One-Pot Conversion of Acetone into Mesitylene over Combinations of Acid and Basic Catalysts

Laura Faba,Eva Diaz,Salvador Ordóñez,Jorge Quesada,Juan Gancedo

doi:10.1021/acscatal.1c03095

Abstract

The transformation of acetone (a byproduct of phenol manufacturing or a bioderived chemical) into mesitylene is a very attractive reaction to prepare renewable fuels and chemicals. This reaction has been studied over both base and acid catalysts, with relevant limitations (side reactions over acid catalysts, oligomerization of isophorones over basic materials, etc.). We propose an alternative strategy to perform this reaction combining acid and basic catalysts either as separate beds or as mechanical mixtures. For this purpose, we first study the reaction over five representative materials (β-zeolite, Al-MCM-41, Mg–Al mixed oxide, MgO, and TiO2). These studies allow determining the rate-limiting steps and identifying the most relevant catalytic properties to enhance the selectivity toward mesitylene, minimizing the deactivation produced by the permanent adsorption and oligomerization as well as side reactions yielding undesired products (β-scissions). Once the combining strategies are studied, we propose using double beds of Al-MCM-41 and TiO2 as the optimum approach. The observed synergistic effects enhance the mesitylene productivity by more than 57% to the most active catalyst (Al-MCM-41), working at a low temperature (250 °C). This improvement is due to the activity of the base catalyst (TiO2), producing an optimum mixture of mesityl oxide and acetone that contacts with the acid catalyst (Al-MCM-41), where the second condensation and dehydration steps are so fast that the mesitylene production is stable, not being affected by any deactivation process.

Highlights

IntroductionTraditional routes to produce it, as pseudocumene isomerization, use petroleum as a raw material,[7] owning a nonrenewable character
Mesitylene (1,3,5-trimethylbenzene) is a high-value chemical, being an intermediate for different manufacturing processes because of its high reactivity.[1−3] Its main applications are in organic synthesis and the production of high-octane additives to liquid fuels.[4−6]Traditional routes to produce it, as pseudocumene isomerization, use petroleum as a raw material,[7] owning a nonrenewable character
This study proposes a new approach based on a doublecatalytic system, combining a basic metal oxide and acidic aluminosilicates with different configurations

Summary

Introduction

Traditional routes to produce it, as pseudocumene isomerization, use petroleum as a raw material,[7] owning a nonrenewable character These routes have technical drawbacks due to the difficulties isolating products with similar boiling points (e.g., mesitylene and 2-ethyltoluene, 165 °C). In this context, the development of alternative routes using renewable raw materials and solid catalysts is one of the main challenges of chemical engineering, with the acetone route being one of the most promising ones.[8,9]. The same compound is obtained when using acids but after the protonation of the oxygen of the carbonyl group that, by resonance equilibrium, produces the abstraction of the most positively charged proton, the one from the α-carbon This abstraction is required to promote the bimolecular C−C coupling step

Methods

Results

Conclusion