Hydrogenation isooctenes

CDTECH/Snamprogetti SpA Isooctene/isooctane Mixed C4 hydrocarbons Isobutylene diemrization to produce isooctene. Additional process can hydrogenate isooctene to produce isooctane 2 1999... 

In other instances, reaction kinetic data provide an insight into the rate-controlling steps but not the reaction mechanism see, for example, Hougen and Watson s analysis of the kinetics of the hydrogenation of mixed isooctenes (16). Analysis of kinetic data can, however, yield a convenient analytical insight into the relative catalyst activities, and the effects of such factors as catalyst age, temperature, and feed-gas impurities on the catalyst. 

Numerous examples of applications of nonlinear least squares to kinetic-data analysis have been presented (K7, K8, L3, L4, M7, P2) an exhaustive tabulation of references would, at this point, approach 100 entries. Typical results of a nonlinear estimation and comparison to linear estimates are shown in Table I and discussed in Section III,A,2. Many estimation problems exist, however, as typified in part by Fig. 7. This is the sum-of-squares surface obtained at fixed values of Ks and Ku in the rate equation used for the catalytic hydrogenation of mixed isooctenes (M7)... 

Fig. 7. Contours of sums of squares of residual rates for isooctene hydrogenation, Eq. (46).

A scheme which was considered by Hougen and Watson (18) and is slightly more complicated is the hydrogenation of isooctene codimer. This illustrates a reaction with a large number of cycles compared with the number of intermediates. 

A supported nickel catalyst was used to study the reaction in which mixed isooctenes, commercially known as codimer, are hydrogenated in the vapor phase to the corresponding isooctanes. Neglecting isomerization, the following steps are assumed to occur ... 

Olefin Dimerization. Other investigators (Schaad, 1955, Sparks et al., 1939) have reported that the catalytic polymerization of isobutene produced a liquid polymer consisting mainly of isooctenes. Hydrogenation of these isooctenes gave isooctanes consisting of 70 to 90 percent 2,2,4-trimethylpentone the remainder was reported as mainly 2,3,4-trimethyl-pentane. That earlier work used analytical techniques inferior to those now available. Typically, It Is now found that the C0 fraction of Isobutene-isobutane alkylate catalyzed by HF contains about 62.6 percent 2,2,4-trimethylpentane, 13.4 percent 2,3,4-trimethylpentane,... 

The aldehydes and alcohols produced are a mixture of normal and iso-compounds. This is due not only to the orientation of the hydrogen with respect to the C-CO bonds in the initial reaction complex but also to the isomerization of the olefin under the process conditions. It may be significant that nickel carbonyl does not readily shift the olefin double bond under the 0X0 process conditions, and nickel compoimds are very poor catalysts for the process. From isooctene 32% n-nonyl alcohol, and from propylene 50% n-butyl alcohol are obtained, the remainder of the products being isoalcohols. In general, using a-olefins as raw material, one obtains about 60% isoalcohols. The synthesis will not occur unless a labile hydrogen atom is available in the olefin reactant. With diolefins the reaction takes place at only one double bond. 

A classical example of this method is the study of the hydrogenation of isooctenes of Hougen and Watson [27]. By considering all possible mechanisms and rate determining steps they set up 18 possible rate equations. Each equation was confronted with the experimental data and the criterion for acceptance of the model was that the parameters ki, K, ..., had to be positive. In this way 16 of the 18 possible models could be rejected. The choice between the seventeenth... 

Sarkar A, Seth D, Ng FIT, Rempel GL. Kinetics of hquid-phase hydrogenation of isooctenes on a Pd/y-alumina catalyst AIChE J. 2006 52(3) 1142-1156. 

The process of hydrogenation may be utilized in adding hydrogen to unsaturated hydrocarbons. For many years it did not find wide application because most oils are already saturated with hydrogen to a sufficient degree. However, during World War II it was applied to isooctene to produce isooctane and more recently it has been used in the desulfurization processes of pages 305 and 332. 

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