Catalytic trickle bed reactor (CTBR)

Chemical reactions requiring the simultaneous presence of a gas, a liquid and a catalytic solid are frequently encountered in industrial practice, notably for :

• hydrotreatment of petroleum fractions;

• hydrogenation and partial oxidation of various petrochemical compounds;

• the use of biological reactors.

To achieve contact between the three phases, the catalytic solid can be kept in suspension within the liquid, which is also contacted by the gas. Associated equipment includes three-phase bubble columns or stirred tanks, as well as three-phase fluidized beds.

The catalytic solid can also be arranged in a fixed bed, through which the gas and liquid flow. This technology is often preferred in industrial practice, both for its simplicity and for its robustness: there are no moving parts, and it does not require a solid separation step. What's more, commercial fixed-bed reactors can be very large: 10 to 30 m high, 1 to 4 m in diameter, with a characteristic catalytic particle size of around 1 to 3 mm. This configuration leads to a plug flow of the two phases, enabling high conversions to be achieved while optimizing selectivity. However, fixed-bed technology has a number of disadvantages linked to the difficulty of removing reaction heat and the inhomogeneity of flows on the reactor scale, the combination of which can lead to the formation of hot spots.