Water effects on the acidic property of typical solid acid catalysts by 3,3-dimethybut-1-ene isomerization and 2-propanol dehydration reactions
Water effects on the acidic property of typical solid acid catalysts by 3,3-dimethybut-1-ene isomerization and 2-propanol dehydration reactions
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水对3,3-二甲基丁-1-烯异构化和2-丙醇脱水反应典型固体酸催化剂酸性的影响
DOI：
10.1016/j.cattod.2017.05.084
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发表时间：
2017-10-15
期刊：
影响因子：
5.3
通讯作者：
Xu, Bo-Qing
中科院分区：
文献类型：
--
作者：
Dai, Qiao-Ling;Yan, Bo;Xu, Bo-Qing
采用3，3-二甲基丁-1-烯的Bronsted酸性骨架异构化反应和异丙醇的脱水反应两种模型反应，考察了水对典型固体催化剂（HZSM-5、γ-Al_2O_3和Nb_2O_5）表面酸性的影响。对于异构化反应，反应原料中加入水对HZSM-5的催化作用影响不大，但对Nb 2 O 5的催化作用有显着的积极影响;典型的刘易斯酸性γ-Al 2 O3在有水或无水的情况下对该反应没有表现出活性。对于脱水反应，水对每种催化剂的催化作用通常是负面的，表明水的存在导致催化剂表面上的刘易斯酸性或多或少的中毒。水中毒的刘易斯酸性的Nb 2 O 5也导致产生的布朗斯台德酸性和更高的水分压（或H2O-底物比）较高的新产生的布朗斯台德酸性。然而，生成的布朗斯台德酸性没有发生在γ-Al_2 O_3和HZSM-5，无论水分压。三个Nb_2O_5样品与不同的煅烧温度，它们的行为清楚地表明，水对Nb_2O_5的影响也依赖于样品的煅烧温度敏感。此外，水的存在提高了γ-Al_2O_3和Nb_2O_5催化剂上脱水反应的活化能和二异丙醚的选择性，从而影响了反应过程中催化剂表面的酸性分布。
Two model reactions, namely the Bronsted-acidity-specific skeletal isomerization of 3,3-dimethylbut-1-ene for evaluating the Bronsted acidity and dehydration of 2-propanol for the overall acidity at the catalyst surface, were employed in this work to measure the effect of water on the surface acidic property of typical solid catalysts (HZSM-5, gamma-Al2O3 and Nb2O5). For the isomerization reaction, water addition in the reaction feed produced little effect on the catalysis of HZSM-5 but significantly positive effect on the catalysis of Nb2O5; the typical Lewis acidic gamma-Al2O3 showed no activity for this reaction in either the presence or absence of water. For the dehydration reaction, the effect of water was generally negative on the catalysis of every catalyst, demonstrating that water presence resulted in poisoning more or less of the Lewis acidity on the catalyst surface. Water poisoning of the Lewis acidity on Nb2O5 also resulted in generation of Bronsted acidity and the higher the H2O partial pressure (or H2O-to-substrate ratio) the higher the newly generated Bronsted acidity. However, generation of Bronsted acidity did not happen on gamma-Al2O3 and HZSM-5, regardless of the H2O partial pressure. Three Nb2O5 samples with varying calcination temperature were involved, and their behavior clearly indicated that the water effects on Nb2O5 also depended sensitively on the sample calcination temperature. Moreover, water presence increased the activation energy and selectivity for di-isopropyl ether of the dehydration reaction over gamma-Al2O3 and Nb2O5, and thus affected the acidity distribution at the catalyst surface during the reaction.