Ethylene alpha olefins, oligomerization

Shell Higher Olefin Process) plant (16,17). C -C alcohols are also produced by this process. Ethylene is first oligomerized to linear, even carbon—number alpha olefins using a nickel complex catalyst. After separation of portions of the a-olefins for sale, others, particularly C g and higher, are catalyticaHy isomerized to internal olefins, which are then disproportionated over a catalyst to a broad mixture of linear internal olefins. The desired fraction is... 

Oligomerization of Ethylene. 1-Butene is a small by-product in the production of linear alpha-olefins by oligomerisation of ethylene. Linear alpha-olefins have one double bond at the terminal position and comprise the homologous series of compounds with carbon atoms between 4 and 19. The primary use of alpha-olefins is in the detergent industry. About 245,000 t/yr of 1-butene was produced for chemical use in the Gulf Coast of the United States in 1988 (72). 

Linear alcohols used for the production of ethoxylates are produced by the oligomerization of ethylene using Ziegler catalysts or by the Oxo reaction using alpha olefins. 

Oligomerization of ethylene using a Ziegler catalyst produces unbranched alpha olefins in the C12-C16 range by an insertion mechanism. A similar reaction using triethylaluminum produces linear alcohols for the production of biodegradable detergents. 

Linear alcohols (C12-C26) are important chemicals for producing various compounds such as plasticizers, detergents, and solvents. The production of linear alcohols by the hydroformylation (Oxo reaction) of alpha olefins followed by hydrogenation is discussed in Chapter 5. They are also produced by the oligomerization of ethylene using aluminum alkyls (Ziegler catalysts). 

Properties and handling. Typical properties for the alpha olefins produced by ethylene oligomerization are given in Table 21-4. You can find in the table that as the carbon count increases, purity declines. The impurities are branched chains and internal olefins (beta, gamma, etc.) These variations have more opportunity to form as the molecules get longer—Murphys Third Law in operation again. 

Alpha olefins are made either by oligomerization, growing them on an aluminum root by adding ethylene until the desire size is reached, or by catalytic processes, one favoring the shorter alpha olefins. 

The resulting alcohols are one type of many alcohols used for detergents. The linear alcohols can be produced from n-paraffins by way of alpha olefins or by way of the chloroparaffins. Or they can be made from alpha olefins formed from Ziegler oligomerization of ethylene. 

Oligomerization of ethylene to higher even carbon number alpha olefins. This is the growth part of the Shell Higher Olefin Process (SHOP) Unit. 

Al-Jarallah, A. M., Anabtawi, J. A., Siddiqui, M. A. B., Aitani, A. M. and Al-Sa doun, A. W. Ethylene dimerization and oligomerization to butene-i and linear alpha-olefins a review of catalytic systems and processes. Catal. Today, 1992, 14, 1-121. 

Wasserscheid, P., Hilgers, C., and Keim, W. (2004) Ionic liquids -weakly-coordinating solvents for the biphasic ethylene oligomerization to alpha-olefins using cationic Ni-complexes./. Mol. Catal. A - Chem., 214 (1), 83-90. 

Aluminum alkyls used in making organometallic catalysts and as initiators for processes such as ethylene-propylene rubber, polybutadiene, low-pressure polyethylene, and ethylene oligomerization to make alpha-olefins and C6-C18 alcohols... 

Probably the first example of a process employing the biphasic concept is the Shell process for ethylene oligomerization in which the nickel catalyst and the ethylene reactant are dissolved in 1,4-butanediol, while the product, a mixture of linear alpha olefins, is insoluble and separates as a second (upper) liquid phase (see Fig. 7.1). This is the first step in the Shell Higher Olefins Process (SHOP), the largest single feed application of homogeneous catalysis [7]. 

Description Polymer-grade ethylene is oligomerized in the liquid-phase reactor (1) with a catalyst/solvent system designed for high activity and selectivity. Liquid effluent and spent catalyst are then separated (2) the liquid is distilled (3) for recycling unreacted ethylene to the reactor, then fractionated (4) into high-purity alpha-olefins. Spent catalyst is treated to remove volatile hydrocarbons and recovered. The table below illustrates the superior purities attainable (wt%) with the Alpha-Select process ... 

Cr/Si02, as described, was used for oligomerization of propene alone or cofed with ethylene to produce HVI-PAO (high viscosity index-poly alpha-olefin). This lubricant material had a structure with a CH3/CH2 ratio of less than 0.19, compared with a ratio greater than 0.20 for conventional PAO. 

The oligomerization process produces homologous, even-numbered, linear alpha olefins. The oligomerization is performed at 80-120°C and at pressures of 1000-2000 psig. A solvent like 1, 4-butanediol is used, in which only the catalyst and the ethylene are soluble but not the formed higher molecular weight olefins. This enables ease of separation of the product from the catalyst by simple phase separation. 

FIGURE 6.3 Coordination-catalyzed ethylene oligomerization into n-alpha olefins. TABLE 6.2... 

Kissin, Y. Y, Beach, D. L., Co-oligomerization of ethylene and higher linear alpha-olefins. 1. Co-oligomerization with the sulfonated nickel ylide-based catalytic system. / Polym. Sci., Polym. Chem. Ed., 27, 147, 1989. 

Keim, W., Ethylene oligomerization to higher alpha-olefins, Angew. Chem., 90, 493, 1978. 

He Ren, Wang Yu, and Jiang Jingyuang, Linear oligomerization of ethylene. I. Synthesis of lower alpha-olefins catalysed by zirconium catalyst, Cuihua Xuebao, 9, 58, 1988 Chem. Abstr, 109, 55301y, 1988. 

Mel nikov, V. M., and Gerasina, M. D., Oligomerization of ethylene to higher alpha-olefins on zirconium containing catalysts, Khim. Prom., 1986, 261 (Russian). 

Linear internal monoolefins can be oxidized to linear secondary alcohols. The alpha (terminal) olefins from ethylene oligomerization, described earlier in this chapter, can be converted by oxo chemistry to alcohols having one more carbon atom. The higher alcohols from each of these sources are used for preparation of biodegradable, synthetic detergents. The alcohols provide the hydrophobic hydrocarbon group and are linked to a polar, hydrophilic group by ethoxylation, sulfation, phosphorylation, and so forth. 

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