Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Multichannel Reactor System

Experiments are performed in a structured packed bed reactor that has been developed for the selective oxidation of organic liquids to produce pharmaceutical products. Molecular oxygen is used as the oxidant, providing a cleaner processing route, than in established methods. The structured assembly consists of an integrated heat exchange system, a gas/liquid mixing zone, and provision for reactant injection. To illustrate the application, the selective oxidation of benzyl alcohol to benzaldehyde was studied.
In the first phase of work, experiments are performed with a Ru/Al2O3 catalyst. This enabled the operating characteristics of the reacting system to be established. In the second phase, experiments were performed on a Pt/C catalyst that was selected by the project partners to act as the reference catalyst for the multi channel reactor experiments.

1ST PHASE: The reactor consisted of parallel reaction channels (10 cm long and square shaped) that were packed with Ru/Al2O3 (0.9 %wt Ru) catalyst particles. From experiments in three different sizes of channel: 2 mm x 2 mm, 3 mm x 3 mm, and 5 mm x 5 mm (at P = 8 bar, T = 388 K, with a liquid and gas flows L = 3.2 kg m-2 s-1, G = 1.35 x 10-2 kg m-2 s-1), it was shown that in a short 10 cm length of channel, a product yield up to ca. 29 % (with minimum 99.5 % selectivity) could be obtained. Conversions were highest in the 3 x 3 mm channel. From the experiments with the reactor mounted both in horizontal and vertical planes, it was shown that gravitational influences are minor.
The choice of solvent was shown to affect the yield of benzaldehyde. The highest yield was with toluene; the application of dioxane/water mixture (70/30 by vol.) and N-methyl pyrrolidone (NMP) not only decreased the yield by factor 2, but NMP also caused deactivation of the catalyst.
Hydrodynamic characteristics of the system were evaluated to establish pressure drop, effectiveness of gas/liquid mixing, and to confirm the nature of the gas-liquid flow regime. Operating the reactor at: 8 bar, 388 K, with a liquid flow L = 3.2 kg m-2 s-1 and gas flows G > 2.5 x 10-2 kg m-2 s-1; it was shown that even in a short 10 cm length of channel, a product yield of up to 55% (with 99.7% selectivity) could be obtained. Although the adiabatic temperature rise at 55% yield is estimated to be ca. 180 K, the reactor was shown to operate isothermally, due to the efficient removal of heat through the integrated micro heat exchange system. It was concluded that this structured design of a reactor showed considerable promise for the development of cleaner oxidation processes.
Conversions up to 25% per 10 cm bed length were measured, giving TOF = 800 h-1, which is close to that reported in the literature for the same catalyst. By controlling the point of injection of oxygen into the reactor an increase in the yield of benzaldehyde formation was achieved.

2ND PHASE: Experiments were then performed using a Pt/C catalyst (3% Pt by weight) and pure dioxane or dioxane/water mixtures as solvents. In spite of the two-fold increase in the rate of oxidation (as the flowrate of oxygen was changed) a similar behaviour was observed. Faster kinetics, and therefore faster release of energy did not influence the temperature profile in the reactor (isothermal operation was maintained due to effective heat transfer). Despite higher rates of reaction the process soon became limited by chemical kinetics and not by mass transfer.
Based on the results of these experiments a pilot scale reactor has been constructed consisting of 192 channels, with total length of catalytic bed equal 0.5 m. This has the capacity to produce 2 kg h-1 of product (aldehyde).

D.V. Bavykin, A.A. Lapkin, S.T. Kolaczkowski, P.K. Plucinski, Selective oxidation of alcohols in a continuous multifunctional reactor: ruthenium oxide catalysed oxidation of benzyl alcohol, Applied Catalysis, 288, 175-184 (2005).
P.K. Plucinski, D.V. Bavykin, S.T. Kolaczkowski, A.A. Lapkin, Application of a structured multifunctional reactor for the oxidation of a liquid organic feedstock, Catalysis Today, 105 479 483 (2005).
D.V. Bavykin, S.T. Kolaczkowski, A.A. Lapkin, P.K. Plucinski, Compact multichannel reactor for liquid phase oxidation of organic feedstocks, Proceedings of 7th World Congress of Chemical Engineering, IchemE, 2005.
D.V. Bavykin, A.A. Lapkin, P.K. Plucinski, J.M. Friedrich, F.C. Walsh, TiO2 nanotube supported ruthenium (III) hydrated oxide: A highly active catalyst for selective oxidation of alcohols with oxygen, Journal of Catalysis, 235, 10-17 (2005).
P.K. Plucinski, D.V. Bavykin, S.T. Kolaczkowski, A.A. Lapkin, Liquid phase oxidation of organic feedstock in a compact multichannel reactor, Ind. Eng. Chem. Res., 44, 9683-9690 (2005).

Verwandte Informationen

Reported by

Claverton Down
United Kingdom
Folgen Sie uns auf: RSS Facebook Twitter YouTube Verwaltet vom Amt für Veröffentlichungen der EU Nach oben