Effect of Acid, Steam Explosion, and Size Reduction Pretreatments on Bio-oil Production from Sweetgum, Switchgrass, and Corn Stover

Bio-oil produced from biomass by fast pyrolysis has the potential to be a valuable substitute for fossil fuels. In a recent work on pinewood, we found that pretreatment alters the structure and chemical composition of biomass, which influence fast pyrolysis. In this study, we evaluated dilute acid, steam explosion, and size reduction pretreatments on sweetgum, switchgrass, and corn stover feedstocks. Bio-oils were produced from untreated and pretreated feedstocks in an auger reactor at 450?°C. The bio-oil??s physical properties of pH, water content, acid value, density, and viscosity were measured. The chemical characteristics of the bio-oils were determined by gas chromatography?Cmass spectrometry. The results showed that bio-oil yield and composition were influenced by the pretreatment method and feedstock type. Bio-oil yields of 52, 33, and 35?wt% were obtained from medium-sized (0.68?C1.532?mm) untreated sweetgum, switchgrass, and corn stover, respectively, which were higher than the yields from other sizes. Bio-oil yields of 56, 46, and 51?wt% were obtained from 1?% H₂SO₄-treated medium-sized sweetgum, switchgrass, and corn stover, respectively, which were higher than the yields from untreated and steam explosion treatments.     

Inorganics distribution in bio oils and char produced by biomass fast pyrolysis: The key role of aerosols

Fast pyrolysis of biomass is a promising process for the preparation of bio-oil dedicated to energy production. Inorganic species originally present in biomass are known to induce problems such as bio-oil instability or deposits and fouling. However the mechanisms of inorganic species release during biomass pyrolysis into the raw bio-oils still remain unclear. The present work focuses on the determination of inorganic distribution in the products from wheat straw and beech wood fast pyrolysis performed in a fluidized bed. More specifically, the bio-oils are fractionated by using a series of condensers. The results show that more than 60 wt.% of the inorganic content of the overall bio-oil is contained in the aerosols. Several possible interpretations for this observation are discussed. It is likely that the inorganics are transported within the aerosols droplets and solid particles which are recovered in the bio-oils, either by mechano-chemical processes, or by entrainment of submicron intermediate liquid compound formed in the first steps of biomass fast pyrolysis.     

Pretreatment of poplar wood for fast pyrolysis: rate of cation removal

It is well known that the presence of alkaline cations in biomass affect the mechanism of thermal decomposition during fast pyrolysis causing primarily fragmentation of the monomers making up the natural polymer chains rather than the predominant depolymerization that occurs in their absence. As a result, liquid products (bio-oil) of quite different compositions can be obtained, and these bio-oils may be used for quite different purposes. A considerable amount of research has been carried out on the changes in mechanism occurring due to the presence and absence of these cations during fast pyrolysis and the compositional changes occurring in the bio-oil product as a result. However, if removal of such cations is to be practised as an industrial process, it would be desirable to have some information on the rates of the exchange step and the degree of removal of a particular cation that can be economically achieved. The present work describes a preliminary study of the rates of removal of the indigenous alkaline cations in a poplar wood (potassium and calcium mainly) by an ion exchange process using a dilute acid. The exchange process is rapid and potassium is more easily removed than calcium. It is also shown that hot water washing alone is able to remove a major amount of the alkaline cations from wood. The deionized wood can be used as the feed for a fast pyrolysis process for the thermal conversion of cellulose and hemicellulose to anhydrosugars for use in synthesis, or for conversion to fermentable sugars in good yield.     

CaO伴随生物质热裂解制油同时脱氧的小型流化床实验研究

在小型流化床反应器中,对CaO伴随生物质快速热裂解制油过程中的直接脱氧效果进行了研究。当反应温度为520℃、载气流量8000L/h时,在纯白松粉末和CaO伴随条件下分别制出了生物油样品。实验结果表明,当采用纯白松与CaO/白松质量比分别为1、2、4时,生物油样品中有机组分的含氧量依次为39.38%、39.15%、39.04%和32.29%;在CaO/白松质量比为4时,生物油有机组分含氧量的下降幅度达18.0%（相对变化）。GC-MS分析结果表明,CaO加入后左旋葡聚糖和甲酸、乙酸等高含氧量物质相对含量明显下降,证实了CaO伴随生物质热裂解过程中“富氧中间体”固氧路径的存在;与此同时,糠醛类等主要来源于脱水反应的产物相对含量上升,说明CaO的加入也促进了脱水反应的发生。     

