Condensed Mode Cooling for Ethylene Polymerization: Part IV. The Effect of Temperature in the Presence of Induced Condensing Agents

Abstract

An experimental investigation of the impact of changes in temperature on the observed rate of polymerization of ethylene in the gas phase using a commercial Ziegler–Natta catalyst in the presence of induced condensing agents (ICAs) reveals some unexpected behavior. In the absence of ICA, the effect of temperature is as expected: raising the temperature of the gas phase from 70 to 90 °C causes the observed rate of polymerization to increase monotonically. It is demonstrated in the past that ICA can increase rate of polymerization of the ethylene in the gas phase due to a cosolubility effect. However, in the current study, it is shown that when ICA is present in the reactor, the same increase in temperature can actually lead to an observable decrease in the reaction rate under certain conditions of temperature and pressure. This is attributed to a lower impact of the ICA on the solubility of ethylene in the amorphous phase of the high‐density polyethylene in the reactor at higher temperatures. An order of magnitude analysis also reveals that the presence of ICA can have an impact on the particle temperature as well.

Condensed Mode Cooling of Ethylene Polymerization in Fluidized Bed Reactors

“…Finally, it has also been shown recently that changing the temperature of the polymerization when using SDM can impact the observed polymerization rates differently than in dry mode . As expected, Figure 22 a shows that when homopolymerizing ethylene in DM, increasing the temperature from 70 °C to 90 °C leads to higher observed rates of polymerization.…”

“…The concept can be seen form the data in Figure 13 , which shows two different (experiment) thermograms of an HDPE powder . The blue curve is for dried powder, and the black one for the same HDPE powder, but with the sample capsule containing 20 wt% (with respect to polymer) of n ‐hexane.…”

“…Pressure 7 bar ethylene, no hydrogen, commercial Ziegler–Natta catalyst. Adapted with permission . Copyright 2017, Wiley‐VCH.…”

Computational fluid dynamics simulation of gas–liquid–solid polyethylene fluidized bed reactors incorporating with a dynamic polymerization kinetic model

“…Under condensed‐mode, more isopentane in the gas inlet results in the increase of liquid content in the reactor, hence, the removal of more heat can be achieved through liquid vaporization process to decrease the bed temperature. Although the bed temperature decreases as isopentane inlet content improves, the gas species reaction rates still increase, which is consistent with the experiments results in published literature . This observation is attributed to the fact that the reaction rates of components in three‐phase polyethylene reactors are affected not only by the bed temperature but also the condensed isopentane under condensed‐mode.…”

Applied Thermodynamics for Process Modeling in Catalytic Gas Phase Olefin Polymerization Reactors

“…For instance, it has been known that the presence of alkanes or alkenes can enhance the solubility of ethylene in LLDPE, while the presence of ethylene decreases the solubility of the heavier components in the polymer phase 15,16. It has been shown experimentally that adding alkanes in an olefin polymerization system has a pronounced effect on polymerization rate, catalyst mileage, and polymer properties 17–19…”