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.     

Evolution of gaseous products from biomass pyrolysis in the presence of phosphoric acid

Slow pyrolysis experiments of China fir (Cunninghamia lanceolata) wood were performed in a vertical tubular furnace at various heating rates. The raw material was pretreated by impregnation with phosphoric acid solutions of various concentrations for given times. The evolution of the gaseous products CO, CO₂, H₂ and CH₄ was analyzed online by using gas spectrometry to investigate the effect of phosphoric acid on the pyrolytic gaseous products of biomass. The addition of phosphoric acid was shown to significantly reduce the pyrolysis temperature necessary for the production of CO, CO₂ and H₂ gases, and the pyrolysis variables exerted an influence on the amount of the gases released. Moreover, phosphoric acid appreciably depressed the CO, CO₂ and CH₄ production, and promoted H₂, especially when a higher heating rate was employed. This suggested that phosphoric acid catalyzed both the primary thermal decomposition of biopolymers and the secondary reactions that took place among the pyrolytic vapor products.     

Simulation of the fast pyrolysis of Tunisian biomass feedstocks for bio-fuel production

An optimized model is developed for the production of bio-fuels from biomass using a SuperPro Designer tool. Four types of Tunisian biomass feedstocks including date palm rachis, olive stones, vine stems and almond shells were selected for the fast pyrolysis process simulation. Simulation tests were performed at different temperatures ranging from 450 to 650 °C, and residence times ranging from 0.1 to 10 s and the products yield were determined. The obtained results indicate that a temperature of 575 °C and 0.25 s vapor residence time are the optimum parameters to maximize the bio-oil yield. Comparison between the different feedstocks indicates that a higher bio-oil fraction was obtained from the date palm rachis and vine stem. However, the difference between the samples is not significant and further investigations on the bio-oil properties are requested to select the suitable biomass for bio-oil production in Tunisia.     

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.     

Screening acidic zeolites for catalytic fast pyrolysis of biomass and its components

Zeolites have been shown to effectively promote cracking reactions during pyrolysis resulting in highly deoxygenated and hydrocarbon-rich compounds and stable pyrolysis oil product. Py/GC-MS was employed to study the catalytic fast pyrolysis of lignocellulosic biomass samples comprising oak, corn cob, corn stover, and switchgrass, as well as the fractional components of biomass, i.e., cellulose, hemicellulose, and lignin. Quantitative values of condensable vapors and relative compositions of the pyrolytic products including non-condensable gases (NCG's) and solid residues are presented to show how reaction products are affected by catalyst choice. While all catalysts decreased the oxygen-containing products in the condensable vapors, H-ZSM-5 was most effective at producing aromatic hydrocarbons from the pyrolytic vapors. We demonstrated how the Si/Al ratio of the catalysts plays a role in the deoxygenation of the vapors towards the pathway to aromatic hydrocarbons.     

Novel gaseous transient species:generation and characterization

Due to special properties of transient species,such as short-lived,unstable,reactive,and even explo-sive,the generation and subsequent characterization is a great challenge for experimental chemists. In our laboratory,systematic researches have been carried out to investigate novel transient species:reactive halogen species(RHS) ,short-lived free radicals,and metastable pseudohalogen compounds,based on the successive technical improvements on the HeI Photoelectron spectroscopy(PES) . In this review,the topic mainly focuses on innovative methods of generating novel transient species,and subsequent geometric and electronic structure characterizations of these species combined with quantum chemical calculations.     

酸预处理对生物质热裂解规律影响的实验研究

在自制的热裂解机理实验台上进行了不同酸处理对稻壳以及白松的热裂解影响实验研究。经过盐酸浸泡后,稻壳中的金属离子含量明显降低;经盐酸洗涤后的稻壳热裂解焦油产量升高,由原始物料时的41.74%增加到7%盐酸洗涤后的52.88%,而气体和焦炭产量相应降低,并且随着盐酸浓度的增加,对应的趋势更加明显。酸洗涤后稻壳热裂解气体产物主要由CO和CO₂组成,其产量相比原样都有所降低;不同种类的酸对生物质热裂解规律的影响存在差异,盐酸因其去离子效果最好而对生物质热裂解产物分布影响最强;对白松原样以及酸洗后白松的微观结构进行了电镜分析,结果发现,硫酸对白松的微观结构产生了明显的影响。     

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     

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.     

