Membrane microreactors permeability

Scheme for membrane microreactors for multiphase reactions, that is, gas-liquid reactions (left), a PSS supported dense PDMS gas-permeable membrane with CNFs as a catalyst support (right). (Aran eta ., 2011) (Copyright permission 2011 Elsevier). 

However, the tube-in-tube reactor is not only used for gas—hquid reactions. The group of Kappe used the gas-permeable membrane to prepare the highly toxic and explosive diazomethane (CH2N2) in a safe manner. The diazomethane was formed from N-methyl-JV-nitroso-p-toluenesulfona-mide (Diazald) and KOH in the inner channel of the microreactor and subsequently diffused through the hydrophobic membrane where it formed the desired products 38, 40, and 42 in the outer chamber. The potential... 

Figure 1.5 Microreactor with permeable porous silicon membrane (squares of 350-750pm, thickness 70pm) coated with Pd (via immersion) with heating filament and temperature sensor for CO measurements up to 140°C. Reprinted from [37], Copyright 2002, with permission from Elsevier.

In order to control highly exothermic catalytic partial oxidation reactions, small time constants for heating and cooling of gases are required. Microreactors equipped with a reaction chaimel that is capped on one side with a flat, thin, non-permeable membrane ( 1 pm thick) are very suitable for gas-phase reactions at temperatures... 

Two groups described a tube-in-tube gas-liquid microreactor - a microporous tube-in-tube microchannel reactor [102] (Figure 9.27) and a reactor/saturation module based on a gas-permeable Teflon AF-2400 membrane [103]. 

Immobilization of Enzyme in Capillary Microreactor by Entrapment Entrapment technique involves the entrapment of enzymes in gel matrix. The enzyme is mixed with gel formation ingredients and upon gel formation, the enzyme remains trapped in the matrix. Another form of entrapment is the formation of membrane around the droplet of enzyme, which is typically in solution. Immobilization by entrapment differs from adsorption and covalent bonding in that enzymes are free in solution but restricted in movement by the lattice structure of a gel. The membrane must be permeable to diffusion of substrate and product molecules... 

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