Catalysts for conversion of synthesis gas

A more comprehensive exploitation of biosources could be assured by the conversion of biofuels to valuable chemicals. The syngas, obtained by hydrocarbons reforming process, represents the most important reactants mixture for other processes devoted to the production of methanol, higher hydrocarbons (Fischer-Tropsch synthesis), and ammonia.The first two processes are very similar, since they involved main components of syngas in exothermic processes in which a more complex compound is achieved; they are promoted at high pressure and low temperature, for which anyway other side reactions occur (mainly methanation), and each reaction could be considered side-reaction for the other. Such observation remarks the relevance of the catalytic system that should enable desired reactions in the selected operating system. In particular, the Fischer-Tropsch synthesis is widely carried out on cobalt-based catalysts at low temperature, achieving long-chain hydrocarbons as main products; conversely, if low chain is preferred, iron-based catalyst could be employed. Methanol catalysts were effectively developed in the 1960s, in which Cu-ZnO-based formulations appeared very promising both in terms of activity and selectivity.Ammonia synthesis utilized hydrogen obtained by syngas purification (WGS, PROX, and PSA), reducing nitrogen to NH3: such process is thermodynamically promoted at low temperature and high pressure. Iron catalysts are currently used in industrial plants. For all these processes, the very high operating pressure was reflected in a limited catalyst lifetime, so nowadays, studies are focusing in the ability to enlarge catalyst lifetime, by doping active phases or supports.Globally, the exothermic nature of these processes suggests to investigate the effect of highly thermal conductive structured carrier, in order to have a better thermal management in the catalytic volume that could reduce hot spot risks and in turn assure a more stable behavior.