The Dimersol-X process transforms butenes into octenes, which are ultimately used in the manufacture of plasticizers via isononanol (isononyl alcohol) and diisononyl phthalate units.
Butenes from fluid catalytic cracking (FCC) or steam cracking are dimerized into a liquid-phase oligomerization unit comprising three sections. In the reaction section, dimerization takes place in multiple liquid-phase reactors (1) using homogeneous catalysis and an efficient recycle mixing system. The catalyst is generated in situ by the reaction of components injected in the recycle loop. The catalyst in the reactor effluent is deactivated in the neutralization section and separated for safe disposal (2).
The stabilization section (3) separates unreacted olefin monomer and saturates from product dimers, while the second column (4) separates the octenes. A third column can be added to separate dodecenes.
Yields: Nearly 80% conversion of n-butenes can be attained and selectivities toward octenes are about 85%. The typical C8 product is a mixture having a minimum of 98.5% octene isomers with the following distribution:
Dimersol-X octenes exhibit a low degree of branching, resulting in higher downstream oxonation reaction yields and rates, and better plasticizer quality.