from first principles PP-I-1

OP-III-4Effect of Metal-Support Interaction in Ni/ZSM-5+Al 2 O 3 Catalystson n-Paraffins TransformationMasalska A., Grzechowiak J., Jaroszewska K.Wrocław University of Technology, Faculty of Chemistry, Wrocław, PolandAleksandra.Masalska@pwr.wroc.plCatalysts NiO(8%)/Ni,H-ZSM-5+Al 2 O 3 (1:1) differing in metal-support interactions, whichinfluenced the metal-to-acid ratios, were examined. Interactions were controlled by themethod of zeolite and aluminium hydroxide combining and the method of Ni incorporation.Nickel(II) nitrate was used as a metal precursor. The catalysts were characterized by ICP,XRD, N 2 sorption, SEM, TEM, NH 3 -TPD, PY-IR, TPR, H 2 chemisorption and XPS. Theeffect of metal-support interaction was determined during n-C 6 conversion in a continuoussystem (H 2 :CH = 7:1 Nm 3 /m 3 , 0.1 MPa and LHSV=1h -1 ).Table 1. Catalysts under the study.CatalystcodeZSM-5& Al 2 O 3NiOdepositionnNi_a/nx 10 2a) b)A/F+I A F+I 4,8A/F A F 1.2E/I E I 2.7E/F+I E F+I 3.2Fig. 1. Yield of i-C 6 (a) and HBH (b).E/F E F 1.8 Catalysts: A/F+I (●), A/F (○), E/I (∆), E/F+I (□),E/F ()The activity results showed that the conversion of n-C 6 over the all investigated catalysts wassimilar (not show). Over the catalysts with a larger metal to acid ratio (n Ni_a /n – note: n Ni_a ,amount of accessible nickel atoms; n, amount of acid sites), where Ni was incorporated bymethod F+I (catalysts E/F+I and A/F+I), the yield of isomerization products was by 5–10 wt. %higher, and the yield of HBH (above n-C 6 ) by 10–30 wt.% lower than over the catalysts witha lower n Ni_a /n ratio, where the whole amount of Ni was incorporated before the step ofcatalyst forming (F) (catalysts E/F and A/F). It can be assumed that at a larger number of Niatoms, the isomerised carbenium ions can be hydrogenated and leave the catalyst surface priorto -scission. Despite the fact that E/I catalyst is characterized by relatively high nNi_a/nratio, the yield of isomerization product was low, while yield of HBH products was high,because dehydrogenation and cyclization of n-C 6 occurred over the "isolated" metal centers.Slightly higher yield of HBH over A/F (up to 300 °C) may be due to its lower reducibility,because of strong metal-support interaction. Synergetic effect between Ni 2+ ions (acting asLewis sites) and Brønsted sites increases the catalyst activity in aromatization of n-C 6 .47