Hexane hydrocracking

Figure 1. Effect of temperature on isohexanes/n-hexane hydrocracking of California gas oil...

For example in Fig. 12, the n-hexane hydrocracking reaction network—the last which can be drawn entirely by hand—contains 6 paraffins, 14 olefins and 10 carbocations, and involves the following elementary reactions ... 

Figure 9 Effect of Pt content in Pt /H-MOR and Pt/BEA Catalysts on n -Hexane Hydrocracking...

Figure 13.36 Dimethylbutane n-hexane selectivity ratios from hydrocracking of n-hexadecane over various framework types [75].

It is significant that the mixture yielded propane as the major product (Table III). As noted in our earlier paper on catalytic cracking (6), the predominance of C3 fragments in the cracked products and the absence of isobutane appeared to be a unique property of erionite. Our present data indicate that this is also true for hydrocracking over a dual function erionite. The only exception was that when n-pentane alone was hydro-cracked, equimolal quantities of ethane and propane were found. This shift in product distribution in the presence of n-hexane, a second crackable component, indicated that the reaction path within the intracrystalline space was complicated. 

In view of the complicated reaction kinetics of multicomponent systems, it was not clear whether or not the diffusional effects would also affect the relative rate of conversion of feed molecules in a mixture. To answer this question we studied the hydrocracking of three multicomponent systems. The first was a C5-C8 mixture, a C5 360° C boiling range midcontinent reformate which contained 12.5 wt % n-paraffins including 4.2% n-pentane, 4.3% n-hexane, 2.9% n-heptane, l.l%n-octane, and <1% C9+ n-paraffins, with the remainder isoparaffins and aromatics. The reaction was carried out at 400 psig, 2 H2/HC, 2 LHSV, and 800°F. Secondly, a Cg-Cie mixture... 

A study is presented of the synthesis and properties of the novel synthetic zeolite omega. The synthesis variables and kinetics of formation are discussed, as well as the ion exchange, sorption, and thermal properties. By decomposition of imbibed tetra-methylammonium ions and exhaustive treatments of the zeolite with ammonium ions, a pure hydrogen form can be obtained which is a suitable substrate for the preparation of hydrocarbon conversion catalysts. Several catalysts were prepared and utilized to isomerize n-hexane, and to hydrocrack a heavy gas oil. 

Ideal hydrocracking of alkanes requires a minimum of seven carbon atoms. This may be derived from Figure 9 in which distributions of the cracked products are compared that were gained with n-hexane (left hand side) and three of its higher homo-... 

According to the reaction scheme shown in Figure 5 both hydroisomerization and hydrocracking of the n-alkanes (except n-hexane) proceed via branched alkyl carbenium ions. In the range of medium degrees of conversion (40 % <,X <, 90 %) both reactions may be investigated simultaneously. A relationship between the products of both types of reaction will be discussed in the present section. 

Figure 9. Hydrocracking of n-hexane and different n-alkanes at low degrees of conversion. Distribution of the cracked products.

No. 2 and 3 seem to be more appropriate to explain the finding that n-hexane is excluded from ideal hydrocracking. 

The chain length of n-alkanes has a marked influence on reactivities for hydroisomerization, and especially for hydrocracking. To a very small extent a methane and ethane abstracting mechanism, probably hydrogenolysis as predicted in a basic work on bifunctional catalysis (14), is found to be superimposed when lower carbon number feeds (C, Cg, Cg) are used. n-Hexane is excluded from ideal hydrocracking. On the Pt/Ca-Y-zeolite catalyst it is cracked via a mechanism that is mainly hydrogeno-lytic. 

Previous results(2) had shown that a Pd-Ni-SMM catalyst was effective for hydrocracking hexane as well as a raffinate feed. Conclusions showed that this catalyst system when containing two nickel atoms per unit cell (15 wt % nickel) was approximately 15 times more active than a Pd-rare earth-Y zeolite catalyst and 1.2 times more active than Pd-H-mordenite. This same catalyst system (0.7 wt % Pd-15 wt % Ni-SMM) was chosen for our raffinate processing studies. 

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