Isomerization of n‐hexane over nickel‐loaded zeolite catalysts

Abstract

The isomerization of n‐hexane to branched‐chain isomers was studied over various zeolite supports containing nickel between 1 to 5 wt%. NaA, NaY, CaY and Zeolon 900H were loaded with nickel by an impregnation technique. It was observed that at a nickel content of about 2.5 wt%, all the catalysts showed maximum activity for isomerization. A catalyst containing 1 wt% Ni/CaY gave the maximum selectivity among all the catalysts studied. Increasing the nickel loading beyond 2.5 wt% Ni with CaY and Zeolon 900H led to more hydrocracking. No major change in the activity and selectivity of Ni/NaA catalysts was observed beyond 2.5 wt% Ni, whereas the activity of Ni/NaY catalysts remained almost constant over the range of nickel content studied. A catalyst containing 2.5 wt% Ni on Zeolon 900H gave the maximum yield of isomers at 643°K. The apparent activation energy of the reaction was found to be 48.6 kJ/mol for 1 wt% Ni on Zeolon 900H catalyst.

Activity and selectivity of nickel-molybdenum/HY ultrastable zeolites for hydroisomerization and hydrocracking of alkanes

“…Another interesting feature which can be observed in the results of Table I is that the C6 + C5 + C4/Cx + C2 + C3 ratio is higher than 1. This result indicates that the C6, C5, and C4 fractions are not only produced by cracking or hydrogenolysis of C7 but also by other reactions involving consecutive alkylation-cracking processes, as has been observed during cracking of alkanes on Y zeolites (Bolton and Bujalski, 1971;Weisz, 1970;López Agudo et al, 1981). On the other hand, when hydrocracking is carried out on Pt or Pd/HYUS zeolite catalysts, the product distribution is perfectly symmetrical with respect to the number of carbons in the products (Weitkamp et al, 1983).…”

“…The formation of methane as a primary product is difficult to explain by an acid-catalyzed mechanism if we take into account that the production of methane involves primary carbonium ions and, moreover, no methane is observed as a primary product when the reaction is carried out on the purely acid HYUS zeolite (Corma et al, 1984). Therefore, we believe that, in this system, methane could be formed by hydrogenolysis on the metal part of the catalyst, while when catalysts containing noble metals are used, methane is not observed (Weitkamp et al, 1983; Weitkamp and Ernst, 1985;Jacobs et al, 1980;Martens et al, 1985). The isobutane/n-butane ratio can be taken as an indication of the relative rate of cracking by B (B1,B2) and C mechanisms (see Figure 4).…”

“…The reaction products obtained during hydroisomerization and hydrocracking on noble metals (Pt, Pd)/Y zeolite bifunctional catalyts have been largely covered in the literature (Steijns et al, 1981;Weitkamp et al, 1983;Gallei et al, 1981;Ribeiro et al, 1982;Weitkamp and Ernst, 1985;Giannetto et al, 1985;Weitkamp, 1982; Weitkamp et al, 1984;Jacobs et al, 1980). However, with non-noble metals (Ni, Mo), detailed work is scarce (Franck and Le Page, 1981;Jothimurugesan and Bhatia, 1984; Choudhary and Saraf, 1978).…”