The Mathematics of Ethylene Oligomerisation and Polymerisation

Abstract

Linear α-olefins or LAOs are produced by the catalytic oligomerisation of ethylene on a multimillion ton scale annually. A range of LAOs is typically obtained with varying chain lengths which follow a distribution. Depending on the catalyst, various types of distributions have been identified, such as Schulz-Flory, Poisson, alternating and selective oligomerisations such as ethylene trimerisation to 1-hexene and tetramerisation to 1-octene. A comprehensive mathematical analysis for all oligomer distributions is presented, showing the relations between the various distributions and with ethylene polymerisation, as well as providing mechanistic insight into the underlying chemical processes.

Ethene oligomerization on nickel microporous and mesoporous-supported catalysts: Investigation of the active sites

“…For a given α, the mole fraction (xn) of an oligomer comprising n monomer units (n = 1 for ethene, n = 2 for butene etc.) can be computed using the standard Schultz-Flory formula, ( ) = (1 − ) [72].…”

Cleaner technology for the production of linear long-chain α-olefins through a “millisecond” oxidative cracking process: a positive impact of the reactant carbon chain length

“…The Anderson-Schultz-Flory (ASF) law 5,6 allows modelling the evolution of the molar distributions of LAOs resulting from cracking according to the following equation: where D mol CxHy is the molar distribution of a LAO and x is its number of carbons.…”

“…The ASF law is usually used to describe the distribution of LAOs synthesised from chain growing processes such as ethylene oligomerisation 5,6 or Fisher-Tropsh. 36 It reports competition between twin reactions: propagation of the chain growth and termination of the polymerisation process.…”

“…[3][4][5] The chain lengths of LAOs thus extend from 4 to 30 carbon atoms and follow the Schulz-Flory distribution for high-temperature oligomerisation (Gulfene and SHOP processes) or the Poisson distribution for lowtemperature oligomerisation (ethyl process). 3,6,7 LAOs then supply the markets of polyethene, surfactants, lubricants and plasticisers. 3,8 The oxidative cracking (OC) of hydrocarbons in a millisecond reactor (MSR) appears as a promising alternative to synthesise these raw materials in one step at atmospheric pressure.…”

Alkene oligomerization via metallacycles: Recent advances and mechanistic insights

“…Following Karl Ziegler's discovery of ethylene oligomerization by organoaluminium compounds in 1952, [1] production of linear α-olefins (LAOs) rapidly became a major process in the petrochemical industry, with an annual worldwide production estimated around 6.2 million tons in 2018. [2] Depending on their alkyl chain length, LAOs can be used as starting materials in various applications such as comonomers in the polymer industry, detergents, surfactants or lubricants. Through a careful choice of catalyst (and co-catalyst), distribution of α-olefins ("full range" processes: C 4 -C 30 + ) or one single α-olefin ("on purpose" processes: C 4 , C 6 or C 8 ) can be obtained.…”