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.     

Valorisation of bio-oil resulting from fast pyrolysis of wood

Bio-oil resulting from the pyrolysis of lignocellulose is a complex mixture of polar low molecular mass oxygenated compounds of various functionalities and non-polar high molecular mass lignin derivatives. Several approaches to the upgrading of bio-oil are currently in progress. This study investigates the valorisation of crude bio-oil using physical and chemical methods. The effects of methanol addition on some properties of the bio-oil are investigated. Stable bio-oil/diesel oil emulsions are produced by the addition of surfactants with a hydrophilic-lipophilic balance value of 5–6. An alternative approach towards the upgrading of bio-oil is the hydrotreatment of the water-soluble fraction of bio-oil. Two-stage hydroprocessing with noble-metal catalysts Ru/C and Pt/C increases the intrinsic hydrogen content of the water-soluble fraction. The results show that the thermally unstable components including sugars, ketones and aldehydes are readily converted to diols and alcohols at pressures of 5 MPa. These observations can be explained by a set of reaction pathways for the compounds identified.     

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass

Hydrogen production from the aqueous phase derived from fast pyrolysis of biomass was carried out by catalytic steam reforming in a fluidized bed reactor. The effects of reaction conditions such as reaction temperature, steam-to-carbon ratio (S/C) and weight hourly space velocity of the aqueous phase (WHSV) on the results of hydrogen yield, potential hydrogen yield and carbon selectivity of product gases were investigated. The effect of reaction temperature on the carbon deposition on catalyst was also studied. The hydrogen yield of 64.6%, potential hydrogen yield of 77.6% and the carbon selectivity for product gases of 84.3% can be obtained at the optimized conditions of reaction temperature 800 °C, S/C 10 and WHSV 1.0 h⁻¹.     

Application of catalysts for obtaining 1,6-anhydrosaccharides from cellulose and wood by fast pyrolysis

The present work is devoted to the estimation of the effect of phosphoric acid and Fe³⁺ ions on the 1,6-anhydrosaccharides levoglucosan (LG) and levoglucosenone (LGone) contents in volatile products obtained from wood and microcrystalline cellulose by analytical pyrolysis. It was shown that the LG and LGone contents can be influenced by the pre-treatment. Iron was introduced into the biomass either by soaking in iron(III) sulfate solution alone or in the presence of ammonium, a treatment, in the course of which iron oxihydroxide is formed. It was demonstrated that a previous decationization of wood plays an important role for the subsequent results of Fe³⁺ ion treatment.The 1,6-anhydrosaccharides content in volatile products and the ratio of LG/LGone is governed by the phosphoric acid concentration. The same is true for cellulose soaked by iron sulfate: at higher concentration, the LGone content increases and the LG/LGone ratio decreases. The mechanism of the action of iron ions depends on the iron species formed upon the cellulose-containing raw materials pre-treatment procedures with iron sulfate. Upon pyrolysis, the adsorbed iron sulfate increases the amount of both LG and LGone in volatile products through the acidic catalysis mechanism owing to sulfate anions activity. The pre-treatment by the ion-exchange method could be considered as an efficient technique for obtaining the biooil containing levoglucosan in high content: 44.8% from cellulose and 27.3% from wood. The results are interpreted based on the quantitative evaluation of the pyrograms and the ESR spectra of the treated wood.     

Pyrolysis oil from fast pyrolysis of maize stalk

Maize stalk was fast pyrolysed at temperatures between 420 °C and 580 °C in a fluidized-bed, and the main product of pyrolysis oil was obtained. The experimental results showed that the highest pyrolysis oil yield of 66 wt.% was obtained at 500 °C for maize stalk. Chemical composition of the pyrolysis oil acquired was analyzed by GC–MS and its heat value, stability, miscibility and corrosion characteristics were determined. These results showed that the pyrolysis oil could be directly used as a fuel oil for combustion in a boiler or a furnace without any upgrading. Alternatively, the fuel could be refined to be used by vehicles.     

