Hydrogen interphase

The effect of physical processes on reactor performance is more complex than for two-phase systems because both gas-liquid and liquid-solid interphase transport effects may be coupled with the intrinsic rate. The most common types of three-phase reactors are the slurry and trickle-bed reactors. These have found wide applications in the petroleum industry. A slurry reactor is a multi-phase flow reactor in which the reactant gas is bubbled through a solution containing solid catalyst particles. The reactor may operate continuously as a steady flow system with respect to both gas and liquid phases. Alternatively, a fixed charge of liquid is initially added to the stirred vessel, and the gas is continuously added such that the reactor is batch with respect to the liquid phase. This method is used in some hydrogenation reactions such as hydrogenation of oils in a slurry of nickel catalyst particles. Figure 4-15 shows a slurry-type reactor used for polymerization of ethylene in a sluiTy of solid catalyst particles in a solvent of cyclohexane. 

QCMB RAM SBR SEI SEM SERS SFL SHE SLI SNIFTIRS quartz crystal microbalance rechargeable alkaline manganese dioxide-zinc styrene-butadiene rubber solid electrolyte interphase scanning electron microscopy surface enhanced Raman spectroscopy sulfolane-based electrolyte standard hydrogen electrode starter-light-ignition subtractively normalized interfacial Fourier transform infrared... 

FIGURE 35.1 Oxygen (solid line) and hydrogen (dashed line) density profiles from a simulation of water close to a Pt(100)-water interphase. (From Berkowitz et ah, 1999, with permission from CRC Press LLC via CCC.)... 

The potential production of sulfide depends on the biofilm thickness. If the flow velocity in a pressure main is over 0.8-1 ms-1, the corresponding biofilm is rather thin, typically 100-300 pm. However, high velocities also reduce the thickness of the diffusional boundary layer and the resistance against transport of substrates and products across the biofilm/water interphase. Totally, a high flow velocity will normally reduce the potential for sulfide formation. Furthermore, the flow conditions affect the air-water exchange processes, e.g., the emission of hydrogen sulfide (cf. Chapter 4). 

Figure 4.3. Structure of water in the interphase. At a negatively charged electrode, there is an excess of water dipoles with their positive hydrogen ends oriented toward the metal.

The standard hydrogen electrode (Fig. 5.5) is chosen as the reference electrode when a series of relative electrode potentials is presented. By convention, the standard potential of this electrode is set to zero. Connecting this reference electrode with other electrodes into a cell, one can determine a series of relative values of electrode potentials (potential differences across interphases). For example, consider the cell shown in Figure 5.9. This cell can be represented schematically in the following way ... 

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