Investigation of Catalyst Fragmentation in Gas‐Phase Olefin Polymerisation: A Novel Short Stop Reactor

Abstract

Summary: A short stop reactor (SSR) was developed to study nascent particle morphology and reaction kinetics in the gas‐phase polymerisation of olefins on supported catalysts. It is shown that the SSR provides a useful means to look into important phenomena such as catalyst fragmentation and catalyst site activation and deactivation that take place during the very early stages of the heterogeneous polymerisation of olefins. New experimental results obtained from gas‐phase polymerisation of ethylene show that, depending on the type of catalyst system and on the reaction conditions, different kinds of morphologies can be obtained for the nascent polymer (e.g., cracks and folded chain). Experimental data also indicate that the growth of the polymer chains occur at a non‐steady state during the very early stages of the polymerisation.SEM image showing the morphology of a polymer/catalyst particle after 2 seconds of polymerisation at 8 bars of ethylene on an MgCl2‐supported Ziegler‐Natta catalyst.magnified imageSEM image showing the morphology of a polymer/catalyst particle after 2 seconds of polymerisation at 8 bars of ethylene on an MgCl2‐supported Ziegler‐Natta catalyst.

Packed‐bed reactor for short time gas phase olefin polymerization: Heat transfer study and reactor optimization

“…11,29,30 In these previous studies, triethylaluminium (TEA)-treated silica was used as the inert diluent. This implies that solid liquid extraction is necessary to recover the polymer for analysis.…”

“…2,3 It is well known that the morphology of growing polymer particles as well as the properties of nascent polymer evolve very quickly during the early instants of a polymerization. [4][5][6][7][8][9][10][11] This phase of the reaction can be crucial in ensuring adequate polymer properties, obtaining or maintaining stable reactor operation, preventing fines generation, and avoiding temperature excursions and catalyst deactivation. The risks of overheating of particles are highest during the early instants of the reaction given the highly exothermic nature of these polymerizations (heats of reaction on the order of 100 kJ/mol 12 and rates of reaction on the order of 5-35 kg of polymer per gram of catalyst per hour) found in industrial processes.…”

“…5,6,[26][27][28] Recently, our group developed and built a special reactor to perform stopped flow catalytic polymerizations in gas phase under realistic conditions. 11 The first version of such reactor consisted in a 1-mL packed catalytic bed capable of working at high temperatures and moderate pressures (up to 90 C and 10 bars). For the first time, evolution of PE properties together with particle morphology produced by classic Ziegler-Natta (ZN) catalysts in gas phase was obtained.…”

System Identification for Experimental Study for Polymerization Catalyst Reaction in Fluidized Bed

“…The morphological development of the catalyst originally obtained from its support could replicate the polymer in controlled conditions. Heterogeneous catalyst particles break up during the early stages of the polymerization, possibly due to the chemical reaction of the catalyst component, mechanical stress and also polymer growth, respectively [Silva et al, 2005;Shaotian et al, 2001). In Ziegler-Natta polymerization, the rate/time profiles are mainly a decay type with very high polymerization activity at the early stage of the reaction.…”

Heat Transfer and Nascent Polymerisation of Olefins on Supported Catalysts

“…In an earlier work, we presented a high pressure gas phase reactor with residence times as short as 0.1 seconds [11] to look at the initial instants of the reaction, and to provide a partial solution to some of these difficulties. This early version of the fixed bed gas phase system worked reasonably well for higher pressures, but the set up did not allow for controlled flow rates, and problems with the initial design meant that there were difficulties associated with back flow at low pressures.…”