Κατεύθυνση Ομογενής ΚατάλυσηLibrary of the School of Science
Γεώργιος Παπαδογιαννάκης Αναπληρωτής Καθηγητής ΕΚΠΑ (Επιβλέπων), Χριστιάνα Μητσοπούλου, Καθηγήτρια ΕΚΠΑ , Μαρίνος Πιτσικάλης Αναπληρωτής Καθηγητής ΕΚΠΑ
Εκλεκτική υδρογόνωση των ανανεώσιμων μεθυλεστέρων του λινελαίου καταλυόμενη από συστήματα του λευκοχρύσου τροποποιημένα με το μετά Νατρίου ‘Αλας της τρισουλφονικής τριφαινυλοφωσφίνης σε υδατικό περιβάλλον
Selective Hydrogenation of Renewable Methyl Esters of Linseed oil Catalyzed by Platinum Complexes Modified with Trisulfonated Triphenylphosphine in Aqueous Media
In this thesis we study the selective hydrogenation of polyunsaturated methyl
esters of linseed oil (MELO) to their monounsaturated C18:1 esters with a low
content of trans-C18:1 isomers catalyzed by water soluble platinum catalyst
modified with the sodium salt of trisulfonated triphenylphosphine (tppts) in
aqueous/organic two phase systems. In the Pt/tppts catalyzed selective
hydrogenation of MELO high catalytic activities have been achieved under mild
reaction conditions to afford a turnover frequency (TOF) of 3000 h-1 at a
temperature of 60°C, 30 bar pressure, molar ratios of C=C/Pt=1000 and
tppts/Pt=12 and a concentration of 200 ppm of platinum in water. The product
obtained within five minutes of reaction time contains a very low amount of
0.7% of the undesired trans-C18:1 esters and a relatively high content of 33.6%
of the desired cis-C18:1 compounds which probably could be attributed to the
low isomerization activity of the Pt/tppts catalyst under these conditions in
the aqueous medium. With increasing tppts/Pt molar ratios decreases the
formation of trans-isomers whereas with increasing reaction times and
temperatures increases considerably the content of the trans-C18:1 esters. The
C=C units/Pt molar ratio has a pronounced and highly interesting effect on the
selectivity of the catalyst. The content of the undesired trans-C18:1 esters
decreased from 6.7 to 1.5% with increasing molar ratios of C=C units/Pt from
1000 up to 4000 with a high catalytic activity of TOF= 3730 h-1 at the low
temperature of 80oC.
Pt/tppts complexes are superior catalysts compared with their rhodium and
palladium counterparts regarding the selectivity on the hydrogenation reaction.
Pt/tppts catalysts yield a very low content of trans-C18:1 esters whereas with
the other metals much higher amounts of the trans-isomers were obtained.
Recycling experiments of the Pt/tppts catalyst showed that the catalytic
activity was lower in one consecutive run.
Hydrogenation , Methyl esters of linseed oil, Trans-isomers, Water soluble platinum complexes, Aqueous/organic two phase systems