Niobium on BEA dealuminated zeolite for high selectivity dehydration reactions of ethanol and xylose into diethyl ether and furfural
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| Main Author: | |
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| Publication Date: | 2020 |
| Other Authors: | , , , , |
| Format: | Article |
| Language: | eng |
| Source: | Repositório Institucional da UnB |
| Download full: | https://repositorio.unb.br/handle/10482/39298 https://doi.org/10.3390/nano10071269 https://orcid.org/0000-0003-4622-2445 https://orcid.org/0000-0003-0042-0091 https://orcid.org/0000-0002-3351-9226 |
Summary: | : In this work, we investigated the role of solid-state dealumination by (NH4)2SiF6 (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 (Brønsted and Lewis) present in the catalyst (n1 = 0.24 mmol g−1 , −∆H1 = 49 kJ mol−1 , and n2 = 0.20 mmol g−1 , –∆H2 = 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 ◦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 SN2 mechanism. The same catalyst was active and selective for transformation of xylose at 180 ◦C, showing 64% conversion and 51% selectivity for furfural (TON Furfural = 24.7) using water as a green solvent. |
| Summary: | : In this work, we investigated the role of solid-state dealumination by (NH4)2SiF6 (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 (Brønsted and Lewis) present in the catalyst (n1 = 0.24 mmol g−1 , −∆H1 = 49 kJ mol−1 , and n2 = 0.20 mmol g−1 , –∆H2 = 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 ◦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 SN2 mechanism. The same catalyst was active and selective for transformation of xylose at 180 ◦C, showing 64% conversion and 51% selectivity for furfural (TON Furfural = 24.7) using water as a green solvent. |
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