During the past decades, reactive distillation has received intensive attention due to the well known benefits of integrating distillation with reaction in a single unit. Significant capital savings, improved conversion and selectivity, avoidance of azeotropes, together with heat integration are some of the main advantages of using reactive distillation. Many applications have proven to be economically advantageous by using reactive distillation (e.g. MTBE and TAME synthesis, production of methyl-acetate, manufacture of di-isopropyl-ether, oligomerisation of linear butenes and others). Whereas there are many procedures available for the synthesis of non-reactive columns or reactive-separation systems, the synthesis of reactive distillation columns is still a challenge, due to the complexity and the high number of design parameters involved. Available conceptual design methods generally address three (or four) components and fully reactive columns, but there is still a lack of systematic conceptual design methods for more general column configurations and for multi-component systems. The aim of this work is to develop a methodology to identify promising column configurations and to obtain column design parameters (number of reactive and non-reactive stages, reflux and reboil ratios, feed condition) for a given feed mixture and a set of desired products. A new systematic design method for reactive systems reaching equilibrium allows the analysis of the impact of different configurations (fully reactive or hybrid columns) and feed policies (single- or double-feed columns) on column performance. The methodology is extended to account for kinetically-controlled reactions in synthesis and design of reactive distillation columns. Systems with two degrees of freedom (according to the Gibbs phase rule) were considered for equilibrium reactions, and ternary and quaternary systems for kinetically-controlled reactions. Reactive distillation column designs generated by the methodology are presented as illustrative examples. Their predicted performances are shown to be in good agreement with those predicted by rigorous simulation using HYSYS. The approach can easily be automated and typically generates multiple designs, allowing a design engineer to efficiently compare various design options including hybrid and fully reactive columns, single- and double-feed configurations, and different sets of operating parameters for a given column configuration. The new methodology developed in this work facilitates a stepchange in conceptual design practice, offering a systematic and easy to use tool for the synthesis and design of reactive distillation columns.

A reactive distillation column for the alkylation of benzene with long chain linear olefin was studied. The study involved design, construction, experimentation, and simulation of the column. Establishing the design required study of reaction rates, thermodynamic relationships, and packing structures. A heuristic was developed for the design of such columns. This heuristic involved estimating an amount of catalyst loading and subsequently determining the operating parameters for a column. This method is particularly applicable to systems with high concentrations of inert feeds. A column was constructed following the design. Data was collected from the column and compared to simulations. The simulations were performed with Aspen Plus RADFRAC. In this manner, the data was used to validate the commercial steady state models for reactive distillation. In addition, dynamic simulations of the system were performed. These dynamic simulations provided insight into more design considerations. For example, steady state simulations indicated an optimal feed stage based on steady state conversion of the olefin. However, the dynamic simulations showed a potential disadvantage to the utilization of the optimal feed stage. With some disturbances, a column configured with the feed stage with the highest steady state conversion also deviated from the steady state faster and with greater amplitude than other configurations. These considerations were further explored in developing a control scheme for reactive distillation columns. Control of reactive distillation differs from traditional distillation in that one control variable is conversion. Traditional distillation generally focuses on production rates and product purity. To this end, control schemes were analyzed and dynamic simulations were performed. These simulations showed an advantage to a variable pairing in which duty is paired with conversion. The conversion was inferred from a stage temperature in the reactive zone. In addition, distillate rate may be paired with product composition. In conclusion, the reactive distillation column design for long chain olefin alkylation of benzene requires careful estimation of catalyst requirements and valid simulation tools. In addition, dynamic response should be considered in the design. Finally, a simple inferential control scheme may be adequate. / text