the ceramic in a automotive catalytic converter is not coated but also if not visible on first sight the ceramic is porous for to provide a large surface. On this surface particles of metal (most palladium, platinum and rhodium sometimes rhuthenium at least Pd or Pt) are deposited. Clusters of a few atoms of metal to small to be seen without an (electron)microscope. The way the noble metal was deposited on and in the pores of the ceramic and the additionally used promotors, most other metaloxides or compounds, is essential for the working of the catalyst, what he catalyses, at what temperature and the fot the specified activity.
So you have an old automobile catalytic converter which was designed mainly for gasphase oxidations at temperatures of 350°C and up. It is now worn out mostly inactive and poisoned. Also if new it wouldn´t have catalyzed a hydrogenation in liquid phase below 100°C. Because it is not made to do this. Nowadays these converters are highly spezialized devices made to fulfill one task with the minimum of noble metals needed. What you want is driving a submarine on the highway.
If you can get hand on a old
unused converter from the time they got usual somewhere in the 80´ies I guess, this might be worth a try as these days the problem was solved by using a lot of palladium what was quite cheap. A small chance I say but a chance. A newer model for hydrogenation: plain forget it.
Nowadays a new converter might be useful for oxidations in the gas phase at elevated temperatures, those which are made of three blocks at least. They could be very useful for this I believe. But this says furnace tube and is regarded as one of the deadly sins at the HIVE (together with microwaves, pressure and else).
I will go now and whip myself for having named it.
ORG