超临界乙醇系统提质木焦油的温度影响

摘要

Wood tar is the by-product during biomass pyrolysis or gasification. Supercritical ethanol upgrading wood tar is an effective way to lower molecular weight and further utilization of wood tar. The wood tar, from biomass pyrolysis integrated multiproduct demonstration base in E'zhou of Hubei Province, was carried out in a high temperature and pressure autoclave under hydrogen atmosphere with the temperature of 280℃,300℃,320℃ and 340℃ respectively to study the influence of reaction temperature on supercritical ethanol upgrading wood tar. Materials and product's characteristics were investigated in various testing approaches, such as gas chromatography, gas chromatography-mass-spectrography (GC-MS) and liquid chromatography. In order to observe the upgrading effect of supercritical ethanol system intuitively, simulation experiment of GC-MS vaporizing chamber was conducted in fixed bed. Components purged out were defined as light oil components and the left were defined as heavy oil components. The result showed that the yield of liquid was the highest at the temperature of 320℃. The total proportion of CO and CO2 contents gradually decreased with the temperature increasing from 280℃ to 320℃ and slightly increased with the temperature increasing from 320℃ to 340℃. The simulation experiment data of GC-MS vaporizing chamber indicated that there was obvious effect of supercritical ethanol upgrading on wood tar and there was obvious increase of light oil components after upgrading. Besides, the results indicated that reaction temperature had an effect on upgrading. Light oil components gradually increased and heavy oil components decreased from 280℃ to 320℃ with the opposite tendency from 320℃ to 340℃. The data from liquid chromatography verified the conclusion above. There was obvious decrease of average molecular weight and dispersity after upgrading molecular weight distribution curve constantly narrowed from 280℃ to 320℃, which indicates macromolecular substance of liquid decreased. And molecular weight distribution curve broadened from 280℃ to 320℃, which indicated macromolecular substance of liquid increased. The components of upgrading oil showed a distinct change according to GC-MS data. The yield of phenols was the highest at 320℃, which could be beneficial for further utilization of wood tar.%木焦油是生物质热解气化过程中产生的副产物.超临界乙醇提质木焦油能够有效降低木焦油的分子量,有利于木焦油的进一步利用.以湖北鄂州生物质热解多联产示范基地的木焦油为原料,在高温高压反应釜上深入研究反应温度对超临界乙醇系统在氢气氛围下提质木焦油的影响,其中反应温度分别为280,300,320,340℃.采用气相色谱法以及气相色谱-质谱联用、液相色谱法对原料和热解产物进行分析.采用固定床模拟GC-MS气化室的实验,定义吹扫出去的成分为轻质油组分,残留的成分为重质油组分.结果表明,在超临界乙醇系统下,木焦油的绝大部分转化为液体产物,只有少量的固体与气体产物,其中反应温度为320℃时液体产率最高.从280℃到320℃,CO与CO2的总含量所占比例逐渐降低;从320℃到340℃,其比例略有上升.固定床模拟GC-MS气化室实验数据表明,超临界乙醇系统对木焦油有明显的提质效果,提质后轻质组分明显增多.且反应温度对提质效果有明显的影响:从280℃到320℃,轻质油组分不断上升,重质油组分不断下降;而从320℃到340℃,轻质油组分下降,重质油组分上升.液相色谱分析结果表明提质后平均分子量和分散度均有下降:从280℃到320℃,分子量分布曲线不断变窄,大分子物质减少;从320℃到340℃,分子量分布曲线变宽,大分子物质增多.提质后的有机成分也发生了明显变化,结合GC-MS数据,反应温度为320℃时酚类物质含量最多,利于木焦油的进一步利用.