Improvement of supported catalysts for syndiotactic polymerization of styrene

The catalytic system Ti(OBu)(4) in combination with methylaluminoxane (MAO) was tested for the syndiospecific polymerization of styrene. A comparison was established between this homogeneous catalytic system and the same one supported on silica or alumina. An attempt was made to introduce a "tether" between the support and the active species to enhance both productivity an d syndiospecificity. These tethers consisted of diols with different length s. At last, the catalytic system Zr(OBu)(4) was supported on silica or alum ina with MAO as a cocatalyst and was tested under the same conditions as ot her catalysts. This study reveals that Ti(OBu)(4) supported on silica enhan ces the productivity and leads to higher molecular weights, while the addit ion of a diol does not result in any enhancement compared to the silica-sup ported catalyst. On the contrary, alumina alone does not seem to be a good support for Ti(OBu)(4), while introducing a short diol such as ethylene gly col leads to a great enhancement of both productivity and syndiospecificity . As reported in the literature, Zr(OBu)(4) always leads to much lower prod uctivities than Ti(OBu)(4).