A Comparative Inherent Safety Assessment of Innovative CO2-based Production Processes of Dimethyl Ether and Methanol

Dimethyl ether (DME) and methanol are proposed as synthetic fuels prone to substitute present fossil propellants in the energy transition framework. Methanol and DME are traditionally synthesised starting from syngas but nowadays new production processes based on the efficient catalytic hydrogenation of CO2 have been introduced. Multiple catalysts, reaction conditions and reactor configurations have been tested to enhance the production performance of both fuels, especially for the case of DME. In fact, DME can be produced indirectly from CO2, i.e. after methanol synthesis and purification. Alternatively, it can be synthesised in a one-pot conversion mode by means of bifunctional catalysts directly receiving CO2. The latter route, avoiding several intermediate separation operations, appears promising from the process intensification viewpoint, thus favouring DME production with respect to methanol. Since safety plays an important role from the standpoint of societal acceptability, it needs to be considered in the selection of sustainable alternatives. This contribution aims to address an inherent safety assessment of the processes for methanol and DME production via CO2 hydrogenation. Inherent safety is evaluated through a consequence-based approach using specific Inherent Safety Key Performance Indicators, which proved to be effective in several applications to early process design. The results obtained shed light on the inherent safety performance of these alternative routes, thus helping decision-makers in accounting for process safety issues in the assessment of the sustainability of these alternative energy vectors and in the selection of the best technological alternative.