Mixed alcohol dehydration over Bronsted and Lewis acidic catalysts
Mixed alcohol dehydration over Bronsted and Lewis acidic catalysts
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DOI：
10.1016/j.apcata.2015.11.019
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发表时间：
2016-01-25
影响因子：
5.5
通讯作者：
Hensley, Jesse E.
中科院分区：
文献类型：
--
作者：
Nash, Connor P.;Ramanathan, Anand;Hensley, Jesse E.
混合醇是生物质衍生的合成气的有吸引力的氧化产物，因为它们可以催化转化为一系列烃产物，包括液体烃燃料。催化脱水形成烯烃是将C-2-C-4醇转化为长链烃的潜在第一步。我们在此描述了4种布朗斯台德和刘易斯酸性催化剂的物理和化学表征沿着以及催化活性和选择性，用于两种混合醇进料流的脱水，所述混合醇进料流代表来自在K-CoMoS型催化剂上的合成气转化的产物（即，乙醇、1-丙醇、1-丁醇和2-甲基-1-丙醇）。具体地，在250、300和350 ℃下测试掺入刘易斯酸性Zr的中孔硅酸盐（Zr-KIT-6）、商业含Al的中孔硅酸盐（Al-MCM-41）、商业微孔铝硅酸盐（HZSM-5）和商业微孔硅铝磷酸盐（SAPO-34）的混合醇脱水。沸石材料在所有温度下都表现出高活性（>98%乙醇转化率），而中孔材料仅在300 ℃或高于300 ℃下表现出显著活性（>10%乙醇转化率）。在300 ℃下，乙醇脱水的转换频率按以下顺序降低：HZSM-5 > SAPO-34 > Al-MCM-41 > Zr-KIT-6，表明Bronsted酸性中心比刘易斯酸性中心对醇脱水更有活性。在300 ℃下，SAPO-34从无水的富含乙醇的进料流和含水的富含C3+醇的进料流中产生最高产率的烯烃产物。反应后表征表明Zr-KIT-6、Al-MCM-41和HZSM-5的Bronsted与刘易斯酸中心比发生了变化。氨程序升温脱附表明，反应后样品的酸位可以在空气中处理后再生。反应后的SAPO-34催化剂含有更多的芳香族化合物，甲基化的芳香族化合物和多环芳烃比它的沸石对应物HZSM-5，而没有观察到芳香族化合物的反应后的Al-MCM-41或Zr-KIT-6催化剂。在300 ° C下经SAPO-34的烯烃产率（>95%）与甲醇制烯烃方法的公开值相当，表明混合醇脱水的潜在工业应用。此外，烯烃产物在SAPO-34上的分布可通过醇进料混合物的组成来调节。(C)2015 Elsevier B. V.版权所有。
Mixed alcohols are attractive oxygenated products of biomass-derived syngas because they may be catalytically converted to a range of hydrocarbon products, including liquid hydrocarbon fuels. Catalytic dehydration to form olefins is a potential first step in the conversion of C-2-C-4 alcohols into longer-chain hydrocarbons. We describe here the physical and chemical characterization along with catalytic activity and selectivity of 4 Bronsted and Lewis acidic catalysts for the dehydration of two mixed alcohol feed streams that are representative of products from syngas conversion over K-CoMoS type catalysts (i.e., ethanol, 1-propanol, 1-butanol and 2-methyl-1-propanol). Specifically, a Lewis acidic Zr-incorporated mesoporous silicate (Zr-KIT-6), a commercial Al-containing mesoporous silicate (Al-MCM-41), a commercial microporous aluminosilicate (HZSM-5), and a commercial microporous silicoaluminophosphate (SAPO-34) were tested for mixed alcohol dehydration at 250, 300 and 350 degrees C. The zeolite materials exhibited high activity (>98% ethanol conversion) at all temperatures while the mesoporous materials only displayed significant activity (>10% ethanol conversion) at or above 300 degrees C. The turnover frequencies for ethanol dehydration at 300 degrees C decreased in the following order: HZSM-5 > SAPO-34 > AI-MCM-41 > Zr-KIT-6, suggesting that Bronsted acidic sites are more active than Lewis acidic sites for alcohol dehydration. At 300 degrees C, SAPO-34 produced the highest yield of olefin products from both a water-free ethanol rich feed stream and a C3+-alcohol rich feed stream containing water. Post-reaction characterization indicated changes in the Bronsted-to-Lewis acidic site ratios for Zr-KIT-6, Al-MCM-41 and HZSM-5. Ammonia temperature programmed desorption indicated that the acid sites of post-reaction samples could be regenerated following treatment in air. The post-reaction SAPO-34 catalyst contained more aromatic, methylated aromatic and polyaromatic compounds than its zeolite counterpart HZSM-5, while no aromatic compounds were observed on post-reaction Al-MCM-41 or Zr-KIT-6 catalysts. Olefin yield at 300 degrees C over SAPO-34 (>95%) was comparable to published values for the methanol-to-olefins process, indicating the potential industrial application of mixed alcohol dehydration. Furthermore, the olefin product distribution over SAPO-34 was tunable by the composition of the alcohol feed mixture. (C) 2015 Elsevier B.V. All rights reserved.