生物质焦油催化重整制氢研究

发布时间：2018-04-23 14:56

  本文选题：生物质焦油 + 重整　； 参考：《大连理工大学》2015年硕士论文

【摘要】：生物质焦油是生物质在热解气化过程中产生的一种粘稠、成分复杂、含氧量高、具有刺激性气味的黑色副产物。焦油的存在不仅影响设备正常运行,而且会对环境和人体健康造成严重危害,进而影响生物质热解气化技术的产业化发展。催化法是高效去除生物质焦油的重要手段,传统的催化法虽然能够有效分解焦油组分,但是因其存在的焦油转化率低、催化剂抗积碳性能差、失活快及氢产率低等问题,限制了其在热解气化领域的广泛应用。针对如何提高焦油的去除效率及解决催化剂易积碳失活等问题,本研究提出了利用镍基催化剂进行生物质焦油催化重整制氢的方法。通过热重分析法研究生物质焦油热解和燃烧过程的动力学特性,Py-GC/MS分析产物分布规律；制备高效、稳定的泡沫陶瓷镍基催化剂；改变实验反应条件,揭示获得最大产氢率的最佳工况条件；通过部分氧化方法实现催化剂原位再生,保证催化剂对焦油的长效催化。本文开展研究工作具体如下：(1)利用热重分析法研究了生物质焦油在不同升温速率下的热化学过程。研究发现,生物质焦油热解失重过程可以分为三个阶段：挥发阶段,一次热解阶段和二次热解阶段。在不同升温速率下,热重曲线具有类似的趋势,随着升温速率的增加,TG和DTG曲线向高温区移动,焦油热解温度升高。生物质焦油热解动力学符合一级动力学反应,根据阿伦尼乌斯公式计算热解区动力学参数可知,一次热解反应的活化能为33.48-50.27kJ/mol,二次热解反应的活化能为39.18-44.20 kJ/mol。生物质焦油燃烧失重规律与热解过程类似,在高温区燃烧过程有明显的失重,燃烧阶段的活化能为79.77-124.25kJ/mol,远大于热解过程。Py-GC/MS分析结果表明,在不同热解温度下,焦油热解产物都主要以芳香族类和酮类物质为主,并且随着热解温度的升高,酮类物质含量明显增多,芳香族化合物明显减少。(2)以泡沫陶瓷为载体,采用浸渍法制备了镍基泡沫陶瓷催化剂。结合SEM和XRD分析方法考察了镍基活性组分,煅烧温度,催化剂负载量等因素对催化剂活性的影响。结果表明,当镍源为Ni(NO3)2·6H2O,煅烧温度为700℃,催化剂负载量为3.50±0.2%时,制得的镍基泡沫陶瓷催化剂对焦油催化重整制氢反应具有较高的活性和较好的稳定性。(3)采用固定床反应器进行生物质焦油催化重整制氢实验,主要考察了反应温度,S/C,空气当量(ER)和再生催化剂四个因素对焦油催化重整制氢的影响。结果表明,当反应温度为500-900℃, S/C比为0-4,ER为0时,氢产量在28.29-105.28g H2/kg tar。但随着空气当量的增加,氢产量不断下降。SEM和XRD分析表明,在部分氧化过程中,催化剂活性组分通过燃烧积碳实现原位再生,而且催化剂再生后仍保持较高的活性。生物质焦油和重整油的GC/MS分析结果表明,活性组分镍促进了链烃化合物和苯环支链上C-C键、C-O键断裂以及杂环类化合物发生开环反应。
[Abstract]:Biomass tar is a kind of black by-product produced by pyrolysis and gasification of biomass with complex composition, high oxygen content and irritating smell. The existence of tar will not only affect the normal operation of the equipment, but also cause serious harm to the environment and human health, and then affect the industrialization development of biomass pyrolysis gasification technology. Catalytic method is an important method to remove biomass tar efficiently. Although the traditional catalytic method can decompose tar components effectively, it has some problems such as low tar conversion, poor resistance to carbon deposition, fast deactivation and low hydrogen yield. Its wide application in the field of pyrolysis and gasification is limited. Aiming at how to improve the removal efficiency of tar and to solve the problem of catalyst deactivation easily, the method of catalytic reforming of biomass tar for hydrogen production using nickel based catalyst was put forward in this paper. The kinetic characteristics of pyrolysis and combustion of tar were studied by thermogravimetric analysis. The distribution of products was analyzed by Py-GC / MS. The high efficient and stable nickel based foam catalyst was prepared, and the reaction conditions were changed. The optimum conditions for obtaining the maximum hydrogen yield were revealed, and the in-situ regeneration of the catalyst was realized by partial oxidation to ensure the long-term catalytic performance of the catalyst for tar. The thermochemical process of biomass tar at different heating rates was studied by thermogravimetric analysis (TGA). It is found that the pyrolysis process of biomass tar can be divided into three stages: volatilization stage, primary pyrolysis stage and secondary pyrolysis stage. The thermogravimetric curves show a similar trend at different heating rates. With the increase of the heating rate, the TG and DTG curves move to the high temperature region, and the tar pyrolysis temperature increases. The kinetics of biomass tar pyrolysis accords with the first-order kinetic reaction. According to the kinetic parameters of the pyrolysis region calculated by Arrhenius formula, the activation energy of the first pyrolysis reaction is 33.48-50.27kJ / mol, and the activation energy of the secondary pyrolysis reaction is 39.18-44.20kJ / mol / mol. The law of mass loss in biomass tar combustion is similar to that in pyrolysis process. The activation energy of combustion stage is 79.77-124.25kJ / mol, which is much larger than that of pyrolysis process. Py-GC / MS analysis shows that at different pyrolysis temperatures, the activation energy of biomass tar combustion is 79.77-124.25kJ / mol, which is much higher than that of pyrolysis process. The pyrolysis products of tar are mainly aromatics and ketones, and with the increase of pyrolysis temperature, the contents of ketones increase obviously, and the aromatic compounds decrease obviously. Nickel-based foam ceramic catalyst was prepared by impregnation method. Combined with SEM and XRD analysis, the effects of nickel based active components, calcination temperature and catalyst loading on the activity of the catalyst were investigated. The results show that when the nickel source is Ni(NO3)2 _ 6H _ 2O, the calcination temperature is 700 鈩，

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