Silyl diol ester as a new selectivity control agent in MgCl₂-supported Ziegler–Natta systems for propylene polymerization: catalyst structure and polymer properties

Abstract

In this study, bis(benzoyloxy)dimethylsilane (SDE) was developed as a non-phthalate selectivity control agent (internal donor (ID) and external donor (ED)) in MgCl 2 -supported Ziegler-Natta (ZN) systems. The impact of SDE as an ID was investigated in regards to chemical composition, morphology, adsorption behavior (using FTIR spectroscopy, WAXD and SEM studies) and the propylene polymerization performance of the catalyst. The results of the adsorption behavior of SDE revealed that SDE, while able to stabilize the electronically unsaturated surfaces of MgCl 2 [(104) and (110)], has a rather high tendency to be absorbed on strongly acidic Mg ions at the corners of these crystals. The catalyst with optimum SDE content as an ID afforded a system with reasonable activity and isotacticity (even in the absence of ED) along with broader molecular weight distribution (PDI: 6.2-10) and greater flexural modulus than phthalate-based ZN systems. SDE was also used as a new ED in most widely used fourth-and fifthgeneration catalyst systems. The results revealed that in fifth-generation catalyst systems, there was an increase in hydrogen response (>40%) along with an increase of activity without any change in the thermal properties of the final polymer in comparison to a conventional ED (alkoxy silane).

Internal donors on supported Ziegler Natta catalysts for isotactic polypropylene: a brief tutorial review

“…Another study on SDE revealed that catalytic activity increases with increase in Mg/SDE ratio and reaches to a maximum at a particular Mg/SDE [106]. The similar phenomenon was noted for II too.…”

Synthesis of Bis(methoxymethyl)silanes and Their Application in MgCl2-Supported Ziegler–Natta Propylene Polymerization as External Donors

“…The n -heptane solvent was refluxed with metal sodium and benzophenone for 24 h and then was distilled out before use. The bis­(methoxymethyl)­silanes were prepared according to the literature , with a little modification. Dimethoxydiphenylsilane (Donor-Ph), diisopropyldimethoxysilane (Donor-P), and dicyclopentyldimethoxysilane (Donor-D) were purchased from Innochem.…”

“…Bis­(methoxymethyl)­silanes were prepared according to the previously reported procedure with some modifications. , In a typical example, the synthesis of bis­(methoxymethyl)­silanes (Donor-PhS, Donor-PS, and Donor-DS) was carried out as follows (Scheme ).…”

Effect of adduct synthesis parameters on the ethylene polymerization kinetics of Ziegler Natta catalysts

“…These polymers are commercially produced mostly by heterogeneous Ziegler Natta catalysts 4,12,13 . These catalysts are mainly composed of support (MgCl 2 , Mg(OEt) 2 , and silica) and TiCl 4 as active center, and occasionally electron donor to control isotacticity in polypropylene 14–18 . By the heterogenization of catalyst on the carrier, its activity and morphology are regulated, which diminishes reactor foaling and improves solid particles conveying in industrial reactors, respectively 19,20 .…”

“…4,12,13 These catalysts are mainly composed of support (MgCl 2 , Mg(OEt) 2 , and silica) and TiCl 4 as active center, and occasionally electron donor to control isotacticity in polypropylene. [14][15][16][17][18] By the heterogenization of catalyst on the carrier, its activity and morphology are regulated, which diminishes reactor foaling and improves solid particles conveying in industrial reactors, respectively. 19,20 Among the mentioned supports, MgCl 2 is the most appreciated one, due to its abundance, cheap price and ease of preparation methods.…”