【作者】 刘少敏；

【导师】 陈明强；

【作者基本信息】 安徽理工大学 ， 环境工程， 2013， 博士

【摘要】 氢是理想的载能体,是用于燃料电池和内燃机的理想清洁燃料。然而,从化石燃料中提取氢不仅会带来环境污染,而且化石燃料的储备正在消耗殆尽。开发可再生清洁能源一生物质能源,对中国能源结构调整,减少温室气体排放,保护生态环境将发挥巨大作用。然而,生物质的高度分散性和较低的能量密度决定了它的高运输成本和经济可行性,而通过生物质快速裂解制得的生物油代表了一种具有较高能量密度的原料,它可以较容易分散制取,然后集中制取氢气,以生物油为原料制取氢气为生物油的利用提供了一条新的途径。本论文对生物油水蒸汽催化重整制氢进行了催化剂的选择、制备,对生物油的热解特性,热动力学进行了分析,对生物油模型物及生物油进行了催化重整制氢的工艺条件、基本规律、催化机理的研究。以廉价Ni过渡金属为催化剂的活性组分,载体主体为海泡石,添加助剂MgO或Mo03,用浸渍法制备一系列Ni基催化剂Ni/Sepiolite, Ni/MgO-Sepiolite, Ni/Mo-Sepiolite, Ni/Mo-MgO-Sepiolite,获得催化剂制备的最佳条件,并对催化剂进行XRD、XPS、BET、SEM、TG/DTG表征。在空气气氛下采用热重分析法对固定床反应器中生物油水溶性组分的热解特性进行对比研究,利用Achar-Brindley-Sharp-Wendworth(Achar)微分法和Coats-Redfern(Coats)积分法结合的方式进行动力学分析,计算了挥发和热分解的活化能、反应级数和动力学参数,确定了机理函数并建立了热解动力学模型。结果表明生物油水溶性组分的热解可分为三个阶段,即轻组分挥发、重组分裂解和焦炭燃烧,热解段生物油水溶性组分活化能较挥发段的活化能降低了很多；挥发段采用一级反应模型来模拟生物油水溶性组分的热分解,而热解段采用二级模型表示热解反应；第一阶段挥发段反应级数近似为一级,第二阶段热解段反应级数近似为二级,两阶段的相关系数表明反应级数具有较好的线性相关度。选择乙酸、丙三醇、苯酚、糠醛作为生物油模型物,以改性海泡石Ni/Mo-MgO-Sepiolite作为催化剂,进行乙酸、丙三醇、苯酚、糠醛水蒸汽重整制氢,获得制氢的基本规律,优化了反应条件,比较了各种催化剂的催化性能。选择生物油为原料,在固定床反应器中进行水蒸汽催化重整制氢,考察了反应温度、进料的水碳摩尔比、进料空速、反应器催化长度对生物油水蒸汽催化重整制氢的影响。用浸渍法制备了镍、钼改性的海泡石催化剂,考察了改性海泡石催化活性对重整制氢的影响,海泡石酸化前后的催化效应,结果表明：用酸化后的海泡石改性的催化剂催化重整得到的氢产率67.5%,而用未酸化的海泡石改性后的催化剂催化重整得到的氢产率仅46.2%。选择乙酸、丙酮、丙三醇、苯酚、糠醛配成的混合物作为生物油模型物,用吉布斯自由能最小化法对其水蒸汽催化重整制氢过程进行热力学分析,考察了反应温度、碳水比(C/H20)、进料流量对平衡时气体产物的影响,并建立了数学模型。对改性海泡石的催化活性进行了研究,酸化后的海泡石经过镍钼改性后,提高了原海泡石品位,使之更具有储存和助催化功能,比原海泡石具有更强的催化性能。对水蒸汽催化重整制氢过程中催化剂催化效应进行分析,推断改性海泡石催化机理,指出催化剂失活的主要原因是催化剂载体孔道及活性金属表面被累积的焦炭堵塞所致。更多还原

