Cu/MgAl₂O₄ as Bifunctional Catalyst for Aldol Condensation of 5‐Hydroxymethylfurfural and Selective Transfer Hydrogenation

Abstract

Copper supported on mesoporous magnesium aluminate has been prepared as noble-metal-free solid catalyst for aldol condensation of 5-hydroxymethylfurfural with acetone, followed by hydrogenation of the aldol condensation products. The investigated mesoporous spinels possess high activity as solid-base catalysts. Magnesium aluminate exhibits superior activity compared to zinc and cobalt-based aluminates, reaching full conversion and up to 81 % yield of the 1:1 aldol product. The high activity can be correlated to a higher concentration of basic surface sites on magnesium aluminate. Applying continuous regeneration, the catalysts can be recycled without loss of activity. Focusing on the subsequent hydrogenation of aldol condensation products, Cu/MgAl2 O4 allows a selective hydrogenation and CO bond cleavage, delivering 3-hydroxybutyl-5-methylfuran as the main product with up to 84 % selectivity avoiding ring saturation. Analysis of the hydrogenation activity reveals that the reaction proceeds in the following order: CC>CO>CO cleavage>ring hydrogenation. Comparable activity and selectivity can be also achieved utilizing 2-propanol as solvent in the transfer hydrogenation, providing the possibility for partial recycling of acetone and optimization of the hydrogen management.

Design and fabrication of mesoporous heterogeneous basic catalysts

“…The bifunctional catalysts were active in Sonogashira and Henry tandem reactions. 406 Mesoporous spinel with strong basicity was prepared by a hardtemplating method using magnesium and aluminum nitrates as precursors and activated carbon as a template. Both amine and Pd II -diamine grafted monofunctional catalysts can catalyze the respective individual reactions, but not both.…”

Hydrogenation of biomass-derived compounds containing a carbonyl group over a copper-based nanocatalyst: Insight into the origin and influence of surface oxygen vacancies

“…Additionally, GBL can be obtained by hydrogenating petroleum-based maleic anhydride over various noble metal and copper-based catalysts [3,4]. With the shortage of fossil resources and increasing emission of greenhouse gases, the conversion from sustainable and renewable raw biomass to useful fuel and chemicals has become more important in the past decade [5][6][7][8][9]. Thanks to the development of biorefinery processes, for example, succinic acid and its derivatives are becoming promising biobased C4 platform molecules for replacing other chemicals such as maleic anhydride [10,11].…”

Base‐Catalyzed Condensation of Levulinic Acid: A New Biorefinery Upgrading Approach

“…This reaction increases the length of the carbon chain by a base‐catalyzed mechanism that begins with abstraction of a proton α to the carbonyl functional group. This reaction has already been proposed to upgrade bioplatform molecules, such as acetone, 5‐hydroxymethylfurfural, and furfural . Although acetone self‐condensation is often studied in the gas phase, most aldol condensations are performed in the aqueous phase, at low pressure, and mild temperatures, and it leads to sustainable and environmentally benign biorefinery processes.…”

“…This reaction has already been proposed to upgrade bioplatform molecules, such as acetone, 5‐hydroxymethylfurfural, and furfural . Although acetone self‐condensation is often studied in the gas phase, most aldol condensations are performed in the aqueous phase, at low pressure, and mild temperatures, and it leads to sustainable and environmentally benign biorefinery processes. Despite the fact that the first references about these reactions propose homogeneous catalysts such as NaOH and KOH, there have been important advances in the development of active, selective, and stable solid basic catalysts, such as mixed oxides, aluminophosphate, and carbon materials …”