Amorphous Silica‐Alumina as Suitable Catalyst for the Diels‐Alder Cycloaddition of 2,5‐Dimethylfuran and Ethylene to Biobased p‐Xylene

Abstract

AbstractThe potential of amorphous silica‐alumina (ASA) to substitute zeolites (HBeta‐25) for the synthesis of p‐xylene via Diels‐Alder cycloaddition (DAC) of ethylene to 2,5‐dimethylfuran (2,5‐DMF) is investigated. ASA were prepared via homogeneous deposition‐precipitation of Al on SiO2. ASA shows good yields of p‐xylene (20–25 % after 18 hours) compared to bare silica and γ‐alumina. Brønsted acid sites (BAS) were identified as the active sites for the DAC reaction. The catalytic performance correlated strongly with the BAS concentration. Increasing the acidity of ASA is, however, limited by formation of agglomerated alumina‐type clusters at higher Al3+ content. While HBeta‐25 zeolite shows initially a slightly higher performance in terms of p‐xylene yield, ASA is the better catalyst upon calcination‐regeneration of the used catalyst. These results furthermore confirm that confinement in zeolite micropores is not a prerequisite for the DAC reaction between 2,5‐DMF and ethylene.