Product distribution from fast pyrolysis of glucose-based carbohydrates

Carbohydrates are the major constituents of biomass. With the growing interest in utilizing bio-oil obtained from fast pyrolysis of biomass for fuels and chemicals, understanding the carbohydrate pyrolysis behavior has gained particular importance. The chemical composition of the bio-oil is an important consideration for its upstream and/or downstream processing. Though the classification of pyrolysis products into overall tar, char and gaseous fraction has evolved as a standard; detailed knowledge of the chemical constituents that determine the quality of bio-oil has received little attention. Furthermore, the speciation arising from primary and secondary reactions has been rarely distinguished. In this study the product distribution arising from the primary reactions during 500 °C fast pyrolysis of several mono-, di- and polysaccharides is studied with the help of micro-pyrolyzer. The study suggests that levoglucosan and the low molecular weight compounds are formed through competitive pyrolysis reactions rather than sequential pyrolysis reactions. It is also shown that the orientation or the position of glycosidic linkages does not significantly influence the product distribution except with 1,6-linked polysaccharide, which showed considerably less formation of levoglucosan than other polysaccharides.     

A study of the properties of a composite asphalt binder using liquid products of wood fast pyrolysis

The results of a study of the adhesive properties of a composite asphalt binder modified with pyrolytic lignin—a water-insoluble fraction of liquid products of fast pyrolysis of wood—are presented. It is shown that 10 wt % pyrolytic lignin increases the adhesive strength of the composite asphalt binder and the obtained samples of modified asphalt concrete correspond to the requirements of GOST (State Standard) 9128–84.     

Detoxification of brominated pyrolysis oils

The development of an innovative technology for the pyrolytic conversion of brominated phenols in a reductive medium aimed at product recovery for commercial use is discussed in this paper. Brominated phenols are toxic products, which contaminate pyrolysis oil of wastes from electronic and electrical equipment (WEEE). The pyrolysis experiments were carried out with 2,6-dibromophenol, tetrabromobisphenol A, WEEE pyrolysis oil and polypropylene or polyethylene in encapsulated ampoules under inert atmosphere in quasi-isothermal conditions (300–400 °C) with a different residence time (10–30 min). Optimal conditions were found to be the use of polypropylene at 350 °C with a residence time of 20 min. The main pyrolysis products were identified as HBr and phenol. A radical debromination mechanism for the pyrolytic destruction of brominated phenols is suggested.     

Fusion-like behaviour of wood pyrolysis

The results of an experimental study of the melting rates of rods of ice, paraffin and Rilsan (polyamide 11) pressed against a spinning hot disk are reported. The observations are similar to those made with wood rods, the “fusion temperature” of which has been found close to 739 K. These results are in agreement with a theoretical study of the competition between the kinetics of thermal wood decomposition and heat transfer resistances inside and outside the wood. A second conclusion is that because of the heat fluxes that can be transferred in most of the experimental devices, it seems almost impossible to raise wood to temperatures greater than about 800 K; the direct experimental determination of wood pyrolysis reaction rate constants at temperatures above 800 K then appears impossible.     

Online upgrading of organic vapors from the fast pyrolysis of biomass

The online upgrading process that combined the fast pyrolysis of biomass and catalytic cracking of bio-oil was developed to produce a high quality liquid product from the biomass. The installation consisted of a fluidized bed reactor for pyrolysis and a packed bed reactor for upgrading. The proper pyrolysis processing conditions with a temperature of 500℃ and a flow rate of 4m3·h-1 were determined in advance. Under such conditions, the effects of temperature and weight hourly space velocity (WHSV) on both the liquid yields and the oil qualities of the online catalytic cracking process were investigated. The results showed that such a combined process had the superiority of increasing the liquid yield and improving the product quality over the separate processes. Furthermore, when the temperature was 500℃, with a WHSV of 3h-1, the liquid yield reached the maximum and the oxygenic compounds also decreased obviously.     

