Mechanism of Fouling in Slurry Polymerization Reactors of Olefins

Abstract

Slurry polymerization processes are used to produce high-density polyethylene of tailor-made properties. The formation of fouling in slurry reactors as well as in its peripheral equipment, such as external heat exchangers, is attributed either to the deposition of oligomers (wax) or to the buildup of electrical charge in small polymer particles. In order to understand the causes of fouling formation, samples were gathered from polymerization processes and they were characterized by microscopy in this research. The results show the existence of an aluminum-based layer as a common element in the samples analyzed. It is supposed that such a layer is formed by the reaction of trialkyl aluminum and water residues during the start-up procedure of the plant.

Influence of Pore Structure and Metal‐Node Geometry on the Polymerization of Ethylene over Cr‐Based Metal–Organic Frameworks

“…Naturally, the PE morphology is highly important for assessing post‐reaction processability as well as preventing reactor fouling, often related to expensive reactor downtimes [62] . From an industrial point of view, “good” is considered spherical with narrow particle size distributions, which is directly related to high bulk density, controlled porosity, controlled internal composition and high process flowability [63, 64] …”

“…platelets, spheroids and fibers) is obtained. Irregularities on the reactor wall and/or stirrer now predominantly act as crystallization points for the (relatively small) waxes formed over the homogeneous Cr sites, after which PE continues growing [62] …”

“…Irregularities on the reactor wall and/ors tirrer now predominantly act as crystallization points for the (relativelys mall) waxes formed over the homogeneous Cr sites, after which PE continues growing. [62] If anything, theseS EM images highlight the importance of selecting the appropriate MOF as ethylene polymerization platform for attainingd esirable PE morphologies. Additionally,a nd possibly more importantly,t he simultaneous polymerization over heterogeneous Cr sites and homogeneous Cr sites is not detrimental for the final morphology,i nferringt hat even for the dissolveda ctive sites, and PE materials, the MOF crystallites act as crystallization point.…”

“…Naturally, the PE morphologyi sh ighly important for assessing post-reaction processability as well as preventing reactor fouling, often relatedt oe xpensive reactor downtimes. [62] From an industrial point of view," good" is considered spherical with narrow particle size distributions,w hich is directly related to high bulk density,c ontrolled porosity,c ontrolled internal compositionand high process flowability. [63,64] Figure 3s hows the obtainedP Em aterials obtained from the ethylene polymerization reactions with the MOFs, and clearly demonstrates that one can affect the final PE morphologyb y selectingt he proper MOF polymerization template, at least under the here described reaction conditions.…”

How Chain Transfer Leads to a Uniform Polymer Particle Morphology and Prevents Reactor Fouling

“…1−3 Reactor fouling can still be an issue but this is mainly due to electrostatics, the formation of hot spots, or deposition of waxes or partly hydrolyzed aluminum alkyls on the reactor wall. 4 Initial research efforts directed toward the development of new SSCs are generally performed using unsupported catalysts at relatively low temperatures, conditions that are very different from any of the industrially applied ones: either slurry or gas phase using supported SSCs or high-temperature solution phase using unsupported SSCs. During such low-temperature lab-scale experiments the polymerization starts homogeneously but gradually more and more of the semicrystalline polymer precipitates from the solution, typically forming highly irregular polymer particles, chunks, sheets, and fines.…”