Role of Lewis Acids of MIL-101(Cr) in the Upgrading of Ethanol to n-Butanol

Jian Zhou,Yifan Zheng,Yuqin Tong,Yaohui He,Jun Ni,Bing Xue,Xiaonian Li,Pengxiang Tu,Yunhui Cheng,Jie Cen

doi:10.3389/fceng.2020.586142

Jian Zhou, Yifan Zheng + Show 8 more

Open Access

https://doi.org/10.3389/fceng.2020.586142

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Abstract

The upgrading of bioethanol to n-butanol has recently been a focus of considerable attention due to the advantages of n-butanol over bioethanol as a sustainable fuel. The efficiency of this reaction is highly dependent on the development of catalysts, where understanding how catalysts perform is essential. However, traditional catalysts are normally composed of several kinds of active sites that work together synergistically in reactions, making it challenging to identify the role that individual active sites play. Herein, we synthesized three chromium-based MOFs ((MIL-101(Cr), where MIL stands for Matériaux Institut Lavoisier) with different Lewis acidities but without any basic sites. The linear relationship between Lewis acidities and their dehydration and condensation abilities suggests that there is a competition between the ethanol dehydration to diethyl ether and acetaldehyde condensation on Lewis acids. Upon the introduction of Pd, the Lewis acidity also dominates the particle size of Pd and then the dehydrogenation and hydrogenating abilities of catalysts.

Highlights

The upgrading of bioethanol to n-butanol has recently been a focus of considerable attention from both academic and industrial fields, given the advantages of n-butanol over bioethanol as a sustainable fuel (Jiang et al, 2016; Wu et al, 2017)
It is known that Lewis bases or Lewis acid-base pairs are active for acetaldehyde condensation
For the reaction over Lewis acid-base pairs, the strength of Lewis bases has to be moderate, and Lewis acids are considered responsible for adsorbing the second acetaldehyde molecule (Sato et al, 2012)

Summary

Introduction

The upgrading of bioethanol to n-butanol has recently been a focus of considerable attention from both academic and industrial fields, given the advantages of n-butanol over bioethanol as a sustainable fuel (Jiang et al, 2016; Wu et al, 2017). Our group developed Pd@UiO-66 catalysts, in which Pd nanoparticles are favorable for ethanol dehydrogenation and crotonaldehyde hydrogenation while coordinatively unsaturated Zr sites acting as Lewis acids are very active toward the aldol condensation of acetaldehyde (Jiang et al, 2018).

Results

Conclusion