Selectivity Control in the Tandem Aromatization of Bio‐Based Furanics Catalyzed by Solid Acids and Palladium

• Published in: ChemSusChem 2017-01, Vol.10 (1), p.277-286
• Main Authors: Genuino, Homer C., Thiyagarajan, Shanmugam, van der Waal, Jan C., de Jong, Ed, van Haveren, Jacco, van Es, Daan S., Weckhuysen, Bert M., Bruijnincx, Pieter C. A.
• Format: Article
• Language: English
• Subjects: acidity; Acids; Adducts; Anhydrides; biomass; Carbon - chemistry; Catalysis; Catalysts; Coupling; Furans - chemistry; Hydrogen-Ion Concentration; Hydrogenation; Palladium; Palladium - chemistry; Petrochemicals industry; Porosity; Selectivity; Steam; Zeolites; Zeolites - chemistry
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.201600776

Bio‐based furanics can be aromatized efficiently by sequential Diels–Alder (DA) addition and hydrogenation steps followed by tandem catalytic aromatization. With a combination of zeolite H‐Y and Pd/C, the hydrogenated DA adduct of 2‐methylfuran and maleic anhydride can thus be aromatized in the liquid phase and, to a certain extent, decarboxylated to give high yields of the aromatic products 3‐methylphthalic anhydride and o‐ and m‐toluic acid. Here, it is shown that a variation in the acidity and textural properties of the solid acid as well as bifunctionality offers a handle on selectivity toward aromatic products. The zeolite component was found to dominate selectivity. Indeed, a linear correlation is found between 3‐methylphthalic anhydride yield and the product of (strong acid/total acidity) and mesopore volume of H‐Y, highlighting the need for balanced catalyst acidity and porosity. The efficient coupling of the dehydration and dehydrogenation steps by varying the zeolite‐to‐Pd/C ratio allowed the competitive decarboxylation reaction to be effectively suppressed, which led to an improved 3‐methylphthalic anhydride/total aromatics selectivity ratio of 80 % (89 % total aromatics yield). The incorporation of Pd nanoparticles in close proximity to the acid sites in bifunctional Pd/H‐Y catalysts also afforded a flexible means to control aromatic products selectivity, as further demonstrated in the aromatization of hydrogenated DA adducts from other diene/dienophile combinations. Balancing act: A balance between the acidity and porosity of H‐Y zeolites and efficient coupling with a Pd catalyst is essential for the selective conversion of bio‐based furanics to renewable aromatic chemicals.