Aromatics and phenols from catalytic pyrolysis of Douglas fir pellets in microwave with ZSM-5 as a catalyst

Microwave assisted catalytic pyrolysis was investigated to convert Douglas fir pellets to bio-oils by a ZSM-5 zeolite catalyst. A central composite experimental design (CCD) was used to optimize the catalytic pyrolysis process. The effects of reaction time, temperature and catalyst to biomass ratio on the bio-oil, syngas, and biochar yields were determined. GC/MS analysis results showed that the bio-oil contained a series of important and useful chemical compounds. Phenols, guaiacols, and aromatic hydrocarbons were the most abundant compounds which were about 50–82% in bio-oil depending on the pyrolysis conditions. Comparison between the bio-oils from microwave pyrolysis with and without catalyst showed that the catalyst increased the content of aromatic hydrocarbons and phenols. A reaction pathway was proposed for microwave assisted catalyst pyrolysis of Douglas fir pellets.     

HZSM-5上生物质催化裂解的近期研究进展

概述了近期的HZSM-5对生物质和生物油催化裂解的研究进展,重点介绍了催化剂的应用、生物油提质的方法和反应机理.     

固体酸改质生物油的研究

利用乙酸和乙醇生成乙酸乙酯的酯化反应为模型反应，筛选得到催化活性最好的固体酸催化剂40％SiO2/TiO2SO42－。 在一定的反应条件下，添加固体酸催化剂和溶剂，生物油的品质得到提高，热值提高了50.7％，运动黏度降低到原来的10％，密度降低了22.6％。生物油改质前后的GC MS分析表明，固体酸可以将生物油中含有的有机羧酸转化为酯类，如甲酸酯、乙酸酯等，使生物油中的羧酸组分发生了催化酯化反应，改善了生物油的品质，生物油物理化学性能得到明显的提高。3A分子筛对生物油的脱水作用不显著，对酸性、密度、黏度等方面影响较小。     

Physical and chemical properties of bio-oils from microwave pyrolysis of corn stover

This study was aimed to understand the physical and chemical properties of pyrolytic bio-oils produced from microwave pyrolysis of corn stover regarding their potential use as gas turbine and home heating fuels. The ash content, solids content, pH, heating value, minerals, elemental ratio, moisture content, and viscosity of the bio-oils were determined. The water content was approx 15.2 wt%, solids content 0.22 wt%, alkali metal content 12 parts per million, dynamic viscosity 185 mPa.s at 40 degrees C, and gross high heating value 17.5 MJ/kg for a typical bio-oil produced. Our aging tests showed that the viscosity and water content increased and phase separation occurred during the storage at different temperatures. Adding methanol and/or ethanol to the bio-oils reduced the viscosity and slowed down the increase in viscosity and water content during the storage. Blending of methanol or ethanol with the bio-oils may be a simple and cost-effective approach to making the pyrolytic bio-oils into a stable gas turbine or home heating fuels.     

Microwave-assisted pyrolysis of biomass: Catalysts to improve product selectivity

This study was intended to evaluate the effects of catalysts on product selectivity of microwave-assisted pyrolysis of corn stover and aspen wood. Metal oxides, salts, and acids including K₂Cr₂O₇, Al₂O₃, KAc, H₃BO₃, Na₂HPO₄, MgCl₂, AlCl₃, CoCl₂, and ZnCl₂ were pre-mixed with corn stover or aspen wood pellets prior to pyrolysis using microwave heating. The thermal process produced three product fractions, namely bio-oil, gas, and charcoal. The effects of the catalysts on the fractional yields were studied. KAc, Al₂O₃, MgCl₂, H₃BO₃, and Na₂HPO₄ were found to increase the bio-oil yield by either suppressing charcoal yield or gas yield or both. These catalysts may function as a microwave absorbent to speed up heating or participate in so-called “in situ upgrading” of pyrolytic vapors during the microwave-assisted pyrolysis of biomass. GC–MS analysis of the bio-oils found that chloride salts promoted a few reactions while suppressing most of the other reactions observed for the control samples. At 8 g MgCl₂/100 biomass level, the GC–MS total ion chromatograms of the bio-oils from the treated corn stover or aspen show only one major furfural peak accounting for about 80% of the area under the spectrum. We conclude that some catalysts improve bio-oil yields, and chloride salts in particular simplify the chemical compositions of the resultant bio-oils and therefore improve the product selectivity of the pyrolysis process.     

