Patent DE-10128048-A1 (DE)
Title: Selective synthesis of linear alpha-olefins useful as comonomers in polyolefins, comprises reaction of a linear olefin with a trialkyl aluminum compound
Inventor: MAAS HEIKO
IPC: C07C2/88
Filed: 2001-06-01
Abstract: Selective synthesis of new linear  alpha -olefins comprises: (1) reaction of a linear, internal olefin with a trialkyl Al compound; (2) reaction of the linear alkyl Al compound formed with an olefin; (3) introduction of the linear  alpha -olefin into a self-metathesis reaction;  (4) reaction of the formed olefin with a trialkyl Al compound; (5) reaction of the linear alkyl Al compound formed with an olefin and formation of a trialkyl Al compound; and   (6) isolation of the desired linear alpha-olefin. New linear  alpha -olefins of 6-20 carbons are synthesized selectively in the following steps:  (1) reaction of a linear, internal olefin or a mixture of these and having a carbon number of (n/2)+1, where n = the number of C atoms of the desired linear  alpha -olefin in a transalkylation reaction with a trialkyl Al compound in isomerization conditions, where an olefin corresponding to the alkyl radical is released and the linear olefin thus added becomes attached to the Al during isomerization with formation of a corresponding linear alkyl Al compound;  (2) reaction of the linear alkyl Al compound formed with an olefin, on release of the corresponding linear  alpha -olefin having a carbon number of (n/2)+1, and formation of a trialkyl Al compound; (3) introduction of the linear  alpha -olefin formed into a self-metathesis reaction, in which a linear internal olefin with the desired carbon number n is formed;  (4) reaction of the formed olefin of carbon number n with a trialkyl Al compound under isomerizing conditions, in which an olefin corresponding to the alkyl radical is released, and the linear internal olefin becomes attached to the Al on isomerization and formation of a corresponding linear alkyl Al compound; (5) reaction of the linear alkyl Al compound formed with an olefin on release of the linear alpha-olefin having the desired carbon number n and formation of a trialkyl Al compound; and (6) isolation of the desired linear  alpha -olefin having a carbon number n.  Independent claims are also included for the following: (1) preparation of hexene from butene-containing streams, preferably raffinate (II), comprises: (a) metathesis of the insertion product with optional addition of ethene; (b) removal, by distillation, of the stream obtained in a 2-3C olefin containing light boiling fraction and in a 4-6C olefin and butane containing high boiling fraction; (c) separation, by distillation, of the low boiling fraction obtained in an ethene containing fraction and a propene containing fraction, where the ethene containing fraction is returned to step a' and the propene containing fraction is removed;  (d) separation, by distillation, of the high boiling fraction in a butene and butane containing low boiling fraction, a pentene containing medium boiling fraction, and in a hexene containing high boiling fraction; and (e) removal of the hexene containing high boiling fraction and optional returning of the remaining fraction to step a;  (2) a process in which 2-pentene from butene containing streams, preferably raffinate II, where in the educt stream the ratio of 2-butene to 1-butene is preferably at least 1, is prepared preferably using the steps: a' to e' as above; and (3) a process in which the catalyst used in metathesis can have an inorganic support and contains a compound of a group VI, VII, or VIII metal, preferably an oxide of a group VIb or VIIb metal, especially a metathesis catalyst selected from: Re2O7, WO3, and MoO3, most preferred catalyst Re2O7, on  psi -Al2O3, or Al2O3/B2O3/SiO2 mixed supports.