Oligomerization of Propylene

The propylene oligomerization literature is considerably poorer than that for the ethylene oligomerization. The catalysts for oligomerization of propylene are also active in ethylene oligomerization. Also in this case, the titanium, zirconium, and nickel complexes are the most popular catalysts. Propylene oligomers are more structurally diverse than ethylene oligomers. 

The versatility of the oligomerization of propylene is very much evident from the extensive applications the individual products and their mixtures find. The oligomerization of ethylene essentially involves the addition of a C-H bond of one olefin molecule across the double bond of a second one. On the other hand, in the oligomerization of propylene four products are possible if only the vinylic C-H bonds are considered, two products involving a C-H bond of methylene carbon and another two involving a C-H bond of the methine carbon. The major products of the initial step of the oligomerization reaction are n-hexenes, 4-methyl-pentene, 2-methylpentene, and 2,3-dimethylbutene. The selectivity of the products depends on the metal, the ligands, and the mode of activation of the olefin. 

Pilot-scale as well as industrial-scale (IFF dimersol process) oligomerization of propylene using organometallic catalysts have been reported [540,541]. The 

CuAlCU and CU2CI2 in the presence of EtjAlCl [15] in isooctane medium catalyzes the dimerization of propylene at atmospheric pressure to give transA-methyl-2-pentene (30.4%) and hexene (27.4%), with 2-methyl-2-pentene (4.5%), 2-methylpentane (1.3%), 4-methyl-1-pentene (1%), and 2-methyl-1-pentene (0.6%) as minor products. AgAlCU and ZnAhClg with EtAlCU or EtjAlCl is also used for conversion of propylene to trans-4-methyl-2-pentene and 2-methyl-2-pentene. 

A patent report [547] is available on the oligomerization of propylene in the presence of BBu3MR H (M = Al, Ga, In, Be, Mg, Zn R = monovalent hydrocarbon radical n = valence of metal m = 0-3) at 195-200°C. Organoboranes promote the isomerization of the product to an a-olefin, which is stabilized by shifting an alkyl group to selectively form 2-methyl-1-pentene. 

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In addition, Lagowski and Simons showed (80) that the black, nickel-containing substances produced by the cocondensation of nickel atoms and alkynes are active, homogeneous catalysts for the oligomerization of terminal acetylenes under mild conditions. Table XVIII shows the yields of the oligomerization of propylene by these catalysts. 

The oligomerization of propylene and butenes to gasoline range olefins is a technology which began in the 1930s with the work of Ipatieff on phosphoric acid in... 

Cumene is generated following a deprotonation step [85]. One of the undesired reactions is multiple alkylahon with propylene. Oligomerization of propylene is also undesired. Beta zeolite is a typical catalyst for this reaction. A series of Beta zeolites synthesized with Si/Af rahos ranging from 20 to 350 were evaluated for the alkylation of benzene with propylene at 423°K and 3 MPa in the presence of benzene alkene molar raho of 7.0. The benzene alkene molar ratio was kept high in order to minimize the undesired reactions. The selectivity to the mono-alkylate product was 92-93% in every case with the balance being the dialkylated product. The activity decreased with increase in Si/Al2 but the selectivity was independent of the Si/A12 ratio [86]. 

Branched Primary Alcohol Ethoxylates (BPAE). The hydrophobes of BPAE are produced by oligomerization of propylene or butene followed by catalytic addition of CO and H2 to yield highly branched alcohols. The ethoxylates of these alcohols biodegrade more slowly and less extensively than the linear alcohol ethoxylates (11.12). 

This reaction mechanism also explains why oligomerization of propylene, as mentioned, tends to yield much more trimer than dimer. The dimeric carbocation (4) formed readily undergoes a hydride shift to yield tertiary cation 5 ... 