Comparison of pretreatment methods on the enzymatic saccharification of aspen wood

Five different chemical pretreatments, using dilute sulfuric acid, sodium hydroxide, hydrogen peroxide and sodium hydroxide, peroxymonosulfate, and acetic acid, were applied to aspen thermomechanical fibers. The pretreated fibers were submitted to enzymatic hydrolysis and the liberated glucose was monitored. High glucose concentrations were observed for the peroxymonosulfate and the acetic acid pretreated samples. Glucose concentrations greater than 25 g/L were obtained in these cases. This corresponds to conversions on the order of 90% of the pretreated substrate glucose content.     

Parallels between slow pyrolysis of Estonian oil shale and forest biomass residues

Different types of forest residual biomass, including pine wood, pine bark and spruce needles, and Estonian Kukersite oil shale, were parallelly subjected to the slow pyrolysis in similar conditions. A Fischer assay, modeling industrial semi-coking retorts, was used. Both the yield and the composition of liquid, gaseous and solid products of pyrolysis were determined. FTIR-spectroscopic and chromatographic methods were used to study products group and individual composition. Common and specific features in biomass and oil shale semi-coking have been described. In comparison with oil shale, the biomass yielded less oil and more gas. Specifically large amounts of reaction water and carbon dioxide were obtained in biomass pyrolysis resulting in formation of significantly deoxygenated liquid and solid products. Bio-oils can be distinguished by the solubility in conventional solvents. Kukersite shale oil and the benzene-soluble fractions of different bio-oils were characterized by similar group composition.     

Production of bio-oil via fast pyrolysis of agricultural residues from cassava plantations in a fluidised-bed reactor with a hot vapour filtration unit

This article reports experimental results on fast pyrolysis of agricultural residues from cassava plantations, namely cassava rhizome (CR) and cassava stalk (CS), in a fluidised-bed fast pyrolysis reactor unit incorporated with a hot vapour filter. The objective of this research was to investigate the effects of reaction temperatures, biomass particle size and the use of simple hot vapour filtration on pyrolysis product yields and properties. Results showed that the optimum pyrolysis temperatures for CR and CS were 475 °C and 469 °C, which gave maximum bio-oil yields of 69.1 wt% and 61.4 wt% on dry biomass basis, respectively. The optimum particle size for bio-oil production in this study was 250–425 μm. The use of the hot filter led to a reduction of 6–7 wt% of bio-oil yield. Nevertheless, the filtered bio-oils appeared to have a better quality in terms of initial viscosity, solids content, ash content and stability.     

Optimization of process for the production of bio-oil from eucalyptus wood

The pyrolysis of eucalyptus wood was carried out in a batch reactor to optimize the yield of bio-oil.Effect of various parameters like feed(particle) size,temperature,presence of catalyst and heating rate on the yield of bio-oil was investigated.The optimum conditions for high yield of bio-oil are for the particle size 2 mm~5 mm(average l/d=12.84/2.03 mm) at 450 ℃ in high heating rate.The reaction kinetics and the quality of bio-oil produced are independent of the presence of different catalysts like mordenite,kaoline clay,fly ash and silica alumina.The physical properties like odour,colour,PH,viscosity,heating value were determined.The FT-IR analysis of bio-oil indicates the presence of different functional groups such as monomeric alcohol,phenol,ketones,aldehydes,carboxylic acid,amines,and nitro compounds.The composition of the bio-oil at different conditions was analyzed using GC-MS and found that the components are temperature dependent but independent of catalysts used.     

Production of fungicidal oil and activated carbon from pistachio shell

The main objective of this study was to evaluate the feasibility of pistachio shell as a biomass feedstock for the production of fungicidal oil and a precursor for the production of activated carbon by physical activation. For this purpose, pistachio shell was pyrolyzed in a fixed bed reactor at the different temperatures (300-600 °C). The pyrolysis products were identified as gas, bio-oil, aqueous solution and char. The product distribution from pyrolysis process did not significantly change when the pyrolysis temperature was above 300 °C. The pyrolysis gas product had low calorific value since it contained the high proportion of carbon oxides. Because of their high oxygen content, the bio-oils were found not to be used as a fuel. Thus, the bio-oil was tested again four different types of fungi (pathogenetic, wood decaying and saprophyting). It was shown fungicidal activity again all tested fungi at the concentration of 10-50 mg ml⁻¹. The pyrolysis char was evaluated as a precursor for the production of activated carbon. The surface area and micropore volume of the activated carbon produced from the char by CO₂ activation at 900 °C were found to be 708 m² g⁻¹ and 0.280 cm³ g⁻¹, respectively.     

