Germanosilicates for selective etherification of biomass-derived furfuryl alcohol

As high-octane fuel additives, biomass-derived furfuryl ethers (FE) can significantly enhance fuel efficiency. In the conventional production of FE from furfuryl alcohol (FA), the strong acid sites in Al-zeolites often cause severe ring-opening of the target product FE. Therefore, it is highly desired to design solid acids that can efficiently catalyze the FA etherification while preventing FE decomposition. Herein, we demonstrate that germanosilicates (Ge-zeolites) exhibit superior target FE yield compared with conventional Al-zeolites and Ti-zeolites. Benefitting from the special germanium-enriched double-four-membered-ring (D4R) building units, Ge-zeolites (Si/Ge = 3–10, UOV, BEC, and -IRT) possess abundant acid sites with suitable strength and excellent diffusion ability. Ge-zeolites in UOV, BEC, and –IRT topology exhibit FEE yields of 85.3 %, 89.8 %, and 75.6 % after reaction for 60, 15, and 5 min under the reaction conditions investigated, respectively. The density functional theory (DFT) simulations confirm that the energy barrier of the ring-opening of FEE over Ge atoms within these zeolites is much higher than that over the Al atoms in traditional Al-zeolites. The inherent extra-large pore channel of Ge-zeolites also minimizes intrapore diffusion constraints, greatly improving the accessibility of active sites and the rapid diffusion of products. Moreover, the Ge-zeolites exhibit certain structural stability in alcoholic solvent systems, resulting in good recyclability and practical application.