MECHANISMS OF DEGRADATION OF HYDRATE YIELD INHIBITORS BY WET OXIDATION

Organic compounds with adjacent hydroxyl groups inhibit gibbsite (“hydrate”) precipitation. These hydrate yield inhibitors can be degradation products from the breakdown of larger organic molecules extracted from bauxite ore in digestion. It has been shown previously that yield inhibitors are readily destroyed at high temperature with or without oxygen.

This study investigates the reaction mechanisms of degradation of a set of known hydrate yield inhibitors in alkaline aluminate solutions by aerobic and anaerobic thermal degradation. The appearance of reaction products was monitored. Sodium oxalate was found to be the main organic degradation product from wet oxidation of the hydrate yield inhibitors studied. A reaction mechanism involving base-catalysed oxidation by water is proposed. This mechanism explains the formation of the degradation products observed. It also explains oxidation of organics in the absence of oxygen, and why it is that hydrogen is produced even in the presence of oxygen.