加拿大合成原油瓦斯油裂解反应规律与产物生成机理

利用小型固定流化床实验装置研究了加拿大合成原油重瓦斯油(HGO)和轻瓦斯油(LGO)的催化裂解性能和热裂解性能。HGO和LGO催化裂解总低碳烯烃(乙烯+丙烯+丁烯)产率在660℃附近达到最大值,分别为33.8%和35.6%。HGO和LGO热裂解反应程度很大,700℃的转化率分别为66.7%和76.3%。HGO热裂解总低碳烯烃的产率在680℃达到最大值27.9%。通过对比分析催化裂解与热裂解气体产物产率的比值发现,催化剂的加入促进了乙烯和液化气的生成,同时抑制了甲烷和乙烷的生成。研究结果揭示了小分子烃类的生成机理,甲烷和乙烷主要是自由基反应的产物,乙烯和液化气是自由基反应和正碳离子反应的共同产物。     

Pyrolysis characteristics of cellulose derived from moso bamboo and poplar

To compare with pyrolysis characteristics of cellulose from moso bamboo and poplar, samples were pyrolyzed with different heating rates through thermogravimetric analysis (TG). The kinetics was calculated by Kissinger–Akahira–Sunose method. The results showed that pyrolysis process of moso bamboo and poplar fiber included three stages, and the main pyrolysis occurred in the second step. Moso bamboo fiber had a higher start temperature, a lower end temperature and a more mass loss at each heating rate in the main pyrolysis stage. With increase in heating rate, the temperature corresponding to the maximum of mass loss increased and the DTG curve shifted to higher temperature. The reaction rates varied at different heating rates. The activation energy of cellulose from moso bamboo was lower than poplar cellulose, indicating cellulose of moso bamboo was easier to be pyrolyzed. The results from this research will provide guidance to thermal conversion of moso bamboo and poplar.

     

Thermogravimetric study of the pyrolysis of waste wood

A thermogravimetric study of the pyrolysis of three different types of waste wood (forest wood, old furniture and used pallets) is carried out in a TGA equipment using dynamic and isothermal techniques. Isothermal runs were carried out at two temperature levels, one between 225° and 325°C (low range) and the other, between 700° and 900°C (high range). Results show a good agreement between the kinetic parameters obtained from either dynamic or isothermal techniques. It must be remarked that the own chemical composition of each type of wood together with the compounds added to the wood for each application, play a fundamental role in the kinetic behavior of their thermal decomposition.     

Sorption of arsenic, cadmium, and lead by chars produced from fast pyrolysis of wood and bark during bio-oil production

Bio-char by-products from fast wood/bark pyrolyses, were investigated as adsorbents for the removal of the toxic metals (As(3+), Cd(2+), Pb(2+)) from water. Oak bark, pine bark, oak wood, and pine wood chars were obtained from fast pyrolysis at 400 and 450 degrees C in an auger-fed reactor and characterized. A commercial activated carbon was also investigated for comparison. Chars were sieved (>600, 600-250, 250-177, 177-149, and <149 microm) and the particle size fraction from 600 to 250 microm was used without further modification for all studies unless otherwise stated. Sorption studies were performed at different temperatures, pHs, and solid to liquid ratios in the batch mode. Maximum adsorption occurred over a pH range 3-4 for arsenic and 4-5 for lead and cadmium. Kinetic studies yielded an optimum equilibrium time of 24 h with an adsorbent dose of 10 g/L and concentration approximately 100 mg/L for lead and cadmium. Sorption isotherms studies were conducted in broad concentration ranges (1-1000 ppb for arsenic, 1x10(-5)-5x10(-3) M for lead and cadmium). Oak bark out-performed the other chars and nearly mimicked Calgon F-400 adsorption for lead and cadmium. In an aqueous lead solution with initial concentration of 4.8x10(-4) M, both oak bark and Calgon F-400 (10 g/L) removed nearly 100% of the heavy metal. Oak bark (10 g/L) also removed about 70% of arsenic and 50% of cadmium from aqueous solutions. Varying temperatures (e.g., 5, 25, and 40 degrees C) were used to determine the effect of temperatures. The equilibrium data were modeled with the help of Langmuir and Freundlich equations. Overall, the data are well fitted with both the models, with a slight advantage for Langmuir model. The oak bark char's ability to remove Pb(II) and Cd(II) is remarkable when considered in terms of the amount of metal adsorbed per unit surface area (0.5157 mg/m(2) for Pb(II) and 0.213 mg/m(2) for Cd(II) versus that of commercial activated carbon.     

