A Novel Hydrogeneation Reactor

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Description And Advantages

Chemists at Nottingham University have designed a continuous hydrogenation reactor that uses supercritical CO2, "the green solvent", which will be scaled up to a $2m pilot plant this month by Company Thomas Swan. Chemical reactions in the liquid phase are faster and easier to control because the reacting molecules mix more readily. Many industrial processes involve dissolving solid reactants in organic solvents to achieve liquid conditions. These solvents are toxic, flammable, difficult to recycle and usually very volatile.

Supercritical CO2 behaves like a fluid if pressurized whilst kept above its critical temperature of 31°C. It enters a relatively dense, liquid like phase that remains highly compressible and mixes easily with gases. The hydrogenation process consists of a mixing chamber where hydrogen gas, supercritical CO2 and the substrate are mixed before passing into a reactor containing a catalyst. The hydrogen, completely miscible with supercritical fluid, is thus brought into intimate contact with the substrate so that they are well mixed. The supercritical fluid has very low viscosity so there is excellent contact between the liquid mixture and the catalyst in the reactor-crucial for an efficient reaction.


The Chemical Engineer, March 2001