碱／碱土金属催化松木屑快速热解机制

研究碱／碱土金属（AAEM）对生物质的热解及其热解产物组成的影响规律,可为生物质热解特性研究和热解产物的高效利用提供重要的理论依据。本文以松木屑为原料,将原样进行酸洗,并对酸洗样分别用K、Ca、Na和Mg氯化盐溶液浸渍,在500℃和Ar气氛下对各样品进行快速热解,考察了4种金属离子对松木屑热解产物组成分布的影响规律;通过热重分析考察了各个样品的热解特性;通过对热解生物油的气相色谱／质谱（GC／MS）分析考察了快速热解的焦油成分。研究结果表明：AAEM对松木屑有明显的催化作用,AAEM的存在能够提高热解气体和固体的产率,降低热解焦油的产率;AAEM能够降低热解温度,使热解更加容易进行;快速热解的焦油成分主要有酚类、酮类、醛类、芳烃、醇类、脱水糖类、呋喃类以及酸类,AAEM显著影响焦油产物组成,特别是呋喃类和芳烃的含量会有所增加。本文为优化生物质的热解条件与提高热解生物油品质具有重要意义。     

Thermochemical Liquefaction as a Cleaner and Efficient Route for Valuing Pinewood Residues from Forest Fires

Biomass thermochemical liquefaction is a chemical process with multifunctional bio-oil as its main product. Under this process, the complex structure of lignocellulosic components can be hydrolysed into smaller molecules at atmospheric pressure. This work demonstrates that the liquefaction of burned pinewood from forest fires delivers similar conversion rates into bio-oil as non-burned wood does. The bio-oils from four burned biomass fractions (heartwood, sapwood, branches, and bark) showed lower moisture content and higher HHV (ranging between 32.96 and 35.85 MJ/kg) than the initial biomasses. The increased HHV resulted from the loss of oxygen, whereas the carbon and hydrogen mass fractions increased. The highest conversion of bark and heartwood was achieved after 60 min of liquefaction. Sapwood, pinewood, and branches reached a slightly higher conversion, with yields about 8% greater, but with longer liquefaction time resulting in higher energy consumption. Additionally, the van Krevelen diagram indicated that the produced bio-oils were closer and chemically more compatible (in terms of hydrogen and oxygen content) to the hydrocarbon fuels than the initial biomass counterparts. In addition, bio-oil from burned pinewood was shown to be a viable alternative biofuel for heavy industrial applications. Overall, biomass from forest fires can be used for the liquefaction process without compromising its efficiency and performance. By doing so, it recovers part of the lost value caused by wildfires, mitigating their negative effects.     

Scale-up of microwave heating process for the production of bio-oil from sewage sludge

A pilot-scale microwave heating apparatus was constructed for the production of bio-oil from sewage sludge, and the effects of important microwave processing parameters and chemical additives on the quality and yield of bio-oils were investigated. It was found that bio-oil was mainly formed at the pyrolysis temperature range of 200–400 °C. A higher heating rate (faster pyrolysis) not only increased the yield of bio-oil, but also improved the quality of bio-oil according to the elemental composition and calorific values. The maximum bio-oil yield was 30.4% of organic fraction, obtained from the pyrolysis of original sewage sludge at microwave radiation power of 8.8 kW and final pyrolysis temperature of 500 °C. All of five simple additives (KOH, H₂SO₄, H₃BO₃, ZnCl₂, and FeSO₄) reduced the bio-oil yield, but the composition and property of bio-oil varied with the additive types greatly. KOH, H₂SO₄, H₃BO₃ and FeSO₄ were found to improve the quality of bio-oils remarkably according to the calorific value, density, viscosity and carbon content of bio-oils, but ZnCl₂ treatment went against that. GC–MS analysis of the bio-oils showed that, alkali treatment promoted the formation of alkanes and monoaromatics, while acid treatment favored the formation of heterocyclics, ketones, alcohols and nitriles. Compared with sulfate slat FeSO₄, chloride salt ZnCl₂ was a better catalyst for selective catalytic pyrolysis of sewage sludge. The addition of ZnCl₂ only promoted the formation reactions of a few kinds of nitriles and ketones remarkably. It is technologically feasible to produce bio-oil form microwave-induced pyrolysis of sewage sludge by optimizing pyrolysis conditions and selecting appropriate additives.     

