Pt/CeO2 with residual chloride as reusable soft Lewis acid catalysts: application to highly efficient isomerization of allylic esters

Abstract

Heterogeneous acid and base catalysts play a crucial role in many important chemical processes. Hard Lewis and Brønsted acid catalysts like silica-alumina and zeolites have been widely applied in numerous reactions; however, developing reusable and active soft Lewis acid catalysts remain a challenge. Herein, we demonstrate for the first time that a highly dispersed supported platinum catalyst can act as a heterogeneous soft Lewis acid. High turnover numbers and reusability were observed in the isomerization of allylic esters under solvent-free conditions. Moreover, the as-prepared catalysts are characterized by X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) analyses, revealing that the highly dispersed Pt clusters with Pt–Cl bonds play a key role in the high activity. The residual chloride anion enhances the Lewis acidity of the Pt metal center and thus improves the catalytic activity. Simultaneously, the high catalytic activity of Pt/CeO2 with residual chloride and the soft Lewis acid mechanism are also proved by density functional theory (DFT) calculations based on the model reaction.

Deoxydehydration of Biomass‐Derived Polyols Over Silver‐Modified Ceria‐Supported Rhenium Catalyst with Molecular Hydrogen

“…An early study of DODH [27] reported that direct DODH of cis ‐2‐butene‐1,4‐diol did not occur in the Cp*ReO 3 +PPh 3 system but isomerization (OH group migration) to 3‐butene‐1,2‐diol did, which can be further converted to 1,3‐butadiene. A recent study has showed that 3,4‐diacetoxy‐1‐butene (diester of 3‐butene‐1,2‐diol) can be isomerized to the equilibrium mixture of diacetoxybutenes over noble metal catalysts such as Pt/CeO 2 [64] . However, our results of the reaction of cis ‐2‐butene‐1,4‐diol with very low selectivity to 3‐butene‐1,2‐diol rather suggested the direct conversion to 1,3‐butadiene without initial isomerization to 3‐butene‐1,2‐diol.…”

Sustainable biochar: A facile strategy for soil and environmental restoration, energy generation, mitigation of global climate change and circular bioeconomy

“…It has been observed that with aging, the capacity of anionic exchange also decreases (Cao et al, 2019). Hard Lewis acid adsorption takes place through ion exchange, e.g., via carboxylic functionalities, whereas soft Lewis acid adsorption occurs through mechanisms of the cation-π bonding (Huang et al, 2021). It was noticed that the sorption capability is governed by the surface area and aromaticity-porosity.…”