If you want to get up to date with any type of research, it's best to start reading review articles. They overview what people have been trying. I don't know anything about hydrodesulfurization (HDS), but I'd recommend looking for review articles on the subject. You might have to be more specific (ie. review of HDS by <enter catalyst type>). I couldn't find anything good on a quick look, but here might be something to start with:http://www.sciencedirect.com/science/article/pii/S0920586104004705
Seems that it's an article comparing the kinetics of a variety of HDS catalysts.
If you are looking to get more into transition metal catalysis in general, I recommend finding a good book and start reading about it. I wish I had a good book to recommend, but I don't at this time. "Transition metal catalysis" is a really broad term--it contains everything from small molecule activation, olefin metathesis, hydrogenations, bond coupling reactions, etc. so it's really hard to sum things up.
Well, I hope something I said helps you out! If there's anything about the conceptual aspects of transition metals, catalysis, etc. that you are confused about, please ask away--I hope someone else or myself can give you an answer!