021 650 1837 info@cchange.ac.za

RSA Olefins

The worldwide alpha-olefin market, which is currently estimated at 2.6m M tons/year, could increase drastically over the next years according to various reports. There are currently eight alpha-olefin producers worldwide. Most of the current commercial linear alpha-olefin (LAO) plants produce even-numbered alpha-olefins based on ethylene oligomerisation. The exception is the coal-based synthetic fuels plant of Sasol who is the major producer of C5-C8 alpha-olefins range of products. Sasol is the only producer of 1-pentene in commercial quantities, and has the potential to recover other LAOs.

 

The Sasol process is unique in that the alpha-olefins are produced from a gasification plant and Fischer-Tropsch conversion. Coal is converted to crude synthesis gas in the presence of steam and oxygen under high presssure and temperature. The synthesis gas (hydrogen and carbon monoxide) is purified and converted under pressure in the presence of an iron-based catalyst to yield hydrocarbons in the C1-C20 range. The hydrocarbon stream is then subjected to various purification stages, i.e. prefractionation to split out alpha-olefins, etherification to convert branched olefins into heavy ethers followed by removal from the main olefin stream by distillation, superfractionation and distillation to separate out impurities (paraffins and cyclic olefins) and to produce pure pentene, hexene and octene. Higher olefins can also be recovered. Sasol produced 177k M tons (ca. 5% of world production) in 2000. BP Amoco, Chevron and Shell account for more than 75% of total worldwide capacity.

 

The largest end-use (ca. 50% in 2000) of these olefins is as polymerisation co-monomers, synthetic lubricants (so-called poly-alpha-olefins or PAOs) being the second largest consumer accounting for 85% of the consumption of 1-decene. Numerous other outlets for alpha-olefins exist, of which the detergent alcohols (used largely in detergents and plastics) represent a prime example. These alcohols typically originate by the chemical manipulation of long chain alpha-olefins in two distinct catalysed steps, being hydroformylation of the olefin to form the analogous aldehyde, which is then reduced to the corresponding alcohol. These alcohols represent products of substantial value for the commodities industry, often being incorporated into formulations destined for speciality markets and end-use. This underlines the importance and value of the longer chain olefins in the world markets. The most common commercial reactions involving LAOs include oxo reactions (i.e. hydroformylation), oligomerisation/polymerisation, addition, alkylation, sulphonations and oxidations.

 

Despite there being an extant supply of medium and long chain olefins, there exist an untapped potential supply of these valuable intermediates in the form of shorter chain length olefins. Such shorter olefins, especially in the case of alpha-olefins, can readily be subjected to metathesis reactions to produce longer internal olefins together with ethylene as a by-product. The ethylene can be captured and utilised in polymerisation reactions while the internal olefins can be used for down-streaming. This down-streaming will necessarily include the isomerisation of the internal double bond to the more reactive terminal analogue, said terminal (alpha) analogue of which is the subject of the detergent alcohol series of opportunities.

In the detergent industry the perennial balancing act is between surfactant chain length, biodegradability and solubility. Traditionally linear alpha-olefins in the C12 to C15 range are used in the manufacture of alcohol sulphates. Longer chain linear alcohol sulphate surfactants leads to higher surfactancy and performance but is offset by low hardness tolerance and limited cold water solubility. Cosurfactants are used to achieve the right balance of performance and hardness tolerance. Furthermore, controlled alkyl substitution in the middle of the hydrophobe chain produced surfactants that are biodegradable, highly soluble and more surface active. Such branching allows the use of chain lengths as long as C16 and C17 without incurring the historical negatives like lack of biodegradability.

Current Projects – RSA Olefins

Code

Project

Institution

OLE-01

The separation of a homogeneous catalyst from a catalyzed reaction mixture using nanofiltration

NWU, US

OLE-07

Oligomerisation of alkenes

US, UJ

OLE-08

Olefin metathesis of C5 – C10 alkenes

NWU

OLE-10

Hydroformylation of alkenes

UCT, US, UJ

OLE-11

Requirements, manufacture and properties of detergents from olefins

NWU, UKZN

Researchers – RSA Olefins

Name

Role

Institution

Project Involvement

M. Vosloo

Programme Manager

NWU

OLE; OLE-01; OLE-08; OLE-11

J. Darkwa

Project Leader

UJ

OLE-07; OLE-10

S. Mapolie

Project Leader

US

OLE-07; OLE-10

G. Smith

Project Leader

UCT

OLE-10

S. Ojwach

Project Leader

UKZN

OLE-10; OLE-11

P. van der Gryp

Project Leader

US

OLE-01

J. Jordaan

Research Team Member

NWU

OLE-01; OLE-08

D. Young

Research Team Member

NWU

OLE-11

C. van Sittert

Research Team Member

NWU

OLE-01; OLE-08

B. Makhubela

Research Team Member

UJ

OLE-7; OLE-10

A. Swarts

Research Team Member

NWU

OLE-01; OLE-11

Back