Many chemical reactions cannot be run to complete conversion of the reactants into products as conversion is limited by equilibrium or selectivity. The separation and reactant recycle requires vast amounts of energy and often generates a significant amount of waste products that can create an environmental problem. Coupling of reaction and separation (membrane or adsorption) within one single unit allows us to cross the boundaries set by selectivity or equilibrium conversion and can lead to higher or sometimes to complete conversion and purer product in a single pass.
Esterification reactions for the production of important chemicals such as methyl acetate, dibutylphtalate and various other plasticisers are traditionally carried out in the presence of a strong acid (e.g. oleic acid), but can also be catalysed by ion exchange resins such as polystyrene divinylbenzene copolymers cross linked with sulphonic groups. The water formed is then preferentially sorbed in the resin and the reaction, normally limited by equilibrium, can now run to completion.
In partial oxidation of hydrocarbons (e.g. cyclohexane) to produce oxygenates (cyclohexanol and cyclohexanone) with homogeneous catalysis by Co-salts conversion is limited to 4 - 6 % so as to limit the formation of side products ( less than 20%). Oxygenates are important intermediates in the production of polyamides, polyesters and plasticisers. When using an FePhthalocyanine complex immobilised in a Y-zeolite, in turn embedded in a PDMS membrane as a catalyst, high conversions above 35% have already been obtained with 99% selectivity towards the desired oxygenates.
The main objectives of the partners are:
- the identification of a number of classes of reactions that can benefit from such operation; the development of suitable catalyst and membrane materials
- the development of integrated heterogeneously catalysed reaction/separation units for liquid phase reactions limited by equilibrium or by selectivity and homogeneously catalysed in traditional processes
- the application of this methodology to two well chosen and - collection of data for technical, economic, energetic and environmental evaluation of such integrated reactor/separation units; in the case of the chromatographic separation a pilot unit will also be used.
The university partners have broad experience in these highly innovative processes (Joule 2.2.1.A.1.1.) that enable immobilisation of the homogeneous catalyst, leading to reduced recycling of reactants and separation of products and hence to lower energy consumption, process intensification, environmentally benign operation and potentially increased safety for some reactions. The industrial partners in this project have large scale processes of the type mentioned here and could rapidly use the results of this study as a basis for further development or directly in their plants.
Funding SchemeCSC - Cost-sharing contracts
38678 Clausthal - Zellerfeld