Continuous fast pyrolysis of biomass at high temperature in a fluidized bed reactor

In order to perform biomass pyrolysis a continuous fluidized bed reactor (bench scale unit) has been assembled. The influence of experimental conditions such as heating-up time and optimum particle diameter is presented. By feeding the biomass (almond shells) directly into the bubbling bed, pyrolysis has been performed at temperatures ranging from 730° to 930°C at constant feed rate (44 g/h). Remarkable increase of H₂ in the product gas is observed when steam rather than an inert carrier such as nitrogen is used thus confirming the potential of this approach.The support of ENEA (Italian Agency for Renewable Energies) is gratefully acknowledged.     

Hollow ZSM-5 encapsulated with single Ga-atoms for the catalytic fast pyrolysis of biomass waste

The development of efficient metal-zeolite bifunctional catalysts for catalytic fast pyrolysis(CFP) of biomass waste is highly desirable for bioenergy and renewable biofuel production.However,conventional metal-loaded zeolites often suffer from metal sintering during pyrolysis and are thus inactivated.In this study,single-site Ga-functionalized hollow ZSM-5(GaO_x@HS-Z5) was synthesized via an impregnationdissolution-recrystallization strategy without H₂ reduction.The Ga atom...     

生物质快速热解油水相溶液超声乳化特性

使用生物油水相溶液与0# 柴油乳化,筛选了四种常用乳化剂和一种助乳化剂进行复配乳化实验,考察了复配乳化剂型号、乳化剂用量、超声作用时间对乳化效果的影响。结果表明,六种乳化液超过30d不破乳,与0# 柴油相比,密度和热值相差不大,含水量3%以下,黏度增大约40%,pH值降低一半。因素分析法表明,水相溶液与柴油质量比和不同的水相溶液对乳化效果影响较大。探讨了乳化机理,认为生物油水相溶液中水、醛、酸、酮等极性组分化合物稳定地被乳化剂包裹在W/O型乳化液液滴中,生物油水相溶液中少量的乙酸乙酯、芳香类化合物等则增溶于非离子乳化剂胶束中。热力学分析表明,超声乳化作用比静置作用具有更大的熵增,乳化液更趋于稳定平衡状态。     

Fast pyrolysis of biomass

The development of viable fast pyrolysis processes for biomass and other carbonaceous feedstocks will offer significant advantages over conventional pyrolysis, flash pyrolysis and gasification processes with respect to product yield quality and flexibility. Fast pyrolysis is defined and related to other biomass thermochemical conversion processes in some detail. Brief references are made to corresponding coal, hydrocarbon and oil conversion research and development. Proposed mechanisms and chemical pathways are reviewed, potential products. product upgrading and product applications are identified. Fast pyrolysis research is reviewed on both the fundamental bench-scale level and the applied process development level.     

Microwave pyrolysis of biomass

Because of the inherent moisture and large particle size of wood used in the Forest Products Industry, there has been regional interest in exploring the feasibility of processing wood, cellulose, and other such related materials using microwave dielectric-loss heating. A research project was undertaken in the late 1970’s to determine the important variables altering the rate of microwave-induced reactions of this polymeric material. The research presented dates from that period. Reaction proudcts were measured in detail and some optimization of the coupling of the microwave energy to the large particles was studied. Results and principal findings at the time of the study are presented in this paper as well as two papers by the author in the cited literature. Suggestions for future directions for this type of study are also presented.     

