Monolithic agitator

Stirred-Tank Reactor with a Monolithic Agitator... 

The trickle-bed reactor (TBR) and slurry reactor (SR) are the most commonly used for multiphase reactions in the chemical industries. A new reactor type, the monolithic reactor (MR), offers many advantages. Therefore, these three types of reactors are discussed below in more detail. Their general characteristics are given in Table 5.4-44. With respect to slurry reactors, the focus will be on mechanically agitated slurry reactors (MASR) because these are more widely used in fine chemicals manufacture than column slurry reactors. 

FIGURE 15 Comparison of mass transfer group k[0 (s ) in structured monoliths and turbulent bubble columns and agitated tanks as a function of power input per unit of reactor volume, P/V (W/m ). 

Figure 15 shows data characterizing gas-liquid mass transfer (represented by values of kid) as a function of the power input for monoliths and typical turbulent contactors (agitated tanks and bubble columns). It is... 

The major disadvantages of using slurry reactors are the problems connected with agitation, filtration of solid catalyst, and reactor scale-up. Although slurry reactors provide the possibility of a rapid replacement of the decayed catalyst, the use of monolith reactors will eliminate costly catalyst recovery steps in industrial operation. The recovery steps are often a hazard when the catalyst is pyrophoric. 

Cybulski, A., Stankiewicz, A., Edvinsson Albers, R.K. and Moulijn, J.A. (1999), Monolithic reactors for fine chemicals industries A comparative analysis of a monolithic reactor and a mechanically agitated slurry reactor, Chem. Eng. Sci., 54, 2351-2358. 

In WAO with solid catalysts, three-phase reactors are used trickle bed, bubble slurry column, and bubble fixed-bed (monolith) or three-phase fluidized-bed reactors. When the catalyst is present in the liquid phase (homogeneous) or absent, two-phase reaetors such as bubble columns, jet-agitated reactors, and mechanically stirred reactor vessels are used. The limitations and advantages of these reactors for the application to WAO are listed in Table 10.7. 

The impregnation is performed generally from an aqueous solution of known concentration of the metal precursor. The procedure is to immerse overnight the coated monoliths into the precursor solution under mechanical agitation. The excess of the solution is then evaporated. When the precursor solution is completely evaporated, the impregnated monoliths are carefully dried before thermal treatment. This is carried out in a lab-made quartz reactor adapted to the size of the monolithic catalysts (Figure 8-c and d). For platinum, rhodium and iridium active phases, this treatment corresponds to a reduction under hydrogen flow diluted in helium. 

---