Glycerol Isopropyl Ethers: Direct Synthesis from Alcohols and Synthesis by the Reduction of Solketal

The catalytic reduction of solketal ((2,2‐dimethyl‐1,3‐dioxolan‐4‐yl)methanol) over bifunctional heterogeneous palladium catalysts is proposed as an alternative to the synthesis of glycerol isopropyl ethers by the etherification of glycerol. The direct synthesis of glycerol isopropyl ethers from iso...

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Bibliographic Details
Published in:ChemCatChem 2017-07, Vol.9 (14), p.2839-2849
Main Authors: Samoilov, Vadim O., Onishchenko, Maria O., Ramazanov, Dzhamalutdin N., Maximov, Anton L.
Format: Article
Language:English
Subjects:
Acetone
Alcohols
Aldehydes
Aluminosilicates
Aluminum
Aluminum silicates
Catalysts
Chemical reduction
Chemical synthesis
Condensates
Conversion
Ethers
Glycerol
green chemistry
hydrogenation
Isopropanol
mesoporous materials
Methanol
Oxidation
Palladium
Reaction products
Regioselectivity
Selectivity
solketal
Zeolites
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Summary:The catalytic reduction of solketal ((2,2‐dimethyl‐1,3‐dioxolan‐4‐yl)methanol) over bifunctional heterogeneous palladium catalysts is proposed as an alternative to the synthesis of glycerol isopropyl ethers by the etherification of glycerol. The direct synthesis of glycerol isopropyl ethers from isopropanol and glycerol requires severe conditions (T=130–150 °C, p(H2)=20–35 bar) and a large excess of isopropanol to reach a considerable yield. The main reaction products in the catalytic reduction of solketal are glycerol mono‐ and di‐isopropyl ethers and solketal isopropyl ether. Solketal conversion over Al‐HMS‐supported palladium catalysts (T=120 °C and p(H2)=20 bar) affords a mixture of ethers with a high degree of conversion (87 %), 78 % selectivity, and excellent regioselectivity between isomeric ethers. Zeolite‐BEA‐supported palladium catalysts also exhibit high activity but much lower selectivity because of intense acetone aldol condensation. The effects of Si/Al ratios in BEA zeolites and Al‐HMS aluminosilicates and the amounts of supported palladium (1 and 2 wt %) on the properties of the catalysts at different reaction temperatures and hydrogen pressures are considered. A roundabout route: Solketal was hydrogenated under mild conditions over Pd‐doped mesoporous aluminosilicas to yield a mixture of ethers and the isopropyl ether of solketal with high selectivity and yield. For high activity and selectivity, the balance between reductive and acid catalytic functions is essential. The significance of the approach for glycerol hydrophobization is discussed in comparison with the traditional acid‐catalyzed route.
ISSN:1867-3880
1867-3899
DOI:10.1002/cctc.201700108