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Slow pyrolysis of xylan as pentose model compound for hardwood hemicellulose: a study of the catalytic effect of Na ions
Journal of Analytical and Applied Pyrolysis ( IF 6 ) Pub Date : 2019-01-01 , DOI: 10.1016/j.jaap.2018.12.004
P. Giudicianni , V. Gargiulo , M. Alfè , R. Ragucci , A.I. Ferreiro , M. Rabaçal , M. Costa

Abstract In this study, the effect of sodium (Na) ions on the slow pyrolysis of hemicellulose is assessed using xylan as a representative of hardwood hemicellulose. Thermogravimetric analysis and pyrolysis tests were conducted at slow heating rates (5 K/min) up to 973 K on commercial xylan, demineralized xylan and Na+ doped xylan samples. Commercial xylan was demineralized by using a cation-exchange resin to reduce the presence of inherent inorganics (mainly alkali or alkaline-earth metals). Subsequently, the demineralized xylan was doped with controlled amounts of Na ions (0.4, 0.5 and 1.1 wt.%) by using cation-exchange resin in Na+ form. The pyrolysis products yields (gas, liquid and char) and the composition of the gas mixture were quantified for each sample. Gas chromatography/mass spectrometry (GC/MS) analysis were performed to quantify the main species in the liquid products. The results, discussed considering of the available hemicellulose pyrolysis models, demonstrate that the presence of Na+ greatly affects the pyrolytic behavior of the samples, whereas only slight quantitative effects are observed on the solid residues yields, which increase with Na+ concentration. Furthermore, Na+ favors the ring opening reactions (increasing the production of CO2, CO and hydroxy ketones) and the rearrangement of the xylose ring to form furan derivatives. The reaction pathways competing with 2-furaldehyde production mechanism could explain the non-monotonous trend of this compound as function of Na+ content.

中文翻译:

木聚糖作为硬木半纤维素戊糖模型化合物的缓慢热解:钠离子催化作用的研究

摘要 在本研究中,使用木聚糖作为硬木半纤维素的代表,评估了钠 (Na) 离子对半纤维素缓慢热解的影响。热重分析和热解测试是在缓慢加热速率 (5 K/min) 下对商业木聚糖、脱矿质木聚糖和 Na+ 掺杂木聚糖样品进行的,最高温度可达 973 K。商业木聚糖通过使用阳离子交换树脂脱矿以减少固有无机物(主要是碱金属或碱土金属)的存在。随后,通过使用 Na + 形式的阳离子交换树脂,用受控量的 Na 离子(0.4、0.5 和 1.1 wt.%)掺杂脱矿质木聚糖。对每个样品的热解产物产率(气体、液体和炭)和气体混合物的组成进行量化。进行气相色谱/质谱 (GC/MS) 分析以量化液体产品中的主要物质。考虑可用的半纤维素热解模型讨论的结果表明,Na+ 的存在极大地影响了样品的热解行为,而对固体残留物产量仅观察到轻微的定量影响,随着 Na+ 浓度的增加而增加。此外,Na+ 有利于开环反应(增加 CO2、CO 和羟基酮的产生)和木糖环重排以形成呋喃衍生物。与 2-糠醛生产机制竞争的反应途径可以解释该化合物作为 Na+ 含量函数的非单调趋势。讨论考虑到可用的半纤维素热解模型,证明 Na+ 的存在极大地影响了样品的热解行为,而对固体残留物产量仅观察到轻微的定量影响,随着 Na+ 浓度的增加而增加。此外,Na+ 有利于开环反应(增加 CO2、CO 和羟基酮的产生)和木糖环重排以形成呋喃衍生物。与 2-糠醛生产机制竞争的反应途径可以解释该化合物作为 Na+ 含量函数的非单调趋势。讨论考虑到可用的半纤维素热解模型,证明 Na+ 的存在极大地影响了样品的热解行为,而对固体残留物产量仅观察到轻微的定量影响,随着 Na+ 浓度的增加而增加。此外,Na+ 有利于开环反应(增加 CO2、CO 和羟基酮的产生)和木糖环重排以形成呋喃衍生物。与 2-糠醛生产机制竞争的反应途径可以解释该化合物作为 Na+ 含量函数的非单调趋势。此外,Na+ 有利于开环反应(增加 CO2、CO 和羟基酮的产生)和木糖环重排以形成呋喃衍生物。与 2-糠醛生产机制竞争的反应途径可以解释该化合物作为 Na+ 含量函数的非单调趋势。此外,Na+ 有利于开环反应(增加 CO2、CO 和羟基酮的产生)和木糖环重排以形成呋喃衍生物。与 2-糠醛生产机制竞争的反应途径可以解释该化合物作为 Na+ 含量函数的非单调趋势。
更新日期:2019-01-01
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