Bifunctional conversion of n-decane over HPW heteropoly acid incorporated into SBA-15 during synthesis

Abstract

SBA-15 ordered mesoporous silica materials containing up to 40 wt.% of HPW heteropoly acid were synthesized via an original method involving the introduction of HPW in an acidified solution of P123 tri-block copolymer (EO 20PO 70EO 20), the SBA-15 mesostructuring agent (direct synthesis). Samples with similar HPW loadings were also prepared by impregnation of SBA-15. Characterization by XRD, 31P MAS NMR, NH 3-TPD, and N 2 adsorption showed that even after calcination HPW in the direct synthesis samples was better dispersed than that in the impregnated samples. SBA-15-supported HPW materials were converted into bifunctional catalysts. In the conversion of n-decane, direct synthesis samples were superior to impregnated samples. The criteria of ideal bifunctional catalysis were fulfilled, e.g. high yields of skeletal isomers (>70%), of multi-branched skeletal isomers, and of branched cracked products, and hydrocracking reactions limited to primary cracking. Compared to ultrastable Y zeolites, the HPW/SBA-15 samples showed a broader optimum reaction temperature window for isomerization and higher n-decane dibranching selectivity.