Ni原位催化生物质及其典型组分快速热解定向制备富氢合成气

The fast pyrolysis of biomass and its typical components (cellulosic, lignocellulosic, and lignin) was conducted over a pressured falling tubular reactor. The nickel crystallites, which was in situ formed by H2 reduction of nickel(II) during the pyrolysis of catalyst precursor-impregnated biomass, could be acted as catalysts for accelerating tar decomposition and increasing H2 yield. In addition, the production of H2-rich syngas for F-T synthesis could be enhanced by the strategy of in situ CO2 adsorption by CaO.The effects of different reaction parameters, such as material ratio, feeding rate, steam consumption, the dosage of CaO and Ni, reaction temperature and pressure, on the pyrolysis products were investigated.The H2 concentration or H2/CO molar ratio was increased by optimizing of the reaction conditions. The kinetic and product evolution during the pyrolysis of biomass and its typical components was studied by a thermogravimetric-mass analyzer. Moreover, the comparison of the difference was conducted between the pyrolysis products of individual biomass components and those of their mixtures. In this way, the pyrolysis interaction mechanism of the biomass typical components could be revealed. The project is important for the exploration of the common pyrolysis characteristics of biomass with different compositions. It has important significance to the highly efficient conversion of biomass, the optimization of energy structure, the reduction of environmental pollution, and the realization of economic sustainable development.

采用加压落管反应器实现生物质及其典型组分（纤维素、半纤维素和木质素）快速热解；利用生物质浸渍催化剂前驱体Ni(II)，经热解时生成的氢还原成零价Ni，作为催化剂促进焦油分解和提高氢产率；同时利用CaO吸附分离CO2，促进氢生成，从而定向制备富氢合成气（可用于费-托合成）。考察不同参数（原料配比、进料速率、水蒸汽消耗量、CaO和Ni用量、反应温度和压力）对热解产物的影响及其规律；通过优化反应条件，提高H2含量或H2/CO比。利用热重-质谱研究热解动力学及产物析出规律，结合生物质典型组分单独热解和共热解时产物差异对比分析，明确生物质典型组分相互作用机制。本项目的研究有助于揭示不同组成生物质热解时的共性规律，对于实现生物质高效清洁转化，优化能源结构，减少环境污染，以及实现经济可持续发展具有重要意义。

利用催化快速热解技术将生物质定向转化为富氢合成气，对于实现生物质高效清洁转化以及减少环境污染具有重要意义。本研究侧重对Ni原位催化生物质及其典型组分制备富氢合成气进行了研究，主要包括：.1）利用TG/MS研究考察了生物质及其典型组分（纤维素、半纤维素及木质素）的失重行为，并实时测定热解产物析出规律。.结果表明，生物质热解产生的氢主要源于CO、CO2、CH4和H2O彼此间的二次反应。加CaO作为CO2吸收剂可提高生物质制氢产率。木屑热解析氢量可由组分加和模型预测析氢量。.2）进一步对生物质热解过程中Ni0纳米晶形成及其催化作用机制作了初步探索，并通过多种分析手段对样品进行了详细表征。.结果表明，在热解温度400~500oC范围内形成Ni0纳米晶。热解时，Nin+（Ni2+ 和Ni3+）被还原成Ni0纳米晶。Ni0纳米粒子在生物质热解过程中可催化水-气转换制氢及焦油精制制氢反应，从而提高氢收率。.3）利用落管反应器研究生物质气化制备富氢合成气过程。考察了不同因素对产物分布的影响及其规律，揭示了CaO催化及吸附CO2强化制氢作用机制。.结果表明，CaO可催化焦油分解反应，并吸附CO2，提高H2收率。气化温度升高也有利于提高H2收率，但超过700oC后，CaO对CO2的吸附能力显著下降。适当提高H2O/C比及反应压力有利于提高H2收率。最佳工艺条件为：气化温度=600-700oC，CaO/C摩尔比 =1，H2O/C摩尔比 =1，此时，氢产率接近60.1 vol.%。.4） 进一步研究了不同含量Ni生物质典型组分气化制氢过程及其作用机制。.结果表明，生物质典型组分热解时其产物分布与其分子结构及所含基团密切相关。Ni催化有利于提高生物质典型组分热解氢产率，其中木质素热解氢产率升高最明显。不同生物质典型组分中，以Ni催化纤维素热解制氢最为有效。