What are some examples of homogeneous catalysis?
The class of homogeneous catalysts is extraordinarily broad from the hydrogen (+) ion in acid catalyzed reactions like ester hydrolysis to natural enzymes (virtually all of them - an example is carbonic anhydrase - enzymes often have a metal iron surrounded by a vast protien complex but I think that it is not always necessary for a metal ion to be involved) to a variety of other noble metal catalysts like for example (chloridotris(triphenylphosphane)rhodium(I) or Wilkinson's catalyst used in hydrogenation of unsaturated alkene compounds, and transition metal organometallic compounds (some ziegler-natta catalysts for example dicyclopentadienyl dichlorides of Zn Hf or Ti - titanocene dichloride being the analog for titanium) soluble in water or organic solutions. I assume techically homogeneous catalysts could exist and function in other phases of matter but these solvent soluble catalysts are the ones that are most familiar to us. I have provided a few examples.. I think the field is probably much, much broader. I must apologize to Wikipedia for shamelessly and gratefully using them as a source for confirmation of some of these on short notice.
The thing that characterizes a catalyst from a simple reactant is that it becomes involved in reaction with another substance or substances but is itself regenerated as a product of that reaction.