Continuous film reactor

Technology Description Hybrid reactors, as the name implies, are a combination of suspended growth and fixed-film reactor principles. In these systems, the fixed film is submerged and the reactor contents are continuously stirred. A large amount of biomass is maintained in the system. 

As a rule, sulfonation takes place continually in a cascade or a falling film reactor (Table 14) at about 50-70°C. The S03 is steadily diluted to a concentration of 5-10 vol % with air or an inert gas. The LAB conversion reaches a value between 92% and 98% [156,157]. Mixing of the already formed alkyl-benzenes with fresh S03 leads to undesired highly sulfonated byproducts. In order to prevent these side reactions, all processes operate concurrently. 

The thin film reactor for the continuous sulfonation of fatty acid esters was introduced by the Witco Technical Center in Oakland, New Jersey [46]. Hurl-bert et al. designed this type of reactor for small-scale sulfonation with S03 [47,48]. The reaction partners could be filled into the reactor through three inlets. One was for the carrier gas (air or nitrogen), one for the liquefied ester that is picked up from the carrier gas, and the last one was for the vaporized S03. The ester and the S03 reacted in a turbulent liquid film. Details of this reactor are given by Kapur et al. [46]. 

The detergent industry requires process equipment having high operation flexibility, low energy demand, low operation cost, consistent production yield, and, of course, ecological optimization with respect to effluents and air pollution control. To comply with these requirements, the continuous S03/gas sulfonation and double-step neutralization are the basic principles applied in multitube falling film reactor and Neutrex neutralization (Fig. 5). 

Even though all three reactors share the same precursor delivery system, each tool offers specific advantages. For example, a cold-wall reactor (reactor B) helps prevent decomposition of the precursor before it reaches the substrate. A pulsed aerosol injection system at low pressure (reactor C) allows the film to grow under better-defined conditions than in a continuous process (reactor A) because of the minimization of undesirable transient effects caused by the high volatility of the solvents used.46 A more detailed description of each of the conditions for film growth, including reactor type, precursor type, delivery method, deposition temperature, growth time, and other parameters are summarized in Table 6.2. Depositions were done on bare and Mo-coated... 

Fig. 5.15b shows a thin-film continuous flow reactor used by Bruno et al. (1991) for determining the dissolution rate of U02 under reducing conditions. A known weight of U02(s) was enclosed into the reactor between two membrane filters (0.22 jum). The reducing conditions of the feed solution were obtained by bubbling H2(g) in the presence of a palladium catalyst. The dissolution rates determined using continu-... 

V-(6-Methyl-2-pyridyl)aminomethylenemalonate (1001, R = Me, R1 = H) was cyclized to 1,8-naphthyridine (1003, R = Me, R1 = H) in 70% yield in a continuous-operation wiped-film reactor with control of the residence time, whereas in a conventional wiped-film reactor, the yield was 25-30% (79MI2). On heating in dodecylbenzene or in diethyl phthalate at 285-300°C for 3-6 min, the yield was 90% (73MIP3). 

The concentration profile for a reactant A which must migrate from a drop or bubble into the continuous phase to react might be as shown in Figure 12-10. There is a concentration drop around the spherical drop or bubble because it is migrating outward, but, as with a planar gas-liquid interface in the falling film reactor, there should be a discontinuity in at the interface due to the solubility of species A and a consequent equilibrium distribution between phases. 

Figure 17.17. Examples of reactors for specific liquid-gas processes, (a) Trickle reactor for synthesis of butinediol 1.5 m dia by 18 m high, (b) Nitrogen oxide absorption in packed columns, (c) Continuous hydrogenation of fats, (d) Stirred tank reactor for batch hydrogenation of fats, (e) Nitrogen oxide absorption in a plate column, (f) A thin film reactor for making dodecylbenzene sulfonate with S03. (g) Stirred tank reactor for the hydrogenation of caprolactam, (h) Tubular reactor for making adiponitrile from adipic acid in the presence of phosphoric acid.

Both batch reactors and continuous-flow reactors have been used. Because Ti02 photocatalysis is generally considered of interest in purifying air or water with low concentrations of pollutants, the absorption of the incident photons by the pollutants is most often insignificant. If it is not the case, a falling film annular reactor (49) can be used as in photochemistry. 

Rate Oscillations During Propylene Oxide Oxidation on Silver Films in a Continuous Stirred Reactor... 

Meade (26), who made use of an alkali metal alkoxide as a catalyst at 100°C at atmospheric and shghtly above atmospheric pressure. Further refinement was made by Tesoro (27), who conducted the reaction at 55-75°C and a vacuum of 4—8 kPa. Schurman (28) patented a continuous process for making alkanolamide, which makes use of a thin film reactor. It is claimed the short contact time in the reactor produces a high-purity alkanolamide (29). 

Figure 13.12. Continuous flow-type reactors to measure dissolution rates, (a) Experimental scheme of the thin-film continuous flow reactor used for example by Bruno et al. (1991) to determine dissolution rate of UO2 under reducing conditions, (b) Schematic diagram of the fluidized-bed reactor by Chou and Wollast (1984), and developed further by Mast and Drever (1987).

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