Ethylene polymerization over supported MAO/(nBuCp)2ZrCl2 catalysts: Influence of support properties

Observation on inhibition of Ti3+ reduction by fumed silica addition in Ziegler-Natta catalyst with in situ ESR

“…In order to remove the OH group on the surface, silica has usually been calcined at different temperatures between 110 and 820 8C [1][2][3][4][5][6][7][8][9]. Although the silanol groups of the silica have been exerted with high calcination temperature, the experimental evidences showed that the high calcination temperature still cannot get rid of all the OH groups [4,6,8,10,11]. Another method is to functionalize it with some substance such as alkyl silyl, alkyl silyl halide or alkyl aluminum to change the silanol groups into the other forms [1][2][3][4]6,7,10,12].…”

Bimodal polypropylene through binary metallocene catalytic systems: comparison between hybrid and mixed heterogeneous catalysts

“…There are different methods of heterogeneization [24]. Three of them are: 1) In the direct heterogeneization, the metallocene is activated by MAO and then anchored onto the support [23,24], 2) The metallocene can be supported by covalent bonding of its ligand environment to the support followed by activation with MAO [25] and 3) The indirect heterogeneization is carried out by an initial impregnation of MAO onto the support followed by adsorption and simultaneous activation of the metallocene [26]. The advantage of using the first method is that allows producing polymers with higher molar masses than those afforded by the appropriate homogeneous catalysts [21] and maximizes the number of active centres by activating the metal component in solution, instead of carrying out the process with one of the components immobilized.…”

“…The large majority of supports currently used in industry are inorganicbased, being silica the most important due to its large surface area and pore volume, chemical inertness and low cost [20][21][22][23]. There are different methods of heterogeneization [24]. Three of them are: 1) In the direct heterogeneization, the metallocene is activated by MAO and then anchored onto the support [23,24], 2) The metallocene can be supported by covalent bonding of its ligand environment to the support followed by activation with MAO [25] and 3) The indirect heterogeneization is carried out by an initial impregnation of MAO onto the support followed by adsorption and simultaneous activation of the metallocene [26].…”

Preparation, characterization, and catalytic activity of zirconocene bridged on surface of silica gel

“…Metallocene compounds supported on activating silica with ordinary alkylaluminas or MAO have been reported [7,[11][12][13][14]. * Corresponding author.…”