Here is what Vogel (3rd Ed.) says about using manganous oxide for the production of methyl benzyl ketone from PAA and GAA:
IV,140 Methyl Benzyl Ketone
Use the apparatus as described in Section III,72 and adjust the furnace to a temperature of 400-450° (centigrade). Although a manganous oxide catalyst gives satisfactory results, thoria is more convenient in practice.
The procedure then goes on to describe the preparation of the thoria catalyst and preparation of the P2P in about 50% yield based on the PAA.
Preparation of the manganous oxide catalyst is described in section III,72 for the preparation of dialkyl ketones from acids in the tube furnace.
Here is what Section III,72 says about preparation of the catalyst:
Fill a Pyrex tube, 100 cm long and 1.5 cm internal diameter, with pumice (4-8 mesh). Transfer the pumice into a thick suspension of about 40 grams of freshly precipitated manganous carbonate in a beaker. (The managanous carbonate is prepared by adding a solution of 38 g. A.R. anhydrous sodium carbonate to a solution of 70 g. of A.R. crystallised manganous chloride, and filtering). Heat the beaker on a hot plate with vigorous stirring with a glass rod until most of the water is expelled, then transfer the solid to a shallow porcelain basin and continue the heating, with stirring, until the lumps no longer cling together; take great care to avoid local overheating. It is important to adjust the volume of water used in preparing the suspension of manganous carbonate so that most of the latter is absorbed by the pumice; if much water has to be evaporated, the manganous carbonate does not adhere satisfactorily.