【Abstract】 Hydrogen is an ideal energy carrier that can be used as an essential clean fuel form. However, hydrogen production from fossil fuels will not only bring about environmental pollution, but also requires a complete consumption of the raw materials of the fossil fuel. As a consequence, the development of renewable clean energy-biomass energy will play a large role in China’s energy structure adjustment in order to reduce greenhouse gas emissions and protect the ecological environment. Because dispersion level and energy density would determine the transport cost and economic feasibility of one particular fuel form, bio-oil that is well-known for its fast pyrolysis has represented one type of promising new energy forms with easy dispersion and high energy density.This paper provided a brief introduction of bio-oil pyrolysis characteristics, carried out kinetics analysis with different reaction conditions considered explicitly based on the basic law of the catalytic steam reforming, and revealed catalytic mechanism in steam reforming of bio-oil for hydrogen production.When the Ni transition metal ingredients are divided according to the active group of inexpensive catalyst, the main body of the carrier is sepiolite, and the carrier assistant ingredient consists of MgO and MoO3.A series of Ni base catalyst Ni/Sepiolite was prepared with the impregnation method. Ni/MgO-Sepiolite, Ni/Mo-Sepiolite and Ni/Mo-MgO-Sepiolite are applied to obtain the optimum reaction conditions of catalyst preparation, with XRD, XPS, BET, SEM and TG/DTG attributed to the catalyst.The pyrolysis behaviors and kinetics of the water-soluble components of bio-oil were studied by thermogravimetric (TG) analysis. The curves of TG and corresponding DTA were analyzed in the oxygen atmosphere within a fixed bed reactor. Based on the experimental data, activation energies, reaction order and kinetic parameters were calculated using the Achar-Brindley-Sharp-Wendworth differential method and the Coats-Redfern integral method. Also, potential involving mechanisms were explored with thermal kinetic equations ultimately obtained. The results showed that the pyrolysis process of water-soluble components of bio-oil can be divided into three stages, including the evaporation stage of volatile fractions, the decomposition stage of heavy fractions and the char combustion stage. To activate energy forms, the volatilization dynamic is higher than bio-oil obtained directly from the decomposition stage. The first stage was expressed as first order reaction whereas the second stage was expressed as second order reaction. The kinetic reaction order was characterized as first order reaction of the first stage, followed by the second order reaction of the second stage. The correlation coefficient of these two stages showed that the reactions were of well conformity.The mixtures of acetic acid, acetone, glycerol urfural and phenol were selected and dubbed as bio-oil model compounds. Studies on the acetic acid, glycerol, phenol, furol and mixed model steam reforming for hydrogen production were carried out within a fixed bed reactor with modified Ni/Mo-MgO-Sepiolite catalyst to optimize reaction conditions and to compare catalytic properties of various catalysts.Hydrogen was produced during the catalytic steam reforming process of bio-oil within a fixed bed reactor. Sepiolite catalysts modified with nickel (Ni) and molybdenum (Mo) were prepared using the precipitation method. Influential parameters such as temperature, catalyst, steam to carbon ratio (H2O/C), the feeding space velocity (feeding rate) and reforming reaction length were quantified. The results of this experiment showed that the yield with the acidified sepiolite catalyst was67.5%. In contrast, the yield with the non-acidified sepiolite catalyst was only46.2%.The mixtures of acetic acid, glycerol, urfural and phenol were selected and dubbed as bio-oil model compounds. The thermodynamic analysis was carried out to understand the steam catalytic reforming hydrogen production process with the Gibbs energy reduced the least. The effect of reaction temperature, C/H2O and the feeding rate on gasous components of the molecular balance was investigated, with involving mathematical model successfully established.The catalytic activity of modified sepiolite, the effect of catalyst on the steam reforming and the associated catalytic mechanisms were analyzed based on the experimental results. Some impurities could be removed from sepiolite after a nickel-molybdenum-modification on sepiolite to improve the original sepiolite grade, to ensure a better storage and catalysis performance, and to have a stronger catalytic performance compared to the circumstances where only original sepiolite was applied. The main reason for catalyst deactivation was due to coke plugging. Both the channels of the carrier and the active metal surfaces were likely to be blocked by the coke.更多还原