Linear alpha olefin
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2008-07-07T21:23:20Z
199.197.2.142
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'''Linear Alpha Olefins''' (LAO) or '''Normal Alpha Olefins''' (NAO) are [[olefin]]s or [[alkene]]s with a [[chemical formula]] [[Carbon|C]]<sub>x</sub>[[Hydrogen|H]]<sub>2x</sub>, distinguished from other mono-olefins with a similar [[molecular formula]] by linearity of the [[hydrocarbon]] chain and the position of the [[double bond]] at the primary or alpha position.
[[Image:1-Hexene.PNG|frame|center|1-hexene, a typical linear alpha-olefin]]
Linear alpha olefins are a range of industrially important [[alpha-olefins]], including [[1-butene]], [[1-hexene]], [[1-octene]], [[1-decene]], [[1-dodecene]], [[1-tetradecene]], [[1-hexadecene]], [[1-octadecene]] and higher blends of C<sub>20</sub>-C<sub>24</sub>, C<sub>24</sub>-C<sub>30</sub>, and C<sub>20</sub>-C<sub>30</sub> ranges.
== Synthesis ==
'''Overview'''
Industrially, linear alpha olefins are commonly manufactured by two main routes: [[oligomerization]] of [[ethylene]] and by [[Fischer-Tropsch]] synthesis followed by purification. Another route to linear alpha olefins which has been used commercially on small scale is [[Dehydration reaction|dehydration]] of [[alcohols]]. Prior to about 1970's linear alpha olefins were also manufactured by thermal cracking of [[waxes]], whereas linear internal olefins were also manufactured by [[chlorination]]/[[dehydrochlorination]] of [[linear paraffins]].
There are six commercial processes which [[oligomerize]] [[ethylene]] to linear alpha olefins. Four of these processes produce wide distributions of linear alpha olefins. These are the [[Ethyl Corporation]] ([[Ineos]]) process, [[Gulf Oil|Gulf]] ([[Chevron Phillips Chemical Company]]), [[Shell Oil Company]] [[Shell higher olefin process|SHOP]] process, and [[Idemitsu Petrochemical]] process.
Two commercial processes make a single alpha-olefin carbon number. [[Phillips]] (CP Chemical Company) ethylene trimerization process, produces only 1-hexene. Another commercial process, offered by a technology licensor [[IFP]], dimerizes ethylene to high purity 1-butene.
There are two alpha-olefin processes that have not been commercialized as of Q1, 2006. One is an ethylene oligomerization to a wide range of linear alpha olefins technology being offered by a technology licensor [[UOP]]. To date, no commercial plants have been built using UOP's technology.
The newest non-commercial linear alpha olefin process is the Sabic-Linde "[[α-Sablin]]" process, being commercialized by [[Saudi Arabian Basic Industries Company]] in Saudi Arabia. [[α-Sablin]] process is a low-pressure ethylene oligomerization process conducted over heterogeneous catalyst in a slurry bed. The process also makes a C4-C20+ distribution of alpha-olefins. Sabic expects commercialization of α-Sablin process at the end of 2006.
The only commercial process to isolate linear alpha olefins from synthetic crude is practiced by [[Sasol]] Ltd., a [[South African]] oil and gas and petrochemical company. Sasol commercially employs [[Fischer-Tropsch]] synthesis to make fuels from [[synthesis gas]] derived from coal and recovers 1-hexene from these fuel streams, where the initial linear alpha olefin concentration in a narrow [[distillation]] cut may be 60%, with the remainder being vinylidenes, linear and branched internal olefins, linear and branched paraffins, [[alcohols]], [[aldehyde]]s, [[carboxylic acid]]s and [[aromatic compound]]s.
Dehydration of alcohols to linear alpha olefins by passing alcohols in a vapor phase over acidic alumina catalyst has been practiced periodically by Ethyl Corporation (later BP, now Ineos), Chevron Phillips, Sasol (formerly Vista Chemical) and Godrej Industries, an Indian petro- and specialty chemical company. Normally, this process is not economical as the linear fatty alcohols are more valuable than the corresponding linear alpha olefins. However, the process has been applied whenever the value of fatty alcohols dipped below that of linear olefins because of market dynamics or regional supply-demand issues.
One of the problems of the linear alpha olefin industry is the wide range of products made by most of the processes. While the Ethyl process makes a [[Pseudo-Poisson]] distribution of products, most others, including the Sasol process, make a [[Schultz-Flory]] distribution. With 8-10 products being made at the same time, with most of them sold into different markets with different dynamics, it is difficult to balance the supply and the demand for all or even most products.
'''Ineos (Ethyl) Process'''
Ethyl linear alpha olefin process is commonly called stoichiometric Ziegler process. It is a two-step process. In the first step, a stoichiometric quantity of triethyl aluminium in olefin diluent is reacted with excess ethylene at high pressure (above 1000 psig) and relatively low temperature (below 400F). On the average, nine moles of ethylene are added per mole of triethyl aluminium, resulting in, on average, a tri-octyl aluminium. The distribution of alkyl chains on the aluminium is determined by statistical bell curve distribution except for some smearing to the light side due to the kinetic phenomena and some smearing to the heavy side due to some incorporation of heavier olefins into the chain. Excess ethylene and olefin diluent are flashed off. The heavy aluminium tri-alkyls are reacted with ethylene again in a displacement or a tranalkylation reaction, but at high temperature (over 400F) and at low pressure (less than 1000 psig) to recover triethyl aluminium and a statistical distribution of linear alpha olefins, which serve as the olefin diluent in the chain-growth step.
