(686a) Analysis and Optimization of Cyclopentadiene Dimerization Using Reactive-Distillation Modeling

Cyclopentadiene (CPD) and its dimer dicyclopentadiene (DCPD) are highly desired raw materials used throughout the chemical industry in a wide range of products such as polymeric materials, polyester resins, synthetic rubbers, solvents, fuels, fuel additives, etc. Conventional processes for making CPD typically produce C5 hydrocarbon stream(s) comprising CPD at a modest concentration, acyclic diolefins at significant concentrations, and mono olefins. Because many of the C5 species have close boiling points, form azeotropes, and are reactive at distillation temperatures, CPD recovery from the product mixture via conventional distillation is not industrially feasible. In conventional recovery schemes, CPD is recovered from other C5 hydrocarbons utilizing dimerization process(es) which causes CPD to undergo Diels-Alder reaction to produce DCPD that can easily be separated from the C5 hydrocarbons by conventional distillation. Unfortunately, CPD can also react with other diolefins present in the stream to produce co-dimers, which contaminate the DCPD. A process model that incorporates these reactions in distillation columns and other equipment is thus required for accurate analysis and optimization of DCPD product yield and purity.

A process model is developed in process flowsheeting software for CPD/DCPD recovery from other C5 hydrocarbons. A comprehensive kinetic model containing reactions of CPD with other C5 hydrocarbons including 1-pentene, 2-pentene, 1,3-pentadiene (piperylene), 2-methyl-1-butene, 2-methyl-2-butene, 2-methyl-1,3-butadiene (isoprene), and cyclopentene, and dimerization of piperylene and isoprene is used. Several isomers of these co-dimers were included in the kinetic model. The kinetic model was incorporated into recovery columns, dimerizer, etc. These recovery towers were modeled using reactive distillation model. Simulations were executed and sensitivity analysis was performed with respect to operating pressure and temperature, and residence times.

As the dimerization reaction rate is proportional to composition squared, co-dimers of only those monomers present in significant concentrations impacted final DCPD product purity. A shift in the purity is also observed based on the initial feed composition. The results show a trade-off between DCPD yield and purity. DCPD formation is limited by CPD-DCPD equilibrium which favors DCPD at low temperature but the rate of formation increases with temperature. Although higher DCPD yield can be achieved at high temperature for small residence time or low temperature with large residence time, the concentration of other co-dimers also increased. Sensitivity analysis on temperature and pressure provided more insights into a desirable operating zone.

This work demonstrates process intensification and modeling capabilities that enable optimal process design and product development. A reactive-distillation model results in more accurate prediction of product yield and purity. A sensitivity analysis helps in evaluating the operating conditions for the desired objective.