Linear heterogeneous catalysts

In the early 1950s, Ziegler observed that certain heterogeneous catalysts based on transition metals polymerized ethylene to a linear, high density material at modest pressures and temperatures. Natta showed that these catalysts also could produce highly stereospecific poly-a-olefins, notably isotactic polypropylene, and polydienes. They shared the 1963 Nobel Prize in chemistry for their work. 

In the Institut Fransais du Petrc le process (62), ethylene is dimerized into polymer-grade 1-butene (99.5% purity) suitable for the manufacture of linear low density polyethylene. It uses a homogeneous catalyst system that eliminates some of the drawbacks of heterogeneous catalysts. It also inhibits the isomerization of 1-butene to 2-butene, thus eliminating the need for superfractionation of the product (63,64). The process also uses low operating temperatures, 50—60°C, and pressures (65). 

Low pressure (0.1 to 20 MPa) and temperatures of 50 to 300°C using heterogeneous catalysts such as molybdenum oxide or chromium oxide supported on inorganic carriers to produce high density polyethylene (HDPE), which is more linear in nature, with densities of 0.94 to 0.97 g/cm. ... 

Octol A process for making mixed linear octenes by the catalytic dimerization of mixed butenes. A proprietaiy heterogeneous catalyst is used. Developed jointly by Hiils and UOP, and now offered for license by UOP. First operated in 1983 in the Hiils refinery in Marl, Germany. Another installation began production in 1986 at the General Sekiyu Refineries in Japan. 

Standard Oil A process for polymerizing ethylene and other linear olefins and di-olefins to make linear polymers. This is a liquid-phase process, operated in a hydrocarbon solvent at an intermediate pressure, using a heterogeneous catalyst such as nickel oxide on carbon, or vanadia or molybdena on alumina. Licensed to Furukawa Chemical Industry Company at Kawasaki, Japan. 

The Diffusion Model. The uptake of a solute by a sorbent can be analyzed by a diffusion model, which has been used successfully to model adsorption rates onto activated carbon (74, 75), ion exchangers (72), heterogeneous catalysts (76), and soil columns (77). For the purpose of illustration, we can consider the diffusion of a compound into a spherical sorbent grain under conditions of linear sorption and no exterior mass transfer limitations (73), which is described by... 

In one process (Fig. 1), linear paraffins are dehydrogenated to linear olefins that are then reacted with benzene over a solid heterogeneous catalyst to produce the linear alkyl benzenes. Usually, the paraffins are of the C10 to C14 chain length. 

Metal-oxides of the type (Al203)x(Sn0)Y(Zn0)z were also studied as heterogeneous catalysts for the transesterification reaction of soybean oil (Macedo et al., 2006). It was observed that these materials are active for soybean oil alcoholysis with different alkyl-chain alcohols using several alcohols, including branched ones. The best result was achieved using methanol, with conversion yields up to 80% in 4 h. As observed for the complex 1 in homogenous conditions, the catalytic activities are strongly dependent on the nature of the alcohol. For alcohols with a linear chain, the reaction activities decrease with... 

Stoichiometric reaction of the type shown by 7.4 also leads to the formation of ethylene oligomers. In the Ethyl Corporation process one step involves stoichiometric reaction of this type. Another variant of this is the Conco process, where such stoichiometric reactions are followed by oxidation and hydrolysis of the aluminum alkyls. This gives linear a-alcohols that are used in biodegradable detergents. The co-product is highly pure alumina, which has a variety of uses, including that of an acidic heterogeneous catalyst. 

Application The Detal process uses a solid, heterogeneous catalyst to produce linear alkylbenzene (LAB) by alkylating benzene with linear olefins made by the Pacol process. 

Homogeneous catalysts have significant advantages compared with heterogenous catalysts concerning both theoretical studies and technological applications. Reports on the application of cyclic and linear poly (aluminoxanes)... 

The tetraallyl complex Th( -C3H5)4 supported on dehydroxylated y-alumina is an outstanding heterogeneous catalyst for arene hydrogenation that rivals the most active platinum metal catalysts in activity. Th() -C3H5)4/DA also catalyzes the rapid and selective deuteration of linear and cyclic alkanes. C-H reactivities fall in the order primary > secondary > tertiary. 

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