화학공학소재연구정보센터
Applied Catalysis A: General, Vol.327, No.2, 247-254, 2007
Non-sulfided nickel supported on silicated alumina as catalyst for the hydrocracking of n-hexadecane and of iron-based Fischer-Tropsch wax
Nickel(II) was introduced by wet impregnation onto a commercial silicated alumina (Siralox 40((R)), SiO2/Al2O3 mole ratio= 1. 1) and the physico-chemical properties of the calcined Ni/Siralox samples were determined by BET, H-2 chemisorption, O-2 back-titration and TPR. The latter technique showed that the nickel oxide species was predominantly associated with the alumina phase present in the Siralox support. Hydrocracking of a model compound, n-hexadecane, was carried out over the non-sulfided Ni/Siralox 40 catalysts at 345-360 degrees C, WHSV = 2.2 h(-1) and 55 bar. At an average conversion of 41.3% and up to 144 h on-stream, the 3.0% Ni/Siralox 40 catalyst (calcined at 300 degrees C) gave a product spectrum that closely resembled "ideal hydrocracking" and produced low C-1-C-2 selectivities (similar to 1.8 wt%). Increasing the metal loading to 4.5% resulted in an increase in the average metal crystallite size, and consequently, in higher C1-C2 selectivities of 11.5 wt%. Calcination of the catalyst precursor at 500 degrees C. however, afforded lower C-1-C-2 selectivies (3.1 wt%), but the extent of secondary cracking was higher. In the hydrocracking of the iron-based Fischer-Tropsch wax over the 4.5% Ni catalyst (at 360 degrees C, WHSV = 2.8 h-1, 70 bar, and using an H-2,/feed (1/1) ratio of 8.0 x 1 02), a diesel selectivity of 74.9% was obtained at a conversion of 51.6%. These results compare favourably with those obtained with a commercial sulfided NiMo/SiO2,-Al2O3 catalyst at 380 degrees C. The non-sulfided Ni/Siralox catalyst, however, exhibited a higher hydrogenolysis activity. (c) 2007 Elsevier B.V. All rights reserved.