Heterogeneously Catalyzed Partial Oxidation in Supercritical Water

Abstract

A continuous high‐pressure plant for heterogeneously catalyzed partial oxidation in supercritical water is described. This plant features a differential loop reactor using the jet loop principle. In this apparatus, the partial oxidation of methanol to formaldehyde was first examined without catalysts in the parameter range 390 to 450 °C and 22 to 35 MPa. Then, metallic silver, copper and a gold/silver alloy were tested as catalysts under the same reaction conditions. The experiments showed that heterogeneously catalyzed partial oxidation in supercritical water is practicable with this plant.

Lewis Acids: From Conventional Homogeneous to Green Homogeneous and Heterogeneous Catalysis

“…231 The same applies for basecatalyzed reactions. 232,233 Among the classes of reactions for which supercritical water is particularly suitable as reaction medium, the most important are hydrolysis, 234,235 hydrations/dehydrations, 236-240 pinacol 241,242 and Beckmann rearrangements, 231,242,243 Diels-Alder cycloadditions, 244 Friedel-Crafts phenol alkylation, 245 and more surprinsingly oxidations [246][247][248] and degradation of organics. [249][250][251] Compounds such as ammonia, 252 phenols, [253][254][255][256][257] anilines, 258,259 pyridines, 260,261 chlorinated aromatics, [262][263][264][265][266] dibenzothiophenes, 267 and carboxylic acids 251,268 can be degraded in supercritical water.…”

“…Among the classes of reactions for which supercritical water is particularly suitable as reaction medium, the most important are hydrolysis, , hydrations/dehydrations, − pinacol , and Beckmann rearrangements, ,, Diels−Alder cycloadditions, Friedel−Crafts phenol alkylation, and more surprinsingly oxidations − and degradation of organics. − Compounds such as ammonia, phenols, − anilines, , pyridines, , chlorinated aromatics, − dibenzothiophenes, and carboxylic acids , can be degraded in supercritical water. The last reaction type has led researchers to consider supercritical water for the treatment of wastewater streams. ,,, In this case, the addition of some solid as oxidation catalyst, very frequently containing noble metals, can increase the overall efficiency of the process.…”

Catalytic Hydration of Propylene with MoO3/Al2O3 in Supercritical Water

“…Enhancement of the reaction rate by the acidic character of supercritical water has also been reported in Beckmann and pinacol rearrangements, hydrolysis reactions, and Diels−Alder reactions . However, chemical synthesis with a heterogeneous catalyst in supercritical water has been investigated by very few researchers. , …”

Ancillary Techniques in Laboratory Units for Testing Solid Catalysts

“…Examples are the thermal generation of oxygen (and water) from aqueous hydrogen peroxide solutions [18] and the catalytic formation of hydrogen (and carbon dioxide) from formic acid, e.g. The stoichiometry of the reaction determines the composition of the components in the feed stream.…”