生物油临氧水蒸汽催化重整制氢机理研究

Hydrogen production via reforming of bio-oil is characteristic of low reaction temperature, short process flow and extensive renewable biomass resources. We propose a process called catalytic steam reforming of bio-oil under oxidative conditions for hydrogen production aimed at solving the key problems associated with reforming reactions such as catalyst sintering, coking and process instability. Low cost catalysts with high activity, selectivity and stability are to be prepared employing clay modified with rare earth metals as carriers. Exploring activation process of tar and oxygen and concentration，time and space distribution of carbonic transition species on catalyst surfaces, illustrating the rules governing catalysis role, dynamic conversion among gaseous molecules and species transfer process by the combination of modern instrument with in-situ FTIR and synchronization photo-ionization analysis, thus mastering the mechanisms of hydrogen production via catalytic steam reforming process under oxidative conditions on molecular level. The influence mechanism of catalyst channel characteristics on hydrogen production via catalytic steam reforming process and cooperation mechanism between each component of bio-oil in hydrogen production process are to be studied By SEM，XPS，AFM and GC/MS methods combined with the model compound in bio-oil, such as Acetic acid, ethanol. In addition, mass transfer-chemical reaction kinetics models are to be established. The basic rules for hydrogen production via catalytic steam reforming process under oxidative conditions might be obtained after this study. The research results of the project can afford the basic data and theoretical basis for hydrogen production from bio-oil.

生物油重整制氢具有反应温度低、流程短、原料广泛且可再生等特点，但反应过程中面临催化剂烧结、结焦和稳定性差等关键难题，本项目提出生物油临氧水蒸汽催化重整制氢方法。采用稀土改性黏土矿为载体，制备出高活性、高选择性和稳定性催化剂；通过原位红外、同步辐射光电离等现代仪器分析技术组合运用探索生物油、氧在催化剂表面活化过程，催化剂表面生成涉碳中间物种浓度及时空分布,并揭示重整反应过程中催化剂、气相分子之间动态转化、物质迁移过程规律,从分子反应水平上掌握生物油临氧水蒸汽催化重整制氢反应机理。采用SEM、XPS、AFM、GC/MS等方法结合生物油模型物（乙酸、乙醇）研究催化剂孔道结构特征对生物油制氢的影响机制和制氢过程中生物油各组份间的协同机制；构建传质-化学反应动力学模型，掌握生物油临氧水蒸汽催化重整制氢的基本规律。本项目可为生物油制氢提供基础数据和理论依据。

生物油催化重整制氢可以提高生物质能利用效率。本项目针对生物油重整制氢中催化剂的烧结和结焦这一关键难题，选用改性的天然黏土矿物-凹凸棒石（ATP）和海泡石（SEP）作为载体，负载Ni基活性组分，制备出高活性、高选择性和稳定性催化剂：Ni-Cu/SEP、Ni-Zn/ATP、Ni/10Mg-ATP以及Ni-Cu/10Ca-ATP等。采用N2吸附脱附、XRD、SEM/TEM、XPS、FTIR、H2-TPR、NH3-TPD以及H2-TPD等分析测试手段对催化剂进行分析，结果证明SEP和ATP作为重整催化剂载体表现出了极强的水热稳定性，催化剂中合金（Ni-Cu和Ni-Zn合金）的形成、碱土金属元素（Mg、Ca）的引入以及活性金属高分散度和强金属-载体相互作用可以有效提升催化剂的活性和稳定性。其中Ni/10Mg-ATP拥有最高的活性金属表面积（0.69 m2/gcat.）和最高的金属分散度（20.2%）；双金属催化剂中Ni-Zn/ATP表现出了最强的金属-载体相互作用；Ni1Cu0.25/SEP在还原活化过程中形成了NiCu合金。在700℃、S/C=1.5、GHSV=19200~19400h-1、乙醇催化重整制氢中，Ni/10Mg-ATP催化剂表现出了100%乙醇转化率和96.7%的H2产率；在600℃、W/G=9、GHSV= 9619 h-1、甘油重整制氢中Ni-Zn/ATP表现出了最高的稳定性；在650℃、S/C=1、WHSV=3.2h-1、苯酚-乙醇重整制氢中Ni1Cu0.25/SEP表现出了最高的碳转化率（83.5%）和H2产率（67.5%）。并阐明了生物油催化重整制氢的反应机理。另外，将这四中催化剂应用于生物乙醇临氧重整制氢中，在T=500℃、乙醇/H2O/O2/N2摩尔比为1:3:0.25:5.0条件下，Ni-Cu/10Ca-ATP表现出了100%的乙醇转化率和84%的H2产率以最高的稳定性。同时，对反应后的催化剂进行系列XRD、TG-DTG、TPO-MS和HRTEM-EDS表征分析，发现Ni/10Mg-ATP表现了极低的积炭形成速率（6.1mgC•(gcat.•h)-1）、Ni1Cu0.25/SEP和Ni-Zn/ATP重整反应后保持基本不变的晶粒尺寸。构建了反应动力学模型，初步掌握了生物油临氧重整制氢的基本规律，为进一步深化研究提供了基础数据和技术基础。