Olefins, especially those containing about 6 to about 20 carbon atoms, are important items of commerce. Olefins are used as intermediates in the manufacture of detergents, synthetic lubricants, lube oil additives, plasticizers, and surfactants. Olefins are also used as monomers, such as in linear low-density polyethylene, high-density polyethylene, polypropylene, polystyrene, etc. and as intermediates for many other types of products. As a consequence, improved methods of making these compounds are of value.
Most commercially produced olefins are made by the oligomerization of ethylene, catalyzed by various types of compounds, such as alkylaluminum compounds, certain nickel-phosphine complexes, and a titanium halide with a Lewis acid such as diethylaluminum chloride (DEAC). In many of these processes, significant amounts of branched and/or internal olefins and/or diolefins are also produced. Because the location of the double bond in olefins affects the physical properties of the olefins produced, generally, branched and/or internal olefins and/or diolefins perform differently from terminal olefins, i.e. normal alpha olefins (NAOs). The position of the double bond in the olefins also has a significant impact on the physical properties of derivatives made from the olefins. For example, a sulfonate salt prepared from a terminal olefin often functions as an oil-in-water surfactant, but a sulfonate salt prepared from an internal olefin, such as in the middle of the molecule, forms a double tail surfactant that performs well as a surfactant in inverted water-in-oil emulsions.
When a terminal olefin is isomerized, the double bond migrates to an internal position to form a more thermodynamically favored isomer. Under normal circumstances, the double bond migration will lead to a thermodynamic statistical distribution of the double bond at each carbon position of the molecule chain.
Because thermodynamics control double bond distribution during known olefin isomerization processes, economically producing an olefin with predominately 2-alkenes has been difficult, particularly when using heterogeneous catalysts. Attempts have been made to selectively produce 2-alkenes using homogeneous catalysts. Homogeneous catalysts, however, are generally more expensive than heterogeneous catalysts. A need exists for an economical process to selectively produce 2-alkenes. It would be advantageous if the process used heterogeneous catalysts.