Niobium on BEA Dealuminated Zeolite for High Selectivity Dehydration Reactions of Ethanol and Xylose into Diethyl Ether and Furfural

In this work, we investigated the role of solid-state dealumination by (NH4)(2)SiF6(25% Al removal and 13% Si insertion), the impregnation of niobium (10, 18, and 25 wt. %) on dealuminated *BEA (DB) zeolite and their catalytic properties in ethanol and xylose transformations. Among all the studied catalysts, 18%Nb-DB showed increased mesoporosity and external areas. A leveling effect in the number and strength of the proposed two sites (Bronsted and Lewis) present in the catalyst (n(1)= 0.24 mmol g(-1), -Delta H-1= 49 kJ mol(-1), and n(2)= 0.20 mmol g(-1), -Delta H-2= 42 kJ mol(-1)) in the catalyst 18%Nb-DB, might be responsible for its good activity. This catalyst presented the highest selectivity for diethyl ether, DEE (97%) with 61% conversion after 50 ethanol pulses at 230 degrees C (turnover number, TON DEE = 1.15). These features allowed catalytically fruitful bonding of the ethanol molecules to the neighboring sites on the channels, facilitating bimolecular ether formation through a possible SN(2)mechanism. The same catalyst was active and selective for transformation of xylose at 180 degrees C, showing 64% conversion and 51% selectivity for furfural (TON Furfural = 24.7) using water as a green solvent.