'''CP Chemicals (Gulf) Process'''
The Gulf linear alpha olefin process is commonly called a catalytic Ziegler process. Triethyl aluminium is used as a catalyst, but in catalytic amounts and the process is a single-step process. Tri-ethyl aluminium and excess ethylene are fed to a plug flow-reactor. The reaction is conducted at high pressure and high temperature. Excess ethylene is flashed off. The tri-ethyl aluminium catalyst is washed out of the product with caustic and the linear alpha olefins are separated. The product distribution is a Schultz-Flory distribution typical of catalytic processes.
== Applications ==
There is a wide range of applications for linear alpha olefins. The lower carbon numbers, 1-butene, 1-hexene and 1-octene are overwhelmingly used as [[comonomers]] in production of polyethylene. High Density PolyEthylene ([[HDPE]]) and Linear Low Density PolyEthylene ([[LLDPE]]) use approximately 2-4% and 8-10% of comonomers, respectively.
Another significant use of C<sub>4</sub>-C<sub>8</sub> linear alpha olefins is for production of linear [[aldehyde]] via [[oxo synthesis]] ([[hydroformylation]]) for later production of short-chain [[fatty acid]], a carboxylic acid, by oxidation of an intermediate aldehyde, or linear alcohols for [[plasticizer]] application by [[hydrogenation]] of the aldehyde.
The predominant application of 1-decene is in making [[polyalphaolefin]] synthetic [[lubricant]] basestock (PAO) and to make, in a blend with higher linear alpha olefins, [[surfactant]]s.
C<sub>10</sub>-C<sub>14</sub> linear alpha olefins are used in making surfactants for aqueous detergent formulations. These carbon numbers may be reacted with benzene to make [[linear alkyl benzene]] (LAB), which is further sulfonated to linear [[alkyl benzene sulfonate]] ([[LABS]]), a popular relatively low cost surfactant for household and industrial detergent applications.
Although some C<sub>14</sub> alpha olefin is sold into aqueous detergent applications, C<sub>14</sub> has other applications such as being converted into [[chloroparaffin]]s. A recent application of C<sub>14</sub> is as on-land [[drilling fluid]] [[basestock]], replacing [[diesel]] or [[kerosene]] in that application. Although C<sub>14</sub> is more expensive than middle distillates, it has a significant advantage environmentally, being much more biodegradable and in handling the material, being much less irritating to skin and less toxic.
C<sub>16</sub> - C<sub>18</sub> linear olefins find their primary application as the hydrophobes in oil-soluble surfactants and as lubricating fluids themselves. C<sub>16</sub> - C<sub>18</sub> alpha or internal olefins are used as synthetic drilling fluid base for high value, primarily off-shore synthetic drilling fluids. The preferred materials for the synthetic drilling fluid application are [[linear internal olefins]], which are primarily made by isomerizing linear alpha-olefins to an internal position. The higher internal olefins appear to form a more lubricious layer at the metal surface and are recognized as a better lubricants. Another significant application for C<sub>16</sub> - C<sub>18</sub> olefins is in paper sizing. Linear alpha olefins are, once again, isomerized into linear internal olefins are then reacted with [[maleic anhydride]] to make an [[alkyl succinic anhydride]], a popular paper [[sizing]] chemical.
C<sub>20</sub> - C<sub>30</sub> linear alpha olefins production capacity is only 5-10% of the total production of a linear alpha olefin plant. They are used in a number of reactive and non-reactive applications, including as feedstocks to make heavy [[linear alkyl benzene]] (LAB) and low molecular weight polymers which are used to enhance properties of waxes.
==References==
* {{cite book | title = Alpha Olefins Applications Handbook | author = George Lappin (ed.) | publisher = [[CRC Press]] | year = 1989 | isbn = 0824778952}}
==Further reading==
* {{cite book | title = Alpha Olefins Applications Handbook | author = George Lappin (ed.) | publisher = [[CRC Press]] | year = 1989 | isbn = 0824778952}}
== External links ==
* [http://www.cpchem.com/enu/nao.asp Chevron Phillips Chemicals]
* [http://www.shellchemicals.com/neodene/1,1098,496,00.html Shell Chemicals Company]
* [http://www.sasol.com/sasol_internet/frontend/navigation.jsp?navid=1600027&rootid=600001 Sasol Ltd.]
* [http://www.uop.com/objects/30%20Linear_1.pdf UOP LLC]
* [http://www.linde.com/international/web/linde/likelindeeng.nsf/repositorybyalias/pdf_lindetechnology_2_2004/$file/Linde_Technology_2_2004_En.Pdf Linde AG Technology brochure]
[[Category:alkenes]]