(49a) Modeling a Low-Severity Ethylene Oligomerization Process

In order to take advantage of low feedstock costs, the Synfuels International / Byogy Renewables Biojet process uses crude ethylene as an intermediate to produce heavier olefins.  This oligomerization process is challenging to operate and simulate.  The highly exothermic nature of the reaction necessitates a heat-exchanger reactor design and multiple sections.  In this reactor, a highly active catalyst is chosen to convert the ethylene into intermediate length olefins.  While the distribution is not as important as the conversion, longer average chain length leads to more deactivation due to waxy buildup. Because of this, the shortest oligomer, butylene is targeted.

The modeling of this process creates the potential for a large number of species, both in terms of hydrocarbon length and type.  In addition, the number of potential reactions (oligomerization, cracking, hydrogenation, aromatization, etc.) is substantial.  It is desired to rapidly produce a model of the process to enable process design and optimization of larger scale reactors from existing lab and pilot scale data.  The scope of these reactions is included in the kinetic technology of Bryan Research & Engineering, Inc.’s AutoKinetic Reactors in their ProMax simulator.  This allows the user to easily test a large number of combinations of reactor designs and conditions.  In addition, with experimental data, the reactor model can be tuned to more closely replicate the process catalyst and conditions.  In this way, the process has been studied to give a reactor design with a minimum capital cost for a given conversion or yield, and to give maximum yield for a given reactor layout. This study has also identified and mitigated temperature and composition sensitive regions of the reactor.