Modelling a process for dimerisation of 2-methylpropene

Isooctane can be used to replace methyl-tert-butyl ether (MTBE) as a fuel additive. Isooctane is hydrogenated from isooctene, which is produced by dimerizing 2-methylpropene. In dimerization, two 2-methylpropene molecules react on ion-exchange resin catalyst to produce isooctene isomers (2,4,4-trimethyl-1-pentene, 2,4,4-trimethyl-2-pentene). Presence of 2-methyl-2-propanol (TBA) improves reaction selectivity. Trimers and tetramers are formed as side products. Water and alkenes have reaction equilibrium with corresponding alcohols. The process configuration for isooctene production is a side reactor concept, and consists of reactor part, separation part (distillation tower) and a recycle structure (Figure 1). Units of miniplant at Helsinki University of Technology imitates the actual units of the isooctene production line in smaller scale, providing valuable information about the process and about the behaviour of individual units, as well as about the dynamics and operability of the process. Ideology behind Miniplant is to separate thermodynamical models from hardware-specific models, so that they could be used as such in other contexts, e.g. in industrial scale. In the specific case of 2-methylpropene dimerisation the key thermodynamical models are vapour-liquid and liquid-liquid equilibrium as well as reaction kinetics. Hardware specific models include distillation column with spring-shaped packings and tubular catalytic reactor with heating coil and a thermowell. Developing these models through experiments and simulations was the primary target of this work.reviewe