The utilization of renewable resources has been given more attention in the past decade due to the growing shortage of fossil fuels and the worsening of global climate problems. Biomass, including wood residues and agricultural residues, is one of the most promising renewable resources due to wide distribution, large yield, and renewability. Pyrolysis is one of the most appropriate thermochemical processes and can convert biomass into bio-oil, bio-gas, and bio-char. In order to use pyrolysis pathway of corn stalk more efficiently, analytical Py-GC/MS (pyrolysis-gas chromatography/mass spectrometry) experiments were performed at 300, 400, and 500℃ to investigate the pyrolysis characteristics and product distributions of the corn stalk fractions (including stem bark, leaf, ear husk, and stem pith) and explore the effects of chemical inhomogeneity on pyrolysis behaviors of the corn stalk fractions, as well as determine the effects of pyrolysis temperature on the product distribution. The results indicated that the pyrolysis characteristics of the corn stalk fractions differed remarkably from each other and were influenced differently by the pyrolysis temperature. With an increase in pyrolysis temperature from 300 to 500℃, total yields of volatile products including phenolics, furans, linear aldehydes, linear ketones, anhydrosugars, linear acids, and others increased from all samples. However, the changes of the total yields of volatile products were different among samples. The most increase from total yields of volatile products was obtained from stem pith at 300℃ and from stem bark at 400-500℃, which suggested that the pyrolysis progress of stem pith germinated more easily at a lower temperature. The total yield of volatile products of ear husk was the lowest at every pyrolysis temperature. At 300℃, the highest value of phenolics content in pyrolysis products was 29.76% from stem pith and the lowest value was 13.97% from ear husk; the highest furans value of 12.34% was from whole corn stalk and the lowest value of 7.60% was from ear husk. At 500℃, the most linear aldehydes content of 18.40% was obtained from leaf, the stem pith was degraded into more linear ketones at 12.45%, and the anhydrosugars content at 4.31% was the highest value from stem bark. The identified chemical compounds contents in the pyrolysis products were different according to the pyrolysis temperature among samples. The 4-vinyl phenol (4-VP) content at 21.27% was the highest from stem pith at 300℃, which suggested more pyrolysis selectivity for 4-VP. However, stem bark pyrolysis could obtain the highest 5-hydroxymethyl furfural (HMF) content of 6.61% at 300℃. At the pyrolysis temperature range of 400-500℃, the most feedstock in corn stalk fractions to form hydroxyacetaldehyde (HAA) and 1-hydroxy-2-propanone (HA) was the leaf. Ear husk as feedstock could be a good selection for product bio-oil due to low acetic acid (AA) in the pyrolysis product. Chemical inhomogeneity among corn stalk fractions could be the main reason for their pyrolysis characteristic differences. Biomass fractions should be given optimum applications in the future. The research results will provide a theoretical basis for using high value biomass and develop a new road of biomass selective pyrolysis.%为了优化玉米秆的热解利用途径,该文通过Py-GC/MS(快速热解-气相色谱/质谱联用)试验,考察了玉米全秆及其不同部位(秆皮、叶子、苞叶、芯部)的快速热解特性与产物分布,以及热解温度对产物分布的影响。试验结果表明,玉米秆不同部位热解特性差异显著,且受热解温度的影响也不同;芯部低温快速热解产物中富含4-乙烯基苯酚(4-vinyl phenol,4-VP),其在300℃下的相对峰面积高达21.27%,同时通过外标法确定其绝对产率为5.05%;秆皮在300℃时的快速热解产物中不但含有大量的4-VP ,还含有较多的5-羟甲基糠醛(5-hydroxymethyl furfural,HMF,相对峰面积达到6.61%);叶子在中温(500℃)下的热解产物中含有较高的小分子醛酮类物质;而苞叶在中温(500℃)下热解产物中的酸含量最低,适用于制备作为液体燃料的生物油。该文的研究成果将为生物质高值化利用提供理论依据,为生物质选择性热解提供新思路。
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