Chemie in überkritischem Wasser

Abstract

Wasser ist ein besonderer Saft – nicht nur unter „normalen”︁ Bedingungen. Wasser im überkritischen Zustand (gerasterte Fläche im Phasendiagramm) zeichnet sich durch Eigenschaften aus, die von denen des normalen Wassers erheblich abweichen. Bisher wurden diese meistens zur Abwasserreinigung, z. B. zur Totaloxidation schwer abbaubarer Stoffe, genutzt. Doch wie sieht es mit dem Synthesepotential von überkritischem Wasser aus? Antworten werden hier anhand von thermodynamischen und kinetischen Untersuchungen sowie von Korrosionsmessungen gegeben.

Organising and running a pump service in The Netherlands

“…Recently we reported an interesting finding that scH 2 O itself successfully functions as an acid in accelerating pinacol/Beckmann rearrangements 3. Bröll et al have briefly reported a base‐catalyzed Cannizzaro‐type disproportionation of formaldehyde in scH 2 O carried out without a base catalyst 4. In addition, our in situ Raman spectroscopy measurements have indicated that the extent and strength of hydrogen bonding of scH 2 O are very different to those in heated and ambient H 2 O 5.…”

Heterogeneously Catalyzed Hydrogenation of Supercritical CO2 to Methanol

“…The view cell setup was already described in . As feed, a synthetic product stream was generated simulating a conversion of CO 2 of 50 % and a selectivity to CH 3 OH of 67 %.…”

Application of Dicyclohexyl‐(S)‐trimethoxyphenyl Phosphine⋅HBF4 Salt for the Highly Selective Suzuki Coupling of the CCl Bond in β‐Chlorobutenolides Over the More Reactive Allylic CO Bond

“…Evaporation of the water in the biomass is avoided when working above the critical pressure of pure water (that is, at p >22.1 MPa). Near‐ and supercritical water is a green solvent that may replace organic solvents for a number of organic syntheses 5. We have shown that waste biomass can be catalytically converted to Bio‐SNG in supercritical water.…”