Reactors liquid phase processes

Barona, N. and H. V. Prengle, Design Reactors This Way for Liquid-Phase Processes, Hydrocarbon Processing, V. 52, No. 3, 1973, p. 63. 

Alkylation of benzene with linear monoolefms is industrially preferred. The Detal process (Figure 10-9) combines the dehydrogenation of n-paraffins and the alkylation of benzene. Monoolefms from the dehydrogenation section are introduced to a fixed-bed alkylation reactor over a heterogeneous solid catalyst. Older processes use HF catalysts in a liquid phase process at a temperature range of 40-70°C. The general alkylation reaction of benzene using alpha olefins could be represented as ... 

Current state-of-the-art technology for the production of MIBK involves one-step liquid phase processes in trickle bed reactors at 100-160°C and 1 to 10 MPa utilizing various multifunctional catalysts including Pd, Pt, Ni or Cu supported on, metal oxides, cation exchange resins, modified ZSM5 and other zeolites with lull energy integration (2,3,4). However, the MIBK... 

EBMax A continuous, liquid-phase process for making ethylbenzene from ethylene and benzene, using a zeolite catalyst. Developed by Raytheon Engineers and Constructors and Mobil Oil Corporation and first installed at Chiba Styrene Monomer in Japan in 1995. Generally similar to the Mobil/Badger process, but the improved catalyst permits the reactor size to be reduced by two thirds. 

The flow diagram for the vapor phase looks about the same as Figure 8—3. But unlike the liquid phase process, in the reactor both alkylation and transalkylation take place simultaneously so there is no need for a separate reactor to convert PEB to EB. Virtually no PEB shows up as by-product. 

Results of these investigations demonstrate that changes of the reactor surface can be an effective method for directing chemical reactions. Thus, developing a theory of how heterogeneous factors influence liquid-phase chain reactions is one of the important lines of advancement in this area. Only a few years ago it was thought, almost a priori, that there are practically no heterogeneous factors in liquid-phase oxidation and that liquid-phase processes differ from vapor-phase processes in this respect. 

It has always been considered that the condition of the reactor wall is less important for liquid-phase processes than for gas-phase reactions. Now there are numerous examples of marked wall effects which induce essentially new chemical results in liquid-phase oxidations. Hence, the parts played by reactor walls, by solid surfaces, and by other solid catalysts in liquid-phase oxidations should be considered as one of the most important remaining problems. 

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. 

Ethyl Chloride. Hydrochlorination of ethylene with HC1 is carried out in either the vapor or the liquid phase, in the presence of a catalyst.182-184 Ethyl chloride or 1,2-dichloroethane containing less than 1% A1C13 is the reaction medium in the liquid-phase process operating under mild conditions (30-90°C, 3-5 atm). In new plants supported AlClj or ZnCl2 is used in the vapor phase. Equimolar amounts of the dry reagents are reacted in a fluidized- or fixed-bed reactor at elevated temperature and pressure (250-400°C, 5-15 atm). Both processes provide ethyl chloride with high (98-99%) selectivity. 

This was a liquid-phase process which used what was described as siliceous zeolitic catalysts. Hydrogen was not required in the process. Reactor pressure was 4.5 MPa and WHSV of 0.68 kg oil/h kg catalyst. The initial reactor temperature was 127°C and was raised as the catalyst deactivated to maintain toluene conversion. The catalyst was regenerated after the temperature reached about 315°C. Regeneration consisted of conventional controlled burning of the coke deposit. The catalyst life was reported to be at least 1.5 yr. 

The hydrogenation of nitrobenzenes to anilines is carried out in a liquid phase or in a vapor phase, in either a fixed-bed or a fluidized-bed reactor. For vapor-phase processes, copper-based catalysts97 and sulfided nickel98 are among those most frequently used. For liquid-phase processes, supported nickel99 and Raney Ni100 as well as supported palladium101 are the catalysts most commonly employed. 

In the EBMax process, benzene is fed to the bottom of the liquid-filled multibed reactor. Ethylene is co-fed with the benzene and also between the catalyst beds. Polyethylbenzenes, which are almost exclusively diethylbenzenes, undergo transalkylation with benzene in a second reactor. Mobil-Badger offers both liquid phase and vapor phase transalkylation processes. The vapor phase process removes benzene feed coboilers such as cyclohexane and methylcyclopentane as well as propyl and butylbenzenes. Because the EBMax process produces very low levels of propyl and butylbenzenes, for most applications, the more energy efficient liquid phase process is preferred. Worldwide, there are currently ten licensed EBMax units with a cumulative ethylbenzene production capacity of five million metric tons per year. 