A Review of Characteristics of Bio-Oils and Their Utilization as Additives of Asphalts

Transforming waste biomass materials into bio-oils in order to partially substitute petroleum asphalt can reduce environmental pollution and fossil energy consumption and has economic benefits. The characteristics of bio-oils and their utilization as additives of asphalts are the focus of this review. First, physicochemical properties of various bio-oils are characterized. Then, conventional, rheological, and chemical properties of bio-oil modified asphalt binders are synthetically reviewed, as well as road performance of bio-oil modified asphalt mixtures. Finally, performance optimization is discussed for bio-asphalt binders and mixtures. This review indicates that bio-oils are highly complex materials that contain various compounds. Moreover, bio-oils are source-depending materials for which its properties vary with different sources. Most bio-oils have a favorable stimulus upon the low temperature performance of asphalt binders and mixtures but exhibit a negative impact on their high-temperature performance. Moreover, a large amount of oxygen element, oxygen-comprising functional groups, and light components in plant-based bio-oils result in higher sensitivity to ageing of bio-oil modified asphalts. In order to increase the performance of bio-asphalts, most research has been limited to adding additive agents to bio-asphalts; therefore, more reasonable optimization methods need to be proposed. Furthermore, upcoming exploration is also needed to identify reasonable evaluation indicators of bio-oils, modification mechanisms of bio-asphalts, and long-term performance tracking in field applications of bio-asphalts during pavement service life.     

碱处理HZSM-5分子筛在线催化提质生物油

采用NaOH溶液对HZSM-5分子筛进行碱处理,利用XRD、SEM、BET、Py-FTIR四种方法表征改性HZSM-5分子筛,对生物原油有机相、未改性HZSM-5制得生物油有机相与改性HZSM-5制得生物油有机相进行理化特性及成分分析,研究了碱处理HZSM-5分子筛对生物油有机相产物的影响;对使用了120 min的三种失活催化剂进行了热重分析,并对焦炭峰面积进行了积分计算。结果表明,经过碱处理后的HZSM-5分子筛保留了典型的MFI拓扑结构,形成了一定数量的介孔;同时,经碱处理1 h的HZSM-5分子筛催化制得的生物油有机相产物的产率有所增加且理化特性得到提高,其产物中烃类物质的含量显著增加,达到了37.67%,且以单环芳香烃为主;同时改性HZSM-5分子筛对生物油有机相中的酸、醛及酮类物质均有较好的脱除效果,有效地降低了生物油的腐蚀性并提升了生物油的稳定性,热值达到了35.32 MJ/kg;经1 h碱处理的HZSM-5分子筛的总结焦量明显降低。     

Chemical composition of bio-oil produced by co-pyrolysis of biopolymer/polypropylene mixtures with K2CO3 and ZnCl2 addition

The chemical composition of liquid products of cellulose and lignin co-pyrolysis with polypropylene at 450 °C with and without the potassium carbonate or zinc chloride as an catalyst was investigated. The yield of liquid products of pyrolysis was in the range of 26–45 wt% and their form was liquid or semi-solid highly depending on the composition of sample and pyrolysis conditions. The potassium carbonate and zinc chloride addition to blends has also influenced the range of samples decomposition as well as the chemical composition of resulted bio-oils. All bio-oils from biopolymer and polypropylene mixtures were three-phase (water, oil and solid). While zinc chloride acted as catalyst, all bio-oils obtained from biopolymer and polypropylene mixtures were yellow liquids with well-separated water and oil phases. All analyses proved that the structure and quality of bio-oil strongly depends on both the composition of the blend and the presence of the additive. The FT-IR and GC–MS analyses of oils showed that oxygen functionalities and hydrocarbons contents highly depend on the composition of biomass/polypropylene mixture. Results confirmed the significant removal and/or transformation of oxygen containing organic compounds, i.e. levoglucosan, 1,6-anhydro-β-d-glucofuranose and phenol derivatives due to the zinc chloride presence during pyrolysis process. All analyses showed that zinc chloride as catalyst was generally much more effective for removal of hydroxyl and methoxy groups than was potassium carbonate. It was demonstrated in this study that catalysts used in present work lead to the increased char yield and improved the fuel quality of bio-oil.