Microwave-Assisted Aldol Condensation of Furfural and Acetone over Mg–Al Hydrotalcite-Based Catalysts

Alberto Tampieri,Francesc Medina,Matea Lilic,Magda Constantí

doi:10.3390/cryst10090833

Abstract

The depletion of fossil fuel resources has prompted the scientific community to find renewable alternatives for the production of energy and chemicals. The products of the aldol condensation between bio-based furfural and acetone have been individuated as promising intermediates for the preparation of biofuels and polymeric materials. We developed a protocol for the microwave-assisted condensation of these two compounds over hydrotalcite-based materials. Mg:Al 2:1 hydrotalcite was prepared by co-precipitation; the obtained solid was calcined to afford the corresponding mixed metal oxide, which was then rehydrated to obtain a meixnerite-type material. The prepared solids were characterized by PXRD, ICP-AES, TGA-DSC and N2 physisorption, and tested as catalysts in the aldol condensation of acetone and furfural in a microwave reactor. The performance of the catalysts was assessed and compared; the meixnerite catalyst proved to be the most active, followed by the mixed metal oxide and the as-synthesized hydrotalcite, which has often been reported to be inactive. In all cases, the reaction is quite fast and selective, which makes our protocol useful for rapidly converting furfural and acetone into their condensation products.

Highlights

Non-renewable resources are slowly, but inexorably, depleting [1]
The original, as-synthesized HT catalyst has the typical hydrotalcite structure, that is, a layered water and carbonate anions in the interlayer [32]: sharp (003), (006), (009), (110), and (113) diffraction double hydroxide structure of Mg–Al mixed hydroxides organized in brucite-like layers containing lines, and two broad (015) and (018) ones
The results of N2 physisorption analysis of HT and related materials very much depend shape of the HT isotherm resembles the shape of type III (Figure 4a), which commonly corresponds on the procedure followed for the preparation and the sample degassing [25,34,35,36]

Summary

Introduction

Non-renewable resources are slowly, but inexorably, depleting [1]. This has prompted researchers to find alternatives to fossil fuel-derived matter, which industry traditionally uses to produce energy and chemicals [2]. It is theoretically possible to switch fossil fuels for renewable sources, such as solar, wind, and hydrothermal energy [3], for the post-oil production of chemicals, alternative raw materials are required. Carbon is present on Earth in many forms. It is mostly stored in the lithosphere as carbonate minerals, whereas the part which actively takes part in the carbon cycle is distributed between the soil, atmosphere, and water as carbon dioxide, carbonates, and their intermediates, and as organic carbon in the fossil pool and biomass [4]. The extensive use of this strategy may be effective at reducing the emission of greenhouse gases and tackling the climate change problem [6]

Methods

Results

Discussion

Conclusion