The methanol hydrocarbonylaiion is usually carried out in the liquid phase using discontinuous batch reactors and continuous liquid phase processes have also been examined. It was claimed that in these processes, side-product formation can be suppressed and ethanol yields can be improved [23, 50]. Continuous... 

This principle may also be illustrated by some real cases. In the codimerization of propene and hexene it is important primarily to minimize the dimerization of the reactive propene. In order to favor the codimerization, a stage injection of propene according to the principle in Fig. 1 was therefore performed [2]. A similar process design with distributed additions of chlorine was applied in the chlorination of propene to allyl chloride in order to suppress different side reactions [3]. For liquid-phase processes, a distributed feed to the cascade of stirred reactors was a more natural variant. This was applied in the sulfuric acid alkylation of / obutane, where the olefin feed has to be subdivided due to selectivity reasons and the goal was to reach a desired octane number of the product [4]. 

A second process using complex as the catalyst was independently developed by the Standard Oil Company (Indiana) and by the Texas Company (25,26). A simplified flow diagram of this liquid-phase process is shown in Figure 17. A portion of the dried and heated feed passes through a saturator where aluminum chloride is picked up in accordance with the solubility curve shown in Figure 8. The total feed combined with re( y< le hydrogen chloride enters the bottom of the reactor and... 

Catalytic reactions can take place in either the liquid or vapor phase. Liquid phase reactions can be run in either a continuous manner or as a batch process while vapor phase reactions are run only in a continuous mode. In a batch reaction the catalyst, reactants, and other components of the reaction mixture are placed in an appropriate reaction vessel, the reaction is run and the products removed from the vessel and separated from the catalyst. In a continuous system the reactants are passed through the catalyst and the products removed at the same rate as the reactants are added. The applicability of vapor phase processes is limited by the volatility and thermal stability of the reactants and products so such processes are not commonly involved in the preparation of even moderately complex molecules. Because of this, primary attention will be placed here on liquid phase processes with vapor phase systems of secondary importance. A discussion of the different types of reactors used for each of these processes is found in the following chapter. The present discussion is concerned with the effect that the different reaction parameters can have on the outcome of a catalytic reaction. 

The above discussion indicates the importance of the size of the catalyst particles-a very small size is required if a technically useful rate of production is to be achieved. The range of sizes of the catalyst particles that can be employed is, however, dominated by the reactor in which the catalyst must operate. Most of the reactions performed in the fine-chemical industry involve liquid-phase processes, normally reactions between two different dissolved compounds. Often one of the reactants is a gaseous compound, which dissolves in the liquid and migrates to the surface... 

Table 8.2 presents comparatively the four reactor types proposed above. Liquid-phase alkylation was practiced in the past, but is nowadays completely obsolete, mainly because of pollution problems. Vapour-phase alkylation (UOP Alkar process) was popular up to 1970, when Mobil/Badger process based on ZMS-5 synthetic zeolite catalyst was launched. This process dominates the market nowadays, but is in competition with the liquid-phase process based equally on zeolite catalyst proposed by UOP/Lummus. The two processes have similar performances. The selection depends greatly on the catalyst behaviour, price and regeneration cost. We would prefer the last, for the following reasons ... 

A prime advantage of the liquid-phase process is its substantially lower cost compared to vapor-phase processes investment is particularly low because a single, inexpensive main reactor chamber is used as compared to multiple-bed or tubular reactors used in vapor-phase processes. Quench gas and unreacted benzene recycles are not necessary, and better heat recovery generates both cyclohexane vapor for the finishing step and a greater amount of steam. These advantages result in lower investment and operating costs. 

The predominant process for manufacture of aniline is the catalytic reduction of nitrobenzene [98-95-3] with hydrogen. The reduction is carried out in the vapor phase (50—55) or liquid phase (56—60). A fixed-bed reactor is commonly used for the vapor-phase process and the reactor is operated under pressure. A number of catalysts have been cited and indude copper, copper on silica, copper oxide, sulfides of nickel, molybdenum, tungsten, and palladium—vanadium on alumina or lithium-aluminum spinds. Catalysts cited for the liquid-phase processes include nickel, copper or cobalt supported on a suitable inert carrier, and palladium or platinum or their mixtures supported on carbon. 

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