Published September 2012
This review presents a technoeconomic representation of a 1-hexene production process based on technical data extracted from the patents of IFP Energies nouvelles (IFPEN). The best possible engineering judgment has been used in the conceptualization and design of the process presented; however, a commercial Axens 1-hexene plant may or may not have the exact construct presented in this review. We, nevertheless, strongly believe that our process design and economic evaluation present a reasonably good picture of the actual process, and the two should be well within the marginal boundaries of error.
The process involves oligomerization of high-purity ethylene gas in the presence of a homogeneous catalyst system. The reaction conditions are 284°F at 435 psia. The catalyst system consists of a proprietary chromium-based catalyst, a cocatalyst based on magnesium, and an activator aluminum salt dissolved in a hydrocarbon solvent. Ethylene per-pass conversion is kept at 33%. The reaction yield of C6 olefins is over 85% with some C4 as well as higher carbon number olefins as by-products. The selectivity of the alpha-olefins in the C6 fraction is very high, at over 99%. The reactant mixture is flashed in a flash drum and the ethylene recovery column to recover unconverted ethylene which is recycled to the reactor after compression. The bottoms from the ethylene column are separated in a distillation column to obtain the desired 1-hexene product as liquid distillate. The bottoms from the product column contain solvent to be recycled to the reactor system and C8+ olefinic oligomers that are not purified further in this study.
Our cost analysis is based upon a 25 thousand metric t/yr plant. We estimate that a plant of that capacity will require a capital investment of about $25.7 million at a US Gulf Coast location. The product value (as defined in the text) is about $0.74/lb and the production cost is $0.62/lb. Cost details and relevant assumptions are given in the process description section of this review.