C) and catalyst loadings (>6 wt.%). The medium and heavy fractions of bio-oil also reacted with methanol to result in increases in their volatility (or decreases in boiling points) when their reactive O-containing functional groups were stabilised. The acid-catalysed reactions between bio-oil and methanol also decreased the coking propensity of the bio-oil reaction products.     

矿物质对生物质热解的影响及其解决方案

通过对一年生和多年生的生物质及其热解油组成的分析,探讨了影响生物质热解油组成及其酸度的重要因素是生物质中的金属盐矿物质,金属盐舍量增加,致使热解油收率降低、酸含量增加。对现有的生物质热解工艺进行了比较和评述,提出了消除金属矿物质影响和含酸少的新型生物质热解工艺。     

Hydro-pyrolysis of lignocellulosic biomass over alumina supported Platinum,Mo<Subscript>2</Subscript>C and WC catalysts

In-line hydro-treatment of bio-oil vapor from fast pyrolysis of lignocellulosic biomass (hydro-pyrolysis of biomass) is studied as a method of upgrading the liquefied bio-oil for a possible precursor to green fuels. The nobel metal (Pt) and non-noble metal catalysts (Mo₂C and WC) were compared at 500 °C and atmospheric pressure which are same as the reaction conditions for fast pyrolysis of biomass. Results indicated that under the pyrolysis conditions, the major components, such as acids and carbonyls, of the fast pyrolysis bio-oil can be completely and partially hydrogenated to form hydrocarbons, an ideal fossil fuel blend, in the hydro-treated bio-oil. The carbide catalysts perform equally well as the Pt catalyst regarding to the aliphatic and aromatic hydrocarbon formation (ca. 60%), showing the feasibility of using the cheap non-noble catalysts for hydro-pyrolysis of biomass.

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Separation of bio-oil by molecular distillation

In this study, KDL5 molecular distillation apparatus manufactured by the UIC Corporation was adopted to separate bio-oil, which came from a bench-scale fluidized-bed fast pyrolysis reactor at a feeding rate of 1 kg/h. A maximum distillate yield of 85% was obtained without obvious coking or polymerization during the molecular distillation process. The effect of distillation temperature on physical and chemical characterization of each bio-oil fraction was investigated. Statistical calculations showed that molecular distillation was successful in the separation of bio-oil. A separation factor was proposed to reflect the ability of isolating the chemicals contained in the bio-oil using molecular distillation.     

生物质快速热解制油试验及流程模拟

使用自主研发的流化床热解反应器对生物质热解制油进行实验研究,通过对不同实验温度450、500、525、550、580、610℃下得到的目标产物进行分析,得到了反应温度对生物油产率的影响规律。实验表明：550℃时,最大液体产率为42.5%（质量）;实验得到的不可冷凝气体的组分以CO、CO₂、CH₄和H₂为主,气相产物产率约为37.7%（质量）。在实验基础上,利用Aspen Plus流程模拟软件,建立了生物质热解制油工艺模拟流程,模拟分析了热解温度对生物油产率的影响,结果表明该模型能准确模拟实际热解过程,具有较好的适用性和可靠性。     

Biofuels from waste fish oil pyrolysis: Chemical composition

In a previous study, waste fish oil was converted into bio-oil by a fast pyrolysis process at 525 °C in a continuous pilot plant reactor with 72-73% yield. The bio-oil was distilled to obtain light bio-oil and heavy bio-oil and these biofuels were characterized in terms of their physico-chemical properties. In this study, the chemical composition of light bio-oil and heavy bio-oil was determined using GC-FID, GC-MS, ¹H and ¹³C NMR techniques. The GC-MS analysis of waste fish oil showed the main composition of fatty acids to be the following: C_16:0 (15.87%), C_18:2 (20.96%), C_18:1 (17.29%), C_20:5 (5.11%), C_20:1 (7.59%), C_22:6 (4.53%), C_22:1 (10.42%) and others. The GC-FID analysis of the light bio-oil showed 482 compounds that were PIONA classified as paraffins (4.48%), iso-paraffins (8.31%), olefins (26.56%), naphthenes (6.07%) and aromatics (16.86%). The heavy bio-oil had a similar chromatographic profile as diesel oil, with a high content of carboxylic acids and olefins. These results are in good agreement with those for the gasoline and diesel oil fractions of petroleum.