You can't get both carboxylic acids and phenols at the same time - you need to focus on one or the other and it will depend on the feedstock, ash content and composition.

Your choice of catalyst depends on what you are trying to make, while the conditions are very important, including temperature, solvent and overpressure (if any). As a very general rule I have found phosphates at neutral pH preferable because by going supercritical you usually get total liquefaction. It is worth while separating the phenolic products from the rest and using them as a solvent for the following run because phenolics can retain the liquid state at supercritical water temperatures, but the ratio of the various components will vary the product slate.

In my work Desorption of phenol

Article Desorption of Furfural from Bimetallic Pt-Fe Oxides/Alumina Catalysts

You can find at least one approach to the best oxide catalyst to phenol.