Oligomerization of propene

In contrast, data on the characterization and the catalytic properties of hafnium surface complexes are very scarce [42, 43]. Yet, some papers describe the hafnium complexes as more active than the zirconium analog, in the polymerization of ethylene [44], more selective in the oligomerization of propene [45, 46] and faster... 

Martens et a/. 3S showed that HZSM-22 synthesized in a pure form with controlled crystal size is a promising catalyst for the oligomerization of propene to Q-C12 olefins. It was found that the reaction occurs at or near the outer surface and the products formed are mainly dimers. In addition, an increase of the linearity of the oligomers as compared with HZSM-5 or solid phosphoric acid was found. It was tentatively proposed that active sites located at the pore mouths are responsible for this shape selective effect. 

A catalyst based on the mesoporous molecular sieve MCM-41 aluminosilicate has been used for the oligomerization of propene and butenes[51-53] at low temperatures (between 353 and 473 K). The catalyst shows higher activity and selectivity for the formation of trimers and tetramers as compared with HZSM-5 and HZSM-23. 

Kim and Inui[54] have reported the synthesis of MCM-41 with incorporation of various metal components such as Al, Ga or Fe with different Si/metal ratio. These catalysts were used for the oligomerization of propene, and it was found that the order of activity was Al-MCM-41 > Fe-MCM-41 > Ga-MCM-41 with the optimum Si/metal ratio being equal to 200. The propene conversion increases with the temperature from 423 up to 523 K. The catalytic activity of mesoporous silicates was lower than zeolitic catalysts, such as MFI metallosilicates. However,... 

UNUSUAL REGIOSELECTIVITIES OBSERVED IN THE OLIGOMERIZATION OF PROPENE ON NICKEL(II) ION-EXCHANGED SILICA-ALUMINA CATALYSTS... 

Unusual Regioselectivities Observed in the Oligomerization of Propene on Nickel(II) Ion-exchanged Silica-Alumina Catalysts 226... 

Summarizing the experimental observations, it follows that (i) no change in the spectrum of adsorbed benzene was detected with increasing loading and adsorption temperature and no irreversible consumption of benzene was found at 453 K. (ii) Very fast oligomerization of propene occured even at room temperature. With increasing temperature above 473 K, intensive formation and decomposition of unsaturated carbenium ions was detected. A broad IR... 

Described in this paper is a model system - one in which well-characterized lanthanide complexes exhibit high catalyst activities for ethylene polymerization but where the corresponding oligomerization of propene is sufficiently slowed so that stepwise insertion of the olefin can be studied quantitatively and all important intermediates observed or isolated. Emphasized in this paper is the effect of added Lewis acids and bases on the rate of olefin insertions, and comparison between ethylene and propene reactions. The catalysts, of general structure M(ri -Cp )2CH3 L (M = Yb, Lu ... 

It was found that 16 exhibited regiospecific oligomerization of propene, 1-butene, and 1-pentene to yield linear atactic polymers as head-to-tail coupling of monomer units is favored by this catalyst [33]. The polymer chain grows by a P-hydride elimination mechanism, which competes with phosphine coordination, leading to a relatively... 

Low Molecular Weight Alkenes by Asymmetric Oligomerization of Propene and 1-Bntcnc Typical Procedure 7 ... 

This method provides a straightforward access to chiral alkyl-substituted 1-alkenes via asymmetric oligomerization of propene or 1-butene. Products of this type are of interest for the synthesis of pheromones and other modestly functionalized chiral compounds. 

These materials, which were initially designed as large-pore zeolites, are not strongly acid but are, rather, quite effective as mild acid catalysts [4], catalyzing reactions such as the oligomerization of propene [5,6] and butene [7], the alkylation of aromatic hydrocarbons [8-10], the acylation of activated aromatics... 

HZSM5 zeolites catalyze the transformation of propane aromatic products. This aromatization requires various steps of propene, oligomerization of propene, cyclization of oligomers and hydrogen transfer from naphtenes to olefinic compounds with formation of aromatics. The cracking of Cg-Cg oligomers leads to C2-C5 olefins which, like propene, participate in the formation of aromatics. 

The peak at 250 ppm is indicative of three-coordinate carbenium ions [64]. A resonance at 250 ppm, observed in an in situ study of the oligomerization of propene on zeolite HY at low temperatures, was assigned to alkyl-substituted eyclopentenyl cations [37]. In that paper, the 250 ppm resonance was assigned to... 

Previous work of O Connor on high pressure oligomerization of propene over different zeolites, heterogeneous phosphoric acid, incorporated acids in clay, and nickel on different supports revealed that the major product in all cases was trimers. The catalyst systems referred to in the text may also be found in Table 2 (page 252). 

The ratio of intra-crystalline acid sites to external surface active sites in zeolites tends to increase with crystal size due to the geometric relation between volume and external surface area. Also, how varying the Si-Al ratio in the ZSM-5 catalyst affects crystal size in the oligomerization of propene has been investigated. The optimum Si-Al ratio was about 20, which yielded the best lifetime and activity. 

Crystal size and purity of HZSM-22 were controlled by the addition of seed during crystallization. The authors used the pure HZSM-22 in oligomerization of propene and, according to their activity measurements, the active sites for oligomerization were located near the zeolite external surface. ... 

In the oligomerization of propene over aluminosilicate HZSM-22 and ZSM-5 catalysts, the yields of lubricant-quality fraction were 21 and 18 wt%, respectively. In propene oligomerization with NH4Cl-exchanged ZSM-22 catalyst the conversion increased from 53 to 79% by increasing amount of added water from 0.02 to 0.15mole%. ... 

The selectivity of the different zeolite systems to produce the lube oil fraction was examined in oligomerization of propene. The lube fraction of the product from oligomerizing propene with a ZSM-5 type catalyst generally has the feature of a low pour point ( —50°C) and low viscosity index (79). The lubricant-range hydrocarbons produced from the oligomerization of propene over HZSM-22 at about 240 °C had a viscosity index of 85. ... 

The coordination sites contributed to the dimerization of ethylene, while oligomerization of propene proceeded both via coordination and acidic sites. However, but-l-ene only oligomerized via acidic sites. 

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