The reactions of 2,2'-dinaphthyl ether and diphenyl ether were studied at 375-425 degrees C using 6.9 Mfa (cold) hydrogen or nitrogen, 9,10-dihydrophenanthrene (DHP) and decalin as solvents, and a molybdenum sulfide catalyst. We chose to examine these compounds as models for the cleavage of diaryl ether bridges during coal liquefaction. The molybdenum sulfide was added to the reaction as MoS3, which should transform to the active MoS2 catalyst. Cleavage of the C-ar-O in 2,2'-dinaphthyl ether, at reaction temperatures of 375 and 400 degrees C, proceeded in the sequence H-2 < DHP-N-2 < DHP-H-2 < DHP-MoS3-N-2 < DHP-MoS3-H-2 < MoS3-H-2 < Dec.-MoS3-H-2. At 425 degrees C, the MoS3-H-2 and Dec.-MoS3-H-2 systems exchange places in this order, Diphenyl ether is less reactive than dinaphthyl ether toward hydrogenolysis reactions under these conditions. The conversion rate of diphenyl ether increases in the order H-2 < DHP-H-2 < DHP-MoS3-N-2 < DHP-MoS3-H-2 < Dec.-MoS3-H-2 < MoS3-H-2, Although the rates of conversion of the two ethers are different, the relative effects of using a reactive gaseous atmosphere, donor solvent, catalyst - or some combination of these factors - are the same for both compounds, In liquefaction experiments, hydrogen donor solvent or hydrogen shuttling solvent seems necessary to reduce retrogressive reactions. However, a solvent interacting strongly with catalyst and scavenging hydrogen atoms can reduce the activity of catalysts in hydrocracking reactions.