Gasification and catalytic conversion of biomass by flash pyrolysis

The influence of the water content, the gasification atmosphere and the action of inorganic catalysts on biomass pyrolysis is discussed. The pyrolysis conditions are characterized by a heating rate of a wood sample of 250–300°C/s and a residence time of the gas in the hot zone of the reactor of less than 1 s. Volumes, carbon contents, weights and energy balances at different temperatures (600–1000°C) are tabulated. The total volume of pyrolysis gas and the yields increase with increasing temperature and water content. This increase is especially due to the production of hydrogen. A large part of the gasified hydrogen comes from water. Water that has not been driven off from green wood is more gasifiable than water that is re-added or from the atmosphere. Three types of catalysts were tested: alumina, aluminosilicate material and nickel-supported catalyst. The results show that it is possible to control the distribution of gas species by controlling the water content of the biomass and selecting the catalyst on which the wood is pyrolysed. A nickel catalyst on mordenite seems to be very efficient in directing pyrolysis gas production towards synthesis gas.     

生物质焦制备条件对其燃烧反应特性的影响

在热重分析仪上,研究了生物质焦的制备条件对其燃烧反应特性的影响。生物质焦由闪速裂解技术制得,裂解温度为 748 K、773 K和823 K;原料含水质量分数为0、7.0%和11.3%。研究发现,生物质焦中挥发性物质的质量分数和H/C质量比随裂解温度的增加而降低,其燃烧反应性随裂解温度的增加而降低;与高裂解温度条件下制得的生物质焦相比,低裂解温度条件下制得的生物质焦具有较高的反应活化能和对燃烧温度更敏感。原料含水量对生物质焦的燃烧反应特性影响很小;但对高裂解温度条件下制得的生物质焦中的挥发性组分含量有较大的影响。简化的生物质焦本征燃烧反应幂函数动力学模型可以很好地描述其燃烧行为。     

Introduction to pyrolysis of biomass

The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicelluloses and lignin and their minor components including extractives and inorganic materials. Pyrolysis of these materials proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products.Pyrolysis cellulose at lower temperatures below 300° C involves reduction in molecular weight, evolution of water, carbon dioxide and carbon monoxide and formation of char. On heating at higher temperature 300–500° C, the molecule is rapidly depolymerized to anhydroglucose units that further reacts to provide a XXXX pyrolyXXXXA: still higher temperatures, the anhydrosugar compounds undergo fussion, dehydration disproportionation and decarboxylation reaction to provide a mixture of low molecular weight gaseous and volatile produces. The composition of these produces and mechanism and kinetics of their production are reported.     

催化热解生物质制取富氢气体的研究

在实验室自制的固定床反应器上, 考察了秸秆和锯屑的热解行为, 研究了热解产物分布特别是富氢气体的体积分数和产率, 着重研究了（5种金属氧化物和2种碳酸盐催化剂）的催化效果。结果表明,温度从500 ℃提高到850 ℃, 秸秆和锯屑的热解气产率分别从29.0%提高到40.6%, 35.0％提高到46.5%, 而对应的富氢气体的体积分数分别从41.2％提高到48.2%, 40.6％提高到47.0%；在5种金属氧化物中，Cr2O3显示了最好的催化效果，在750 ℃时对应的热解气产率与不使用催化剂相比提高了10％，富氢气体的体积分数提高了13％；催化剂（CaCO3和Na2CO3）占生物质的质量分数对热解气和富氢气体产率有明显的影响，当质量分数从0增加到30％时， 热解气和富氢气体产率增加较明显，而后其值的增加可以忽略， 因此推荐使用的催化剂质量分数为30％。     

生物质热解液化与美拉德反应

对生物质热解液化和美拉德反应进行了介绍,指出美拉德反应不仅存在于生物质热解液化过程中,而且通过引入适量氨等调控措施,可以促进美拉德反应有选择性地生成吡嗪类杂环化合物等高值化学品,然后再通过分级冷凝将生物油分为化工生物油和燃料生物油,前者用于分离提取高值化学品,后者用于锅炉和窑炉的燃料.引入美拉德反应后,生物质热解液化技术经济性将会得到根本性的改善.