EFFECT OF HYDROGEN-SULFIDE ON THE REACTION OF 2,6-DIMETHYLANILINE OVER SULFIDED HYDROTREATING CATALYSTS

The reaction of 2,6-dimethylaniline was studied between 280-degrees-C and 320-degrees-C at 4 MPa on CoMo and NiMo/Al2O3 hydrotreating catalysts. The formation of dimethylcyclohexanes and dimethylcyclohexenes, of m-xylene and of o-toluidine plus mesidine gave access to three functionalities of the catalysts: hydrogenation, C-N bond cleavage and acidity. The influence of H2S on the activity and the selectivity of the catalysts was examined for H2S/H-2 molar ratios ranging from 0 to 0.07. The response of hydrogenation and of hydrogenolysis to H2S were similar: activity of both functions decreased up to about 1% H2S, and stayed constant beyond that value, while the acidity continuously increased with the H2S concentration. From these results, the distribution of active species originating from H-2 and H2S is discussed in relation with the reaction mechanism.