Study of butanol conversion to butenes over H-ZSM-5: Effect of chemical structure on activity, selectivity and reaction pathways
Study of butanol conversion to butenes over H-ZSM-5: Effect of chemical structure on activity, selectivity and reaction pathways
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DOI：
10.1016/j.apcata.2017.03.036
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发表时间：
2017-06-05
影响因子：
5.5
通讯作者：
Verberckmoes, An
中科院分区：
文献类型：
--
作者：
Gunst, Dieter;Alexopoulos, Konstantinos;Verberckmoes, An
为了评价丁醇作为绿色化学关键分子的可行性，考察了温度和反应时间对正丁醇、异丁醇和异丁醇三种异构体在H-ZSM-5上转化为丁烯的影响，以寻找最有希望的异构体。在脱水条件下，2-丁醇是目前为止最活跃的，只有1-丁醇才能观察到中间醚的形成。另一方面，只有异丁醇允许异丁烯的直接形成，异丁烯是丁烯中最有价值的异构体。因此，特别感兴趣的是进一步刺激生物质衍生的异丁醇的生产，例如通过适当的微生物的基因改造，以便此后在现有炼油厂用H-ZSM-5脱水时形成绿色的异丁烯。由于异丁醇的潜力很大，基于从头算的微观动力学模拟，对该分子进行了反应路径分析。将这些结果与1-丁醇的模拟结果进行比较，表明这种转变是由于主要反应途径通过反消除向直接脱水转移所致。Gibbs自由能分析表明，异丁醇醚化过渡态的大扭曲使这一途径变得不那么有利，导致没有形成二烷基醚，而异丁醇中烷基链的取代度增加促进了直接脱水途径，导致异丁醇与正丁醇相比总体活性增加。(C)2017爱思唯尔B.V.保留所有权利。
To evaluate the viability of the use of butanol as a green chemical key molecule, the effects of temperature and site time on the transformation of the three butanol isomers, 1-butanol, 2-butanol and iso-butanol, towards butenes over H-ZSM-5 have been studied in search of the most promising isomer. Under dehydration conditions, 2-butanol is by far the most active and intermediate ether formation is only observed for 1-butanol. On the other hand, only isobutanol allows the direct formation of isobutene, the most valuable of the butene isomers. Hence, it is especially interesting to further stimulate the biomass derived isobutanol production, e.g. via genetic modification of appropriate microorganisms, in order to allow thereafter the formation of green drop-in isobutene upon dehydration with H-ZSM-5 in existing refineries. Due to the large potential of isobutanol, a reaction path analysis via ab-initio based microkinetic simulations is conducted for this molecule. Comparing these results with simulations on 1-butanol indicates that the shift is occurring due to a shift of the dominant reaction pathway towards the direct dehydration via anti elimination. A Gibbs free energy analysis shows that the large distortion of the transition state for isobutanol etherification renders this path far less favorable, resulting in the lack of formation of the di-alkyl ether, whilst the increased degree of substitution of the alkyl chain in isobutanol is found to promote the direct dehydration path, leading to an increase of the overall activity of isobutanol as compared to 1-butanol. (C) 2017 Elsevier B.V. All rights reserved.