Optical and infrared imaging of growing polyolefin particles

Abstract

A method was de®eloped that obser®es polymer particles during a polymerization reaction using optical-and infrared imaging. The yielding images gi®e good insight into catalyst-specific properties as shape replication, distribution of acti®ity, and the acti®ation. The ad®antage of this method is the possibility to link beha®ior of indi®idual particles to its own specific properties. The infrared method measures surface temperatures of growing particles. Such data are useful to feed mathematical models describing the growth of single particles. The temperature᎐ time cur®es showed maximum temperature to be reached after some minutes; a simple model was used to describe this effect qualitati®ely. The maximum particle temperature rise was 20 K, but depended strongly on reaction rate and particle size. Temperature, prepolymerization method, catalyst recipe, and catalyst acti®ation time were ®aried for a fourth-generation Ziegler-Natta catalyst in polymerization of propylene and ethylene.

Evaluation of the Initial Stages of Gas‐Phase Ethylene Polymerizations with a SiO2‐Supported Ziegler–Natta Catalyst

“…Among them, we should mention the work of Eberstein et al, [28] Zöllner and Reichert [29] and Knocke et al, [30] based on the concept of videomicroscopy (combination of a microreactor and a microscope) to observe polymerizations performed with heterogeneous catalysts. Pater et al [31,32] described a new method for online observation of polymer particle growth, based on optical microscopy and infrared images. With the aid of infrared images, it was possible to determine the temperature of the particles surface in situ during the polymerization.…”

Comparison of catalytic ethylene polymerization in slurry and gas phase

“…Magnesium chloride with typically 10% TiCl 3 initially forms the continuous phase, but is distributed within the polymer after reaching yields higher than 1 g polymer / g catalyst, which can be the case < 1 second under "industrial" conditions. For the characterization of the single particle behaviour, see [24][25][26][27][28].…”

“…Therefore, softening and -in extreme case -melting of the growing particles is more critical for gas-phase polymerizations. Some authors have reported (using IR thermography) that the surface temperature of such particles could be up to 30°C higher than the bulk temperature [26]. Keeping the bulk temperature of the reactor constant and the particle temperature below the softening temperature of the polymer is the best arrangement for a catalytic polyolefin polymerization reactor [69].…”

Uma revisão sobre polimerização de olefinas usando catalisadores Ziegler-Natta heterogêneos

“…Esta técnica permite o acompanhamento simultâneo do crescimento da partícula polimérica e da cinética de polimerização em polimerizações em fase gasosa. Pater et al [82,83] descreveram um Recentemente, Ollala et al [110] e Tioni et al [111] usaram o SSR [105] para estudar o mecanismo de transferência de calor em polimerizações de eteno em fase gasosa, conduzidas com catalisadores heterogêneos. De acordo com os autores, a taxa de polimerização exerce um forte efeito sobre a fragmentação, apresentando forte dependência com as condições iniciais da polimerização.…”

“…Neste cenário, inúmeros trabalhos teóricos e/ou experimentais foram desenvolvidos com a finalidade de entender como a morfologia da partícula polimérica é afetada pelas condições de polimerização [23,27,30,36,41,53,55,57,58,61,62,69,80,81,83, . A Tabela 1 ilustra alguns dos fenômenos, que devem ser considerados Tabela 1.…”