Boron Nitride: A Support for Highly Active Heteropolyacids in the Methanol-to-DME Reaction,ACS Catalysis

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Boron Nitride: A Support for Highly Active Heteropolyacids in the Methanol-to-DME Reaction
ACS Catalysis ( IF 11.3 ) Pub Date : 2017-05-04 00:00:00 , DOI: 10.1021/acscatal.7b00808
Josefine Schnee ₁ , Adrien Eggermont ₁ , Eric M. Gaigneaux ₁

Affiliation

Due to its superacidity and ability of its bulk to react following a pseudoliquid mechanism, the Keggin H₃PW₁₂O₄₀ heteropolyacid attracts more and more attention as a catalyst for the gas phase methanol-to-DME reaction. However, in its pure state, H₃PW₁₂O₄₀ has a very low surface area (typically 5–10 m²/g), which limits the accessibility of its inner protons due to diffusional constraints and explains why teams investigate H₃PW₁₂O₄₀ in its supported form. In the present work, we highlight the interest of using hexagonal boron nitride (BN) as a support. We show that, in contrast to commonly used supports such as TiO₂, BN is able to increase the accessibility of H₃PW₁₂O₄₀’s acid sites (i.e., stabilizing small enough crystallites) while preserving their strong acidity (i.e., not interacting too much with the Keggin units). At low loadings (typically around 16% of one ideal Keggin monolayer), BN leads H₃PW₁₂O₄₀ to reach an almost 2 times higher methanol conversion than obtained with the adequately activated pure bulk sample, and an almost 10 times higher conversion than an optimized TiO₂-supported H₃PW₁₂O₄₀ catalyst. At higher H₃PW₁₂O₄₀ loadings, the BN-supported catalysts are still much more active than the optimized TiO₂-supported one, but less active than the pure bulk-activated H₃PW₁₂O₄₀, which we attribute to the partial intercalation of H₃PW₁₂O₄₀ within the interlayers of BN.

中文翻译：

氮化硼：甲醇制DME反应中高活性杂多酸的支持物

由于其超酸度和其本体遵循拟液机理反应的能力，Keggin H ₃ PW ₁₂ O ₄₀杂多酸作为气相甲醇制DME反应的催化剂越来越受到关注。然而，在纯净状态下，H ₃ PW ₁₂ O _40的表面积非常低（通常为5-10 m ² / g），由于扩散限制，它限制了其内部质子的可及性，并解释了为什么团队研究H ₃ PW ₁₂ Ô ₄₀以其受支持的形式。在当前的工作中，我们强调了使用六方氮化硼（BN）作为载体的兴趣。我们表明，与常用的载体（如TiO _2）相比，BN能够增加H ₃ PW ₁₂ O ₄₀的酸性位点的可及性（即稳定足够小的微晶），同时保留其强酸度（即不与Keggin单位互动过多）。在低负载下（通常约为一个理想的Keggin单层膜的16％），BN导致H ₃ PW ₁₂ O _40的甲醇转化率比充分活化的纯大块样品所获得的甲醇转化率高几乎2倍，而转化率则比其高出近10倍。优化的二氧化钛₂负载的H ₃ PW ₁₂ O ₄₀催化剂。在较高的H ₃ PW ₁₂ O ₄₀负载下，BN负载的催化剂的活性仍然比优化的TiO ₂负载的催化剂高得多，但比纯的本体活化的H ₃ PW ₁₂ O ₄₀活性低，我们将其归因于H ₃ PW ₁₂ O ₄₀在BN中间层中的部分嵌入。

更新日期：2017-05-13

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