Up-Grade of Catalysts for Medium and High Temperature Water Gas Shift Reaction

Abstract

The Water Gas Shift (WGR) reaction plays a fundamental role in the production of H2 or syngas, which are widely used in the chemical industry to produce building blocks or fuels. Considering the very large global request of these molecules, each improvement in the WGS processes generates a huge return on investment for the industries and for this reason, this reaction is still under investigation. This PhD thesis aimed to upgrade the Medium and High Temperature Shift process by improving the catalytic formulations or finely tuning the reaction conditions. For the MTS formulations, the introduction of small amounts of elements such as La, Zr and Ce resulted in a significant improvement of the physical properties, with a corresponding increase, especially in case of Ce, of the CO conversion and the catalyst stability. On the other hand a small amount of Mg increases the stability and the catalytic performances, while the same amount of Ba does not affect the catalytic behavior. Finely, the role of the different reaction parameters on the methylamine formation and, consequently, on the deactivation by carbonaceous deposits was proposed. Novel catalyst formulations were successfully obtained also in case of HTS, favoring the economic items of this process, with a strong increase of CO conversion and very low deactivation with time-on-stream by addition of very small amounts of Ga. This effect was attributed to the tendency of Ga to favor the formation of spinel-type phases that stabilized the metallic copper, resulting in a decrease in particle sizes. The high stability of Cu- and Ga-containing spinel-type phases and their controlled reduction are the key factors to favor the catalytic activity and reduce the copper sintering, main cause of catalyst deactivation.