Macroporous catalyst films

Fig. 2. Models of the primary particle (a) and polymer grain (b) for the analysis of the role of monomer diffusion to tbe catalyst surface, (a) 1—catalyst 2—polymer film, (b) 1—micrograin 2—macropore.

Another use of nonpermselective membranes is in multiphase organic reactions involving trickle-bed type reactors (Harold et al., 1989, 1994 Cini and Harold, 1991). The reactor consists essentially of a hollow macroporous membrane tube coated on the inside with a hollow mesoporous catalyst layer, as shown in Figure 24.Id. Liquid and gas are allowed to flow on opposite sides of the membrane. Because the gas comes into direct contact with the liquid-fllled catalyst, it resembles a trickle-bed reactor. However, because there is no separate liquid film to hamper the supply of gas to the catalyst sites, it performs better than the traditional trickle-bed reactor. 

In particular, for the synthesis of optically pure chemicals, several immobilization techniques have been shown to give stable and active chiral heterogeneous catalysts. A step further has been carried out by Choi et al. [342] who immobilized chiral Co(III) complexes on ZSM-5/Anodisc membranes for the hydrolytic kinetic resolution of terminal epoxides. The salen catalyst, loaded into the macroporous matrix of Anodise by impregnation under vacuum, must exit near the interface of ZSM-5 film to contact with both biphasic reactants such as epoxides and water. Furthermore, the loading of chiral catalyst remains constant during reaction because it cannot diffuse into the pore channel of ZSM-5 crystals and is insoluble in water. The catalytic zeolite composite membrane obtained acts as liquid-liquid contactor, which combines the chemical reaction with the continuous extraction of products simultaneously (see Figure 11.28) the... 

It was found that these dopants had a significant effect on the structure and the mechanical stabilities of the obtained opaline films. With selection of suitable dopants, PANI composite inverse opals could be fabricated with very high quality. The obtained films remained electroactive in buffer solutions of neutral pH. Together with their huge surface area, they would be ideal candidates for biosensing applications. Such macroporous structures were used as electro catalysts for the oxidation of reduced / -nicotinamide adenine dinucleotide (NADH]. This showed that the electrocatalytic efficiency of the inverse opline film was much higher than that of an unpatterned film. 

Adsorption equilibria are normally considered in connection with processes occurring in porous media filters, catalysts, adsorbents, chromatographs, and rock of petroleum reservoirs. In macroporous and mesoporous media, adsorption is normally accompanied by another surface phenomenon, the capillary condensation. These two types of surface phenomena are closely connected because they are both produced by surface forces. On the other hand, these phenomena are relatively independent and may, to some extent, be discussed separately [3]. Moreover, the description of the coexistence of the adsorbed films and capillary condensate in the same capillary is a nontrivial problem. We present capillary condensation and adsorption separately, although their eommon roots are discussed in Section II. The (more or less) comprehensive description of the thermodynamics of multicomponent capillary condensation... 

---