Publikationsserver der RWTH Aachen University
Selektive Hydrierung biogener organischer Disäuren mit Rutheniumphosphinkatalysatoren
Abstract
dc:descriptionIn the scope of this work the hydrogenation of diacids was investigated in depth on the example of itaconic acid. Rutheniumcatalysts with phoshineligands were stable and active hydrogenation catalysts. Mono- and bydentate ligands catalyse the conversion towards the 2- and 3-methyl-gamma-butyrolactone (2-MBGL and 3-MGBL) whereas the tridentate ligand 1,1,1-Tris-(diphenylphosphinomethyl)ethane (TriPhos) 2-methyl-1,4-butandiol (MBDO) yielded. Best solvents were found to be cyclic ethers which were inert under reaction conditions and in which the catalyst-components as well as the substrate were soluble. The reaction temperature had a high influence on the selectivity and activity of the reaction. Beneath 150°C no reaction was observed. Between 150°C und 185°C mainly the lactones 2-MBGL and 3-MGBL were formed and above this temperature the conversion of the lactones to the diol MBDO took place. To reach a high yield in 3-Methyltetrahydrofuran (3-MTHF) acidic additives had to be added. The combination of para-tolenesulfonic acid and ammoniumhexafluorophosphat in dioxan as solvent yielded 95% 3-MTHF. The reaction profile was recorded and it could be verified that the lactone hydrogenation proceeds only when the free acid is fully converted. The catalyst recycling is possible as recycling experiments showed. The use of 3-MTHF as solvent for the reaction resulted in complete conversion of itaconic acid. As reaction products the lactones 2-MBGL and 3-MGBL with 53% and 3-MTHF were identified. The possibility to influence the regio- and enantioselectivity was investigated for the synthesis of the lactones were . Variation of the ligand showed that rac-BINAP has a high conversion as well as a high chemoselectivity with a regioselectivity toward 3-MGBL. The enantioselective hydrogenation with the complex (BINAP)chlorodihydridoruthenium(II) yielded a regiomeric ratio of 1.9 and an ee-(R) of the same regioisomere of 5%. The scope of the catalyst system could be broadened to other biogenic diacids such as succinic acid, fumaric acid and methyl succinic acid with only little changes to the reaction conditions. The system could be optimized with fumaric acid as substrate to yield gamma-butyrolacton with 97%, 1,4-butandiol with 83% and THF with 95% depending on the conditions. The reactivity of 2-MGBL and MBDO was unexpected under reaction conditions the backreaction of MBDO the lactones was observed. To explain this behavior the active species was further investigated. An indication for a molecular catalyst was the negative mercury test for the presence of nanoparticles. The complex carbonyldihydrido(TriPhos)ruthenium(II) could be identified as single organometallic complex after the reaction. The formation of carbonyldihydrido(TriPhos)ruthenium(II) by decarbonylation of aldehydes could be demonstrated. A new synthesis route was developed yielding carbonyldihydrido(TriPhos)ruthenium(II) in 85% as yellow powder from rutheniumacetylacetonat, Triphos and propanal. By comparision of the activity of carbonyldihydrido(TriPhos)ruthenium(II) to the in situ system in the hydrogenation of levulinic acid the role of carbonyldihydrido(TriPhos)ruthenium(II) as catalyst could be clarified. Examples for the catalytic active species could be identified with levulinic acid and an acidic ionic liquid.
Degree
thesis:*- Grantor dc:publisher
- Publikationsserver der RWTH Aachen University
- Year dc:date
- 2011
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- Engendahl, Barthel
- Contributors dc:contributor
-
- Leitner, Walter
Subjects
dc:subject × 12Rights
dc:rights- Statement dc:rights
-
- info:eu-repo/semantics/openAccess
- Language dc:language
- ger