1-olefins Schulz-Flory type distribution

Titanium and zirconium based catalysts oligomerize ethylene into a mixture of a-olefin ranging from C4 to C30 with a Schulz—Flory type distribution. The content of linear a-olefin is nearly 100% provided conversion is low enough (a high concentration of ethylene has to be maintained during the whole reaction). 

The catalytic single-step Alfen process has a good space-time yield, and the process engineering is simple. The molecular weight distribution of the olefins of the single-step process is broader (Schulz-Flory type of distribution) than in the two-step Alfen process (Poisson-type distribution) (Fig. 2). As a byproduct 2-alkyl-branched a-olefins also are formed, as shown in Table 6. About... 

From Table 2 it can also be observed that the selectivity towards different hydrocarbon groups strongly depended on the acid properties of solids. Large amounts of C4 and C6 olefins were obtained for the mesoporous NiMCM-41 and NiMCM-48 catalysts with the lowest acid site concentration. In this case, a near Schulz-Flory-type product distribution (C4>C6>C8>Cio) was observed. The increase in acid site density (for the catalysts NiY, NiMCM-36, NiMCM-22) results in decrease of C 6/C8 ratio. These results are in agreement with the reaction network proposed in Scheme 1. 

Metals such as Fe, Co, Ni, or Ru on alumina or other oxide supports convert CO and H2 to hydrocarbons. Using different catalysts and reaction conditions either CH4, liquid hydrocarbons, high molecular weight paraffins, methanol, higher alcohols, olefins, and aromatics can be obtained, though rarely (with the exception of CFL, and methanol) with high selectivity. Hydrocarbons typically exhibit a Schulz-Flory type molecular weight distribution. 

The nickel concentration in the catalyst system is in the range 0.001-0.005 mol %. The oligomerization is carried out in a series of reactors at temperatures of 80-140 °C and pressures of 7-14 MPa. The rate of the reaction is controlled by the rate of catalyst addition [38]. A high partial pressure of ethylene is required to obtain good reaction rates and high product linearity [30]. The linear a-olefins produced are obtained in a Schulz-Flory type of distribution with up to 99% linearity and 96-98 % terminal olefins over the whole range from C4 to C30+ (cf Table 4) [21]. 

The catalysts belonging to the second class are especially reactive towards ethylene, and afford mixtures of nearly pure linear a-olefins ranging from C4 to C30 (chain length distribution of the Schulz—Flory type). These do not catalyze a double-bond shift. 

Deviations from the Schulz-Flory distribution arc possible if secondary reactions such as cracking on acidic supports or insertion of product olefins into the growing chain occur [42]. It has been reported recently that the Schulz Flory constant a has a tendency to increase from C3 to C, [45]. This may be the reason why the values found are usually higher for methane and lower for Cj and C) j.)., as would be expected for an ideal Schulz-Flory distribution [40]. Investigations by Madon et at. on partly sulfur-poisoned iron/copper catalysts revealed a dual product distribution. This was explained by the assump tion of > 2 types of active sites for hydrocarbon chain formation, each with a slightly different value of the chain growth probability [46]. 

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