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

Abstract

A specially conceived packed-bed stopped flow minireactor (3 mL) suitable for short gas phase catalytic reactions has been used to study the start-up of ethylene homopolymerization with a supported metallocene catalyst. Focus has been put on the heat transfer characteristics of the supported catalysts and on understanding the relationship between the initial rate and the relative gas/particle velocities and the influence of particle parameters in the packed bed. We performed a comprehensive study on the influence of various physical parameters on the heat transfer regime at start up conditions. The catalyst activity as well as the polymer morphology is shown to be dependent on heat transfer regime. The knowledge thus obtained is applicable to industrial problems like catalyst injection in fluidized beds and helps preventing experimental artifacts due to overheating in following studies.

Condensed Mode Cooling in Ethylene Polymerisation: Droplet Evaporation

“…It is well-known that the nature of the gas phase in an FBR can have a significant impact on heat transfer if the standard inert component of nitrogen is replaced by a gas such as helium [13] or propane [14] . Since the evaporation process is quite rapid the gas phase will be quite rich in the heavier ICA.…”

A 2‐D observer to estimate the reaction rate in a stopped flow fixed bed reactor for gas phase olefin polymerization

“…The laboratory scale, stainless steel, fixed bed reactor contains a mixture of catalyst, and inert solid (see Tioni et al for details of the reactor preparation and setup). The bed is 1 cm long by 2 cm diameter and is held in place by two 15 µm, stainless steel frits of thickness 3 mm.…”

“…Not only is the process dependant on the catalyst breakup occurring in a controlled manner but also the morphology of the final polymer particles is determined at this early stage while particle scale heat‐ and mass‐transfer resistances are at a maximum due to the small external surface area of the initial catalyst. To study these effects, a packed bed reactor for the study of the first instants of gas phase polyolefin polymerization was designed and optimized . The reactor was designed to perform experiments of very short and precise timescales at close to industrial conditions with relative gas flow rates similar to those experienced by the particles in a fluidized bed reactor.…”

Specialised tools for a better comprehension of olefin polymerisation reactors

“…This allows catalyst poisoning and complete removal of residual monomer even from the smaller pores of the catalyst thus stopping immediately the reaction. More details are available in a paper by Tioni et al [10] The reaction conditions used throughout this work are (unless specified):…”

“…This allows catalyst poisoning and complete removal of residual monomer even from the smaller pores of the catalyst thus stopping immediately the reaction. More details are available in a paper by Tioni et al The reaction conditions used throughout this work are (unless specified): Superficial gas velocity of 5‐20 cm/s; 9 bar of total pressure with 3 bars of helium in the feed and 6 bars of ethylene; Use of fine NaCl as inert catalyst diluent; Catalyst mass between 30 and 80 mg according to reaction time and activity. A zirconene ( rac ‐EtInd 2 ZrCl 2 ) supported on Grace‐Davison 948 silica prepared as described previously …”