13C-NMR Evidence for Hydrogen Supply by Water for Polymer Cracking in Supercritical Water

Abstract

A rubber polymer (EPDM, ethylene-propylene-diene-terpolymer) vulcanized was cracked to paraffinic oil (PO) in NaOH-containing supercritical water (SCW) at 420 °C and 30 MPa. The SCW polymer cracking in not oxidative but reductive. The 13C-NMR analysis of PO obtained by SCW D2O cracking demonstrates that the terminal methyl carbons are deuterated as a clear indication of hydrogen supply by SCW in the cracking.

Organic Chemical Reactions in Supercritical Water

“…Reaction with supercritical D 2 O provides a convenient alternate route to the synthesis of deuterated organic compounds. Deuterium was also present in the products formed from tert-butylbenzene pyrolysis 45 and polymer cracking 46 in supercritical D 2 O. These experiments clearly show that near-critical and supercritical water is not merely a solvent, but rather also a reactant, at least in hydrogen exchange reactions.…”

“…Supercritical water has been explored as a medium for the degradation of waste synthetic polymers. [46][47][48][49][50][51] Rubber tires were converted to a 44% oil yield by reaction in SCW at 400 °C. 50 Polystyrene-based ionexchange resins were subjected to SCW at 380 °C for 1 h. 49 Less than 5% of the polymer decomposed, and the products included styrene and several oxygenated arenes such as acetophenone and benzaldehyde.…”

Noncatalytic kinetic study on site-selective H/D exchange reaction of phenol in sub- and supercritical water

“…Thus sub-and supercritical water can be used as a novel and clean medium for chemical reactions of environmental and industrial importance. [10][11][12][13][14][15][16][17][18][19][20][21] In this study, we investigate the H/D exchange reaction on the phenyl ring of phenol in sub-and supercritical water under noncatalytic condition. The H/D exchange reaction is one of the simplest forms of chemical reaction, involving no substitution in functional groups, and is thus suited for the fundamental study of the nature of hydrothermal chemical reactions.…”

Decomposition of Prepolymers and Molding Materials of Phenol Resin in Subcritical and Supercritical Water under an Ar Atmosphere

“…However, they also reported that diarylalkanes such as diphenylmethane were not attacked by water. Recently hydrogen supply reaction and oxygen supply reaction of water were confirmed by 13 C NMR and the reaction product of a model compounds study of phenol resin, respectively. The presence of oxygen supply reaction suggested the participation of OH - ion to the reaction.…”