Watson et al.124-1261 studied the polymerization of ethylene and propylene with Lu(n5-C5Me5)2(CH3) ether in toluene or cyclohexane at 30-80 °C. The Lu complex produced polymers of Mn = 10M04 for ethylene, and oligomers for propylene. In the oligomerization of propylene an unusual chain transfer reaction due to 0-alkyl elimination was found together with P-hydrogen elimination from Lu-alkyls as chain-terminating processes 125). 

The heat requirements of the reactive distillation-based process are ca. 50% lower than in the conventional technology. In the alkylation of benzene to cumene reactive distillation effectively eliminated the hot spots and reduced the oligomerization of propylene (6). 

Fig. 24. Asymmetric oligomerization of propylene at various temperatures gas-chromatographic separation of 2,4-dimethyl-2-heptene (trimer) in a capillary column coated with octakis(6-0-methyl-2,3-di-0-pentyl)cyclodextrin) (204).

Alkylbenzene. Alkylbenzene is an intermediate for the production of alkylbenzene sulfonate. Alkylbenzene consists of a mixture of phenyl substituted n-alkanes of 9 to 14 carbon atoms. Prior to 1965, alkylbenzene was synthesized from propylene tetramer, obtained by oligomerization of propylene. The resulting hard alkylate was a highly branched chain compound. However, the slow biodegradability of propylene tetramer-based materials soon became apparent and by 1965, most of the detergent industry had switched over to linear alkylbenzene. Extensive research has demonstrated... 

Although SPA remains a viable catalyst for cumene synthesis, it has several important limitations 1) cumene yield is limited to about 95% because of the oligomerization of propylene and the formation of heavy alkylate by-products 2) the process requires a relatively high benzene/propylene (B/P) molar feed ratio on the order of 7/1 to maintain such a cumene yield and 3) the catalyst is not regenerable and must be disposed of at the end of each short catalyst cycle. Also, in recent years, producers have been given increasing incentives for better cumene product quality to improve the quality of the phenol, acetone, and especially a-methylstyrene (e.g., cumene requires a low butylbenzene content) produced from the downstream phenol units. 

Oligomerization of Propylene. In principle, the same types of catalysts are used for propylene oligomerization as described for C2H4 oligomerization . 

Dimerization of isobutene with a catalyst of Si02/Al203 molar ratio of 102, NiO/Si02 molar ratio 0.021 in autoclave at 60 °C, 15 min and conversion 44% oligomerization of propylene with the above formula for catalyst, space velocity 2.87h , 3.08 MPa, 94 C, conversion 79%... 

Petrochemical alcohols are also produced via the oligomerization of propylene and butylene, followed by hydroformylation of the olefine to the alcohol. 

The structure at the upper left comer characterizes the main product. The above technology shows that synthesis of these products gives a mixture of several isomers. Process controls and purification methods allow to keep concentrations within the required Umits. Decyl alcohols are also obtained by oligomerization of propylene in the presence of deactivated zeolites, separation of olefins containing nine caibon atoms, formylation of mixture to aldehyde, and hydrogenation of aldehydes to corresponding alcohols. ... 

UOP developed two varieties of zeolite catalyst designated as QZ-2000 and QZ-2001 (47,48). Its research indicated that the catalysts have Bronsted acidity values. As a result, oligomerization of propylene is essentially eliminated. Accelerated stability tests indicated that the percentage of the bed of catalyst employed for desired reactions increases with time of operation. QZ-2001 demonstrates improved stability and operation at benzene/propylene ratios of 2.0 in its liquid-phase process. Unreacted benzene and polyisopropylbenzenes are recovered and recycled so that cumene jdelds of about 99% are obtained. Four catalyst beds in series are employed. The catalysts need to be reactivated after about 2-5 years. UOP have licensed several units. 

Zeolite ZSM-58 (and its coimterpart Sigma-1) have been foimd useful in the conversion of methanol to mainly lower olefins [16,18] and for the oligomerization of propylene [17]. Moreover, it has been shown that shape selective... 

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