Liquid oxidation reactor

FIGURE 3.3 Praxair liquid oxidation reactor. (Reproduced from Roby and Kingsley (1996) with permission from Praxair Technology Inc.)... 

Duveen (1998) has suggested the use of a venturi loop reactor for oxidations with pure oxygen in a manner exactly analogous to the Praxair Uquid oxidation reactor. The operation in a dead-end mode has been claimed to produce practically no vent gas. It must be noted here that burning of acetic acid and the consequent products cannot be avoided. CO and other products formed must be purged. To this extent, the operation is likely to be similar to the Praxair liquid oxidation reactor. 

In view of (2), the gas-inducing impeller has to be necessarily located closer to the top liquid level (Section 3.4.2.4.3 and Figure 3.3 Praxair liquid oxidation reactor). For three-phase reactions involving a solid catalyst, a multi-impeller system is required. This is because a single impeller used to induce the gas is not capable of suspending the solid settled at the bottom. Further, because of the poor gas dispersion by the top gas-inducing impeller, the second lower impeller has to also perform this duty of gas dispersion in the lower part of the reactor. 

Product removal during reaction. Sometimes the equilibrium conversion can be increased by removing the product (or one of the products) continuously from the reactor as the reaction progresses, e.g., by allowing it to vaporize from a liquid-phase reactor. Another way is to carry out the reaction in stages with intermediate separation of the products. As an example of intermediate separation, consider the production of sulfuric acid as illustrated in Fig. 2.4. Sulfur dioxide is oxidized to sulfur trioxide ... 

Herm/es/Djnamit JS obe/Process. On a worldwide basis, the Hercules Inc./Dynamit Nobel AG process is the dorninant technology for the production of dimethyl terephthalate the chemistry was patented in the 1950s (67—69). Modifications in commercial practice have occurred over the years, with several variations being practiced commercially (70—72). The reaction to dimethyl terephthalate involves four steps, which alternate between liquid-phase oxidation and liquid-phase esterification. Two reactors are used. Eirst, -xylene is oxidized with air to -toluic acid in the oxidation reactor, and the contents are then sent to the second reactor for esterification with methanol to methyl -toluate. The toluate is isolated by distillation and returned to the first reactor where it is further oxidized to monomethyl terephthalate, which is then esterified in the second reactor to dimethyl terephthalate. 

Ethylbenzene Hydroperoxide Process. Figure 4 shows the process flow sheet for production of propylene oxide and styrene via the use of ethylbenzene hydroperoxide (EBHP). Liquid-phase oxidation of ethylbenzene with air or oxygen occurs at 206—275 kPa (30—40 psia) and 140—150°C, and 2—2.5 h are required for a 10—15% conversion to the hydroperoxide. Recycle of an inert gas, such as nitrogen, is used to control reactor temperature. Impurities ia the ethylbenzene, such as water, are controlled to minimize decomposition of the hydroperoxide product and are sometimes added to enhance product formation. Selectivity to by-products include 8—10% acetophenone, 5—7% 1-phenylethanol, and <1% organic acids. EBHP is concentrated to 30—35% by distillation. The overhead ethylbenzene is recycled back to the oxidation reactor (170—172). 

The homogeneously catalyzed oxidation of butyraldehyde to butyric acid is a well-characterized gas/Hquid reaction for which kinetic data are available. It thus serves as a model reaction to evaluate mass transfer and reactor performance in general for new gas/liquid micro reactors to be tested. This reaction was particularly used to validate a reactor model for a micro reactor [9, 10]. 

Smith and Raptis53 have suggested using the deep-well environment as a wet-oxidation reactor for liquid organic wastes. This process, however, does not involve deep-well injection of wastes but rather uses temperatures and pressures in the subsurface to increase the oxidation rate of organic wastes, which are then returned to the surface. 

Figure 14.17 Schematic diagram of the ThermoElectron liquid chromatography isotope ratio mass spectrometry chemical oxidation reactor...

LOR [Liquid-phase oxidation reactor] Not a process but a piece of equipment in which to conduct liquid-phase oxidations (e.g. the Mid-Century process) safely with oxygen rather than with air. The oxygen is introduced into the liquid phase and rapidly dispersed in the form of bubbles 1 to 5 mm. in diameter. Developed by Praxair and ABB Lummus Global in 1996. 

Processes involving oxygen and nitrogen oxides as catalysts have been operated commercially using either vapor- or liquid-phase reactors. The vapor-phase reactors require particularly close control because of the wide explosive limit of dimethyl sulfide in oxygen (1—83.5 vol %) plants in operation use liquid-phase reactions. Figure 2 is a schematic diagram for the liquid-phase process. The product stream from the reactor is neutralized with aqueous caustic and is vacuum-evaporated, and the DMSO is dried in a distillation column to obtain the product. 

In the laboratory batch ozonation is easy to apply, whereas multi-stage continuous-flow systems are difficult to handle (Method 1). However, mainly due to large liquid flow rates the inverse situation is valid for many full-scale applications. Often three oxidation reactors in series are found in waste water ozonation (cf. Table A 3-3). The advantage of a multi-stage CFSTR system - or even a batch system - lies in their faster reaction rates compared to a single CSTR due to the reduced axial/longitudinal mixing. 

Paraxylene and air comprise the chargestock. These materials, along with a proprietary catalyst and solvent, are fed to a liquid-phase oxidation reactor, operated at moderate pressure and temperature. The reaction is ... 

Although benzoic acid occurs naturally in some substances, such as gum benzoin, dragon s blood resin, balsams, cranberries, and the urine of the ox and horse, the product is made on a large scale by synthesis from other materials. Benzoic acid can be manufactured by the liquid-phase oxidation of toluene by air in a continuous oxidation reactor operated at moderate pressure and temperature ... 

Figure 4-14. A two-phase tubular flow reactor (e.g., gas-liquid bubble reactor for oxidation of pollutants in water). (Source J. M. Smith, Chemical Engineering Kinetics, 3rd ed., McGraw-Hill, Inc. 1981.)...

Reactions involving gas, liquid, and solid are often encountered in the chemical process industry. The most common occurrence of this type of reaction is in hydroprocessing operations, in which a variety of reactions between hydrogen, an oil phase, and a catalyst have been examined. Other common three-phase catalytic reactions are oxidation and hydration reactions. Some three-phase reactions, such as coal liquefaction, involve a solid reactant. These and numerous other similar gas-liquid solid reactions, as well as a large number of gas-liquid reactions, are carried out in a vessel or a reactor which contains all three phases simultaneously. The subject of this monograph is the design of such gas-liquid -solid reactors. 

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