Methane production by sequential supercritical gasification of aqueous organic compounds and selective CO2 methanation

In this paper, a catalytic process based on supercritical gasification of aqueous organic solutions coupled with a CO2 methanation reactor is proposed. Different catalytic systems have been investigated with the aim to obtain an outlet gaseous stream rich in methane. The stream at exit of supercritical reactor, mainly containing CH4/ CO2/H2, was used to feed a fixed bed reactor containing a catalyst to promote the selective hydrogenation of CO2 to methane. The results obtained under supercritical conditions clearly demonstrate that, with an appropriate catalyst, the gasification of diluted organic solutions allows to obtain an outlet stream containing about 50% CH4/40% CO2/10% H2. By feeding a fixed bed reactor, loaded with an efficient methanation catalyst, it has been seen that, even in presence of high methane contents, the CO2 is converted into methane obtaining, at the exit of the methanator, a stream containing a mixture close to the following composition, 60% CH4/38% CO2/2% H2, suitable to be used as a fuel to feed energy generator systems.