A Preliminary Assessment of Sorption-Enhanced Methanol Synthesis in a Fluidized Bed Reactor with Selective Addition/Removal of the Sorbent

Abstract

Methanol synthesis from CO2 can be made in the presence of a sorbent to increase the achievable yield. If the fresh sorbent is continuously fed to a fluidized bed and separated from the catalyst bed by segregation, a steady-state operation can be achieved. The objective of the present work is to provide insight on the suitable operating conditions for such a fluidized bed reactor system. For this, a conventional CuO/ZnO/Al2O3 was selected as the catalyst, and the SiOLITE® zeolite was selected as the sorbent. Different particle sizes were used to be tested in various proportions to perform the fluidized bed segregation study. The fluid dynamics and segregation of the catalyst–sorbent binary mixtures were the most critical points in the development of this proof of concept. A good bed segregation with a mixing index of 0.31 was achieved. This fact favors the correct operation of the system with the continuous addition of adsorbent, which had hardly any catalyst losses during the tests carried out, achieving a loss of 0.005 g/min under optimal conditions. Continuous feeding and removal of sorbent with a low loss of catalyst was observed. Reactor simulations with MATLAB provided promising results, indicating that the addition of sorbent considerably improves the methanol yield under some operating conditions. This makes it more viable for industrial scaling, since it allows us to considerably reduce the pressure used in the methanol synthesis process or to increase the yield per step, reducing the recirculation of unconverted reactants.