玉米芯快速热解油特性研究

利用层析法对玉米芯快速热解油进行分析。结果表明,裂解温度对热解油产率及其族馏分构成的影响很大。通过气相色谱(GC)分析表明,脂肪族馏分碳数分布主要在C12~34,在烷烃碳数分布上,脂肪族馏分与柴油相当。并利用傅里叶红外光谱(FT-IR)、核磁共振氢谱(1H-NMR)分析了600℃下得到的热解油特征,表明玉米芯快速热解油作为燃料和高品位化学品原料来源具有潜在的发展前景。     

SANS analysis of the microstructural evolution during the aging of pyrolysis oils from biomass

In this paper, we report for the first time a microstructural characterization of pyrolysis oils obtained from biomass. Bio crude oils (BCOs) are good candidates as substitutes for mineral oils as fuels. By using small-angle neutron scattering (SANS), we show that BCOs are nanostructured fluids constituted by a complex continuous phase and nanoparticles mainly formed by the association of units of pyrolytic lignins. The aggregation of these units during the time produces branched structures with fractal dimension D(f) between 1.4 and 1.5, which are responsible for BCO aging. SANS results fully support the recently formulated thermal ejection theory, accounting for the mechanism of formation of the lignin fraction in oils obtained from fast pyrolysis of biomass.     

Bio-oil from fast pyrolysis of rice husk: Yields and related properties and improvement of the pyrolysis system

Rice husk was fast pyrolysed at temperatures between 420 °C and 540 °C in a fluidized bed, and the main product of bio-oil is obtained. The experimental result shows that the highest bio-oil yield of 56 wt% was obtained at 465 °C for rice husk. Chemical composition of bio-oil acquired was analyzed by GC–MS and its heat value, stability, miscibility and corrosion characteristics were determined. These results showed that bio-oil obtained can be directly used as a fuel oil for combustion in a boiler or a furnace without any upgrading. Alternatively, the fuel can be refined to be used by vehicles. Furthermore, the energy performance of the pyrolysis process was analyzed.     

生物质热解油气化试验研究

生物质是一种环境友好可再生资源，可以通过多种途径转化为液体燃料。生物质热解液化即是在缺氧状态下对生物质进行快速加热，然后再对热解产物进行快速冷凝，最后获得一种称为生物油的液体燃料的技术。该技术以及生物油的特点主要有：热解液化温度为500℃，远低于生物质热解气化所     

Catalytic fast pyrolysis of jatropha wastes

In this work, the decomposition behaviors of jatropha wastes (husk, seed shell and branch) have been examined in order to get desired liquid organic compounds, but not undesired inorganic compounds such as CO, CO₂, water and coke. The jatropha wastes exhibit a stepwise degradation pathway which has a slight difference in between samples before and after milling. In the preliminary pyrolysis using quartz reactor and H-ZSM-5(30) catalyst, the liquid products selectivity was seed shell > blanch > husk > seed shell (no catalyst). In the absence of catalyst, the Py-GC/MS analyses for pyrolysis of jatropha wastes show a range of aromatic hydrocarbons, phenols, alcohols and ketones, acids and esters, ethers and aldehydes. Aromatics are predominantly formed above 90% of area percentage by use of catalyst. Of aromatic compounds, xylenes, naphthalenes and toluene are mainly produced. The product selectivity is dependent on both the size of the catalyst pores and the nature of the active sites and one candidate is H-ZSM-5 and the other candidate is β-zeolite. The reaction pathway involves dehydrogenation and dehydroaromatization of aliphatic oxygenates such as alkylcyclohexanol and higher carboxylic acids to form phenol derivatives, which undergo hydrodeoxygenation into toluene and xylenes, followed by dehydroaromatization to give naphthalenes.     

煤直接液化残渣快速热解半焦特性的研究

在惰性气氛N2条件下,利用小型固定床进行了煤直接液化残渣快速热解半焦特性的研究,并结合热天平残渣半焦等温热失重进行分析。考察了终态温度、停留时间等外部操作条件以及颗粒大小对液化残渣快速热解半焦特性的影响。结果表明,半焦产率随着终态温度提高而降低,焦质变脆,石墨化程度增强,气化反应性减弱;随着反应停留时间的延长,热解产物半焦收率降低,但焦样中孔的数目增多;颗粒大小也影响着半焦的产率,在较大颗粒大小分布范围内,随着颗粒大小的减小,半焦产率随之减少。