Pt, Ir and Pd promoted Co/MSU catalysts for hydrotreating of tetralin: A thiotolerance study

Cobalt based catalysts doped with noble metals (Pt, Ir or Pd) supported on Zr-MSU type materials were studied in the hydrogenation and hydrogenolysis/hydrocracking of tetralin at different temperatures. Sulphur tolerance was studied in order to evaluate the possible application of these catalytic systems in second stage processes. The catalytic test was carried out in a high-pressure fixed-bed continuous-flow stainless steel catalytic reactor operating at a pressure of 6.0 MPa. Textural, structural, acidic and metallic properties were studied by XRD, XPS, H2-TPR, NH3-TPD, O2 chemisorption measurements, TEM and elemental chemical analysis. Three catalysts were prepared with 10 wt% of cobalt and 0.5 wt% of noble metal (Pt, Pd or Ir). Moreover, other three monometallic noble based catalysts (0.5 wt% of noble metal) were prepared to demonstrate the improvement found in the bimetallic ones. The results indicate that the presence of a noble metal in cobalt catalysts, especially Pt, improves their catalytic properties in hydrogenation reactions with or without dibenzothiophene (DBT) in the feed by operating not only at low contact times, but also at low H2/THN molar ratios. The conversion values and the yield of hydrogenation products were higher for noble metal doped catalysts at all temperatures studied; meanwhile, the yield of hydrocracking and hydroisomerization compounds is appreciable at higher temperatures, especially for platinum and iridium catalysts, despite the formation of considerable amounts of undesirable naphthalene. The platinum promoted catalyst displays very good properties when DBT is added to the feed. After 10 h on stream, with 600 ppm of DBT in the feed and at 315 °C, it was found to maintain its high conversion of tetralin (90.5%) and a yield of hydrogenation products of 82.2%.