You are taking about a PO420 Diagnostic code. I discussed this in the article. High Octane gasoline can help clear out the Catalytic Converter, and this has helped me, and people I know, avoid having to replace the unit. But it's no guarantee. If it's damaged enough, the check engine light will come back on again later.
It's a worthwhile thing to try since the cost of a tank of High Octane is much less than the price or replacement and labor. If it works, you might get a few more years out of it. I have.
Keep in mind, another thing that can be causing the OBD diagnostic code is a stuck sensor. If the light keeps coming back on with this code, then this should be considered too. I trustworthy mechanic should be able to determine this. But try the High Octane method, as I discussed in the article, before you start spending money on repairs.