【作者】 王锐；

【导师】 贲昊玺；

【作者基本信息】 东南大学 ， 热能工程， 2021， 硕士

【摘要】 生物油是一种由生物质热解得到的具有应用价值的液体产品,热解油中含有成百上千种化合物,成分复杂。这种复杂的成分结构既给各种表征技术带来了困难,又给生物油老化创造了条件。因此,清晰地表征生物油以及了解生物油的老化机理是加深对生物油成分结构的理解、研究稳定生物油性质的方法的基础。本文在深入研究生物油¹³C NMR核磁共振技术的基础上,借助生物油核磁共振技术和生物油模型化合物对生物油老化机理进行深入研究。研究中建立了一种借助生物油核磁碳谱技术高效准确表征生物油的标准方法,同时创新地提出了一种借助生物油核磁碳谱计算生物油中C、H和O含量的方法,并且在实验中也明确了生物油中不同类型物质在生物油老化过程中起到的作用。首先,本文对生物质核磁共振表征技术进行了深入研究。生物油核磁碳谱虽然能表征全谱的生物油,但仍然存在核磁时间较长的问题,为了在保持测试结果的准确性的同时缩短生物油¹³C NMR核磁共振表征技术的测试时间,实验过程中测试了不同的驰豫试剂浓度、脉冲时间和扫描次数对¹³C NMR测试时间以及准确性的影响。最终通过实验结果可以确定添加5mg/ml的Cr（acac）₃、设置3s的脉冲时间和1k的扫描次数这样的核磁测试条件是最优的,这种核磁测试条件仅用1.5小时就能获得原来需要20多小时才能获得的核磁测试结果。在研究过程中,还通过测试三种含氧量不同的生物油样品,结合¹³C NMR、DEPT90和DEPT135这三种谱图对生物油中C、H和O的含量进行了计算。与传统的C、H和O含量计算方法相比,该方法计算C含量的绝对误差为4%,计算H含量的绝对误差为1.5%,计算O含量的绝对误差为2%,虽然不能用于分析各种生物油样品中的细微差异,但已足够适用于生物油样品中C、H和O含量的量级分析。为简化生物油的老化过程、深入了解生物油的老化机理,选取了来自于纤维素和半纤维素部分以及木质素和丹宁部分的生物油模型化合物,并且将这些模型化合物分为四类在生物油老化过程中可能发生的反应（单独老化、酯化、醛醇缩合以及酚醛反应）,分别放置于80℃下加热老化72小时。在这些模型化合物中,酸类物质和醛类物质在生物油老化过程中扮演着非常重要的角色,酸类物质不仅是生物油老化反应的反应物还是老化反应的催化剂,而醛类物质的存在会加速生物油的老化过程。为进一步验证生物油模型化合物在真实生物油环境下对生物油老化过程的作用,根据生物油模型化合物老化反应的结果,选取了三种模型化合物（乙醇、糖醛和5-羟甲基糠醛）分别与生物油混合后置于80℃下加热老化72小时,每12小时取样进行检测。实验结果表明乙醇具有缓解生物油老化的作用,它能提升生物油的PH值,保护生物油中酮类醛类这些官能团,从而抑制老化反应的发生。而糖醛和5-羟甲基糠醛,这两种物质的存在会大大推动生物油老化过程,使生物油中发生缩合反应生成高分子物质。更多还原

【Abstract】 Bio-oil is a kind of valuable liquid product obtained by pyrolysis of biomass.Pyrolysis oil with complex components contains hundreds of compounds.This complex composition of bio-oil not only brings difficulties to various characterization techniques,but also creates environment for bio-oil aging.Therefore,a clear characterization of bio-oil and understanding of the aging mechanism of bio-oil are the basis for deepening the understanding of the composition of bio-oil and studying methods to stabilize bio-oil properties.Based on the in-depth study of bio-oil ¹³C NMR,bio-oil NMR technology and bio-oil model compounds were used to conduct in-depth research on the aging mechanism of bio-oil,so as to achieve the purpose of clearly characterizing the composition of bio-oil and clarifying the aging mechanism of bio-oil.In the research,a standard method for efficiently and accurately characterizing bio-oil with the help of bio-oil nuclear magnetic carbon spectroscopy was established.At the same time,a method for calculating the content of C,H and O in bio-oil based on ¹³C NMR technology was innovatively proposed.The experiment also clarified the role of different types of substances in bio-oil during the aging process of bio-oil.First of all,this article conducts an in-depth study on the biomass NMR characterization technology.Although ¹³CNMR can characterize the full spectrum of bio-oil,there is still the problem of long NMR time.In order to shorten the ¹³C NMR test time while maintaining the accuracy of the test results,the influences of different relaxation reagent concentrations,pulse times and scan times on ¹³C NMR test time and accuracy were tested.The experiment results show that adding 5mg/ml Cr（acac）₃,setting the pulse time of 3s and the number of scans of1k are optimal NMR test condition,and this NMR test condition only takes 1.5 hours.During the research process,a method of calculating the content of C,H and O in the bio-oil was established by testing three bio-oil samples with different oxygen content and combining the three spectra of ¹³C NMR,DEPT90 and DEPT135.Compared with the traditional C,H and O content calculation method,this method has an absolute error of 4%for calculating C content,an absolute error of 1.5%for calculating H content,and an absolute error of 2%for calculating O content,although it can not be used to analyze the subtle differences in various bio-oil samples,it is sufficient for the magnitude analysis of C,H and O content in bio-oil samples.In order to simplify the aging process of bio-oil and to understand the aging mechanism of bio-oil,bio-oil model compounds from cellulose and hemicellulose parts,lignin and tannin parts were selected for aging tests,and these model compounds were divided into four categories（self-condensation,esterification,aldol condensation,and phenol and aldehyde reaction）,which were heated and aged at 80°C for 72 hours.Among these model compounds,acids and aldehydes play a very important role in the aging process of bio-oil.Acids are not only reactants in the aging reaction of bio-oil but also catalysts for aging reactions.And the presence of aldehydes will accelerate the aging process of bio-oil.In order to further verify the effect of bio-oil model compounds on the aging process of bio-oil in the real bio-oil environment,three model compounds（ethanol,2-furaldehyde and5-hydroxymethyl furfural）were selected according to the results of the aging reaction of bio-oil model compounds.They were mixed with bio-oil and heated and aged at 80°C for 72hours,and samples were taken every 12 hours for testing.Ethanol has the effect of slowing the aging rate of bio-oil.It can increase the PH value of bio-oil and protect the functional groups of ketones and aldehydes in bio-oil.Thereby,it can inhibit the occurrence of aging reactions.The presence of 2-furaldehyde and 5-hydroxymethyl furfural will greatly promote the aging process of bio-oil,causing condensation reaction in the bio-oil and producing high molecular substances.更多还原