Apparatus for continuously carrying out heterogeneously catalyzed chemical reactions at elevated temperatures

1. An apparatus for continuous performance of heterogeneously catalyzed chemical reactions, wherein the apparatus comprises

a monomode microwave applicator configured to propagate microwave radiation in a direction of propagation;

a substantially microwave-transparent reaction tube having a longitudinal axis in the direction of propagation of the monomode microwave applicator, and having an irradiation zone operatively coupled to the monomode microwave applicator; and

an open-cell solid foam essentially filling the reaction tube in the irradiation zone, wherein the open-cell solid foam comprises a plurality of cells and a plurality of cell walls, the cells and the cell walls forming two continuous networks that penetrate one another, and has a porosity of at least 20%.

2. The apparatus as claimed in claim 1 , wherein the monomode microwave applicator comprises a hollow conductor in which the microwave-transparent reaction tube is disposed, the hollow conductor being operatively connected to a microwave generator.

3. The apparatus as claimed in claim 1 , in which the monomode microwave applicator is configured as a cavity resonator.

4. The apparatus as claimed in claim 1 , in which the monomode microwave applicator is configured as a cavity resonator of the reflection type.

5. The apparatus as claimed in claim 2 , in which the hollow conductor has a central axis of symmetry, and wherein the reaction tube is aligned axially with the central axis of symmetry of the hollow conductor.

6. The apparatus as claimed in claim 3 , wherein the cavity resonator comprises a coaxial transition of the microwaves.

7. The apparatus as claimed in claim 3 , in which the cavity resonator is configured such that it can be operated in E 01n mode with respect to the microwave radiation where n is an integer from 1 to 200.

8. The apparatus as claimed in claim 3 , in which the cavity resonator is configured such that a standing wave with respect to the microwave radiation can form therein.

9. The apparatus as claimed in claim 1 , in which the open-cell solid foam consists of a ceramic material which is itself catalytically active.

10. The apparatus as claimed in claim 1 , in which the open-cell solid foam is a ceramic material which bears a different catalytically active species.

11. The apparatus as claimed in claim 1 , in which the open-cell solid foam consists of a catalytically active metal.

12. The apparatus as claimed in claim 1 , in which the pore count of the open-cell solid foam, determined on the basis of ASTM D3576, is between 1 and 150 ppi.

13. The apparatus as claimed in claim 1 , in which the porosity of the open-cell solid foam is 50% to 90%.

14. The apparatus as claimed in claim 1 , in which the pore size of the open-cell solid foam is between 0.01 mm and 1 cm.

15. The apparatus as claimed in claim 1 , in which the average strength of the open-cell solid foam, determinable by means of die indentation, is between 100 and 15 000 N.

16. The apparatus as claimed in claim 1 , in which the open-cell solid foam bears or consists of catalytically active species, and is configured such that a reaction mixture to be converted can flow through it.

17. The apparatus as claimed in claim 1 , wherein the open-cell solid foam is formed from a catalytically active material.

18. The apparatus as claimed in claim 1 , wherein the open-cell solid foam is formed from a material into which catalytically active species have been intercalated and/or which has been coated or impregnated with catalytically active species.

19. The apparatus as claimed in claim 1 , wherein the open-cell solid foam is formed from a ceramic material into which catalytically active species have been intercalated and/or which has been coated or impregnated with catalytically active species.

20. The apparatus as claimed in claim 1 , wherein the open-core solid foam is fixed in the reaction tube as a core.