Multi-phase structured reactors

ECN is developing a novel type of reactor for the chemical industry. These structured reactors, based on creating a highly organized process in a large number of parallel channels, increase the effectiveness of chemical reactions. ECN research focuses on gas/liquid reactors, in particular for oxidation of hydrocarbons.  This type of reactions plays an important role in manufacturing of plastics such as polyurethanes, PET and engineering plastics. Although the principle of enhanced performance has been shown for many reactions, the largest challenges lie in the reactor design. Distributing gas/liquid over a large number of channels, handling of catalyst and developing reactor concepts which allow inexpensive manufacturing are key issues in our research.

Status of research

At ECN we are testing different industrially relevant reactions:

• A key installation is our Taylor-flow reactor, where we can test oxidation reactions in a single channel. As the channel has a length of 4 m and can be operated at high temperatures (60-200 ºC) and pressures up to 20 bar. Therefore a wide range of possible reactions can be tested in this facility. One of the processes we are currently investigating is the oxidation of ethylbenzene to the corresponding hydroperoxide. The project partners are  Shell and TU Delft.
• Another approach investigated in ECN is full-liquid oxidation, where oxygen is dissolved in hydrocarbon. Single-channel testing of full-liquid oxidation is used to test new catalysis. In cooperation with PDC and Hybrid Catalysis we are currently testing a highly selective "ship-in-a-bottle" catalyst for production of purified terephthalic acid (PTA). Working at challenging conditions (300 °C, up to 70 bar pressure) with pure oxygen requires highly specialize test equipment and well-developed safety consciousness in designing and operating equipment.

     In parallel we are developing several aspects including:

1.   Several aspects of scale -up of multi-phase reactors (such as distribution of gas and liquid);
2.   Development of catalyst coating technology for an industrial hydrogenation;
3.    Strategies of coping with catalyst degradation;
4.    Process design of systems based on structured reactors.  

Industrial relevance

Conventional reactors used for  gas/liquid reactions are trickle bed reactors, slurry reactors and bubble columns. The processes in these reactors are generally mass transfer limited with slow diffusion of gas through the liquid to the catalyst as the rate determining step. In addition it is difficult to control the process conditions within the reactor in order to achieve uniform temperature and processes. 

Mayor issue at in development of oxidation processes is to obtain a high per pass yield. Oxidation processes are generally characterized by a trade-off between selectivity and conversion. At high conversion the selectivity will become lower. Therefore many processes operate at low conversion (e.g. 10-30% per pass).

Break-through work at the Technical University Delft and other institutes has shown that Taylor flow or Segmented flow is a very stable gas/liquid flow which has most attractive mass transfer characteristics. Goal of the work at ECN on structured reactors is to design large-scale reactors which translate these attractive characteristics into economically and technically viable reactor designs.

More information?

For more information on structured reactors, please contact Arend de Groot (a.degroot@remove-this-part-ecn.nl)

Publications

L.A.Correia, R. Sumbharaju, D.F. Meyer, Y.C. van Delft, A. de Groot, Oxidation of ethylbenzene in a G-L Taylor Flow reactor, will be presented at CAMURE8 & ISMR-7, May 2011.