CO2 and water can be electrochemically converted to the more valuable and industrially useful mixture of CO and H2 (syngas). However, as more CO2 is converted relatively more H2 is produced. Therofore, a tempting strategy is to use less catalyst downstream and produce relatively more of the desireable CO at lower catalyst costs.
We first made a simple model that we optimised for our self-defined “effectiveness” giving
On the left is the average CO2 reaction rate coefficient <k> times the residence time L/U. Here q is the ratio between the inlet CO2 and H2 reaction rate constants.
By using less catalyst downstream, <k> decreases and a smaller residence time is better. However...the same effectiveness is obtained!
A similar conclusion is obtained for a more elaborate model including more physical and economical complexity. For a given residence time the catalyst distribution can be optimised using our freely available Matlab script. But in this case the improvements in effectiveness can be larger than those obtained by simply increasing the residence time, while at the same time using less catalyst!
