Effect of support composition on the activity of Pt and PtMo catalysts in the conversion of n-hexadecane

Abstract

The SiO2Al2O3 material and mesoporous molecular sieves of AlSBA-15 type described in this work were applied as the supports for the Pt and PtMo catalysts. Catalysts were synthesized by one step impregnation, i.e. Pt catalysts with 1wt.% of Pt as well as by two step impregnation, i.e. PtMo catalysts with 4–8wt.% of Mo followed by 1wt.% of Pt. The activity of the catalysts was investigated in n-C16 conversion (5MPa; 320–370°C; WSHV, 3.5h−1; H2:CH, 350:1Nm3/m3) and in n-C7 conversion (0.1MPa; 350–370°C; WHSV, 1h−1; H2:CH, 10:1mol/mol). The results have shown that at comparable reaction temperatures, i.e. 340–360°C the catalysts containing AlSBA-15 are more active than the catalysts supported on SiO2Al2O3. Among the PtMo/AlSBA-15 catalysts, the catalyst containing 8wt.% of Mo provides the highest selectivity towards i-C16 and the highest iso/n proportion within C10–C15 fraction together with the maintenance of a high conversion. SEM examinations of PtMo catalysts have shown that type of support influences Mo distribution; agglomerates of Mo phases are observed on the AlSBA-15 containing catalysts. It was postulated that the weaker Mo–support interactions and higher acidity in AlSBA-15 supported catalysts resulted in a more active and selective catalyst for hydroconversion of n-hexadecane.