More than 100 industrial scale catalytic distillations are operated worldwide today. Most of these plants started up less than 15 years ago. In most cases, variable cost, capital expenditure and energy requirements are reduced by 20 % or more, compared to the classic set-up of a reactor followed by distillation. This rapid invasion of a new unit operation into the petrochemical processing industry is mainly due to technology provider CDTECH with tall pilot plant facilities, reducing commercial scale introduction to low risk levels.
Chemical manufacturing companies have also developed their own specific catalytic distillations by their own research and development. These companies, both on their own and in consortia, also developed heuristic process synthesis rules and expert software to identify the attractiveness and technical feasibility of reactive (catalytic) distillation. The rules and expert software will be presented and supported by examples. Moreover a sustainable development scorecard is used to highlight the potential contributions of reactive distillation to sustainable development by the process industry.
Industrial catalytic distillation systems comprise homogeneous and heterogeneous catalysed, irreversible and reversible reactions, covering large ranges of reactions, notably hydrogenations, esterifications and etherification. Various commercial methods for packing heterogeneous catalyst in the columns are now available.
Academic research has produced methods to identify the feasibility of reactive distillation, to determine the feed locations, to select packing types, to sequence columns optimally and also produced methods to design, optimise and control the columns with steady state and dynamic simulation models.
The forecast for the application of catalytic (reactive) distillation in the petrochemical industry, is that many reactions, homogeneous and heterogeneously catalysed, equilibrium and irreversible, will be implemented commercially. Moreover in some separations, selective reversible chemical reactions will be applied in reactive extractive distillation set-ups to replace expensive distillations. Examples of industrially patented cases for these will be presented. Barriers for commercial implementation and how to overcome them will also be indicated.
The forecast for academic research is that process synthesis heuristics on feasibility and attractiveness will be developed for irreversible reactions. Heuristics will be generated to combine catalytic reaction and dividing wall columns and or combining them with heat exchangers inside the column. Design and simulation tools will be developed that include reactions, residence time distribution, mass transfer, heat transfer and impulse transfer.
Catalytic distillation, also called reactive distillation, can be considered as reaction and distillation combined into one new unit operation. Distillation itself is here considered in the wide sense, i.e. the separation by use of vapour-liquid composition difference. So it includes distillation columns, flashers, strippers and condensers. The reactions in reactive distillation considered include heterogeneous catalysis reactions, homogeneous catalysis reactions, and thermal (non-catalyst)reactions.
In nearly all cases reactions take place in the liquid phase, but reactions taking place in the gas phase and locate the catalyst in the vapour phase of the column is conceivable.
CDTECH, the major commercial process technology provider, licensed up to now 123 commercial Catalytic Distillation units [Loescher, 2005]
