【作者】 徐勇；

【导师】 李全新；

【作者基本信息】 中国科学技术大学 ， 可再生洁净能源， 2013， 博士

【摘要】 生物质是一种资源丰富、环境友好的可再生能源,通过热化学的方法可以将生物质转化为高品位的液体燃料或者高附加值的化学品。生物质也可以通过气化或者生物油重整的方法制备合成气,这些合成气不但可以直接用作燃料,亦可以作为化工合成的初级原料。尽管生物质能的开发和利用受到了越来越多的关注,但是目前就如何有效地利用生物质能还存在很多问题,例如能量利用效率的提高等。本论文所研究的工作主要围绕以下几个方面展开：1.生物油水蒸汽重整制富氢合成气的研究制备了用于生物油水蒸汽重整制备合成气的碳纳米纤维负载的镍催化剂(Ni/CNFs),研究了重整温度以及S/C比对生物油的转化率,氢气的产率,合成气的组分的影响。结果表明：重整温度以及S/C都能有效地促进生物油的转化。在本文研究的范围内(重整温度：350-550℃,S/C：2-7),生物油最大转化率和氢气最大产率分别为94.7%和92.1%。合成气中,氢气的体积百分比约为69%,二氧化碳的体积百分比约为26%,并伴随少量的一氧化碳及其微量的甲烷生成。2.生物质炭用于生物油重整合成气组分调整的研究研究了利用生物质碳催化调整生物油重整合成气组分的过程。目的是利用生物质炭与生物油重整合成气中的二氧化碳反应以实现降低合成气中二氧化碳含量和增加一氧化碳含量,使得调整后的合成气中各组分含量达到适合传统甲醇合成的要求。考察了催化剂用量,调整温度以及进气流速对调整效果的影响。以二氧化碳转化率,一氧化碳产率和调整后合成气中C02/CO体积比以及各组分体积含量用来评价调整效果。实验结果表明,在普通催化调整下,温度为800℃时,二氧化碳转化率达到了71.1%,一氧化碳产率为0.88,C02/CO从调整之前的6.33降到0.28,调整后的合成气组分也达到合成甲醇的基本要求。为了进一步弄清调整的过程,本文还利用模拟气研究了调整过程的基元反应步骤,探讨了调整过程二氧化碳转化和一氧化碳生成的两个主要反应通道,即C02+C→CO和C02+H2→CO+H20.本文还研究了活性炭,稻壳生物质炭和锯木屑生物质炭用于富二氧化碳合成气的调整过程,证明了生物质炭中的固定碳部分和活性炭一样可以用于富二氧化碳合成气的调整,并且不受生物质炭种类的影响。另外本文还探讨了电流促进的催化调整过程,结果表明在电流存在的条件下可以高效地促进调整效果,在电流为4A,调整为600℃时,二氧化碳转化率达到了约82%,C02/CO下降到约为0.11：而当温度进一步上升到800℃时,二氧化碳几乎完全转化。3.调整前后生物油重整合成气用于合成甲醇和二甲醚本文为了体现合成气调整效果对液体燃料合成的影响,将模拟的调整前后生物油重整合成气用于合成甲醇和二甲醚。实验结果表明：在甲醇合成中,利用调整前合成气为原料时,最高碳转化率和甲醇时空产率分别为12%和每千克催化剂每小时0.44千克甲醇：经过调整后,碳转化率最高达24%,最高甲醇的时空产率为每千克催化剂每小时1.32千克甲醇。在二甲醚合成中,最高碳转化率从调整前的15.1%增加到调整后的84.8%,最高二甲醚产率从调整前的12.7%提高到60.1%。这种利用生物质炭的调整方法为从生物质制取甲醇等液体燃料提供了一个潜在的有效途径。更多还原

【Abstract】 Biomass is a rich, environmentally friendly and renewable resource which can be converted to high-quality liquid fuels or high value-added chemicals using thermochemical means. Bio-syngas can also be produced from biomass gasification and bio-oil reforming. The development and application of biomass renewable energy is receiving great attention. However, there are still some problems for the utilization of biomass energy, especially, how to increase the efficiency to make biomass energy become the complement of petroleum. The main points of present work were focused on the items as follows:1. Studies on hydrogen-rich bio-syngas production from bio-oil steam reforming.A carbon nanofibers supported Ni catalyst was prepared for hydrogen production from bio-oil steam reforming. The effects of reforming temperature and S/C on bio-oil conversion, hydrogen yield and gas compositions were investigated. Results show that the increasing temperature and S/C can significantly promoted the bio-oil conversion. During our investigated range (the temperature ranges from350℃to550℃, and the S/C ranges from2to7), the maximum bio-oil conversion and hydrogen yield reached about94.7%and92.1%respectively. The main contents in the syngas were hydrogen and carbon dioxide, reaching about a volume fraction of69%and26%. Besides, a small amount of carbon monoxide and a trace of methane were detected in the bio-syngas.2. Studies on the process of bio-syngas conditioning using biomass charThe present work proposed a new method of CO2-rich bio-syngas conditioning by using biomass char. The work aims to decrease the content of CO2and increase the content of CO in the conditioned syngas for producing liquid fuels through the reaction of biomass char and the excess CO2in the unconditioned syngas. The effects of catalyst/char (the mass ratio of catalyst and char), temperature and gas flow were investigated in the process of CO2-rich bio-syngas conditioning. The CO2conversion, CO yield, CO2/CO ratio and the gas compositions of the conditioned syngas were employed for evaluating the performance of conditioning. Results show that CO2conversion and CO yield reached about71.1%and0.88respectively at800℃, the CO2/CO ratio decreased from6.33to0.28, and the gas compositions of the conditioned syngas were suitable for conventional liquid fuels synthesis from syngas. To make clear the process of conditioning, the present work was also studied the two main paths (i.e. CO2+C=CO and CO2+H2=CO+H2O) by using model gases of CO2and CO2/H2. Furthermore, the activated carbon (AR), husk char and sawdust char were used for the conditioning of CO2-rich syngas, indicating that biomass char as well as activated carbon can be used for the conditioning. In addition, the results show the current can greatly improve the performance of conditioning in terms of CO2conversion and CO yield. At4A and600℃, the CO2conversion reaches about82%, the CO2/CO ratio drops to about0.11, when further increased the temperature to600℃, CO2was almost completely converted.3. Methanol and dimethyl ether synthesis from the unconditioned and conditioned bio-syngasTo certify the effects of the present conditioning, two model syngases corresponding to the unconditioned and the conditioned bio-syngas were used for methanol and dimethyl ether (DME) synthesis. Results show that, for methanol synthesis from the unconditioned bio-syngas during our investigated ranges, the maximum carbon conversion and space time yield of methanol are12%and0.44kg/(kgcatalyst h), and increase to23.9%and1.32kg/(kgcatalyst h) after conditioning. Similarly, for DME synthesis from the unconditioned syngas, the maximum carbon conversion and DME yield were15.1%and12.7%, which increased to84.8%and60.1%respectively from the conditioned syngas.更多还原